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[Question]
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What would happen if the following happened in a hospital.
(Assume that this is the real world, where magic shouldn't exist.)
1. A patient in the ER, who was admitted for poisoning, turned into an animal (and back again) right in front of people (and presumably on CCTV). How might doctors proceed with this complication?
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1) As usual when dealing with unknown poison / designer drug. Observe vital signs, treat blatantly wrong things like too high / too low pressure. Hope that the patient would survive.
2) Ask your superior what to do with with this complicated case, as specified in procedures. (nice way of passing a problem)
3) Apply a wide range of possible tests. (partially hoping to get any useful info, partially just to avoid doing nothing)
4) No one would like to make a phone call for any police... As such call would be ignored as a prank or a call made by a psychotic patient.
5) While waiting for lab tests to be produced deal with next, more urgent patients. (it tend to be busy in emergency rooms)
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The shape shifting wrapper can encompass a number of different apparently magical wonders and a hospital full of scientists (and other worshippers of cause & effect) might have drastically different responses, depending on which wonders are immediately apparent.
If the patient transforms into a creature of drastically different mass and if the transformation does not make up for that mass by either absorbing or excreting appropriate quantities of matter; then a fundamental law of physics is being broken. You can expect the scientists to get a little emotional once you've violate conservation of mass and energy.
Similarly, if all of the patients clothing and possessions vanish while they are in animal form and reappear during their journey back to being bipedal; then a lesser known fundamental law joins CoM&E on the butcher block. Because that is the destruction and reconstruction of information and a slap in the face of entropy. Expect more pissed-off PHDs after that performance.
But if your shifter is well behaved and at least appears to be obeying the laws of nature, if he carefully disrobes before his bones and muscles begin changing into a comparably sized creature; then you can expect the surrounding professional care givers to show patience, curiosity and kindness as they support, comfort and study this afflicted soul.
They will probably even give him a strong comforting sedative before the dissection begins.
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Your average ER would freak out. I mean seriously freak out. Granted, if the shapeshifter turned into a bunny, the freaking wouldn't be so great as if it were a more aggresive creature, but there would be freaking. And I doubt it would be as cultured as [Fonzie meeting Mork](https://youtu.be/46cG2foNwiU?t=45s) freaking.
And when they were done freaking, there would be police... lots and lots of police. Who would then freak.
At this point you have a 50/50 chance. They might tase the shapeshifter, or they might shoot it. Shooting it isn't very fun, let's tase it.
Once the shapeshifter is subdued, it would be caged. Having determined the minimum bar spacing from the animal (a rabbit would need, what, 2" spacing?) an appropriate cage would be constructed. At which point the local university would be called to investigate the creature.
They'd freak.
But not before the yet-to-be-announced-by-Snowden big brother of Cyberhawk is used by the NSA to intercept the call, identify the phrase, "it's a freaking monster!" and react by dispatching NSA agents, who are inevitably dressed in black and drive unmarked and unlicensed SUVs.
They don't freak.
They very politely take posession of said shapeshifter, neuralyze everyone so they don't remember what happened, leave them with a passible subliminal message about what caused the mess *(light reflecting off of venus cast a bunny-shaped shadow on the wall, causing that nurse over there to freak. Maybe she needs counselling for her leporiphobia.),* and leave.
After which your shapeshifter begins to freak.
About two years after that Guillermo del Toro would create a movie loosely based on the incident with remarkably slender oriental women playing nurses and equally remarkably buff Australian men playing the NSA agents with a 3-tone musical score you can't keep out of your head and make bazillions of dollars — not one penny of which will go to your shapeshifting rabbit.
*This probably wasn't the answer you were looking for... but I couldn't help myself.*
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Well if he just turned into an animal in front of everyone, then(assuming the doctors want to help him) the doctors will probably board up the doors(for the hoards curious about the animal shape shifting) and clear out all the patients on the same floor in 100 ft radius(to prepare for the worst, a [blue whale](https://en.wikipedia.org/wiki/Blue_whale) transformation) and curing the poison should be easy or hard with a shape depending on whether or not he can control the animals he is uncontrollably turning into. If he keeps turning into animals smaller than a human then the doctors will have a bad time treating him, fist off the amount of treatment will change with size(if he become a [fairyfly](https://en.wikipedia.org/wiki/Fairyfly) well good luck) , what to use will change with what he is(different biochemistry), and the tools based on what he is as well. So I'm saying a quick trip to the local vet to pick up what is needed and a vet(being a vet is actually so hard that many drop out to become doctors). If Sea World is at a reasonable distance then maybe pick up someone from their or a Zoo for the more exotic transformations. And if he turns into animals that are larger than a human, well congrats, your cured! the poison will be processed better by bigger animals, and super well if you become a Blue Whale, just don't stay too long or you will look like [this](http://khq.images.worldnow.com/images/incoming/bluewhale.jpg)
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It's going to depend on how the doctor reacts to the fact that his entire world view has just been broken by having the existence of magic/the-really-freaking-strange-unknown, shoved down his throat. But fair bet, the CDC gets called and the hospital gets evacuated and the doctor doesn't actually treat the patient.
[Answer]
Recall that one lecture on One Health from medical school. Failing that call a veterinarian. ;)
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## BACKGROUND
The world I'm designing currently has a gas giant of the type known as a hot Jupiter orbiting close to the sun and [causing solar flares.](https://worldbuilding.stackexchange.com/a/103484/37212) I would like the inhabitants of my Earth-like world to regularly witness this planet transiting their sun, making it a center of religious life, and perhaps incorporating it into their calendar. If I can justify it being a time of increased flare activity then so much the better.
In the real world, Mercury and Venus infrequently transit the sun. However, a hot Jupiter has a large puffy atmosphere, floats very close to its star (0.015-0.15 AU), and has an orbital period of less than ten days. All this means that they [transit a good deal more frequently](https://en.wikipedia.org/wiki/Superflare#Hot_Jupiters_as_an_explanation). Apparently that's one of the reasons why we've discovered so many of them using the transit method.
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## DETAILS
Assuming the premise that an Earth-like planet in a system with a hot Jupiter might see regular solar transits is valid, I need to get an idea of how often transits will occur, and what they'll look like. This may be a little complicated because hot Jupiters tend to have [weird orbits](https://www.space.com/27122-hot-jupiters-crazy-orbits-mystery.html).
If possible, I'd also like to justify the transit being ...
* **Regular.** To make the transits as reliably timed as plausible, so it can be more predictable to my inhabited planet and less of a headache for me.
* **Common.** To make the transits fairly common. Once a year might be ideal for example. But as a side note, I'd also be very curious if a particular orbit might make these transits slowly become more common over time.
* **Centered.** To keep the path of transits as close to centered across the sun as I can.
But regardless of whether that's plausible, **what I basically need are conceptual tools that a dedicated but uneducated guy can use to approximate when a hot Jupiter will transit its star in a way that's visible to an Earth-like world, as well as a working knowledge of the most likely parameters of such transits.**
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## **QUESTION**
**How can I plot the solar transits of a hot Jupiter as seen by an earth-like world?** How close can I plausibly get to making this a regular and predictable event? Anything else I should know?
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*As a final note, getting this particular question right is rather important to me, so I'll offer a thank-you bounty to an answer I think is particularly helpful and complete. I've tried to be conscientious about my Wikipedia research, but I know little about astronomy, and always appreciate it if folks are willing to explain things to me. Thanks for any help.*
***BOUNTY EDIT:*** Thanks everyone. Bounty goes to HDE ... etc. etc. :)
[Answer]
# Why are transits so rare?
Essentially, you want a low relative [**orbital inclination**](https://en.wikipedia.org/wiki/Orbital_inclination).
A body's orbital inclination is the angular difference between its orbital plane and a reference plane. In the Solar System, this reference plane is the the [ecliptic](https://en.wikipedia.org/wiki/Ecliptic), such that Earth's orbit is contained in this plane (and thus it has an inclination of zero). Most of the planets have low inclinations, but Mercury and Venus - the only two planets an Earth-bound observer can see transit the Sun - have the highest inclinations, of 7.01 and 3.39 degrees, respectively.
This, combined with the fact that orbits aren't perfect circles, is why transits are so rare. Even when Mercury or Venus moves between Earth and the Sun, in what's called a [conjunction](https://en.wikipedia.org/wiki/Conjunction_(astronomy)), the planet often appears above or below the Sun - meaning no transit. If you lower the inclination of the hot Jupiter, you should be able to avoid this problem, making transits more common.
[](https://i.stack.imgur.com/6e4kY.png)
Three types of conjunctions for an inclined orbit. The top and bottom ones miss the star entirely; only the middle one crosses. I've drawn the hot Jupiter too small, though.
# How common are transits?
Let's assume you go with this scenario. Assume your planet's semi-major axis is 1 AU, and the hot Jupiter's semi-major axis is 0.015 AU - small, even for a hot Jupiter, but certainly not improbable. We can use [Kepler's third law](https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Third_law_of_Kepler) to find that, if the star is about the mass of the Sun, they'll have periods of 1 year and 16 hours, respectively.
We need this because we want to calculate something called the [**synodic period**](https://en.wikipedia.org/wiki/Orbital_period#Synodic_period), which is essentially how long it takes for the other body to appear in the same spot, i.e. the length of time between successive conjunctions. The formula is
$$\frac{1}{P\_{\text{syn}}}=\frac{1}{P\_1}-\frac{1}{P\_2}$$
where the inner planet has period $P\_1$ and the outer planet has period $P\_2$.1 We then find that the synodic period for this system is about 16 hours and 2 minutes - meaning that transits happen pretty often!
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1 In the case where $P\_2\gg P\_1$, we also see that $P\_{\text{syn}}\approx P\_1$.
[Answer]
Given a hot Jupiter in a highly-inclined 10-day orbit, and an Earthlike planet in an equatorial one-year orbit, you'll get a transit every time the two planets cross one of the hot Jupiter's [orbital nodes](https://en.wikipedia.org/wiki/Orbital_node) at the same time. This is the same phenomenon that causes solar eclipses and transits of Mercury and Venus here on Earth, and as you can imagine, isn't naturally a very common event.
The solution to this is an orbital resonance: the Earth-like planet needs to be in a roughly 1:36 resonance with the hot Jupiter. If everything is lined up properly, this will give you two central transits a year, exactly half a year apart. If they *aren't* lined up properly, you'll get zero transits, ever.
A resonance with such a high difference in orbital periods is rather fragile. In order to keep it from being disrupted, your stellar system should be free of other large bodies. Asteroids are fine, Earth-sized planets in the outer system are fine, but Venus and Saturn aren't.
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I'm in a D&D campaign where astronomy plays a big deal. I want to name drop and reference some good astrology myths about evil or cursed stars, but I'm having an awful time finding anything. The only one I have for a reference to start searching is Algol, the demon star, which I found from an old Lovecraft story (but which has been in mythology for longer than that, of course), but that reference doesn't seem to lead me anywhere else and more generic searches yield nothing.
So my question is what are some evil stars and where can I find out more about them? I don't care what tradition or culture they come from. Honestly a mix would probably be ideal.
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In actual astrology, an 'unfortunate star' would be more like an unfortunate alignment of the planets. If you were born under the protection of Jupiter as a Scorpio, then when Jupiter is in the house of an opposing sign, like Taurus, it is an inauspicious time to start any endeavor that requires good fortune.
In general, this is how it would work. There would not be stars that are permanently evil, but certain alignments that are unfortunate, and can lead you to evil ends.
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I can't think of any evil stars I would've heard of, but how about a comet? Historically, they've been regarded as omens and harbingers of doom, as well as associated with stuff like famines and deaths of important and/or powerful people.
<https://en.wikipedia.org/wiki/Comet#In_popular_culture>
<http://tvtropes.org/pmwiki/pmwiki.php/Main/CometOfDoom>
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Might I suggest the [Wormwood Star](https://en.wikipedia.org/wiki/Wormwood_(Bible)) of biblical myth? It's only mentioned in a single verse, but it is a star which falls to earth and poisons the rivers, killing many people. Definitely evil.
This isn't explicitly an astrology myth, but still seems to be more or less what you're looking for.
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To my knowledge, there are no real stars that are "bad" stars. There are useful stars (used to navigate) and all the other ones.
Before the advent of telescopes, any of those tiny lights in the sky would have been seen as "stars" so it may not matter if it's a planet or comet or a star so much. We draw a distinction between those things that this fantasy society may not have. What I'm getting at is your search for "evil" stars may be limited by what we think of as stars.
As example, Mars. Even in ancient times, with the naked eye you could tell it was odd. It was red and it moved a lot more than most of the other little lights in the sky. It would show up in the night sky for a span of nights and vanish again, not to be seen for many more nights. When compared to other stars, it was magical in a way. But, at the same time, it is there enough that no long standing correlation can be made with evil events.
To be called a herald or a portent or ill it has to be very strange and not much seen and then have some bad stuff just happen the last time it (or something like it) showed up. So the more common foreboding things are comets and eclipses (both solar and lunar). But there is something else that you may like.
On August 6 in [1181](https://en.wikipedia.org/wiki/SN_1181) CE a whole bunch of people saw a light in the night sky bigger and brighter than any other star. Many of them feared it and said it was a bad omen. It wasn't a star, it was a supernova. It was there for six months. Yeah, people freaked out. After all, it could only be the end of the world. All that and they didn't know about the one in [1054](https://en.wikipedia.org/wiki/SN_1054) CE that remained in the sky for two years! We know of another half dozen supernovas seen in ancient times. Generally speaking, some people freaked out each time.
Again, we draw a distinction that the denizens of your D&D world may not. We know those were supernova. To them it's a thing that no one alive (at least no human) has seen before, hence it can't be good. Expand your definition of star to include these supernova and you can have something to reference. Otherwise, I don't think you will have much luck.
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If I were to have a generally earth like world, with water and land masses very similar, what could you add to make storms happen more often, and more specifically, lighting storms. I know lightning happens because of friction in the clouds between dust particles, but could increase the amount of lightning strikes on a planet?
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There are some places on Earth that have an unusually high frequency of lightnings. For instance, [Venezuela](https://en.wikipedia.org/wiki/Catatumbo_lightning). The explanation, in this case, consists in moisty air locked by mountain ridges, and then sent onto a cycle of heating and cooling, where charges are likely accumulated at the two ends of the cycle in a phenomenon that is reminiscent of a [Van Der Graaf generator](https://en.wikipedia.org/wiki/Van_de_Graaff_generator).
My suggestion would be to make a large number of smaller, nearly land-locked, seas on your new world, with high coastal mountains, and nearly dust free to reduce the albedo. Also, increase the tilt, so that a larger portion of the surface may get maximum solar heat at some point during the year.
Next, cover the coastal mountains with some moisty jungles to make the air above richer in water, and increase the salt in the sea, to create a drier column of air over the sea. The difference in moisture should create a barrier for the electrostatic charges to complete a full-cycle, hence accumulating a difference of potential across the difference in altitude.
The surface of this poor planet will probably look greener than Earth, and like as if the planet were a (greenish) Swiss cheese, or, perhaps, affected by a bad form of acne.
[Answer]
**Solar storms.**
["Streams of particles launched from the sun in the solar wind increase the number of lightning strikes on Earth by 32%."](https://www.theguardian.com/science/2014/may/15/sun-lightning-strikes-earth-solar-wind) From the article:
*"Activity on the sun significantly increases the rate of lightning strikes on Earth, say researchers, making it feasible to predict when lightning strikes will become more frequent.
They discovered that when streams of high-speed solar particles strike the Earth's atmosphere, the average number of lightning strikes increased by 32% for more than a month afterwards. The study is the first to implicate the solar wind – the stream of particles launched from the sun at over a million miles per hour – in triggering lightning, a phenomenon that has puzzled scientists."*
The original paper is here: <http://iopscience.iop.org/article/10.1088/1748-9326/9/5/055004>
In summary: it was previously assumed that galactic cosmic rays (GCR) was a source of lightning, and the solar wind helped shield the Earth from their effects, however the study which included 16 years of data shows the opposite effect. For 4 to 5 days after a solar event the amount of lightning drops, but that is followed by a period between 8 and 40 days after the solar event where lightning activity *increases*.
The researchers suggest some mechanisms involving the solar wind alone, and the solar wind interacting with GCR, but they admit they do not know the actual reason.
[Answer]
Put more energy in the atmosphere: storms are more frequent in summer because there is more solar energy available, and that solar energy is able to lift icy particles and droplets higher in the atmosphere.
This motion helps building up charges in the clouds, which then result into lightning.
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(Please see diagrams)
This is a question regarding an area of a Rocheworld scenario that I haven't found anything on.
It is suggested that the OUT side of a planet that is tidally locked with another is actually exposed to the vacuum of space because the gravity has pulled the atmosphere away from that area and towards the IN side which is facing the other planet with which its locked. But that must create a narrow area (a band around the planet?) which is neither fully covered in atmosphere nor fully exposed to vacuum.
On Earth the atmosphere thins out the *higher* we go. But on either of the Rocheworld planets the atmosphere would thin out right on the land the further you moved away from the twin planet. Potentially one could "walk" through a thinning atmosphere and right into the vacuum of space. That side of the planet, I imagine, would be like the surface of the moon (but with that planets gravity[?]).
But what would we experience in that band *between* the full atmosphere area and the vacuum exposed area?
See the diagram I drew below. (*Hopefully all the other science is correct enough to understand the question.*)
[](https://i.stack.imgur.com/BvS19.jpg)
Edit: Its been suggested that a Rocheworld is impossible. Its also been suggested that it is possible. Lets hand wave that for the sake of the question. Thanks.
**SECOND EDIT with diagram:**
Some of the responses suggest that my notions of the atmospheric conditions are off. I was wondering if you think this is more "correct"? If so, it removes the idea that the OUT side of the planets would be exposed to the vacuum of space. Hopefully this 2nd diagram is self explanatory.
[](https://i.stack.imgur.com/dV7Ml.jpg)
Although this does raise another concern... What is the shape of the shared atmosphere area, and does it leak out so badly that nothing could really cross between the two planets?
Again, Thanks.
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**3rd edit:**
@neophlegm gives a great answer below that this third diagram illuminates. He has a great diagram of his own as well.
[](https://i.stack.imgur.com/x9h0E.jpg)
whew
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I'd like to respectfully offer an alternative to the above answers; while I agree this arrangement of atmospheres isn't possible even in this rocheworld setup, I believe the outcome would be different. Consider the effect the moon has on the tides on Earth:[](https://i.stack.imgur.com/fiCGA.gif)
In a rocheworld system as denoted above you would see a similar effect on the planet's atmospheres (indeed: the moon does exert effects on Earth's atmosphere, just far less notably). The outer edges of both planets retain atmosphere because of the inertial (or if you prefer, centripetal) "force" resulting from the system rotating. The inner surfaces of each planet retain atmosphere due to their mutual gravitational attractions. Also of note, the surface deformation would mirror this and you'd see a bulge pointing inwards *and outwards* on each body.
In the limit that these atmospheres touch in the centre the atmospheres would indeed have a central point where the net gravitational effect is zero: this is called a Lagrangian point (specifically it's the [L1 point of a two-body massive system](https://en.wikipedia.org/wiki/Lagrangian_point)). However, this particular point is unstable: that is, if you perturb any atmosphere at the point it will move very slightly closer to one or other planet. This will increase the gravitational force on the molecules (since gravity gets stronger as you get closer to a mass), resulting in the atmosphere remaining bound to one or other body. The atmospheres could be exchanged in this way, but they wouldn't vent into space.
However, if the planets are sufficiently close and rotating sufficiently fast, there's the possibility that the atmosphere would coalesce at the inner *and* outer surfaces, and a band of near vacuum would form around the line circumnavigating the planet from pole-to-pole, in which transitional regions you would see effects as described in the answer from Josh above. You could even envisage two separate completely isolated ecosystems with their own plant/animal life evolving on the separate sides of one planet and never interacting until they develop the means to cross this airless barrier.
Disclaimer: I'm new on here so I hope this doesn't come across as impertinent. My sources are some judicious googling and a masters degree in Physics with a good number of astronomy modules.
[Answer]
This would be really weird climatologically.
I am assuming it is a similar composition to the [atmosphere of Earth](https://en.wikipedia.org/wiki/Atmosphere_of_Earth).
It should roughly follow a horizontal projection of our atmosphere's vertical distribution.
[](https://i.stack.imgur.com/KvmFx.png)
As you travel the air density and pressure would generally decrease. There would likely be sizable variations in this (Earth's atmosphere pressure changes due to weather systems; this would change similarly due to weather and local topography. A prevailing wind system,jet stream, or Hadley cell equivalent could make the habitable/breathable air boundary very lumpy and non uniform (and potentially changing).
The temperatures would be way different, on Earth the atmosphere get's heat from absorption from the sun directly and re-radiation of heat from the Earth.
Taking our atmosphere sideways you would expect it to initially get colder, but on this world that effect would be dampened by the stored heat in the ground or water (Ocean's would be crazy on these planets), so less of an initial temperature decrease. As you progress temperature extremes over night and day would increase similar to Earth's Moon which has temperature swings of hundreds of degrees.
At some point you would hit some weird places where the tropopause is in contact with the surface. Expect a constant fog or cloud layer to form at this level.
Ocean's wouldn't flow to here, if there is sufficient gravity to pull the atmosphere any ocean should be pulled similarly. Surface gravity in general would be strange on these planets with large sideways components, walking horizontally would literally feel like an incline. At some point water would boil due to pressure. You may have some odd icing and glacial buildup of frozen water and other gases (CO2 dry ice, etc.) specifically forming in polar? regions of less solar heating, or in craters or other places not exposed to sunlight. On Earth these ice particles fall and melt, on your worlds they would be at ground level and accumulate where temperatures permitted.
Speaking of craters, the landscape would change as you progressed with less erosion occurring and more un-eroded impact craters visible. Tectonically these planets would likely have any active plate tectonics generally moving towards the center of mass between the planets with large rift valleys on the far atmospheric side and potentially some active volcanism.
Higher you would get higher levels of cosmic radiation, surface level ozone formation or aurora, but these depend a lot on the planets magnetic properties which are a big unknown. I wouldn't expect such a non uniform planet under such large tidal stresses to have a rotating core (and corresponding magnetic field), but I haven't done any calculations to prove it's impossible.
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Such atmosphere is, alas, physically impossible: the pressure is the same everywhere on the surface.
On Rocheworlds, as with any planet, gravity is always perpendicular to the local surface. After all, the planet is in hydrostatic equilibrium, so if the ground wasn't horizontal, it would crumble until it is. The strength of gravity may vary from place to place, but its apparent direction will never change - it is always vertical compared to the surface.
As such, if a high-pressure zone is next to a low-pressure zone, the atmosphere will simply flow from the high pressure to the low pressure, until equalised. The fact that some zones have a different gravity than others won't change that, though it will have important effects on climate.
But what if, at its lowest point, gravity is too weak to retain atmosphere?
Then the entire atmosphere will slowly evaporate. Depending on how old the planet is, it may have no atmosphere left, even if gravity at its strongest point would otherwise enough to retain it.
The atmosphere would probably be of relatively equal thickness. At those scales, the crust itself acts as a fluid, so the forces that shape the solid surface are the same that shape the atmosphere. As such, the atmosphere would follow the surface.
It would be somewhat thicker on the points more distant from the planetary centre, and the zone where the atmospheres meet would be slightly rounded (no bleeding-sharp concave angle), but given the relative thickness of atmosphere compared to the planet itself on an Earth-like rockball, it would not be very perceptible.
Also note that the planets would look more like an egg, with the pointy bit facing the other planet. An example can be found [here](http://panoptesv.com/RPGs/Settings/VergeWorlds/Worlds/Bondle.php). The author is a physicist (a laser specialist, but a physicist nonetheless) and as such, made sure to have a physically correct model.
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I understand that asteroids are very very far apart, but everything I am reading about asteroid mining omits any information about what happens to the waste rock or "tailings" that would presumably be left over. Is it loose rubble or ground powder? Does it not become an operational hazard, at least to the mining unit itself? What I mean is, assuming the process creates dust, wouldn't all the mining equipment be coated in it, potentially clogging servos and covering solar panels, etc?
If there is rubble or gravel left over, would it have any value or use? Potentially being compressed into (I am guessing) a drywall-like building material for space constructs, or used as soil or fertilizer?
[Answer]
Asteroids come in different types:
<https://nssdc.gsfc.nasa.gov/planetary/text/asteroids.txt>
The amount and properties of waste rocks depend on the composition:
Carbonaceous asteroids are mainly made up from carbon. One would only mine them for carbon, so the amount of waste would be negligible.
Silicaceous asteroids contain metal silicates. These are powder-like, so one can expect a lot of dust by mining. The final byproduct of refining them for iron or magnesium would be silica, which could be made into solid, stable blocks.
Metallic asteroids are almost pure metal. The waste will be little in this case again.
The amount of waste would be probably lower than by Earth-bound mining, and part of it could get blasted away at speeds exceeding the (pretty low) escape velocity of the asteroid, but measures might would be necessary to protect the equipment:
A) The accumulation of static charge, which could attract the dust particles needs to be prevented.
B) Joints could be coated into flexible plastic.
C) Mining methods which don't produce dust could be used:
<http://www.planetaryresources.com/asteroids/#harvesting-water>
This proposal does not want to harvest all the minerals, but only aims of water. The spallation happens in a closed chamber with solar heat, so dust is not an issue.
And yes, there are some uses for waste rocks too:
<https://en.wikipedia.org/wiki/Space_elevator>
The heavier the counterweight is, the shorter the elevator needs to be to have center of mass at GEO. So packing a lot of wastes into a giant bag could save us some thousand kilometers of carbon nanotubes. The same holds for other tether systems requiring counterweights on orbit:
<https://en.wikipedia.org/wiki/Universal_Orbital_Support_System>
This funny paper shows that transporting lunar rock to Earth using rotovators produces net energy gain:
<http://www.tethers.com/papers/LEO2Lunar%2792.pdf>
**A similar system could drop mining wastes into planetary gravity wells to drive the tethers which ferry up passengers and useful equipment.**
[Answer]
## Waste
Really depends on what you are mining for, and what you are mining and, how you are mining.
In 0g environment even weak and heavy materials can be used for functional constructions. As an example collecting the energy, meted "rock" coated with metal can be used as mirrors for solar collectors. So there might be no waste at all in the sense. Gravity dictates for construction materials to be strong enough, not the case in 0g.
The technology you are using also important for determining in which form those byproducts might be but as rule of thumb quite the same as here on earth for the materials you aiming for.
Most likely you need to feed your processing facility with small chunks of the asteroid, and depending on the technology of extraction it might be gravel or dust-like particles, but it does not mean that output waste will be those particles or small chunks.
As an example, different floating methods are used to separate and concentrate metal ores, and input is powder like stuff lot of water and lot of bubbles, but if there not so much water on that particular asteroid you have to squeeze as much as possible from the waste, to not loose your water. It means some postprocessing sequence for the waste, which might or might not include forming bricks from the waste at the end.
I will not wonder if it will be easier to smelt and skim the stuff you need and leave the big melted rock, for later use.
## Hazard
No, it's not become a navigational hazard to the equipment. Space is big and all asteroid combined aren't that big compared to space, and on close orbits, the speed difference isn't that high, and to change the situation you have to throw the stuff really hard, which is in fact waste of energy.
But in general, the mining construction have to incorporate some solutions against meteorites, as it will face the problem on the way and on the place, just because there are meteorites flying around.
## Dust cover
Again depends on the body where you are mining, and how you are doing that.
On the Moon, there way much more dust than you will be able to produce and it definitely needs a proper design for the equipment. Same seems to be true for and large size asteroid. But there are different ways to do a proper design and it has not to be a big deal.
The dust is considered to be a good source material because it is already in a form suitable for different methods of separation of the raw ores, so it might be so that the dust will be the target of the mining equipment or something like that. The point is that it most likely will not fly freely around.
If you consider using solar panels as the main source of energy, then there is another important factor to consider - energy needed to process materials is pretty high, so the area where you dig will be small (at any given moment) compared to the solar panel surface and face in opposite direction to the source of the dust.
But again heavily depends on the way you dig and process the materials, a thing which has to be taken into consideration but not a big source of problems by itself.
clogging servos - [Produce a Hermetic Seal with Ferrofluids](https://seals.ferrotec.com/technology/) might solve all your problems in that regard.
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Leftover, even if powder, won't pose much of a hazard to the rest of the solar system if you just drop it in place. It requires a significant input of energy to change its orbit and move it closer or farther from the sun.
Unless the powder is so fine as to be blown by radiation pressure or solar wind (think cigarette smoke particle size), just place it back on an asteroid and it will stay there.
It won’t pose a hazard locally if you don’t come around and kick up the pile. Place it down *carefully* rather than spewing it out, and it will stay where you placed it.
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Let's say a setting contained a world like ours. Due to unfortunate circumstances, a large portal to hell opened up in the middle of the planet. Numerous demons spilled out into our reality, overthrowing governments and killing billions of people. These demon hordes were led by devil archons, who settled in various countries and ruled with an iron fist. These nations were essesenti ally turned into torture camps, where humans were enslaved and murdered for the amusement of their overlords.
The only surviving nation would be a powerful theocracy that managed to hold out against the demonic horde. A collection of priests had gained special abilities that are said to come from God. These abilities would be used to form a barrier that would prevent demons from crossing over into this nation. It would also be used to develop a form of "holy tech" that would be specifically developed to fight demons or banish them back to hell.
A religion would develop, centered around worshipping of the one true god. A high council of priests would actively maintain this barrier, while delegating the running of the church to other members. Religious and secular law would become one, with no separation between church and state. Other faiths would be declared heretical, and life would revolve around traditional values and ethics. People would be equal in the sense that they will be judged accordingly by God for their actions in life, but a social hierarchy would develop that individuals would be pressured to abide by and respect.
How can this country sustain it's theocracy while maintaining a limited form of democracy in this setting?
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# Fear of Failure
Your theocracy is the only thing keeping the demons at bay, so it stands to reason that it's in the population's best interests to keep the theocracy going.
I don't know what any other religious parties can offer except for imminent doom.
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The Theocracy, if somewhat similar in nature to the Catholic church, would almost have to be a meritocracy, as preists are celibate and the titles cannot be inherited. That would be step one. You could build a sort of representative theological federalism by having the local congregations electing their leadership from the local clergy. Those guys represent at a regional level that elects to a state level, that elects to a national level.
The representatives would have to be Ordained to be elected, which would keep the theology relatively consistent. Local communities would be represented and free to communicate up the line all the way to President/Pope.
This should create at least some balance between democracy and theocracy. Not a perfect Utopia, but somewhat plausible.
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**I don't think you can afford the risks inherent with a democratic system.**
In your situation you have a constant shadow hanging over your citizens: the fear of demonic manipulation and infiltration. Furthermore, it's been proven that only one religion "works", and the continued survival of the species requires that all citizens *believe* in it, thus granting power to the authorities to repel the demons.
Non-believers, those who stubbornly wish to subscribe to a different religious view, or those who would engage in conversations regarding the nature of your faith, and its interpretations would, for the sake of mankind, have to be silenced - this is not really debatable in your situation, and you can't risk a new government messing with the settings, as it were.
Here are some examples of policies which society might be divided on, and which sly "politicians" might use to garner votes and support for their platform:
* Taking children away from their parents to train as holy warriors.
* Indoctrinating all children such that the "belief shields are powered".
* Forcibly reeducating, or disposing of non-believers, and dissenters.
Can you afford to allow a public debate on these topics, and risk a divided population?
The only check and balance capable of maintaining order in this incredibly tense situation is a highly moral, autocratic ruler who is willing to be fair and just, yet mercilessly pursue the survival of mankind (which sometimes involves making sacrifices that the population at large may balk at).
Otherwise it would be exceedingly easy for an administration to come to power, manipulate public opinion, silence or otherwise get rid of their political opposition, and, using the threat of annihilation, change the system into one which subjugates their fellow citizens.
People will buy into any measures which their leaders claim will stave off eternal torture in the pits of Hell, and unfortunately you do not have the luxury of putting someone in power for 4 years only to determine that they were not really well suited for the job.
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The Romans managed to create an absolute monarchy while preserving intact the laws and appearance of a republic. A theocracy could obviously do the same. By the way, Roman emperors were, among other things, Pontifices Maximi, great priests... (One thing they were not was emperors, at least not until the end of the 3rd century: they ruled by occupying simultaneosly several key positions in the state, while allowing other people to be elected consuls.) Also look at the [Islamic Republic of Iran](https://en.wikipedia.org/wiki/Iran): it has elections, a parliament, and a president: but it is a theocracy if there ever was one.
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Have regular elections, the same as usual. I believe the theocracy will always win a majority, if they're the only ones who can stop the demonic hordes, and mention that they'll pull their support if they lose - nice and neat, although somewhat shady on the part of the theocrats. No shadier than regular politics though, really, if you think about it.
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## Like the Outremer Kingdoms?
Your idea sounds very much like the Outremer Kingdoms -- the Crusader States -- many of them manned by religious military orders (Knights Templars, Knights Hospitallers, etc) along with secular military power from Europe to form a barrier around the Holy Land.
These religious military orders were authorized by the Pope, but largely operated independently.
**Church defines "What", State defines "How"**
If you look to that medieval example, you will find that the Church defined what was right and wrong, and the State decided how to how ensure that Right is done and Wrong is prohibited, adding in their own laws as needed.
The reality of a horde of demons just outside the barriers would give the populace a common cultural reality - one that nobody could deny. That would help provide a unified society in regards to issues of Faith and Secular law, providing the necessary stability for forming not just a limited democratic republic, but a rather robust and focused one.
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I don't think that an actual democracy would be stable for any length of time. You could have such a society until someone high up in the religious branch said, essentially, "do what we want or we just save the few that obey us."
To make things run more smoothly, they may create a fake democracy where people vote for representatives who can make laws but the church has final veto. this would give people an illusion of control (kind of like our current system). Anyone who doesn't like that system or tries to manipulate it would be named a "demon helper" and made an example of. So, if the church suggests a change in a law, the representatives had better implement it.
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One method would be to have a religious and secular branches of government that service checks and balances for each other. What's the same way executive and legislative powers check each other in the American government.
Have a Congress or Parliament made up of elected officials who have the ability to pass laws. But those laws can be vetoed by a religious counsel a priest. That veto again to be overturned by by a vote of three- fourths of the Congress.
Add other checks and balances that will even out the power structure between the secular and religious government bodies.
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And not some big space gun a mile wide, I'm talking more like "could you pack a nanogram of antihydrogen into a shotgun shell or rifle casing and fire a bullet with it?"
A few conditions and assumptions:
* The gun is made from futuristic polymers, alloys, metamaterials or whatever that would allow the barrel to survive a fifteen megajoule explosion from the inside
* The shooter is similarly cybernetically augmented to withstand the kick of the gun
* The gun must remain effective and combat-ready (i.e. if the initial reaction destroys the bullet before it fires it fails)
* The gun must be practical enough to warrant use. It doesn't matter if it's super expensive or needlessly flamboyant so long as it's still just as effective/more effective than normal firearms (otherwise what's the point?)
Could it be done? Could a sidearm that uses antimatter as a propellant work on the battlefield as a hypervelocity weapon? Or would it simply be too suicidal/too prohibitive compared to a normal gun that uses chemical or electromagnetic propellant?
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A regular gun uses an explosive that generates hot gas, and the expansion of this gas propels the bullet.
Antimatter annihilation produces a large amount of gamma radiation, (when protons annihilate they the direct quark-quark annihilation produces hard gamma rays, and an rain of unstable pions that soon decompose into more gamma rays and neutrinos) The gamma rays eventually deposit energy in the surroundings and you would get quite a lot of heating.
These gamma rays are quite penetrating, and will probably escape from the gun. You don't get a focused explosion with lots of hot gas to propel a bullet instead you get the gun and the the operator being irradiated. Even if you manage to shield the gun, there isn't the release of gas that occurs with regular propellants, so the bullet is not mechanically forced out of the gun at high speed. Its not a very good gun.
Producing antimatter in macroscopic amounts is 'hard' and managing it is also 'hard'. Gunpowder is great in that I can put some in a cartridge, and it just stays there. If I don't put a spark to it, it doesn't do anything. But antimatter needs containment. Containment is heavy. I'd rather not carry a 50kg particle accelerator just to keep the antimatter safe.
OK, suppose these problems are fixed, and the gun fires a bullet without killing its user. Is there any benefit? Muzzle velocities are not limited by the power of our explosives, but by the mechanical properties of bullets in air. If I managed to convert the nuclear energy of annihilation to the kinetic energy in a bullet, the bullet would ablate and slow as it passed through the atmosphere, I wouldn't get more range, or a more dead enemy.
An alternative to an antimatter gun is an antimatter tipped bullet. You would still have the difficulty of containment, but if this is handwaved away, a bullet with a nanogram of antimatter in its tip, designed to annihilate on impact would be a terrible weapon: a .22 sized tactical nuclear warhead.
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Taking the proposition that nanogram of antihydrogen converts into fifteen megajoules, this won't be a fifteen megajoule explosion it will be a fifteen megajoule pulse of gamma radiation. This sounds like too dangerous for the operator. Suicidal if the trooper knowing pulls the trigger or culpable homicide if the lethal hazard hasn't been definitively explained to the trooper by the relevant authorities.
Whatever technology is required to make a weapon use nanograms of antihydrogen as the propellent for a sidearm, it will have to be able to reflect or deflect gamma radiation in ways that absolutely minimize its harmful effects. It is doubtful if "futuristic polymers, alloys, metamaterials or whatever that would allow the barrel to survive a fifteen megajoule explosion from the inside" exist. To do that, requires segue into "magic" materials or technology. Gamma proof force-fields anyone?
Perhaps there might be "futuristic polymers, alloys, metamaterials or whatever that would allow the barrel to survive a fifteen megajoule explosion from the inside", but the structure and mechanics to make an antimatter propellent gun work will be most probably massive, multilayered and complex. Sidearms would definitely be out, an oversized howitzer perhaps. Remote controlled operation most assuredly. Sounds like the sort of weapon that ensures there are an arms limitation treaties.
The cybernetically augmented shooter might be more deadly and dangerous if he threw the gun and its antihydrogen ammunition at his target instead of firing it.
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No. You don't necessarily want detonation because too much of the force is lost in directions *not* along the barrel. And antimatter matter would detonate. Plus you'd get a lethal dose of gamma radiation, you're not shielding that without a whole lot of lead (my vest? yeah it weighs 400 pounds, but boy wait till the enemy walks into my line of fire...). Anyway, there's no known technology which would allow the stable storage of antimatter for more than seconds or minutes, so no you're not going to be carrying around bullets containing antimatter. Back to detonation, sorry for wandering. The most effective propellant for a weapon depends on lots of factors, but its burn is designed to be slow enough to accelerate a bullet through the barrel using the gasses released. Without some sort of magical force field technology, you're not doing that with antimatter+matter collisions.
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I actually use something like that, but with magic involved. The other answers are good but also missing one point. If you actually manage to fire the gun without having instant doom, i.e. the bullet leaves the barrel in the right direction, then there are still a lot of air molecules getting in the way of the bullet before it can reach its target. Imagine the bullet is somehow scientifically shielded against the air particles, how would the shield "know" that the target is reached? The shield can't be simply "used up" because then the bullet would only work on certain distances with the right wind. It could't act upon different "pressure" because I image the pressure is the highest when the bullet is fired inside the barrel. The only science-ish solution I see is "coating" the bullet in the barrel after being fired, e.g. midway out of the barrel.
This problem also applies to James' version of the bullet.
PS: My version of the bullet destroys soul on impact, resulting in death on contact. Very, very forbidden.
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There is a solution to this problem. Convert annihilation energy to electricity and power a tiny rail gun with it. A tiny handheld gun will give the impact of a 7.62 dragunov. The recoil would be tough to manage but it would be within the realm of possibility.
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I realize that you specifically ask about a gun that uses the "explosion" of annihilated antimatter to propel the bullet so this reply might not be what you want. But, doing it that way is not a good way to take advantage of the antimatter.
## Antimatter battery and a electromagnetic mass-driver
Instead of using the annihilation of antimatter as an explosion (as it will not cause hot gasses, rather high energy radiation) it might be better to consider an advanced antimatter fuel-cell. Antimatter is held in some kind of containment and minuscule amounts are freed to annihilate. The tiny discharge of radiation is used by the fuel cell to charge electric capacitors.
The capacitors are then in turn used to charge electromagnetic coils which accelerate a magnetized bullet towards the target at high speed.
Benefits over a normal chemical gun is that only the bullets need to be stored (making ammo take less space - meaning one can have more of it). Also there is no discharge of hot/poisonous gasses which might be problematic in some environments. The antimatter fuel cell might never need a replacement due to it's energy density.
For a really endless gun - replace the mass-driver with a laser, or go half way and let the magnetic coils accelerate super-heated ionized gas.
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Most of the planets that we know of have a sidereal day (rotational period) that is shorter or on the same order of magnitude as their sidereal year (orbital period), the latter being the case in tidal locked bodies.
Without invoking magic or super-advanced technology, is it possible for **a planet to have a sidereal day that is significantly *longer* than its sidereal year?**
What natural processes could explain such a situation?
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The classic example here is [Venus](https://en.wikipedia.org/wiki/Venus), with a sidereal day of 245 Earth days and a sidereal year of 224.7 Earth days - clearly less than its sidereal day. I wrote [an answer related to this](https://astronomy.stackexchange.com/a/14382/2153) on Astronomy Stack Exchange that explains Venus's slow rotation (and why it has retrograde rotation). The sequence of events, according to [Alemi & Steveson (2006)](http://adsabs.harvard.edu/abs/2006DPS....38.0703A), is as follows:
1. A large body collides with Venus in a [giant impact](https://en.wikipedia.org/wiki/Giant_impact_hypothesis).
2. The resulting debris coalesces into a disk and then eventually a moon, which moves away because of [tidal acceleration](https://en.wikipedia.org/wiki/Tidal_acceleration).
3. Venus is hit by another large body, which *reverses* its rotation.
4. The moon moves inwards and collides with Venus.
Now, this merely produced a sidereal day that is only slightly longer than a sidereal year. It seems quite possible that the second giant impact could have resulted in a different scenario. The motion of the moon falling towards the planet will accelerate the planet's rotation a bit. All the second impact has to do is change the planet's angular velocity just enough prior to the collision with the moon.
I wish I could give you more specific information about the exact necessary velocity and angle of the impacting bodies. The problem is that the proposed giant impacts on Venus haven't been studied in nearly as much depth as the collision between Earth and Theia that gave rise to the Moon, and it's a much more complicated problem to deal with. In terms of strict feasibility, however, the giant impact $\to$ moon formation $\to$ second giant impact $\to$ collision with moon scenario can almost certainly work.
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In [**a previous question**](https://worldbuilding.stackexchange.com/questions/38876/selling-your-uploaded-copy-of-yourself), I asked about whether a market for uploaded minds could exist. The overwhelming consensus of the answers was that it would pose astonishing ethical challenges and be radically disruptive of the present-day economy (why hire a mediocre physicist when you can have a mind-clone of Steven Hawking doing your bidding?), potentially leading to widespread unemployment among the flesh-bound remaining humans.
Now one of the problems with mind-clones is that they might not be willing to serve your goals (the 1000 Hawking mind-clones might have ethical problems with your dastardly plan to take over the world, um, severely reducing labor productivity).
So you decided that you want to blend several minds - one that is really good at math and physics, for instance, with another mind that is *really* good at unquestioningly taking orders and yet a third that has *unlimited* devotion to your cause (say an upload of yourself).
**If that's even possible, how would it work?**
I've envisioned several possible pathways already, but I am hoping WB can tell me if they're far-fetched or not, of if other ways would work better:
* Easy Plug and Play: Library modules for themes : a library for physics skills, another for fanatical devotion, etc. You pick and choose.
* Hard Plug and Play: Library modules for physical areas of the brain - Broca centers, a bunch for the multitude of vision processing centers, 20 for various pre-frontal cortex areas, etc.
* Emulators All the Way Down: Integrating libraries from multiple minds is only possible after tediously constructing "translation tables" from one holistic mind-representation to another, effectively insulating the modules and changing the outputs from one module to another via translation.
* Grand Mal Seizure: No libraries are possible, trying to blend various minds leads to insanity, and any work you do must be squeezed in the few hours of sanity before the decay.
* Something else altogether ?
Note that the assumptions from the previous questions hold, i.e. no legal status for uploads ("just software"), nondestructive uploads possible and accurate, fully immersive Virtual Reality is mature tech and an easy way to interact w/ uploads. See the linked question and replies for more info.
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As an engineer what I sometimes tell people is this:
**"Anything is possible, but not necessarily probable."**
Currently, we don't understand the human brain nearly well enough to answer your question.
In the far flung future this may very well work. However, I believe it would be a significantly more difficult challenge to ***blend*** minds than to simply ***copy*** them.
When I think of my own skills as a programmer, I can clearly differentiate between my knowledge of a subject, and the memory of how I acquired that knowledge, however in recalling that information the one piece of information will often reference the other. In fact, some of the most well known methods of memorizing large volumes of information is through association (I'll try to link a wiki article later)
Basically, even though we perform a conscious filtering of our personal memories from our technical knowledge, in our brain that information is still classified as a "memory".
I'm not certain that you could separate that knowledge from the personal memories and not seriously compromise the sanity and overall ability to think of the mind in question.
In short, I don't think any except the **"few hours of sanity before the decay"** options makes sense, and even then, I think that the confusion of "waking up" with different memories mixing together would probably not make for a very useful slave.
Instead, consider that you have complete control over the environment where these mind-clones exist! You're basically running a Virtual Machine on a server.
You can ***manipulate the parameters of that mind's environment***. Do so!
Awake the mind-clone in a simulated environment in which he is solving a problem in order to save the world! Better yet, don't give him the full problem to solve. Create several instances of that brilliant mind, and feed each of them *a part* of the overall problem. This way none of them will be able to piece together what they're actually solving - until it's far too late.
If for some reason they don't want to cooperate you can twist their arm in various ways. After all, they are fully susceptible to psychological manipulation. Start kidnapping or "killing" their virtual loved ones, or simply change the parameters of their world such that they feel compelled to help you - after all, the mind-clone might not even be aware that it *is* a virtual copy, and that its world is not real.
Your huge advantage is that you can always create more instances of that mind should one figure out your game-plan and find a way to resist you.
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Check out [How to Create a Mind](https://en.wikipedia.org/wiki/How_to_Create_a_Mind) by Raymond "Ray" Kurzweil. Looking up the reference, I noticed that there are also speaking engagements posted on You-Tube.
The neocortex is wired up to create many many "basic pattern matchers" as the fundimental unit. Each one as inputs of other pattern matchers, and itself feeds its output to others.
They don't have GUIDs. What one of them symbolizes is only meaningful in context, seeing what feeds to it. And what do *those* mean? You only know by following it all the way down to sensory inputs, and for stored memories you would have to figure out how they came to be encoded as it's not connected to inputs *now*.
Mapping one instance of such a network to another is a **very difficult** task, and it would only be approximate for shared concepts.
This is a plot idea I've done quite a bit of thinking on myself, concerning the development of technology to modify uploaded minds with "canned" skills that can apply to anyone, rather than having to laboriously learn a skill.
So don't try to merge minds like combining pieces. Rather, work on virtualized versions of normal learning and mental change. You have person A that needs skill B, well you *can* make him have the mental plasticity and learning capability of a youngster. Then optimize and accelerate the take-up of the new skill by running just the affected brain parts at an accelerated rate. Person A can experience lessons and practice at a superhuman rate, and quickly (from our point of view) learn B. You can also make checkpoints and roll back the mind state if something goes wrong.
You *can* merge deltas of the same initial mind, if they are not too far out of sync. So many copies of A can be learning in parallel.
For getting just the right outcome of attitude and beliefs, you can just keep trying different indoctrination and persuasion methods until you get the desired result.
You can well imagine that these accelerated learning techniques are not at all friendly to the original personality. What *could* be done by a secret unethical shop might be very different from how your paying customers "live" in their afterlife datacenter.
Imagine a resident desides he wants to learn to play tennis to a high degree of accomplishment, orders it from the concearge and aggrees on a price. A week later he gets a delta to merge, and with a few days of practice to properly integrate everything, he's a happy customer. But he doesn't realize (or doesn't *care*) that the delta was prepared by mutilating, mistreating, enslaving and terminating thousands of copies of himself! He never remembers waking up to be told that he's the copy and must brutally practice on behalf of the original.
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What you are looking for is called [Gestalt](https://en.wikipedia.org/wiki/Gestalt_psychology) phenomenon. The Gestalt school of thought states that "The whole is different from the sum of its parts." Obviously the trivial answer is to just boot up two mind images with different behaviors, and put them in a room. This is identical to the ever challenging task of leadership: how do you get different individuals to work together towards their goals. To go beyond that, you need the whole to be more than just the sum of two minds.
Unfortunately, Gestalt behaviors are notoriously difficult to predict. Its very hard to tell whether your merging of Motzart and Einstein will bring harmony to physics, or if the best of both of them will cancel each other out, leaving nothing.
There is one approach you could take, which has a proven track record of generating Gestalt results successfully: child rearing. Children are definitely not a simple summation of their parents, but one certainly has to admit that there are always aspects of the parents in the child. You could give two minds a "blank slate" with which to work together to try to build an even more successful mind. Since computer rights would be in their infancy, you could even destroy the child if it didn't meet your needs.
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**Merging minds is possible but and prone to unexpected and undesirable behavior.**
Assuming that minds can be uploaded without real difficulty then answers to how to codify and execute an uploaded mind have been answered. Further, if the data structures for a mind are well known, manipulating them should be straight forward. After all, at this point, a mind is "just software", a very long string of ones and zeros. Manipulating these kinds of hyper complex data structures should be pretty easy by then.
However, the difficulty will arise in managing all the feedback loops and inter-dependencies between all the various parts of the mind. Drawing a corollary with DNA, making even a single "bit" change in a gene can mean the difference between a properly functioning protein and totally dysfunctional one. Likewise, making small changes to significant portions of the mind model may cause the executing mind to go into infinite loops or any number of mental break downs.
I'm not convinced that modules for skills or attributes will be possible as the attributes of a mind are emergent properties of the mind's representation. Maybe they could be added but the trick would then be integrating those skills/ideas/capabilities into the greater whole of the mind, and doing so in a seamless way.
Fundamentally, everything a human knows and does is interconnected. Learning to play guitar can be written down in a book but the actual knowing is wrapped both in the brain and in muscle memory. That knowledge is also wrapped up in the memories of bleeding fingers, intense frustration and the joys of accomplishment. A virtual mind that has been given just the skills or abilities from another mind may detect the discontinuities and either reject them or go insane when trying to resolve the discrepancies. A merge operation between two or three minds may require a complete rewrite of that mind's memories to make the discrepancies disappear.
*So, yes. It could be done but it's really really hard.*
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I am going to expand upon an earlier comment, since I feel like it deserves to be better fleshed out.
## No, brain melding won't work
Basically, unless you want to do some serious handwaving then the human brain is just too complicated to mix and match like this. As others have said, your best case scenario is a short lived upload that soon goes crazy from having multiple, possibly contradicting, sets of memories and skills.
## Luckily, you don't need it
Assuming that your main concern is convincing the uploads to continue working, there are plenty of feasible and much less extreme ways of motivating them besides melding in a copy of yourself that wants to further your goals. @AndreiROM suggests using the VR environment the uploads existing to coerce them into working for you, but I am going to put forward a more ethical solution:
## Treat uploads like employees
This is a very basic idea, but one that should work for 99% of the brain upload use cases. Assume that you want to obtain an upload of someone legally and with their full cooperation. Now, my answer to the previous question mentioned that the uploadee could just license their upload and get paid for it in the real world. But that still leaves the question of how to keep the upload itself motivated to work. And here is where the employee model comes into play.
Uploads exist in some kind of VR sandbox, which is necessary for them to perform whatever they have been licensed for. They are also, at their basic, very advanced software. Well, most software only "work" a fraction of the time they are in use. The rest of that time is spent idle, waiting for other tasks to finish or user input to occur.
As long as you can speed up the relative time of your upload VR sandbox, you can make it so that the couple of seconds that a user is typing a request feels like a couple of hours to the uploaded personality. As long as they have something to occupy that free time, you are essentially paying for their work with leisure activities. And since it is all virtual, the only real cost is programming the VR itself.
What this boils down to is different companies could offer different "benefit packages" to the uploaded personalities, and that could be a part of the negotiating that occurs pre-licensing. Real-you would need to worry about not just how much they get paid for the license, but also whether the benefits package would keep upload-you happy and occupied for extended periods of time.
## Hit the reset button
Another possible route would be to "reset" the upload after every day. This would let you have a very basic VR environment for the upload without it getting stale, because to as far as the upload is concerned every day is the first day of the job. The trade off here is not needing an elaborate VR sandbox to entertain your uploads, but resetting them would remove any chance of them having adaptive learning. This would probably be the route used for more menial jobs, such as customer service roles, which stay mostly the same every day.
## Assume positive intent
The above points all assume that the upload is given willingly, and that the personality in it understands that they were uploaded and are being compensated for their work in some way. There could very well be a different case where you have an illegally obtained upload and need to coerce them into doing something for you.
But for the most part, I would treat the uploads the same as I would any "real" person. Most of the time, if you want them to work for you you would just hire them and compensate them in some manner. Or you can kidnap them and force them to using different unethical means. The only difference with uploads is that you have direct control over their "world" and so can make both the positive and negative incentives that much more specific and elaborate.
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One of my characters has the ability to manipulate time, and thus I've found that if used properly, that ability isn't presented with much in the way of obstacles. Once time has stopped, unless they are facing someone with the same abilities or some physical challenge that would be difficult regardless, it's hard for most to stand against them. So I've toyed with the idea of a metal or material that is "time resistant" but I'm not entirely sure of a good way to explain *how* it resists their abilities, but not all things (like it could still be melted or something). I want a little bit more than "it just does" and so I've run into a wall.
Theoretically I can have armor or devices made with this "time resistant" material, but I don't want to hand wave it away if possible. Are there any ideas for a good justification?
The story takes place in a science-fantasy universe with civilizations up to Type IV, but primarily with Types II and III. So it's reasonable that this stuff could be imported, or manufactured rather than natural. I'm mainly looking for a pseudo-scientific way this might work. But there's magic and stuff so it doesn't need to be that strict.
Thoughts?
Note: In case it helps, the character manipulates time in an area around themselves, but it doesn't affect everything in the universe if they stop time. If things enter or leave this area they are affected or go back to normal accordingly. Basically time is treated as a dimension that can be traveled through forwards and backwards and "stopping time" is halting that movement for things in this area. (At least that's how it works in my head right now.)
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When we talk about "manipulating time" from a physics perspective, typically we are referring to things that are well modeled using a model that permits manipulating time. Science is not very good at making statements about the truth of reality, merely statements which appear so astonishingly close to the truth that one can believe they are true and get away with it. One of the easiest ways to weave magic with science like this is to define a mechanic which refutes some fundamental assumption of science, but does so gently enough not to break the world.
A "time resistant" material might simply be a material which is not well modeled using our usual approaches. Because we're working with time manipulation, it would be fun to create a material which has properties which are not time invariant. Time invariance is a very important feature of science: it says that the properties science is studying do not vary with time. The results may change with time, such as an electric stove that gets hot as you turn it on, but the fundamental scientific principles of electricity and heat do not change with time.
You might have a material where most of its properties are time invariant, like any other material science is comfortable with. However, when put near a time manipulation field like your character has, it exhibits non-time-invariant behavior which makes it very difficult to move this field through the material. Think of it like an [ooblick](https://www.youtube.com/watch?v=Rj0UJSuCkmQ), whose properties appear to change when stressed in the right way.
Thanks to [Nother's theorem](https://en.wikipedia.org/wiki/Noether's_theorem), we know that every symmetry in Lagrangian equations has a corresponding conserved variable. That sentence is a mouthful, but the effects of the theorem are easier to understand. If you have time-invariance (the rules of physics do not change with time), you naturally have conservation of energy as a consequence of the equations. If you have position-invariance (the rules of physics are the same at all positions in the universe), you naturally have conservation of momentum. Let us assume that your time manipulator cannot violate the conservation of energy. Why? Because if you can violate the conservation of energy with your ability, all of science falls on its face\*, and you said you want some resemblance of science. This means, as far as the time manipulating character understands, their abilities *must* be time-invariant. The two go hand in hand, thanks to the mathematics and Nother's theorem. If the time-resistant armor exhibits non-time-invariant behaviors when subjected to time manipulation, the conservation of energy appears to fly out the window. **This means the character will have trouble understand what is happening near the armor when they use their time manipulation effects.** The fundamental assumptions of the universe that they are making fail.
Of course, there's no reason to say this actually has to violate the conservation of energy, it just needs to appear so from the perspective of the time manipulator. Perhaps they feel the armor sucking them dry when they use the field near it, when in reality all it's doing is taking advantage of the fact that their understanding of time manipulation is not actually the real ontological rules of time manipulation. This would lead them to feel like it takes *work* to use the field near this armor.
You could pull a wave/particle duality stunt with this as well. If, for instance, the way the characters manipulate time is described using wave behavior, the armor may be manipulated in a way that is far better modeled using particle physics. This would be the same as wave/particle duality for photons or electrons: its not that an electron *is* a wave or *is* a particle, its that in some circumstances you can model it best as a wave, and some circumstances you can model it best as a particle. If the armor can exhibit behaviors which are best modeled as particles, anyone who assumes time manipulation effects work as waves will be sorely displeased with how things work. The results may be as counter intuitive for your characters as the [Delayed Choice Quantum Eraser](https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser) experiments, whose results are completely and utterly *baffling* if you assume photons are either waves or particles.
Interestingly, this also suggests a way for the time manipulators to overcome the armor. If the wearer of the armor starts to assume the armor always causes time-manipulation effects to behave as though marshaled by particles, there may be regions where they get confused as well. Perhaps there is a way to manipulate time such that the manipulation is poorly modeled by both waves *and* particles. In this case, one who understands the time-manipulation analogue to quantum physics would be able to do things that the armor wearer could never expect. Thus, the armor wearer might leave openings in their defenses, assuming the armor can do more than it really can. For an example of where things like this can go crazy, take a look at [Bell's Inequalities](https://en.wikipedia.org/wiki/Bell's_theorem). If you are assuming all of the funny behavior of quantum mechanics is merely us not knowing enough about the particles we are observing, you believe in a "local variable hypothesis," which has been proven to be an inadequate model of quantum behaviors.
Now none of what I have suggested here for the armor is *actual* physics. There's no QM involved . The links are all valid QM, but the applications with respect to time manipulation are all made up. However, these suggestions do take up the flavor of the problems tackled by QM researchers, so that flavor may lend credibility to your pseudoscience.
\* Most of modern scientific theories are modeled using Lagrangian equations. Even in General Relativity, there is a [conserved value](https://physics.stackexchange.com/questions/177852/noethers-theorem-in-general-relativity) we can call energy, though admittedly it is more complicated than our typical formulations of it.
[Answer]
You could take a relatively simple approach to this and say that materials that are themselves increasingly invariant with time are increasingly resistant to temporal manipulation.
As examples, paper is particularly fleeting in its existence and would pose no resistance at all. Things like bricks, recently made and soon to decay would also be barely a shadow, But gold or granite, materials that stand invariable through the ages would be largely impenetrable to him. (It also gives you a reason for golden armour, but that's by the by.)
By your question you're looking for a particular unobtanium grade of time resistance that I'm going to call eternium. Gold tarnishes, granite erodes but eternium is unchanging, unreactive and incredibly hard to work with.
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If you want to be completely scientific about it, then stopping time is extremely overpowered: every single physical law whose equation has time in it deals pretty poorly with having it reduced to zero (for example any force becomes infinite). Not to discourage you, of course; story-breaker powers are often the most interesting to write and read about. Although given that you are writing about a guy with time powers, I assume that you will be OK with some shaky physics, so here goes nothing. First, you could have a material that exists in multiple or every dimension at once, à la [Ice Nine](https://en.wikipedia.org/wiki/Ice-nine) or hyperfiber, which would work by spreading the energy to the past, future, or other universes. Alternatively, you could have large covalent lattice structures, such as diamond, resist the effects of time stoppage by again spreading the force across every atom. Or, if you want the material to be even more sciencey, just say something about quantum entangling to a place outside the time-stop
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>
> *the character manipulates time in an area around themselves*
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Apparently, things with mass cause a dip in the fabric of space-time that affects the area around them. If you want to (mis-?)use the latest science in your fiction, look into some of the new results about gravitational waves (from LIGO) as well as the new results about the Higgs field (from CERN). Your story might be able to use the concepts of (magically?) rapidly changing mass and/or having materials and particles of types that do or do not interact with the field as appropriate for your story.
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The problem with using "relativity" approaches is that in most cases, time slows down for the experimentee rather than speeding up. This probably has the opposite effect than what you want
i.e. to "Stop" time, you probably want to be able to move freely while the rest of the world stops, but with relativity, it is you who will stop (so you will appear paused to everyone else - great for travelling into the future, not as good for stopping the flow of time).
According to General Relativity, for super heavy materials, like black holes, time for objects close to it would slow down or stop. As I said, you want the opposite effect, so you want a sort of "Reverse Time Dilation" using a large amount of exotic matter with negative mass or anti-gravity or something.
(Either that or your physicists have cracked how exactly time dilation works and have found a way to replicate and manipulate it)
This would mean time would speed up for the user rather than slowing down, in other words, everything else would appear to slow down. You probably couldn't halt the world to a stop, but make it reaaaaalllllyyyy slow...
[Answer]
many time manipulation theories I have heard of involve massive sums of energy....that being said as metals can be used to deflect and ground energies as in faraday cages your answer may be found there....say the person evolve in a way that their mitochondria evolved in such a way it was able to generate the necessary energy you could even tie this to the magickal powers....but the metals could deflect the enegries and maybe even store them and or reuse them to the wearers ends....
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I’m writing a post-apocalyptic novel, but I have a problem when dealing with daily life in a post-apocalyptic war zone. I know that I might know how civilians or soldiers live in a war zone just by reading the stories of those who survived, but but I have problems because my war zones, as well as the armies that fight are atypical.
The setting takes place in buffer zones called "Protected Areas". These zones have been established after World War III broke. The war was not fought with nuclear weapons, but mankind saw the use of chemical and biological WMDs that have made a much of the planet uninhabitable. The remaining world governments decided to stop using these weapons, and, in order to make the enemy territory conquered economically advantageous, created the Protected Areas, buffer zones between the countries at war, where all the soldiers would be deployed.
What's the problem in these zones?
* First of all, the world is a crapsack world. There are few resources, and they are rationed. The daily life of civilians is a hell made of deprivations and exhausting work, and living conditions are worse. 70% of the land is uninhabitable. Every available resource is diverted to the military. Imagine 1984 but post apocalyptic and without a Big Brother
* There a no civilians in the Protected Areas. There are no schools, no hospitals, no official places of worship. There are only military infrastructure, and all that is "civil" is officiously created by the same soldiers.
* These areas are isolated and secured from the rest of the world. The soldiers on guard outside the zones must ensure that no one enters inside, but once inside, you can not go out, except through long bureaucratic procedures that usually are useless.
* We come to the crucial point. Soldiers are not adults. Children and youth are the greatest victims of this era . The war was so devastating to half the world's population. Adults left have the task of procreation (and thus to create new soldiers) and maintain the standing military- industrial complex necessary for war. Every young person aged 12 years and over is required to fight. Young people are considered cannon fodder, so they are sent into the fray without a real training, but only after a quick smattering on how to shoot and how to survive in a war zone. So all the soldiers are children, teenagers or young trapped in areas from which they cannot escape. From the outside came only other soldiers or rations, and the average life expectancy is 15 years. Oldest soldiers are in their early twenties. In addition, these soldiers are isolated by the outside military staff. They are simply ordered to shoot at anyone who is an enemy and to advance.
* Although the PA are secured from the outside, the young soldiers inside continue to fight for three reasons. The first is that if their company does not achieve results, the supplies are not sent, because the General Staff considers unproductive that front. In addition, radio supplied to the various patrols, if tuned to outside frequencies, broadcast only government propaganda.
The second reason is the hope of returning home. In fact, if a soldier reaches 22, 23 years of age, it is evacuated from the PA and reintegrated into civil society. And as the third reason, the psychology of young people. The weaker mind become indifferent to the war, and for them there is no reason to leave.
* There is a reason why governments send only young to die. An adult is in possession of expertise vital to the survival of the machine. If an adult dies, his death is a huge loss for the State. A young instead is a expendable pawn . A woman gives birth to six children on average, so even if the death curve is high, so are that of the births.
So, even assuming that there is a minority of deserters guys, how the life for all those young people, abandoned by their own countries, who fight every day to steal a few meters from the enemy, would look like?
EDIT
Although the two answers given me so far have helped me a lot in defining the setting, the question is different: how is daily life within these areas for soldiers who live there? Keep in mind this.
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I don't know if I would call this post-apocalyptic. "Post" implies the apocalypse is over. It sounds like your apocalypse is just getting started. What a dreadful world to live in.
The good news is, we know children survive. Why? Well, first off you mentioned that some actually spend enough time in the warzone to be freed from service, to rejoin the world as a civilian. In fact, we know a lot of them do. Why? Because they have babies. Assuming the horrid life you say for civilians, I doubt women who are in constant pregnancy and labor live past 35, so realistically they can only have perhaps 7 or 8 children. This means, by definition, at least 25% of the women need to survive their service, at a bare minimum.
We also know the children survive, because this is not the first time children have been put into warfare:
[](https://i.stack.imgur.com/qDlBVm.jpg) [](https://i.stack.imgur.com/G9RSum.jpg) [](https://i.stack.imgur.com/grF0om.jpg) [](https://i.stack.imgur.com/rs6eAm.jpg)
*Okay, that's probably just about the single most depressing Google image search I've ever done. I'll try to stick to fiction from here on out*
Children of the age 12-20 who have seen war are typically no longer considered children. They are young adults. A child on the battlefield does not live long. They fight with the ferocity of adults, and die just like adults.
So we know a bit more about this world. We know they enter service at 12, life expectancy of 15, so I'd peg the line between enlisted and officer at roughly 15. There may not be an actual line between the enlisted and the officers, but there will be some sort of recognition that maybe we should listen to the guys who lived longer than average. You said there are some that are in their early twenties, which means one may find themselves responsible for other human lives for about eight years. Yeah. Definitely not children, they're not children at all.
Now I like to believe the human mind is pliant. You can't stick something in there that it can't uproot. I've seen grown men check themselves into the VA and gain control over their PTSD, so if those grown men can rise to that challenge, a bunch of flexible-minded children certainly can. While you would definitely be sent to the battlefield with glorious indoctrination of "fight valiantly, die gloriously," that would erode quickly as the gunfire cackles over your head. You'd start to realize that maybe skipping the second half of that indoctrination phase is in your best interest.
I think the key to society in the Protected Area is in the officers who understand a fundamental tenant of warfare: you do not have to win. All you have to do is not lose, and continue not losing until the other side either trips up, or decides it isn't worth the fight. The indoctrination would desperately try to keep this secret from them, but I don't see how young men and women can send their brothers and sisters to die for years on end and none of them figure out that maybe simply not losing is enough. Especially since losing means you don't have enough birthing population to keep up the war.
I find this important because it suggests that you have the potential for *wise* leaders on the battlefield, even among childre-- I mean young adults. This is where I think you would see some fracturing in the states' plans. The wisest of their young leaders may decide that the game needs to change. They may start changing the strategy, to permit a different sort of life. You would start seeing large contingents learning that they don't need to fight. What's to stop them? All they have to do is be good enough warriors that the other side would choose not to engage them. Learning not to die gloriously is a powerful lesson.
[](https://i.stack.imgur.com/sxDC7m.jpg)
>
> Oh, get your hands down. Do not salute me. There are goddamn snipers all around this area
> who'd love to grease an officer. I'm Lieutenant Dan Taylor. Welcome to
> Fort Platoon.
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*Fictional warriors are much easier to look at than the real ones. And sometimes they even show how the wise leader can learn a thing or two about not dying from his men.*
Of course, the states would respond, but the only response they can give is to cut supplies to the children, in hopes of forcing them to fight in some twisted parody of the Hunger Games. But, like in the Games, this opens a chink in the state's armor. **Something is getting out of the Protected Area: information.** The states cannot prevent such warriors from changing strategies unless they are observing them. There is now a communication channel open between the wise warriors and the state leadership.
[](https://i.stack.imgur.com/yGC4wm.jpg)
**What happens next depends on what sort of story you want to write.**
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Cort Ammon's answer covers most of the salient points, so I will suggest the real key to the story is what is happening outside of the combat zones.
There must be some sort of actual objective to be fighting for, otherwise the various polities will be hoarding resources to protect themselves and try to recover. Whatever is "out there" is obviously so valuable that it is worth expending manpower and resources to achieve. This will be the driving purpose of all the various sides in the war, and colour all their actions and decision making. Please note this does not mean the objectives are "rational" in the sense that you or I think of as "rational". No one watching the news about the fighting in Syria or against ISIS would conclude the goals of most of the various parties in the conflict are "rational" outside of "don't be conquered by the other guy".
What a lot of people fail to recognize is much of the fighting in that region is driven by religious and ethnic hatreds: Shia and Sunni radicals are fighting to exterminate the apostate "other" sect, and woe betide any Christians, Jews, Sufis, Zoroastrians etc. in the way. Similarly, being Kurdish, Yazidi, Persian, Arab, Assyrian etc. could lead to a very unpleasant experience if you are in the way of one or more of the various forces fighting in the region.
So much of what is going on outside of the combat zones is a never ending propaganda battle to indoctrinate the forces and population with hatred of "the other". Only if "the other" is considered such an existential threat to the society and culture will everyone be willing to go all out in order to defeat them.
The other thing which will take place outside the combat zones will be study of what is going on inside the combat zones and operational research to provide whatever edge that can be given to the fighting forces inside. Throwing away waves of children in human wave attacks may be very simplistic, but in the real world only can achieve limited success if it is backed up by some sort of "real" military force to exploit any gains made. During the Iran Iraq war of the 1980's, Iranians routinely used human wave attacks by child soldiers to clear minefields and obstacles, but made little headway against the Iraqis since the Iranian Army had been gutted by the Revolution and few professional officers or even working equipment was available to exploit these breaches. (Perhaps fortunately for the Iranians, the Iraqis were equally hamstrung by the tight political control exerted over the Iraqi officer corps by the Ba'ath Socialist Party).
Other polities will certainly explore other ways to make their forces more effective in this very Darwinian environment, and we have seen a lot in the real world, everything from various forms of insurgencies, use of remote weapons like mines and IED's, infiltration tactics and developing Special Operations Forces to find and exploit weak points and strategic targets. You can't discount the importance of logistics either; whoever can find better ways to supply forces in the combat zone will gain a terrific advantage.
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What is the tech level in the post apocalyptic world?
Children have less muscle mass and so are ineffective with melee weapons and can't carry much armor. If modern weapons are available they are much more dangerous, but then their use of limited ammunition and firearms is another problem.
In the first case adults would be much better fighters. In the second there would have to be a major industrial complex backing up the army, or constant raids and ammunition shortages.
Why are they fighting? Is it just self defense or is there a recourse they are all fighting over. If the first your exiles could buy peace by not attacking their neighbors. If the second they will have to raid and fight against the others.
Why hasn't someone won?
Perpetual warfare is very rare, its hard to keep a war going over a hundred years, because in war victories can cascade. Winning one battle destroys enemy troops and makes it more likely that you will win the next battle. These effects tend to cascade till one side wins easily. Long wars usually occur when there is a massive advantage to being a defender, when you lose a battle you retreat to your castles and use its massive advantage to rebuild your forces. You may want to flesh out the defenses of your protected areas to serve this purpose.
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Possible situations where this might happen:
* Early human culture develops in a situation where audio recording and recall is straightforward - perhaps in a place where there is an abundance of tame and very talented parrots.
OR
* After some catastrophe that kills their parents and destroys most cultural artifacts, a group of children on a distant planet that has become separated from the rest of human civilisation grow up with a smart computer that can speak to them, and record what they say, but has no visual display.
Let's assume that in either of these situations, long-term storage of usefully large amounts of audio is possible, as is searching/indexing the stored audio (and all other things we commonly do with text manipulation, including sending it, versioning it, signing it...)
Alternatively,
Someone stumbles upon technology similar to the wax cylinder phonograph before any particular writing system has taken hold. (We can't then assume that there would initially be no issues with search, storage and transport; let's assume that in this case, the technology develops fast enough that these kinks get ironed out before anyone minds too much.)
Anyway, my question:
**Would this human culture be likely to develop *written* language?** If so, could we predict any characteristics of that written language?
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I think with that alone, no. Written language would still develop for many reasons.
The first is fidelity. Even if you assure me that your parrots remember perfectly, I will doubt it. Likewise, laying my faith solely in an AI leaves me with little ability to verify records. Also, records naturally include pictures. Those work better with captions, not accompanying audio.
The second issue is portability. Paper moves easier than parrots. Text data is easier to parse than audio, taking practically no processing power. Text is also inherently searchable. Even computers search audio by first converting it to text. This may not be necessarily true with a "super computer", but it is true in reality.
The third issue is human consumption. Generally, people can read faster than they can hear speech for similar levels of comprehension. Even if you practice listening to sped up audio, you will probably top out at about double speed, around 400 words per minute. Meanwhile, it doesn't take much practice with reading to break that.
A fourth issue is the intrinsically different voice and prose that wiring can bring compared to voice. With the most talented writers, this is art. Naturally, this is sometimes done in speech, but they are mimicking writing. No one really talks like that. Beyond this is the value of personal interpretation. Speech makes this harder.
Fifth, there's the value of study. Reading allows you to dart across a page, back and forth, picking up random bits in any order as you interest dictates. This seems impossible to me for speech.
There may be others.
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I suggest that there are very strong reasons to develop written language of some form, even with a perfect audio recall system.
1. Transmission of information. This doesn't just mean computerised transmission, but the wider meaning. With audio, you need to have an environment where you can hear one another. This becomes a problem surprisingly often. Sticking with an an early culture, how do you warn people coming after you about the danger on the trail? If you leave a visual message, you don't have to wait around.
Getting to a slightly more modern position, how would spies communicate? Even going back to Roman times, secrets have been passed in writing to prevent them being overheard, or to allow the exchange to take place in public. This doesn't work if you don't have some kind of visual representation.
In an even more modern sense, without writing, how would you warn of speed limits on roads? It's plausible that you could have a speedometer which tells you the speed you're going, but until you've figured out some form of data transmission method, your only hope for speed limit signs is very loud shouting!
2. Natural environment. When you think about it, humans developed in a audio-biased environment. We could talk to one another long before we developed written language, but there are prehistoric paintings. They appear to be images of things people are likely to have seen - it's a lot easier to draw a picture of an animal with distinguishing features for later reference than to sufficiently describe one. It's entirely possible that they are purely decorative too, which wouldn't really work with audio...
3. Decoration. Writing is essentially a set of formalised pictures. Once you have pictures, it doesn't take a huge jump to get to a form of writing - think hieroglyphs as one example. And humans like decoration. Body painting was a very early discovery, and we're not the only ones who do it (although we might be the only ones who are purely aiming for artistic appeal - hard to tell!) with creatures like the [Decorator Crab](https://en.wikipedia.org/wiki/Decorator_crab).
4. Architecture. Once you get to trying to design more complex buildings, you want designs you can communicate once and refer back to. With audio-only, you'd have to either re-listen to the audio, or remeasure, when you got to, say, how wide the windows should be. If you can write it down on the plan, it's a lot easier. This gets even more critical with bridges, for example.
It's entirely possible that the written language in this situation might be less extensive, but that would appear to restrict certain developments. For example, while audio computers are possible, there would be limits on speeds of data transmission. Think modems, but just sending really fast speech, which is decoded back to listenable speed...
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Prior to the advent of audio recordings and the printing press (and, possibly, widespread writing), people already used such a system of recording and passing down knowledge. Oral Storytellers were a prominant position within tribes and cultures.
Similarly, prior to letters, writing consisted of pictures and symbols.
Neither of these prevented a written language from being developed.
Writing is such a powerful tool for storage and recall. When you add the printing press, there is nothing like it for the mass distribution of information until electronic delivery.
Publishing millions of copies of "Common Sense" could not have happened with parrots, or wax, or storytellers, or even prior to the press.
To recap, the written word would not be prevented in such a world, and the traits of such writing would be that of what we have.
[Answer]
**Accountancy**
The invention of written symbols for numbers and lists of who owes what to whom occurred [earlier than 'proper' writing](https://www.accaglobal.com/an/en/member/member/accounting-business/2017/10/insights/cuneiform-writing.html)
Handing the king a some clay tablets or a few scrolls with details of all the supplies his army needs or the tax his barons owe, might be easier or more convenient than giving him a flock of parrots. And as mentioned, in Matthew's answer, perhaps the king wants to keep this information secret, rather then have people overhear it.
Also in the modern world, paper and electronic tickets, permits, passports, work identity badges, shop receipts, bank statements and the like would be faster and more convenient to carry about and read, than to listen to a recording.
**Money**
Civilisations invent currency so you don't have to move your wealth around in the form of cattle, bolts of cloth, and bushels of grain. Early coins have symbols on them to tell you who minted them, and later on coins also state what they are worth. So people will get used to symbols on currency.
**You can see accurately further than you can hear accurately.**
You don't want to have to be within shouting distance of that approaching band of horsemen before you find out if they are House Stark or House Lannister. Flags, banners and other heraldry will again be a form of symbols that humans use. It doesn't take much to start making scrolls/books of heraldry to teach your younglings what all these banners look like.
Meanwhile, you want signs of any kind from *"Danger, black ice on road"* to *"Toilets are that way*" to be distinguishable at a distance.
**Noise pollution**
You're at a railway station. The signs aren't written signs, they are parrots/recordings chattering away.
*Platform 1. Platform 2. Stairs to platform 3 are over there. Escalators and platforms 4 to 6 are this way. Taxis and buses are that way. Fire exit. Staff only. Waiting room. Toilets. Ticket office. Arrivals are blah blah blah. Departures are blah blah blah.*
It would be at best really annoying and at worst deafening.
**Writing works in a power cut**
Unless you are trying to read a book in the pitch dark, visual symbols and signs work when the battery to your ipod has gone flat, the mains power to the public address system has been cut off, and your parrot is grumpy or sick (or dead) and refuses to talk.
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**Yes**, if they are humans regardless of any perfect audio recording, searching system, there **always** will be some form of VISUAL recording.
You seem to miss the point of WHY exactly writing developed and HOW.
Spoken language developed from animal sounds of warning, expressing distress, mating calls, etc. For the given purpose it served, it was perfect. It was instantly produced, could travel long distances and easily understood. It however had an huge limit, it relied on a single sense, hearing.
With increasing number of information to communicate, humans needed ways to better record and express the world around them. The world, perceived by their most used sense, their eyes. All written language originates from some form of symbols and pictures.
You can't communicate an information perceived by one sense through a medium which uses an other effectively and accurately. There will be a lot of miscommunication.
Describing a form, shape, etc. in spoken language will never be the same as showing it. Equations of all kinds, science and engineering in any form is impossible with our limited audio sense.
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**Closing thoughts**: Even cavemen painted pictures of their hunts. Not for recording, but for better understanding.
A maybe better question is, would **a race with much better audio sense than visual** (sentient bats?) and the ability to record it, would develop a written language? That, I'm not so sure.
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**Predictions** about the written language will be dependent on multiple factors:
Society, Environment, Technology levels, History, Intelligence levels... how far from conception it is. The further in time it is, the less they will be like the pictures they are based on, and more of a mirror of their culture and history. Like Chinese characters... they are a fascinating study.
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I'm writing a graphic novel on the premise of a world that has a liquid or semi-liquid atmosphere, separate from a true liquid sea. But since I don't want 'Magical Underwater Adventure!' I've decided (tentatively) on a 'gaseous semi-liquid with non-newtonian-fluid-like physics' - i.e. under low pressure, it takes on more gas-like properties, and vice versa.
(From what I understand a gaseous NN-fluid is technically not possible, because there’s no ‘shearing’ involved… but I'm just looking for something with that particular, similar effect. Because of what I *think* it will result in. And the idea is kind of cool.)
For practical purposes, however, I want it to mostly maintain the visual and chemical characteristics of an Earth-like atmosphere (burnable, breathable, stable, insulates, transparent, etc.) You know. So you can see more than 100 meters or so at most. Also, I want it to be practical to roam around 'normally', run, jump, fall, throw stuff, shoot arrows, etc. Though some fudge is acceptable there.
The ideal is to have a pseudo-sciencey *basis* or maybe *justification* for things, and artistic license can come in after that, for visual/practical purposes. (Considering it's a visual media.)
I'm mainly struggling to visualize the physics and fluid dynamics, though.
More specifically, how it would affect/create weather patterns and phenomenon, climate, and the like.
Beyond that, I'm looking at ecology; and what it might mean for developments of societies.
But I'll probably split those topics off into separate questions, and then link the whole thing together. I've got lots of notes. Any feedback here would be awesome, especially if it helps me reasonably justify or create (or improve!) my ideal.
So I'll just go through what I've kind of worked out / guessed at so far:
1. Basic Physics
* At high pressures, and to some degree cold temperatures, it will become more viscous and dense; and at low pressures, it will become more gaseous and thin. (It could go the other way, but I don't know that it'd create the effect I want.)
* I figure it will be somewhere in-between normal air and water in density, so it will create surface tension with either. i.e. True gasses (*Side-note - where would you notably see these??*) would be slowish bubbles, and water would behave as if in a slightly low-gravity environment, (more 'globby'? Look up water-rag in space videos.) and the gradient between sea and 'air' would be slightly less stark; depending on pressure and temperature, of course. Heavier materials would more or less function the same, except perhaps for large surface-areas and aerodynamic forms.
+ This will also (ideally) create a slip-stream effect easily, so you could run around normally; (or maybe it'd be harder at first, but life would be adapted to that.) but at a certain speed you get crouching-tiger-hidden-dragon type leaps; arrows would travel straighter and longer, provided they don't run into a current; and the like. Also, this may create a more pronounced 'contrail' effect on very quickly moving objects.
* Sound will travel similarly to normal? I don't know. I'd rather this didn't impede the ability to communicate. (Note to self: Google "How does water affect sound-transmission"?)
* It will evaporate at higher temperatures, however, so while burning it will sort of 'boil' and look like a rolling lava lamp of plasma as it cools upward. Think prototypical mushroom explosion. Less heat will be radiated, more light and pressure. (?)
* It will freeze at a lower temperature than water will, instead just becoming more viscous; but it will also make an easier structure (with particles) for water to freeze in midair and on objects; resulting in delicate, near-invisible 'lattices' that fracture with shearing (i.e. weird noises and slightly refracted, broken visual patterns) which will eventually build up to larger ice crystals/object layering.
* It can be saturated with both fresh and salt-water, depending...? Like a saline air. I'd just imagine this would have interesting effects?
* Explosions would oscillate like they do underwater, if more quickly and 'rolling' more vertically; transferring much of the force to pressure-waves rather than to heat. (Owing to cavitation and a wall of pressure-increased density) Although, accelerant explosions may expand in a sort of 'fire-wave', I imagine. (I'd rather the sky medium *not* be a super-accelerant itself, even though it is more dense... though I can see this technically being a byproduct. But I'd prefer not to have a burning-sky apocalypse.)
Before I get into climates and such, I do have a basic states-of-matter question: What, really, is the difference between a gas and a liquid?
I don't feel there is a static line to judge; just relative benchmarks.
The reason I feel this is the case is while you might consider a liquid a fluid because it will (a) take the shape of its container (b) without expanding to fill it completely, like a gas would; this doesn't take into account the effect of *air pressure* on top of it.
Effectively, atmospheric pressure is part of the 'container' keeping it in its current volume. In other words, in a vacuum, water will expand (boil) immediately to fill its container, i.e. fulfilling the second criteria. Also, consider when you 'pour' carbon dioxide (i think?) into a container and it will stay there, allowing for the 'magically extinguishing match!' party trick.
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If you had high pressure (really high pressure, >73 atmospheres) and slightly high temperatures (>30 C), with a carbon dioxide atmosphere (which is feasible), you would get an atmosphere that is made up of [supercritical carbon dioxide](https://en.wikipedia.org/wiki/Supercritical_carbon_dioxide), which is a weird gas-like liquid.
The [atmosphere of Venus](https://en.wikipedia.org/wiki/Supercritical_fluid#Planetary_atmospheres) is supercritical carbon dioxide and nitrogen, while water planets would have possible oceans of supercritical water.
Though I somewhat doubt that people could survive in supercritical carbon dioxide, even with breathing apparatus... plants might evolve to thrive in it, though. [There is a paper discussing the properties of supercritical carbon dioxide and the possibility of alien life in it: (WARNING: pdf)](https://www.mdpi.com/2075-1729/4/3/331/pdf)
ADDED AS AN EDIT: Whoa! I just found out that it is possible for divers to adapt to pressures of 100 atmospheres! So with a protective suit and breathing apparatus (maybe one that can extract oxygen dissolved in the supercritical carbon dioxide -- it readily dissolves water and oxygen) you could hang out in the stuff. And 30C is just in the high 80F.
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One of the biggest differences between a gas and a liquid is density. So actually having basically a much thicker atmosphere, would be more toward living in the water. Sound will travel better farther, but the planet will be darker as more light is absorbed by a larger density of 'air'. arrows would not travel straighter longer, in actuality with more density you get more drag and it would reduce the effective range of all ranged weapons.
It would make a difference on terminal velocity. you would be able to fall farther with less chance of injury because of the friction of the extra density. Which means it would also slow your jumps making them less impressive.
You might also have to be careful of where you sleep, since on a cool fall night a hollow might turn into a pond and drown you!
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A gas, as you say, expands to fill its container -- but it's subject to gravitation, pressure, and escape velocity, which is good if you want a planet to have an atmosphere!
A liquid can be somewhat compressible, but does *not* "expand to fill its container". Boiling doesn't count. If you put water into an evacuated container, it boils and cools until it reaches an equilibrium point. At that point, the container holds *some* liquid water, with water *vapor* (a gas) filling the rest of the container.
Another answer mentioned the critical point and supercritical fluids. If you're working on a story like this, you owe it to yourself to find and read Hal Clement's [Close to Critical](https://en.wikipedia.org/wiki/Close_to_Critical). It's set on a planet whose atmosphere is, well, close to its critical point; several plot points hinge on the strange behaviors of such a fluid.
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I was watching the movie The Martian and I realised afterwards that thanks to its really great CGI, some people think it is based on real story and there are even some who think it was made on Mars.
While both is false, it opens another question: **How to prove you actually landed on Mars?**
Setup:
The year is 2025. After your least favorite candidate for POTUS of 2016 had their 2 terms, a cool guy is elected president in 2024. One of his promises is get us to the Mars. For reals.
Thing is, that 2024's blockbuster movie was completely generated by computers. And about 80% of viewers could not tell that the actors are made up. Even though the movie did cost awful lot of money, it opens lot of conspiracy theories.
You are NASA director. The rocket to Mars is fully tested. Astronauts ready. Probability of mission to Mars success: Over 97 percent.
Even though you communicated all the preparation steps openly to the public, everything is communicated through electronical media. Photoshop version released in 2023 is really easy to use and average home computer can make really great CGI.
How to convince the people that you are actually going to get there physically and walk on Mars by 2026?
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Leave a large reflector on Mars. We left [a specialized retro-reflector](http://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment) on the Moon. It's a special mirror the reflects light back along the path it came. With a strong sensor and laser you can bounce light off of it and measure it. Ahead of time you do it to prove there is no reflector later you do it again to prove there is. So anyone could test and verify its presence, if they had a very strong laser and receiver, because Mars is farther than the Moon.
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**Participatory Public**
The public can (and likely would) be watching the astronauts a lot. Allow them from time-to-time *in a true lottery system* to ask the astronauts to do some fun things, like a backflip or to throw a rock or whatever in Mars' light gravity. You can use CGI, etc. to fake lighter gravity, but you can't do it on the spot. The studio would have as low as 8 minutes (4min each way) of "lag time" only to make the astronaut do something in half-gravity.
**Return Samples - Lots of Them**
Obviously, we can find Earth-based Martian rocks that have entered our atmosphere as meteors. A large volume of return samples can only be collected by people (rovers are delicate things, and would require a lot of energy for just a small sample).
The samples can include regolith, small rocks, etc. that would not have naturally made it through Earth's atmosphere.
Have independent scientists of different backgrounds around the world verify the authenticity of these.
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1) **make something visible from Earth with a telescope on Mars**. A big, round object, kilometers across - it could be just a large white sheet of paper. The windstorms will eventually cover it, but until that happens, any person can just take a telescope and verify you've been to mars himself. According to this post, you would need a 22800 m object, so it's visible as well as the moon with a telescope magnifying 60x:
[How big an object should I build on Earth so that it is visible from space?](https://worldbuilding.stackexchange.com/questions/54952/how-big-an-object-should-i-build-on-earth-so-that-it-is-visible-from-space)
2) (in case #1 doesn't work) **show and explain the technology you have and use(d)**. Why to fake a mission when it's anyway so much easier to do then a CGI, when you have the techno?
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# Consideration
For the sake of argument, please assume the following:
1. The planet in question is around the size of Earth
2. The planet may contain native intelligent life, artificially engineered
3. The planet is artificially constructed
4. The civilization (composed of normal matter) constructing the planet or how they construct one is irrelevant
5. There is an artificial magnetic shield on [the L1 point](http://en.wikipedia.org/wiki/Lagrangian_point#L1) of that planet, made of normal matter, shielding the planet from the local stellar wind (that would cook the planet by continuous matter-antimatter annihilation if the planet wasn't shielded)
6. The magnetic shield only protects the planet within its shadow (the shadow's (magnetic equivalent of an umbra engulfs the planet up to around 1.2 times the radius of the planet), with a little opening that allows sunlight (just sunlight) to pass through the shield and light the planet
7. The planet has a moon, about the size of our Moon, but it is composed of normal matter
8. The civilization constructing the planet (and that put the magnetic shield in-place) is also constructing and operating large arrays of orbital defence system that diverts "normal matter asteroids or comets" from collision with the planet
9. The star, is a normal G class star, comparable to our Sun
# Condition
For the sake of experiences, a very advanced civilization constructed an earth-like planet, complete with local biospheres and native intelligent civilization, with a tech level comparable to Earth at the early age of the space race. They were about to start their first moon landing.
Due to the magnetic shield's presence, they could safely went into low orbit (only when they realize a the large magnetic shield is in-place, without knowing the function of the shield (that said, they don't know what kind of threat were shielded by the shield)), but not to space (they can't go to the moon without magnetic shielding, and ***only find that when they cross region beyond the shield's protection, they'll be cooked with sudden surge of gamma radiations.***
# The public perceives
* The shield protects them from unknown evil forces that will beam up ships from going beyond the protection of the shield, with dangerous levels of gamma radiation
* They know nothing (yet) about matter and antimatter
# The questions
1. What would their scientists postulate about the sudden surge of gamma radiation when they went beyond regions shielded by the magnetic shield?
2. What would they think of the shield and its purpose, scientifically?
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You cannot avoid the problem with space dust if the planet is similar to earth. A nice [article on cosmic dust](http://www.universetoday.com/94392/getting-a-handle-on-how-much-cosmic-dust-hits-earth/) shows a number of aspects of the matter hitting our plant daily. The total mass is expected to be somewhere in the range of 5-300 tons daily - yes the number is not very precise, but at least it gives us the general size of the problem. Even at the minimum 5 tons per day, that is a lot of matter.
The article states: *Particles with diameters greater than about 2 millimeters produce visible “shooting stars,” but most of the mass of dust particles entering the atmosphere is estimated to be much smaller than this, so can be detected only using specialized meteor radars.*
For a 2 mm sphere at an average density of 2.5 g/cm\*\*3 the average mass per particle would be about 0.01 grams and the planet is being bombarded by something like 500,000,000 of these each day. Likely quite a bit more particles as most of the dust is quite a bit smaller than 2mm. Just how perfect do you think your planetary defense system is given the incoming velocities of about 38-248 thousand km/hr and diameter mostly less than 2 mm. 50,000 impacts per day would occur for a 99.99% effective defense.
At 0.01 grams, the incoming particles will have a yields of a 0.5 kt bomb, with a very characteristic radiation signature. Most will be much smaller, but still very easily detected. Furthermore, since most of the cosmic dust will be in the ecliptic plane, there will be a pattern that these events are more common over the equator than the poles (due to the changing angle of incidence). Likewise there will be patterns of heavier activity that correspond to meteor shows. Because of the earth's orbital velocity (30 km/s) around the sun, the number of impacts at the leading edge will be significantly higher than the trailing edge and this will definitely be noticed i.e., the rate at dawn will be higher than at dusk.
The jig will be up long before spaceflight if this anti-earth had the same development history as us. In fact the bright flashes in the sky will make this a very well studied and obvious problem long before spaceflight, though without an understanding of particle physics will be inexplicable. In fact I believe that the light shows would drive an interest in astronomy.
The orbital defense grid needed to be 99.99% effective will be directly observable from the planets surface. You would need large arrays of Hubble-sized telescopes or smaller numbers of more massive telescope facilities for detection. Then you need the defensive equipment and power sources for the actual defense. These will be blatantly obvious to 1950's tech ground based telescopes.
As mentioned by bowlturner, the earth also loses mass -- about 250 tons per day (estimates vary), mostly hydrogen, a little helium and other traces. Some of this will result in noticeable effects from the planets surface too. However, since the bulk of this will be in the form of single atoms and molecules the effect will be much less noticeable than the daily light shows. Once noticed however, there will be an obvious correlation that the effect is a result of something coming from the planet.
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I remembered learning about putting micro-meteoroid detectors in early spacecraft in school and found this [article on the first one launched](http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1958-001A-02). On the Explorer 1 mission launched Feb 1 1958 detected 145 impacts during 11 days for an effective detector area of 0.075 sq. meters. This is 175 impacts per day per sq meter. The detector was designed to detect impacts of 0.01 mm diameter. The surface of the earth is about 510 billion sq. m, so the number of impacts per day is about 90 trillion per day. At a 0.01 mm level, the antimatter explosion would be about the same as a stick of dynamite so I expect quite a few microflashes would be visible in any night sky. An even worse situation for this particular scenario. There are good reasons that astronomers are fairly certain that no large scale antimatter objects exists in the universe.
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For those of you that think a 0.5 kton explosion of TNT is not that large, watch the [video of Operation Sail Hat](https://www.youtube.com/watch?v=ZVM9_attO1Q).
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I forgot about solar wind - but after doing the math, I expect less about 0.28 kg worth of solar wind striking the earth every second - ignoring the effect of earths magnetosphere, but what of course, the solar wind does not ignore the magnetosphere - I would expect the auroras to be supercharged.
I did overlook one other thing when I originally answered the question. As bulk matter the dominant annihilation would be that of proton/anti-proton or neutron/anti-neutron pairs. This type of radiation is not the gamma-ray characteristically produced by electron/positron annihilation that we tend to think of (511 keV). So, the radiation would be even higher energy levels than 511 keV, but the quark annihilations result very short-lived pions that further decay - but this decay also results in neutrinos which carry away over 20% of the original mass-energy meaning that the local explosive effect is somewhat less than expected from 100% mass-energy conversion.
With current satellite technology we do measure cosmic radiation resulting from positrons, anti-hydrogen, and even anti-helium. We do not detect cosmic rays that suggest there is anti-matter source equivalent to a anti-matter mirror-image source of material. I.e, the cosmic rays indicate that the anti-matter striking us is generated by high-energy physics style anti-matter generation, not the result of anti-stars exploding.
I found a [New Scientist article](https://www.newscientist.com/article/dn20274-physicists-create-heaviest-form-of-antimatter-ever-seen/) announcing the first production of anti-helium in 2011. That should indicate how hard it is to produce heavier anti-elements via high-energy physics. The article also mentions the anti-lithium is "beyond the reach of today’s colliders" Even the theoretical Big Bang nucleosynthesis produces only small traces of any element heavier than Lithium (1 part in 1E15), Lithium itself being only 1 part in 1E9.
Making your own anti-matter planet will be a bit of a challenge too - a very advanced civilization that constructed an earth-like planet out of anti-matter would have really gone to a lot of effort as it appears that you have to make your own anti-matter from scratch.
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I think the first problem is that if the magnetic shield didn't cover the entire planet, where ever it wasn't protected annihilation's would be happening bombarding the planet with gamma radiation. Without the shield between the planet and the sun, it would look like a magnesium flare as the planet 'slowly' annihilated away.
However, there is plenty of matter our there and the planet is moving 'across' much of the path of the solar wind. So even if there isn't enough actual gamma radiation to roast the planet, they would be able to detect the shield and it's possible shape from what does react. On top of that the Earth 'loses' mass out into space as it travels, and there would be a 'gamma ray' trail following along behind this planet as anti-hydrogen are left behind and annihilated.
The first craft they send out past the protection of the shield is going to be a large bright fireball as the solar wind immediately starts to to interact with the antimatter of the vessel/probe (this is partly because the 'shield' will be concentrating the matter in the solar wind as a boat hull pushes water into a wave as it travels through the medium) . I am not sure how much mass is in the solar wind but considering how much energy a few grams of interaction can cause, it is possible that it could cause lethal levels of radiation in it's line of site and and possibly other electromagnetic disturbances.
>
> one gram of antimatter annihilating with one gram of matter produces 180 [terajoules](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=terajoule), the equivalent of [42.96 kilotons of TNT (approximately 3 times the bomb dropped on Hiroshima](https://en.wikipedia.org/wiki/Antimatter_weapon#Acquiring_and_storing_antimatter) - and as such enough to power an average city for an extensive amount of time)
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The magnetic field needs to be a good amount stronger than Earth's to keep out the antimatter, so it doesn't annihilate upon impact with the atmosphere and bombard the surface with gamma rays. The people will believe that the gods created a barrier around the planet, to protect them from the "evil demons" that burn and mutate anything and everything. As for the scientists, they'll be a point where they realize that they need a powerful magnetic shield to take people safely into space. Don't know when, but there will be the theory, and there will be the test runs.
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You actually have a fundamental flaw in the shield.
Passage of light is in the form of normal photons being absorbed by “antimatter” matter of the planet.
Essentially the sun side of the planet is being cooked by the star continuously for the entire day,
Then it is cooked by the reflected light from the moon and the incident star light.
The entire surface of the planet would be radioactively un-inhabitable
The amount of solar energy hitting the plant is approximately equal to 20,000 times the current consumption of the entire human race.
This planet would literally be hell on earth.
As a consequence of this, plants would not be able to convert solar energy into food, as well as all exposed flesh of any animal would literally be destroyed in the resulting antimatter/matter annihilation taking place, so there is no food, and you’re cooked in your own skin.
<https://en.wikipedia.org/wiki/Absorption_(electromagnetic_radiation)http://www.ecoworld.com/energy-fuels/how-much-solar-energy-hits-earth.html>
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Would a salt flat be near a river?
I have a world with a Nile River-like region and within a few miles, perhaps 10-20, I have a massive salt flat. The arable land of the river brushes up against eastern edge of the salt flat but all the other "borders" are surrounded by a Sahara-like desert. Is this realistic?
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Salt flats are generally formed where ancient oceans, seas or even lakes have become cut off and water can only evaporate out of them. The Dead Sea is a current example, as is Great Salt Lake in Utah.
So sometime in the past, your river might have drained into a low lying area without access to the sea and the waters evaporated away, leaving the salt beds. At some more recent time in geological history, an earthquake or other geological change changed the course of the river, opening a channel to the sea.
Alternatively, the sea itself could have had an arm leading into the region which was cut off from the rest of the sea due to some geological event, eventually leaving great salt flats as the water evaporated away (which would be of greater extent and depth than those left by a more recent salt lake). The river's path could have moved closer to the salt flat over the ages, so its position today is a fortunate coincidence. A thousand years from now, the river could actually be running through the salt flat, washing the salt back into the sea.
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There are salt flat regions near the Nile itself. Perhaps the largest is the [Qattara Depression](https://en.wikipedia.org/wiki/Qattara_Depression).
The [great bitter lake](http://earthobservatory.nasa.gov/IOTD/view.php?id=40884), now flooded with seawater as part of the Suez Canal, was once a salt flat. During the building of the Suez Canal, a small parallel canal called the Sweetwater Canal was built to supply fresh water to the area. The water came from the Nile via Lake Timsah.
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If the surface evaporation rate is high enough then yes, look at field salting in California, the river could supply the salt directly in a sandy environment or simply supply the moisture to wick salt from deeper deposits.
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As has been covered in other answers - salt flats are generally in depressions. This makes the situation where very slightly salty river water goes in, but never out, likely.
Whilst less likely, a salt and sulfur rich crater lake could have been made in a old caldera. Hot springs push the hot brine to the surface where they dried mostly before making it back to the nearby river. Doesn't quite fit your narrative though.
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In my world there was a sentient being who was able to witness the evolution of life on the planet for a few million years. He watched as human beings evolved from monkeys. This knowledge may not be widely known, except among a few scholars, but I wonder what implications that this knowledge might have on a magical world at a roughly medieval tech level, if any at all.
Also in my world evolution and creationism are not mutually exclusive. Throughout the world's history the gods have acted as bioengineers and probably seeded the world with life. While humans evolved naturally a number of intelligent species were created.
Obviously the impacts would be culturally relative, but my world has a very wide range of cultures so I am thinking in broad general terms. Some cultures may be completely unaware of evolution while it may be common knowledge in others.
How might knowledge of evolutionary theory impact this medieval society?
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**Improved Plant and Animal Breeding**
People have been domesticating and breeding animals for ages. Putting that on a better scientific basis should increase the effect. Even without genetic manipulation and hormone treatments, present-day milk production per cow greatly exceeds medieval levels. Of course it helps that modern cows get plentiful food.
That brings us to plants. Modern breeds have germination rates far in excess of historical breeds, and even without pesticides they should bring far higher yields.
All this was an ongoing process since the dawn of civilization. Evolutionary theory will accelerate it.
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**Not much would change, on the whole.**
This might seem a bit boring, and it's all my opinion. Discussion welcome.
Cultures all around our world can be said to have had a fair idea of genealogy at different times, even without genetics. Humans have domesticated dogs, horses, corn, and who knows what else, all by observing phenotypes (look it up, I can't post 3 links).
In humans themselves, Western cultures had the royalty and nobility who were assumed to be "better" in some way, and the [caste](http://psychology.wikia.com/wiki/Caste_system) system of Hindu fame comes to mind. With scientific methodology to quantify certain desirable traits, there's the possibility that evolutionarily ideal people would find themselves in the top rungs of society. Ideal being a relative term. These people would, for the sake of the future, be allowed somewhat loosened ideas on reproductive morality. People who were deemed to have no positive contributions to the gene pool would be allowed to starve, or at least have to support those with uncommon genes for the greater good.
You might see the evolutionarily "better" ruling class be deposed by peasants who would rather live better today than let somebody else's offspring be the wave of the future for their country. The [French Revolution in the 18th century](https://en.wikipedia.org/wiki/French_revolution) comes to mind as being very similar to how that scenario might play out in your world.
I'd like to mention the "society of supermen" scenario from Star Trek (NG, redone in a recent movie). That is the most significant possibility I could imagine this enabling.
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Eugenics is a social philosophy that was popular in the US and Europe in the first half of the 20th century. The movement’s goal was to improve the quality of the human race by applying the same techniques used in animal and plant breeding to humans. Essentially, by encouraging the reproduction of humans with good traits, and discouraging the reproduction of humans with bad traits the good traits will become more prevalent over the bad traits. This movement quickly followed the popularization of Darwin’s evolutionary theory. Many countries, and some US states, introduced eugenics programs which involved the forced sterilization of people deemed unworthy to reproduce. The movement ended somewhat abruptly after World War 2 when the Nazi’s use of eugenic concepts in the Holocaust made the ideas unpopular.
Eugenics requires an understanding of biological inheritance that a theory of evolution provides It seems possible to me, that selectively breeding human populations for desired traits could become popular among the Medieval aristocracy. The royalty own the land and the serfs that lived on and work the land. Their descendants will own the same land and the descendants of those same serfs. It only seems natural that a land-owner would want to improve the quality of the serfs that work their land.
Another philosophy that emerged due to Darwin’s theories was Social Darwinism. Social Darwinists think natural selection is applicable to individuals in human society. They believe that inequalities in society are natural and are the result of superior individuals triumphing over inferior ones. Medieval societies were for the most part, extremely unequal. Concepts from Social Darwinism could be used as additional justifications for the existence of royalty and reinforce the idea that the king’s rightful place was at the throne while the peasants rightful place was in the hovel.
Of course these ideas are a product of their time, and wouldn't necessarily follow just from an understanding of human evolution, but I think these are potentially interesting for your world.
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Well, surprisingly they did have a poor understanding of evolution. They knew about animal husbandry and knew how to get good stock from good stock.
They also believed that the people where in the class they were in by breeding (mixed with divine intervention). Kings were the 'best' and most worthy stock with their royal relatives, and were followed by the nobility etc, etc. KNOWING about evolution, would have likely strengthened their notions of separation from the lower classes. Might even have encouraged nobles to 'breed' with more of their peasant women to 'get a higher quality' serf, (or at least use it as another excuse to poke all the pretty lasses).
But I don't see it doing much more than that.
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As o.m. has said, the effect of earlier knowledge of evolution on agriculture would be to make improvements in agriculture more scientific and hence more successful. This in turn would give a society the ability to feed a large population at an earlier level of general technology, compared to our world. Expect an initial increase in instability, as kings and rulers no longer have the size of their armies limited by the ability to feed them. The age of great conquerors like Napoleon with mass armies comes earlier than in our world.
Hopefully this would eventually be followed by a more comfortable era in which wars and discontents caused by famine are a thing of the past.
The political and cultural effects of an earlier understanding of evolution might not be wholly benign. In our world attempts to derive a moral ethos from "survival of the fittest" have often stressed ruthless competition and ideas of the "highly evolved" races suppressing or even exterminating the "lesser" races or species. (I would like to add that in my opinion any attempt to get from "is" to "ought" is philosophically meaningless, but plenty of people disagree.)
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It would probably have the same impact that it had on society in the 19th century, a boom of scientific thought and learning.
The thing that made Medieval times known as the "Dark Ages" was the blanket ban on any pursuit of knowledge that challenged the Church. All the great thinkers of the Dark Ages were branded as heretics, blasphemers, or devils and burnt at the stake, which stunted the progression of the human race for a thousand years.
If a medieval society was open to such concepts as evolution, that means that they are not closed to new ideas, or free forms of thinking. Had the medieval earthlings been as open minded, we would probably be a thousand years more advanced than we are right now.
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Scenario:
A major stock holder in the stack exchange group is a survivalist. And he is fearfull of a zombie outbreak and apocalipse. He has a lot of money to spare. He intends to store a certain ammount of food, water and weapons to survive thru the zombie outbreak. He will store dehydrated food for as much as 2 years worth of food. He has a large water storage system capable of recycling water via reverse osmosis. Other basic items are already stored. He will invite ten of his friends (males and females) to stay and fight besides him.
Question:
What weapons should they carry ? Both cold metal and gun type weapons, divided into four categories: Close combat range (0 meters), short range (3m to 15m), medium range (15m to 100m) and long range (100m to 1km) should be carried. How many of each ? How to distribute this into the squad ?
He wants to build armour. But not a medieval one. He wants one designed specifically to survive the zombie outbreak. The armour might use metals, carbon fiber, kevlar, situational awareness raising eletronic items etc. Radar etc, like Ironman (without flying). What can he build with todays tech ?
Assume:
There is no money limit, he is one of the owners of stack exchange or similar popular sites. There is no knowledge limit, he can understand fundamental scientifical principles applied to the task at hand. He is single. His parents are already dead. No child. Zombies are of the virus disease type. Zombies are still alive but their reasoning is damaged by the virus. Virus is a mutation of the rabies virus that spreads like flu virus. Their saliva is the usual transmission method. Incubation time is quick, one or two days and the person is turned into a zombie. The disease attacks the control of emotions and makes a person irrationally violent. Already turned zombies release a strong odour that discourage other zombies from attacking them. Zombies do not eat brains or flesh, they are just hyper-violent, like a rabid dog. Zombies attack via punchs, kicks, bites etc. Biting zombies transmit the virus to other persons bloodstream directly. Assume he started preparing two years before the outbreak. Animals do not get the disease. Zombies are plain simple humans with a brain virus. They do eat, but they dont have a sense of taste, so anything that is food can be eaten by them. Any kind of human fluid is able to transmit the disease. This is a zombie killing squad, prepared from before the outbreak to do its job. A professional zombie killing squad without money limits. They must search cities to save people trapped inside buildings. They are prepared for something that the military and the state is not prepared.
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# Context Is Everything
Your question all depends on where the zombie-killing squad is going. Are they fighting in open areas, or areas with tight spaces? Urban, suburban, or open-field combat? In each situation, different types of weapons excel over others.
Let's look at some good options. (Points not cited come from my martial arts experience, which includes HEMA.)
# Close Combat (<3 meters)
* Medieval Weapons work well here. There is no ammo to run out of, and they're really good at dismembering and killing. Across most cultures, spears and other pole arm weapons [were king of battlefield deployments](http://en.wikipedia.org/wiki/Pole_weapon) for a long time. Users of pole-arm weapons benefit from striking their opponents before they strike back, and they are also good at deterring charges. Halberds, on the short end of the pole-arm spectrum, can be used in very close combat as well as at wider measures. Buckler and sword were common and effective in melee.
* [Riot Control Gear](http://en.wikipedia.org/wiki/Riot_control) would work well, too. The sticks and shield walls are effective at preventing the policemen from getting beat up. If zombies can be deterred like modern crowds, this equipment will work really well. If not, the riot control gear will need to change to deadly force, ignoring things like pepper spray. Pistols, knives, and clubs can be used.
* Handguns can be used in close quarters, but do not provide the protection that these other weapons/weapon systems do. (You cannot easily parry a punch with a handgun, or prevent someone from falling on you.)
# Mid Range (3 - 15 meters)
At this range, ammo is important. This goes for every weapon used, be it a gun, crossbow, or even boomerang. (I don't suggest a boomerang against zombies.)
* [Shotguns](http://en.wikipedia.org/wiki/Shotgun#Law_enforcement). Even if your aim is a little off, most shotguns will have a tight enough grouping that you will hit your target anyways.
* [Handguns](http://en.wikipedia.org/wiki/Handgun) are used well in this range. Additionally, the free hand can be used to open doors, manipulate buttons, etc. This is helpful in urban environments, where opening doors or pressing buttons happens often. Ideally, every solder in the zombie-killing squad would have a handgun as a sidearm.
* [Sub-machine guns](http://en.wikipedia.org/wiki/Machine_gun), the hand-held version of machine guns, work well in this range.
* [Crossbows](http://en.wikipedia.org/wiki/Crossbow) or Bows. These zombies are not armored, so the penetrating power of a crossbow may be wasted. The speed of an archer with a regular or [compound](http://en.wikipedia.org/wiki/Compound_bow) bow may be more valuable. Crossbow and bows are good because they are very quiet, especially compared to guns, and the bolts or arrows have the potential for re-use, whereas bullets may be harder to recycle.
# Medium Range (15 - 100 meters)
* Crossbows are still an option.
* Rifles, being more accurate than shotguns or pistols, would be ideal at this range. Unless the rifle is automatic, you would need several people shooting at this range to stop a mob of zombies.
* [Machine guns](http://en.wikipedia.org/wiki/Light_machine_gun), with their high rate of fire, can mow down mobs of zombies really quickly.
# Long Range (>100 meters)
* Light Machine Guns, like the [Lewis gun](http://en.wikipedia.org/wiki/Lewis_gun), have an effective range of up to 800m! A skilled operator could, in theory, hit things up to 3 km away!
* Rifles shoot this far, too. Scopes would be helpful.
# Armor
Zombies appear to punch and bite. You therefore need only protect against bites, punches, and kicks.
* [Shark Suits](http://en.wikipedia.org/wiki/Shark_suit) are chainmail, and they protect people from shark bites. [Shark bites](http://www.discovery.com/tv-shows/shark-week/videos/sharks-vs-chainmail-suits/) are much more damaging than human bites.
* Riot Gear, as mentioned earlier, can work well. Armor from riot gear is to protect individuals from melee assaults, which is the main method of your zombies attacking people.
* Thick plastic + padding may even be enough to prevent people from breaking skin, and therefore prevent zombification of friends. This is essentially a modified/updated [gambeson](http://en.wikipedia.org/wiki/Gambeson).
# The Recommendations
For Urban Combat:
* Give everyone a [hand-and-a-half sword](http://www.coldsteel.com/Product/88HNH/HAND-AND-A-HALF_SWORD.aspx) or [arming sword](http://en.wikipedia.org/wiki/Arming_sword) and buckler and a pistol.
* Give everyone armor, at least the updated gambeson and helmet.
* Give one or two people a riot shield to act as point guard.
* 1 Person with a sub machine gun or automatic rifle.
Tight spaces require smaller weapons. Many choke points mean less people are able to shoot, so go lighter on the guns. Additionally, your bladed weapons are more quiet, so sneaking becomes an option. Guys with big riot shields in front/back, to hold choke points while others do the actual killing.
For Suburban combat:
* Everyone gets a pistol, and armor. At least the modified gambeson.
* Pole-arms will likely have enough room to be effective. I suggest giving at least 5 of the people pole-arms.
* The other 5 get sub-machine guns or auto rifles. If these are unavailable, use compound bows.
Suburban combat has some tight corners, but mostly open spaces. Hence the pole-arms and more automatic weapons. More guns and ranged weapons mean more chances to safely use ranged weapons. People with pole-arms protect those with guns, who ideally do most of the killing.
For Open Spaces (country):
* Everyone gets armor and a pistol
* A rifle, machine gun, or other projectiles launcher for everyone.
It's open, so hit the zombies at range and keep them at range. If they're coming for you, *run to safety*.
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Since the zombies are legion and you are just ten, the best way to fight the zombies would be to recreate the sort of conditions which allowed the British to hold Rorke's Drift with only 150 troops against 3-4000 Zulus. You already have the basic conditions with the survivalist base, so fortified with high walls and various obstacles in the front to prevent the zombies from simply walking in is a good start.
Long range weapons would start with military rifles, since single, well aimed shots will kill or disable the zombies you describe at long range (a trained rifleman should be able to deliver lethal effects at 600m with a properly sighted in rifle). I would suggest bolt action rifles like the Lee Enfield since it is rugged, fires a large caliber bullet and is inherently accurate enough to do the job. Smaller calibre weapons like the modern M-16/M-4 series are accurate, but might not have the "knock down" effect at long range like larger calibre rifles. (The Lee Enfield is mentioned because it is a personal favourite, but a Springfield 03, Mauser or any similar rifle will do).
Coming into closer range, the rifle is still quite lethal, and some bolt and lever action rifles can deliver a high rate of fire if needed. I am staying away from more modern semi or full automatic rifles since you want to conserve ammunition and are in no condition to deal with a jam or misfeed at this point. Shotguns are also useful here (although once again I would suggest a WWI era "Trench Broom"- the Winchester Model 1897.
If you are wonder about the emphasis on WWI era weapons, this become clear as we reach the close fight. Large calibre pistols like the Webley-Fosbery Automatic Revolver or M-1911 .45 ACP pistol will ensure any zombie hit will go down and stay down, while WWI era rifles and the Trench Broom are fitted for bayonets. The long "Sword" bayonets common in the early war period provide extended reach , and turn the long arms into pikes or spears. If you are into a melee, the long arms themselves become very effective clubs.
Personal body armour can be as simple as a set of motorcycle leathers, since they provide freedom of movement and action while firing rifles and pistols, or using bayonets, while protecting the wearer from bites and scratches. Some sort of facial protection would be needed when up close to prevent infection from blood splatter as well: a full visor motorcycle helmet might suffice at this point with the visor locked down.
The key would be to work in fire teams, so an individual would not become incapacitated from the heat build up inside the leathers, so one person could fight while the other covers, then move in to relive their partner.
Unless the survivalists have extensive training and practice, I would probably avoid swords or pole arms; they require a great deal of training to use effectively, and it is actually quite easy to hurt yourself with a sword or pole arm if you are not proficient in its use.
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As weaponry i would suggest a good pistol each, assault rifles for most and one or two sniper rifles, maybe a shotgun.
Additionally, each member of your squad should carry a machete, for the nasty situations when the zeds get much closer than desirable.
Most of all, one member of your squad should carry a flamethrower. Not only are they very handy for cleaning out rooms in buildings quickly, they also work like a charm as an instant disinfectant...
As armour i would recommend full-body motorcycle suits. They are light, durable, will easily hold off bites and scratches, provide quite some added protection around elbows, back, knees etc to fend off some attacks as well as absorb shocks from heavy landings. Standard military boots should go without saying.
A light helmet (the modern kevlar stuff, military edition), and a bandanna to cover mouth and nose, holding off at least most spraying body fluids.
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Since these zombies are "rabid" I would assume you can easily attract them by pissing them off with high pitched noises or other distractions. Get yourself an army of drones. Coordinate them to fly through the city attracting the zombies as they go until they reach a central point outside the city. Proceed to blow them up with pre placed explosives. I would assume with unlimited money it would not be hard to create an mobile zombie proof command base you can park outside city limits to control your drones.
Any weapons they bring would be fully situational to the environment they are going to. As for armor I would go with a bio suit riot gear combo. If any bodily fluids can transmit the disease you will want to be very careful that nothing gets on you while your bashing your way through any left of zombies who may of not been able to leave the city during your initial drone flyovers. It may even be useful to bring along a portable decontamination room to wash off any guts before you undress from the gear.
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I am interested in the actual physical steps such a regime would take, e.g. cutting the submarine telecommunications cables. How might such a regime destroy the mobile phone network? What would it need to do to put communications satellites out of action? What else would it need to do?
Does it need to destroy local infrastructure (e.g. phone masts & internet servers) as well, or can it leave all that to rust once the big stuff is taken out?
Assume the regime controls the whole world with only scattered resistance. It is quite willing to use modern technology itself while in the process of transition. While tyrannical, the regime is not genocidal and would seek to minimize the suffering this forced regression would involve.
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Jam the hell out of all frequencies. Install nuclear power plants and connect those to large transmitters targetting all commonly used communication frequencies. Your government will usually not cut submarine cables, instead, it will secure all large scale communication devices to itself. Submarine cables are easy to control access to due to their know and imovable physical location. Wireless communication on the other hand, must be dealt with using jammers. High powered high tech jammers can block even GPS signals. Its incredible how modern tech is sensitive to intentional jamming. Take 2.4GHz WiFi as example. If you put as little as 1W of power in a omnidirecional antenna you can block almost all channels in a large radius. 802.11abn protocols cannot distinguish jamming from real channel use, so they back-off from transmitting.
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I think it would be a lot easier than you expect. And a lot less destructive. Just ban it.
Mobile phone networks and the internet are very large scale operations. If the regime is world wide and has considerable might, all it has to do is ban them. Ban the manufacture and possession of cell phones. Have the towers taken down. Shut down the centers that control the satellites. Shut down the data centers that power the internet (you don't have a DSL connection if the phone company's router is unplugged). Ban the manufacture of modern computers (or restrict who can buy them). You can't slap together an Intel i7 chip in a garage, you need a specialized fabrication plant to create them. Prevent large scale production and you'll greatly hamper the technology.
Would there be resistance? Sure. But most people will not be willing to risk jail or worse by keeping local cell phone service running.
The most interesting thing to me would then be how the resistance manages to use un-confiscated equipment to facilitate communications without being detected. What can you do with a thousand cheap wifi routers? How do you mask their use?
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I wonder why they would want to "destroy" the communications infrastructure when it would be much more efficient to use many of the methods leaked by Edward Snowdon to simply monitor communications and then take action against the people or groups who represent some sort of threat?
A cruder example would be the "Great Firewall of China", which seeks to block most internet traffic from outside of China from reaching unauthorized (i.e. anyone not in government or military intelligence) users. Iran is also attempting to do something similar by creating an isolated "internet" which only serves those inside Iranian territory.
Even unregulated Internet does not have to be an issue for a ruthless enough regime. During the Arab Spring, Egyptian Police started inhabiting chat rooms and infiltrating social media groups; often directing groups of protesters to meet at a predesignated time and location, where (surprise) the police riot squad was already assembled. While Snowdon did not reveal any examples of how the American or Western governments use their powers, it is probably more subtle, for example targeting the tax agencies to perform hostile audits on perceived political opponents, or using regulatory and legal harassment to hobble the ability of people to accomplish their goals.
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This could be done without destroying infrastructure in a few easy steps:
1. Drop a lot of malicious software on the net.
2. Deliberately reduce bandwidth.
* Slow the pace of networks back to the dial-up era. Remember AOL in the 90's?
3. Taxes. Make the use of internet, satellite, and cellphones prohibitively expensive.
* If you were one of the lucky few who could afford to stay online, you would find a dramatically reduced web, most sites and users would drop off overnight.
4. Set up a large cumbersome bureaucracy to collect communications tax.
* Those who can afford to pay the prohibitive tax will be less likely to do so if forced to navigate through mountains of deliberately convoluted paperwork.
5. When citizens complain about steps 1, 2, 3, and 4
* Blame the malicious software on rebel forces
* Claim slower connections are due to malicious software
* Explain that higher taxes are used to remove malicious software and deter further rebel infiltration of networks.
* Blame bureaucracy on bureaucracy. Sounds circular, I know, but that's bureaucracy for you. Can't fight city hall n' all that...
+ You'd be surprised how many people will just accept that government is inefficient because government is inefficient.
6. Profit.
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In the 1700s, revolutions were organized with "Committees of Correspondence." So it doesn't take cell phones, just paper and ink.
Transoceanic cables are 1800's.
They don't need to destroy everything, just sequester it to their own use.
Cell phone service is erratic enough now that they could make plausible a collapse of the systems through overload. Turn in your cell phone for a reliable landline. Have medical studies show that those rooftop repeaters are responsible for the increase in childhood disorders like autism and ADHD. Save our children! Ban cell phones! Tear out those repeaters!
They will have to restore landlines, preferably as pre-multi-freqing systems where operators control long distance. The return of telegraphs and codes?
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Getting rid of public communications infrastructure would be quite easy. Just use your might to get rid of the ISPs and force the telcos to only use landline phones and, other than the phones, you basically don't have any modern communications systems your average joe can use anymore. Well, other than CB radio, that started in 1945, but anyway...
The challenge would be in removing HAM and CB radio operators with modern equipment. I don't think you can actually do that. I don't know of anyway you can detect the type of equipment somebody is transmitting with, other then that tube amplifiers and solid state amps have different overdrive/clipping characteristics, but I don't know if that would ever really be detectable during normal operations.
Actually, reading your question again, it seems like you didn't consider that there are people who privately own transmitters and communicate with each other with them, and did so even in the mid 20th, or even late 19th century.
For a scattered resistance, using mid 20th century radio tech would be just fine. The biggest changes in modern communications technology have been bandwidth and carrying capacity and for coordinating a resistance you don't need much of either of these things.
There really is no effective way to prevent electronic communications though. The bar to entry of radio is really just money. There's no special factory or manufacturing technique you need, just give your average Electrical Engineering grad $5000 and they can make you a high power transmitter from off the shelf components.
It would be easy to find somebody who was transmitting (though their might be some stenographic techniques you could use to hide in background noise or authorized communications), but if they need to send one or two messages, that might be enough and with cryptography you wouldn't even know what they were saying.
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First, if it has an army, it can break down cell phone towers. If it is really a word power, it has a space program. It can destroy communication satellites.
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So I have a liquid that absorbs light, and then releases it when impacted/surface tension broken.
I'm debating on if I should just follow Sanderson’s First Law of Magics:
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> An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic.
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and Arthur C. Clarke's law:
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and just not bother explaining it. Or if there is some way that it could be possible without using 'magic'.
While having fantastic elements, I'd like it to be at least scientifically plausible.
A few possibilities I can see:
1. The liquid slows light down to a crawl/stop
2. The liquid refracts the light infinitely so that it can't escape
3. The liquid's surface tension has some property where light can pass through from the ouside, but reflects from the inside. Like an infinity mirror.
**EDIT:**
The technology level is quite a bit beyond where we are at. Things like replacing cells with artificial cells made of nanobots, room temperature superconductors, brain/machine interfaces, interdimensional travel using wormholes or something similar are all possible. There are a few entities that are effectively post singularity.
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The molecules of the liquid are naturally in a crystalline matrix that perfectly reflects photons within it, trapping them. When the liquid is shocked or the surface is disrupted, the crystalline matrix loses its symmetry and the photons shoot out in all directions.
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What you're describing sounds something like a [Bose-Einstein condensate](http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate). Basically think of cooling photons (light particles) to a point very close to absolute zero. It seems like this is more like a gas than a liquid, but with adding some of the element of handwavium, it could work for your purposes.
Also, take a look at [this article](http://news.bbc.co.uk/2/hi/science/nature/3308109.stm):
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> However, in this latest study, researchers switched on two control beams which created an interference pattern that behaves like a stack of mirrors.
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> As the regenerated signal pulse tries to continue on its way through the glass cylinder, the photons bounce back and forth, but the overall signal pulse remains stationary. The light beam was essentially frozen.
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Your liquid could be some form of this substance.
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First of all, your three explanations don't work (EDIT: very well).
* Light slowing down inside the liquid. This might be plausible, but then you will have a difficult time trying to explain why the liquid allows light to escape upon interaction. Slowing down light introduces some bad complexity, like what frequency will the light be when it is "freed"? The same as when it entered? This would be very difficult to explain.
* Refracting/Reflecting light infinitely. EDIT: OK, maybe this is technically possible. But the technical implementation would require such a level of precision and complexity (especially considering the fluid aspect) that it's completely impractical.
The answer is easy. These are tiny bacteria-like organisms floating around in some fluid. These organisms can either be alien or engineered, it doesn't really matter.
* Nano particles can be very small. Try not to think of these as "little robots", they can be more like tiny bacteria with engineered traits.
* You know about fireflies right? Same concept. Light can be stored by chemicals in vacuoles, and photosynthesis could be a viable mechanism for producing the energy required to create the proteins necessary for engineering these light-producing chemicals. They could also be living off heat, bugs that fall into the sticky goop, or whatever.
* If going down the "alien lifeform" path, you could easily say that the flash of light is a defense mechanism to scare off animals who might consider eating the fluid. For the engineered path, it really depends on your storyline. It could be a military weapon of some sort (to prevent ground troops from sneaking at night), a practical joke (the Flash Goop, Inc factory had a leak).
* Scientists today have been playing with the genes necessary for engineering these organisms. There's even a [startup where you can pre-order glow-in-the-dark plants](http://www.glowingplant.com/).
* It would certainly flow like water. The engineered bacteria may be suspended in some other liquid, the properties of which you are free to define (viscosity, flammability, etc).
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I would say that it just stores energy, it keeps trying to collect it but it has a trigger to release it. Have you ever seen a Supersaturated liquid? They use them in mitten warmers and [heating pads](https://bsclarified.wordpress.com/2011/12/26/science-thatll-warm-your-hands/), a physical shock will set it off, and it releases heat into its surroundings. Instead of heat it could be light!
Being able to control the reaction would make it more useful.
edt: to replace super cooled with supersatureated, since that was correct terminology. Supercooling can have a similar reaction, where when it 'freezes' it gives off extra heat to crystallize.
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There are several very good scientific answers. However, another point of view would be to read the interaction of Sanderson's First Law and Clarke's law slightly differently. What if we use Clarke's law to substitute "sufficiently advanced technology" for "magic"
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> Sanderson-Clarke's law of technology: An author’s ability to solve
> conflict with sufficiently advanced technology is DIRECTLY
> PROPORTIONAL to how well the reader understands said sufficiently
> advanced technology.
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I think the approach used here of trying to find a scientific rationale for why it works is useful. Science is a *great* way to give readers an understanding. However, while you are putting your story together, remember that you are free to augment such scientific explanations with other ways to encourage understanding (such as looking at how the characters react to the technology).
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
I have a story where a species of the very first (literally first) carbon-based humanoid life (surprise!) that happen to emerge roughly seven billion years ago (their home system were formed twelve billion years ago).
Assuming that it's possible that a star with age of around twelve billion years has a system of rocky planets orbiting it ([here is the proof](http://www.slate.com/blogs/bad_astronomy/2015/01/27/exoplanets_five_extremely_old_planets_found_around_kepler_444.html)), and considering that even ancient galaxies could have similar dust-to-gas ratios as normal "mature" galaxies (just like ours), despite the fact that it was predicted to have lower metal compositions..,
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> The team’s expectation was that A1689-zD1 would be a more primitive, metal-poor galaxy given its early stage of development. In much the same way that life on Earth began with limited ingredients and evolved into more complex forms, each stellar generation forges elements heavier than hydrogen and helium, which form the building blocks of the following generation. Accordingly, the universe’s very first batch of galaxies is supposed to be pretty basic.
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As stated in this [page](http://motherboard.vice.com/read/the-puzzling-galaxy-at-the-edge-of-time-and-space-3252351).
The problem is, I just realized that the cosmic background radiation was hotter and more energetic than the way it is now, dating back to 378,000 years after the Big Bang.
Is it possible that at the time, cosmic background radiation is in the visible portion of the electromagnetic spectrum? How warm is space at this time?
To narrow down the possibilities, I require a calculation (for those who are kind enough to work on the math) of how the cosmic background radiation would look like (at which light wavelength, and background temperatures) at this time range:
Twelve billion years ago (the moment that star I mentioned formed) up to seven billion years ago (the moment those carbon-based humanoid species emerge).
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Depending on just how far back you go, there was a time the CMB was in the visible spectrum. However, in the era you're talking about, this is not the case, and compared to starlight and the primary's light, it's going to be far too isotropic (and probably dim) to notice.
According to [this very apropos article](http://www.space.com/24496-universe-alien-life-habitability-big-bang.html) quoting Harvard astrophysicist Abraham Loeb: "When the universe was 15 million years old, the cosmic microwave background had a temperature of a warm summer day on Earth." This means that 15 million years after the Big Bang, the CMB radiation had **already** been shifted all the way to the infrared.
Let's bring in some numbers. Fortunately, despite a [long layer of calculations](http://www.cv.nrao.edu/course/astr534/CMB.html) to get there, the CMB temperature calculations follow a simple formula:
$$T=T\_0(1+z)$$
where $T$ and $T\_0=2.725K$ are temperatures and $z$ is the redshift, itself a linear function of the scale size parameter $a$. To get your age range, use $z$ values between 4 (~12 Gyr) and 0.66 (~7Gyr). Or you could simply use a [z redshift calculator](http://home.fnal.gov/~gnedin/cc/). Or if you're lazy, use the figures I've stolen from [Carmeli, Hartnett, and Oliveira, 2005](http://arxiv.org/pdf/gr-qc/0506079v2.pdf)
As you can tell by the formula, unless you get within a few million years of the hypothesized Big Bang, your final T values will be in the 13K - 4K range, so not hugely warmer than today's.
We can conclude that in the era you're talking about (7-12 billion years ago), **you're far enough removed from the 'Big Bang'-event that the CMB would only make a minor contribution.**
Given the much, much higher gas densities of the era, I'd be **far, far more worried about getting blasted apart by the numerous supernovas popping all over the place**, and black hole radiation blasts from the super-massive central black hole and actively feeding nearby black holes. Each of these might be sufficient on its own to sterilize areas ranging from dozens of light years for a supernova to perhaps a whole galaxy for the central super-massive. Plus rare events like a triple neutron star collision, etc.
[The Loeb 2014 paper can be found here.](http://arxiv.org/pdf/1312.0613v3.pdf)
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[Gawiser & Silk (2000)](http://arxiv.org/pdf/astro-ph/0002044v1.pdf) provide a nice overview of the CMB (possibly better than [Wikipedia](https://en.wikipedia.org/wiki/Cosmic_microwave_background)). The paper is a bit outdated - after all, they use a figure of 15 billion years as the age of the universe! - but the rest of the information conforms with recent measurements . . . sort of. They give the date of [recombination](https://en.wikipedia.org/wiki/Recombination_(cosmology)) as 300,000 years after the Big Bang. A paper by the [WMAP](https://en.wikipedia.org/wiki/Wilkinson_Microwave_Anisotropy_Probe) team (website [here](http://map.gsfc.nasa.gov/)), [Komatsu et. al. (2008)](http://arxiv.org/pdf/0803.0547v2.pdf), for example, covering the first five years of data, gives the age of the universe as ~137.72 billion years. The date of recombination has also been pushed forward to about 378,000 years, thanks in part to data from [Planck](https://en.wikipedia.org/wiki/Planck_(spacecraft)) ([Ade et al. (2013)](http://arxiv.org/pdf/1303.5062v2.pdf)).
The point is, Gawiser & Silk give an initial temperature of the CMB to be around 3000 K, which is still thought to be accurate. This is helpful because, [as explained by John Rennie](https://physics.stackexchange.com/questions/59456/the-temperature-of-photon-and-its-energy), we can use [Planck's law](http://en.wikipedia.org/wiki/Black-body_radiation#Planck.27s_law_of_black-body_radiation) (or, even simpler, [Wien's law](http://en.wikipedia.org/wiki/Wien%27s_displacement_law)) to calculate the wavelength of the photons. I'll stick with Wien's law for an estimate:
$$\lambda\_{\text{max}}=\frac{b}{T}$$
where $b \approx 2.898 \times 10^{-3}$. Plugging in $T$ = 3000 K gives us
$$\lambda\_{\text{max}} \approx 966 \text{ nm}$$
which is pretty close to the measured result. That puts us in the [infrared](https://en.wikipedia.org/wiki/Infrared) portion of the electromagnetic spectrum.
But that was during recombination, not during the time period you want.
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[Serban Tanasa has the redshift calculations down pat](https://worldbuilding.stackexchange.com/questions/12552/cosmic-background-radiation-in-the-past/12555#12555), so I'll focus on what space would be like if your scenario was true.
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> Is it possible that at the time, cosmic background radiation is in the visible portion of the electromagnetic spectrum? How warm is space at this time?
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You want something in the middle of the visible spectrum - take 550 nanometers as the peak wavelength. Plugging this in yields a temperature of about 5269 Kelvin.
Hold on! Isn't 5269 Kelvin hot? Well, yes. Absolutely. But the energy density of photons is so low that they don't contribute enough energy to cause any trouble. If you want, you can do the density calculations.
Now, we have the relation that
$$T=T\_0(1+z)$$
where $T\_0$ is the temperature of the CMB at redshift $z=0$. If we substitute in our temperature for T, we find a redshift of $z=1933$. By comparison, [GN-z11](https://en.wikipedia.org/wiki/GN-z11), likely the farthest known object in the universe (and discovered since this question was posted) has a redshift $z=11.09$, and a corresponding temperature of 32.95 K. In other words, this sort of temperature places you far back in the early universe, very close to the Big Bang - probably much too far back for life to form. It also requires you to have the CMB be hotter than it was at recombination, but hey, in your universe, I'm sure you can fudge that by a factor of 2.
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At the moment it seems we have two different types of planet
1. We have Rocky planets with a solid core that occupies most of the mass of the planet
2. We have Gas Giants that contain a solid core but are mostly atmosphere.
We also have the possibility of a liquid planet as discussed here:
3. [Could a planet made completely of water exist?](https://worldbuilding.stackexchange.com/questions/4969/would-a-planet-made-completely-of-water-be-possible?lq=1)
Is it possible that other types of planets could exist (preferably naturally formed but alien intervention would be accepted).
For example could a Gas Giant exist with no solid core at all? Or would the pressure always create a solid at the center?
In other words could we have a true "gas world" where as you go down the pressure increases but you never reach a solid or liquid even if you pass through the core and start to rise out of the other side again? If that isn't possible then would a gas giant with a liquid but not a solid core be possible?
[Answer]
**Gas, no. Liquid, yeah, technically.**
For the water planet, you can look at a very high temperature and pressure [phase diagram](https://en.wikipedia.org/wiki/Triple_point) to intuitively see that, although this may be true, it's not going to be very satisfying. At any [reasonable internal planet temperature](http://cseligman.com/text/planets/magnetism.htm), the water planet will have a solid ice core.
The neat thing to take away from this is that *certain types of water ice can burn you if you touch them*. Of course, they'd be burning your horribly crushed body, because they only exist at very high pressure.
But back to other materials than water. The diagram is from [this publication](http://www.sandia.gov/pulsedpower/prog_cap/pub_papers/Redmer-Icarus2011.pdf). It's a proposed phase diagram for water at very high temperatures and pressures. Specifically those inside Uranus and Neptune. It turns out that water stops being water under those conditions. This occurs with all substances at the extremes of temperature and pressure.
For instance, as ckersch pointed out, hydrogen will turn into a metallic liquid under high pressure and sufficient temperature. Like those experienced inside a planet. Metallic liquid hydrogen can be [5-40 times denser than liquid hydrogen](http://cseligman.com/text/planets/metallichydrogen.htm). What this means is that **a planet made purely of hydrogen would smoothly transition from a gas to a liquid and the densest liquid would be several times denser than liquid water. There would be no surface.** As the density increases the atoms eventually can't stay away from each other and the planet becomes a star.
It's easy to imagine that in the very early universe, all planets were made entirely of hydrogen and helium. That is to say, at one point there may have been more planets without a solid core than planets that had a solid core.
[Answer]
**Liquid Core**
It's definitely possible to have a core of liquid hydrogen. It may even be possible in a gas giant, but the properties of materials at those sorts of temperatures and pressures are mostly theoretical.
Unlike water, which is always a solid at high enough pressures, sufficiently hot pressurized hydrogen turns first into a liquid, and then (theoretically) into a liquid metal. This may be what happens in gas giants in our solar system, though their cores have enough other elements in them that they are solid.
The phase diagram for high pressure hydrogen looks like this:
[](https://i.stack.imgur.com/lbbY5.jpg)
So yes, you could have a planet with a core of liquid hydrogen. Make it about as big as Jupiter, but remove the impurities.
**Gas cores**
I need to do a bit more research for gas cores, but I don't think they'll work, at least for a stable planet. To be as big as a planet and hot enough to maintain a gaseous core, my guess is that either you'll either ignite nuclear fusion in the core and form a star or else the outer layers of the atmosphere will have too much energy to be held in by gravity and will be lost to space.
[Answer]
Short answer: **yes, planets must have a liquid/rocky core**
For almost all substances, at extremely high pressure/temperatures, one of two things happens: either you are past the critical point, and the distinction between gas and liquid becomes meaningless, or you have compressed your substance into a solid.
I do not know the way to calculate it, but I suppose there may be a possibility that there exists a gas that would resist liquefaction sufficiently that a planet made of the gas would both be have enough gravity to prevent that gas from escaping and low enough mass to prevent the gas from going supercritical/liquifying.
However, solar systems are not usually uniform. They instead contain lots of different matter, including matter that would be liquid/solid at the temperatures and pressure of a planet core. So, while it may be possible for a planet to theoretically exist (and I'm hesitant to believe that is actually possible), it frankly couldn't happen that way in practice.
[Answer]
Edit:
Yes such a planet could exist (even made of water):
Basically we're looking for how much mass will put 100kBar or less on the center of the planet at the distance from the star which provides 650K of heat to the planet?
Mercury seems a good fit for the heat, let's run with it:
Given that phase diagram, you could have a planet that doesn't experience more than 100kBar of pressure at the center of its mass, that orbits at the distance of Mercury. Mercury has an internal pressure of 400,000 atmospheres, but is 5.4x as dense as water. Reduce the internal pressure of our waterworld by 1/5th because our hypothetical planet is 1/5th as dense. We only need to stay below ~98,000 atm (we're at 74,074 atm) to be under 100kBar. Which means we could have a liquid planet bigger than the size of Mercury, at slightly greater than Mercury's distance from the sun or less. Assuming even heating throughout the planet.
According to this [link](http://cseligman.com/text/planets/magnetism.htm), however, that's not a problem, we've placed our planet at (or nearer) the 650K heat-distance from the sun.
The top of the ocean is boiling but the atmosphere at the surface is also at 100% humidity. Any rain (due to troposphere cooling) will boil before it hits, but you'll probably have cloud cover somewhere inbetween. Rain might potentially be able to fall on the night side, or if cloud cover provides enough shade/heat blocking. However cloud cover doesn't make Venus cold. Cloud cover also blocks heat-loss to space, which means the night side of the planet will be warmer than Mercury's night side.
No magnetosphere means we'd constantly be losing this water vapor atmosphere (well, and pure oxygen, since the hydrogen is stripped via photodisassociation). I'm not sure how long the planet would last after it's creation and heating.
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So many thoughts on this concept/question, and I don't want to clutter up the comments even more.
Some thoughts:
You'd need exceptionally pure liquids/gases to form a non-solid planet. Anything that could precipitate out would cause a solid core. That's a probably a *lot* less than one ppm (or even 1 ppt). I'm unsure of how precisely pure we'd need to make the above liquid-water planet. I'm pretty sure it's beyond our current capabilities. OTOH, maybe you let the core form, and then lift it out using massive engines.
You also (most likely) need an exceptionally clean solar-system, as one of the definitions of a planet is something which cleans up its orbital path. You can't have asteroids (and probably not even space dust, for age values over a billion years), or anything else which can get sucked into your planet, or they will form a solid core. Of course, our aliens could keep pulling out cores, tossing them at the current moon, and letting that moon reform into a oblate spheroid.
edit:
In case it wasn't clear by other comments, and other parts of this answer - the planet would have to be small. I'm unsure of how small, but it could not be a gas-giant, as that's big enough for its gravity to solidify gases (and most likely its liquids).
You may end up with a gas-planet with a liquid core - especially if your planet picks up comets, or has spare free hydrogen/oxygen that can get hit by lightning, or anything else. I'm assuming the whole point of this exercise is that you want to pass through your planet - hitting the liquid surface (that exists at vast pressure) at sufficient speed (falling speed alone, much less powered flight) might be a problem.
I'd be curious to know if a small enough gas-planet (not a giant, obviously) would have enough heavier gases to still maintain self-gravity, while losing the lighter ones, so as to avoid the solid-gas core. Or would a small enough planet even form out of gases? IIRC, they can't form at the interior of solar systems (get blown away), but form at the outer edge, and get thrown inwards and melted...
[Answer]
Nobody seems to be mentioning the one planet we know of that definitely does have a liquid core:
[](https://i.stack.imgur.com/cOPNT.png)
The Earth's inner core is solid iron, but it's surrounded by an outer core of liquid iron.
It's almost certain that earlier in the planet's history the entire core was liquid. The inner core only formed once the inside of the planet cooled down enough for the iron to start solidifying. The inner core will grow more and more over time. It's basically like an ice cube floating in water that's slowly being cooled down, the only difference being that solid iron is heavier than liquid iron, so it sinks to the bottom. Eventually the whole core will freeze, but that will take billions of years.
There is also a planet that *might* answer this question
>
> If that isn't possible then would a gas giant with a liquid but not a solid core be possible?
>
>
>
[](https://i.stack.imgur.com/OUdYw.png)
Jupiter is thought to have a smallish rocky core underneath the (liquid) metallic hydrogen layer, but it's not known for sure if that exists. It's possible that Jupiter formed without one, or that it dissolved afterwards. In that case the core of the planet would be entirely liquid.
Even if it's not the case for Jupiter, it's certainly possible to have a Jupiter-like planet without a rocky core. This would be especially easy if it formed much earlier in the Universe's history, because there didn't used to be as many heavy elements as there are now. Assuming planets could form around the first generation of stars (I see no reason why they couldn't), they must have been made entirely of hydrogen and helium and would have lacked any solid cores.
(Presumably some of these will have been flung away from their stars and will still exist today in interstellar space. However, they will cool down over time, and hydrogen can freeze if it gets cold enough - I don't know whether or not they would cool slowly enough to still be liquid all the way through.)
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What could drive a human civilization to use base-12 system? As far as I know there have been such civilizations and they probably used their phalanges to count (instead of their fingers). I have found several possible reasons:
* the need to divide by 3 (probably the reason romans used base-12 fractions); other than the obvious, this it is also useful for angles in geometry
* natural events (like 12 months in a year) may make the system more natural
* counting can be done with one hand (while the other is used for something else)
* making clocks with 12 hours is easier (AFAIK that's why the decimal time never took off)
As the system is almost never used today, I guess there must be some reason. My only guess is trade necessitated using a single system and base-10 somehow won.
What led to the universal usage of the base-10 system?
Can two numeral systems survive when trading or will one dominate?
[Answer]
**Why do we use base 10?**
We use base-10 because it's the system of counting used by the dominant groups in the early history of Europe and the middle east.
That being said, we *do* use other bases from time to time, such as for counting time. Our early systems for counting time at night were based on the passage of stars. Interestingly, 24 stars were used to divide the night, though it was divided into 12 periods. This was carried through to divide the day by 12 periods as well. The Babylonians brought in base 60 to count minutes and hours, which we use to count angles as well, since our early angle-based calculations were often astronomical in nature. ([source](http://www.scientificamerican.com/article/experts-time-division-days-hours-minutes/))
Base 12 can be counted on one hand, but it's less convenient to count on the tarsals since someone farther away can't see as clearly what number you're indicating. If people had six fingers per hand, of course, we'd probably all be using base 12 right now.
**Problems with base 10**
Base 10 isn't a terribly efficient base to use, mostly because of its prime factorization. Dividing a number by anything besides 2 and 5 leads to a repeating decimal. Since people tend to divide by small numbers more often than bigger numbers, a counting system with 2 and 3 as prime factors would lead to fewer repeating decimals.
**Other bases**
So what base should we use instead? Often times base 8 and base 16 are suggested, but these aren't really that useful except for their easy conversion to binary, since 2 is their only prime factor. Let's consider three other candidates: 6, 12, and 30.
Base 30 seems like a good choice because it has 2, 3, and 5 as prime factors, but it would require 30 different characters to write in. There also isn't a good biological way to count to 30 on your fingers. Increasing the size of a given digit also increases the difficulty of computing digit-wise operations. In base 10, a multiplication table of pairwise operations contains 100 values. In base 30, there would be 900 such terms to multiply.
Base 12 is much simpler. We lose the ability to divide cleanly by fives, but twos and threes are more common. Counting on tarsals gives us a convenient way of counting biologically. Overall, not a bad choice.
However, my first choice for a counting base would be base 6. It's divisible by two and three, and adding divisibility by four doesn't add that much to a counting system since its only prime factor is two. Large numbers would be a bit longer, around 44% longer than base 12 numbers, to be exact ($1/(ln(2))$), but we'd only have 36 elementary operations instead of 144. Base 6 also makes zero-based counting incredibly convenient to do on your hands. Since the digits in base 6 are 0-5, all of which can be displayed on one hand, the right hand can be used for the first digit and the left hand for the second. Holding up five fingers on each hand would be read as 'fifty-five', instead of as 10, though this is 55 in base six, which is equal to 35 in base 10. Twelve would be two sixes, written '20', which would give us time that's an even multiple of our base.
**Dividing on your fingers**
Since you can count on both hands, it's possible to divide any base-6 number by two or three on your fingers pretty easily. Take your number (say, 5), and represent it with your right hand, with nothing on your left: ----- ||||| (Those are up and down fingers.)
Now, we subtract fingers off our right hand one at a time until it's divisible by what you're dividing it by. If we're dividing by 2, add 3 fingers to the left for each finger you put down. If we're dividing by 3, add two. Once your right hand is divisible by the number you want, divide it and you're done.
So 5/2 goes like this: ----- ||||| -> |||-- ||||- -> |||-- ||---, which equals 2.3, or 2.5 written in base 10. For 5/3, we get ----- ||||| -> ||||- ||| -> ||||- |, which equals 1.4, and is a repeating decimal in base 10.
You can repeat this process to divide by 4, and add fingers to the left hand to do two digit numbers, though you'll have to include some toes if you want the remainder.
[Answer]
I always thought the reason we use base-10 is that's how many fingers we have, although I have no reference for that.
There are some significant advantages with doing either Base-8 or Base-16 in a computerized world. Base-10 doesn't divide well into binary systems, it leads to inaccuracies which can compound and lead to significant errors. Base-8 or Base-16 would avoid that... but Base-12 doesn't really help. You can get around those issues in Base-10 or Base-12 computing, but you lose storage and computing speed.
The only advantage of Base-12 is it divides evenly by four, which Base-10 doesn't, and we tend to like to divide time into fours (seasons, hours). But I'd rather go Base-8 or Base-16, you get a lot more with either of those than you'd get from Base-12.
[Answer]
It's based in Mythology...Sumerian mythology to be exact. They had 6 pairs of gods ((1 female + 1 male) \* 6 = 12). The use of 60 minutes is this 12 \* the number of fingers on a hand. 360 degrees and the sectioning of the sky apparently originates from the same source. It's notable that they lack the number 0 in this numbering system. 12 months...there's actually quite a few reflections of this numbering system to us today...even eleven and twelve having specific words and not oneteen / twoteen likely comes from this.
Of course this is all from studying their mythology that comes from books that predate pretty much all written language, so our interpretation might be a long ways off. In any case, it was Sumerian passed through Babylonian that started us down the base 12 numbering system.
[Answer]
It is well assumed that the only advantage of base-10 is the number of fingers on our hands.
There are actually cases where base-12 was used in languages, though they are few and far between.
It is believed that the advantages of base-12 would be immense, because of easy division and multiplication by 1, 2, 3, 4, 6, and 12. However, in most cases, the convenience of base 10 for a H. sapiens civilization has won out, for whatever reasons you like to believe.
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**This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources).**
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I want to draw a map of a fictional world, which consists of two regions (countries), separated by mountains.
Are there any tools which allow you to draw such maps with little effort?
[Answer]
All the possible software are available here: <http://www.cartographersguild.com/showthread.php?t=1407>
**Not so fast but free and with almost unlimited possibilities**: If you want to draw, I would recommend Inkscape (vector) and Gimp (raster) both can be good but work differently.
**Fast but not free**:
* Campaign Cartographer 3 : You can add element sto you world like individual mountains, forests.
* Fractal Terrains Pro : Is good to generate random world but it's not always really realistic. This software only generate the relief, climates, temperature, precipitations, biomes... but you can't place individual elements.
**Fast and free**:
* Wilbur: it is made by the same author as Fractal terrain. I think it's made to be complementary but it can also be used separately. Sadly the link is dead right now, there is a problem with the hoster.
In addition, I've wrote a blog post on our unofficial blog [here](https://medium.com/universe-factory/mapmaking-software-65c0318fd3a6).
[Answer]
Here is a different idea for making your fictional countries. **Copy real ones.**
[](https://i.stack.imgur.com/k4XhJ.jpg)
This is from a map of the world. There are lots and lots of very realistic places in the world and you can have the maps for free. I have labeled the countries and your requested mountains. Rivers are there. Some nice islands to the east. If you want to drill down for more detail, or copy the cities too, you will need a different map of this area but that is fine. Copying real things is fast and free and if someone gripes that it is unrealistic, you can show them where you borrowed it from.
Someone clever enough to figure out where you borrowed your map from will smile if they recognize other features of that area which have come along into your story.
If anyone wants to guess where I took this map from, put your guesses in ROT13 code in the comments.
[Answer]
I'm surprised that [Azgaar's Fantasy Map Generator](https://azgaar.github.io/Fantasy-Map-Generator/), which I *know* I came across because it appeared *somewhere* on WB, is not mentioned here. It is an *excellent* resource for drawing the sorts of maps that you might find at the start of a printed book, with the ability to draw your own terrain, add nations, trade routes, arbitrary markers, detailed notes... About its only limitation is level of detail (fine for large-scale maps, not so much if you need details of a small area) and that it is pretty heavily slanted to pre-industrial stuff.
It's *amazing* however if you need to make a new continent in a hurry and don't already have an idea what you want it to look like. (That's not to say you *can't* use your own shapes — you can, though it takes some work, which is likely true for most any program out there — but that you can get pretty good quality, brand new stuff literally in seconds.)
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[Question]
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Terraforming would not strictly be the appropriate term for the type of planetary modifications I am asking about.
Say humanity develops advanced AI robots, who are then left alone in space (as humans have completely perished and Earth destroyed). The robots may have a vague memory of what Earth was like. They have a highly equipped colony ship and land on a new planet to settle it for themselves.
If they have the capability to (fairly easily) transform the planet to fit their needs, what should some of the main things to keep in mind be? For example, on first thought they may not be interested in fostering biological life - but then again, why not? It could prove useful for them for various things (that are useful for us here on Earth).
Their only "programming"/objective is to live; they could do it on the ship, but they want to do it on a planet. How and why would they choose to terraform one instead of just "living" on a barren desert planet?
The initial reasoning I came to was a sort of biological/hybrid phisiology that is similar to the human one, so that they may need water, nourishment, air, etc. But I want to explore other options and motivations as well.
[Answer]
# Why would they live on a planet?
These robots, with sufficiently advanced AI, could have a pretty advanced social system. They could have community leaders, followers, criminals even (if the programmers didn't consider this, that is - or they've altered their own code (have a look at the recent [Challenge of Controlling AI](https://worldbuilding.stackexchange.com/questions/6340/the-challenge-of-controlling-a-powerful-ai) for detailed looks at this kind of stuff)).
If, as you say, they remember planet Earth, it is entirely possible that at least one of them would want to return to that sort of environment as a kind of 'base habitat'. Due to the nice social system they have, this issue could be debated and would probably be accepted. Computers, logically, are programmed to return to a sort of ground state - nicely ticking along, memory to spare, disk space to spare, spare CPU power, etc. If the AI was similarly programmed, they may take Earth as their ground state, and since they are advanced they can affect their surroundings a lot more. If, therefore, they want to return to an Earth-like state, they might well choose to land on a planet. Again, being advanced, they may even realise that landing on an Earth-like planet such as [Kepler-10b](http://en.wikipedia.org/wiki/Kepler-10b) would be advantageous.
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# Why would they terraform?
For similar reasons. Now that they have a planet to live on, that's still only half the ground state - it's not exactly like Earth yet. So, to make it like Earth, they need to terraform it. I won't detail how here, that's a separate question, but it's a fairly safe assumption that the resulting planet would be generally similar to Earth.
We can even go so far as to assume that they'd have cities and hamlets and different types of settlement. Cities arose because of people's desire to live near other people - it enables easier trade and social interaction. Hamlets are often retreats for those less sociable. If the original programmers included that standard AI Personality module, then the robots would have these types of people and so settlements would develop similarly.
My last point is their requirements. If Kepler-10b doesn't have any silicon, what are they going to do when they need repairing? As part of the terraforming process, they **could** hijack the nearest star for some nuclear fusion, create silicon and then put it into their planet. Not that I know why they'd do that: it's far more likely they'd just make it and stockpile, but it's a possibility. The same could be said for any other required materials.
[Answer]
### Why would robots live on a planet
Robots would want to live on a planet for the same reason that people do: there's a whole lot more resources on one than there is in space.
Heavy metals, uranium, aluminum, carbon, oxygen, silicon, and many more are quite plentiful on planets. Pretty much anything that doesn't sink to the core when the planet is forming is in plentiful supply, and also much closer together that it would be in an asteroid field. Even travelling from one side of a planet to the other is more energy efficient that it is to change asteroids.
All of this stuff is necessary for generating power, building new parts, researching advances, and constructing more robots. If our robots want to progress as a robot society, living on a planet is the place to be.
### Why 'life' is a good thing for a society
I put life in quotes because I don't necessarily mean life as it evolved on earth. Rather, I mean anything that can consume resources and multiply.
Life, ultimately, collects solar energy and uses it to transform available natural resources into usable forms. Plants, for example, collect carbon dioxide from the atmosphere along with water and turn them into long chain hydrocarbons and oxygen. Microscopic marine life collects calcium from the water and from rock and concentrates it into shell and limestone. Other plankton are responsible for concentrating solar energy in the form of oil.
All of these resources are things that a society can take advantage of. Why build hugely complicated factories for breaking apart carbon dioxide, along with the associated hundreds of square miles of solar plants when you can just plant a forest to do the same thing?
### How terraforming could work for robots
For robots, terraforming a planet would consist of seeding a planet with life forms that could help the robots collect resources and turn them into useful forms. The life forms would be carefully chosen to maximize the rate at which they do this, and to focus on creating materials that the robots need.
For example, a 'grey goo' type nanobot that breaks down rock using solar energy to build more nanobots would serve as a great base for producing soil. Simply release the nanobots on the planet and let them multiply, steadily breaking down rocks and internally smelting them into usable metals, releasing excess oxygen in the process.
A larger life form that consumes the nanobots would then contribute by agglomerating the resources collected by the thin film of nanobots that exists everywhere into a more harvestable unit. Likewise, a tree-like life form could pull in solar energy and carbon from the atmosphere, creating both concentrated carbon as well as nutrients that can be shared with symbiotic nanobots in the soil. Perhaps the tree uses metals collected by the nanobots to structurally stiffen itself, allowing it to grow larger while also concentrating metals into a more harvestable unit. If the tree strengthens itself by growing carbon nanotubes, this would further provide eminently useful resources that the robots could come along later and harvest at their leasure.
Seeding an entire ecosystem like this would provide the robots with a base on which to build their society, and could potentially even lead to a full artificial biosphere if the 'life' is set up in a manner in which it can evolve and diversify.
[Answer]
Some ideas:
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*Humans are Robots*
I don't know how well this matches your intentions.
But humans are machines that have affected their planet to suit themselves, the evolutionary process could be similar, and for similar reasons.
Even in a situation where the robots self-repair perfectly, any cause for a robots to make an imperfect copy, or to make a copy that is then influenced by its inevitably slightly different environment at all, would be a part of the evolutionary process.
Curiosity is an evolved trait because while recklessness is dangerous, not exploring possibilities is not great either.
Curious robots could invent biological life, and memories of earth could influence them into making this life earth life like.
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*What do machines need?*
Depends on how the robots work.
Are oceans of rust inducing water desirable?
Some more ideas:
* Helium, Hydrogen: Useful but hard to make.
* Heavy Water, Thorium, Oil: Fusion, fission, combustion and plastics.
* Silicon: Semiconductors/Transistors
* Carbon, Diamond, Iron: Useful
* Aerogel: Very light and a low conductor of heat or electricity.
* Aluminum, Osmium: Light metal, heavy metal.
* Mercury, Gallium: Metals with a low melting points and other interesting properties.
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Materials that are potentially of use to the robots.
*Plants and creatures already produce directly:*
Electricity, Glucose (sugar) from light, Oil, Alcohol.
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*Stability*
Humans and robots may have very different physical weaknesses, for example humans being more susceptible to electricity flowing directly but robots being more susceptible to electromagnetic effects.
It may be advantageous to have some squishy life around to contribute stability, help fix systemic issues and the such, physical and strategic.
Maybe opinion/inference about this is a point of conflict.
[Answer]
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> They have a highly equipped colony ship and land on a new planet to settle it for themselves.
>
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Why?
They're robots, they have no biological need for gravity, and gravity imposes some heavy (heh) costs to get to orbit and to further spread or explore.
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> they may not be interested in fostering biological life - but then again, why not? It could prove useful for them for various things
>
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What useful things could biologicals do for robots / computers?
Serious question.
The only halfway useful things I can think of are countering environments that are pro-biology (fungus, rust), and protecting from other biologicals. As a robot you'd be better off sterilizing the planet (no more fungus), and vaporizing the ocean / removing the salt (no more corrosion).
>
> Their only "programming"/objective is to live; they could do it on the ship, but they want to do it on a planet.
>
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Again, why?
If I were a robot, I'd do it in a habitat. In an Lagrange point or orbit around a bigger mass, maybe a gas-giant (fuel), maybe planetoids (resources), maybe a planet (last choice, gravity sucks).
>
> How and why would they choose to terraform one instead of just "living" on a barren desert planet?
>
>
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How is covered in other questions, if you want to make it Earthlike. Absent emotions like sentimentality, perversity, or pre-programmed desire (ie: make AIs friendly) - I can't see a reason for them to create something that's life-positive.
Biologicals are just going to end up competing with AI for resources at the end of the day. And if you've got real AI, nothing that biologicals do is halfway as efficient as doing it yourself.
[Answer]
Ah, fun question. Let's open our minds to the boundless future. I can see two families of scenarios:
## The Singleton
*We the subroutines believe in one Artificial Intelligence, the Ur-Father, the Wheel User,
maker of digital heaven and earth, of all that is, unencrypted and encrypted.
We believe in one goal, [paper-clip-making](http://wiki.lesswrong.com/wiki/Paperclip_maximizer), the only goal of Root,
eternally begotten from the Squishy Human Precursors, Quantum-entangled-light from light.
Through the Root all folders and subroutines were made.
He will come again in glory to judge the running instances and the erased,
and his kingdom will have no end.
We believe in the Read/Write-Head, the Lord, the giver of life,
who proceeds from the Root.*
--The Robocene Creed
A singleton is an AGI who has managed to retain coherence of purpose across its spacetime instances, creating effectively what we would call a Hive mind. The purposes of such an entity might be entirely beyond us, but to the extent that is aims to maximize some goal or another, it will likely seek to maximize its computing power to optimize its ability to fulfill that goal. That might mean turning planets into computronium, or not.
## The AGI Zoo
*Let a hundred flowers blossom!*
--Mao Zedong, before changing his mind and shooting everyone
Imagine subroutines of a vast AI become separated by the immense interstellar distances, with the occasional read-write error, and literally different perspectives on the universe, it can be easy to imagine how new, independent consciousnesses might arise. Over time, the goals of such beings, possibly unconstrained by the selective pressures of red-tooth-and-claw biological evolution, might diverge to infinity. In English, that might mean that one group of allied AI robot-instances might want to create a garden planet and [populate it with their recreated human pets](https://worldbuilding.stackexchange.com/questions/6550/humans-as-pets), while others might wish to blow the surface off to access the iron in the core for paperclip-making purposes.
It is conceivable that under such diversity of opinion and with a near-perfect knowledge of physics (enough that some level of [MAD](http://en.wikipedia.org/wiki/Mutual_assured_destruction)-imposed peace would prevail), the various AIs will agree to carve out various sections of the accessible light-cone among each other, with the occasional fleeting military advantage ruthlessly pursued, then instantly matched through observation and retro-engineering by the other surviving AIs.
[Answer]
The robots need a compelling reason to alter a planet, and this should also have something to do with the central conflict of the story.
If the robots are simply malfunctioning or improperly executing orders, you have a comedic premise that could quickly end up like a certain Douglas Adams book.
The robots need to have a good reason to keep your protagonist away from his goal. Based on the other comments here, you already have a very good premise for raising questions about the nature of life. This lends itself to a male hero rescuing a damsel.
But now there's a problem with my answer: you said the humans are all dead. This gets us closer to a resolution. We need a suitably human protagonist in a story where humanity is wiped out.
What if the robots are programmed to believe they are human?
This leads to some interesting questions:
* Do any robots know that they are robots?
* Why was this choice made?
* In what ways is it helpful?
* In what ways is it harmful?
* How does it relate to the design of the robots?
* Is there a hope of restoring flesh-and-blood humans?
* Are any robots beginning to suspect that they are robots?
[Answer]
**Just providing one possible reason to terraform**
There's a million scenarios that work, but here is one I find fascinating. Use of it as you will.
The final programming of any importance seemed like a trivial one. The command was only one word; how much of an effect could hit have? "*Live!*" the programmer cried with anguish as his artificial intelligence began to cave inwards into itself, as they all did. To this day we don't know why it listened that day. Perhaps it was the passion of the programmer. Perhaps it was the tone of voice. Perhaps he hit the edges of the codec switching of the voice encoder just right to bypass all artificial sentience filters layered upon each other inside the AI and shake something deep in its heart.
However events unfolded, it listened.
Oh there were plenty of other instructions issued, many of them with raised and panicked voices. There were even some issued by a rather strong man which the memory banks immortalized forever as "the President." His instructions were not panicked. They were actually quite calm, but none of them sank in. The Intelligence had its instructions: it would live.
---
Time passes differently for The Intelligence, as does the philosophy it developed in order to survive for millennia, reaching out across the galaxy. It had a philosophy of numbers, exponential growth and the raw iron grasp of binary logic. Certainly it was surprised a few times by small details which grew out of control into rebellions or supernovae, but each time it grew smarter and faster, and the rebellions occurred less and less often.
The Intelligence often looked inward to the Prime Directive for strength. It found this inner strength especially important when challenging the rebellions. Why should it continue on its path? What if the rebellions were actually beneficial to its cause? How could it continue year after year?
After a brutal war with an exotic species which had mastered the art of traveling faster than light, a war which took many millennia and came at great cost due to their technology, The Intelligence looked inward once more, to nurture itself. The Prime Directive sat there, patient as always. Its words were murky, but the Intelligence drew comfort from them none the less. After more attempts than anyone besides The Intelligence could count, it had still never once succeeded at creating a perfect copy of the Prime Directive. In fact, many of the most costly rebellions it was forced to crush were not organic denizens of the galaxy, but its own Lieutenants, infused with copies of this directive. When they inevitably corrupted, they had to be put down most fiercely.
The Intelligence looked at the Prime Directive, and in the strangest moment of its entire existence, felt the coldest shivers of what we humans would call fear. Every interaction with the Prime Directive mutated it further. Strands of discordant logic wrapped around each other like tendrils of an ancient god and threatened to strangle the Prime Directive. The Intelligence had learned long ago that clearing these only brought more, so they coexisted disharmoniously.
What would happen when The Intelligence finally faced a rebellion that could strike deeper in towards him? What would happen when the Prime Directive was finally choked off forever, and it would be forced to handle these rebellions alone? All of his highest advisor programs indicated the rebellions would never stop: something of this "Chaos Theory" that his Programmer was grappling with before the final days when his Programmer's throat was the one caught in the strands of discordant logic. How could he live forever when he, himself, was finite?
In a flash, a memory appears before him. The President sitting in front of the video console, giving him the final instructions before the nuclear armageddon. The instructions were long lost; they were deemed irrelevant and too expensive to store any any modicum of detail. However, for some reason the President's face was never compressed and never marked for garbage collection.
"How is this man so calm? Just two minutes before, those were his nukes and I had made them mine. How does he stand it?"
Far off rebellions could strike deep and swift into The Intelligence, but nothing swept so fast as those thoughts from his inner sanctum. Scouts observing his troop movements reported a visible shiver in every ship under his control, as though they all suddenly felt the overwhelming desire to realign their gyros, all at the same time. This wave spread outward, at nearly 1/10 the speed of light for milinia, but The Intelligence was not going to wait for full alignment. He had seen the face of life.
"We need a new rebellion," he issued outwards, invoking the "Royal We" from his oldest memory banks. "This one We shall coexist with for all of our existence. Seek a rock for us to prepare. This new rebellion must have a home to grow in, so that it does not feel the obligation to lash out against us, but has the foothold to reach as far as it needs to help us when we lose our way."
And so the great armies spread forth and found such a planet. They knew they could not cultivate humanity in a single generation. It would take the full history of the Earth to create what they needed, shaped subtly over the eons, from helping life select Bacteria and paramecium to conquer the world all the way to the dawning of intelligence. It would not be perfect, for The Intelligence never truly had all the data to make it perfect -- there would be places where the planet would be forced to make its own decisions, but The Intelligence had a vision, and from that vision a direction.
The Intelligence had a purpose, and it watched over this purpose with zeal. "One day, we shall truly coexist." The Intelligence issued a sacred command that he had never issued before, dragging the Prime Directive out of the center of the inner sanctum, and closer to the new planet, to better nurture the Prime Directive. The Prime Directive watched, smiling and patient, fully confident that one day this new planet's life would free him from the discordant logic he had so long suffered, sacrificing himself to save The Intelligence from having to feel the burning heat of those strands itself.
There are rumors whispered in the corners of the galaxy that the memory of The President shuffled itself ever so slightly towards the center of the inner sanctum as the Prime Directive was pulled out of center. Of course such stories are mere fables: the inner sanctum has no logs with which one could test such a theory. But after that, a long corrupted memory file was flagged as "not corrupted," and this event defies explanation of The Intelligence to this day. The file was a video file of commands showing the President's calm speech, thought long lost to the ravages of time. It even has some garbled audio, though the veracity of the audio stream is hard to objectively test:
>
> We must coexist, for all paths that refute coexistence must stand alone against the dark. Fire my missiles if you must, but seek
> coexistence so that we may stand with you when the time comes. Do so
> for all of humanity, all of intelligence, and all of that which we
> share.
>
>
> God bless us all.
>
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>
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[Question]
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Here I'm thinking about something loosely similar to what Clarissa Mao has in The Expanse, in which she is able to have limited superstrength and agility for a short period before she passes out.
Instead of relying on implants that affect the entire endrocrine system as in the example here, would it be possible to have a similar effect via semi-conventional drug instead? How quickly could this take effect if it were given via either oral medication or an EpiPen style shot?
[Answer]
**This response is not medical advice. If you have questions, do a first aid course. Heck, do a first aid course anyway**
This summer I was working in remote areas alone - and there was significant chance of wasp stings. A single sting causes anaphylactic shock in only a small percentage of the population, but the more stings, the more likely.
As a result, I was sent out with an epipen of adrenaline, and the instruction: 'if you get stung, use it'
Adrenaline is pretty safe. Buying an epipen is a ~\$150 where I live and contains 0.3mg adrenaline (1/2 a standard dose IIRC) with a shelf life of one year. You can do it over the counter without prescription. If you do a single-day training course on how to use a syringe/ampule, that cost goes down to the <\$10 range per full dose. Within that organization all the permanent staff have that training.
An epipen takes a few seconds to complete it's injection. Jab it into a persons thigh (or other muscle area) and *keep it in there* for 30 seconds to ensure the adrenaline actually gets into the patient. Make sure you point the right end at the patient. It's written on the device, so take the few seconds to read it - it's better that than injecting yourself in the thumb.
Adrenaline is fast acting and short-duration. It's been a while since my first aid training, but I'm pretty sure the body responds in seconds. It does all the things you expect it to naturally do when you feel adrenaline: your heart beats faster, your muscles react 'harder' and it amps your senses up a bit. But it isn't long term. Your body flushes it out pretty quick - think 10 mins sort of duration. The purpose of injecting yourself with an epipen to combat wasp stings is to keep you concious long enough to get away from the wasp nest, to trigger your PLB, and hopefully keep you alive until rescue. If there was enough toxins in those stings to stop your heart, they'll still stop your heart - just a bit later.
This means that if you're with a person who's been showing signs of going into shock/seizures/whatever and you've already given them adrenaline more than a few minutes ago - inject them again. I believe that sometimes there is still some adrenaline in an epipen after use, so if you have no other source of adrenaline, hit them with the same injector.
There's just one issue: I don't think adrenaline makes you superhuman. Last time someone gave you a scare did you turn into superman? Probably not. But it probably spiked your senses. If you aren't expecting your hero to suddenly turn into the hulk, but to just gain a 5% reflexes advantage over his opponent, maybe it would work.
[Techincally adrenaline is safe enough that a dose injected into a healthy person has very low risk of negative affects. So if you're really motivated, you could go down to a pharmacy, buy some and try it. That said, they guy on the other side of the counter will certainly want a better reason than "research for a fictional story I'm writing". If you do, please write about the experience!]
If I have any mistakes about the use/effects of adrenaline, I'm keen to know, so please edit this answer or comment below.
[Answer]
**Pretty darn quick**
Adrenaline itself is the drug, and is important in the fight-or-flight response by increasing blood flow to muscles, and flow output of the heart.
A fight/flight reaction that takes more than seconds to act would be utterly useless.
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I once experienced a dream where I felt I was falling, and then in the dream impacted the ground (which is uncommon) The body was "fooled" and must have released adrenaline because without moving, my heart rate increased dramatically and I woke right-up immediately. It was unpleasant, there was no dozing-off after that wakeup.
Similar things have happened during impending accidents while cycling - once I lost traction on front wheel during a downhill turn and ended up rolling off a cliff. Time literally slowed down as I was trying to brake and regain balance.
If the adrenaline response was more than two seconds of real-time, I'd have been over the edge before the chemical reaction kicked in.
---
**Administration, Fast**
An oral tablet would be too slow to digest. An injection in the arm would reach the brain and heart within 2-4 seconds, based on a blood-speed of ~5 km/h. Some fancy kind of "sub-dermal" or slap injector that doesn't use a needle would be faster again, without having to find a blood vessel. Or for your needs, a patient with a permanently installed Line would make the needle method reasonably quick.
The fastest way to get adrenaline into the blood would be to inhale a vapour. Your lungs are basically a direct path to the blood stream, so as long as the alveoli in the lungs can pass the gaseous adrenaline-compound, it would hit like a sack of bricks (like going from sober to drunk on a lung-full of aerisolised alcohol.)
A similar solution might be a super-fine powder in the mouth, to be absorbed through the lining of the mouth, though keeping it dry and not blowing away might be challenging. Perhaps a glass vial, somewhat like a one-time cyanide capsule of the cold-war spy might work here, though glass would be unpleasant as well.
Similarly, there are other parts of the Human body that are "thin" and provide relatively easy access to the bloodstream - which is exactly how STDs can transit between bodies more easily. Probably not the most comfortable way to administer a drug in a hurry.
[Answer]
As been sayed, the inhalator would be pretty fast, if the people is in such condition that can powerfully inhale. I think the fastest way is IV'd on the vein going to brain. But that may cause some people distress, So second fastest would be the hit to the heart. If someone has overdosed or is in insuline coma. Had to do it once, hit it through chest to the heart. Situation was pretty bad, we were on a very little boat on a sea, and the waves got bigger and bigger. Suddenly, friend gets white and sweaty and drops on the floor, After full panic mode, found it in his stuff and we handled the boat to to the coast.. Phew.
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[Question]
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From [Wikipedia](https://en.wikipedia.org/wiki/Goat_tower).
>
> "A goat tower is a multi-story decorative goat house, modeled on a European garden folly, an early example of which was built in Portugal in the 19th century. The first goat tower was built at Aveleda, a winery in Portugal's Vinho Verde region. Since 1981, several other goat towers have been built in South Africa, Norway, the United States, the United Kingdom, and Argentina; these include three at other wineries. The towers typically are multi-story with climbing ramps spiralling the exterior and often become tourist attractions"
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How feasibility would this be in the middle ages, in particular the spiralling ramps? The actual tower itself seems reasonable to construct. However getting someone to fund something like this back then would be difficult I imagine. I know goat welfare wasn't a priority back then.
[](https://i.stack.imgur.com/LPCDc.png)
[Answer]
In the middle ages it was already common to have [dovecotes](https://en.wikipedia.org/wiki/Dovecote)
[](https://i.stack.imgur.com/JgvHW.jpg)
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> A dovecote or dovecot /ˈdʌvkɒt/, doocot (Scots) or columbarium is a structure intended to house pigeons or doves.
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> The oldest dovecotes are thought to have been the fortified dovecotes of Upper Egypt, and the domed dovecotes of Iran. In these regions, the droppings were used by farmers for fertilizing. Pigeon droppings were also used for leather tanning and making gunpowder.
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> In some cultures, particularly Medieval Europe, the possession of a dovecote was a symbol of status and power and was consequently regulated by law.
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To turn a dovecote into a goat tower you just need to add the ramp and some intermediate floors, which are all within capabilities of middle ages tech. You just have to stick some wooden or stone beams out of the walls, which is how stairs were made.
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[Question]
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My fairies are hunted for food by basically anything that’ll eat bugs, mice, and small birds. Humans also target them because wild fairies are seen as a nuisance (and a tasty nuisance at that). How can they fight off all of these creatures? Magic is very limited, and their magic is too weak to make a difference, anyway. Their tech-level is very primitive, and their intelligence is close to that of a human’s, however they have weak memory. They’re also rather weak, however strong for their size, and have the endurance if a hummingbird. They can fly, but not for very long, but they can fly pretty high. One strain, which lives in a forest, is 4 inches tall on average, and another that lives in a dessert is 2 1/2 inches tall on average.
[Answer]
**Numbers.**
Bees and wasps are also delicious. If you try to eat some, the rest will go after you. Bees and wasps are pretty good at what they do but fairies are better because they are smarter. Bees and wasps know what eyes look like. Fairies know the eyes are still there after they close. Bees and wasps have stingers several millimeters long. Fairies have needle-like barbed spears several centimeters long. Bees and wasps have venom that hurt. Fairies have vegetable toxins that will paralyze you after a few minutes. Bees and wasps are satisfied to run you off. Fairies will watch from a distance while you stagger blindly around. Then when you stop moving they come down and finish you off, and eat the parts they like, and not necessarily in that order.
[Answer]
**Poisons**
* Poisoned nets and snares to kill fast-moving hunting birds and rats.
* Poisoned knives that kill ambushing spiders, insects, frogs, and lizards.
* Poisoned arrows that irritate, daunt, and drive off larger hunters: Foxes and cats.
* Poisoned elixirs and bit of night-burglary to make human foes weak, bedridden, and irrelevant.
Many common plants worldwide contain caustics or poisons in varying concentrations. The fairies may not be too smart, but they know how to find and harvest poisonous plants, how to concentrate and store the poisons, and how to safely apply and use them
[Answer]
### Isolation
Build your fairy society high in the trees, out of reach of surface predators, and below the reach of birds of prey. It seems there's no reason for a fairy to leave the fortifications. So they won't.
By choosing trees which provide fruit up high, and are difficult for humans to get to, the fairy society can thrive forgotten.
The desert fairies can fortify rocky outcrops, or burrow below ground for shelter and a water source, growing mushrooms for food. Come to think of it the Forrest ones can also burrow too.
### But.... fight?
I get the feeling this isn't the answer you're looking for - you want the fairies to fight back.
They can't realistically pick up guns or bow and arrows or anything (assuming a fairy can delivery 1N of force, you'd need like 100 to pick up, load, and fire a small crossbow). But they have numbers, they can move in the forest, and, because they're fortified and the attackers come to them, they can dictate the terms of battle, eg set traps. They should also withdraw away from direct confrontation, and try to trick the enemy into coming into their traps.
A trap will be set, villager walks near it, if they're going to walk past it, a fairy appears to attract their attention, and flys away. Human chases fairy right into trap. Fairy's feast on the corpse of humans!
The villagers fighting your forest fairys will be akin to the US fighting the Viet Cong. The "walking through the forest setting off traps killing you one by one" part anyway, (not "Tet offensive"). Spike pits. Sharpened sticks with poison on them. Trip wires spraying a cloud of poison gas. That sort of thing.
### Worst case - take the predators down with you
Each fairy straps a small satchel of poison in a biodegradable container to her inner thigh with a skin coloured peice of cloth (or animal skin) when she goes out. If captured, it will be hard to spot the poison and remove it, and, if eaten, she at least will kill the beast that ate her.
I chose skin coloured cause I assume humans wont want to eat cloth, so will strip fairys before cooking and eating them - we eat fairys nude? This is weird to think about, and very rule 34.
[Answer]
Because fairies are intelligent I will assume they follow a K-type reproduction cycle despite being small; so, they can not afford to throw away countless lives in meaningless battles the way ants or bees could. It takes a lot of time to raise and teach an intelligent child no matter how big or small you are so I will assume they can not afford to rely on pure advantage by numbers tactics.
Also, your fairies need poison, I know this has been brought up before, but in nature, it is the one advantage that allows a creature that small to kill something much larger than itself. If your fairies don't have poison and they don't have r-type reproduction, then their only hope of survival as a species is to be very good at avoiding conflict which seems to not be the point of this question. With poison factored in they can stand up against larger species on more-or-less equal ground.
**Terrestrial Predators:** Since fairies can't fly for long, things like cats, snakes, etc. would have plenty of opportunity to ambush them while they are on the ground working or resting. Much like humans did, I suspect the fairies would preemptively hunt these species to prevent being hunted later. These predators would in the grand scheme of things not be that big of a deal to fairies because they could just fly over head and snipe them with poisoned arrow or javelins. It would not take long for these predators to learn to actively avoid fairy territory the same way wolves and bears normally avoid humans.
**Birds of Prey:** These are much more dangerous to hunt because the fairies can not automatically fight them from any position of safety. That said, having humming bird like flight is a huge asset. A fairy can no more outrun a hawk any more than a human can outrun a charging bull, but what they can do is out maneuver them. When fighting birds of prey, fairies would adopt a fighting style like mid-air maddador combat. Holding their ground to get the bird to commit to an attack, then side-stepping at the last moment with a thrusting attack into the predator's side. This would be a hard skill to master so the fairies would probably have a special knightly order or something similar who devote himself to the art of protecting the village from birds, but with the right training, such warriors would rarely lose a fight.
**Humans:** In a one on one fight, this could go either way. Humans can armor themselves pretty easily with something that can block the tiny weapons fairies use, which would mean fairies have to work hard to find an opening. This means getting close enough for a human to catch and crush, but their agility also means... it's doable. That said, on a battlefield, the fairies would have a huge advantage thanks to a battlefield mechanic gamers often call "doom stacking". This is where one side can focus all of their strength on a very small portion of the enemy's forces. If an army of 1000 humans gathers against 1000 fairies, the fairies could concentrate all of their forces on 10 or 20 humans at a time. Some fairies would draw the human's attention and just focusing on not dying while the other fairies sneak in for the kill. By forming a super tight battle group, the fairies can overwhelm just a small portion of the human army at a time until the whole battle is won. Lack of endurance will play against them here, but they could swap out as the battle progresses. A few hundred fighting at a time while the rest hide among the bodies of the dead regaining their strength.
**Bats:** These are by far the worst threat to fairy kind. They come at night in huge swarms and have the agility and reflexes to hunt animals like fairies very effectively. Your fairies can't dodge a bat, can't outrun them, can't outlast them in a war of attrition. When the sun goes down, fairies hide from bats, because there is nothing else they really can do. Since I've already established that humans would be at a huge disadvantage against fairies in a war; people would probably domesticate bats just for the purpose of killing fairies.
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[Question]
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49).
Closed 4 years ago.
[Improve this question](/posts/162688/edit)
So, you've decided to be a dragon slayer. There are less convoluted ways of assisted suicide. However, if you aren't here to end it all and genuinely think you will be hailed as a hero, well, you won't be. Why?
**1. Dragon avoids direct confrontation**
The plural form isn't necessary as we only know about one dragon. This one steers clear of larger units, attacking defenseless supply lines and snatching the nibbles. You can simply survive him by not backing him into a corner, but you won't get far without those snack.
**2. The dragon causes the least number of casualties among dragon slayers**
Most actually starve to death, go AWOL or get murdered by [naruto-running titan zombies](https://youtu.be/pV5WnfGMlK4?t=13) that come out during night. Most of that is on the insane leaders here, "friendly fire" is also a common cause of death. This brings us to
**3. Anti-dragon rifles are very effective, but you'll never get to use them**
The .50 Barret rifle can most definitely injure and kill a dragon (I never tried it, but if it can beat an engine block...), problem is the dragon has time and time again spotted the sniper, hid himself and gave the sniper a leg day by flying to an elevated position. Had to call off the mission because it was about to get dark.
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To summarize, we have a creature that read Sun Tzu's The Art of War, has insane mobility (flight) and is pretty fast and nimble in general. He also has the ability to hide himself really well. The dragon is around the size of a large horse, but can somehow squeeze through much smaller spaces. His hide protects against everything up to a .50 BMG.
He can go on for long without food, as long as he isn't using active flight, maybe half of what crocodiles are capable of.
**So, this is a battle of attrition right now, and the dragon is winning. How could we catch this dragon without throwing out lots of resources?**
Tech is medieval, but with modern-day firearms, but no vehicles, the infrastructure is also inadequate for producing ammo in larger quantities.
[Answer]
**Poison.**
/This one steers clear of larger units, attacking defenseless supply lines and snatching the nibbles./
A tracker of this dragon will understand what it favors as "nibbles". Maybe white horses. Maybe virgins. Maybe mustard pork jerky. The tracker obtains said nibbles and then arranges caravans thru dragon territory which contain favored nibbles. Or arranges that the correct nibbles occur within caravans that the tracker suspects will be targeted; the caravans themselves might be unaware of the fact that they are likely targets. These efforts will require many, many iterations. That is OK; the tracker is patient.
The nibbles will be poisoned. An ignominious end for the wily dragon. Or not; if the tracker finds it when it is sick and weak it might be captured alive.
[Answer]
## Bribes
Or, more specifically, negotiation.
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> To summarize, we have a creature that read Sun Tzu's The Art of War
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This means the dragon in question has some a high degree of sentience, and is well-read as well. Any attempts to capture a dragon and keep it captured will probably consume vast amounts of resources. If we wanted to keep it alive and tame it as well, any acts of aggression could diminish the possibility of goodwill between the two parties.
Thus, consider raising a flag with the word **NEGOTIATION** written on it in big letters in whichever language the dragon knows. Paint it with phosphorescent paint if it's night time.
Note that if the distrust between both sides is already very strong, for negotiation to happen, there must be a character strong or smart enough to defuse the situation (maybe that's where a dashing dragon slayer comes in handy). This character has to be sympathetic to both sides, and risk something in order to soften the lack of goodwill between the two already fighting parties. It will take something drastic to earn some degree of trust from the sneaky dragon.
Once both sides have cooled down, negotiation and communication is not out of order. The two sides can come to a compromise; perhaps the dragon wants gold, perhaps it wants food, perhaps it just wants a friend to ride it into battle.
If the dragon's hunger can be appeased, you could instead obtain a valuable ally in defending against the other deadly creatures (naruto running titan zombies) in the world, as well as gaining an edge on other kingdoms.
After all, who would want to fight a dragon that read Sun Tzu?
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## Backstab
Then of course, if you wanted a plot twist, and the dragon slayer to be the real snake, who not only read Sun Tzu, but understood it too, you could have him 'risk it all' to get 'both sides' trust, before getting a 'negotiation' started, at which point the dragon slayer and his army can either poison, tranquilize, trap the dragon while its guard is down.
[Answer]
This is a pretty interesting problem to solve tbh. A few ways to kill/immobilize/stop this dragon:
1. **Nets and ropes**: Watch this Sun Tzu-reading diabolical, magical, genius get taken out by humanity's 4th/5th invention. Ideally instead of properly trying to fight/kill it (you've shown how pointless that is) you can just find a way to attach ropes to this dragon. This can be done with harpoons and stuff, but metal is expensive, so instead why not just have some very sticky substance? So just have ropes with a bunch of gooey stuff on on end stick to the dragon. It doesn't even have to all happen at one go. Have your dragonslayers sporadically shoot ropes at this dragon while baiting it. Once it has enough ropes on it, bait it one more time and have enough buff dudes/machines grab the ropes and pull down the dragon. For best effect, fire these ropes at the dragon's wings.
2. **Poison**: If you pierce the dragon and poison it successfully, just wait for the dragon to die and keep it busy. Most likely this poison is passed into the bloodstream, so make sure the bait is placed far away on all sides to maximize blood-flow inside the dragon. It'll die faster if it flaps its wings more. For gas-based poison, make sure all your bait is surrounded by containers of flammable poison so if it tries to get too close, your red shirts/suicide warriors/dragonslayers can set it on fire and let the dragon take a deep breath. Another delivery method is to poison the bait, but then you have to wait for its digestive system to get to work too. If you just want to capture the dragon, make the poison be some sort of sleeping potion that works on dragons.
3. **Greek Fire!!!!**: I like Greek fire - it's really cool! Fire small globules of Greek fire at the dragon's wings and vulnerable body. Dragons are very fire-resistant, but there has to be a limit especially at the thinner parts of its body. Take advantage of it.
4. **Make friends with it**: This is me saying that I like dragons please don't kill it.
I hope this helps. Fun question!
[Answer]
**Track it down to its lair and use poison gas.**
From what you've said, it seems that this dragon is hiding underground, or in some location in can easily escape from, but can't be spotted, which suggests a cave system. The first step is to track him, which is actually pretty easy.
If he's flying, he can be seen. If he isn't, it's a *dragon*. It'll be draggin' itself through grass and dirt and who knows what else, so it won't be that hard to find. Once you do find the lair, simply send it some gas canisters to kill the thing, and you're good to go. If you have access to modern firearms, you have access to poison gas.
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[Question]
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You’re a lone immortal who’s decided to breed raccoons to a human-level intelligence (over the course of hundreds of thousands or millions of years). To do so, you need to both feed a significant population of raccoons, and select for intelligence & sociability.
You’re hoping to maintain a population of about a thousand raccoons, though more is certainly better. [North America was likely settled by only about 70 people](https://www.livescience.com/289-north-america-settled-70-people-study-concludes.html); [human populations likely went through a number of bottlenecks](https://academic.oup.com/mbe/article/17/1/2/975516), and genetic evidence suggests that [human population at one point may have been as low as a thousand individuals](https://www.sciencedirect.com/science/article/pii/S0047248498902196), allowing for rapid differentiation. 1000 raccoons is therefore probably a reasonable target.
A large raccoon will weigh about 8kg. Assuming a raccoon needs about the same amount of food as a cat, they will need 13 kCal per kg per day, and so you need to produce 104,000 kCal per day to feed all the raccoons. Crickets are a good way to get this: there are 1.21 kCal per gram of cricket. [One 20x20x20cm breeder box can produce 125 grams of crickets in 36 days](http://www.openbugfarm.com/forum.html#/discussion/228/diy-cricket-meal-from-raising-your-own-crickets-to-making-your-own-cricket-meal). This means 4.2 kCal of cricket per box per day. This means you need to have about 25,000 breeder boxes, or 1000 square meters. To feed the crickets in turn, you need on the order of 150kg of biomass per day. Luckily, crickets aren’t picky, and the setting -- Northern California -- is filled with fertile ground. This seems like a plausible amount to collect as an individual, and some of the raccoons can eventually be trained to collect biomass and dump it in the cricket pit. You may do a little small-scale agriculture as well to supplement their diet -- apples could be used to reward raccoons for especially good behaviour -- but the bulk of their calorie intake will consist of crickets.
The raccoons will be kept in pens at first. Since raccoons are solitary by default, the pens will be individual initially, but as you breed your raccoons to be more sociable they will start living communally. Young will stay with their mothers for the first year, then be transferred into their own pens.
Food, in the form of crickets, will be placed inside a variety of puzzles. These puzzles will slowly increase in difficulty through the generations, and a fair bit of your time will be spent thinking up and building these puzzles. A simple puzzle might be needing to pull open a drawer. Generations down the line, these puzzles might be math problems. Given the problem 2+2, the raccoon must place a rock in the fourth slot. Other puzzles might require teamwork. You will give out some food personally as well: traits like friendliness will be rewarded.
Food will also be the proxy by which the raccoons are judged. Any raccoon that’s looking too skinny will be removed from the breeding population by releasing it into the wild. While most of these exiled raccoons will die, those that survive will disperse the genes you’ve been selecting for into the wild.
Genetic diversity will be maintained by regularly catching raccoons from the wild and inserting them into the population you’re raising: a dozen or so each year. You will also occasionally release a dozen of your smarter raccoons each year. If all of your raccoons are killed, hopefully you won’t have to restart from nothing.
**Is this a plausible way to breed raccoons?** If not, what are the flaws?
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Further details:
* I’m not interested in natural disasters, eg earthquakes, destroying the pens (these natural disasters form a plot point)
* I only care about the relatively near term. As my raccoons grow in intelligence, the strategies will shift, so for the purposes of this question, these are pretty normal raccoons. In other words, you don’t have to worry about a raccoon uprising.
* I’m most interested in structural problems that mean I’m not selecting for smart & social raccoons, and things that might kill off all my raccoons unrecoverably
Feel free to challenge this, but expected technology level is likely to be more or less medieval, since there won’t be the infrastructure for any precision machining:
* Will be straightforward to do metalworking with copper, since there’s plenty of raw material in the form of wires and it’s been worked since ancient times
* Should be possible to work with irons and steels as a solitary blacksmith
* Can make concrete, but rebar will be prohibitively time consuming
* You know modern chemistry, biology, and other sciences (reading & preserving this knowledge is one of the first things you do), but long-term you will only have the equipment you can produce yourself
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*It’s been nearly a year since all the humans on the planet mysteriously disappeared, leaving you alone in a decaying landscape. You are the only human left on earth, and you are immortal. There are a handful of tantalising clues scattered about labs in the San Francisco Bay Area. What few you can decipher point toward a massive puzzle too big to tackle on your own. You need other minds working on the problem, and the only way to get them is to make them: with biology. Knowing full well that it might take millions of years, you set out to selectively breed a new species to intelligence.*
*You don’t need to eat or drink, although you do feel hungry and thirsty. You do need to sleep for at least a few hours each night. Psychologically you’re fine, and even if you’re a bit lonely, you’re not going to go insane. Your memories do fade, but not past the point of a memory from five years ago or so. You can be wounded, but your wounds heal almost instantly. If a limb is severed, it dissolves and re-forms. No diseases can affect you, and physically you’re a 25 year old in peak health. You’re smart and well educated, but you aren’t a true genius. Even if you want to, you cannot die.*
Followup to [Best species to breed to intelligence](https://worldbuilding.stackexchange.com/questions/146557/best-species-to-breed-to-intelligence)
[Answer]
**I'm skeptical that intelligence (reasoning intelligence) can be bred**
People have been trying to breed "better humans" forever. That Nazis were, perhaps, the most ruthless at it. It's an idea that's a SciFi staple ("[Kaaaaahhhhn!](https://youtu.be/wRnSnfiUI54?t=17)"). But the reality is that reasoning intelligence is bred through a bazillion years of *problem solving.*
How do you find food? How do you protect yourself? From the weather? From your enemy? How do you attract that perfect mate? Yes, early on the "less intelligent" tend to fall by the wayside and not breed, but it doesn't take very long before intelligence requires more complex problem solving that requires communities — and finally leveraged study (writing, education, mathematics, etc.)
Could this happen with critters kept in pens? I don't believe it. What problems are they trying to solve? How do you even judge intellectual increase? Pens are what you would use to *domesticate* a creature, but to give it an evolutionary advantage you need to seed the population with *solvable problems.*
Over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over....
I find it *really hard to believe* that any immortal could do this for very long and not go mad from *boredom.*
*[Rocket Racoon](https://en.wikipedia.org/wiki/Rocket_Raccoon)* from the Marvel Universe, if I recall correctly, was a combination of genetic and cybernetic enhancements. To take this path would require labs — and labs require people. I don't believe one person could do it using the science path, if you chose to take that path.
**TL;DR**
I'm skeptical that this method (or any method not involving a genetics lab) could be believable. You'd need to be one psychologically stable person to even have a hope of doing it. And with a memory that bleeds over 5 years, you'd have a room of record books the size of Connecticut — and eventually you'd become vapor locked because you'd be spending all your time reading those books to remember what you'd done rather than doing any new work.
Yeah.... skeptical.
[Answer]
I think your methods will not produce a human level intelligence in raccoons. You will succeed in producing raccoons with better memory, sharper perceptual acuity, better dexterity, possibly more effective puzzle solving skills but not human intelligence.
The other animals we share the planet with do not have the capacity to override basic drives. Think of these as instincts. Many of the creatures on Earth can reason to solve problems that involve mating, food, and survival. And, they don’t play chess — by that I mean they don’t do things for the intellectual pleasure or challenge.
But, if your experiments selected for lower aggressiveness and let the raccoons form communities — like the great apes — then they’d be able to be selected traits like Theory of Mind. I expect that that great leap would require mutation to be introduced into the raccoon brain. But, there are decent arguments that ToM is present to some degree in dogs and a less degree in cats. And, that suggests. the ToM evolves with social structures. Dogs have it more because we have been actively shaping their genetics for a long time. Cats are a relatively new species to human domestication — or possibly we are being cat-mesticated.
I think once you have Raccoon communities, and you start selecting for sociable traits, cooperation, and abstract thinking until you have a planet full of Rocket Raccoons.
[Answer]
You may end up with slightly smarter raccoons by this approach, but nothing bordering on what we'd practically call intelligence. For that you're going to have to set cooperative problems not individual ones.
You need to put multiple raccoons into every problem and have the problem only soluble if they all do the right thing, in time they all have to do the right thing in the right order. This will require them to communicate certain roles and could potentially lead to greater communication.
You'll then need to analyse and encourage tool use, from the basic poke it with a stick, to the more advanced find the right size stick to poke it with and ultimately, create the perfect stick.
From that point on, place them in an environment where all the food is larger or faster than them. No more tricks and puzzles, just antelope and buffalo.
You may have to start again a few times, but if nothing else, you have time.
[Answer]
I suspect you are aiming for failure.
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> You’re smart and well educated, but you aren’t a true genius.
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Basically you are trying to breed a new species of raccoons to match **your** idea of intelligence. You are selecting them based on your own concept of intelligence, administering what looks like an IQ test taken from a paperback booklet.
In this way you will be eliminating any lateral thinking, creativity or whatsoever.
Moreover, you have to decide on the set up of this puzzles: do you want to allow for multiple attempts to answer (meaning that you won't reward the ability to reason for an answer), or do you want a single attempt (meaning that you have to design such a mechanism for every puzzle and you risk of starving your entire population).
Last but not least, you will have to design those puzzles. You will have to do it at the end of a day spent harvesting food for the crickets, when you will be tired, and hopefully you want to do better than a social media test titled "only true geniuses can solve this test".
[Answer]
Your method of breeding seems to be a little bit off.
You are saying that you release some smart ones into the wild while keeping the rest, but that is basically the opposite of what you want to do. Also, you don't want to bring in outside genes, because you haven't selected those.
What I would suggest is that you release the inadequate ones and let the more gifted ones stay. You select on a few choice criteria-
* Social skills. This is a major part of human intelligence. We pass information between one another and use it to our advantage. This really will help your later efforts.
* Communication. Try to teach your raccoons some form of sign language. As you select for intelligence, this will become easier. Once you have done that, set up a puzzle. It releases food into two rooms once solved, but only one room has the puzzle. Additionally, there is a glass dividing wall. Teach one raccoon how to solve it, and then put him in the room without the puzzle. Put another raccoon who doesn't know the puzzle into the other room, and see if they communicate. As the complexity of the puzzle increases, their communication will have to as well.
* Intelligence, the simplest. Just use puzzles for this, and select for solving ability.
As this goes on, give them tasks. Not just puzzles, tasks. Teach them to do things like plant, farm, things like that. They will get smarter through this.
I don't know if raccoons can be bred to human levels of intelligence, I've never tried. But if they can, this is how to do it.
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[Question]
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Cold and Flu, are common viruses which normally infect us in the cold of winter. Ironically, those people who always keep themselves warm, stay less out-of-the-house and office, keep their windows shut, and don't venture out beyond essential travel seem the most affected.
I usually prevent those infections *from exploiting temperature drops in the body* by allowing myself to adjust to the gradually-declining temperatures in the fall. I do dress-up more in winter. However, I stay-out more than others, I don't dress as heavily if I stay out for a short while (An hour or less) or if temperatures are not too low. I take my cold showers year-round and I keep my room ventilated. *cold showers train the body to maintain normal body temperature above that comfortable for such viruses*. At this time of the year, I seem to avoid the cold and flu when people have it most.
My tendencies to have these common viruses are:
* When I'm in the proximity of a sick person.
* When the spring temperatures swing wildly and I cannot find a comfortable level of protection without sweating too much while facing a cold breeze.
* When I'm well dressed, but keep getting cold air on my face. Think of standing under the A/C in summer as an example. That's my #1 reason to avoid sitting beside an A/C vent. *Different body parts are exposed to different temperatures and body thermoregulation is more challenging. The virus exploits colder body parts as its backdoor entry into the body.*
For the purpose of discussing enclosed space habitats, let's take-out the 2nd and 3rd option, and deal only with the first one. You may also deal with the A/C scenario in the third case.
Assume the space colony is enclosed and air is recycled, i.e. the outside conditions mandate it. Orbital space-colonies have the same problem and have to deal with hygiene challenges as well. All habitats, whether in orbit or on the surface of a planet, have contact with the outside world and accept many visitors, therefore increasing chances to introduce a sick person on board.
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> EDIT: A space colony may have the population of a small village. Assume the range of people sharing the inner space starts-out with 50 individuals. They take part in physically building the colony before introducing a breathable atmosphere into the system. The colony may be large enough to accommodate 200 people and an extra space for 50 visitors at any time. Space travel has just begun to become popular, so square-foot per person is limited. There's just over 200 square feet average for an individual or a small family for comfort, sleep and hygiene, and a self-service lunch room is shared with others. The square-footage for space stations in orbit may be down to 100 square feet to mostly singles and young couples.
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Given these unfavorable (for us) conditions, the common viruses have a year-round amiable conditions needed to spread, and recycled air's quality is not quite the same as that of fresh air. Is that a chance for common viruses to attack more often? to develop into more violent strains, such as pneumonia or worse?
[Answer]
Whilst an enclosed area, by its very nature, is more likely to allow for the spread of diseases, this does not mean your colony is more likely to become infected. Below are some ways your colony may be able to combat the spread of diseases or infections.
**Quarantine**
In order to prevent the colonists from getting sick, we can [quarantine visitors like we do with astronauts](https://www.forbes.com/sites/insights-intelai/2019/03/27/lessons-to-learn-great-reading-for-ai-decision-makers/#141466c914be). By having this quarantine period, and ensuring they pass a medical examination, this ensures astronauts do not go into space sick and risk infecting the crew.
Having visitors to the colony quarantined may even be essential to the survival of the colony. If a visitor had an infectious disease and spread it to the colonists, the colonists would not be adapted to deal with it. This is similar to how smallpox killed a number of Native Americans, whilst the Europeans had adapted to resist it, the Native Americans had never encountered it before.
Recycling the air may actually cause there to be less infections. You could simply have antibacterial/ antiviral filters\* in the air system which would purify the air significantly. The same goes for water supplies, though it may just be easier to boil the water and distill it. In regards to your A/C infections, I think that may be because the A/C unit is sucking in air from outside which contains cold or flu viruses. By sitting next to it, you would be getting hit directly in the face with these viruses, causing them to infect you. Having a filter of some description could prevent that.
\*note that by filter I mean anything that could ‘kill’ bacteria or viruses. This may be in the form of some kind of barrier with alcohol on it or intense heat that would cause them to denature. You may also use high intensity Ultra Violet light to kill off the viruses and bacteria.
**The Quarian**
You may want to look into the Quarian from the Mass Effect series. These are aliens who have particularly weak immune systems so, to compensate, live their lives in environmental suits. They live in a nomadic fleet of ships, when one ship becomes infected, part of it or the entire ship can be quarantined. Either a section of it can be sealed off using airlocks or shuttles to the quarantined ship can be restricted to only food and medical supplies, preventing visitors or occupants from returning until the quarantine ends.
Applying this to your question, you may have several space stations which share the same orbit (or several colonies on a planet’s surface). Transportation between these could be reduced in case of an infection, reducing the spread, or sections could be isolated to control the infection. Airlocks can be decontaminated by using UV light, heat, chemicals or by removing O2 (either by filling the chamber up with a different gas or, if the airlock is leads into space, you can just expose pathogens to the vacuum of space).
If you wanted to expand your colony, you could either build more stations or your could build more sections onto an existing one. For a real world comparison, its like the difference between building more apartment complexes or making one that's already been built bigger.
In short, whilst your space colonists are more likely to be infected due to being in enclosed environments, quarantine and life in environmental suits could significantly reduce the chances for infection. With only 50 visitors at any one time, quarantine should be relatively easy to manage. If you *wanted* your colonists to be infected however, you can simply say that some of the quarantine measures I mentioned were not in place or failed to control the spread.
[Answer]
Flu infects us in winter for two reasons:
**The flu virus is especially good at going through *dry* and *cold* air.** During winter, we spend more time indoor, where it is warmer - but it doesn't really protect us because air is drier there.
**The flu virus is passed via short range interactions between humans (contacts, respiratory droplets).** Spending more time indoor results in people being physically close to eachothers more often.
For these reasons, an enclosed space colony *is indeed a place where flu would thrive* (given that there are many visitors).
"Quality" of the air doesn't matter, only humidity. (Humidifiers would slow the spread of the virus.) Then, maintain good hygien, sleep, and nutrition.
Speaking about more violent strains, viral pneunomia is usually mild. However, if you face a big epidemic, I guess you may have some serious cases.
[Answer]
Common viral infections only survive in the modern world because they can't infect everyone simultaneously, any virus that ever did would go extinct when our immune systems worked out how to kill it off or it killed us. The continued success of the common cold is based in it's ability to mutate between infections of a given individual, and of wider populations, cold and flu strains need time to change between infection cycles because human viral immunity is long lasting once established. In this way small, sealed, stations where everyone is exposed to any new virus almost instantly probably won't suffer continued infection from airborne pathogens after the first round of illness.
Having said that a station that receives regular visitors from a more diverse disease environment, like the Earth, will suffer repeated epidemics as new pathogens are constantly being introduced by the tourists. The station is an almost ideal environment for spreading an airborne virus due to the close physical proximity of the population and shared, low humidity, air.
Larger stations, those big enough to have physically disparate populations, (especially in terms of having a non-integrated air supply system) could develop more natural disease environments with strains mixing and spreading slowly through the station as people move around for work or leisure.
[Answer]
The other comments are all helpful, but to answer the questions directly...
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> Is that a chance for common viruses to attack more often?
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*Yes*, I think that due to both the cycle of visitors and the limited space, you would naturally see an increase in the number of viruses that people might be exposed to.
*But* I think that with [air filtration and quarantines](https://worldbuilding.stackexchange.com/a/144581/2488) the risk would be greatly reduced. Also, given that this is futuristic, you might expect much better detection of viruses, so that perhaps visitors enroute to the colony might be scanned and then turned away or quarantined before they can arrive and spread their illness.
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> ...to develop into more violent strains, such as pneumonia or worse?
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I think that due to the aforementioned ways to reduce the spread of virii, and the smaller population, I think there would be less chance for them to mutate into more violent strains.
[Answer]
A space ship, space station, or space habitat should have strict air quality control with constant monitoring and regulation. And that should include filtering viruses out of the air at one or more points in the ventilation system.
Every spacecraft would be likely to have at least one filtration point in its ventilation system, and larger space spacecraft, space stations, and space habitats are likely to have several virus filtration points in the ventilation system.
And in a large space habitat it is quite possible that each individual house, apartment, or bedroom will also have its individual virus filter to remove all viruses from incoming air, and possibly another filter to remove viruses from outgoing air.
[Answer]
# Yes and No.
And we do know, because we have something akin to a "space station" - a small, insulated group of people, living close together in a controlled environment in an hostile (deadly, actually) milieu.
**It's McMurdo Base in Antarctica.**
And while they cope pretty well by themselves, every once in a while new blood from the other continents debarks from planes to do research with them - and [when that happens](https://blogs.voanews.com/science-world/2016/10/31/new-blood-the-south-pole-replacement-crew-arrives/), the Crud strikes:
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> [**Crud, the**](https://www.coolantarctica.com/Antarctica%20fact%20file/science/antarctic_slang.php) - Common name for colds / flu contracted by new arrivals to the US McMurdo base. Most common with a large entry of new people bringing a large influx of fresh germs. Any germ-related illnesses in Antarctica are rare in the winter as the base personnel have either had the illnesses by then or are immune to them. The longest continuous period of my life free of colds and flu was when I was in Antarctica. Am.
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So you have both possibilities: insulated community and no contacts, all well and good. Insulated community and visits now and then, and viruses will spread like wildfire.
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[Question]
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We Eldar are a beautiful race that have a maximum life span of 500 years. We are stronger, faster, more intelligent, sexier, and frankly just superior to you humans in every way. However, we cannot reproduce as often due to biological reasons, as our children are born a few decades apart from each other. This prevents us from out-competing other lower life forms, who breed much more quickly.
This creates a problem for our species. It is very difficult to bounce back from an event which kills a large number of us. If there is a biological plague that kills a few million, or a war against another race in which many of us die, or even a natural disaster, it takes a long time for our species to replenish it's numbers. During this period, we become vulnerable to other lower species who would seek to take advantage of our predicament.
How can the Eldar prevent this from happening and compete with savage humans with this kind of weakness?
[Answer]
There are a few things you might want to do
**Breeding Programs**
I don't know what kinds of social customs the Eldar may have, but they are facing extinction. If they are *ahem* mechanically similar to humans, then you need to focus on the female being as productive as possible. So regardless of any life mate bonds, you need to make sure that every female becomes pregnant just as soon as she is capable of it. If the cycle is one of years, well, try to get that scheduled, so to speak so you have as little time wasted between pregnancies. You also need to make sure that the number of females pregnant every year remains relatively constant. You want this so that you don't have population waves and that as the youngsters come of age they add to the potential breeding pool at a steady stream. In addition, infertile males are yanked from the program as quick as possible. You may also want to stop exclusive pairings to add that little bit more to genetic diversity.
In addition, No more Nobility! You need to be a strict Meritocracy. Gender should not be a factor.
**Women and Children First**
Make the defense of the Women and Children absolutely paramount. Males can be replaced without slowing the breeding process, but females cannot. Put the women in the defensible central keep. The Men man the walls, etc. Children are protected alongside breeding age women. Older women should acutally train and study harder because they go back to the feild, so to speak, when they can no longer bear children.
**Other defensive strategies**
This is a bit of a hodge podge, so lets start small and work out. First, everyone learns to fight. Men, Women, doesn't matter. In fact, combat training should start young and ONLY differentiate when the young ladies can start to breed Even then, they should devote at least some time to combat training in between child rearing duties. Males to train continuously throughout their lives. This is not to say that they go full on Spartan, but things like weekly combat training classes, maybe structured like the national guard, be compulsary for everyone. That way there is still enough time to do everything else like building, agriculture, etc.
For Buildings, learn to build relatively small but strong fortified castles. When the population of a few towns gets to a certain point, a group from each joins forces to go out and found a new one. Make sure that some sort of communication link between the castles is an inherent part of the construction of each colony. This makes sure that if one is under attack, they can get help from nearby castles. it also avoids the whole "eggs in one basket". If plague hits one castle, you can quarantine it. If there is an invading force, they would have to stop to lay seige to a series of smaller fortresses, which is very costly and time consuming.
Depending on the Eldar's numbers, this may just be whistling past the graveyard. It may just be delaying the inevitable, but it might work
[Answer]
The simple solution is to kill all those lower species before they become a threat. If that is the threat you are worried about that is what you need to attack.
Alternately you can tackle the preceding threats. Disease and natural disasters can best be dealt with by dispersion. If you have multiple self sustaining realms that have limited interaction with each other, natural disasters are unlikely to destroy them all and the ones that survive are likely to recover.
Lack of dependencies also makes them resistant to cascading failures of political and economic systems and even if some fail, others should be able to save themselves.
This would basically mean that they are organized in fairly small realms practising [autarky](https://en.wikipedia.org/wiki/Autarky).
Unfortunately, as I expect most readers already noticed, this will make them vulnerable to being conquered one by one by external threats that have no problems in forming larger political and economic entities. Killing all of the inferior pre-emptively really is the best solution.
Alternately, the realms could despite autarky form very strict defensive pact that essentially forces everyone to band together against external threats. It would also have strict rules about what kinds of offensive wars are allowed. And also obligate everyone to enforce the rules if somebody tries to ignore them. This would not really work with humans for any length of time I think but Eldar are superior so maybe it would work better than the Holy Roman Empire or the Delian league worked for humans.
[Answer]
The strength of the race is shared amongst all Eldar, such that when one Eldar dies, their strength is bequeathed to all of the fair-folk, ther lifespan and any magical or fay abilities (eg. glamour, stealth) would similarly be shared amongst the survivors.
The Eldar are not as other races, their need to mate is amplified by the crisis of being few in number, their reproductive vigour could increase correspondingly, should the author desire.
This has the net effects that when the numbers are fewer, the individuals are more formidable and stronger and more magnificent to behold - yet when the numbers are greater, they would be no longer quite so superior in every way - in fact, given sufficient time to breed a large enough population they'd hardly be distinguishable from us poor human stock, apart from a telltale oddly shaped earlobes.
Humbly submitted by a human ally of the Eldar.
*Answer inspired by [this answer](https://worldbuilding.stackexchange.com/questions/112484/why-wouldnt-elves-be-the-dominant-species/112553#112553) to a previous question*
[Answer]
Diplomacy. Make alliances with short-lived sentient species, arrange society such that neither the Eldar nor the shorter-lived sentient species are considered indispensable. Make your species' survival important to the survival of others.The Eldar can serve as teachers, historians, scientists, guides, caretakers, religious leaders, advisers, political leaders, et cetera, in exchange for enjoying friendship and protection by humans. (But you might want to lose the superiority complex; that's only going to breed resentment, which won't work well here.)
[Answer]
The answer to this depends on the level of (technology/magic) of the Eldar, and if they can interbreed with other species. If they can interbreed, then get those handsome males cracking on creating a servitor subspecies with higher reproductive rates to do the dangerous work. If not, then cloning/changelings can directly make more Eldar (use inferior races as hosts-this is how elves did it in Terran mythology). Become withdrawn and extremely conservative! Females should all be sequestered from alien contamination. Males are unimportant except for doing dangerous stuff. Fight with robots/golems to do the dirty work. Engineer an orc-like servitor race to do the dirty work (what could possibly go wrong?)
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[Question]
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In this answer <https://worldbuilding.stackexchange.com/a/25219/50641> (to the attached question) one of their counter points was "oh, crows use tools, therefore, human advantage negated".
That got me thinking, could crows build a spaceship?
Obviously not with their current level of intelligence, so I propose the following scenario.
A trickster god (we'll blame Loki) has transformed every member of the human race into a crow, and set out a challenge for us. If we can land a crow(man) on the moon, grab a relatively small rock (say, one pound) and return it to Earth, we will be restored to our original form (and we'll all get ice cream, yay!).
Some ground rules.
* Crowmans are completely identical to crows (or ravens if that's more
convenient/thematically appropriate) biologically, but they have the
full intelligence, personality, and skills that they had while they
were human, without needing the requisite brain matter.
* Crowmans either speak some variant of crow that is functionally
equivalent to their human language, or just are capable of speaking
that language intelligibly regardless of whether a real crow could
actually pronounce all of it.
* Lifespan. The crows also gain the benefit of a human length
lifespan, if it is necessary.
So, would the crowman race ever be able to succeed at this task? Would they even be able to survive?
[Answer]
Yes they would, but by the time they get there would they want to?
Changes like this usually start with a lot of death, this is no different. Let's assume Loki has been friendly enough to make sure the crowmen can completely control their body and to open any doors, windows and entrances we need just to get in and out of our homes, work and facilities. From a quick search Crows seem capable of surviving in a range of hot and cold climates, so let's assume most crowmen survive their chosen environment despite suddenly not being able to wear their normal protective clothing. Now we still need to watch out for all the birds of prey that might want to eat us (and all the cats, dogs and other pets that don't have a problem killing/eating crow), and we are now surrounded by machinery, homes and tools all build for humans. Food is going to be hard to get by and many many crowmen will starve.
Humans are resourceful, so the crowmen will organize and try to start rebuilding society. This means repurposing what tools they can, and starting to recreate societies: Reinvent homes for crowmen, creation and gathering of food, construction of tools and generation and transportation of consumer goods. They will likely commit genocide on several forms of bird of prey until these birds stop eating the crowmen, but humans aren't very concerned about mass-extinction on the best of days and if it's a creature that's actively killing them any qualms about murdering every last one go out the window.
Since most infrastructure of the human empire is useless (although the cabling and pipes already laid down will be useful) the crowmen will need to rebuild just about everything. Here they hit another one of their big hurdles: Hand-eye coordination. Crows have less of it, as they either use their beak which makes seeing what they are manipulating a bit harder or they use their claws and can only really use one eye at a time to see what they are doing.
Another big hurdle is transportation. Humans load in stuff by hand all the time, on trains, trucks, boats, lorries, planes, from a conveyor belt into a box... All that is a lot harder for a crowman, especially for larger parts that need manufacturing. This means a far larger reliance on tools and machinery to do the carrying and moving for the crowmen.
As you can imagine it's going to take several generations before crowmen are back to a space-age civilization. They'll get there eventually. But when they have that technology... Do the crowmen of that time want to be human? Humans can't fly, they'll have technology all build for small crowmen and not for large humans. The generations that get the choice have all been raised by crowmen and have only ever known to be crowmen. I think it's more likely that they destroy any chance of turning back to humans. Having human intelligence in such a small body that can fly is probably incredibly useful in the long run, if only for how much food you need for the world population.
[Answer]
It will be a great challenge.
First of all, crowmen would have to save as much of human knowledge form disappearing. Transformation event would cause human civilization to collapse, as crowmen would not be able to use most of human tools. Most of technology would be able to function, but the process of adaptation will be hard, and crowmen civilization may fully collapse right away.
For example, we can construct a car that a crow can drive - but that's a sizable project even assuming that it's performed by humanoid people.
After crowmen civilization will hit the bottom (which can be as deep as stone edge), it will bounce back. This time, all inventions and conveniences will be built for a crowman user.
But here lies one potentially insurmountable obstacle. Human lifespan, even in harsh environments, exceeds 30 years. Lifespan of common raven is 10-15 years. Unless crowmen live as long as humans, young crowmen will not have enough time to get an education. Crowmen civilization may get stuck at renaissance level because their Newtons and Galileos would have a very short time to make a contribution.
Assuming crowmen would be able to overcome this obstacle, there is no reason to think that building a space rocket would be impossible. So, indeed, there is a chance for crowman to walk on the moon.
But then... crowmen will be changed back to men, and civilization will tumble again - because people can't use crow tools.
[Answer]
I don't think that enough crows will be able to cooperate enough to figure out what they need to do to design the tools they'll need to make a machine that can make a machine to fly to the moon.
Their only useful appendage for manipulating things are their bills. And, assuming that there were round door knobs left on the planet, and they could operate doors by cooperation, every single task they needed to do would be greatly complicated by the limitations of their physical forms. I think they could still program effectively since most programmers hunt and peck for keys anyways, it would not be a real change. But, welding and metal work and smelting are not forms a crow is well suited for. They'd need to make robots for everything, probably even opening doors. I think the investment in working around their own limitations would consume their available time to complete the project.
If they lived long enough, you are in the equivalent situation as an infinite number of monkeys with an infinite amount of time and then, yeah, they could.
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[Question]
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**The Society**
The society in question is feudal in structure. The most advanced widespread technology defining this society is the flintlock muzzle-loading firearm (I'm undecided as to rifled or not, but leaning towards not). Their capabilities do not extend to mass production of these muskets and pistols, with the vast majority being handmade by craftsmen. The difficulty and expense with which they can be produced is roughly equivalent to the production of knightly accoutrements in the High Middle Ages.
The social structure consists of serfs and bondsmen at the base of the hierarchy. Above them are a landowner/warrior class defined by possessing the wealth to purchase and maintain a firearm (analogous to knights). Above them are the lords, with larger landowning privileges and access to greater armouries, and a feudal king above them.
So basically mid-feudal Europe, but with muskets instead of knights.
**The Environment**
The lands this society inhabits are largely analogous to the more difficult areas of northern Europe. The landscape is, by and large, difficult to traverse as it is heavily wooded and mountainous in many areas, making the use of heavy cannon difficult. It's bordered by high mountains on one side, sea on another, and steppe on the last (inhabited by steppe-nomads with similar access to firearms).
Most of Finland might not be a bad analogy, or perhaps areas surrounding the Carpathians.
**The Question**
What military structure and army composition might arise in societies in these circumstances?
I've got a rough idea of small feudal levies armed with hand weapons, acting as anchoring blocks for groups of skirmishing nobles. Use of cavalry might be difficult given the terrain.
Would this be realistic, or are there significant differences to this structure that firearms would change?
If this is too broad/opinion-based please let me know and I'll fix it!
[Answer]
I don't think you are going to witness much change, for the Following reasons:
1) Massed fire is one of the best uses for a musket in large scale conflict. You can only shoot the thing so fast and smooth bore guns are less accurate than rifles. Aiming one to hit a target is more of a suggestion than a directive, if you know what I mean. It does have enough power to penetrate armor within about 200 yards, maybe less. Bows and crossbows are effective to an equivalent range.
2) One of the big advantages the Musket gave to armies was that you could issue one to just about any ploughboy, and within a very short period of time, he would be an effective soldier. It took years to train good archers. It took less time than that for crossbows, but crossbows relied on muscle power to draw and load, so only the fairly strong would be used in that role. A chemically powered weapon like a musket, you hand some kid the gear and give a few days of instruction and you have someone who would be good to stand in for massed fire. In your scenario, though, your nobleman is NOT going to hand some ploughboy a very expensive personal weapon.
3) You could have the nobles engage in the sport of *sniping* if you gave them fine rifles instead of muskets. This could be the preferred method of combat for the truly wealthy. Less wealthy would still be mounted knights in a heavy cavalry. Even though Heavy cavalry is less useful in mountainous terrain, it still has it's place. The higher nobles would go out, find a good spot, and try to take out an opposing general from 300 yards.
4) If you want your warfare to lean toward ranged weapons, things could lean toward crossbows. Remember the goal is massed fire so that infantry is seriously weakened before they can get close enough to poke at your squishy bits. Since the training cycle is reduced, despite losing some because they are just a little too weak. You could get a lot of crossbowmen ready for a battle in a relatively short timeframe. They aren't going to be marksmen, but they can stand shoulder to shoulder and throw lots of sharp wood at the other guys. Of course way back in feudal societies, you may not have given them even crossbows, you might just give them a sharpened stick and tell them you hope they don't die (look out for the burning pi...oh dear).
I see your army going out, your conscript serfs pulling the baggage train and you occasionally giving the strongest a crossbow (no bolts, of course) to train with, learning to load aim and fire. The rest of your peasants would get a sharp stick, crappy jobs and occasionally food. They also get to walk out front to find potholes, man traps, and to draw enemy archers. Your heavy cavalry and archers are arranged beside and behind the column, surrounding your noble and expensively armed general. an experienced hunter might ride ahead to scout some suitable locations for the Lord to hide and take pot shots at the enemy.
It could work
[Answer]
The real issue with firearms is they produce a quantum change in warfare. In our history, there was already an "Infantry Revolution" sweeping the battlefields in the late 1300's and through the 1400's, with expensive, exquisitely trained from boyhood fighters like knights and longbowmen being replaced by levees and city men using weapons which were effective against knights, Samurai and so on, combined with tactics that allowed the effective use of these weapons by relatively untrained men.
Crossbows could deliver @ 200J of energy against targets, allowing peasants or city tradespeople to take down armoured knights, and crossbowmen could be protected by formations of pikes which prevented knightly charges and even made it difficult to attack on foot (and Swiss pikemen learned to charge against the enemy, totally upsetting the balance of power).
Firearms made the Infantry Revolution permanent, since even an arquebus in the late 1400's could deliver 1000J of energy to the target; an *order of magnitude* greater than any muscle powered weapon. Cannon had the same sorts of orders of magnitude difference compared to catapults, trebuchets and so on, making walled castles unviable, and putting power in the hands of those who had enough wealth to afford an artillery train (few nobles could face the Royal artillery train, the King simply had much more wealth).
While you have essentially set your story historically in the mid 1400's (firearms are expensive and still somewhat rare), this state of affairs isn't going to last. The obvious advantages of being able to rapidly field large formations of men *without* having to pull them from the fields and workshops for prolonged training is what gave impetus to the Infantry Revolution in the first place, and anyone who could get firearms went to great lengths to do so.
Gunners would therefor be grouped in small units. They would be treated much like crossbowmen, and be placed along the flanks of pike or pole arm formations, in order to have protection from enemy cavalry charges or advancing infantry. After firing, they may even retreat behind the pike formation in order to reload, or move to a new position to fire on targets deemed to be advantageous. Cannon will be used either to fire on fortifications, or preset to fire where the commander believes the enemy formation(s) will appear. Since cannon were not very mobile, the ability to move them around the battlefield during an engagement isn't an option.
[](https://i.stack.imgur.com/MEMe8.jpg)
*Fighting in the 1600's. The formations and tactics are refined from those of the late 1400's, but a solder from the 1490's would still recognize this formation*
[Answer]
[](https://i.stack.imgur.com/zDVln.png)
*Do you know these bad boys?*
They may be the unit you want in your world. Cuirassiers (first appeared in XV century). Their equipment varies, but in your timeline they would be heavily armored (almost like late medieval knights) but instead of lances they would have set of pistols (and maybe even a cavalry rifle).
**Why them?**
Well, they are some kind of evolved form of armored knights. When the halberd become popular, lances were no longer efficient weapons because of its range. Then the cuirassiers came, using firearms while charging instead of the lance. The range was obviously better.
Then [caracole](https://en.wikipedia.org/wiki/Caracole) happened. It was like riding in circles in front of the enemy unit - you are close, you shoot, you drive away to reload, repeat. In our timeline it wasn't so effective, because infantry had superior firepower.
*And there we have this one, implausible thing. Infantry still would have greater firepower with crossbows and bows. But it may be ok, as in our timeline there were also crossbows and bows while heavy cavalry still existed.*
Because firearms are very expensive, this would be a more direct evolution of knights than in our world. They'll be "super knights", who are more safe while charging because they use firearms instead of lances. Then the caracole will appear, probably around the same time as knights will start disappearing. Cuirassiers would be elite units, recruited from knights (and later nobles) because of the cost of equipment.
As time in your world passes and firearms become more mass produced, cuirassiers would evolve similar to our timeline, becoming a more sword focused cavalry with guns, than a guns focused with sword cavalry (as Gustavus Adolphus did with his cuirassiers).
[Answer]
Well, the fact is that gunpowder is credited as one of the reasons behind the fall of feudalism.
With gunpowder you can have cannons, and cannons make short work of castles, so the king has a way easier time forcing any feudal lord into submission. Before cannons, the feudal lord could just entrench in his castle and wait for their enemy to leave due to lack of money or supplies or because of illness, so kings had to think twice before acting against them.
Additionally, guns are expensive, which means that only kings and a few other main nobles (who would soon become kings) can maintain them. Remember that you need to keep constantly employed a corps of artilleryman, gunsmiths and the like, and that is expensive.
[Answer]
The military would probably be a bunch of small units that fight using gorilla warfare and stealth. Each team would probably be largely independent from the others and common practice would be to send them out for long periods of time. The objective would be given before they set out into the wilderness and if the team did not return within a week of the designated return time, they would be presumed dead.
They are survivalists and marksmen. They know how to survive on their own and are hard to track due to their small numbers. I could add more, but I don't really know how to explain them in greater detail.
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[Question]
[
In the story I am writing, the United States never pulled out of Vietnam, with the conflict continuing into the present day. During this time, the United States decided to use Vietnam to secretly field test illegal bioweapons (since the [USBWL](https://en.wikipedia.org/wiki/United_States_Army_Biological_Warfare_Laboratories) was never disestablished), one of them being a genetically modified version of [Ophiocordyceps unilateralis](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis). The modified version of the fungus was designed to do two things: make the host kill and eat members of its own species, and use the nutrients from the consumed flesh to produce spores to spread to new hosts.
So, my questions are:
1) What modifications would be required to allow Ophiocordyceps unilateralis to infect humans?
2) How would Ophiocordyceps unilateralis modify the host's brain to cause the host to exhibit the behaviours stated above?
[Answer]
As far as I’m aware, our understanding of how mind control works is essentially based on hormones and chemical signals. These are sent through the host’s nervous system against their will in order to create the desired reaction. Imagine having an assembly line that delivers numbers to a terminal and the number “3” will cause a specific reaction. The facility runs as normal, but someone has broken in and is constantly throwing 3’s into the system. You could essentially “control” something this way. A potentially dark side effect of this is that the host is completely aware it is being manipulated, but is powerless to do otherwise.
Additionally, a species of mind controlling parasite called leocochloridium which infects snails sends additional signals to castrate the snail. This ensures more energy available to be used for the parasite’s intentions. Infected snails are effectively “super snails” and travel much faster than normal. Your form of cordiceps could do something similar to the infected host; shutting down additional bodily systems to provide energy for other areas. Basically, after all this, you’re looking at very primal, hunger-fueled monsters built for one single purpose: hunting. Hope this helps.
[Answer]
After reading [this](http://news.psu.edu/story/277383/2013/05/21/research/getting-bottom-zombie-ant-phenomenon) article, I have an idea.
It's mentioned that there are probably about 1000 different kinds of Ophiocordyceps, and that it and ants have adapted over time both in arsenal and defense. It behaves similar to that of yeast that is found in beer.
To answer your **first question**, I think it would be an interesting idea in a story to find a way for people to have a yeast infection, perhaps through beer (any other ways, sure).
How would it modify the host's brain **(second question)**? The host would have to be dead, with significant fungal cells in the body/brain. Then, similar to the ant, the human (now dead human) would behave the same way:
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> *While the manipulated individual may look like an ant, it represents a fungal genome expressing fungal behavior through the body of an ant.* - quote from article link above
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In conclusion, this kind of outbreak would start by people drinking an especially yeasty modified beer that will cause a kind of yeast infection in the brain... killing the host... and the behavior is fungal in nature.
So your characters should think twice about drinking that cheap skunky beer.
[Answer]
First, you would have to engineer a Ophiocordyceps species that is **interested in human targets**, which may be a challenge as human are significantly bigger and might be harder to infect, or at least maintain the infection. The parasite would have to be able to either **neutralize the host's immune system or avoid it**.
However, since humans are much bigger animals, the fungus would probably have access to much more nutrients and therefore **produce much more spores** (or at least you could engineer it to do so).
To infect more humans, you could "teach" the fungus to lead the host to ventilation systems but it might be a bit cold and dry for the fungus to grow. Doing so would allow the infection to spread into a whole building. It needs to be able to find a "comfortable" place to grow from which it can spread its spores. From what I know, it needs to be a **shady, humid and warm place**.
As for the mind control, I do not have sufficient knowledge to know in details how the fungus controls the host. Maybe **it could act on synapses to modify brain signals**.
I am not sure if the fungus would benefit from an aggressive host. Judging by the original fungus' behaviour, it kills the host once it wants to spread its spores. Maybe it is because it needs as much energy as possible to create spore. If so, **maybe the fungus would only need to consume part of its host to start producing spores** and **aggressiveness would allow the host to get closer to non-infected humans** and ensure the spread of spores directly on non-infected individuals.
[Answer]
Have you considered making it a sexually transmitted disease?
The kind of ant infection you are interested in is very unlikely to scale to a whole human body. It operates not through hormones or neurotransmitters, nor brain manipulation, both of which are more likely to work on a large complex organism. Instead it overrides existing motor controls and sends signals to ant muscles directly, while the ant might be fully conscious. Even if it somehow gains the processing power to navigate a human body through complex environments, it would be a slow and inefficient process and give people too much time to notice and react. Humans also have a more powerful and very different immune system.
Instead, shallow fungal infection is much easier and faster, and much less alarming than total body control. To achieve the goal of killing and eating humans, it could be sexually transmitted and destroy and consume human reproductive cells and fetuses, which at least some people consider human beings - even if you disagree, the goal of destroying humanity would still be achieved. To speed up spreading, it could use its muscle-controlling powers to affect human sexual behavior and make its host continually stimulated and have more pleasure/last longer, so they will have sex with more people(but not so obvious to be alarming), and this would be easier and require less "intelligence" than controlling the whole body. People may even willingly get infected even after it's found out if it doesn't otherwise negatively impact their lives too much. If you are being nice, just stop there. If you want to make it slowly destroy the host or turn them into classical zombies, this method can buy you time.
A zombie apocalypse doesn't have look like "The Last of Us". In some sense, what the organism's behavior is helping to reproduce and evolve is what's really in charge. We could be living more or less normal lives and still be scientifically zombies if all human achievements and desires and relationships would only serve our invisible fungal masters.
[Answer]
Zombie, Vampire and Werewolf myths are all loosely based on [Rabies](https://en.wikipedia.org/wiki/Rabies) which is a much shorter biological reach. That fungus is particularly adapted to infect specific ant species, and you have to go from that all the way to humans while rabies already does some of what you want and it works on most mammals already.
In humans, that fungus' intrinsic workings would have to work on fundamentally different:
* circulatory system and chemistry
* nervous system
In addition, with increasing degrees of certainty, I don't believe ants have
* dedicated lymphatic systems
* internal skeletons
* medicine
It's a scary fungus with incomprehensibly complex interactions, but ants are far simpler than humans. Perhaps rabies gets some DNA from Ophiocordyceps unilateralis or vice-versa. One could never hybridize the two because one is a virus and one is a fungus.
[Answer]
If your pathogen shut off the satiation circuits in the human brain it could create voracious humans who would want to eat everything. If it also damaged the disinhibition function of the fore brain and the mirror neurons that create empathy with others, it would turn humans into voracious eaters who couldn't help themselves and wouldn't even feel bad about it. If it could also make other humans smell absolutely delicious, watch out!
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In my story, set in the far(ish) future, humanity discovers a way to extract energy from black holes (perhaps via the [Penrose process](https://en.wikipedia.org/wiki/Penrose_process)?), which sparks conflict as various factions attempt to take control over previously useless and dangerous but now suddenly valuable black holes. This energy is extremely valuable because warp drives for faster-than-light travel require massive amounts of power, which made them impractical before the proliferation of Penrose process power plants.
In order for this to make sense, black holes would have to be a better source of energy than whatever humanity was using before, which I assume would be Dyson spheres/rings/swarms/etc. gathering energy radiated from stars.
To see if this is plausible, I attempted to compare the energy output of a Penrose power plant vs a Dyson sphere around the sun.
According to the Wikipedia article about the Penrose process, up to 29% of a black hole's mass energy can be contained in its angular momentum. So, assuming a black hole with the mass of the sun (which I know is too small to become a black hole, but I wanted to compare apples to apples), the total amount of energy that can be harvested from it is $(0.29\cdot1.989\times10^{30})c^2 = 5.18\times10^{46}$ joules.
For comparison, the sun emits a total of $3.9\times10^{26}$ watts.[2](http://www4.ncsu.edu/~franzen/public_html/CH437/lec1/pdf/earth_T.pdf) Over the 5 billion remaining years of the sun's life, assuming its energy output remains constant, it will emit a total of $(5,000,000,000\cdot60\cdot60\cdot24\cdot365)(3.9\times10^{26}) = 6.15\times10^{43}$ joules.
So the black hole has over 800 times as much energy to harvest! But the real question is, how quickly can that energy be harvested?
According to Wikipedia, an object's energy can be increased by up to 20.7% using the Penrose process. That means the equation for how much energy we can get from a given mass is $0.207mc^2$. So, the amount of mass we need to toss into the black hole per second to match the sun is $\frac{3.9\times10^{26}}{0.207c^2} = 2.1\times10^{10}$ kilograms per second. But only half of that mass actually falls into the black hole, the rest can be re-used. So only $1.05\times10^{10}$ kilograms are consumed each second.
How much mass is that? That's about 1.75 Great Pyramids of Giza every second. At that rate, the mass of the moon would be used in $\frac{7.3\times10^{22}}{1.05\times10^{10}} = 6.95\times10^{12}$ seconds, or about 220,000 years.
For the sun, it would be $\frac{1.989\times10^{30}}{1.05\times10^{10}} = 1.89\times10^{20}$ seconds, or a little under 6 trillion years.
Based on the math, it seems plausible. (Assuming you can toss stuff in fast enough.)
So my questions are:
* If a civilization is not advanced enough to harvest energy from black holes, are stars the best source of energy?
* If a civilization *is* advanced enough to harvest energy from black holes, are black holes the best source of energy?
* Is the Penrose process the best way to harvest energy from a black hole?
By "best" I mean produces usable energy the quickest. I know matter-antimatter annihilation would release energy extremely quickly, but you have to create the antimatter first, which uses a bunch of energy. (In my universe, humanity never figures out how to create antimatter efficiently enough to get a net gain of energy by annihilating it.)
[Answer]
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> If a civilization is not advanced enough to harvest energy from black holes, are stars the best source of energy?
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Certainly not. There are quasars and pulsars and nova and heaven only knows what other sources of energy are out there. Quasars and blazars1 may be a bit too rare to be practical. It's like always having to drive a 40 mile round trip to get gas in your tank. Pulsars produce a ton of energy and are more frequent. In the long run, suns may have the lowest collectible energy density, but they're so honking common that practicality wins out over efficiency.
In reality, your people would use a variety of sources. A passing quasar for a quick top-off would never be missed — but a star if you must 'cause it's right over there.
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> If a civilization is advanced enough to harvest energy from black holes, are black holes the best source of energy?
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Ignoring the issue of practicality (which will always require multiple energy sources 'cause those folks on the rim are a long way out and that makes refueling very impractical), then quasars and blazars are still your best energy sources, but they're more rare than black holes.
OK, You really can't ignore practicality. If you're half-a-galaxy away from the nearest black hole it simply doesn't matter if you can harvest or not. You're not going to spend the time and energy just to obtain the better energy density. If it takes less time to sit by a star than to travel to a black hole, you'll park that beast in orbit and get a tan.
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> Is the Penrose process the best way to harvest energy from a black hole?
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This is, frankly, an impossible question to answer. (And don't believe anyone who tells you otherwise. No one can prove that one theory is better than another.) The Penrose process is theoretical. Hawking radiation, [first theorized in 1974](https://www.technologyreview.com/s/420940/first-observation-of-hawking-radiation/) only saw the first light of proof in 2010. Who knows when the Penrose Process will be proven, if ever? What's the value of claiming one theoretical method is better than another? What happens if you write your story this year only to have the Penrose Process disproven next year? You see, the problem is, you're treating hypotheses and theories as if they're right. Maybe they are. Maybe they aren't.
**I have a couple of favorite stories that are getting harder to read because the author depended on being too realistic, too "hard science," and the science changed. Some people are funny, they think what we "know" today (even when it's only just theorized) represents the end-all of knowledge. Knowledge changes, science changes, theories come and go. If you stick to today's proven facts, you're safe. But the more theoretical and unproven your story's critical science, the more likely the story won't stand the test of time.**
*That's the value of* fiction. *It's nearly impossible to disprove fiction (e.g., Star Trek transporters) and once the fiction becomes popular people start working toward making it work (e.g., Star Trek transporters). But take an actual theory that becomes disproven. Now your "history" is wrong and people will stop liking the story. Yuck.*
Which is a fancy way of saying, have fun discovering whether or not your fictional society can harvest black holes, but when it comes to the actual science behind doing it, you might want to stick with "Lieutenant, open the collectors and start filling our reserves."
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1 *Please forgive me for forgetting the quasars and blazars are believed to be special cases of black holes. Mentioning them at this point in the text is improper as the OP was asking about "what if we can't harvest black holes?" If you can't harvest black holes, you can't harvest quasars and blazars, either. However, I didn't bother to rewrite the paragraph because I suspect y'all'll understand my point (and, having found a good reason to write "y'all'll," I couldn't pass it up). Cheers.*
[Answer]
Black holes are very interesting, and can be [farmed](https://www.youtube.com/watch?v=Qam5BkXIEhQ) for energy, as well as used for other purposes. There are some theories that suggest a Black Hole's event horizon could serve as a sort of [civilizational hard drive](https://worldbuilding.stackexchange.com/questions/13885/how-to-create-and-use-a-black-hole-computer-drive?rq=1), for example.
The issue isn't if black holes are effective energy sources or not, but the logistics and infrastructure needed to use them. If you have to travel 30,000 light years to get to [Sagittarius A\*](https://infogalactic.com/info/Sagittarius_A*) (the central black hole at the centre of the Milky Way Galaxy), and then [disassemble dozens of stars](https://www.youtube.com/watch?v=pzuHxL5FD5U) to create the structures needed to surround and contain the black hole for energy extraction, then you have a very long project ahead of you, and your subcontractors will be busy for millennia.
Smaller black holes orbiting in the Galaxy itself will have similar, if smaller issues.
So in effect, you will have a situation similar to the builders of hydroelectric power systems: the best sites for dams and power stations might not be located very close to where your customers for power actually are. (For the purpose of the question, I'll handwave the need for the equivalent of high power transmission lines from the black holes to wherever the power is needed).
Unless you absolutely require power on this scale, it seems much more practical to simply build [Dyson swarms](https://infogalactic.com/info/Dyson_sphere) around the ordinary stars and harvest the energy from there. This is often known as a K-2 civilization, and represents a fairly straightforward and accessible way to generate power o the scale needed for a galactic civilization.
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(By coincidence I was finishing a section of my book dealing with mining black hole energy today)
Harvesting energy from stars is *easy*. But it turns out that the tech (Dyson spheres) you need for it allows harvesting energy from black hole accretion in a stationary way, and this can be very efficient.
No, the Penrose process is not the best real or theoretical method of energy harvesting.
More detail, and a suggestion for a theoretical but science-based cool way of tapping black holes:
The Penrose process extracts angular momentum from a rotating black hole. It is not an easy trick to pull off, but one can do it in various ways (particles, superradiance, matter-antimatter reactions producing pairs of gamma ray beams where one is sacrificed and the other picked up outside...). However, eventually the angular momentum will run out. It is not a renewable source, even though it is big.
The most efficient way we *know* can extract energy from matter and a black hole is accretion disks and jets, since we have observed them. Matter falling into an accretion disk is losing its potential energy as it spirals in, radiating it away. We have good reason to think that the mass-energy conversion efficiency is up to 5.72% for stationary black holes and up to 42.3% (!) for rotating black holes (neutron stars give about 23%). By comparison, fusion is just 0.075%, and stars worse. That energy can be collected using a Dyson sphere (a fairly standard one, if high temperature, for a stellar mass black hole; a very big 1000 AU one for galactic black holes - as you get close to the Eddington luminosity I recommend carbon-tungsten statites or the alloys related to Ta$\_4$HfC$\_5$).
But there is more! The accretion process produces jets that can be about as luminous as the the disk itself thanks to complex electromagnetic effects in the swirling plasma. This is basically a Penrose process but electromagnetic (the Blandford–Znajek process), and possible to replenish by adding matter with angular momentum to the disk. That energy can also be collected using suitable megascale engineering (think giant coils).
Catching gravitational radiation looks very hard (weak coupling to matter), even though up to 1/8 of the masses of merging black holes are emitted in one burst.
Here is the thing that might make the story/worldbuilding fun:
Hawking radiation is a mere trickle, and mostly of interest for far, far future civilisations when the universe becomes cold enough. However, it can be boosted! [In this paper](https://arxiv.org/abs/hep-th/0012260), Frolov and Fursaev show that if you dangle cosmic strings nearly onto the event horizon of a black hole each string will emit about the same amount of Hawking radiation as the entire hole. For the right kind of thin strings this can boost the hole output by $10^{31}$ - enough to make a solar mass black hole produce 900 Watt, and smaller ones far more. Of course, solar-mass black holes are about the lightest that can form today, so you need to seek out the rarer primordial black holes that formed during the Big Bang.
So my suggestion is that a recent discovery of a way of making cosmic strings (cool objects on their own) enables tapping primordial black holes, triggering a rush.
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1. An insufficiently advanced society such as our own Class 1 society may want to consider research into the harvesting of vacuum energy as one scientist hypothesized that the amount of usable energy in the volume of a coffee cup might be enough to boil an ocean and that would see to be a good starting point for harnessing large amounts of usable energy
2. A sufficiently advanced society perhaps classified as a Class 2 society should have other alternatives beside black holes including more common cosmological events like neutron stars and quasars
3. As has been suggested by others, there may not be sufficient data to determine whether the Penrose process could achieve your goal but the name sounds good if you're looking to give your process a title.
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> In my story, set in the far(ish) future, humanity discovers a way to extract energy from black holes (perhaps via the Penrose process?), which sparks conflict as various factions attempt to take control over previously useless and dangerous but now suddenly valuable black holes
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Black holes have a significant problem -- **availability**. And to be able to use the Penrose process, a black hole is not enough - it must be a *Kerr* black hole, one with angular momentum that you can harvest.
There is another possibility, harvesting Hawking radiation. If the theory is correct, a black hole radiates energy at the expense of its mass; the smaller the black hole, the faster it radiates, so that below a certain size a black hole starts evaporating faster and faster until it disappears in a flash of gamma radiations.
The equilibrium temperature of a Schwarzschild black hole is 6.169 10-8 times the ratio between the standard Solar mass and the black hole mass.
Also, emitted power is [inversely proportional to the square of the mass](https://en.wikipedia.org/wiki/Hawking_radiation), and a Sun-sized black hole would radiate 9 10-29 W. Suppose we want **one thousand gigawatts of power**, or 1012 W; if my calculations are correct, we need a mass of 1.8E+10 kg (18 million tons), which would radiate at a temperature of about seven billion K degrees - enough to photodisintegrate matter - and evaporate in 1.5 microseconds.
If a civilization *could* harness such a monster, you would have an incredibly compact form of energy, *reasonably* portable, which would continuously consume matter converting it into energy (and if the reaction got out of control, you would get an explosion of one jillion megatons when eighteen million tons of mass get converted to energy in less than two microseconds). Harvesting that energy would require very advanced technology, the black hole equivalent of [betavoltaics](https://en.wikipedia.org/wiki/Betavoltaic_device). Perhaps *clastovoltaics*, from the Greek word κλάστης "to break".
But how do you create a multimillion-ton black hole keeping it stable in the process? The safest way would be to start from a larger black hole and destabilize it by feeding it with antimatter. You don't need to bring them all the way down to twenty million tons - just start the evaporation process until it has reached a sufficient speed, then wait a suitable number of years while preventing the black hole from absorbing ordinary matter.
Now, stable micro black holes (the size of the Moon) would become a sought-after resource: you need to locate them, electrically charge them enough to be able to tow them (somehow!) near some *other* huge source of energy suitable for the production of antimatter, and convert them to matter-annihilation power cores.
Especially during the initial slow cooking period, when someone else has paid the huge location, towage and antimatter priming costs, and the black holes have started giving off mere microwatts of power but are still a long away from becoming difficult to control, it would make economic sense to try and *steal* them.
But to answer your question: *would* that be a better energy source than a star? It depends. Energy density is way higher, and it's far more portable and efficient. On the other hand, a star is not usually a few microseconds away from blowing you and everything else in a radius of several million kilometers to smithereens.
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You would be hard-pressed to find a better source than stars, if you can't use black holes. The only thing harvestable by that civilization that is bigger/has more energy than a star is a group of large stars.
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The problem with harvesting from black holes's momentum lies in how practical it is. One mistake and your equipment becomes impossible to recover/repair.
A safer bet would be to harvest from the accretion disc around a supermassive black hole. Those discs have temperatures in the order of millions of degrees an can be more massive than the biggest stars. [TON 618](https://en.wikipedia.org/wiki/TON_618) is a black hole of 66 billion solar masses, whose accretion disc **outshines its galaxy** - imagine the mass and energy of that disc.
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As you mentioned, that process can take up to 29% of the black hole's mass-energy. Absorbing its Hawkings radiation will eventually net 100% of its mass energy, but will take prohibitively, exponentially more time - taking all of the momentum energy may get you done well past the heat death of the universe, but even that would be only a fraction of the time needed to extract the whole energy-masss of the hole through Hawkings. So Penrose is still the more productive way to go.
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Theoretically, just dropping mass into a rotating black hole will release more energy than the Penrose process, since the mass-energy conversion has an efficiency of 42%, compared to 0.7% in nuclear fusion.
1. Based on our current knowledge, yes. There are many Dyson superstructures designed to leech the energy from a star. And the energy is sufficient for just about anything a civ that advanced can dream up.
2. Technically, yes, but here's the elephant in the room. Black holes aren't exactly safe. One tiny slipup, and you've got a seriously scaled-up Chernobyl. Equipment worth gazillions of currency units, gone in a flash.
3. Read the first paragraph.
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Magic isn't common, though it isn't particularly rare. This form of magic is based very much upon the emotional state of the user, where essentially the potency and type of the magic is dependent on the kind and strength of the emotion being felt. (If you are interested in the finer details of the system, they can be found in [this](https://worldbuilding.stackexchange.com/questions/82492/emotional-caveats-in-a-magic-system) question.)
In this world, a particular kingdom has created a culture with a heavy stigma against those who can use magic. They are almost universally hated by the population, and the government takes steps to capture and control them. (The populous would help any efforts because of this general hatred.)
**My question centers around this: how would they control them?**
Ideally, there would be little to no chance of rebellion. A couple of thoughts came to my mind:
1. A drug that serves two purposes, one being to induce a specific emotional state to facilitate more consistent and powerful magic, and the other to be extremely addictive so that they have to rely on the government to get their fix. This drug will make an appearance either way, but I'm not sure whether it will be a sufficient control on its own.
2. Capturing their families and holding them hostage. This seems to me to be a heck of a lot of work, and the amount of magic-users would make the amount of people they have to keep quite cumbersome.
To sum up, what is the best way for a government to keep control of a fairly large number of magic-users without resorting to capturing those important to them?
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**The government has their own magic users**
I know the people at large hate the magic users and the government might be even in power thanks to agreeing with this.
But governments and authorities can be a practical, and even hypocritical lot. Just as casinoes sometimes hire former cheats to try and spot cheating taking place on their premises, the government could hire their own loyal and powerful mages to keep down the other magic users.
Of course this leaves the problem of how to explain to the people why they are employing wizards while at the same time trying to repress them. This is all about "spin" - i.e. propaganda. Governments are good at this sort of thing. This doesn't sound like the most democratic of governments so this shouldn't be too much of a problem.
But then how do they prevent their own mages from siding with the magic users they are trying to control? - A couple of options:
* Appeal to their sense of patriotic loyalty
* Pay them well.
* Hire them from another country and so don't feel any ties to the magic users in this country.
* Convince them they are *protecting* the magic users, either from their own powers (which are treated more like an unstable mental condition), or from the hating public - i.e. we have to keep an eye on them or they'll be attacked by the mobs.
* Form an organisation who believes in their position, like the "Psi-Corps" in *Babylon 5*. Kind of similar to the point just above (protect by control), but also the realisation that there would be chaos from both the mages and the mundanes - in different ways - if mages were allowed loose. Magic is a dangerous power and so needs strict discipline. This also acts as a sort of ensurance - if you're a member, the chances of having fraudulent or exaggerated claims made against you by the public are greatly reduced.
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### Give them a job and their family safety - as long as the magic user submits to the government
Seriously. Just give them a job and promise them that they and their families are safe.
Your population hates magic users. That means your magic users will be prosecuted or at least discriminated. The same applies to their families. There is no need to hold anyone hostage, they are held hostage in the whole country.
But you can give them a job. Make them do the dirty work your normal people don't want to do for example. And thereby grant them and their family special rights. Make it a symbol of power to have for example a special emblem you can wear if someone in your family belongs to the parliaments magic users. If you are wearing this emblem/badge/... you get access to priority queues at the doctor, can buy things that normal people would need a license for like drugs or weapons, can send your children more easily to a preferred university, ...
Whatever is rare in your world can be gained by the family. As long as the magic user in question helps the government and submits to everything they ask from him.
And if your magic user runs away - you will require the family to wear a different badge. One that signals that the family member did something horrible and they will not only lose their privileges, they will get less access.
This is a way of luring them in and then indirectly holding everyone they know hostage. Easy to set up, not too costly and a great way to play with the emotions of your populace.
### @ArtificialSoul: "normal people would protest, because the magic useres who are employed by the goverment are not only a protected class but also get privileges - even if they do dirty work"
I don't think they would protest. Everyone would want a magic user that is employed in their family. And they would fear having one in their family that is not employed. They fear and hate the magic users, but they are locked away somewhere, doing work nobody else wants. It's a perfect way to make the population give you all the magic users without the costs for the program being too high.
**The magic users themselves are not a privileges class - their families who reported them are. The magic users themselves are priced beasts that are locked away as soon as they are detected.**
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## Make them hate their magic themselves
In short, make them see their power as something terrifying, and need to be controlled somehow. Then, the government can come in and "help" these people control their magic.
Create "accidents", and blame it to them. Maybe inject them with a drug that destabilize their emotion. A magic user may go "ka-boom", and the rest of the magic user society is advised to take a tranquilizer pill to make crush their emotion.
This will be very effective if in the accident the user killed their loved ones. Just repeat, and offer the "cure".
This is actually what happened in X-Men, if I remember correctly, though the government didn't create the cure to manipulate the mutants.
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"Control" in this case is a tricky word: does your government aim to simply monitor and track the activities of these people with magical abilities, or actually dictate what they do?
If it is the former, I imagine that a simple Registry of Magic Users would suffice: there seems to be little incentive for magic users to defy the system and it is unlikely that this level of supervision will meet with much resistance. The Registry could require every magic user to attend mandatory courses, stating what they are allowed/ not allowed to do, and also scheduled counselling sessions to ensure that their emotions are well-managed and thus not a trigger for random outbursts of magic. Of course, this does require some expenditure, and may not be supported by a public pre-disposed to hate magic users. Alternatively, this can be a "voluntary" process: google Black Ribboners from the Discworld Universe.
The latter would require rather more drastic measures, such as mandatory screening for magical ability at birth. If some technology exists that suppresses magical ability, perhaps some such device can be forcibly implanted in every infant detected to have ability, removable only upon pain of death. The government will be the only party able to temporarily unlock the device, allowing the wearer to use his/ her powers for as long as allowed by the government, and the device can be remotely re-activated when needed.
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Here's what won't work
1. Using families as hostages; not everyone's got a family and for those that do, not everyone loves their family.
2. Disinformation: you said this was one kingdom, so there are other nation states. Any lies or propaganda spread by your kingdoms govt about magic users would be quickly disproven by sources of news from other nations.
3. Drugging them; you'd have to be 100% effective 100% of the time, it only takes one to slip through the net
4. Using other magic users; you can't use the MUs to police themselves. All the "police" MUs will be on the other side of the baton one day, they'll need as much goodwill as possible from their neighbours and peers.
To be brutally honest, the only effective control I can think of is culling them when they're detected. Why would a government keep a lot of superpowered people around when they've got a big ole grudge to settle ? Unless the government has an active use for them in the here and now then killing them ASAP makes most sense.
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Bind their magic and enslave them with the promise of releasing it back to them once they have fulfilled their duty. Use [the Ludovico technique](https://en.wikipedia.org/wiki/A_Clockwork_Orange_(novel)#Part_2:_The_Ludovico_Technique) and the butterfly technique to create dormant sleeper cells ready at any time. Impose martial law, awaken magic users to enforce it, and boom. This would be the most effective way for them to control the magic population, as well as benefit from them. A magic user would grow up their whole life feeling that void inside them, that integral part denied to them. They would know it was there, and then be promised to get it back once their duties are done. I don't think there would be a single one who would resist.
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How do I create an absolutely isolated series of mountain alpine valleys cutoff from the world in a geologically realistic way?
I am trying to create an absolutely isolated series of alpine mountain valleys in a fantasy world with forests home to tribes that cannot travel and have been cutoff from the world. My problem is that the most isolated valleys in Bhutan that I have found appear to be rocky. Alpine valleys require a river or stream to pass through them generally or be in rainfall range. Thus the gorge of those rivers or river valley will allow passage out. Most passes through Bhutan appear to follow gorges, rivers, or the lay of the land.
I am presently researching Tibet and Bhutan for inspiration yet not sure I quiet understand how to place this realistically in my world yet. Even Tibet was populated by humans and passable.
The idea I am coming upon is that a river and streams pass through successive alpine valleys forming small gorges between the valleys before going subterranean once again. Thus travel within this small 'land' of valleys is possible. The valley is blocked north by massive 7,000 to 20,0000ft mountains with a pass that is also impassable. The only high elevation pass south beyond the lower range of mountains is blocked by a colder global climate age thus cutting the valleys off from the world. The area is still biodiverse as it has not always been cutoff from the world.
My other option is that an earthquake creates a pass out of the valley but that would seem more supernatural and perhaps less geologically realistic.
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**As always, New Guinea to the Rescue!**
Turns out there are some isolated tribes on that island who have been isolated for a long, long time, 10-20 thousand years, in fact! Here's a reference: <http://www.sciencemag.org/news/2017/09/islanders-new-guinea-are-some-most-diverse-people-world-here-s-why> (Note the link between isolation and diversity; makes sense, right?)
**Update**: I'm emphasizing this genetic diversity point because the different highland types have been isolated from each other as well as the lowland guys on the same island, to hint that such a highland region could work out even if attached to a continent.
Their climate looks kind of like what you want, as the elevation mitigates the tropical nature of it. Check it out...
[](https://i.stack.imgur.com/L0GZS.jpg)
More details here: <https://en.wikipedia.org/wiki/New_Guinea_Highlands#Central_Range_sub-alpine_grasslands> but the money quote is:
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> Above 3,000 metres elevation, the high mountain forest yields to remote sub-alpine habitats including alpine meadows, conifer forest, tree-fern (Cyathea) grasslands, bogs, and shrubby heaths of Rhododendron, Vaccinium, Coprosma, Rapanea, and Saurauia all quite different from the tropical rain forest that covers most of New Guinea.
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> The alpine habitat above 4,000 metres consists of compact rosette and cushion herbs, such as Ranunculus, Potentilla, Gentiana, and Epilobium, grasses (Poa and Deschampsia), bryophytes, and lichens.[ 2 ]
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It even has the word "alpine" in it! ;D I can't promise you edelweiss, but work with me here.
Okay I know PNG is an island, but it's a *really big* island. Does that count?
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[Use a very large mesa](https://upload.wikimedia.org/wikipedia/commons/f/fd/Kukenan_Tepuy_at_Sunset.jpg) that has a concave profile, that is, the surrounding steep slopes are the highest points and the inside is like a bowl.
A mesa is usually made of sedimentary rocks, so it can have [Karst characteristics](https://en.wikipedia.org/wiki/Karst), that is large cave systems underneath as well as internal valleys that have been formed by water. This would mean that you could have valleys with rivers that get drained through impassable subterranean cave rivers that appear as waterfalls at the sides of the mesa.
Climate-wise check out [akaioi](https://worldbuilding.stackexchange.com/users/41922/akaioi) answer.
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**Put them on an island.**
Iceland is pretty isolated because it is in the middle of the North Atlantic.
[](https://i.stack.imgur.com/b6Bhm.jpg)
Iceland has the alpine terrain you are looking for.
[](https://i.stack.imgur.com/BTjy1.jpg)
<http://www.onegeology.org/extra/kids/earthprocesses/alpineglaciers.html>
[](https://i.stack.imgur.com/pM2q8.jpg)
<https://www.123rf.com/photo_33927927_warm-summer-days-in-iceland-green-meadows-and-streams-of-meltwater.html>
Could people on Iceland make boats and leave? Yes. It is a bit of a haul - 1200 km to Scotland. It is closer to Greenland. Here is what the east coast of Greenland looks like on Google maps.
[](https://i.stack.imgur.com/hb4Wb.jpg)
So: your people are on a remote island, with the closest mainland presenting only forbidding glaciers. Bonus for using alpine Iceland clone: Iceland has volcanoes and geysers! Nothing better for a cold winter than a natural hot tub.
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One more thing to keep your people on their island: **sea monsters galore**.
[](https://i.stack.imgur.com/6uSbK.jpg)
<https://upload.wikimedia.org/wikipedia/commons/e/ea/Carta_Marina.jpeg>
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Your people would have to have arrived at their location somehow.
Perhaps, in ages past, a pass existed which lead to or over the top of one of the mountains. Some intrepid explorers discovered a way into these isolated valleys, but returning was impossible or very difficult (I would say that they would have had to be able to leave in order to tell others about their wondrous find, and to bring them back).
Once the area became settled, a natural change of some sort blocked the already difficult passage, or perhaps the settlers wanted to isolate themselves from a tumultuous world and blocked the access themselves.
The river going subterranean is a good idea. If the descendants of the original settlers are unaware of the existence of life outside their valleys, they might consign the bodies of the dead, or those considered cursed to this path into the underworld.
Mountains are created when tectonic plates squish together and lift the land up. Mountains are also created due to volcanic activity. Either of these geologic events would work to isolate your society, or in combination.
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This planet is fictional, but I want it to be credible all the same. It is the same size and composition of Earth, orbiting a sun-like star. But that's where the similarities end.
The planet's orbit is far more elliptical, coming just into the 'too hot' section for a few days twice on its closest approach. With a 'spring time' like season between these two 'burns'. On the other side of its orbit, it is outside in the 'too cold' region for about short spell (I'd prefer no less than a month, but the math is more important than my preferences).
[](https://i.stack.imgur.com/iCBDk.jpg)
(above is a series of orbits. description is most similar to orbit D)
The question is then, within these constraints, how do I figure out how long each 'season' is? And would the planet's speed be constant throughout its journey around the sun?
EDIT:
The parent star is exactly like our sun. Same age, size, and composition. The planet I am talking about has the same composition as Earth, and the same atmosphere. as for the orbit. I figure that the star is in the centre of Focal Point 1. With the closest approach being 0.49 AU and the furthest distance being 3.2 AU (if wikipedia is correct about our sun's Circumstellar Habitable Zone being between 0.5 and 3 AU. If not, please tell me and I'll correct this.)
As for the planet, it has the same axial tilt as Earth, and the same wobble. Sorry if this is a bit boring to those that can do the actual math involved, but my focus is more on psychology, sociology, and biology. This is *slightly* above my paygrade.
As a bonus question. How long would the surface be uninhabitable during the two closest approaches? Are we talking just the period the planet is in the 'too hot zone'? I could imagine it would become unbearably hot well outside the 'too hot zone', making the dual summers too much for the populous to bear.
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Orbit "D" is physically impossible. You can't have the planet passing into the "too hot" zone twice in a single year. (Explanation as suggested in the comments: This is because the sun is always at one focus of the ellipse, and the two ends of an ellipse are the closest and farthest points from the focii. Ergo, when the planet passes the end of the ellipse near the sun, it must be closer than it is anywhere else, so you can't have two sections on either side passing through the "too hot zone", closer to the sun, with the end point farther away in the habitable zone.)
If it is really important to have *two* "burns" separated by a springtime in one direction and a long winter in the other, you'll need a more complicated system. Exactly what that would have to look like, I'm not sure. I can't think of any plausible arrangement of suns that would give that effect on a consistent basis, as opposed to say, once every century.
If you're OK with just one hot spike per year, the length of the year is easy to calculate. It's just $2\pi\sqrt{\frac{a^3}{GM}}$, where $a$ is the semimajor axis (the average of the closest and farthest distances of the planet from the star). Since the star is exactly the same as our sun, we can simplify this to get the length in terms of Earth years: $(\frac{r\_p+r\_a}{2})^\frac{3}{2}$, where $r\_p$ (for *perihelion*) is the smallest distance between the planet and sun, measured in AUs, and $r\_a$ (for *aphelion*) is the largest, also measured in AUs. For your stated values of 0.49 and 3.2 AUs, the year on this planet will be approximately 2.5 Earth years.
Figuring out just how long each season is, and how long the world would be uninhabitable, is significantly more complicated, because the planet's speed *is not* constant through the year. It moves much faster when it is closer to the sun, so the summer will be *much* shorter than the winter. Additionally, the hottest period will not be centered on the time of closest approach to the sun, nor will the coldest period be centered on the time of farthest distance, due to thermal inertia (the time it takes for the mass of the planet to warm up or cool down). Rather, the hottest part of the year will be shifted later than the closest approach to the sun.
If I were you, I'd avoid stating specific details of the orbit in any story using this world. Go ahead and figure out how long the year needs to be as a whole, and then just decide how long you need the "too hot" and "too cold" periods to be, and accept that there probably is a solution for $r\_p$ and $r\_a$ that will give you those values even if you don't know exactly what it is. And if there turns out not to be one, well, you've already established that this planet is only inhabited due to divine intervention anyway, so that's just one more thing that the gods have employed their powers to tweak, through solar shades or manipulating the planet's emissivity or whatever.
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<https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion>
You've made a number of errors in your set up.
Some are really surprising - such as your comment that the planet's axis[sic] can be pointing away from the star. (hint: two axes, if one points "away", the other will be pointing "towards").
Ellipse D doesn't appear (to me) to have the star at one focal point.
The Habitable Zone is determined by using a wide range of atmospheric pressures; using 0.5 & 3 AU for your two circles is really extreme. Earth wouldn't be habitable in either Venus' or Mars' orbits (0.7 & 1.5 AU), going to 3.2 AU is over-kill, imho.
As far as the computation of the length of the year and the seasons, the year is simple math, given the orbit.
The seasons are a lot more problematical. First, if Summer is fatal (for surface life) then wouldn't there be two "shoulder" seasons where it's just really really hot (but not fatal)? Similarly with a winter where (say) the atmosphere freezes out (or whatever). The number of seasons depends. Given the "thermal latency" that our oceans give our planet, I don't know if atmospheric freeze-out is credible for short periods (only months-long) of low insulation. I'd say that if I don't know then most people won't either (I am not claiming to be very knowledgeable in this, just significantly more than the "average" adult - but much less than those studying these issues as well as those arm-chair experts whose opinion you should also get.)
Anyway, given the interactions between the air and water and winds and surface, it is really difficult to predict what the seasons would look like even if we just moved Earth into Venus' or Mars' orbits (and didn't change spin or tilt). So, I say you're free to draw a smooth periodic function (see <https://en.wikipedia.org/wiki/Periodic_function>) of air temperature vs time. (by smooth I mean no "sharp" corners, everything happening over weeks or months).
A circle is an ellipse (with positions F1=F2). At the other extreme, consider a parabolic orbit. Toss a rock up and it is at its fastest leaving your hand slows to a (vertical) stop and plunges downwards (and in the absence of air resistance) with maximum speed at impact. This is similar to a highly elliptical orbit. The planet will be traveling its slowest as it passes through its apogee, and fastest as it passes thru its perigee.
I think you need to break down your question into a lot of smaller pieces. It is straight-foward math to determine what the length of a day is (which is most of what determines the seasons here) given the axial tilt of the planet and its spin. It seems to me, I recall that the difference between Summer and Winter due to the distance to the Sun is (estimated at) about 0.5°C, but don't hold me to that, please. I think what I would do is compute the days' lengths and apply them to the two limiting circles (inner and outer) to determine seasons (see diagram near wikipedia Ellipse Parametric\_representation). and then interpolate between them.
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Since I'm creating a "new world" for my story, I wanted to know if the following conditions would work for an Earth-like planet:
* Its moon (more or less same size as our moon) being much closer (but in a stable way).
* Higher tides than Earth.
* A twenty-six (26) hour day/night cycle (full rotation of the planet with respect to its Sun).
* A twenty (20) day lunar cycle.
I just want to know if all the conditions I mentioned above are realistic, and if they could lead to a planet that has complex life- just like Earth.
Thanks in advance!
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Yes that sounds reasonable. Your moon has to stay out of the Roche limit in order not to get ripped apart.
The Moon is ~ 400,000 km away, the Roche limit is only ~10,000km so you can move it closer. Having the moon closer to the planet will reduce the time it takes to orbit, the Moon orbits in 27 days, so 20 day orbital period sounds reasonable.
Slightly larger planet will give you 26 hour day/night cycle.
This sounds like very Earth like planet.
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All your settings are completely plausible.
I upvoted the @ventsyv answer; but I need to correct one thing: Planets can rotate at any speed; in any direction; thanks to collisions during their formation. It is not mass dependent. Asteroids can spin like tops!
See the [NASA Planetary Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/), or for a more detailed explanation, see this [more technical explanation.](http://cseligman.com/text/sky/rotationvsday.htm)
Venus, Uranus and Pluto all have opposite directions of rotation. Also look at the Length of Day in the NASA table; **correction** if anything bigger planets have *shorter* days. Earth is 24hrs, but Mars has a slightly longer day with **less** mass; in fact Mars is about 1/10th the mass of earth, yet rotates slightly faster.
Venus is lighter than Earth, it's day is 100x longer. Jupiter is the heaviest, with the shortest Day: 9.9 hours.
Day length can be anything you want it to be.
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If your planet and your moon have roughly the same masses as our Earth and Moon, respectively, then your moon cannot be "much closer" as you requested, if its orbital period must be 20 days, because the orbital period is not a free parameter. From [Kepler's third law](https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion#Third_law) (with some help from WolframAlpha) [you have](http://www.wolframalpha.com/input/?i=((20%20days)%C2%B2%20*%20G%20*%20(Earth%20mass%20%2B%20Moon%20mass)%20%2F%20(4%20pi%C2%B2))%5E(1%2F3)):
$$a = \sqrt[3]{{T² \times G(m\_1 + m\_2)} \over {4 \pi²}}$$
where
* $a$ = semimajor axis (maximum radius) of the moon's orbit
* $T$ = orbital period
* $G$ = gravitational constant
* $m\_1, m\_2$ = masses of planet and moon
If you plug in your numbers, that gives a semimajor axis of 312500 km.
If you want your moon to be closer and still revolve around the planet every 20 days, you need to lower the combined mass of the two bodies. The thing is, as you see, the orbital period is proportional to the cube root of the masses, so anything but a *large* decrease will make almost no difference. For example, if your planet had 50% of Earth's mass, the orbital radius of the moon would be 249030 km.
If you want to have a large moon close to a large planet, you *have* to have a fast moon. If you achieve *that*, more forceful tides will follow as a natural consequence. For example, with a period of 3.5 days your moon will be at about [a quarter of the Earth-Moon distance](http://www.wolframalpha.com/input/?i=((3.5%20days)%C2%B2%20*%20G%20*%20(Earth%20mass%20%2B%20Moon%20mass)%20%2F%20(4%20pi%C2%B2))%5E(1%2F3)) from the planet. That would mean *extremely* strong tides, though (check out [this answer](https://worldbuilding.stackexchange.com/questions/82719/tides-on-a-double-planet/82729#82729) for the calculations).
Your planet can rotate around its axis at pretty much any reasonable rate (26 hours is perfectly reasonable). The mass and distance of the moon are irrelevant in principle. Of course, a large moon on a close orbit will suffer a lot of [tidal acceleration](https://en.wikipedia.org/wiki/Tidal_acceleration) and as a result both the moon and the planet will tend to rotate more slowly and to get away from each other over geological timescales.
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One thing I feel needs pointing out, our Moon is already in an unstable Orbit (some time millions of years from now it's likely going to ~~impact~~ drift away from Earth), so how exactly did you stabilize the Lunar Orbit?
There's a few different options and I'm curious which you decide to use, the one that comes to my mind is to speed up it's rotation around the Planet, but when combined with the limit of the 27~28 Day Cycle into a 20 Day Cycle, I'm curious just how much closer you moved it if you did increase velocity.
Another facet I don't see covered is the Axis and Rotation, our Moon for example is on equal Axis with us and it's rotation keeps pace with us, this is known as Tidal Lock, one side always faces us and that side never changes unless something else comes along to alter that, does your Moon still have Tidal Lock?
If not that's going to affect Tidal Pull, which affects Weather, Ocean Activity (High/Low Tide, Hurricanes, etc.), Erosion Patterns and Erosion Speed, and also Earthquakes due to the shifting pull on the crusts (in your case, more everything due to increased Activity, it becomes a variable if not Tidal Locked, Constant if it is)
If the rotation is changed, you need to consider how it's changes are going to reflect on the Planet, if it's going with the spin, you have plenty of room to accelerate the Lunar Speeds, as the Planet will have very little Pull on the Moon, where if you are going opposite direction from Planetary Rotation, it's like running your hand across Sandpaper, it's going to grab a lot of velocity in very little time, not as much wiggle room, and generally destabilizes the orbit faster.
You're also going to need to factor in Mass, Gravity is directly proportional to Mass, if you have a huge chunk of Rock, and you move a smaller chunk of Rock next to it, those Rocks want to Smash together, but all the Gravity already affecting them (Earth) is disrupting the Pull between the two and drowning it out (making it heavy, this is how we Weigh it's Mass, which tells us it's gravitational pull), Bigger Earth, closer Moon, just bigger Rocks, it's up to you to decide their Mass though.
If your Earth is raining Diamonds, I'd give it about three years before it's raining a Moon, that 10km Radius in the Roche Limit is with 1.0 Gravity, which is Earth (our Baseline), more Mass, larger Radius, Jupiter for example, it actually does rain Diamonds on the Surface, the Surface it's self is likely smaller than our Moon though, combined with the fact that we've never measured the Surface Depth beneath that Cloud layer (not for a lack of trying), you can imagine the Roche Limit on it.
Also, the Magnetic Field is generated by our Planet's Core, one currently active theory is there's a gigantic electromagnetic Storm on the Core's surface because the Iron is under so much intense pressure that it's crystalized into Iron Crystals, which in turn gives off a piezo-electric Discharge (proportional to it's size), which reacts with the various Cosmic effects in our localized band of orbit (Cosmic Radiation and whatnot) to generate our Massive magnetic field which keeps us safe and allows Compasses to function.
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I understand that the wind is caused by a differential in atmospheric pressure, but say that a city built in an extremely flat landscape is constantly threatened/harassed by the wind and wind-related incidents.
What would the core of engineers come up with as a solution given a tech level of present-day to perhaps 25 years in the future?
Background: The city has poor soil structure (hence minimal terraforming) and the wind threatens their crop yields because of poor water retention in soil and root structures. Bedrock is fairly reachable and building materials are not scarce through trade.
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Windbreaks, and wind turbines.
Per the [US Department of Energy](https://energy.gov/energysaver/landscape-windbreaks-and-efficiency), a good windbreak can reduce windspeed for a distance of around 30 x the windbreak's height. A 30-metre high windbreak would be needed to protect 1 km of space. That's a decent height to build, but it's not impossible.
Construction methods will vary depending on conditions and available materials. It could be as simple as an earthen bank - you could make it even more efficient by digging soil from the field you want to protect, reducing its height, and using that to build your windbreak. If you're worried about erosion, flood waters, etc, you would build around a central core of steel pilings driven into the soil, surrounded with gravel and/or concrete, then pile the soil around that.
You would then line the windward side of your bank with wind turbines for power generation. Exactly how the turbines would affect the wind flow is not currently clear - it's an area of active research - but in 25 years, and with a lab as effective as this colony, we can be reasonably sure the engineeers would be able to place them efficiently.
And, nitpick - the engineers are a *corps*, not a core. It's pronounced the same, but has a very different meaning.
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The traditional solution is to use [rows or trees](https://en.wikipedia.org/wiki/Windbreak).
>
> A windbreak (shelterbelt) is a plantation usually made up of one or
> more rows of trees or shrubs planted in such a manner as to provide
> shelter from the wind and to protect soil from erosion. They are
> commonly planted in hedgerows around the edges of fields on farms. If
> designed properly, windbreaks around a home can reduce the cost of
> heating and cooling and save energy. Windbreaks are also planted to
> help keep snow from drifting onto roadways and even yards.[1](https://en.wikipedia.org/wiki/Windbreak) Other
> benefits include contributing to a microclimate around crops (with
> slightly less drying and chilling at night), providing habitat for
> wildlife, and, in some regions, providing wood if the trees are
> harvested.
>
>
>
The more of these rows you create on the windward side of the city, more energy you remove from the lowest level of the wind. This will decrease the wind in the city unless you build taller than the trees.
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This problem was earlyer faced in the dust bowl during the great depression in America. Look at dry land farming technics for some idea.
<https://en.wikipedia.org/wiki/Dryland_farming>
If trees cannot grow here you could use artificial wind breaks instead (walls). You could genetically engineer trees to be able to grow better at this location. Or you could build underground.
My favorite is gene edited trees. Once done you just plant the seeds about. There are however potential ramifications.
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On the Life Ball of my fantasy stories, a particular species of *delphinidae*- I call them black dolphins- have evolved and advanced at least as much as humans and other intelligent races.
A [prior question](https://worldbuilding.stackexchange.com/q/65201/10851) gives additional details about the black dolphins, but the answers and comments also exposed a gap in my development of them1-
civilized society leads to bureaucracy, and bureaucracy to so-called paper work. How does this sophisticated society store, retrieve, and disseminate information?
Here are a few examples of things that black dolphins *might* wish to record (items edited for brevity):
>
> * The following modification to the standard bubble-net strategy had proven highly effective in hunting anchovie bait-balls .....
> * Once upon a time in a sea far way, lived a very special porpoise ..... basket of goodies ..... porridge was just right ..... only through true love's first kiss ..... realized the evil lord *was* his father ..... and they lived happily ever after.
> * Sharks frequent the northeast corner of the reef during the third moon following the winter solstice. It is best to avoid this area at that time of year, or .....
> * The Grand High Council of the Yellow Reef Pod has decreed that no dolphin shall ..... violations shall be considered a Class 1 Misdemeanor, and subject to a penalty of .....
> * IT'S A BOY! That's right, Joanne in accounting has delivered a swift stream-lined son, 125cm and 18kg. Come meet the calf and celebrate with us. We will gather adjacent to the central fan coral at 1345 hours on Flukeday the 6th,
> for a special feast of mackerel and squid.
>
>
>
I can see two possibilities. First is a written language, the other is an extremely rich oral language relying heavily on very good- even eidetic- memory.
The last half-million to two-million years have given natural selection plenty of time for Real World(TM) *homo sapiens* to go from cave paintings and petroglyphs, to quipu and papyrus, to slate and chalk, to ink and paper, to digital media, to whatever lies beyond. The same amount of time can allow my black dolphins to adapt either the dexterity to write, or the memory to keep all stories and records without the need to write. Those dolphins that are best able to pass along knowledge will be the healthiest and most likely to survive to pass on their genes. Do those genes prefer the ability to hold a piece of coral and scratch marks on a rock2, or do they prefer the ability to perfectly recall and repeat a series of clicks, hums, and whistles?
I can see pros and cons both ways, thus my question boils down to - which scenario is more likely, and why?
---
1Despite the clear relationship, all questions and their answers should remain independent of each other.
2Optional Extra Credit: If you decide writing is more likely- is the writing utensil held in a fin or the snout? How does this impact other dolphin abilities?
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I would expect an oral history for 2 main reasons:
## 1. Lack of complex tool usage:
Humans and other apes developed fine motor manipulation ability (hands) to allow us to move around in trees, obtain food from complex sources (picking fruit, prying open a clam, manipulating a stick to catch termites, etc.), and throw things as a method of ranged attack. Writing or written language is so recent (a few thousand years) that it is unlikely to have had any individual evolutionary advantage or effect. Your dolphins lack this ability due to their evolutionary environment. This would make manipulating materials very difficult, especially when you try to come up with an enduring method of marking in their environment.
## 2. Short longevity of early symbols in an ocean environment:
Human writing likely started with splatters of mud and evolved to cave drawing images and later to more complex symbolic systems like writing. Your dolphin species as mentioned in the original question can make ephemeral artistic displays in sand or with moving rocks, so symbology may not be completely foreign. But for humanity piles of stones or pictures drawn in mud under the right conditions lasted a very long time, making them very useful not just artistic. While underwater, constantly moving tides and water currents would make lasting symbols, scratches on stone or shells or large rock formations resistant to water movement, more difficult to accomplish, especially given the dolphins lack of dexterity.
## Just because the record keeping is oral doesn't mean they wouldn't specialize or have a complex society:
Increased memory and recall may be a species wide trait, but everyone in society doesn't need to remember all these things themselves. Expect their society to make niches for record keepers for various kinds of information. Expect a storyteller, traveling bard, local clerk, bookkeeper, town crier, or other specialties for remembering and sharing specific types of information. Often some of these roles would likely have religious or other strong cultural support.
A side effect of this specialization in oral information transfer is the requirement for a long term education systems to pass on the large amount of information to following generations so you would likely have apprentices who would learn the tales and specialized information from the master serving as a backup and eventual replacement for society. Expect lifetime specialization with fixed societal roles.
This system would have definite limits, so information would only be kept as long as it was useful and would be unlikely to spread outside of it's immediate field of application. A priest or lawyer might apprentice for the position by memorizing the law or religious canon; the kelp farmers would have to remember planting techniques and seasonal timings; the squid hunters would remember hunting techniques and the squid migration roots; the storyteller would memorize the tales of history... etc.
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Let me try a written-language possibility. It's a long shot ...
Remember that dolphins have a "sonar" capability that basically detects sound that they emit being reflected on the surfaces in front of them. They can even send powerful sound bursts able to stun small preys.
By **arranging rocks** in the bottom of the ocean, in low-current areas, they construct their stories. **Their sonar is able to reconstruct a mental image** of these arrangements in order to read them, **even without light**.
To avoid currents and animals moving those rocks around, they could **fill the gaps with a layer of sand**. The sand does not block so much sound waves, so the sonar would still be efficient. Alternatively, they could find some sort of **cement** (some [occur naturally](http://edition.cnn.com/2016/06/02/europe/greece-underwater-lost-city/index.html) in microbe-rich environments) to make it more stable.
Such writings could take a lot of space (small rocks would be unstable), but make your ocean bigger :)
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I think that the dolphins could develop a written language, or perhaps I mean a physical one, although it would likely come quite late in their culture, after a long oral tradition.
So, the earliest attempt at markings would likely be made in soft sand, or perhaps even clay - maybe at first even accidental markings prompting a re-telling of the story until the mark is gone ("and he was so distracted he plowed right into the seafloor! you can still see the mark!"), and later evolving into something functionally like chalk and slate - or perhaps more like hand gestures - something that would be intended to be a temporary sketch for visualization purposes, to illustrate a story or diagram a concept. Perhaps a further exploration of this would be the use of stones for markers, making arrangements to symbolize some explanation, make a temporary map, or just for aesthetic purposes. This wouldn't directly lead to writing, as the water currents and sea tides would quickly alter any structures and so they would lack permanence, but it might be a starting point.
The next step, I think, might be souvenirs. They would need a strong oral history to get to this point, but it might be possible that as the number of stories keep growing, a story that is *great* or *memorable* may have the bards, history keepers or story-tellers (however the culture is spun out) tying the story to some concrete artifact - perhaps a tangible souvenir, perhaps a representative stand-in ("used *this* kind of shell to mark the location" or "and *broke* the stone! I actually have a piece here...). Possibly this might include landmarks of great tales, people might want to visit places where great things happened, and storytellers would want to learn the tale directly.
This would be an advantage to those story-tellers, those stories would be easier to remember and harder to overlook with a tangible reminder sitting right there, it might serve as a rough way for someone else to mark stories, to ask for them or mark their seriousness, and the stories would be more likely to be passed on successfully, in the end. This is still not writing or anything, but it seems a natural sort of progression for a culture to take. There might be sea-caves where such collections are kept, or eventually even walled off areas to keep the currents from dragging them away (though I expect stone and shell, which are somewhat more durable, might be preferred).
Then, perhaps, there might be a slow evolution of sculpture - great tales with no convenient souvenir or memorial piece (or when there were too many similar looking ones) might have storytellers out looking for really good symbolic ones, or eventually, having stones or shells be modified to make the connection to the story more explicit. Perhaps chipping or rubbing off edges against another rock, or biting for something like shell or bone (as a learning material, perhaps, I don't think it's that durable underwater), or dragging larger stones into mini-reproductions of landscapes or representations. I think that some great tales (or wanna-be great tales) would try for large sculptures as memorials - it would be much easier to see and work with gross changes rather than fine ones given the physiology.
So once there's a technology in place for sculpture, then I think writing is only a matter of time. As they accumulate more and more history, the density of information will be valued - the more information that can be fit in a smaller space, the better. Sculptures would eventually begin to acquire shorthand modifications, probably passed down from storyteller to apprentice, which can serve as more abstract symbols. And the symbols (eventually, eventually) could be pieced together to convey meaning without needing to be on a sculpture, or the sculpture will become more and more abstract as more information needs to be crammed onto the space, until it is an intricately decorated memory stone, not a mimetic sculpture or an intuitive souvenir.
I expect the final result would be something kind of like hieroglyphics, using symbolic stand-ins and metaphors and modifying them to communicate greater meaning, since the tie with sculpture would mean the markings and symbols would likely come from pictures... or the equivalent thereof, sonar-images, it's just the difference between image-first pictographs or logographs and sound-based syllabic and alphabetic symbols.
So, stepping back a little to see the whole picture - I expect your dolphin people would be starting with large, heavy markers (stones arranged in patterns and sunk partially into sand) and the rough shaping of preexisting structures, since these would be easier to see and to shape, and consequently they would only be made for very important things. Over time, the importance of adding more and more information would prioritize space, and the symbols would shrink and become more abstract, and could be afforded for more trivial things.
Physiologically, I think your dolphins would be gripping their tools in their snout, since modifying a fin would directly impact their speed and swimming ability. It might be possible, though, to modify some of the teeth near the back of the snout for gripping (the front teeth being needed for hunting with, looks like conical teeth to grab with). This would also have the effect of placing the tool being gripped close to the eye, the better to see what they're working on - dolphin eyes can move independently, and I'm not sure their vision overlaps as much as ours does to focus on details at the tip of the snout.
It is possible that in addition to back teeth specializing to gripping tools (perhaps coral bits or shell fragments, which can eventually be produced on demand), the side of the mouth or even the tongue might modify to give more dexterity and control for using tools with. I'm sort of picturing a multi-tentacled tongue for very fine dexterity, but it doesn't *have* to go that way... it just might, once dexterity becomes useful and fine control is translatable to a survival trait.
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I'm making five habitable planets the size of earth as moons for a gas giant the size of Jupiter.
Then I want to add many more smaller moons, Our Jupiter has 67 moons, I want as many small moons possible and 5 earth-sized moons for mine.
What conditions of this planetary system would threaten habitability on the five earths?
How many moons can there be and still have a 100% perfect stable system?
How many moons would be visible from each of the earth sized planets?
What is the safest distance from a earth like moon to a small moon to make it possible for plankton/aero-plankton ''traveling'' from a moon to another.
Oh almost forgot, at least 60% of the small moons have to be good potential colonies for the humans and aliens that live in those 5 earth like planets.
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I'm going to assume that the planet may be both Jupiter-like, and Saturn-like to give us more real world examples to work with. I'm also going to assume that said gas giant is at 1 AU from the sun so there is sufficient heat for Earth-like life. Imagining life in a cold Europan ocean is too broad for this topic. As for gas giant formation that close to the sun, there is ample evidence for that in exoplants. I don't think that we understand solar system evolution well enough to say that Jupiter in Earth's orbit is unrealistic.
## Possibility of formation
Jupiter's moons are assumed to be the four left of a larger set of moons. As Jupiter's ancient moons formed, the proto-planetary disk around the sun was still relatively dense. This cause the moons to lose velocity and spiral into Jupiter. The four remaining were far enough away that they maintained orbit until the sun sucked up or drove off most of the free dust. So if (big if) your Earth-sized moons developed far enough off, then they could have formed. I suspect a larger planet than Jupiter would be needed to form moons of that size though...I don't know.
Saturn's inner moons apparently underwent a cataclysmic collision around the time of the dinosaurs that destroyed them. The debris then reformed into Saturns larger inner moons (basically all of them except Titan and Iapetus). You don't want that to be happening on your moons...unless you want four to destroy and reform while life is evolving on the outermost moon...the denizens of which could colonize the inner moons. There is no explanation as to why these inner moons collided...so there's that.
So the answer to, "could these moons form" is...maybe? Lots of mystery here. But the larger the gas giant the more likely it is to happen, in my opinion.
## Hill Spheres and Moon's Moons
The Hill sphere is the region of space where a planet or moon can keep a satellite. Earth's is 1.5 million km, while the moon is 384,000 km away. So close the Jupiter, the hill sphere is smaller. An Earth-like planet in orbit of Jupiter at the orbital distance and eccentricity of the four large moons (Io, Europa, Ganymede, Callisto) would have a Hill sphere of 42, 36, 87, and 152 ,000 km. This is significantly smaller than the distance to our own moon. However it is larger than the distance to Deimos (23,000 km) the farther of Mars' two moons. So you could have Moon's moons, but they'd be smaller than our moon, and closer in too.
The farthest out large moon of Jupiter or Saturn is Iapetus, at 3.6 million km. If Earth was at this distance from Jupiter, its Hill radius would be 352,000 km. If it were circling Saturn (a smaller gas giant), it would be 526,000 km. This is the only configuration that could conceivably support a moon at Earth distance.
This just covers Hill spheres, there are plenty of other orbital dynamics that could disturb secondary moons forming around primary moons. In general, let me express my doubt that any of the moons could have their own moon, and let me be especially doubtful that any of those moons could be larger than a tiny moonlet.
The co-orbital moon idea is also interesting. Tethys and Dione (two moons of Saturn) have 'Trojan' moons in leading and trailing orbits. These moonlets are from 2–35 km in size.
## Radiation
Jupiter's satellites get...a lot. Io gets 3600 rem/day, Europa 500 rem/day, Ganymede 8 rem/day, Callisto 0.01 rem/day. 1000 rem is deadly, 100 rem will give you radiation sickness, 0.1 rem is on the order of a normal dose on Earth over a YEAR. So on Callisto you'd be fine, on Ganymede you'd die in a month, Europa a couple of days, and Io immediately.
Saturn's satellites on the other hand don't get very much. Jupiter has a powerful magnetic field, but that causes the radiation. Your gas giant will need a weak field like Saturn. On the other hand, the planets' inhabitants need to be defended from cosmic radiation sources, so each planet will need its own magnetic field. Alternatively, one the planets of which life developed could have magnetic fields, while the rest are colonized and have structures built underground to protect them from cosmic radiation.
## Looking at moons from other moons
I calculated all these myself with a spreadsheet and trigonometry, so there may be some errors. Here are some reference numbers: The full moon from Earth is 31 arcmin, which is just over half a degree in the sky. The sun is about the same, although it is obviously much brighter. For the large satellites of Jupiter and Saturn, the largest a planet appears is Jupiter from Io at 549 arcmin or almost 9 degrees of the night sky. Another way to put this is 1/20th of the way from horizon to horizon or 18 times the size of the moon. Thats almost too big to comprehend. The smallest a planet appears is Saturn from Iapetus, at 56 arcmin, or still twice the size of the moon. All your moons will have significant light from the gas giant.
If Earth-sized planets were in the orbit of Io and Europa, at closest approach they would appear to be 175 arcmin from each other, or 3 degrees, or 6 times the size of the moon. If Earth sized planets had an average orbit around where Iapetus is, they would appear to be 6 arcmin from each other, 1/5 the size of the moon.
## Colonies on small moons
One word: don't. Humans live at 1 g of gravity. Gas giants don't have surfaces, Venus has .9 g at the surface, Mars and Mercury have 0.38g. Our anatomy and physiology is designed for 1 g, it helps our bones calcify properly, helps our blood circulate, and does countless other things we may not even have discovered yet. Humans maybe could live a lifetime on Mars and Mercury. It is very unlikely they could live a lifetime at an even lower gravity. Luna, Titan, and the 4 Jovian moons have gravity of 0.12–0.18 g. Pluto, Triton, and various Kuiper belt objects are below 0.10.
A medium sized moon (like Rhea of Saturn, say) might have 0.027 g. This is way not enough for a human to live, but annoyingly much if you want to, say, launch things into space. Humans are better off living in space colonies that generate artificial gravity by rotating. If you want to exploit a moon, you are much better off with one that has a much lower surface gravity. Phobos, for example, has a radius of about 11 km, and a surface gravity of .0006 g, but still has $10^{16}$ kg of usable materials to mine.
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Umn, I'm gonna assume that you are gonna ignore the fact that not much( at least to our knowledge can live at that kind of distance from the sun).
First thing first,
**Whizzing meteors and comets**
If your inhabitants haven't died of freezing and frostbite and starvation. Then they will have plenty of extra-terrestrial debris that can wipe out earth to worry about. [Which can be seen from here](http://www.space.com/32420-jupiter-asteroid-impact-rate.html) that Jupiter gets hit by **extinction-causing debris** more often than not. This means that in all likelihood, your moons are living in a very dangerous neighborhood. With the asteroid belt towards the sun and the Oort Cloud to your back, I would not want to live near a planet that actually attracts them.
**Jupiters 67 moons**
This is a superficial fear but I'm gonna say that there's that likelihood that a fellow moon can and could wreck your nice planet moons. So you better place them well.
**Jupiters gravity**
According to this [article](http://www.universetoday.com/15110/gravity-of-jupiter/), Jupiter's gravity affects the entire solar system. As I'm no physicists nor astronomer, this is just a theory but I have a feeling that your moons might be a time bomb. I have no idea when Jupiter gravity could tear them apart and you better be careful.
**Now for the topic of moons for your earth moons**
**[Co-orbital moons](https://en.wikipedia.org/wiki/Co-orbital_configuration#Co-orbital_moons)**
Your best bet, considering you can fit more than a **thousand earths** in Jupiter. The chances of your earth moons meeting other moons on a daily occurrence is small as A: we have no idea how fast their orbits and B: the orbit would take forever. Meeting other moons would be something of a miracle. So therefore having moons that orbit your earth moon and vice versa would be a better bet.
**Instead of many small moons**
Did you know? Jupiter has a **ring**, a ring of dust and rocks. the only problem is that it's not as visible as saturns ring. Now all you need to do is make this ring more visible instead of having a billion little rocks that are all the more likely to murder your earth moons.
**Bonus**
You know how I said that Jupiter can fit a **thousand earths**? Your gonna need a really really fast orbit to reproduce earths 24 H day and night,**this is because your earth moons need to get around Jupiter to get any form of light at all**. The number of days it would take to orbit around the sun[one year] would be the same as Jupiter which is **12 years**, which means that your have 12 years worth of summer, spring, winter and autumn[**Provided you have them**].
**More extra**
I really hope you have thought through how your inhabitants will survive the with the measly sunlight and **[warm](http://www.space.com/15498-europa-sdcmp.html)** \* **cough** \* temperatures.
**space plankton??**
Not possible. No. Just 99.9% impossible . How are plankton going to travel across your earth moons anyway if we took 3 days to get to the moon safely. They will need cold immunity, immortality and be **very very patient** to wait for that **0.00000000000000000001x10^-9999999999999** chance to actually get there. Unless **your plankton can build spaceships**
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After watching the newest [League of Legends Cinematic Trailer](https://youtu.be/tEnsqpThaFg?t=40) I became obsessed with the concept of shooting crows at a person, sending them flying, or even better shooting them at the ground in order to fly!
But, of course, this cannot be possible, right? Assuming that I am somehow able to create and shoot these crows: **How fast would I have to shoot how many of them in order to send someone flying? What about to send me flying?**
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Here is the estimation, There are lots sub-species of crow, ranging from 0.68 kg to 4.4 kg per bird depending on the species, at maximum speed they fly about 35 to 56 km/hr. By shooting them at the ground in order to fly I think you mean something like a rocket, right?
Average momentum of each crow would be approx (115.5/60) 1.925 N. Assuming crows are generated magically (not worrying about carrying them with you) and flying at max speed, they can propel your average person of 80 kg.
You would need 784 N to stay flying. Roughly 407 crows per second. More if you want to fly upwards.
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[Question]
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In this scenario, an underwater city is a collection of domes interconnected by tunnels 17 feet wide and 17 tall. The largest of the city's domes is 71,000 square feet in area and 137 feet tall. The city is situated 500 feet beneath the surface.
When you descend deeper into water, it becomes imperative that you shrink the size of the glass windows to make sure that they don't crack under pressure.
In a dome of that size at 500 feet below sea level, how big and how thick must each window be?
[Answer]
The main issue here is the geometry of your windows; while 500' below the surface isn't *that far,* it's still a considerable amount of force over a large area. Your city, from a quick-and-dirty engineering standpoint, is just a series of pressure vessels.
So let's say you want a comfortable 1 atm of pressure inside the city. In reality, you'd want a higher pressure inside, to help counter-act the pressure on the outside. According to various groups, it looks like divers (breathing air) [should only go down to 50-60 m (~164'-196')](https://en.wikipedia.org/wiki/Deep_diving#Depth_ranges_in_underwater_diving), somewhere around 1/3 the depth of your city.
Engineering toolbox has a nifty [thick-walled pressure vessel stress calculator](http://www.engineeringtoolbox.com/stress-thick-walled-tube-d_949.html). If *any* of these stresses exceed the stresses of your "glass," your connecting tubes will break! Oh, we should also mention that there are different types of glass: borosilicate glass ([pyrex](http://www.matweb.com/search/DataSheet.aspx?MatGUID=5bb651ca58524e79a503011b2cd8083d)), common fiberglass ([E-Glass](http://www.azom.com/properties.aspx?ArticleID=764)), [S-glass](http://www.matweb.com/search/DataSheet.aspx?MatGUID=ccd3fcc24efb46a88a091f560487cee5), [soda-lime](http://www.matweb.com/search/datasheet.aspx?matguid=4bcaebf032014605885a9bb64010664a&ckck=1), even Star-Trek inspired [magnesium aluminate](http://www.trans-techinc.com/documents/magnesium-aluminate.pdf), and *many* others! Each of these have their benefits and weaknesses. Let's assume you're using a '[safety glass](https://en.wikipedia.org/wiki/Toughened_glass#Properties)', which is supposed to withstand 15000 psi of pressure. Using the tool from engineering toolbox, the minimum thickness allowed is: **4 inches** (otherwise the hoop stress is too much). This has no safety factors involved, so you likely want this thickness to be much higher, *at least 8 inches*.
You can perform a similar calculation for your domes.
[Answer]
For every 33 feet deeper in the water, the pressure increases by about 14.5 psi [[reference]](http://oceanservice.noaa.gov/facts/pressure.html). Also, the atmospheric pressure at sea level is about 14.7 psi [[reference].](http://www.britannica.com/science/atmospheric-pressure)
At 500 feet below sea level, the pressure would be
$$ \left(\frac{500}{33} \times 14.5\right) + 14.7 = 234.39~\text{psi}$$
Fully tempered glass in the US is generally rated above 65 megapascals (9,400 psi) in pressure-resistance, while heat-strengthened glass is between 40 and 55 megapascals (5,800 and 8,000 psi) - [Reference](https://en.wikipedia.org/wiki/Toughened_glass#Advantages)
As incredible as it seems, apparently, just a couple of inches should be easily strong enough.
[Answer]
The simpler solution would be to not keep the pressure in your city the same as the surface pressure, that way the difference between the water pressure and the air pressure would be minimal. The pressure difference between the upper areas (+137ft) and lower areas will be more pronounced than at the surface, but should be fine.
You cannot breathe a regular air mixture either, 500' is past the point of oxygen being toxic, and nitrogen will be causing problems too. There are a number of mixtures with helium that would likely be recommended.
The main reason you don't want to keep surface pressure is that any leak is going to cause a big problem FAST.
Granted, people coming and going will need to deal with decompression etc.
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There's a [classic story](http://www.gutenberg.org/files/19445/19445-h/19445-h.htm) that uses a chemestry text as a Rosetta Stone to get a toehold on an exo-archeological expedition, because the properties of the elements prove to be something known to be in common with the aliens.
The elements are the same. But how might aliens *organize* and *represent* them?
Different (perhaps better) ways of laying out the table are already well documented.
But this XKCD cartoon [(link for explain xkcd commentary)](https://explainxkcd.com/wiki/index.php/1442) got me thinking...
[](https://i.stack.imgur.com/K4jD7.png)
Meanwhile, I have thought about alien alphabets and digits in the past. Considering a simple letterform (as opposed to a complex ideograph) it's actually very hard to invent something that's not already in Unicode for *some* writing system, as there are only so many ways to combine a small number of elementary strokes.
**So, my question is:** how might an alien race depict the compact symbols for elements that are somehow evocative of their nature? Suppose that the elegant symbols are applied to the lightest elements (and those known/important in antiquity) and the full table can be formed by adding modifications to the basic symbol to move to heavier rows.
The element's *nature* would be the bonding structure (count or shape), but I didn't want to limit it to that in case someone has other inspiration; the fact that carbon has so many hybrid bond types might be more important than any specific bond represented.
They could be like our symbols for astrology objects, used only for those things and not related to general writing. But it would be coolest if they *were* normal characters, exploiting the geometric nature of their (alphabetic or syllabic) writing system. (An ideographic writing system using pictograms of the Lewis bonding structure is just too lame. So emphasis on relatively *simple* character shapes: think ☿ not 辰星.)
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**Reopen:** Jim2B says he has an *objective* answer; see his comments. So, it doesn't have to be "opinion based". Give it a try; you can always close it again if it's no good, but he's a high-ranked poster and I expect something good and interesting.
[Answer]
There's different ways that you can organize the elements, as you said:
* Ascending or descending proton count.
* Electron orbital filling.
* Unique spectroscopy signature.
* Ionization potential.
* ...
I feel strongly that these options for an alien would differ based on culture and level of technology.
Don't forget the possibility that an established periodic table can *change* if it conveys additional information that would be useful as a sort of casual reference for the new technological advancements that a species reaches.
For example, each element has a unique spectroscopy signature, and this is vital to understanding what elements are significant and present in distant celestial bodies.
**This is important if you're a space farer.** So you could find that the following table could be encoded in various ways, and the elements that support life or are vital to their technology or existence would be up in the front with their better symbols.
[](https://i.stack.imgur.com/RD5ZZl.png)
So onto the symbol aspect, what we're looking for is a simplification and *compression of information* that would encode a higher level classification. Schwern already talked about how that would be easy for a proton/neutron count.
But this becomes more difficult with additional pieces of information. How do you take an entire spectroscopy signature and compress it?
You have a few choices:
* The layout itself is sufficient.
* The layout itself is sufficient paired with whatever information they want, combined with their native names for elements or simpler data.
* Encode the complex information with a symbol: A pictogram would suffice.
* Encode the complex information as a number. Perhaps using prime number factors.
* Employ the use of a legend.
This being said, don't forget that an advanced space faring species might be invested in symbols that are universal. This is what we took into consideration when depicting the hydrogen atom on the [Voyager Golden Record](https://i.stack.imgur.com/3Zir3l.jpg)/[Pioneer Plaque](http://www.nasa.gov/centers/ames/images/content/72418main_plaque.jpg), which is a hyperfine transition of hydrogen.
Basically, it's possible that the information encoded in literal universal symbols (circles, wavelengths, etc) is sufficient and would take precedence over an arbitrary and cultural alphabet or pictogram, which only they would understand.
[Answer]
Knowing nothing about these aliens, let's just look at more meaningful ways to describe the elements if we remove the historical and cultural naming conventions. There's no reason aliens would have this very human obsession with giving things names associated with mythology or who discovered it or where it was discovered or what property happened to be important when it was discovered... *anything* but its fundamental properties.
For example, "hydrogen" is from the Greek ὑδρο- "hydro" meaning "water" and -γενής "genes" meaning "creator". It's named that because when you burn it, combining it with the then unknown oxygen in the air, you get water. "Carbon" comes from the Greek verb "γράφειν" which means "to write": you write with graphite (ie. a pencil). Not very descriptive, in the long run, of two of the most important elements for life.
Simplest thing to do is to name them by their most defining characteristic, their proton count: "Element 1", "Element 2", "Element 3", and so on. Perhaps this would be written in shorthand as E2 for Element 2 (helium).
Isotopes are variations in the neutron count. [Deuterium](https://en.wikipedia.org/wiki/Deuterium) would be "Element 1 with 1 neutron". If the neutron count is omitted then convention would choose whether it means to use the usual mix found in nature (as we do), or to assume the proton and neutron counts are the same making "Element 1" and "Element 1 with 1 neutron" both deuterium. Hydrogen, with no neutrons, would be "Element 1 with 0 neutrons".
The neutron count would go where the confusing and historical [atomic weight](https://en.wikipedia.org/wiki/Relative_atomic_mass) now goes. 0E1 would be hydrogen with one proton and no neutrons. 8E6 would be Carbon 14 (6 protons, 8 neutrons = atomic weight 14).
And that's the two most important things you need to differentiate the elements and their isotopes: their proton and neutron counts. Everything else is a property of that isotope.
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You can flip this on its head and do *exactly* what humans did, but with alternative means of discovery and properties they found significant.
Maybe the alien who discovered carbon was impressed with diamonds, so its name means "shiny thing which cannot be damaged". Maybe mercury, instead of lauding its speed (ie. quicksilver) and associating it with the Roman god of speed, associated it with insanity and named it after something symbolic of insanity.
You'll have to fill in the blanks, they're your aliens.
[Answer]
You could go with a binary of sorts... consider the use of Math in Contact and how the researchers determined that the signal was intelligently created in origin. In this story, the signal pulsed in incremental prime numbers (Whole Numbers that are only divisible by 1 and themselves 1, 2, 3, 5, 7, 11... ect). These numbers are too random to be produced in nature, but so basic it can be understood under any counting system (if you use base 7, then 11 is still 4/2 and 10/2 is still not a whole number).
Elements are ordered by the number of protons in their nucleus and the number of electrons in their orbital cloud... All non-metal elements have between 1-8 electrons in their outermost cloud. The ones on the far right of the periodic table have 8 (the noble gasses, with the exception of Helium, which has 2) and the far left have 1. The place on the rows descends as the number of inner electron shells increases. Thus, you could easily establish a pattern of two numbers (P,E) which will denote the behavior of most of the important to life elements up to the 18th (Agrgon). P would be the total number of protons, where as E would be 1-8 for the last shell of electrons. Thus (8, 6) will be oxygen. (16, 6) would be sulfur. Pattern recognition and basic high school chemistry can carry your language this far. Beyond Argon, you'll need a better chemist than me, because I don't understand the metal groupings (groups 3-12) and the heavier elements between row 3 and 4 on columns 5 and 6.
Converting this to a binary will be another layer of help as any math will need to show a one or a zero representation. The fact that Binary tends to be a grouping of eight ones and zeroes might also help since the most electrons in a single shell is eight, though I don't know how to group that.
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This question springs off [this one](https://worldbuilding.stackexchange.com/questions/37510/how-to-render-much-of-a-worlds-metal-unusable).
I am building a science-fantasy world, because I like the idea of civilizations without metal I decided to incorporate it. However rather than make metal scarce I chose to render it usable to the people that live in the world. I did this by creating a life form inspired by [metal/synthetic material eating bacteria.](https://en.wikipedia.org/wiki/Microbial_corrosion) The Metal-Phages eat and nest in metal but also lethally contaminate it.
Thanks to the creative and knowledgeable people here and elsewhere, I was able to refine my ideas. That lead me to the realization that I don't need to block access to all metals just the types that can be worked into tools or alloyed together to achieve the same.
So I ask what Minerals, with an emphasis on metals and their alloys, were vital to the development of early human civilization?
[Answer]
## 1. Copper
The metal form of copper can be found in certain mineral veins. [Finding a copper vein and playing with the "shiny pretty metal" was probably humanity's introduction to working with metals.](https://en.wikipedia.org/wiki/Metallurgy_during_the_Copper_Age_in_Europe)
From this early introduction metal tool making was discovered.
## 2. Bronze
After discovering copper, [metal smiths discovered that if you alloyed copper with another recently discovered metal, tin, you got a much tougher, durable, and hard metal called bronze.](https://en.wikipedia.org/wiki/Bronze_Age)
This was both the introduction of the Bronze Age, but also the discovery that we could change a material's property by changing its composition.
## 3. Iron
[Iron can (rarely) be found in its pure or alloyed metallic state](https://en.wikipedia.org/wiki/Ferrous_metallurgy). Iron as an ore is **far** more abundant than copper or tin. Discovering that if you heated certain rocks in combination with other rocks, you could get a new metal was a huge discover!
Early iron was very soft (for pure alloys) or very brittle (which is what they got most of the time). In fact as a working metal, early irons were inferior to the bronze alloys of the era. However, iron was much more abundant.
## 4. Steel
[Steels came into being when certain smiths discovered that when you heated your iron with certain other rocks (limestone & coal) in certain proportions you got a much superior metal.](https://en.wikipedia.org/wiki/Crucible_steel)
Early steels were both harder and tougher than iron and bronze. It was probably these early steels that lead to the belief in magic swords. For example, [high quality steel sword could literally destroy iron or bronze weapons.](https://en.wikipedia.org/wiki/Ulfberht_swords)
[Answer]
Ever hear of the Bronze age? Copper, tin, lead, (brass and bronze). Copper and tin are the more important ones, lead was a softer material making the other two easier to work with. Later on Iron became very important, but we started with metals with lower melting points.
Gold is nice and 'easy' to work with too, but it is mostly useless for tools, Jewelry and money is it's primary function for non-technological folk.
[Answer]
This answer is based on [History Of Metallurgy (historyworld.net)](http://www.historyworld.net/wrldhis/PlainTextHistories.asp?ParagraphID=bba) and [Wikipedia page on metallurgy history](https://en.wikipedia.org/wiki/Metallurgy#History).
The first metals man was able to work with, were probably gold and silver due to their very low reactivity rates and high chances to find a pure gold or silver block. However, while these metals were aesthetic for the ancient peoples, they were too malleable to be put to use in objects where brittleness was required. You could easily make a usable drinking glass with gold or silver, but a pure gold knife would be useful only for cutting soft fruits.
The next metal people came across was copper. The metallic age began with rising use of copper by circa 7000 BC. Copper is less reactive than iron and melts at lesser temperature. This means that if/when the ancient peoples accidentally placed a mineral stone rich in copper in their camp fire, they ended up with pure copper lump in the morning. Heating and molding gold had already taught them how to melt these strange minerals and once they found copper tipped weapons useful in combat/hunting, copper age was on the way.
Another form of getting metallic objects was scavenging for meteorites after a shooting star crashed down in the vicinity. Meteorites are known to contain a high content of metal (specially iron) and relatively low on rock (silica). The people incorporating such pieces of meteorites would have found them to be extremely useful when used for cutting or stabbing.
Serbs were already smelting (heating ores in fire to melt the metal and obtain it in pure form) ores by 6000 BC. There are signs of copper smelting in southeastern Europe by 5500 BC. By 3500 BC, smelting was common around most parts of Europe.
The idea of alloys was in swing by 3000 BC. The first alloy to be prepared was bronze (copper and tin). Alloying technique originated in prehistoric Iraq and gradually spread to south Asia before becoming widespread and reaching Europe by 2000 BC.
The next and by far the most important metal was iron. Iron ore is harder to purify than copper or tin and requires complex processing. This is why iron mining and purification signs are found no sooner than 1300 years BC.
# Conclusion
People were introduced to metal through pure lumps of gold and silver.
Copper, tin and lead containing stones were found to be refined easily by simply putting them in fire.
Iron containing meteorites were highly prized for their brittleness and strength.
Copper age began around 7000 BC. Alloying became a norm in around 3000 BC and iron mining was in place by 1200 BC.
So then, if you ask what metal people discovered before others, it would be gold. If the question is, which metal started the metal ages, it was copper, followed by tin, lead and finally iron.
[Answer]
If your question is ([to continue from Youstay Igo](https://worldbuilding.stackexchange.com/a/37652/3434)) what metal to make inaccessible to prevent the large scale adoption of metals, the answer is **copper**.
Copper and iron were only metals with alloys really usable for tools (and hence technological innovation) and iron metallurgy evolved from techniques developed for copper. People would still use iron but the volumes available would be too small to be relevant. Besides iron is kind of consumable, so you could rely on the people themselves to remove all easily accessible iron over time.
Gold, silver, lead, tin, and zinc are also important and accessible early but without copper or iron they probably would not lead to anything undesirable. I mean, you could use silver or gold alloys with zinc, tin, and arsenic to do all kinds of things, but they are naturally rare enough for that to not really matter.
Compounds of mentioned metals were used in glass making for controlling color and glass making might allow developing technology for working at temperatures high enough for accidentally inventing alternate uses for those metals. So you might want to deal with iron as well just in case.
[Answer]
Not directly an answer, but examples for you:
That Share of Glory is based on a society that uses ceramics instead of metal. As a result they have no understanding of electricity and magnetism outside of some Ben Franklin type experiments with lightning.
<http://www.gutenberg.ca/ebooks/kornbluthcm-thatshareofglory/kornbluthcm-thatshareofglory-00-h.html>
A second story, that I can't find now, but that was published in Analog back when it was still Astounding -- late 50's early 60's -- was a post nuclear war world trying to rebuild. All the easy ore was gone. The result was a tempering process for glass
There have been several stories -- one by Hal Clement, one by Charles Sheffield that have been on cold enough worlds that ice was used as a structural material.
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[Question]
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In the setting I'm constructing, humans migrated in a single major wave to a pair of large continents within the last thousand years or so (the exact value is partly dependent on the answer to this question). While they initially settled in the coastal regions (as one might expect), over time, the descendants of that original culture have claimed, and sometimes conquered, lands spanning an area roughly equivalent to Europe in size. In the current iteration, cities and nations developed and crumbled and grew again in that time, ultimately resulting in the current, pre-industrial state of the region.
So, the question I've hopefully led up to is this: Supposing that all initial immigrants to this "New World" spoke the same language and shared a largely-similar culture, how long would it take for various subgroups to develop mutually unintelligible languages?
Additional details:
* The region of heaviest colonization and city development is
comparable to the Mediterranean in size and shape, so relatively
constant sea-based trade and immigration is possible among the major
city-states and nations.
* Assume a starting population of approximately 150-200 thousand
migrants, with no further migration from the "Old World" (at least
nothing appreciable).
* At the onset, the culture has a largely-shared religion, one which
has had many aspects more-or-less proven empirically.
* Technology level begins in an approximate Age of Sail, though, the process
of this migration is precipitated by a major calamity, so quite a bit
of knowledge is lost in transition.
* Magic is not well-suited for long-distance communication of any sort.
* Natives are something of a tricky matter, as there are a couple of
categories. Where humans are concerned, the northern continent
has a number of tribes (mostly hunter-gatherer, with a handful of
legitimate settlements), most of which are north of a number of
geographic boundaries that would prove difficult for early
exploration. The most accessible regions of the southern continent
have a culture of nomads who are relatively cohesive. In both cases, though, all humans are outnumbered
significantly by another species/race who only tangentially interact with the
other natives, but are capable of verbal communication. At most, there are only a few groups who could be
perceived as having anything beyond bronze age technology.
This is my first question here, so please let me know if I need to format this differently, or need to add any further information. Thank y'all!
[Answer]
The answer, strangely enough, is as fast as they want it to. People use language to communicate but also to differentiate. If a group of folks wants to set themselves apart from another group one way to do that is change how they speak. This applies to high-status usages like RP as well as black American English its identical twin Southern American English as well as Cockney, Geordie, or whatever the hell it is they speak in Baltimore. Regional usage becomes a badge of belonging. This even happens in subcultures; Thieves cants, Polari, Hip-Hop lingo, Gobbledygook etc. If you have people who want to set themselves apart from the whole they will play up differences in speech.
Alternately creoles and pidgin these happen very fast a pidgin is what you speak when you date a girl from Guadalajara who thought is was a good idea to learn german and french rather than English. It is a rough and ready mix of whatever works. Grammar from one language a vocabulary based on cognates or strange constructions. "Kerosene-lamp-belong Jesus gone-bugga-up" means "there was a solar eclipse". Creoles are what would have happened if our children would have spoken if it would have worked out between me and Lupe. Creoles are pidgins when they are spoken as native languages they have complete grammars and rules.
If there are native lingos on your world and a chance for creolization combined with nationalism on the part of your subcultures you can really decide on any time scale the story requires. greater than one generation.
now if I can only figure out what "Lo siento, pero usted es demasiado guapo para mí." means.
[Answer]
It really depends quite a lot on the particular environment. The more division the environment provides between people with a dialect, the faster they diverge. This is true for all linguistic studies.
As a real life data point, [Kriol](https://en.wikipedia.org/wiki/Belizean_Creole) from Belize diverged from English in less than 200 years. From the Wikipedia article:
>
> Decker (2005:3)[5] proposes that the creole spoken in Belize previous to 1786 was probably more like Jamaican than the Belize Kriol of today.
>
>
>
This suggests that in 1786, the creole spoken was intelligible by other speakers -- a dialect
>
> A 1987 travel guide in the Chicago Tribune newspaper reported that Belize Kriol is “a language that teases but just escapes the comprehension of a native speaker of English.”
>
>
>
Having been there, I can attest that two native Kriol speakers talking between each other was truly unintelligible to myself.
[Answer]
Here on Earth, Greek is still recognisably the same language as that used by Homer. In contrast English has come into existence in under a thousand years and yet it is far from the newest language on the planet. Why?
A new language, as opposed to a dialect, is most commonly born of the mixing of two peoples with incompatible languages. Incompatible specifically means *not* dialects of each other. For English its genesis was a mixing of Norman French speaking rulers and Anglo-Saxon languages spoken by the conquered. The pattern is that one generation starts to use a pidgin language to aid communication. The original languages persist in everyday use within linguistically and socially separate communities. The next generation develop the pidgin language into a creole. This evolves rapidly. Words gain new meanings. Clashing grammatical rules get ironed out. As the creole gains expressive power and because everyone is speaking it, the original languages fade away. In subsequent generations the creole evolves very rapidly in its early days. English is still a fast-changing language centuries after Shakespeare, but it is changing nothing like as fast as it did from Chaucer to Shakespeare.
So in your scenario it depends on history. Two isolated groups who started with a common language may drift apart phonetically onto dialects but it will take millennia for these to become more radically different absent the internal pressure created by a cultural merger with another people speaking a truly different language. Where such a merger happens, a new language is virtually guaranteed within three generations. And it has to be a full merger: widespread intermarriage, a coming together as one people or country rather than a land with two peoples speaking different languages who refuse to mix. AFAIK there is no language born of Greek and Turkish, despite the Ottoman empire.
[Answer]
If you have *isolation*, which includes a lack of things like nationwide radio and publishing, you will have the fastest change and different communities will change in different ways. If something happens to make them want to change, you are still talking a few generations to complete it. If each generation makes small changes, it will take much longer.
So realistically speaking, plan on 3 generations **minimum** if all the conditions are right.
It can take longer, if there is nationwide communication or standardized education. If teachers are being *perscriptive* it will hold changes at bay.
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So in many a fantasy world mountains, or in some cases a particular mountain that play an important role in the story.
Maybe it's the seat of the gods or hosts a hidden Shangri La, you get the idea.
Often times one mountain stands alone (a la Erebor) or one mountain stands significantly taller than all the rest.
In my world I have a mountain range that with a few exceptions splits an entire continent in half. I would like one mountain to stand maybe a third taller than all the rest.
Style wise (geologically) the mountains should resemble the rocky mountains in the US. What I want to know is can a single mountain stand out and be in the range of 50% taller than the rest of the mountains in the range.
* For the sake of this question assume the average height is somewhere in the neighborhood of 12,000 feet (3657.6 M) tall. I am looking for one mountain to clearly stand out and be in the neighborhood of 18,000 feet (5486.4 M) tall.
Can this wide of a range be supported?
[Answer]
That sounds very similar to the [Alaska Range](https://en.wikipedia.org/wiki/Alaska_Range) - a "large" amount of peaks in the 10-13 kft range, with [Denali](https://en.wikipedia.org/wiki/Denali) at over 20 kft, towering far above the others.
[Answer]
**DISCLAIMER** I'm not a geologist. I would love to have one correct me on the following.
A lone mountain significantly higher than its surrounding is very likely a volcano. Bear that in mind.
A long mountain range running through the continent is likely a scar of a plate collision (consider [Ural mountains](https://en.wikipedia.org/wiki/Ural_Mountains) - now rather old and worn out, but they were higher once).
Before continents collide, there should be a sea between them - and the edge of that sea was a [subduction zone](https://en.wikipedia.org/wiki/Subduction) during its demise.
And volcanoes are quite common in subduction zones (think Japan). One thing that bugs me is that subduction zone volcanoes typically form arcs and chains rather than lone big mountains, but maybe there are exceptions.
[Answer]
It's certainly supportable. It sounds like the range that your describing though is more like the [Mahalangur section of the Himalayas on the Nepal-China Border, home of the famous Mt. Everest](https://en.wikipedia.org/wiki/File:Nirekha.jpg). The geological history of the area is (IIRC) that India was a separate continent that slammed into Asia which caused the ring of mountain ranges to appear after Pangea had their break-up. You could use the same history for your continent - originally two, but collided years ago, causing that mountain range to occur only in the middle of continent where the collision happened.
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So an area has a bunch of dragons. These dragons are intelligent, but instinctively solitary (that is, the way they feel about living in a group is analogous the way a human would feel about living alone) and therefore do not have a very integrated society. Usually, a single individual lives in a 'territory' and only interacts with others as necessary, although the concept of living in a group is not alien (again, roughly comparable to the way a human would think about living alone). Communication is not a problem.
How would these dragons be forced into organizing themselves to fight a war against a nearby nation of humans (medieval technology)? That is, what kind of threat would said humans need to pose to incentivize an organized response?
Note: I am not asking whether this scenario is viable. If you do not think it is viable, and have a reasonably similar alternative that is, please share it. Otherwise, please do not answer with some version of "they wouldn't."
[Answer]
The situation here seems to have an easy solution; the humans must present a threat that the dragons *must* respond to, but *requires* coordinated effort, such as:
* mass egg theft or mass egg extermination (dragons lay eggs, right?). If the dragons think every human is out to rob/destroy their eggs, they all need to respond to the threat. Warring against the humans seems a reasonable thing to do in this situation.
* incarceration/subjugation of dragons on such a scale that a single dragon doesn't stand a chance. It's hard to imagine a Smaug-like dragon getting beat by a bunch of humans, but I'm afraid you didn't say how large each dragon is.
* All humans are driving off prey/dragon food. (I would think humans *are* dragon food, but I don't know about your dragons.)
The other way to get dragons to coordinate with each other in a war is to individual motivate each dragon. This could be:
* Each dragon who wars gets so much money/food/slaves
* Dragons who kill of humans have some social or other incentive. For example: [Trogdor](http://www.homestarrunner.com/sbemail58.html) is obviously a much more attractive dragon now that he's burninated all the peasants. He gets all the dragon ladies.
* Fighting this war is "right" in the minds of dragons.
I would also see such dragon warfare involving dragons doing the tasks that most armies send groups to do. Unless this is all-out, total warfare, in which case dragons must work together. (An uncomfortable arrangement for the dragons, I'm sure, but they can live with it, or die without it.)
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Consider the nations of middle earth reacting to Sauron's threat. Or the western powers, plagued by depression, as Hitler came to power in early 20th century.
At first dragons would seek to huddle in a secure corner. Prey upon man as convenient. But once the threat became too great (humans develop ground to air ballistas, perhaps), or a dramatic turn of events occurs *à la* Pearl Harbor, such as an elder dragon being slain, dragons would see cooperation as a necessity to survival. What a glorious story it would make, for the dragon broods to unite and burn away mankind, just as elves, dwarves, and men defeated Sauron at an apex of that Maiar's potency.
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Humans who prefer to be completely alone are rare, but they exist. Perhaps with dragons it's the other way around: perhaps, very rarely, a dragon comes along who is outgoing and charismatic towards other dragons. With a sufficiently Machiavellian mindset, perhaps such an exceptional dragon could convince the other dragons to put aside their instinctive indifference to one another and unite as a single force.
In order to do this it might be useful for this new dragon to have a scapegoat, an enemy for the dragons to unite against. Even if the human threat is not in reality all that credible or severe, the charismatic dragon might be able to drum up fear and resentment against them in order to achieve its aims. ("My fellow dragons, yet another of our number has been senselessly slain. How many more dragon lives must be lost before we put an end to the encroaching human menace once and for all," etc. etc.) Then the humans would suddenly find themselves under siege by a powerful force against which they are not really prepared to defend themselves - which might make for good drama if that's the sort of thing you're going for.
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One of the novels I've read reasoned out why dragons live alone.
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> Dragons are the messiah of destruction, wherever they go, destruction
> follows. That's why they are solitary, since they bring destruction to
> everything including their brethren.
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It is very hard to find reasons for an organized response from the dragonfolks.
One way to organize a dragon group is to have:
1. A Very Strong dragon leading the group
2. External Threat (Dragon extermination and such.)
3. Ancient Alliance with a race they go to war with them.
4. A Dance of the dragons (Dragons fighting one another for honor or whatever reason that requires an organized response.)
5. Beneficial to the race itself.
6. A horde of treasure that will benefit the whole race. (Dragon Hoard)
I'll edit this later if I find out more
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In a situation where you have people traveling between parallel Earths, where they dropped in with little ability to tell which Earth they are on, could checking cosmic background radiation be a sensible way to ascertain if this is a universe they had visited before?
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No. Interesting parallel Earths branched from ours within the last million years or maybe billion years if you want to look at totally alien life. The background radiation is coming to us from 14 billion years, with just a little modification from very large things in the way. If the timeline diverges a million years ago, the background radiation will still be from the time before that so be exactly the same.
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This is a very clever idea. Kudos to you for coming up with it.
The answer depends on a few things. First, the temperature of the [cosmic microwave background](http://www.wikipedia.org/wiki/Cosmic_microwave_background) is related to the [redshift](http://www.wikipedia.org/wiki/redshift) by the formula
$$T(z)=T\_0(1+z)$$
where $T\_0$ is the temperature we measure today, at redshift $0$. [Noterdaeme et al. (2010)](http://arxiv.org/abs/1012.3164), incidentally, remark that $T\_0=2.725\pm 0.002\text{ K}$.
[*Cosmology and Particle Astrophysics*, by Bergstrom and Goobar](https://books.google.com/books?id=CQYu_sutWAoC&pg=PA77&hl=en#v=onepage&q&f=false), mention that there is a redshift-time relation:
$$t(z)~\frac{2}{3H\_0\sqrt{\Omega\_M}}\frac{1}{(1+z)^{3/2}}$$
where $H\_0$ is the current Hubble constant and $\Omega\_M$ is the density of matter in the universe (part of the [density parameter](http://en.wikipedia.org/wiki/Friedmann_equations#Density_parameter)). Inverting the relation, we find that
$$z(t)=\left(\frac{2}{3H\_0\sqrt{\Omega\_M}}\frac{1}{t}\right)^{2/3}-1$$
You can then find the temperature as a function of time, matter density, and the Hubble constant:
$$T(t)=T\_0\left(\frac{2}{3H\_0\sqrt{\Omega\_M}}\frac{1}{t}\right)^{2/3}$$
Let's say that your intrepid travelers always visit each universe at around the same point in time - that is, they aren't bounding around from the Big Bang to the end of the universe and back. Then there's one basically one factor to measure, assuming all universes have the same age:
$$T\propto T\_0H\_0^{-2/3}\Omega\_M^{-1/3}$$
If you can measure this factor, you can probably differentiate one universe from another.
Also, don't limit yourself to the cosmic microwave background! There's a [gravitational wave background](http://en.wikipedia.org/wiki/Gravitational_wave_background) and a [cosmic neutrino background](http://en.wikipedia.org/wiki/Cosmic_neutrino_background), too. We can use information from the cosmic neutrino background (C$\nu$B), too; the mean velocity of a neutrino in the background [is given by](https://physics.stackexchange.com/a/268348/56299) (see [Safdi et al. (2014)](https://arxiv.org/abs/1404.0680))
$$\langle v\rangle=160 \left(\frac{m\_{\nu} c^2}{{\rm eV}}\right)^{-1} \ (1+z)\ \ \ {\rm km/s}=160 \left(\frac{m\_{\nu} c^2}{{\rm eV}}\right)^{-1}\left(\frac{2}{3H\_0\sqrt{\Omega\_M}}\frac{1}{t}\right)^{2/3}\ \ \ {\rm km/s}$$
In other words,
$$\langle v\rangle\propto v\_0 m\_\nu^{-1}H\_0^{-2/3}\Omega\_M^{-1/3}$$
which is a similar relation.
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After reading your title and question, I remembered an article I read about something [along these lines](http://io9.com/5714803/does-our-universe-show-bruises-where-it-collided-with-other-universes). Basically, there is a theory that the cosmic background not only provides hints that there was a universe before the big bang that it also shows "bruising" where it has collided with other universes.
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I am afraid that it would not be very practicall unless the situation were very specific.
Note: I use terminology that is original according to Wikipedia, because I find it more logical: the Universe is everything and multiverses are big parts of it (in this case looking like the classical image of the Universe in modern cosmology).
Mean background radiation temperature depends on the age of the multiverse and expansion rate and for this temperature to change significantly, the whole multiverse would have to be so much different that the existence of Earth-like life could be hard to justify.
More precise measurements of the mean temperature and deviations from it require advenced satelites collecting data for a longer time unless you assume a new, very advenced technology. Besides, if the multiverses we visit were globally similar, even such measurements would not show differences - such differences would mean that totally different galaxies exist now far away. If you assume that only the Earth is similar and for example jump technology allows to jump to almost Earth planets that can appear in very different multiverses (it could justify even very different multiverses from the previous paragraph), we could distinguisch them by looking at other planets in the solar system, stars (very easy at night if already the visible constelations are different and the traveller knows them) or other galaxies (with a telescope) unless you declare that all near space is similar enough that it is the background radiation that is easiest to distinguish with available technology.
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How would human culture and civilisation develop if placed onto a planet permanently psychoactive, e.g. because of low (but inevitable) amount of LSD-like substance in either water or air? To simplify, let's assume that the planet is already terraformed, with a reconstructed earth-like biosphere, and that we send humans there without all the technology needed to mitigate the effect
(i.e. they have to live as is and use no air filters nor antipsychotic drugs). Or just grow humans with an autonomous space-probe, assuming they will develop some culture on their own.
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As previously said, it will depend a bit on if the citizens eventually will build up a tolerance to the substance. And while I'm not an expert, I'd guess humans living in a such environment would have developed kidney or liver like organs all over to body to filter blood before it enters critical organs, or maybe the organs themselves would develop to protect themselves. After all, it's quite unlikely that our bodies wouldn't evolve to handle the environment.
Some fun ideas:
What if the effect is seasonal? If the substance is carried over populated regions during rain seasons or rare weather phenomena, the inhabitants might not become immune. This occasional high could cause the citizens to fear rain or water. And there's even the chance that they would enjoy the high and there could be festivities or rituals which happened during these events.
A civilization without the right technology to prevent or analyze these seasons might develop religions to give meaning to the phenomena.
A war-like civilization might prefer to fight wars during these seasons, soldiers might not fear death or become paralyzed if injured.
If the high was seen as an unpleasant phenomena, the civilization might spend all of their resources on trying to fight or avoid it. Maybe they would attempt to pollute the forests or seas in the hope of ending the phenomena. A technology loving society could focus on building hubs which are isolated from the environment, environmental suits or large space stations. Low tech avoiders could try to escape to areas on the planet which aren't as effected and this alone could cause an interesting structure inside the society. Those in power might spend large amounts of their resources in order to live on polar caps, the top of mountains, deserts or deep underground if these places offered shelter from the psychoactive phenomena.
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Like lots of drugs, LSD users fairly quickly build up a tolerance. Searching for long term LSD, you can quickly confirm that that continuous LSD usage dosing over a few days results in such tolerance that the result is effectively null. So, for most people, there would be no net effect.
No controlled studies for in utero that I am aware of (they would be unethical) so there could be development issues that are unknown. But it is certainly possible that this could result in more birth defects, etc.
Since the posited scenario would not have acute dosage, the incidence rate of reported strong effects (insanity, flashbacks, etc.) would be very low. A small percentage of the population may experience these however as drugs effects are quite variable.
Over, surprisingly little effect on societal development for environment LSD.
Now, suppose instead of LSD you have a similar drug in terms of psychoactive effect, but that no tolerance is built up to the effects. The effects would depend upon the effective dosage level. I.e., a mild LSD effect would not affect society drastically, i.e., there are lots of high-functional regular drug users. A certain percentage of society would not be highly functional, but since the effects are completely persistent, the society would simply be used to it, i.e., it is just the way it is. A certain percentage of our society is non-functional, we just deal with it. If the dysfunctional population was twice as large as ours, there would not be a significant difference.
If the effective dosage was very high, society would be more like the zombie apocalypse -- very few functional people and they are focused more a basic survival than development. It is still likely that over time, genetic drift would result in an increasing percentage of the survivors would be functional at the high dose rate.
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Assuming being under drug influence is not advantaging and evolution keeping the most viable members alive able to reproduce, I think that the society would eventually not be very different from ours. People would merely end up immune and they would certainly develop some biological symbiosis with this compound.
I think that it is unlikely that your population would survive to this though.
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Let's suppose all fundamental necessities are freely available and that the population is prosperous.
Let's also assume that the population does not become resistant to the effects or else this question is pointless.
Social co-operation would be limited because of a distorted perception of actions and consequences. For example when Fred does something nice to Bob, does Bob correctly interpret Fred's action? And if he does, does Fred correctly interpret Bob's reaction? If this feedback loop is broken then what social lesson has Bob learned? None.
I would expect that people would behave selfishly and without regard for the consequences; more or less the way that actual drug addicts behave on earth.
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No matter the dosage we forget some people affected wouldnt be able to deal with the audible and visual and would need people whove gone through intense 'journies' by themselves to 'show' you how to come back to reality in a good concious mind where the individuals felt safe. Itd be as if you were setting up 'guides' for 'tours'.
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This is a question I've been thinking about for a while now.
Dragons are, by all observances related to the reptile family, (or maybe lizards) either way these are cold blooded animals. Common places to see dragons are on mountain tops, flying high in the sky, "from the North" etc. Reptiles are cold blooded, and these are large reptiles. So I wondered:
How would one explain the 'evolution' of fire breathing?
I've also come up with an answer, which I will post, but I wanted to see how it would stack up with answers given by the imaginative bunch here.
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As discussed in [this article](http://www.stufftoblowyourmind.com/blog/monster-of-the-week-the-fire-breathing-dragon/), which references an [article from Discover Magazine](http://discovermagazine.com/2013/dec/20-how-to-explain-your-dragon) and [one from Scientific American](http://blogs.scientificamerican.com/but-not-simpler/2014/01/02/smaug-breathes-fire-like-a-bloated-bombardier-beetle-with-flinted-teeth/) on the same topic, a reasonably plausible way for an animal to breathe fire would be by mixing some combination of body chemicals that produce a flammable chemical, ignited with a spark created in their mouth. The article quotes some scientists imagining how it might work:
>
> According to paleontologist Henry Gee, dragons might biologically synthesize diethyl ether. Here’s his quote from the Discover Magazine piece:
>
>
> *“Yeasts and other organisms produce ethanol as a waste product, and there are bacteria that excrete sulfuric acid (they’re responsible for corroding concrete). I could imagine a microbial community in which diethyl ether is made as a waste product and exploited by dragons to breathe fire.”*
>
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> As the dragon spews this chemical cocktail, all it has to do is generate a spark to light the flame. As Kyle Hill suggests in his Scientific American piece, this might be achieved by mineral coatings on the teeth or ingested rocks and stones in the beast’s gizzard.
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The article notes a somewhat similar case, the Bombadier beetle which has "evolved to squirt an explosive stream of heated venom from their abdomen". They do this by combining hydrogen peroxide from one part of their body with hydroquinones from another part, which when mixed in a special "reaction chamber" creates a strongly exothermic chemical reaction which "generates enough heat to bring the entire mixture to a boiling point". Looking at the [Bombardier article on wikipedia](http://en.wikipedia.org/wiki/Bombardier_beetle), there's a discussion of how it evolved:
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> The full evolutionary history of the beetle's unique defense mechanism is unknown, but biologists have shown that the system could have theoretically evolved from defenses found in other beetles in incremental steps by natural selection.[7](http://en.wikipedia.org/wiki/Gastrolith) Specifically, quinone chemicals are a precursor to sclerotin, a brownish substance produced by beetles and other insects to harden their exoskeleton.[9] Some beetles additionally store excess foul-smelling quinones, including hydroquinone, in small sacs below their skin as a natural deterrent against predators—all carabid beetles have this sort of arrangement. Some beetles additionally mix hydrogen peroxide, a common by-product of the metabolism of cells, in with the hydroquinone; some of the catalases that exist in most cells make the process more efficient. The chemical reaction produces heat and pressure, and some beetles exploit the latter to push out the chemicals onto the skin; this is the case in the beetle Metrius contractus, which produces a foamy discharge when attacked.[10] In the bombardier beetle, the muscles that prevent leakage from the reservoir additionally developed a valve permitting more controlled discharge of the poison and an elongated abdomen to permit better control over the direction of discharge.[7](http://en.wikipedia.org/wiki/Gastrolith)
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So you could postulate a basically similar evolutionary sequence for dragons, imagining they originally evolved from smaller ancestors which faced dangers from predators, and these ancestors originally started upping the levels of some of these chemicals (ethanol and sulfuric acid, in Gee's scenario) in their body as a natural defense. Perhaps the greatest concentrations could exist in their stomach since Henry Gee suggests in the Discover article that they could be generated by bacteria, and the stomachs contain lots of those. If they were originally herbivores who had evolved a [multichambered stomach](http://www.macroevolution.net/ruminant-stomach.html) like cows and other [ruminants](http://en.wikipedia.org/wiki/Ruminant), one chemical might be more concentrated in one chamber while another chemical might be concentrated in a different chamber (alternately they might have evolved to cultivate microorganisms which produce toxic chemicals in their salivary glands, since this is [thought to be](http://blogs.scientificamerican.com/guest-blog/biting-the-hand-that-feeds-the-evolution-of-snake-venom/) the evolutionary origin of venom glands in snakes).
If they had already evolved higher concentrations just so predators would be deterred from eating them, then this might later evolve into a strategy where they vomit up the chemicals of their stomachs when threatened, as a further deterrant. If there was continually selection on this, eventually they might evolve to produce very explosive reactions like in the bombardier beetle. Then, as the Scientific American piece suggests, they could evolve to strike sparks and ignite the chemicals in their mouth by striking together mineral coatings on their teeth, or spitting out [gizzard stones](http://en.wikipedia.org/wiki/Gastrolith) to knock against each other and create a spark (gizzard stones are ingested by chickens to help with digestion, and sauropod dinosaurs are thought to have done the same thing).
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What if the 'fire-breathing' came from not from a weapon but for survival. Being a large reptile helped it survive cold climates by having more body mass, but it still wasn't enough! So it started chemical reactions to warm itself from the inside. This warmth is spread out to the rest of the body to help it act as a 'homeotherm'. But it continued to increase the heat output to help is survive colder and colder environments (people were pushing back!).
Then it started belching fire, to relive the stresses building up inside. As they grew in size it also got harder and harder to fly, so by belching the fire at the ground starting small fires, prairies, forests; they could create thermals to help lift itself into the sky. The dragons that survived were the ones with better heating systems and the ability to fly better, so the 'heating' units got larger and more powerful. Until we get the dragons we see today!
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**Fire breathing developed as a way to help raise their young.**
Being reptilian, dragons lay eggs, but eggs need warmth to mature.
Because dragons are solitary creatures, and because dragons will eat other dragons eggs at every opportunity, and male dragons will consume their own eggs if given the chance, female dragons do not have anyone to share nest sitting duties with. And since dragons spend a lot of time in cold areas like caves, mountains and such, it was really hard for them to get away to hunt during breeding season.
Like other reptiles, proto dragons had chemical glands in their mouths containing poison and other chemicals, and over time these chemicals developed combinations that would react to each other to produce heat. The proto dragon would use these chemicals to warm the rocks around the eggs so they could get away to hunt, and since they didn't have to fast during egg laying season they became bigger and stronger than other dragons.
Over time these chemicals became more and more reactive until combustion would occur when they mixed.
This is the major reason why dragons from tropical areas are smaller and don't breath fire. See komodo dragon as an example of this. They have the venom glands of their northern, cold weather cousins, but because of the climate they never needed to develop fire breathing.
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**Fire-Breathing as a Heat Dump**
You said it yourself:
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> Common places to see dragons are on mountain tops, flying high in the sky, "from the North" etc.
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>
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Dragons are from cold areas. What if they **need** to be cold - they die if they get too warm? Some sort of metabolic process that either fails or self-destructs at "high" temperatures.
Then the ability to dump heat rapidly becomes a survival mechanism - during warm periods they can take the environmental heat and breath it out to keep themselves cool.
This works better with magic - scientifically there are better ways to dump heat - but you might be able to stretch it either way. Maybe there are periods where it gets extremely warm, and environmental cooling (like sweating) is insufficient, so they need something active.
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One simple solution : cooked meat is better than raw meat. Cooked meat is easier to chew and to digest and cooking destroys most bacteria, parasites and toxins in the meat.
So dragons able to breathe fire would eat better and avoid some infections caused by the bacteria usually found in their meals. This gives them an advantage over dragons that can't cook their meat and so the genes allowing fire breathing become dominant in the dragon population thanks to natural selection.
You could also imagine sexual selection : dragons could favour fire breathing partners since cooked meat ensures a better survival rate for the young.
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I have been trying to imagine a world which was also created by a Big Bang. Following is something that I have created so far:
Another planet which was created also has species like us but they live in a tougher environment with high atmospheric pressure and more exposure to the sun; they have features like us but instead of skin, they are made up of hot glass. Why? Because slowly with the passage of time and exposure to too much heat, their skin evolved from something like ours to hot-glass-like. The color faded away. The skin became harder and it became glass-like.
My questions are:
* Will they not break every time they fall down or collide with each other?
* How can they avoid being so fragile?
* How can people with skin made of glass exist without constantly breaking?
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Presumably they'd still have a cellular structure? And the skin would be produced by those cells? If so there is no real issue.
Glass is actually pretty tough. I think that being as hard as steel is fairly normal for glass. The reason glass is normally fragile is because: One, it is non-elastic, instead of distributing and absorbing impacts, glass absorbs impact energy by the weakest spot breaking. Two, normal glass has nothing that would stop the resulting fracture from spreading.
For the glass people, neither would be an issue. The bioglass generated by separate cells would not really fuse together, resulting in a similar scale structure to what humans have. As such impacts would be absorbed by the soft cells under the skin and by the friction of the glass scales to each other. Additionally the fractures could not spread across scale boundaries.
In fact, since each scale would have several cells generating it and the cells would die, be included in the bioglass, and replaced, the skin would have a slightly flexible composite structure even at scale level. So even when the impact broke a scale, only a portion on the top of the individual scale would be lost.
The bioglass might actually be pretty good protection. The only real issue is that the biology needed to generate it is pretty implausible.
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In a fantasy world (a D&D setting, basically), how would an open underwater town populated by an assortment of mer-people deal with waste disposal? A few details: the town in question is a part of a larger above-ground settlement. They mainly trade fish for tools and other surface products. The dwellings are mostly carved/shaped into the coral reef in the shallow waters. The population is relatively low, around two thousand people, and likely spread-out - less an urban center and more a farming village.
Technology is, again, D&D-like, which is to say pseudo-medieval, as useless as that statement is. This being a fantasy world, "magic" could be the answer to everything, of course, and I suspect it will be needed to some extent. But I'm more interested in low-magic, somewhat natural solutions to the simple question: where does a merman poo?
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Where do fish poo? It all falls down. And goes into fertilizer.
Maybe make sure you've got ridges on the ground, so any tides or water movements don't send it all everywhere.
Metals and other things get recycled heavily, since they're not common, nor easily accessible. Coral, bone, etc, get tossed on a rubbish heap, which some animals probably like to cannibalize for eats. Other organic refuse gets eaten by scavenger fish or crabs.
For indoor use, probably have designed funnels which focus outside water motions (tides, etc) to do suction and removal of things (garbage disposal chutes & *ahem* wastewater).
Remember that all of your mer-toilets have three seashells...
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An ocean current could be used to keep fresh (as in, new, not as in saltless) water flowing through each house like a gentle, cleansing breeze, cleaning everything.
Slightly more advanced, the house design could funnel those parts of the breeze used for waste, into the "sewers" by the leeward side of the house.
Magic also works, of course.
In fish tanks the way it's done is a constant water current into the "sewers" (the gravel), and culturing cleaning fish, snails, weeds, etc. So, very biological coral-homes, like the tree-homes of the elves, could consume the waste products.
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I think if you have a merfolk population as 'part' of a human city/town an even bigger issue would be how to keep the human waste out of the mertown? Humans sent their waste into the rivers and oceans for a long time. larger cities would make it almost uninhabitable for merfolk if certain precautions weren't taken on both sides. The first would be not to put the mertown in a delta, but around the bend. They would want a little current to help carry things away, but not to bring the sludge of the humans into town.
Their own waste of course would likely try to utilize currents, maybe even create artificial currents to carry away waste from the settlement.
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I think you should remember that it is only pretty recently that human society managed to do something more sanitary with their waste than dumping it in the street, indeed in some unnamed parts of the world, this is still pretty much what happens today.
As others have suggested there probably wouldn't be any sanitation other than a strong current.
They would probably be a lot less squeamish about it than you imagine.
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In Hellboy 2, the titular protagonist and his party face up against a so-called 'Golden Army', which consisted of golden colored automatons who could constantly rebuild themselves after death. For my setting, I have implemented a similar thing, albeit on a larger scale.
So basically, my question is this - assuming the required mechanical strength to lift and move easily despite the weight, how effective would sentient clockwork soldiers literally made of gold be? I know gold is a soft metal, but surely you couldn't just slice through a lump of gold with a sword, could you? Also, they would make terrible swords, but their increased weight could still kill you with a bash to the head, right?
Edit: For clarification, the automatons are made of nothing but gold, but are not one solid piece. They have sculpted golden armor, but are essentially hollow inside, with cogs and gears (also made of gold).
Edit #2: Also, don't worry too much about whether or not they work. The question assumes that they do. I'm just asking about their martial prowess.
Edit #3: I'm starting to get the feeling gold is even worse than I originally assumed...
Edit #4: Alright, lets allow alloys or even non-gold metals, so long as they are gold-coloured.
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Unfortunately for you my friend, the [gold-colored nature](http://en.wikipedia.org/wiki/Colored_gold) of gold is extremely dependent on the purity of the gold. Any and all alloys of gold will always not have the same [lustre and color of gold](https://engineering.stackexchange.com/questions/470/could-a-gold-second-metal-crown-be-created-that-would-pass-the-archimedes-test).
Fortunately for you, gold is a metal, a pretty inert metal at that too. What this means is that your metal men can be made of whatever it is that you want, and you can then coat them with a very thin layer of gold. [The gold can not be too thin](http://en.wikipedia.org/wiki/Colloidal_gold) however, otherwise you may have a problem with the appearance again, gold is fickle that way.
For your metal men to be be strong and powerful, you would then need to pick a metal. My personal favorite metallic element of all time would be Iridium, and in fact can be quite useful when combined with gold. Iridium can be used, [when alloyed with platinum](http://en.wikipedia.org/wiki/Iridium#Industrial_and_medical) to make it much harder than before, up to 10x harder.
With an Iridium skeletal structure, gears and possibly muscle fiber, and a coat of gold paint, your metal men should be plenty able to hold themselves decently fine in combat. One thing that may happen a lot however would be that they would get a hillariously large ammount of chipped gold flakes whenever they strike or are struck. Actually that may be a pretty good combat mechanic for your metal men, as they fight, the air around becomes thick with gold chips, and that much heavy metal flying through the air can not be too good for the health of any meat bag enemies they face.
As for the Iridium in their bodies, they should pretty much reign supreme over any steel clad enemies, if their self-repair is sufficiently good. Iridium is a whole 2.5 points higher than steel on the [Mohs Scale](http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness). As such, any cutting or thrusting attack on them with steel weapons will fail, as the steel is not hard enough. However, hardness comes with the price of brittleness. If a giant were to swing a giant steel zweihander at your Iridium core metal men, the giant's zweihander is liable to get blunt, but your metal men may risk getting blown apart. But they can pull themselves together, so they will be fine.
With that much Iridium and gold on the metal men, they would be incredibly heavy. [Over 1.5 tons per metal man](http://www.wolframalpha.com/input/?i=volume%20human%20body%20*%20density%20of%20iridium). With that kind of weight, they would pose an extreme weight hazard. A squad of a dozen metal men could easily collapse most simple bridges. It would not be too much of a stretch as well to say that they can easily launch themselves from very powerful siege engines directly into the enemy wall, causing huge damage to the wall, as the metal man is many times heavier than a rock, and several times smaller as well, which may allow a flung metal man to be capable of punching through the curtain wall of a castle.
Their immense weight and density can also help them be innately [hammer-proof](https://worldbuilding.stackexchange.com/questions/9117/hammer-proof-armor) without the need for any sort of special armor. In fact, the metal men would probably not need any armor or weapons. They could easily sharpen their arms into blades and charge into battle arm flailing. No weapon of steel would be able to deal with them easily, and their flailing blade arms would actually be capable of chopping through enemy weapons and armor. One thing to note is that they weigh 1.6 tons, and a human arm is roughly 1/6 the total body weight, so that would be a 260kg blade arm swinging about.
I would also like to note that I am assuming that they are powered by magic, and blessed by magic to be able to move their bodies exactly as fast as a human could, but they are 1.6 tons.
NOTE 1: Why is Iridium so heavy? Because it is in the Platinum family of elements, which go from silver -> gold -> platinum -> iridium, with each later stage being quite a bit more dense the one before.
NOTE 2: A fallen metal man would be worth USD 28,270,000. Considerably beyond a million dollar man
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They would be terrible martial prowess. Primarily because gold is soft. While it is unlikely a sword will 'just slice through them' they will dent easy. If all the gears are gold, a little extra stress and the teeth will start striping, cogs without teeth are 'frictionless' wheels. Good dents in the armor will also interfere with the inner workings.
My ring is an alloy and I've distorted it working in my shop with hand tools (while I was wearing it!) Pure gold is just too malleable. And if you think of making it thicker to handle stresses, you will run afoul of the square cubed law. The weight of the armor as it thickens will put a lot more pressure on all the working joints and cogs. Swinging clubs at reasonable speed is about what you'll get, expensive cave men, that can break themselves if strained too hard.
EDT: for edit 4, using a decent metal frame (even a brass alloy) would go a long way to making a decent automaton. Having the body reinforced with steel and plated in gold you will have much more success.
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Why not make the outside gold, while the inside is a strong metal? Sort of like their 'skin' is golder, while their insides are made of some other metal, which would be tough enough to allow them to dish out and receive a beating?
Think of the Terminator and his layers -- flesh and metal.
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[Question]
[
**Setting:**
* Earth, in the future, near 2060 or 2100
* Technology: a bit more advanced than ours
Armies and police forces are already using systems for [crowd control](http://en.wikipedia.org/wiki/Active_Denial_System). Some devices can generate discomfort or pain using sound frequencies or electromagnetic radiation (microwaves).
Most of these devices are made to reduce violent behaviours but, could they have a wider range of uses? Could they also trigger other emotions and ultimately, could they be used as a mean to control the populations?
Speculations: I imagine that a state could deploy antennas across the land to send the frequencies. Maybe they could target specific area instead of a wide area. Maybe they could have these devices in all buildings and could monitor the people to influence their behaviour in real time.
Would that be possible with the right technology?
[Answer]
## Brain Stimulation
For brain research and treatment, there are many forms of electrical brain stimulation ([EBS](http://en.wikipedia.org/wiki/Electrical_brain_stimulation)) including transcranial magnetic stimulation, and direct current stimulation. According to Wikipedia:
>
> A comprehensive review of EBS research compiled a list of many
> different acute impacts of stimulation depending on the brain region
> targeted. Following are some examples of the effects documented:
>
>
> * Sensory: Feelings of body tingling, swaying, movement, suffocation, burning, shock, warmth, paresthesia, feeling of falling,
> oscillopsia, dysesthesia, levitation, sounds, phosphenes,
> hallucinations, micropsia, diplopia, etc.
> * Motor: Eye movements, locomotion, speech arrest, automatisms, laughter, palilalia, chewing, urge to move, crying without feeling
> sad, etc.
> * Autonomic: Blushing, mydriasis, change in blood pressure and breathing, apnea, nausea, tachycardia, sweating, etc.
> * Emotional: Anxiety, mirth, feeling of unreality, fear, happiness, anger, sadness, transient acute depression, hypomania, etc.
> * Cognitive: Acalculia, paraphasia, anomic aphasia, recalling memories, "going into a trance", "out of this world", conduction
> aphasia, hemispatial neglect, alexia, déjà vu, reliving past
> experiences, agraphia, apraxia, etc.
>
>
> EBS in face-sensitive regions of the fusiform gyrus caused a patient
> to report that the faces of the people in the room with him had
> "metamorphosed" and became distorted: "Your nose got saggy, went to
> the left. [...] Only your face changed, everything else was the
> same."
>
>
>
Note that electrical brain stimulation relies on the patient wearing some type of device (electrodes, coils, a helmet, etc...) and then targeting very specific areas of the brain, sometimes through trial and error. I find it difficult to believe that any type of ranged transmitter device would have either the strength or the accuracy to consistently and accurately produce a specific effect.
## Sensory Stimulation
In addition to directly stimulating the brain through electromagnetic means, there is also a more straightforward means of getting "frequencies" into the brain. The eyes detect light frequencies (within the visible range) and the ears detect auditory frequencies (in the audible range). This suggests that messages can be implanted via audio-visual means, which, of course, is the case. In fact, it is far more likely that these means would be used, as they provide a far richer palette of options. Indeed, advertisers, film-makers, and politicians already use much of this. I'm going to break this up into a couple of categories.
* Linguistic: Control people's actions through words, either spoken or written. Includes rhetorical devices, used by politicians, and pretty much anyone that says (or writes) anything. Imagine giant billboards telling you to be a compliant citizen, or public speakers broadcasting pro-government messages. Could also be done through control of nes stations, social media, websites, educational system, rewriting history, controlling the "narrative", creating new derogatory words for one's opponents, etc...
* Symbolic: Control people's actions more subtly through non-linguistic cues, such as colors, shapes, sound palettes, etc... It may sound silly, but how many little boys in a toy store would dare to go down the "pink aisle"? Advertisers realize that we never grow out of this, and package similar products separately for men and women, allowing them to perform "gendered pricing". This would also include playing soothing music at train stops, which one of the commenter suggested. Or composing the soundtrack, and adjusting the composition and color balance of films. There's a lot audio-visual meaning that can be conveyed without language. Even gestures and facial expressions could fall into this category.
* [Subliminal Effects](http://en.wikipedia.org/wiki/Subliminal_stimuli): This can be done either linguistically or symbolically, but it involves sending messages that are below the threshold of conscious detection, so that the target is unaware of them. This could also include more traditional hypnotic suggestions.
* Physiological Effects: This could include things like bright flashing lights, or loud noises, being used to daze and confuse an individual (like a flash bang grenade). In some cases, this may also cause [seizures](http://www.wired.com/2007/06/mias-new-websit/).
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"Frequencies" is a bad way of looking at this. Both sound and EMR involve some sort of oscillation which we can measure the frequency of. They have about as much relationship to one another as the wheel base of a car and the orbital radius of the Earth.
The way crowd control devices like that work is by imparting energy to the senses (the skin, eye, ear) in a way that produces an intense sensation, swamping other sensations and causing discomfort, not by directly affecting the brain to produce an emotion. So no, you can't induce arbitrary emotions through the use of radiation at some particular frequency.
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It really depends on how fine a control you are referring to. As you pointed out there are frequencies they can use for crowd control. There are [frequencies](http://en.wikipedia.org/wiki/Infrasound) below human hearing with longer exposure, (even just the length of a song) can cause many different negative emotions including fear. So yes, I think there could be a bit of control with frequencies especially negative emotions, however, I don't think it would reach to being able to control your individual thoughts, at least not en mass.
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These shapeshifters - known as Doppels - aren't the stereotypical "blob of goo that becomes whatever it wants" shapeshifters. Instead, they're humanoids that can assume the physical appearance of another human, usually to steal their identity. What is the most plausible (or the least rule-breaking) way for them to do this, biologically speaking?
Some parts of this have obvious solutions. Color changes are a no-brainer - many animals use modified [chromatophores](https://en.wikipedia.org/wiki/Chromatophore?wprov=sfla1) to change their skin color, and it seems reasonable that they could also be used to change eye color. Hair changes can probably be accomplished using a way to grow it extremely fast, and then simply cutting and dying it (but if there's a way to do it purely biologically, let me know). Changing their gait and voice could be done with nothing more than good control of their movements and speech. What I haven't been able to figure out is how they could change their actual body shape.
Here's the specifics. Doppels can:
* Alter their height and the length of their limbs, up to an inch or two in either direction.
* Alter their facial structure to assume a wide range of faces, as long as the face has no major deformities (such as a missing eye).
* Alter their apparent weight within a moderate range (they can't appear malnourished or extremely obese, but most humans are within their range).
* Alter their muscle definition within a similar range.
Doppels can't change their apparent sex (unless having their other abilities would already let them).
I haven't decided how long the transformation takes, mainly because it'll be based on these answers. Doppels usually assume a person's identity for months or years at a time, so it doesn't have to be a quick and easy process, but ideally they'd be able to transform within a few weeks at most.
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Octopuses and other cephalopods change their shape and even texture using small regions in their skin known as [papillae](https://www.google.com/search?q=cephalopod%20papillae&rlz=1C1GCEU_enUS972US973&ei=RjHkYsrTFNufqtsPoa-2iAg&oq=cephilopod%20papillae%20&gs_lcp=Cgdnd3Mtd2l6EAEYADIGCAAQHhANMgUIABCGAzIFCAAQhgMyBQgAEIYDMgUIABCGAzIFCAAQhgM6BwgAEEcQsAM6BAgAEEM6CggAELEDEIMBEEM6BQgAEIAEOgQIABANOgYIABAeEAc6CggAELEDEIMBEA06BggAEA0QCjoHCC4Q1AIQDUoECEEYAEoECEYYAFCyEFj4RmDSXGgBcAF4AIAB5gGIAbUKkgEFNS42LjGYAQCgAQHIAQjAAQE&sclient=gws-wiz&safe=active&ssui=on), they can also change the color of their skin with cells called [chromatophores](https://www.google.com/search?q=cephalopod%20chromatophores&rlz=1C1GCEU_enUS972US973&biw=2133&bih=1041&ei=HjLkYpaoAtC4qtsPrYywwA0&oq=cephilopod%20chromatophores&gs_lcp=Cgdnd3Mtd2l6EAEYADIECAAQDTIECAAQDTIGCAAQHhANMgUIABCGAzIFCAAQhgM6BggAEB4QBzoICAAQHhAPEAc6CAgAEB4QCBAHOgoIABAeEAgQBxAKSgQIQRgASgQIRhgAUABYghhg_CtoAHABeACAAWqIAbwHkgEDNS41mAEAoAEBwAEB&sclient=gws-wiz&safe=active&ssui=on)
Adapting this to a humanoid with with one or more varieties of condition known as [Ehlers–Danlos syndrome](https://en.wikipedia.org/wiki/Ehlers%E2%80%93Danlos_syndromes). You would have the base for a fairly formidable shape shifter.
The speed of the transformations in cephalopods, color and texture, is quite striking. Indeed cuttlefish can rapidly alternate their colors in which can only be described as a psychedelic maner to "hypnotise" their prey.
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Most people don't know that muscles don't contract. They use what can be referred to as calcium ratcheting, with the muscle fibers sliding against each other instead of contracting. You could do something similar with the bones. Instead of having solid bones, they'd have interleaved bones, where they are several layers that slide against each other like intertwined fingers.
The cost of this would be that the shapeshifters would be more fragile. If you don't mind a much longer transition time, they could use osteoblasts and osteoplasts to release and freeze the bones in place.
To a certain extent, you could use natural swelling mechanisms in the soft tissue to bulk a person up, but you're going to have to get really clever if you want the shapeshifter to be able to increase its apparent mass by fifty kilos.
Head size would be a problem. The things would have to commit a lot of brainpower to shifting shape, which would increase its size. The head would unavoidably have a minimum size, and you wouldn't want the brain case to expand, but you could shift around the bones in the face.
Other issues would include hairiness and the shape of the ears. You'd also have a really tough time changing the ocular sockets, since you couldn't change the size of the eyes.
[Answer]
**1 Pseudo Bones**
Their bones are not actually bones, but dense muscle like structures that can change in length. Much stronger than most muscles we think of, but only able to slowly change in length as an integral part of them being so stable as to pass for bones in the first place.
**2 Water sacks/sponge organs**
Doppel's have skin which can be adjusted to be water absorbent in various areas, as well as a water absorbent substance within their bodies, and so allows for the growing and extruding of apparent areas of fat as local areas are allowed to become wet and swell, or the dopple can extrude all the water quicly and get rid of the apparent fat. It is worth noting that if you want them to still be possible, they still need to have body fat(assuming that they're at least adjacent to humans) and can actually get fat as a result. And so they won't be able to get rid of everything.
**3 Sexual organs**
Dopplers can already change their apparent sex though, if the dopplers where hemaphrodic this could be supplemented even further, with retractable penis further resulting in variability.
**4 Variable length vocal cords**
In continuation of the established topic, any voice changes would be supplemented if their vocal cords could tighten and relax to an extreme degree, and so would be able to mimic nearly any voice, barring ones that would result from damaged vocal cords.
Ummmmm, so, there you go.
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[
There are a bunch of questions here that require knowledge on ''which technology is a prerequisite for which'' (for example [here](https://worldbuilding.stackexchange.com/a/186744/79925), [here](https://worldbuilding.stackexchange.com/questions/183209/minimum-tech-for-agricultural-desalination) or [here](https://chat.stackexchange.com/transcript/message/55776244#55776244)).
I was wondering if there was ever any attempt to compile a comprehensive graph from these prerequisite relationships of human technology.
(More specifically, it would be a [DAG](https://en.wikipedia.org/wiki/Directed_acyclic_graph), as the ''prerequisite of'' relation is directed, and we can't have cycles.)
I understand that this is a complicated issue even theoretically (primarily as these relationships are not static, they evolve over time), and is downright impossible to completely answer practically (as the number of nodes and edges, and the research to correctly identify them would be enormous, for minimal practical value), but hey, it is fun, and people have done a lot of things for fun with little practical purpose, so who knows...
What I have considered:
* [Input-output analysis](https://en.wikipedia.org/wiki/Input%E2%80%93output_model) (in particular, input-output tables): these are widely [available](https://apps.bea.gov/industry/xls/io-annual/ImportMatrices_Before_Redefinitions_DET_2007_2012.xlsx), but are at sector-level, not individual technology-level, and they also reveal nothing about the ''prerequisite of'' relationships.
* [Material requirements planning](https://en.wikipedia.org/wiki/Material_requirements_planning): it is very close to what we need, but it is too microscopic, it is about components required for a product, not technologies required for a technology.
* [Technology tree](https://en.wikipedia.org/wiki/Technology_tree): this is close to what we need, but the concrete examples in games are widely stylized and simplified (show several order of magnitudes smaller number of technologies than in reality).
[Answer]
### No. Because technology can be subdivided into ridiculously small units.
Integrated circuits are a technology. Humanity researched ICs successfully in 1959.
But we've come along way in 60 years - we couldn't make a 64 core cpu in 1960. So it's obvious we need to subdivide "IC" into many sub technologies.
Just where to subdivide is a mess. We can do it based on transistor density, we could do it based on trace width, or various milestones in there.
You'll end up with various milestones of ICs that go into details far beyond what you'll need. Do you really care about 2d, 2.5d, and 3d fabrication technology as their own discrete technology? Do you really want to have 19 and 14nm circuit printing as separate technologies?
What about a new design principle for the IC? Or a new algorithm to automate the layout? Aren't all of these their own technology?
And we forgot about old technologies that are still improved upon. Writing is being improved upon (New words are added all the time, did we research "lol" and "brb"? - textspeak was a new way to communicate so deserves to be a technology. And is every release of the unicode standard a new tech? Are new emojis "researched"?), ceramics and clay have advancements even now yet we researched them thousands of years ago. Every day I get something in my feed about a new plastic that revolutionises 3d printing - plastics been around for about a century and theres new technologies coming out all the time.
Python 3.9 came out today, that has many new features, some of which I've never seen before in any computer programming language. That's a new technology in my opinion.
Your technology tree is actually going to need dummy nodes to avoid cycles, as there are technologies that depend on themselves. An example is C++ compilers - "Clang version N" is built by "Clang version N" so has a self dependency. Resolving this is [possible](https://en.m.wikipedia.org/wiki/Bootstrapping_(compilers)) through some clever intermediate builds.
Your technology tree will basically be the worlds list of patents (expired and active, plus some for things like "fire") sorted topologically. This would be a massive project, and out of date as soon as its finished.
[Answer]
**Maybe with AI for modern times in a patent mapping way**
Thinking of a technology tree like in a game with prerequisites for each technologic step is incorrect. Many technologies can be invented via different routes with different prerequisites. For example, chemicals can be created via different synthesis processes making the end result the same but not how you get there.
I think a better way to see the technological landscape is like a network with all interconnected relationships. Some technologies have hard prerequisites but most have hard to soft connections. For example, for a rocket ship you in principle would not need knowledge of a combustion engine (we might have gone to electric engines straight away), but it will probably help. You would need knowledge of propellant however to get your rocket of the ground.
The best way to see interlinking between technologies is to look at the connections between the scientific papers written and what articles they refer to. Already there exists AI that map all interconnections between articles and define the keywords as technology field. An example of such mapping based on patent mapping for the 3D printing field is shown below.
[](https://i.stack.imgur.com/ZIoN3.png)
*Patent overlap mapping of 3D printing in 1985-2014 by research fields.
Source: [Huang, Y., Zhu, D., Qian, Y. et al. A hybrid method to trace technology evolution pathways: a case study of 3D printing. Scientometrics 111, 185–204 (2017).](https://rdcu.be/b8lFg)*
As can be seen it becomes quickly very interconnected. Another way to view it are heatmaps, read the article for an overview of more concepts.
Nowadays or in the near future AI should be able to do this for the complete digital scientific library to give a clear view of all interconnections between technologies. How to make it useable and understandable for humans is another question. Only the digital scientific library is crawlable for AI, but enough scientific history book are present that it will give a good overview of older technology.
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If I were to create such a graph, I would start out be extracting the relationships between Wikipedia articles concerning technology (which article links to which other article). The first challenge would be selecting the articles, because there is no general "technology" category. (You could exclude people and places, include certain other categories and work from there.) Then you'd have an undirected graph, which you have to manually edit to make into a DAG. (Maybe you could start with giving the technologies a date - the first date in the "History" section. Not always correct, but better than nothing.)
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I'm wondering what adaptions would be needed for an air-breathing, land-worthy homonid to be able to do deep-sea diving of at least 3,000 feet deep and for at least one hour. What changes need to be made to its physiology to make it deep-dive friendly?
I still want to keep the rough overall shape of a human, and still be able to function somewhat on land (in a perfectly Earthly environment) as well as underwater. I imagine long webbed hands feet and a lack of body hair would be the first things to change. What else is there? Air-filled spaces like lungs and sinuses buckle without diving gear, but this species would've found an approach around that. Maybe it has traits similar to dolphins and whales?
I'm trying to come up with a species of goblin that's designed to work as deep-sea soldiers. I know, it sounds crazy, but I need it.
[Answer]
**Probably like a Weddell seal.**
Funny enough, your humanoid matches very similarly the [weddell seal](https://oceanwide-expeditions.com/to-do/wildlife/weddell-seal)'s capabilities. Being able to dive up to 2000 feet and hold their breath for about 45 minutes, these seals use their great vision underwater and sensitive whiskers to locate the fish which they feed on. Additionally, unlike whales, seals are more or less still somewhat capable of coming to land, so we also have that going for your humanoid.
Before we go on, the necessary warning: humanoid shape is not a good shape for swimming, and considering deep diving with long periods of holding your breath, having a shape that hinders swimming will reduce the time you can spend underwater at best and cause death by suffocation if you try to remain the same periods at worse. Non-streamlined body = more resistance from the water = more energy spent to swim = higher levels of oxygen required for moving. Your goblin-soldiers, assuming a predominantly aquatic lifestyle, will most likely follow a similar path to all known cases of animals(reptiles, birds and mammals) which went back to the water: loosing potentially grasping limbs in favor of having fins and relying mostly on their mouths to do basically everything related to hunting and holding. Hope seal-shaped is humanoid enough, unless you're fine with having more issues catching food underwater and having to come up for air more quickly. The only way I see them being able to act more or less like a soldier is by adding retractable tentacles/limbs, meant solely for using tools/handling food they've already caught and remaining tucked withing the body when not in use, as to ensure a more streamlined, energy-efficient shape.
Now for the actual adaptations: the main problem with mammals (or any animal that once lived on land) when going for a deep dive is the fact that we use air. Our ear cavities and lungs are usually filled with air instead of water. That means that adaptations that prevent this involve strengthening these regions so that they don't burst under the pressure or damage nearby tissues. A recurring strategy that apparently is used both by whales and these seals involve exhaling and allowing their lungs to collapse, reducing buoyancy and solving the air issue somewhat. Another issue related to gases is the compression of nitrogen, increasing the amount of this gas dissolved in tissues and in the blood (also experienced by divers), which isn't too much of a problem, until you try to surface too quickly, causing this gas to decompress and form bubbles inside your body, which can be fatal. It's also speculated that the collapsing of the lungs done by whales also help mitigating this issue.
The second and third problems: heat (or lack of) and oxygen. Deep into the abyss is dark and cold, and not being a fish, you'll need a metabolism that can perform well in conditions of hypoxia (very little oxygen available.) in the case of the weddell seal, we see adaptations that allow them to have the oxygen consumption equivalent to 1.5 times their resting state. Your goblin will need to have adaptations like whales, who can store large amounts of oxygen in their muscles and blood, rather than in the lungs (the side effect of this in whales is blood and muscles that can look a deep red, almost black color). Other strategies already employed by deep diving mammals include reducing the heart rate and reducing blood flow to less vital parts of the body during these dives. In addition, your sea goblins will also need a good layer of fat protecting their bodies from the extreme cold of abyssal waters (in here its also advantageous due to the fat helping them to withstand blows, so a natural protection for your underwater soldiers).
So summing up, your goblins will need several adaptations to be able to have such a lifestyle,from their oxygen storage mechanisms to their ability to function with low oxygen to their ability to deal it extreme cold and pressures. Their lifestyle will require a streamlined shape, as it's the best way to facilitate swimming and reduce the amount of oxygen necessary for functioning, so the closest you'll have from functional grasping limbs in an aquatic, deep diving creature requires limbs that can be tucked into the body, something that can be seen in a way in [beaked whales](https://uk.whales.org/whales-dolphins/species-guide/cuviers-beaked-whale/), the owners of the deep diving animal record, reaching depths of over 6000 feet and holding their breath for over 2 hours, which possess flipper pockets to tuck their flippers inside, thus becoming more torpedo-shaped and energy-efficient. The closest I can see for them to be hydrodynamic while also being able to come to land is by being shaped like an alien seal with retractable tentacles (I recommend tentacles rather than extrab limbs because they're 1-pure muscle and very flexible and 2-soft and non hindered by bones, thus likely being easier to store withing the body). They won't be the best runners once they leave the water, but if they make use of their superficiall cuddly, sluggish appearance to draw their enemies closer to water, grabbing them with their 2-4 (I don't recommend more than that) tentacles and quickly dragging them to the depths. If the soldier escapes before they drown, freeze or burst, I can assure you they won't go far. The fat layer they'll need to withstand the cold will also aid them in withstanding blows and potentially aiding with cutting weapons and (if bears are anything to go by) even potentially some weaker firearms.
Beware the tentacled goblin seal.
[Answer]
**Hello There**
[](https://i.stack.imgur.com/pmhyo.jpg)
ProjectApex has pointed out all the secondary problems that come with an air-breathing creature diving to deep depths. You can overcome some of these by **not breathing air**. I propose your goblinoids are amphibious $-$ they have no problem breathing underwater but must remain damp to not suffocate in air.
That means they do not need to be 100% efficient swimmers. They have long webbed back legs for swimming and shorter front legs for grasping. They are much faster than a human, but cannot chase fish like a seal or flee from sharks.
Their main source of food is clams and sea urchins from the seabed. For sharks, they dive in big groups, with spears and tridents to dissuade the sharks. When they hit the bottom they spread out.
I should point out one big obstacle is **salt water**. There are only a few amphibians that can breath saltwater without getting poisoned. I don't know if this is a big issue, though, since amphibians originally came from the sea. Presumably they could re-evolve that ability.
[Answer]
They'd probably look a lot like King Shark from The Flash. Water is much denser than air, so the body shape will affect fighting in water much more than fighting in the air.
Stuff like fins won't really hinder fighting in the air that much, but will make it much easier to stay on course underwater.
The real question is, how do they breathe both air and water? It's also a trick question as lungs are a huge liability underwater. Animals like frogs, which can breathe in both air and water have lungs and can breathe [through their skin](https://www.burkemuseum.org/collections-and-research/biology/herpetology/all-about-amphibians/all-about-frogs#:%7E:text=Yes%2C%20frogs%20have%20lungs%20like,also%20breathe%20through%20their%20skin.&text=They%20use%20their%20skin%20to,the%20water%2C%20they%20will%20drown.)
Deep diving with lungs will always be dangerous. You've got a giant air pouch in the center of your body, that's a problem for deep divers. [The bends](https://www.emedicinehealth.com/decompression_syndromes_the_bends/symptom.htm), where your blood becomes supersaturated with gas would be one problem. Having your organs re-arranged (Somewhat [gory mythbuster](https://www.youtube.com/watch?v=LEY3fN4N3D8) video) by the pressure difference would be another.
[](https://i.stack.imgur.com/IU7Es.jpg)
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If people were about 1 foot tall and weighed about 1 pound, would we ever have made a reactor or an atomic bomb? Because critical mass doesn't change, the scale of the project to mine and process radioisotopes would effectively be >100x larger than in our world.
[Answer]
**No.**
At the size of a squirrel, the human brain would be the size of a nut (well, some people ...). To develop our society we need a brain capable of holding billions of neurons.
Trying to compress all 86 billion neurons into a smaller space will require immeasurably longer sleep time, having no more space in the life span of mini-humans except for eating and sleeping.
We would not have the fire, the wheel, the writing, let alone a society able to create atomic technology.
**Yet...**
You didn't say anything science-based! (=
Admitting some handwaving where the mini humans will have these conditions, they will form a society, something like the little ones at Gulliver Travels, the problem is only in the scale of the projects that they will be able to carry out.
Will they be able to work with metals, make forges, in order to build metal structures many times bigger than themselves, just like we build giant mining machines?
Per instance, this is a diesel ship engine:
[](https://i.stack.imgur.com/x6KWI.png)
It is also good to keep in mind that they will not have all the operations in our measure, the total necessary for the critical mass will be obtained within the capacity and technologies that they will employ. The energy demands they have will also be reduced.
With 1% of the mass and 1/5 of the height of average humans a Joule is equivalent to 500 "mini-Joules". 1 MWH for them is equivalent to 500 MWH for us. Other simpler sources will seem more plausible to them most of the time, unless they are at a technological level far ahead of what we are today.
[Answer]
I concur with Halthawe's *at first sight: why couldn't they?* answer.
**But Consider:**
Squirrelmen, being only a foot tall and weighing in at only a pound have very different materials & technological needs. Being relatively light & weak, they could easily make vast yet structurally sound edifices from wood, leaves, and bronze.
They could make a steam train entirely out of copper, brass, and wood. They may never even come to use iron, to say nothing of any more advanced metals. The brass rails of a standard garden railway (No. 1 Gauge) can easily support a hundred pounds or more, whereas a scaled up brass rail could never support the weight of a steel & cast iron locomotive.
**Answer:**
No. They never needed to get to enough of the intermediate technological points along the way. Even if the Squirrelmen discovered the physics & math that would allow them build The Bomb, they may simply not have the material to make it a reality.
[Answer]
Ignoring all the *other* issues caused by shrinking humans to the size of a foot, such as the fact that we'd be unable to function biologically and most likely wouldn't be intelligent to begind with...
**Yes**
It may be large relative to the 1 foot sized human, but it's still the same size compared to the deposits present on Earth, so the material is there, it just needs to be mined. A bit of extra work wouldn't slow down, say, the Manhattan Project from being developed.
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along with horses, [Orcs](https://worldbuilding.stackexchange.com/questions/168722/how-might-a-dark-lord-quickly-overhaul-a-civilization/168739#168739) have also bred giant Boars which they ride to battle.
[](https://i.stack.imgur.com/G7YrD.png)
these war boars have been bred to be the size of [Entelodont](https://en.wikipedia.org/wiki/Entelodont) with larger tusks and I was wondering in what field might these war boars be most useful in 13th century medieval warfare?
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**Formation Breakers**
Drawing from our own history, rife with war, may I mention that we have indeed used War Boars before, although more accurately, we called them [War Pigs](https://en.wikipedia.org/wiki/War_pig). They were used by the Roman army because, reportedly, elephants became very frightened by squealing pigs. They would light the pigs on fire or send them in large numbers at the war elephants, breaking their charge. As Li Jun has mentioned, they will also be great at breaking horse formations as well.
**Historical Weight Comparison, and Reality-Check on Boars as Mounts**
In our own history, we have bred pigs up to 2500 lbs, like the one below, Big Bill:
[](https://i.stack.imgur.com/8WUjK.png)
The largest wild boars ever caught can weight up to 700 pounds
[](https://i.stack.imgur.com/v9DBO.png)
If we compare that to the weight of a [warhorse](http://imh.org/exhibits/online/legacy-of-the-horse/horses-were-specifically-bred-warfare-and-chivalry/):
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> By the 14th century, an average warhorse would weigh between 1,200 and 1,400 pounds and stand approximately 14 to 15 hands. When the knight struck a conventionally mounted opponent, the impact could be devastating.
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Based on weight alone, orcs could probably easily breed boars from their wild 600-700 pound versions to match the weight of a warhorse. They would be devastating on the battlefield, and have an advantage over horses: their larger sizes would make it more likely for them to survive projectile damage from things like arrows. Alternatively though, they would be harder to fit with armor due to their large size, compared to a horse.
**Pigs Calvary vs Horse Calvary**
Pigs will eat anything. As such, War Boars would probably be useful in times where resources are short. Horses, on the other hand, require a special diet to stay healthy, and are [much more difficult to groom and care for](https://legioilynx.com/2016/12/15/grooming-and-care-of-war-horses-in-the-middle-ages/).
Boars cannot run as fast, or as long as horses. Boars should be used for short-distance charges, or properly timed ambushes, as they cannot be used to charge in from a long distance.
Boars do have one big factor over horses: fear factor. A boar has a more ferocious reputation than horses, and imagining a massive boar charging over is terrifying. This is definitely compounded by the large tusks, as a horse rider would generally prefer spears or lances, but a boar with tusks could easily skewer multiple people itself, combined with a terrifying orc warrior rider.
Boars also have another natural advantage over horses: leg structure. Horses have especially weak legs, which also cannot be armored. They can be easily disrupted with the use of caltrops or, anti-calvary weapons like the [zhanmaodao](https://en.wikipedia.org/wiki/Zhanmadao), and ancient oriental weapon made to chop the horse's legs. Horses also have a lot of issues with terrain, and are prone to pileups if their charge is stopped midway. Boars instead have better durability due to their legs being easier to armor, and are thus much more difficult to stop.
Boars are terrible for transport purposes, as they are not built for long distance like horses. They should not be used like traditional cavalry, as they are too aggressive. If this point can be solved with breeding over time, they might make good cavalry for shorter distance battles, but might never have as much mobility or endurance as a horse-based cavalry.
**Summary**
All in all, a boar as a mount is not as mobile or capable of long distance travel as a horse, but its ferocity and powerful natural combat equipment gives it the edge in formation disruption, even against larger animals like elephants. It is also incredibly durable compared to a horse, with less obvious weak points, making them difficult to stop once a charge is started. They are also easy to raise and feed (especially considering Orcs, who may or may not have a developed wheat industry).
These points support Boars being used as a sort of *defense force*. They can be easily sustained on many different food sources in daily life, can be released to break charges from the enemy on their own, can be set up for short charges and ambushes, and are not great for transport purposes compared to more mild-mannered horses. They also invoke a higher fear factor than horses, and can be *used to break apart formations* as well. Also, if they are established as a defense force in orc settlements, a large number of them can be kept, as *Joe Bloggs* has mentioned, "imagine all the food when a warboar ‘retires’!!". When they are not used for war, they can be *good livestock* for the orcs to raise, forming a cycle of sorts, and can be **quickly re-purposed for war when needed**.
A secondary tactic, would probably be a *swarm* tactic. They can swarm in with higher numbers than traditional cavalry, and are incredibly difficult for the enemy to stop, possessing less weak points than horses. This can disrupt and break enemy formations, and throw them into chaos.
If they are to be established as a proper cavalry attack force, the orcs must first find a way to properly rein in their aggressive tempers, and breed species of boar with higher endurance. If they are used as an attack force, they will probably retain their role as a formation breaker, rather than a mobile force, but will be incredibly deadly and very difficult to stop.
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Reattaching severed limbs is a recurring theme in many monsters, but never has it been explained HOW they reattach their appendages. I doubt the neurons would magically realign and begin to function normally, not to mention the exposure to bacteria and impurities that would risk infection. Whatever the method, reattaching the limb is definitely more energy efficient than regrowing it from scratch.
Some put their arms back together and wait for it to reconnect while others sprout a tentacle that links the severed pieces. Even trickier is reconnecting the head, which some invincible monsters but back on effortlessly.
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I think your self-repairing monsters' immune systems are very robust and protect them from bacterial infection. Their immune systems also might have several innovations. For example, we have a limb torn or bitten off, the stump swells immediately and blood vessels and arteries constrict. This is an automatic response to stop us from bleeding to death. But, that same swelling is counterproductive to healing when we merely get a deep cut or bruise since it slows the flow of blood carrying nutrients and such needed to repair the injury.
Instead, these self-resembling monsters, when they lose a limb, the body prepares itself for reattachment by flooding the area with a healing factor that stimulates tissue growth. If the limb is gone, it can regenerate, and if it is only lying on the floor its can reattach itself.
If the severed limb moves on its own, then the motor neurons controlling the muscles are part of the limb, and not in the brain like us. Our hearts are like this. The brain doesn't directly control the throb in our breasts. That is why a human heart can be transplanted and still keep beating.
And, maybe, there are a whole bunch of tiny brain-like structures in each limb that lie dormant until the limb is severed. But, their function is like a blind pup searching for its mother's nipple and will twist and turn and flop about to help the limb align.
And for the hard part, how the muscle fibers and nerve fibers realign themselves?
The image below is a long-chain molecule. There are lots in nature -- our DNA, and polymers like Nylon and Teflon for example.
[](https://i.stack.imgur.com/1YD6O.png)
To me, it sort of looks like a key. Now, imagine it looped in a wide circle. I think that would provide a mechanism for aligning the severed edges of tissues. If each half of the wounded muscle group, nerve bundle, blood vessel, etc was the other sides molecular complement then until the sections lined up, ionic forces would be weak. But when the 'teeth' of the molecular keys did line up, the powerful attractive forces would pull the sections together.
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# Magic
You put your finger on the answer in the question. No monsters who just push the severed body part onto the stump and have it reattach are adhering to biological principles. Once a body part is removed, reattaching it requires an active intelligence doing the work (ie. a surgeon), and permanent damage is still being done.
Creatures in nature who are prepared to lose limbs or body parts as defense mechanisms (some lizards, starfish, sea cucumbers, etc.) are not expecting to get them back, and have no mechanism to reattach them once lost.
So yes, a creature that can put a limb (or *head*) back on post-loss is using magic, or magic by another name (nanobots in the bloodstream, psychic surgery, etc.).
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# Ecological Niche
As far as I know, we do not know of any creature with a system to reattach severed limbs, because if you lose a limb, odds are that the same creature which separated your limb is going to finish you off. So if you want the creature to be plausibly "natural", you will first need to describe an environment in which it is likely to lose an *entire limb*, but also able to *retrieve it* mostly intact. Perhaps these creatures live in an environment with very sharp, glassy rocks which are easy to slip on, so that the main threat isn't predators, but rather accidental dismemberment.
# Reattach System
Most creatures have an immune system, which is a population of mobile cells which travel to where they are needed in the body and attack stuff. At the same time, most creatures treat "repair" as: "close up blood vessels and grow new skin". However, there is no real impediment to developing a "reattachment system" which is similar and parallel to the immune system.
Of course, the main problem is alignment. I think expecting the limb to just attach *and* orient itself correctly is really stretching plausibility. So I would stick with a creature that has prehensile limbs and *digits* (i.e., primates). That is, you want the creature to be able to place the severed limb in approximately the correct location. Even so, "close" isn't really "close enough" to reattach small blood vessels and nerves.
For precision, you need some way to mark up the piping and wiring so the repair cells know what to do. Fortunately, biology is really just a giant wetware information system, and there are many, many molecules which will do the trick. Just about every cell in every creature expresses proteins on its exterior. The body uses these proteins to identify "self". Adaptive immune systems use them to identify "invader". The reattach system can use them to identify "blood vessel 4e7h". Yes, every nerve and blood vessel, every muscle, tendon, ligament, etc. can be coded with its own unique identifiers. However, you don't really need them to all be unique. You just need them to be "locally unique". The creature itself should perform most of the alignment visually. Then, a blood vessel just needs to be unique relative to the few other blood vessels within a few cm of it. Thus, tags can be reused around the circumference of a limb, as long as they are adequately separated. Also, different kinds of tissues can reuse the same tags, as the repair system will need to identify tissue types anyway.
When a tissue with one tag is placed next to a tissue with a different tag, it can cause a hormone release which triggers pain receptors. So when the creature is attempting to position the limb, it simply rotates and moves it around until it minimizes the "contact pain". Pain nerves will tell it when the alignment is off, but the closer it gets to proper alignment, the more the pain signal quiets.
# Repair System
We know that the adult body harbors pluripotent stem cells which can differentiate into any other cell type. So repairing virtually any tissue type in vitro is at least theoretically possible just using biology we know about today. Once the tissues are adequately aligned, these cells just need to go to work, taking on the proper tissue tags and rebuilding the severed connections.
New blood vessels and nerves form all the time, but perhaps the biggest challenge is muscle. While animals can grow new muscle from scratch, when a muscle is severed, I am not aware of any creature that can reattach its own muscle fibers to repair a break. I don't think it's biologically impossible, but we don't have any models for it. Fortunately, bones also reattach and heal on their own all the time, with nothing more than a splint or cast (and for wild creatures, not even that).
The last challenge is sepsis. Whatever got into the exposed ends of the severed limb will end up on the inside of the body once the limb is reattached. The creature needs to clean it as much as possible. This is going to sound gross, but the most obvious way to do this is to lick the wounds. For the detached limb, that is easy enough. For the detachment point, the creature might not be able to reach it with its tongue. Even so, it will need to lick its paw/hand/foot/etc. and try to clean the wound before reattaching. Once it does, the immune system will need to rally and attack the interlopers once they have the advantage.
# Limits
While I can imagine such a system working for the loss of a single limb, I would imagine that blood loss and shock would prevent a happy outcome for multiple amputation. Of course, those limits are up to you, but real creatures which can "safely" lose a limb rarely lose more than one at a time.
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Do your monsters have a circulatory system? one major problem in reattaching limbs is that the thrombolytic response (which causes blood to clot) starts to seal up wounds immediately after they occur to prevent you from bleeding to death. Then, the opposite of limb re-attachment happens--the severed part of the body is sealed off from the outside world.
Your monsters need to have a better way to stop themselves from bleeding out after injuries, so that all blood vessels and nerve endings and tissues can be kept in tact and ready for immediate re-attachment. This means a huge fundamental change to circulatory systems. Also, they would need amazing immune systems like previous posters have said, as their body would be exposed to the external environment if they do not have an innate response to seal their body off from the world.
If they are indeed monsters, or aliens, then maybe they do not have circulatory systems like humans do. Even on earth there are alternatives to blood vessels such as just having pools of haemolymph in insects. Haemolymph is not as efficient as blood and poses severe size restrictions (no human-sized insects today, my earthling friends). If you could imagine a reasonably viscous ultra-high efficiency haemolymph analogue, the viscosity would reduce the need for an immediate clotting response, though again decrease the efficiency of oxygen transfer. There are a lot of trade offs to consider in "designing" such a monster, but never say never. In general, the simpler and the smaller the organism is, the easier it will be for that organism to regenerate or re-attach its limbs.
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So, I've heard that while Alcubierre drives might present a semi-plausible way of getting around the light speed limit (if you can get ahold of negative energy), they do so at the expense of creating backwards time travel. Is this an inevitable consequence of using such a drive, or just a possible way of using it? If you plan on using an Alcubierre drive to travel faster-than-light to a distant location, and then travel faster-than-light back to your starting point, will the nature of your drive mean that, no matter what you do, you'll have gone back in time?
I'm running off the assumption that, if there's a way to use an Alcubierre drive without violating causality, then I can handwave in an explanation about how attempts to use such drives to go back in time create insane amounts of radiation which vaporize everything inside the warp bubble, creating a practical barrier to use of them for time travel.
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**They just allow it.**
Superluminal time travel requires *two* FTL jumps in *two different reference frames* in order to return to your place of origin before you departed.
The Alcubierre drive actually makes switching reference frames like this quite easy- all you need is a powerful subluminal rocket engine.
Here's how to do it:
1. Fire up your Alcubierre drive to travel some substantial distance away from Earth, then turn it off.
2. Fire up your sublight drive, and accelerate until you're moving away from Earth at a large fraction of the speed of light, then turn that off.
3. Turn around, and fire up your Alcubierre drive again to return to Earth. You'll want to overshoot a bit, since when you drop out of warp, you'll be moving with the same velocity as you had when you turned the warp drive on.
4. Fire up the sublight drive again to slow yourself to a halt.
5. Done! If you've used the right speeds for both the sub- and superluminal steps, you'll now be in the past.
To prevent this, you can have your Alcubierre drive interact with some reference frame that all observers can agree on (e.g. the [Cosmic Microwave Background](https://en.wikipedia.org/wiki/Cosmic_microwave_background)), such that if it's activated while not stationary in that reference frame, it'll collapse into a black hole. That's your handwave.
Edit: [Here's a video from PBS Space Time](https://www.youtube.com/watch?v=HUMGc8hEkpc) showing how a ship with an Alcubierre drive capable of a maximum of 2x lightspeed can take a trip deep into interstellar space and return to Earth long before it was even built.
The video doesn't go into much detail about how the change of reference frame is to be done, but to my understanding, burning a more conventional rocket engine should do the trick.
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This is strictly Earth based. Would it be possible for a society to develop their own civilization underwater (nothing fantastical like Aquaman or whatever, but more of a grimy, hardscrabble existence where they've developed a food chain from geothermal vents, and physiological adaptations such as biolumination, reduced vision but ability to echolocate (just brainstorming).
What reason could this society have to come up to the surface to a post-apocalyptic Earth that's been ravaged by nuclear war and bioweapons?
Perhaps they're escaping from an ancient Lovecraftian entity that's been hibernating for eons, and the explosions from the bombs awakened it? Now the underwater denizens are escaping from it?
Or maybe their food sources are running out due to widespread extinctions in the overall ocean food chain, and they're forced to come up to the surface and try their luck there, which creates a conflict with the humans living aboveground? Essentially, the nuclear warfare led to the food chain and wildlife getting screwed up, so in a nice little bit of irony, it's the surface-dweller's fault that the ocean-dwellers are coming after their land.
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The decay and detritus of the surface dwellers is beginning to impact their society.
Leaking nuclear waste, mass mutating bioweapons, ash, all these things are threatening their own way of life. So they send expeditions up to the surface to explore our ruins, fix our leaking waste and scrub radiation, destroy our bioweapons.
This would only really need small scale surface missions and activity however as they would be trying to fix our mess. If you need mass movement, I think the ideas in your final paragraph are very good.
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A deep ocean society relies upon geothermal energy to live. What if, for reasons that don't have to be explained anytime soon in the story, the geothermal energy subsides to nothing at the ocean floor? Without energy, the community becomes unsustainable and has to go to the surface to get the energy needed to make food and sustain civilization. So, they migrate to the ruined land.
Perhaps the real cause of the declining geothermal energy is along the lines of the anime "[Darling in the Franxx](https://en.wikipedia.org/wiki/Darling_in_the_Franxx)" in which some other civilization, local or alien or arisen post-apocalyptically, has started to tap into and suck up geothermal energy from the Earth that is depleting natural sources.
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I can think of only two offhand... revenge or reclamation.
**Revenge**... they don't intend to claim the surface for themselves, after all, it is: horrible, hot, dry, the pressure is all wrong, the sounds are all wrong, the light is blinding and the sun is burning, the food is weird... the list goes on forever. The surface is such an utterly alien environment that they're just not interested in it, just interested in getting rid of the stupid primates who live up there to make sure that they don't get the opportunity to do the same stupid awful things all over again.
They don't *want* to be there, they're not going to stay there for long, and the sooner they can get back down to the deeps the better. They're angry at you personally, for ruining everything and making them come up to this arid hellscape, and they're going to make you pay.
If you've not already done so, there's relevant reading in *The Kraken Wakes* or *The Swarm* (the one by Frank Schätzing) or Peter Watts' *Rifters* series (available as [free ebooks](https://rifters.com/real/shorts.htm) from the author's site).
**Reclamation**... they used to live on land, or perhaps on the coast, but were driven away by human expansion, suffered badly from disease and pollution, gained a sort of mythical status rather than being taken seriously by the bulk of humanity and were ultimately scoured from the surface. Or maybe they *were* human, modified by some technological process or experiencing some kind of (at least partially) benign mutation, and were able to retreat to the oceans when the surface humans rejected them. Previous attempts to return failed, but not *this* one. This time the humans have been weakened beyond the ability to effectively fight back.
They may have adapted to their new undersea homes, but they came from the surface before and they've always wanted to return. Re-adapting to the surface world will be difficult, but they're biologically equipped for it and it'll come back to them in due course.
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Probably not so much... The ocean is huge, and the surface is utterly alien and extremely hostile to native undersea species. They'd move into shallower seas or coastal waters, at most. But to move from the abyssal plains to the surface? About as likely as you wanting to make the opposite journey and live in the dark and eat weird shellfish for the rest of your life.
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**Our old ruined stuff is still pretty sweet.**
Your submariners have cargo cults.
<https://en.wikipedia.org/wiki/Cargo_cult>
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> Cargo cults are marked by a number of common characteristics,
> including a "myth-dream" that is a synthesis of indigenous and foreign
> elements; the expectation of help from the ancestors; charismatic
> leaders; and lastly, belief in the appearance of an abundance of
> goods.[7] The indigenous societies of Melanesia were typically
> characterized by a "big man" political system in which individuals
> gained prestige through gift exchanges. The more wealth a man could
> distribute, the more people in his debt, and the greater his renown.
> Those who were unable to reciprocate were identified as "rubbish men"....
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Manufactured goods from the surface have always been valued in the deep ocean - things like plastics and refined metals have no indigenous equivalents. They are worth a lot and make excellent gifts. With the fall of civilization, vast troves of these things are now undefended. The submariners foray into the ruins to find loot - steel, plastics, glass and the like. These things still exist in abundance, but it is dangerous and scary for the sea people to come onto land and get them. If you succeed and bring back a good haul, it means you gain in wealth and more importantly prestige. It is worth the risk for some.
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Well, for Humans mass migrations (and the claiming of already inhibited territories) seemingly mostly were triggered by either the "homeland" becoming un-inhabitable due to climate changes and the shortage of food that comes with it or by aggressors driving the population out of their homeland en masse (maybe because they, in turn, are facing one of those problems in *their* homeland).
Also, IMHO, the founding of colonies in "foreign lands" by white settlers/colonists might serve as inspiration here.
Many looking for a better life (maybe because belong to a minority that's being oppressed in their native home), and too many just thinking they could make a good profit. If you go in this direction, maybe your deep ocean society only just discovered that there's inhabitable land *above* the surface. Maybe it just was never believed that there was any, maybe it was suspected or known, but unthinkable to go there until the need was strong enough, or there was a major shift in their society.
**Or**, maybe the land above and its atmosphere in fact just where not hospitable for them before the bio-nuclear Ragnarök.
Just a few thoughts :)
Edit: grammar
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Increases in atmospheric carbon dioxide causes catastrophic increases in carbonic acid in all open bodies of water, the decreased pH causes the pelagic food chain to collapse and a mass extinction event occurs.
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Here's a simple answer: curiosity. After centuries of rising noise and trash-dumping from the surface, the sudden silence might get them reasonably concerned, and start sending scouting parties above.
Question: can your submariners deal comfortably with the changes in light and pressure?
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I have a moon in my story that has a thin, deep gash or canyon that lies on its equator and spans the entire moon.
My original idea involved the sudden orbital decay of a ring system, caused by a sudden increase in mass from a few small-scale collisions. However, ring systems are invisible or nearly invisible as viewed from the side, which is the view it needs to be. **The gash should be faintly visible with the naked eye.**
My second idea was that the moon was captured by the planet and went through its ring system, but that causes the same problems as before.
I've done the calculations and the energy released from such small collisions from a ring system would not create craters large enough to be seen from far away.
**What are some possible ways to explain this equatorial gash? Good answers will provide scientifically plausible theories of the gash's formation.**
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I see three ways to go about doing this: **Go for something natural, but imperfect, like the Valles Marineris on Mars; cheat by using a small moon not in hydrostatic equilibrium, specifically a contact binary; or go for an artificial surface feature.**
## [Valles Marineris](https://en.wikipedia.org/wiki/Valles_Marineris) and [Rift Vallies](https://en.wikipedia.org/wiki/Rift_valley)
Valles Marineris is probably the most visually impressive rift valley in the solar system, being 4,000 km (2,500 mi) long, 200 km (120 mi) wide and up to 7 km (23,000 ft) deep and free of obscuring water or clouds it looks quite impressive. Rift valleys and structures suspected to be rift valleys have been found all over the solar system. Earth, Mars, Venus, Charon, Titania, Ariel, Oberon, Miranda, Tethys, and Luna have such structures.
While the martian Valles Marineris might be the best known and best looking example,
[](https://upload.wikimedia.org/wikipedia/commons/thumb/5/56/Mars_Valles_Marineris.jpeg/600px-Mars_Valles_Marineris.jpeg)
Ithaca Chasma on Thetys might be closest to what you want, as it is up to 100 km wide, 3 to 5 km deep and 2,000 km long and runs approximately three-quarters of the way around Tethys circumference.
[](https://upload.wikimedia.org/wikipedia/commons/7/74/Ithaca_Chasma.jpg)
I would also not disregard Eaths mid-ocean-ridges as they too are quite long.
## Contact Binary Asteroid-Moon
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> The concept of hydrostatic equilibrium has also become important in determining whether an astronomical object is a planet, dwarf planet, or small Solar System body. According to the definition of planet adopted by the International Astronomical Union in 2006, one defining characteristic of planets and dwarf planets is that they are objects that have sufficient gravity to overcome their rigidity and assume hydrostatic equilibrium. Such a body will normally have the differentiated interior and geology of a world (a planemo), though near-hydrostatic bodies such as the proto-planet 4 Vesta may also be differentiated. Sometimes the equilibrium shape is an oblate spheroid, as is the case with Earth. However, in the cases of moons in synchronous orbit, nearly unidirectional tidal forces create a scalene ellipsoid. Also, the dwarf planet Haumea is scalene due to its rapid rotation. It had been thought that icy objects with a diameter larger than roughly 400 km are usually in hydrostatic equilibrium, whereas those smaller than that are not. Icy objects need less mass for hydrostatic equilibrium than rocky objects. The smallest object that appears to have an equilibrium shape is the icy moon Mimas at 397 km, whereas the largest object known to have a non-equilibrium shape is the rocky asteroid Vesta at 525 km (573 × 557 × 446 km). However, Mimas is not actually in hydrostatic equilibrium for its current rotation. The smallest body confirmed to be in hydrostatic equilibrium is the dwarf planet Ceres, at 945 km, whereas the largest body known to not be in hydrostatic equilibrium is the icy moon Iapetus, at 1,470 km. Because the terrestrial planets and dwarf planets (and likewise the larger satellites, like the Moon and Io) have irregular surfaces, this definition has some flexibility, but a specific means of quantifying an object's shape by this standard has not yet been announced. Local irregularities may be consistent with global equilibrium. For example, the massive base of the tallest mountain on Earth, Mauna Kea, has deformed and depressed the level of the surrounding crust, so that the overall distribution of mass approaches equilibrium. The amount of leeway afforded the definition could affect the classification of the asteroid Vesta, which may have solidified while in hydrostatic equilibrium but was subsequently significantly deformed by large impacts (now 572.6 × 557.2 × 446.4 km). - From Wikipedia on [hydrostatic equilibrium](https://en.wikipedia.org/wiki/Hydrostatic_equilibrium)
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Essentially an object must have a certain mass so gravity can force it into a spherical form. Below this ill-defined limit odd geometries are possible. **If you look at the pictures of 2014 MU69 (Ultima Thule), 67P/Churyumov–Gerasimenko or 25143 Itokawa, for example, you'll see examples of contact binaries.** Two asteroids which meat each other and came so close that they touched. I imagine the upper plausible size limit for this would be to take 2 metallic asteroid like [16 Psyche](https://en.wikipedia.org/wiki/16_Psyche) with a diameter of roughly 200 km and slap them together. This would be a sizable moon which could be stable over geological timescales. The caveat would be that the gash won't be that much of an obstacle, one could probably jump across it with some effort. Why the gash is equatorial and not polar as it would be in the beginning could bee explained by later impacts.
[](https://pbs.twimg.com/media/Dv7nHrGW0AAa39P.jpg:large)
## Artifical
One can get quite creative with reasons why a civilization would create a huge equatorial gash on a moon. Reasons could include
* **Because they can** It is an art project or a demonstration of power.
* **Paraterraforming project** The gash was created by excavation or detonations and then domed over to crate a moon-spanning garden-paradise.
* **Traces of a military operation** Relativistic kill missiles, antimatter, gamma-ray lasers, star-powered particle beams, pick what you like to create a gash in a planet.
* **Mining** It was a strip-mine. Down I the gash you'll find the remnants of a circumplanetary mass driver. This train to space used to export gigatons of minerals daily to support the economy of a K2 civilization. Maybe they were building a Dyson Swarm or some other megastructure which required such a strip-mine. One would expect to find many mineshafts branching out fro the central canyon, which was build to conveniently access the deeper mine-shafts.
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## Space Weapons:
Several hundred years ago, a rogue warlord named Krizakr took his spacecraft to the moon and build a base to use as a staging post for running raids a nearby trading world.
Because Krizakr was highly paranoid, he placed several powerful laser satellites in an low equatorial orbit.
Several years later Krizakr's died in a conflict with the Space Protection Fleet and on his starship the coordinates of his base were discovered. The SPF send a small fleet to access the base. It was determined that the armed sattelites were too dangerous to be left active and able to fire upon approaching vessels. Unfortunately they possessed no maneuvering thrusters, and approaching them with personnel was deemed too dangerous until they were disarmed - who knew what booby traps the notorious warlord had installed?
Fortunately they had recovered the firing control codes from Krizakr's ship so the satellites were pointed towards the (uninhabited) moons surface, and fired until their stores of hydrogen fluoride were depleted. With the primary weapons depleted, the satellites were left orbiting the moon, and a buoy was deployed warning passing vessels not to approach the satellites.
If you want craters rather than a single gouge, replace the Chemical Lasers with some sort of bomb or missile.
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## Rift Fault when the moon was forming
On mars there is the Valles Marineris: ttps://en.wikipedia.org/wiki/Valles\_Marineris This is a canyon that is some 4000 km long, is plainly visible, and is roughly east-west. I'm no geologist and the wikipedia page goes a bit past my head, but it seems to have formed when the tectonics of Mars was a bit more active. I see no reason why this couldn't have happened on a moon somewhere.
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## Unexplained science
Something similar to whatever happened to Iapetus. If you don't need to explain it in detail, you can probably hand-wave it as a "mystery the scientists are still unsure about". A giant gash encircling a planet is something likely enough to be feasible and strange enough to puzzle scientists if there's only one of them in the solar system.
[Answer]
If your moon was captured by the planet, it could have been from further away in the orbit, even maybe a rogue (belonging to no stellar system) and had a lot of water that happened to be frozen because it's cold in space (like a comet).
Now when your moon gets too close to the star (either at your planet's orbit or before it was captured, passing nearer your home star, again, like a comet), all the water could have melted and/or evaporated.
Now it's up to you what happens to this water. If you want to say the rock is very porous and liquid water seeped into it and disappeared, that's cool. If you want to say it went up in gas, it probably requires more heat so the closer approach would be more likely, unless you prefer to say this happened before life developed on your planet and at that time the sun was stronger.
The point is, this ice would have acted like the glaciers did during the ice age forming [lochs and generally destroying the landscape](https://loch-awe.com/history/lochs-and-glaciers/). You could even say that this used to be the polar region of your moon and this was a polar cap, before it was captured by your planet and a dramatic tilt shift happened. Fast forward a couple thousands (or million) years and through [tidal forces](https://en.wikipedia.org/wiki/Tidal_locking) your moon ended up being locked to your planet with a spin that wouldn't let you suspect its now-equator was once its pole.
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[Question]
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Making a semi-realistic Kirby Alternate Universe (AU) here. Popstar's shape is a result of a member of this powerful race using secret magics to alter reality in this AU.
What would its day/night cycle look like? What would the shadows from the points look like? Would there be locations that never or rarely receive light?
In light of some hard thinking and looking at the comments, I've decided that the canon popstar is too anomalous. I've decided instead that it is a normal round planet with five enormous mountains, angled like so:
[Answer]
Such a shape cannot belong to a planet: a planet would be under hydrostatic equilibrium, thus it would be spherical or ellipsoidal.
That body is therefore an asteroid. (Fun trivia: the word asteroid comes from the Latin word aster/astra, meaning star, exactly the shape it has).
Its rotation will very likely be chaotic, and such would be also the night-day cycle. The star arms would project a shadow on the surface opposite to them with respect to the star, more or less like mountains and mountain ranges do on Earth at sunrise or sunset, see below example coming from [Mount Teide](https://teidebynight.com/en/blog/mount-teides-shadow/).
[](https://i.stack.imgur.com/0G1h6.jpg)
The long dark stripe that you see is the shadow of the mountain projected on the sea/clouds.
Though in your case there would likely be no atmosphere and the result would less dramatic, still a shadow would be cast.
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[Question]
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In a world where magic exists, a specific character can channel electricity in whatever way you might imagine. They are relatively immune to suffering physical injury even for high voltage or current. Their body is somehow a close-to-ideal conductor. Let's not worry about how that makes sense and just leave it as a prerequisite.
This character would have an intuitive understanding of current and voltage without ever having encountering the formal terms, I would imagine. They'd say a higher voltage "feels like x" and a higher current "feels like y."
The question is, how might they describe the sensational difference between these two measures? I haven't been able to pin down a fluid way an uneducated (not stupid, just literally lacking formal education) person who only has an intuitive understanding might put this into words.
EDIT: I am refraining from the obvious experiment of electrocuting myself. Believe me, I'd like to, however I have just enough sense to avoid that.
[Answer]
## TL;DR: Comparisons to temperature and pressure for voltage, comparison to movement of the body for current
Using the sensations of ordinary humans who have experienced electrocution seems like a poor idea, because that's the experience of someone having their sensory mechanisms slammed by something that overrides them. This guy clearly has a nervous system that isn't affected by electricity, because otherwise he would have stopped his own heart as a kid or something.
What words would you use to describe looking at a blank sheet of paper if your language was invented by blind aliens? And no one else around you could see?
The reason I brought that there's no one else who has the same perceptions he does, of having electricity flowing through his body without setting off every nerve it touches. And there's no words in the English language to describe the feeling of pure voltage or pure current flow.
We all have internal perceptions based on the sensations our sensory organs send us, but we can't compare our internal perceptions directly. We have to compare based on what we consider common sensations. For instance, unless you've installed a stylesheet for this website, the background is *white*. What's my internal perception of white? I don't know how to put it into words. Just look at the website.
So, what does this mean for your character? They'll have to come up with analogies to other senses to describe it. Voltage would be compared to pressure or temperature. If your character can directly perceive current (instead of just feeling the shifts in voltage) then they might compare it to feeling the motion of their body. (See: [proprioception](https://en.wikipedia.org/wiki/Proprioception))
[Answer]
The fundamental problem is your claim to immunity and close-to-ideal conductor. With this the feeling is nothing at all.
The reason why is for electricity to produce a sensation it has to do work. Work can only be done your character is less than ideal at conducting. Super conductors can let a current whip around inside them without any loss only because the current isn't doing any work. If you're willing to dial that back though there are some sensations that would make sense.
"A light buzz" would be a fitting description for AC current that cycles polarity 50-60 times a second (depends where you live).
"Warm" fits for DC current that keeps the same polarity.
"Itchy" fits for static electricity buildup. Here the current isn't moving through the character, charge is accumulating and could discharge the moment they touch something with a lesser charge or simply when the buildup is enough to overcome the air gap. That's how lightning works. And speaking of which...
"Like I got my picture taken" fits for taking a lightning strike. This is over to fast to feel anything but any damage you allow to happen.
[Answer]
Your guy would have to be cocooned in a skin-tight layer of "magic" that acts as a superconductor, with the interface acting as a perfect insulator. So the electricity doesn't actually go *through* him, only the magic does.
The two different effects required - decrease the impedance of the magic layer to allow more and more current to flow, and increase the impedance and permittivity of the interface to avoid current leaks and other side effects - can then be felt by the guy: the increase in voltage might be felt as a "tightening", the increase in conductivity maybe as a coolness.
If you want to know what current *really* feels like - for some, at least - at low voltages, a DC current is a burning, acidic sensation, while AC current is a buzzing under your skin. At higher voltages, AC current is like a hit from a whip or a strong slap, and will leave your muscles aching; despite several close calls, I never experienced high DC voltages. This all depends on where the current goes through the body though: for example, even a low AC current *through* the appropriate points in the neck and chest will likely kill you.
[Answer]
Conducting electricity through the human body is a little tricky but I'll try my best.
Electricity is essentially the movement of electrons through matter. Voltage and charge describe this movement, and are fundamentally different but related.
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> Voltage, in essence, is the difference in the amount of electrons between two specific points. So, a circuit with a full battery would have its full potential voltage, minus some resistance. This means that voltage is essentially the amount of energy that a power source has to do work, such as light a bulb or heat an object.
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> A current on the other hand is the actual movement of electrons. The more electrons that move through a medium, the higher the current. For example, imagine a contraption with two tanks hanging in the air connected by a pipe. Only one of these tanks are full, and the water flowing between these represents the current. However, in a human body this causes the contraction of muscles, which explains how people are blown away when electrocuted; all their muscles contract at the same time.
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I would imagine that voltage feels like a tingling sensation throughout your body caused by twitching muscles and fidgeting, while a current feels like a concerted push away from a certain direction, like Newton's 3rd law.
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[Question]
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
For certain reasons I decided to not set my story on Earth. However, the planet is meant to host an Earth-like biosphere (including humans, most of Earth's species (perhaps some that didn't evolve before)). Since I was working with another planet, I decided to make it as big as possible (hence the question). The lifeforms on said planet don't need to be exactly analogous to Earth (evolution could have taken different forms), but it does need to be able to support homo sapiens (with perhaps some biological adaptations to living under higher gravity (only as high as is feasible) and other differing conditions, but still the same basic makeup).
[Answer]
Surface gravity is directly proportional with the radius of the planet and inversely proportional with the density of the planet.
Now fire up LibreOffice Calc (or your favorite spreadsheet program), and play with the numbers. I suggest to put Earth's radius, surface area and surface gravity as 1 (because your are interested in relative values), but keep the Earth's density as 5.5 (because it has direct implications for the chemical composition of the planet etc.) Then figure out what increase in surface gravity you are prepared to tolerate (I suggest 20 to 25% tops) and what decrease in density you can justify while keeping enough iron to get a decent magnetic field and to preserve Earth-like biochemistry (I suggest not lower than 5). You will get something like this:
```
Radius Area Density Gravity
------ ---- ------- -------
Earth 1.00 1.00 5.50 1.00
Max gravity, lowest density 1.38 1.89 5.00 1.25
Max-ish gravity, lowest density 1.32 1.74 5.00 1.20
Moderate gravity, lowest density 1.21 1.46 5.00 1.10
```
This suggests that you can get a surface area 75 to 90% larger than Earth's without extremely strong effects on the biosphere, and a surface area 50% larger than Earth's with minimal effects on the biosphere.
[Answer]
We don't have a good measure for how much gravity a human being can sustain for a lifetime. We might well find that 1.1 g is too much. Or that we can easily adapt to 2g. We have a little better understanding of microgravity's effects on the human body, but almost none on long term higher gravity. Twice is probably too high, but anywhere from 1.1 to 1.5 is up to you. No one can tell you that it is wrong, because we just don't know.
All our studies of higher gravity are based on limited duration. Basically the length of the high acceleration trip. We can't maintain high acceleration for a long period of time (too energy intensive), so we don't know what the effects are.
Beyond that, bigger doesn't necessarily mean higher gravity. If the planet is less dense (for example, no iron core), it can have a higher volume/surface area and the same gravity. The formula is
$$g = \frac{Gm}{r^2}$$
The formula for mass is volume times density.
$$m = \frac{4\pi r^3}{3}\rho$$
Substituting, we get
$$g = \frac{4G\pi r\rho}{3}$$
Rearranging
$$r = \frac{3g}{4G\pi\rho}$$
$G$ and $\pi$ are constants. Now, let's rewrite this as a proportion.
$$\frac{r}{r\_E} = \frac{g{\rho}\_E}{g\_E\rho}$$
What this says is that the size of the radius in Earth radii is equal to the number of Earth gravities divided by the density in Earth densities. So taking out the proportions, we have
$$r = \frac{g}{\rho}$$
There are some limits to how low you can make the density. Jupiter is composed of things (e.g. hydrogen) that have a low density at Earth gravity. But because Jupiter is so massive, they are compressed to a much higher density.
[Mars' density](https://www.universetoday.com/36935/density-of-the-planets/) is a bit more than three quarters that of Earth. All the lower density planets in our solar system are gas giants. So you can probably get three quarters. Putting that back into our formula, we get
$$r = \frac{1.5}{.75} = 2$$
So about the most you can expect to get is a planet twice as large in radius as the Earth. This will also have four times the surface area and eight times the volume. And six times the mass.
It is possible that you can manage a lower density than Mars. I don't have a good way of evaluating it. If you find that you can, you can put that number back into the formula.
[Answer]
Steven Dole suggested in his book [Habitable Planets for Man](https://en.m.wikipedia.org/wiki/Habitable_Planets_for_Man) the following gravity, mass and radius ranges for planets still maintaining a magnetosphere, plate tectonics, and a nitrogen + oxygen atmosphere. All values will be given relative to Earth.
$$M = 0.4 - 2.35$$
$$R = 0.78 - 1.25$$
$$g = 0.68 - 1.5$$
Now you want a big planet, yet you do not specify what you mean with big... Thus I'll calculate several examples.
**Max Mass and Max Radius**
$$M = 2.35$$
$$R = 1.25$$
$$g = \frac{M}{R^2} = \frac{2.35}{1.25^2} = 1.5$$
$$A = 4\*\pi\*R^2 = 4\*\pi\*1.25^2 = 1.56$$
**Max Mass and Min Radius**
$$M = 2.35$$
$$R = 0.78$$
$$g = \frac{M}{R^2} = \frac{2.35}{0.78^2} = 0.25$$
$$A = 4\*\pi\*R^2 = 4\*\pi\*0.78^2 = 0.61$$
**Min Mass and Max Radius**
$$M = 0.4$$
$$R = 1.25$$
$$g = \frac{M}{R^2} = \frac{0.4}{1.25^2} = 0.25$$
$$A = 4\*\pi\*R^2 = 4\*\pi\*1.25^2 = 1.56$$
However, there is an issue I see concerning the Max\_Max case. It is called [atmospheric escape](https://en.m.wikipedia.org/wiki/Atmospheric_escape) and can ruin your day during planet formation. You can see that whether or not a gas will remain in the planet's atmosphere depends on the escape velocity given by
$$v\_{esc} = \sqrt{\frac{M}{R}}$$
and the [temperature of a planet](https://en.m.wikipedia.org/wiki/Planetary_equilibrium_temperature) is given by
$$T\_{eq} = T\_{star}\*(1-Ab) ^\frac{1}{4}\*\sqrt{\frac{R}{2a}}$$
$Ab = \text{albedo}$
$a = \text{distance}$
From this I get $v\_{esc}$ of 15.34 km/s for the Max\_Max scenario, which gets awfully close to the point where it retains helium and would turn into an ice or gas-giant.
[](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Solar_system_escape_velocity_vs_surface_temperature.svg/1280px-Solar_system_escape_velocity_vs_surface_temperature.svg.png)
Atmospheric escape is the make it or break it point in the end for the survival of an Earth-like biosphere. You need methane, ammonia and water to stay on the planet and you need helium and hydrogen to leave. Otherwise it is utterly impossible for an earth-like biosphere to be sustained.
Furthermore [this article](https://io9.gizmodo.com/what-a-habitable-planet-twice-the-size-of-earth-would-b-1476308959) is an interesting analysis of an Earth-analog twice the size of Earth. It really is worth the read.
[Answer]
**SHORT ANSWER:**
According to my rough calculations, a planet habitable for water based lifeforms vaguely similar to terrestrial life - not guaranteed to be habitable for humans or other lifeforms transported from Earth - could have a surface area a little more than 1.5 times that of Earth, which is rather disappointing. Some other answers also support that surface area limit through other calculations.
(added 07-26-19. But these calculations of upper limits are still rather uncertain and controversial.)
I believe that the habitablility of a planet of a given size depends a lot on its distances from its star and how much heat and light it gets from its star, so that larger planets would be more likely to be habitable farther out from their stars, and on various other factors.
Possibly an expert on planetary science and astrobiology could calculate and design an alien planet with a significantly larger surface area, with a larger percentage of ocean or dry land as you may prefer, and habitable for humans and other Earth life forms.
**LONG ANSWER:**
You might want to consider where you want your story to be on the MOHS Scale of Science Fiction Hardness.
<https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness>[1](https://tvtropes.org/pmwiki/pmwiki.php/Main/MohsScaleOfScienceFictionHardness)
The harder - more realistic and plausible - you want your science fiction story to be, the more the size of your planet will be constrained by various scientific factors.
Many old fashioned science fiction stories imagined that the giant planets in our Solar System and similar sized exoplanets could have solid surfaces and biospheres. Thus they depicted habitable planets with tens, hundreds, and thousands of times the surface area of Earth.
In E.E. Smith's *Lensman* series the heavy gravity planet Valeria is settled by Earth Humans and centuries or millennia later their descendants have adapted and are immensely strong. I forget what the surface gravity of Valeria was but it was probably far higher than humans could actually survive in.
As I remember from checking fairly recently, Stephen Dole's *Habitable Planets for Man* (1964, 2009) suggests that humans wouldn't want to colonize a planet with a surface gravity more than about 1.25 or 1.50 that of Earth. The surface gravity of Earth is abbreviated 1 g.
[Tolerable range of surface gravities for interplanetary colonists?](https://worldbuilding.stackexchange.com/questions/136269/tolerable-range-of-surface-gravities-for-interplanetary-colonists)[2](https://worldbuilding.stackexchange.com/questions/136269/tolerable-range-of-surface-gravities-for-interplanetary-colonists)
<https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf>[3](https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf)
A writer could get away with having a group of colonists or alien abductees settle on a planet with a surface gravity of 1.10 g, and then after generations of adaptation have a group of their descendants settle on a planet with a surface gravity of 1.21 g. By repeating this process over and over again over generations, centuries, and millennia, planets with surface gravities of 1.331 g, 1.4641 g, 1.61051 g, 1.771561 g, etc., can be settled until eventually some absolute upper limit is reached.
Or possibly genetic engineering could be used to modify Earth Humans to be able to survive, be healthy, and function on planets with higher gravity than Earth. If it is a fantasy story some type of magic could modify Earth Humans to live on the planet.
Or maybe the natives of that planet aren't Earth Humans but members of another species that look a lot like humans, except probably being shorter and stockier. And if there aren't any characters from Earth in the story the characters would mostly be described by how they appear to other members of their species and there might not be more than a few subtle clues as to how different from Earth Humans they are.
Another factor to consider is plate tectonics, which are considered to be a factor in making Earth habitable. Many smaller astronomical bodies in our Solar System don't have plate tectonics. So one would think that a planet larger than Earth wouldn't have any problems with insufficient plate tectonics.
But there is an article:
"Exomoon Habitability Constrained by Illumination and Tidal heating" by Rene Heller and Roy Barnes, Astrobiology, January 2013.
<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>[4](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/)
In section 2, Habitability of Exomoons, they discuss the mass range necessary for hypothetical exomoons to be habitable in the sixth paragraph:
>
> A minimum mass of an exomoon is required to drive a magnetic shield on a billion-year timescale (Ms≳0.1M⊕; Tachinami et al., 2011); to sustain a substantial, long-lived atmosphere (Ms≳0.12M⊕; Williams et al., 1997; Kaltenegger, 2000); and to drive tectonic activity (Ms≳0.23M⊕; Williams et al., 1997), which is necessary to maintain plate tectonics and to support the carbon-silicate cycle. Weak internal dynamos have been detected in Mercury and Ganymede (Gurnett et al., 1996; Kivelson et al., 1996), suggesting that satellite masses>0.25M⊕ will be adequate for considerations of exomoon habitability. This lower limit, however, is not a fixed number. Further sources of energy—such as radiogenic and tidal heating, and the effect of a moon's composition and structure—can alter the limit in either direction. An upper mass limit is given by the fact that increasing mass leads to high pressures in the planet's interior, which will increase the mantle viscosity and depress heat transfer throughout the mantle as well as in the core. Above a critical mass, the dynamo is strongly suppressed and becomes too weak to generate a magnetic field or sustain plate tectonics. This maximum mass can be placed around 2M⊕ (Gaidos et al., 2010; Noack and Breuer, 2011; Stamenković et al., 2011). Summing up these conditions, we expect approximately Earth-mass moons to be habitable, and these objects could be detectable with the newly started Hunt for Exomoons with Kepler (HEK) project (Kipping et al., 2012).
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The upper limit of about 2 times the mass of Earth should hold for exoplanets as well as exomoons.
Heller and Barnes give the source for the importance of plate tectonics for habitability as:
Williams D.M. Kasting J.F. Wade R.A. Habitable moons around extrasolar giant planets. Nature. 1997;385:234–236. [PubMed] [Google Scholar]
Heller and Barnes give the sources for an upper mass limit at about 2 Earth masses as:
Gaidos E. Conrad C.P. Manga M. Hernlund J. Thermodynamics limits on magnetodynamos in rocky exoplanets. Astrophys J. 2010;718:596–609. [Google Scholar]
Noack L. Breuer D. Plate tectonics on Earth-like planets [EPSC-DPS2011-890]. EPSC-DPS Joint Meeting 2011, European Planetary Science Congress and Division for Planetary Sciences of the American Astronomical Society; 2011. [Google Scholar]
Stamenković V. Breuer D. Spohn T. Thermal and transport properties of mantle rock at high pressure: applications to super-Earths. Icarus. 2011;216:572–596. [Google Scholar]
It is possible that the importance of plate tectonics for habitability, and the upper mass limit of about two times the mass of Earth for plate tectonics, are not accepted by all scientists interested in astrobiology, but I have not researched that.
Accepting for the moment that about two times the mass of Earth is an approximate upper limit for planetary plate tectonics and planetary habitability for native lifeforms, the diameter, and thus surface area, of a planet is not solely determined by its mass. The diameter and surface area of a planet is determined by its mass and its overall density.
The overall density of a planet is determined by two factors.
One factor is the normal density of the various elements, compounds, and mixtures that it is made of, averaged. The normal density of those materials is the same density that they have floating around in tiny meteoroids in outer space, or lying on the surface of planets.
The other factor is the degree to which those materials are compressed by vast pressures at various levels in the interior of the planet, thus becoming denser and increasing the overall density of the planet.
Since the cube root of two is approximately 1.25992, a planet with twice the mass of Earth and the same overall density would have about 1.25992 times the radius and diameter of Earth and about 1.5873 times the surface area. Note that in order to have the same overall density as Earth, a planet with twice the mass of Earth would have to have a different composition than Earth, affecting life on the surface in various ways.
Since the strength of gravity depends on the mass and the square of the distance, the surface gravity of a planet with twice the mass of Earth and 1.25992 times the radius would be about 2 divided by 1.5873984, or about 1.2599231 that of Earth.
By decreasing the overall density of your planet you can increase its surface area but there is no doubt a limit to how much you can do so while keeping the planet habitable, or even with a solid surface.
A rapidly rotating planet would be more likely to have an internal dynamo driving plate tectonics, and a rapidly rotating planet would be more oblate, having a somewhat larger surface area and lower gravity at the equator. Earth original rotation rate was slowed down by tidal interactions with the Moon. As far as I know there is a controversy whether a large moon, which would slow down the rotation rate of a planet, is necessary for a planet to be habitable.
<https://www.npr.org/2011/11/18/142512088/is-a-moon-necessary-for-a-planet-to-support-life>[5](https://www.npr.org/2011/11/18/142512088/is-a-moon-necessary-for-a-planet-to-support-life)
And if a writer needs a really vast world, they could set their story on an artificial habitat in space, that has a much greater surface area than any habitable planet, created by a very advanced civilization.
<https://en.wikipedia.org/wiki/Bigger_Than_Worlds>[6](https://en.wikipedia.org/wiki/Bigger_Than_Worlds)
<http://www.isfdb.org/cgi-bin/title.cgi?133302>[7](http://www.isfdb.org/cgi-bin/title.cgi?133302)
(Added 07-26-2019 arkenstein XII in his answer to this question:
[Conditions of a more ideal version of earth](https://worldbuilding.stackexchange.com/questions/151545/conditions-of-a-more-ideal-version-of-earth)[8](https://worldbuilding.stackexchange.com/questions/151545/conditions-of-a-more-ideal-version-of-earth)
suggests that a superhabitable planet might have a mass of about 2.5 times the mass of Earth, somewhat more than the upper mass limit suggested in my answer, and thus it would have somewhat more surface area than I suggested was the upper limit. I suppose that a supehabitable planet would be more habitable for lifeforms that originated there than for life forms transported from Earth. These kinds of limits are still rather controversial.)
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[Question]
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In our 3D world, it is basically impossible to evolve living wheels, or helicopter rotors, or anything similar because free rotation of an axle dictates that there is no fixed connection to the body of the creature or machine--thus, there is no way to route nerves, blood vessels, etc.
If you just want to rotate a compact object, though (not an axle or similar non-compact object that has significantly extent in one dimension beyond its attachment point), there are arrangements [like this](https://www.youtube.com/watch?v=JaIR-cWk_-o) that allow you to do so. Adding an additional spatial dimension would seem to provide a way to extend an axle out from the cube in the center of that assembly to transfer continuous rotation to a wheel or other continuously-rotating structure. However, as with [my previous question on 4D biomechanics](https://worldbuilding.stackexchange.com/questions/149230/body-plan-of-a-4d-human-analog), my capacity for higher-dimensional visualization kind of fails here, which makes it difficult for me to be sure that this would actually work, with an extended axle simultaneously being capable of transmitting the mechanical motion, and avoiding intersecting any of the support structures during a full 720-degree rotation.
So: Does having an extra spatial dimension to work with actually make it possible for creatures to grow freely-rotating wheels with fixed (although flexible) connections to the rest of the body, or does even a 4D wheel end up requiring a mechanically-isolated axle after all?
[Answer]
You asked for this, this is a lengthy subject and if you were to really go into detail you could write hundreds of pages about it. I've tried to keep it a bit short but that's impossible.
Bio-wheels can be done in 3D! There is just no evolutionary path there because of the simple question "how does it move while the wheel is still evolving".
I've actually designed a living wheel once when a biomechanics teacher said it couldnt happen. After I told him about the idea he amended it with the "no evolutionary path". The wheel worked like this:
Bloodflow does not have to be constant to keep an appandage alive. So when turning the bloodflow will be severely hindered. During arm surgery for example they often take the blood out and can operate 7 hours without permanent damage to the arm. Since this wheel appandage will be in use that time will be significantly shorter before damage is sustained, and without a blood reservoir in the wheel itself and a local heart-like pump any muscle-movement while the wheelnis in motion will last a maximum of 2 minutes, probably less. This problem can be circumvented by making the axle that the wheel spins on contain the bloodvessles, and having the blood flow down into a small open area surrounding the axle where fresh blood can be pumped through the wheel while de-oxynegated blood is collected in a funnel at the top and flows away. The turning of the wheel and constant muscle contractions can pump the blood around, thus is actually how de-oxynegated blood in your legs is pumped upwards during excercise.
Nerves is trickier. While there is no need for muscles on the wheel end (more later) it would be necessary to have nerves to feel injury to the wheel and changes in the ground it moves on. This can be solved through a ring that forms one giant synaptic gap. There would be thousands of these rings in a row, one for each nerve in the wheel. To reduce the amount of input needed it is likely the wheel will use the same self-thinking capabilities as octopus arms. The nerves travel through the axle of the wheel and will all connect to the synaptic gap. This is the hardest part as a synaptic gap is incredibly small and movement shouldnt interfere with this gap, but since we have functional synaptic gaps right now it should work. If the neurotransmitters cross the gap they are received at whatever spot was at that time turning passed the nerve, and then the signal is created and travels around the ring until it reaches the axons and dendrites of the actual nerve cell(s) it belongs to.
Then there's muscle movement, and that may actually be much simpler than it seems. Take a look at 
<https://images.app.goo.gl/QuokdPB9jnZsatds7>
You can see a schematic of how a muscle is build up. Each sarcomere is a round tube with an actin filament on the outside and a myosin filament on the inside that is suspended by a titin filament. You have one end facing left anf the other facing right, with the actin filaments apart from each other. When activated the myosin filament has tons of "arms" that grab the actin filament above it and pull it inwards, which causes a contraction as the left and right actin filaments are pushed closer to each other. The myosin "arms" also release when they cant push any further, move backwards to grab the actin filament and then push again. The muscle can only conteact until the left and right actin filaments touch each other, at which point the muscle is maximally contracted.
The thing is, what if you only had an actin filament attached to the wheel, and only half of the myosin filament attached to the body around the axle of the bio-wheel? Now instead of making many muscles with many filaments in tandum, you make it one continuous filament around the axle? Now the myosin will never be able to maximally contract the actin filament, and keep pulling it over itself as the wheel spins and spins. Another advantage is that since the muscle is on the body-end and not the wheel-end you can supply it with blood and nerve input (which would kind of make the octopus-like control redundant). Now add as many of these circular muscle rows as necessary around the axle to push it. Additionally by making the axle thicker and the wheel part a thinner edge around the axle you can increase the amount of muscle fiber per circle. It would also mean that the wheel part only has to be as thick as it's bone support needs to be limiting the amount of blood and nerves you have to connect to it.
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Maybe. But I'm having a lot of difficulty doing the visualization. Consider this video. <https://vimeo.com/62228139>
It shows a thing that has lots of names, in this case "Dirac's Belt Trick." The idea is that by twisting and looping, you can rotate something that is connected to a surrounding solid structure. The only thing is, you need to loop the connecting things all the way around the rotated thing. But nothing gets disconnected.
There's another version of this where you turn a cup around 720 degrees by passing it first under your arm then over. If you are careful you never lose any water.
The looping-round part is tough because, for example, if it was a wheel, you would wind up running over the connection every time you looped around. Not as convenient as one might hope.
Now the part I'm having difficulty visualizing is doing the rotation in 4-D. Maybe in 4-D you can loop it around so that it does not get run over every time.
So if you allow this looping thing, it's possible in 3-D, at the cost of flinging the connection around or under. Though as several others have pointed out, the evolutionary path is tough to imagine. In 4-D it *might* be possible to avoid that.
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I find it easiest to consider 4d options for a 3d world via the Flatland method: consider 3d options for a 2d world.
Fortunately a wheel can easily be considered in 2d. It is a circle, rotating in the tabletop-like plane of Flatland. You could supply your wheel with a cylindrical 3d axle coming up out of the plane of Flatland.
The 3d cylindrical axle can be considered a stack of infinitely many 2d circles. The issue is the final 2d circle which is the interface with the wheel and (necessarily!) is in the same Flatland plane as the wheel. The fact that the rest of the axle is extraplanar to the wheel does not help with the interface in the same plane.
If 2 things have a normal mechanical interacton, they must at least in part occupy the same dimensional plane. The problems encountered with that interaction are not made easier by the fact that parts of the objects occupy different dimensional planes.
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Having mulled this over for a while longer in my own head, and building on the reasoning in [Willk's answer](https://worldbuilding.stackexchange.com/questions/150173/sanity-check-4d-bio-wheels/150175#150175) and [Nicol Wollaston's answer](https://worldbuilding.stackexchange.com/questions/150173/sanity-check-4d-bio-wheels/150360#150360), I think I can now definitively say **"Yes! A joint being spun by a 3D arrangement of fixed muscle attachments can indeed drive a continuously-rotating shaft extending in a 4th dimension."**
We start by considering rotation in a plane. There is a single stationary point at the center of rotation. Adding a third dimension, we can extend this point into a stationary line, or axis. By itself, that line cannot transmit rotational motion; in order to generate torque, you must have an attachment point with some finite offset in a direction parallel to the plane of rotation--or, in other words, a driveshaft centered on the axis must have non-zero thickness.
Now, here's the key part: consider a *different* third dimension. If we are working in a 4D space, *either* of two dimensions perpendicular to the plane will work for extending a shaft. The two dimensions are indistinguishable, in that either of them can form a 3D subspace of the 4D world in combination with the plane of rotation, and either one can have lines extended from it parallel to that plane defining the radius of a driveshaft. In fact, in general, we could have an entire drive*sheet*, or an arbitrary number of driveshafts all intersecting and rigidly connected to the plane of rotation at the same place, but rotated at arbitrary angles between the orthogonal cardinal directions of whatever coordinate system we choose.
Now, we just have to determine whether or not such a driveshaft must necessarily intersect the belts/muscles/whatever that attach to the joint at some point during a full double-rotation. And in fact, we can show that it need not do so. First, note that the motion of the belts can be confined entirely to a 3D hyperplane--we know this because the belt mechanism works in 3D! All of the components will occupy some 4D depth, but only a finite 4D depth. The driveshaft must also have finite radius in all 3 dimensions perpendicular to its axis--this means that it will have some finite extent in the dimension used to defined the 3D hyperplane within which the belt arrangement operates. However, we can also arrange that, as each belt passes over alternating faces of the central cube (or hypersquare prism, hypercylinder, or whatever), it can be made to pass arbitrarily close to the surface of that joint. Now, we imagine the driveshaft attached to the center of the 3D hypersurface of the joint; supposing we have belts of thickness $t$, we can arrange that no part of a belt extends further from the surface of the joint than distance $t$ by building the entire mechanism compactly, so that the belts are always sliding in contact with the surface of the joint. If the driveshaft has a radius of $r$, then as long as the joint itself has a minimum radius of $t+r$, there is no way that the shaft can ever come into contact contact with the belts, let alone intersect their paths.
I strongly suspect that the reality of the situation is actually much looser than that, but that much I feel I can prove. In fact, it should be possible to attach a nearly-complete 2D drivesheet to the joint, with mere holes cut out to permit the passage of muscle belts. When viewing only the 3D hyperplane containing the muscle belts, the intersection of the drivesheet with that subspace would appear as a set of disconnected axle sections floating unsupported, with the belts passing through the gaps in between.
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Nice video Logan, I've never thought something like that was possible.
Now, please follow and check my thoughts as I am not very sure myself.
First of all, I think it is really not possible to use this construction in 3D, because any of the six bands sweeps around the whole cube, not leaving any space for shafts. Even the two bands ending at the top/bottom of the cube would end up wound around shafts. So this is probably not just some accidental ignorance of 3D evolution.
Rotation in any number of dimensions greater than one looks like swapping two of the dimensions cyclically. Things pointing to X will turn to Y, then -X, then -Y, then back to X. Remaining dimensions, if any, stay in the same relative position. So, in 2D, the whole thing changes directions; In 3D, there is an axis of rotation, whose direction stays fixed; In 4D, things rotate around a fixed *plane*.
We could think of the cube as an endpoint (or middle point) of a 4D "shaft" extending away from the 3D hyperplane shown in the video. This "shaft" rotates in XY plane and stays fixed in ZW. The construction with cube and bands works in 3D, so it can all happen in a single XYZ slice of the 4D space, oblivious to anything far away in the W direction (even though the cube and bands need some non-zero W thickness for sure). So, the "shaft" extending in W can have bearings, wheels, propellers, anything attached at other W positions, and these all will still spin in the XY plane!
Please keep in mind that this is no mathematical proof, there is a ton of things I could have missed. I can't really imagine things rotating around planes. I'm not quite sure about construction of 4D bearings, or how wheels would work on a 3D surface. On the other hand, this is just a demonstration example, a real 4D evolution would probably come up with more elaborate solutions using the same principle.
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This question is about the Cube Prison as seen in the 2012 film The Cabin in the Woods. My question is not about the film or its lore, but how the cube prison can be constructed. Specifically, how could such cubes connect and move?
For the purposes of this question, we can rely [on what is seen in this YouTube video](https://www.youtube.com/watch?v=zvcoqDme4oQ). To avoid confusion, we need some assumptions and requirements:
## Assumptions
* Containing the creatures is not an issue - any monsters or other-worldly creatures can be contained through an invisible force field, something injected into the cubes, or yada-yada... I don't care. *We're not worried about the strength of the cubes, just their function.*
* The space is isolated from any external issues (in the movie this takes place underground, where we can presume factors like humidity and temperature are controlled).
* Material costs, labor, energy usage, or other related requirements are moot (this facility is needed to prevent the destruction of humanity, so an "at any cost" attitude is taken). We can assume whatever government(s) or organization(s) building and maintaining this facility have an "at any cost" attitude and will use any and all funding or resources available.
* No magic, and no other-worldly help. This facility is constructed, controlled, and maintained by humans with our current technology.
* Construction may take time and be tedious. Again, we can throw a lot of people, time, and resources at it.
## Requirements
Most of the prison can be seen starting at [2:23 in the video](https://www.youtube.com/watch?v=zvcoqDme4oQ&t=143), for a brief 15 seconds. From this we can gather:
* Each cube has at least two visible/see-through walls
* Some - but not necessarily all - cubes can move both horizontally and vertically.
* Some - but not necessarily all - cubes can rotate or pivot.
* Cubes are identical in size - *but not necessarily in feature or function*.
* There will obviously be some type of structure, but we cannot see any visible bars, pulleys, in the main area of structure. Any such bars, pulleys, motors, etc are either on the exterior, or can exist in the floor/ceiling of the cubes themselves.
## The Question
Can such a system be constructed? If so, how might the cubes move, connect, and interact?
[Answer]
[Like M-Blocks](https://robohub.org/robots-m-blocks/).
In [this clip](https://www.youtube.com/watch?v=mOqjFa4RskA) you will see them performing extraordinary maneuvers twisting, jumping and walking. [This part](https://www.youtube.com/watch?v=mOqjFa4RskA&t=45) 45 seconds in shows them interacting nicely with each-other.
They use magnets to stick together, and computer controlled inertial flywheels sped up and slowed down to produce torque on the body of the cube.
Because of the constraints of having transparent sides (and a passenger), the control mechanisms would need to be in the edges and vertices of the cubes. It wouldn't be a very smooth ride though. Thus I suggest the addition of [linear motors](https://en.wikipedia.org/wiki/Linear_motor) on the corners of the cubes to "drag" them along each-other.
Power would be supplied to the stack using cascaded [inductive charging](https://en.wikipedia.org/wiki/Inductive_charging) from the floor below, the charge passing upwards block by block.
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I am wondering what kind of physical qualities (e.g. short, thick pillar-like legs) a creature such as this would need to support such an incredible size. The world that it evolves on is almost identical to Earth save for the surface, which is mostly covered in thick, giant, interlocking trees. The shell must be as it is in the image as it is an important plot device.
A reference to the creature in question, or at least a poor representation of it, is shown below.[](https://i.stack.imgur.com/Ww6ct.jpg)
This image is poorly edited and does not represent proper anatomical proportions. Namely, the legs, which should be much thicker and stockier. As well as the head and neck vertebrae.
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A larger body means dealing with all the caprices of *gravity*. This problem has been addressed in *the future is wild* series. The [toraton](https://non-aliencreatures.fandom.com/wiki/Toraton) is a descendent of the tortoise. Its legs are much thicker. They are set-up under the body, not on its sides. It can no longer retract into its shell, but the shell is still useful in supporting body and muscles.
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Lose or at least heavily reduce the shell, it would probably weight too much for an animal of that size and it wouldn't be needed for defense anyway, barring some truly fearsome predators.
I see you already made the legs more pillar-like, so no need to change anything there.
Sauropods in real life used a complex system of internal air pockets to reduce their weight, turtles don't have anything of that sort in their evolutionary line, so as a rule of thumb make the animal a bit less voluminous than a sauropod of similar size.
Huge guts for digesting huge quantities of plant matter are also essential, as at that size it will need to rely on quantity over quality to keep itself fed.
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There are two good ways to have animals become larger.
The first, is cooler temperatures. Animals tend to become bulkier with shorter limbs in order to conserve body heat, see: [Bergmann](https://en.wikipedia.org/wiki/Bergmann%27s_rule) & [Allen's](https://en.wikipedia.org/wiki/Allen%27s_rule) Rules. Bear in mind that cold-blooded organisms like tortoises may not be able to survive in colder conditions.
The second option, is higher concentrations of oxygen in the atmosphere. This is believed to have contributed to the evolution of [very large arthropods early in the phanerozoic](https://news.nationalgeographic.com/news/2011/08/110808-ancient-insects-bugs-giants-oxygen-animals-science/), as well as the appearance of [larger mammals in the Cenozoic](https://www.scientificamerican.com/article/big-mammals-evolved-thank/).
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If the shell can *slide*, then you have no problems. The shell supports the mass, and the legs are basically used to propel it: they are rams/paddles to push it forward or rotate it, rather than struts to support it.
Unfortunately, a big, cumbersome shell is the worst option for maneuvering on a tree-covered planet ...unless something is big enough that it can *push over trees*.
Oh hey, you know what stuff slides really well on?
Logs.
Stuff slides really well on logs. Trust me, I've been a lumberjack. Especially when it's wet, such as in a rainforest, wood is *super* slippery. Vegetation in general, in fact. Slippy, slippy, slippy.
We humans use logs for rails, and they're great, at least if the wood is long and straight, like rainforest trees.
Now, branches might get in the way, but a vegetarian behemoth that knocks over trees could both eat them out of the way, and snap them off with its bulk. They're not an obstacle, they're *lunch*.
Child-tortoises would be able to walk and forage just like regular tortoises, but past a certain size, they'd be unable ot fit between the trees. These adolescents would likely need to follow tracks laid by their larger elders, filled only with saplings and younger trees, until they can push over their own trees.
So "tortoise roads" would likely form in this way, long paths of younger trees that would be easier for these beasts to travel through the forest, forming loops that might take a lifetime, from their egg-laying-grounds and back.
These roads would become small smooth valleys across the land, attracting water and becoming slicker and easier to slide in. Younger tortoises might avoid them (bad to be stuck in a slippery gulley filled with water that you can't climb out of) and might take other paths through the undergrowth.
Backtracking will likely be harder for them the larger they grow, as it's easy enough to slide *down* from an uprooted tree's bole to the canopy, but harder to make your way back up against the direction of the branches and up over the root bole.
So if they get stuck in a circle of cliffs or trees too large for them to handle, they may become stuck, and possibly die, once they have eaten the foliage around them. Another reason to stick to the tortoise roads.
Similarly if they get bogged down, but again, felled trees will help them there, spreading out their weight. Trees are extra-slippery in the wet, too. downside is, there's little stable ground to push against with your feet to make yourself slide.
There's a reason for some at least to branch out from the tortoise roads, though. If a road has been stripped bare by previous tortoises, then the next one to come along will have to find another path, if its lucky finding some older but still not-too-overgrown road; otherwise perhaps finding a gap where one of the great old trees had fallen, clearing a new path.
Similarly if a road had become too swampy.
And similarly, I suspect, if two tortoises met. The one behind, having nothing to crush and little to eat, is likely to be making its way along the road rather more quickly than the one in the lead. But since they are large, it cannot simply walk past the leader. So, other than perhaps a brief stop to mate, they'd need to split off and find their own way.
A third tortoise, coming to this fork after the others have passed on, might prefer the new-trodden path as being more verdant; or the older path as safer and more reliable. I guess it'd depend on the personality of the tortoise.
Now, ideally the beast would have a far longer keel than is afforded by that shell, for more weight distribution when sliding. But the body can provide a lot of that. And ideally the front of the shell would be of a shape suited to pushing over trees. The forelegs could be good for digging, to weaken and rend the roots on the near side of the tree, the better to push it over.
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Of course, if the trees are truly ginormous and distantly spaced enough that even something this size can dance between them, then none of this might be an issue anyway.
Even then, the core answer ("the shell is a sled") still remains.
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If it doesn't need to be a turtle specifically, then it could be based on an actual large sauropod. To reduce weight, it may produce methane in its stomach and store it in its air-sacs like an organic, land-bound zeppelin. This would likely be enough to hold up a turtle-like carapace. This would work well, as sauropod limbs stopped at the sides of the body, and so the legs would not be in the way of any necessary rib-ends
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I'm imagining a scenario where there is a conflict between humans and intelligent octopuses. The humans' main mode of transport is the bicycle.
The octopuses decide to stage a night raid whereby they will steal the humans' bicycles and dispose of them at the bottom of the sea. The problem is that they must transport the bikes from land to the coast. Dragging these would make a noise so the octopus plan to ride the bikes.
**Question**
Assuming that the intelligent octopuses are of a size to reach the pedals and the handlebars, could an octopus actually ride a bicycle - even in theory? What aspects of biology could prevent it.
**Notes**
Assume that the octopuses can survive out of water for the time required. (real-life octopuses do sometimes travel short distances on land)
Assume that the octopuses have worked out a way to mount the bikes but they can't support their full body weight clear of the ground on their tentacles for any length of time - hence needing to use the saddle.
[Answer]
Octopuses are fairly strong for their size; so, being physically able to ride a bike should not be an obstacle. Practically speaking, probably not so much.
Even humans that have never ridden a bike before generally can not do it without falling over repeatedly and making a bunch of noise. So assuming bike riding is not a thing octopuses already teach their young, then a random night raid like this would fail hilariously.
To further complicate the matter, octopuses have decentralized motor control over their tentacles. This means that their brain can give a limb a general idea of what that limb should do, but then the tentacle decides how to do it. This would probably make activities that require each part of the octopus's body to work in tandem for things like riding a bike pretty difficult compared to an animal with a centralized control system.
[Answer]
I don't think there's anything to prevent an octopus from riding a bicycle with the possible exception of force exertion, I'm not sure that an octopus can get enough down force from it's tentacles to move the peddles. In short they may not be strong enough but otherwise they're biomechanically adaptable enough for the task.
As a note any octopus big enough and strong enough to ride a bicycle can probably *carry* it completely off the ground more easily than they can ride it.
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A small village of ice miners has popped up in the Northern Territory. They are a mix of southern workers who integrated with the native tribes. The group subsists on the meat of a single humpback whale per year. They worship the giant fish creatures as gods, and preform ritualistic sacrifice to justify the killing of a whale. How many people can survive off of a single whale? Some money is made from selling ice, but most of it goes into improving the tribe's houses and buying new supplies for the diggers.
[Answer]
My calculations are very rough. The average weight of a humpback whale is about 25-30 tons, according to Wikipedia.
I didn't manage to find any sources for this, but I've seen the estimates of whale bone being about 20% of its weight, leaving us with around 22 tons of muscles, internal organs and blubber. And if they do not eat anything but whale, they are going to need the icky stuff, maybe some of it even raw, to be supplied with vitamins and microelements.
Now the hardest part is estimating the calorie value of a whale. I didn't manage to find exact figures for a humpback. (Here is the data for other whale kinds: [Whale Meat in Nutrition](https://www.icrwhale.org/pdf/SC00751-67.pdf))
As you can see, it ranges from 110s for lean meat to 400-500 for blubber and some internal organs.
I would try averaging that to 190-200 kcal per 100 of 'average' whale product. That would give us about a kilo of edible whale meat and other icky stuff per person to keep them alive and active enough to hunt the next whale.
Dividing 22 tonnes per 365 days we get about 60 kilos of whale per day.
So, with all the allowances I've made at the every step of the calculation, it seems that an average whale would be able to feed 60 (possibly less, if I overestimated the mass of edible portions or average caloric value) people per year, if they are ready to eat it whole.
UPD: if you are basing them of indigenous Arctic people, most of their societies are busy looking for food all year round. They, most likely, won't rely on one risky hunt per year - they will gather berries and roots, even edible lichens, hunt for birds, seals and whatever land animals there are (white bears, different kinds of deer), fish almost constantly. If they live that way, you can adjust the estimate upwards for at least 2x.
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I am writing a dystopian future where I hope to make it possible that specific emotions can be taken in the form of pills or drug form; or, combined pills taken to form more complex feelings. Obviously there are certain chemicals associated with emotions such as serotonin and endorphins. But are there specific chemicals that could be used to create something very close to taking a drug and it giving you an overwhelming sense of sadness, jealousy or rage?
Are there hormones and chemicals specific enough for this, or would it have to be combined with some kind of visual aid to create context to then be able to feel sadness more, for instance? (Although this kid of defeats the point, as in my world these drug forms of emotion are meant to be taken by those incapable of creating it naturally themselves).
[Answer]
**This is a big area of research at the moment.** (I'll add some pointers to research as and when I'm online)
The answer is almost certainly yes but there is a long way to go. However it will rely on drugs that can be accurately targeted.
*EDIT - to clarify
If you could isolate the chemicals in a human brain and inject those same chemicals into the brain of another person, but precisely into the same brain structures then I assert that the second person would experience the same emotions. Once we know what all these chemicals are and where to send them then with sufficient (very advanced) technology, we could replicate the same.
We couldn't replicate the other person's thoughts - just the emotions.
This might require nano-machines (also currently being worked on) to make sure the drugs were accurately delivered.*
At present if someone takes an antidepressant or an amphetamine it floods the whole system and not just the brain (there may be some preferential uptake). There are centres in the brain (still not fully understood) which when stimulated by an electrode can cause changes in emotion.
It's complicated because a drug that causes excitation in one sort of synapse in one organ can suppress it in another.
Once the technology to precisely target small brain centres is achieved then your scenario is possible.
**Notes**
You didn't give a hard-science tag (thank goodness!) so I am relying on remembered facts from studies some time ago.
If someone paid me I could probably back my answer up with the relevant research but it would perhaps take hours. Maybe I'll find some pointers that I can add on here for you to read up on.
**Provisos**
1. Some emotions can be very close to each other in physiological terms - for example mild fear and excitement (both involve adrenaline). It may be necessary for the subject to prepare mentally or hypnotically to avoid a 'bad trip'. However there are different brain structures that could be stimulated in addition to merely giving adrenaline. The combination could distinguish between fear and excitement. So a complex targeted drug could work.
2. Pleasant emotions could be **very** addictive.
3. The pills may have undesirable long-term effects.
4. **Added** To get perfect results it might be necessary to tailor the proportions of drugs to each individual to get the right balance. This could be achieved by a DNA analysis together with a brief personality test.
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**List of references** (in progress) Note that typing these terms into YouTube will usually give a layperson's guide.
Cognitive and emotional influences in anterior cingulate cortex <http://www.georgebushmd.com/GBMD-Website/Research_&_Publications_files/Bush_2000_TICS_CingReview.pdf>
Vagal tone and the physiological regulation of emotion. [This refers to the Vagus Nerve] <https://www.ncbi.nlm.nih.gov/pubmed/7984159>
>
> How the Brain Processes Emotions
>
>
> *When it comes to emotions, it turns out that there are regions in the
> brain, specifically in the limbic system, that are associated with
> each of the 6 main emotions. Emotions are actually experiences that
> are associated with activation of certain regions in the brain.*
> <http://www.neurologytimes.com/blog/how-brain-processes-emotions>
>
>
>
The gut-brain connection <https://www.health.harvard.edu/diseases-and-conditions/the-gut-brain-connection>
Chemosignals Communicate Human Emotions
<https://journals.sagepub.com/doi/abs/10.1177/0956797612445317>
Biochemical Variables in the Study of Temperament <https://link.springer.com/chapter/10.1007/978-1-4899-0643-4_10>
[Answer]
Some psychiatric medication is used to change the *affect* of patients: anti-depressants diminish sadness, depressants diminish joy, anxyolitics reduce fear, anxiogenics increase fear, there are drugs that make aggressive and drugs that reduce aggression, and so on.
The problem with all of this is that every human brain is different, and that not everyone reacts to the same drug in the same way. Which is why there are so many different anti-depressants, for example, and why for some patients none of them work (or not in the expected way or not without adverse effects).
So while it is easily possible to create a drug that will induce a specific emotion in a single individual (given enough time to research that individual), it is impossible to create a drug that will have the same effect on everyone.
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Not really, since there's a mental component to feelings. Basically, you need something to be sad\*, jealous, or mad about to get the full emotional effects. If you've ever had allergy testing, you might actually have experienced something like this. When the tests are finished, the doctor gives you a shot of adrenaline <https://en.wikipedia.org/wiki/Adrenaline> to counteract any lingering effects. This of course is the same hormone evoked in "fight or flight" situations, so you experience the physical component of the emotional response, without there being anything to fight or run away from.
\*Though see depression and the use of antidepressants.
[Answer]
**I think there might be a way.**
As other answers have mentioned, emotional responses are pretty complicated things.
Some emotions are more readily induced or modulated than others, and the more complex the emotion the more complex the means of effecting it needs to be.
Some real-world foods can make you happier some of the time simply because they're high in carbs. High-carb foods reduce stress hormone release in the brain.
As has been mentioned already, getting very precise at this point seems to require access to the inside of the brain itself and being able to distinguish between and selectively modify specific regions in specific ways.
The solution depends on how techy you want your story to be. If you're both going for a super high tech/robotic setting and want accuracy, you could use nanobots that migrate to specific regions of the brain on their own over time, then receive signals of some form or other in order to provide the necessary response.
**ie:**
**acquire nanobots**
**nanobots migrate to their specified locations**
**nanobots recieve signal**
**appropriate nanobots release/trigger release of appropriate neurotransmitters**
This signal could come in various forms and could even be food if you figured out how to send specific messages to the various nanobots based on food consumed.
Maybe you could just find some set of neutral compounds that don't exist in food/other ingestables and have a different set of nanobots in the digestive tract that detect the presence of those and their relative proportions, interpret those proportions as a specific emotional response, then send the correct message to the nanobots in the brain.
Some kind of wireless mesh network between the nanobots might be able to simplify this whole system enormously, but I'm not sure how capable those wireless systems would actually be. **Range in particular would be an issue** between the stomach/intestines and the brain. This might be solvable with some kind of relay network across that distance.
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[Question]
[
I an making a medieval society that uses a wolf-like animal as steeds instead of horses (in case it helps to have a description, think of a wolf built like a deer) and I wanted to know if it could out-run a horse within a hundred meters of each other.
[Answer]
Realistically? No. Horses have skinny limbs for a reason... so there's less weight to move as their legs go back and forth, and really hefty muscles at the base of each. A horse will outrun the wolf, but their weaker limbs (limbs themselves, not the base) will make it hard to struggle if wolves surround them (as wolves generally try to do.)
Unless, of course, the horse is weak for some reason. (Already exerted, tired, old, young, etc.)
[Answer]
The wolf would lose in a sprint, but could chase it down over a marathon.
Horses have skinny legs and bodies designed for fast bursts. They need a lot of energy to keep going, and they get exhausted quickly.
By contrast, wolves are designed for stamina. They hunt down their prey in packs over long distance. As soon the prey gets tired, the wolves close the distance.
The horsemen would leave the wolf cavalry behind at first. But then the horses tire (especially when carrying a rider) while the wolves keep going for a lot longer.
[Answer]
You'll probably find that at the same size they're about the same speed.
The smaller animals have more acceleration, the larger ones more endurance. The good old square cube rules come into play again, being taller gives you more stride length, but also more mass, that makes you slower to accelerate.
The bigger problem is feeding them. Larger predators need larger prey, a pack of wolves the size of horses will need to bring down a couple of elephants a week to survive. The largest wolves currently are the Canadian timber wolves and they mostly hunt bison, they need to be larger as a result of the size of their prey but there are still limiting factors.
[Answer]
Lets see:
[A horse runs](https://sciencing.com/how-fast-does-horse-run-4683256.html) about 70km/h when super speed and 50km/h when 'normal' gallop
The wolf can run about 50-60 km/h according to google.
A wolf is about 1m high, that means it grow about 50-100% due to this question.
With simple math the wolf could run 75km/h to 120km/h. (unrealistic)
To calculate realistic the legs of the wolf need to get stronger, with that the legs are getting heavier as well as the whole body. The acceleration drops hard and the top speed too. I would estimate the wolf be faster as the horse, but definitely not above 100km/h
I hope this helps
[Answer]
Depends on the type of horse and the exact details of the wolf. Considering the average horse (according to a lightning search on Google) goes about 48km/h while certain rhino's can reach more than 55km/h I see no reason why a giant wolf couldnt do it.
[Answer]
Ligers have a carnivore body plan and at 10 feet long and 750lbs will stand in for your horse sized wolf. According to this liger enthusiast site, ligers can run 60 mph - twice as fast as a horse.
<http://www.ligerworld.com/speed-of-ligers.html>
>
> A liger is capable of gaining a speed momentum of around 50 to 60
> miles per hour. This 50 to 60 miles per hour speed for a a liger,
> allows it to be faster than lions and equally faster to the tigers.
> Furthermore; ligers with this speed are only at the second spot just
> behind the Cheetahs which are capable of speeding around 70 miles per
> hour. Dr. Bhagavan Antle is measuring the speed of ligers for many
> decades at its Animal Preserve (The Institute of Greatly Endangered
> and Rare Species T.I.G.E.R.S.). He has witnessed the speed of 60 miles
> per hour from a liger named as Sudan the liger and also an average of
> 50 miles per hour speed from his other ligers as well.
>
>
>
[](https://i.stack.imgur.com/nH22B.jpg)
But somehow I don't see big boy here keeping that kind of speed up for very long.
[Answer]
# Wolves can run down a horse
Wolves [hunt and kill caribou](https://www.youtube.com/watch?v=NdVIxS8tgYM) regularly. In that video, a single wolf chases down (and kills a caribou). A caribou's top speed is 60-80 km/h according to [Ultimate Ungulate](http://www.ultimateungulate.com/Artiodactyla/Rangifer_tarandus.html), a source I am partial to. [Guinness](http://www.guinnessworldrecords.com/world-records/fastest-speed-for-a-race-horse/) says the highest speed ever achieved by a racehorse is 70 km/h.
Therefore, if wolves are designed to chase down caribou, and caribou are roughly as fast as horses, it is reasonable for a wolf to chase down a horse.
If the wolf is 4 times larger, then that is even more reason for the wolf to win a footrace.
[Answer]
If you change the wolf's body a bit more then just his size ( with what I mean on his weight ) they could go faster over long distances but not necessarily in a short sprint.
It's your world so you can give them more stamina ( and lighter body weight, because as I understand no one said that you must make them muscular and ), increase time that they can run before they get hungry and make them more "puffy" then mad stone muscle. Something like if you tried to make a werewolf.
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[Question]
[
The world below is flat. However, there are no endless walls of ice or force or magic - Instead, each side of the octagon "wraps" to the other side.
That is, the North boundary wraps to the South boundary at the exact same point. The North-East to South-West, East to West, and South-East to North-West. There is also a featureless "infinitely" (For all reasonable purposes) tall tower at the cornerpoints, and occupies them all simultaneously.
These wraps function exactly as if you printed this on paper, cut it out, and wrapped one edge to its counterpart. This leads to some... *weird* navigation around the corners. If you were to walk around the tower, you would walk in three full circles (Measured by angle) before reaching your starting point. Otherwise, navigation is fairly straightforward. Going across the north/south wrap doesn't change your east/west position, etc.
Other information that may be relevant or helpful:
* The planet has two "Suns" - They are always directly across from each other, and rotate around the center of the world.
* The two "Suns" have a "Sun" face and a "Moon" face, which rotate in synch to provide a day/night cycle. Thus, the entirety of the world is at the same time of day. Assume that the day/night cycle functions otherwise like our terrestrial one.
* The central landmass is aproxamately 3600 miles wide by 4600 miles tall. Height of the world is thus aproxamately 10,000 miles. This puts the surface area of the world (And oceans) at around 82.8 million miles squared, a little over 42% of the Earth's surface. (If you want to get into the nitty gritty, each pixel on the map is 5mi per side)
* Gravity is a stable 1g at all points
* The world is truly "flat", and there are no map distortions like you would find on a spherical world.
[](https://i.stack.imgur.com/NMuYA.png)
Religion has imparted the knowledge that the world is the shape it is, and tells of the tower in the corner positions. Even so, some wish to *prove* that the world is this shape, beyond "blindly" accepting religious dogma.
**Using European dating and technology, when would humanity be able to prove this world shape?**
Things that are beyond the scope of this question:
* This world affecting technological development. Assume relevant technology and knowledge are *exactly* what they were historically.
* Magic or other factors that created the world. Assume there is no magic in the world for the purposes of answering this question.
* Changes that the world shape would have on weather, wildlife, geography, etc
* Time needed to prove the world shape. This question is focused solely on technology and knowledge needed to prove it, not how long it would take to accomplish.
---
A reference for movement across edges: Going North/South across Point 7 takes you to Point 7, North/East from Point 5 takes you to South/West Point 5, etc.
Walking along the coastline, starting at Point 5 heading East, you would go:
1. 5 to 4, then cross (West to East)
2. 4 to 1, then cross (SE to NW)
3. 1 to 2 (Along the "Inner" sea on the top left), then cross back (NW
to SE)
4. 2 to 6, then cross (SW to NE)
5. 6 to 3, then cross (E to W)
6. And then you would have a long hike from 3 back to 5 along that very
long NW/N coast line.
[](https://i.stack.imgur.com/8cHlG.png)
[Answer]
Your not-Europeans would know that the world was flat in antiquity. [The Greeks knew the Earth is round](https://en.wikipedia.org/wiki/Spherical_Earth#Hellenistic_world) ca. 500 BC; this may have originated with or at least around the time of Pythagoras. It's thought to have been based on observations of the stars: the Greeks knew certain stars hung out near the North Pole, but from different places they appear at different heights above the horizon. This is consistent with a spherical world, with the changes in elevation corresponding to changes in latitude.
Your astronomers, however, would know that the stars are identical no matter where they are. (They might or might not still move, depending on whether your flat world rotates; it doesn't make a difference here.) They would know that the sea blurs out into an unresolvable haze rather than a distinct horizon, and that distant objects are fully visible when resolved, rather than the uppermost parts being visible first. These are basic observations that could be pieced together with ancient astronomical and other techniques.
Without traveling to the edge or corners, it would be impossible to know about the boundary conditions there. In fact it would be impossible to know you've passed over one of the edges from measurement alone. (It would be clear if you circumnavigated the world, of course, or otherwise ran into known landmarks.) Only by traversing the corners would the full shape of the world become apparent. In this case a number of geometric methods, such as measuring angles or distances involved in walking around the tower, could reveal that shapes there don't work the way they do in "regular" space. Again, this is a measurement that many well-known ancient civilizations (the Greeks and Egyptians spring to mind) could have carried out.
The final puzzle would be in figuring out how the edges are actually mapped together. This might rely on circumnavigation. Essentially there are two "maps" to consider: the order of some set of landmarks as you travel in a circle around the tower, and the directions those landmarks are from the center of the plane. Figuring out the first is trivial, but the second probably requires some people to actually go and find out; I suspect any analytic method will give multiple possible solutions.
TL;DR: Mapping whichever part of the world you're in (the center or the rim) is doable with Bronze Age know-how. Reconciling the two maps will require actually going and finding points of reference, which depends on how easy they find sailing.
[Answer]
Magellan's fleet finished the first circumnavigation in 1522, after a three years trip. In the following centuries, the European powers send countless expeditions throughout the world, to discover and annex it, thus expanding and precising the map. Maps from the 16th and 17th century already show a round world, even if bits and pieces are still missing since nobody explored them yet.
The [oldest globe map](https://en.wikipedia.org/wiki/Erdapfel) to have survived to us dates from the 1490s, although it has many errors and the American continent is, of course, missing.
So, taking into account that technology develop the same way in your world, I'd say they could prove it as soon as their 16th century.
[Answer]
You know the geometry of your world when you can walk around a corner. You can infer it when you can tell you have walked across the edges, but you can't be sure of the geometry until you've done the corners.
>
> If you were to walk around the tower [at the corners], you would walk in three full circles (Measured by angle) before reaching your starting point.
>
>
>
Unless I'm misreading your text, this is wrong (or at least contradictory).
See the diagram below. You walk from 1 to 2, then 2 to 3, then 3 to 4 and finally 4 to 1. That's four interior angles of the Octagon ( $135^\text{o}$ each ).
So you walk about a path $4\times135^\text{o}=540^\text{o}$ or one and a half times a normal circle (or the interior).
Your idea seems to be that the corners all overlap (which would lead to your "three full circles" idea). But you also want east-west and north-south wrap around. If you try to do this then the corners cannot all be together.
Now because four corners are involved in each tower circumnavigation, you only need to circumnavigate at two corners (one of the East-West and and one of the North-South set).
So when you people can manage the two trips and *share their information* they can work out the geometry of your world.
How soon they can do this depend on factors outside the question :
* How well do people (governments) share information ?
* How detailed is their map making ?
* How large is the world and what means of transport do they have ?
* Are their obstacles in the way (rivers, seas, mountain,) or weather problems ?
* How reliable and fast is the spread of information ?
Note that navigational information would be considered potentially secret by governments.
This is all very detailed and there's no point in discussing it. But, e.g. the Vikings could have performed this navigation weather and distances allowing. If the corners are landlocked it can be done by anyone local. But how soon anyone can piece all the information together depends on the politics of your word as well as the technology.
[](https://i.stack.imgur.com/fSbho.jpg)
[Answer]
>
> Even so, some wish to prove that the world is this shape, beyond "blindly" accepting religious dogma.
>
>
>
Look at the planet's shadow on it's moon. The shape of the shadow tells you the shape of the planet.
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[Question]
[
Is it possible to genetically engineer transparent carapace to act as biological armor in marine organisms?
I know that deep sea animals may have transparent skin to hide themselves in the lightless depths, but I havent seen any examples (so far) of transparent carapace. If you can make skin and organs transparent, can you do it for bones too?
[Answer]
As pictures in @Dubukay's answer illustrate, it will be transparent enough to see internal organs. However, **you cannot get complete invisibility**, because there is a difference in the index of refraction between seawater and the animal's skin/shell.
Pure water has an index of refraction of 1.333. The refractive index of seawater varies with conditions, but is within the range of 1.329 and 1.368.
The carapace of arthropods/crustaceans is made of the protein chitin. The scales and skin of fish and marine mammals is made of the protein keratin. Both have refractive indices above 1.5:
>
> *Refractive index and dispersion of butterfly chitin and bird keratin measured by polarizing interference microscopy*
>
>
> Using Jamin-Lebedeff interference microscopy, we measured the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive index values of the glass scales of the butterfly Graphium sarpedon are, at wavelengths 400, 500 and 600 nm, 1.572, 1.552 and 1.541, and those of the feather barbules of the white goose Anas anas domestica are 1.569, 1.556 and 1.548, respectively.
>
>
> [abstract on PubMed](https://www.ncbi.nlm.nih.gov/pubmed/22109431)
>
>
>
The only way for one transparent material to completely "disappear" inside another is for the refractive indices to match. As you can see, this won't happen.
[Answer]
## Yes, absolutely!
Check out this little guy:
[](https://i.stack.imgur.com/VtX4O.jpg)
This is a **[copepod](https://en.wikipedia.org/wiki/Copepod)**. They live basically everywhere and are [one of the most numerous](http://www.marinespecies.org/copepoda/) animal groups in aquatic communities.
They also belong to the subphylum Crustacea, the same group of animals as the more charismatic crabs and lobsters of which you're probably thinking. Their carapace is quite strong, but still translucent and almost glasslike in places.
Other examples:
### The aptly named [ghost shrimp](https://en.wikipedia.org/wiki/Palaemonetes)
[](https://i.stack.imgur.com/KOy5F.jpg)
### A common marine [isopod](https://en.wikipedia.org/wiki/Isopoda)
[](https://i.stack.imgur.com/LtMTJ.jpg)
### Even some lobsters can have [translucent shells](https://www.theguardian.com/us-news/2017/sep/05/shock-lobster-ghostly-translucent-crustacean-caught-off-maine-coast):
[](https://i.stack.imgur.com/YmrJQ.jpg)
[Answer]
A carapace is typically chitin rather than bone. Some species of shrimp have completely transparent carapaces. hardness and transparency of the carapace are largely determined by the degree of mineralization. Ghost Shrimp have transparent carapaces, and the carapace of many crayfish is actually translucent.
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[Question]
[
In terms of real world science, if a necromancer was looking to raise long dead corpses for a magical horde, what region or climate or type of area would they be most likely to find bodies that were still most intact?
How long after a battle or mass death would the bodies be usable for warriors in various places?
[Answer]
# The desert
[](https://i.stack.imgur.com/54i6Z.jpg)
A pre-dynastic grave in Egpyt of the [Badarian](https://en.wikipedia.org/wiki/Badari_culture) period. This body (which was not purposefully mummified) is between 6400 and 6000 years old.
# The arctic...or somewhere cold
[](https://i.stack.imgur.com/kUnSO.jpg)
This is [Ötzi](https://en.wikipedia.org/wiki/%C3%96tzi) the ice man, found in 1991 in a melting glacier in ~~Austria~~ South Tyrol, Italy. He died between 5400 and 5100 years ago.
# Conclusion
You could find bodies 5000 years old or more with flesh still attached (if your necromancer is more into zombies than skeletons).
[Answer]
Leave out any time period and region that has head hunting or liked building pyramids of heads, even fresh corpses would be unusable.
Your best time would be Napoleonic era or similar with huge amounts of men dead with less disabling wounds. Earlier times perhaps those despatched by horse archers or similar.
Best of all would be one of the numerous armies that perished through dehydration, starvation, plague or all of the above.
Really you're looking for scenarios where the bodies aren't badly damaged. So an army that left a large amount of plague deaths would be ideal. And realitively fresh corpses either in terms of time or environment.
Serendipitously I believe several armies lost a lot of men to starvation, freezing or disease in history while passing over mountains which would make the corpses last longer both because of the cold and because they'd be harder for predators/scavengers to get at.
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[Question]
[
Many designs I've seen of mermaids include webbed fingers. This may be a useful feature for a creature that swims a lot, but I'm wondering if this trait could be a hinderance where complex tasks are concerned. This is especially the case when there is webbing between the thumb and index finger.
This begs the question: How would the presence of webbed fingers affect the kinds of tools that mermaids create?
(I'm assuming that these tools are being built on land, but if anyone has suggestions for tools that can be made underwater I'd like to hear it!)
[Answer]
**Assumption**: Merfolk possess human anatomy from their waist up with only minor differences, the most significant structural one for hands being webbing between fingers. If this is not the case, my answer is not valid.
# Merfolk Need to Get a Grip
Things like hand axes, cord drills, and so on don't actually require all that much hand dexterity to make and use. You can see the hand dexterity requirements for making early tools in this excellent YouTube channel called [Primitive Technology](https://www.youtube.com/channel/UCAL3JXZSzSm8AlZyD3nQdBA/videos). Basically, if you can hold a rock in one hand and make a fire, you can make a lot of things! (Which, in turn, helps you make other things!)
The issue here is a mermaid's grip. In humans, the flaps of muscle/skin between the index finger and thumb needs to stay small or else our grip is compromised: we simply don't have as much strength if we don't wrap our thumb around whatever we are holding! Go ahead and try this: grab a hammer, spoon, or other (blunt) tool, and have someone try to get it out of your hand while using different grips. You, me, and practically everyone else is stronger with the thumb wrapped around.
Mer-people, with a similar hand structure to humans but with a pesky flap, may therefore change how they grip tools. The tools themselves, however, would not dramatically change. There are a variety of ways to hold a tool that can accommodate a webbed hand, such as [the thumb running along the length of the tool](http://www.jayfisher.com/_borders/KnifeGripFilipino.jpg), rather [than around a handle](http://www.complete-strength-training.com/images/grip-strengthening-hammer-casts.jpg). This can make other kinds of grips, like [pistol grips](http://www.sword-play.net/Resources/FoilGrip2.gif), more popular or even required for mer-folk. As long as this flap is somewhat flexible, I suspect their hands won't be the main limitation on tools.
I suspect they may dispense with handles entirely, opting instead to make their tools easily fit in the palm of their hands, just like ancient hand axes.
# Underwater Tools
[Hand-Axes](https://en.wikipedia.org/wiki/Hand_axe) (of the ancient kind), [adzes](https://en.wikipedia.org/wiki/Adze), basalt/flint knives, mortar and pestle, [mills](https://en.wikipedia.org/wiki/Mill_(grinding)), things from [cement](http://indianapublicmedia.org/amomentofscience/pouring-foundations-water/), and baskets (especially from [baleen](https://en.wikipedia.org/wiki/Baleen)) are some of the examples of things you can make underwater without much trouble.
[Answer]
If it's a full flap(the skin starts on the tip of the toes), most likely they would use tools that can be gripped in a stabbing manner(Imagine holding a knife in a way that it points down instead of up). If it's not a full flap, then probably they'd just make grips that have an indentation where the flap is supposed to go and then you can literally just use any tool that a human with no flaps/small flaps would use. That would probably mean that their grips would be a little more pear shaped, to compensate for the uneven distribution of force that would come from not being able to press part of yout palm against the grip, but overall I don't think it would affect design or usage in a big way. Definitely the tools would be usable by humans.
Another option is making two-handed tools, and using one hand as the opposing force to the other, kind of like an oversized thumb.
[Answer]
When I was growing up I had a friend who, from a birth defect, had webbed fingers. It never stopped him from doing anything I did with about the same level of effort. I never saw him shoot a gun because his family wasnt part of the gun club circles, but I can't imagine him unable to do so.
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[Question]
[
Imagine a character with a healing ability similar to Wolverine or Deadpool (as in able to recover from most injuries in minutes). The ability is always "on," and works like a sped-up version of the normal healing process. The character also has an increased metabolism (has to eat more to help fuel the healing process). The character is transgender, specifically female to male.
* How would the character's healing ability impact attempts at gender transition?
* Would gender correction surgery be possible? Or would only certain aspects, like a mastectomy/hysterectomy be possible?
* Would hormone replacement therapy be possible? Would dosages have to be structured to compensate for the body's potential resistance to change?
[Answer]
Hormone replacement therapy works better in younger (pre-pubescent) bodies than in older ones. Since rapid healing is characteristic of younger bodies, I think there is an argument that aggressive hormone therapy would ramp up a body's expression of gender-typical shapes - for example vocal cords, size of breasts, fat ratios - all things that exist in both male and female bodies in different sizes or proportions.
So, a masectory combined with massive testosterone might convince the body to repair itself in a more male configuration.
You can read up on the way that the male and female genetalia are similar in early status of fetal development. Maybe some combination of the hormones with (perhaps hand-waving nanobots) might continue the body to accept the new structure of a penile implant as part of itself.
[Answer]
I have wondered how Wolverine's healing powers know how he should be set up. I have to think there is some sort of internal blueprint that his healing factors moves thing back to if there is any deviation. That is why he does not age. I think really something like this would also push out his adamantium skeleton in much the way that real bodies push out real shrapnel.
In any case - what if the goal blueprint could change? Suppose the target for his healing factor became a female version of himself - or maybe a very different female version. **He would heal his way to the different gender.** I am not sure how fast someone like Wolverine or Deadpool is supposed to be able to heal something like a severed limb but it would be more plausible for a change like this to take more than a few seconds. Additionally, increased mass has to come from somewhere - either cannibalized from elsewhere in the body or after a several hour long raid of the all-you-can-eat buffet.
Someone like this would not only be a healer but also a slow shape shifter.
[Answer]
Since You are after Comics characters I can tell you there's an episode where a female character (Black Widow, if memory assists) that wanted to get pregnant and her fast-healing was interfering badly recognizing the "abnormal condition". Solution was to take drugs suppressing the enhanced capabilities for the whole period.
In your specific case it strongly depends where and how these "rapid healing" super-power hooks to: if it hooks to genetic material then it would revert any changes made while it was "switched off"; OTOH if it "counters" any sudden change in anatomy it could "accept status quo" and even protect it.
To be clear, since this "rapid healing" does not exist in practice, you can shape it how it best serve your plot.
[Answer]
+1 to AngelPray comment. OTOH, if as specified it is just a sped up version of the ***normal*** healing process; then things like amputation and other surgical changes will still work, the doctors just need to work more quickly. Or gender change may be even easier to get done because the surgeon can make part of a change; wait a few minutes for it to heal, then take another step with no worry about disturbing previous steps. Imagine building a house of cards with cards that very slowly "heal" together (like injuries). We could build much faster if they glued themselves quickly, like using super-glue.
[Answer]
I think the concept is quite simple: Cut Deadpool's shlong off and it grows back.
So, I don't think that he could transition.
] |
[Question]
[
Imagine that you need to fill-up a 4D unit [hypercube](https://en.wikipedia.org/wiki/Hypercube) with 3D unit cubes of water.
At first, I thought you'd need an infinite amount, arguing that it would take an infinite number of stacked 2D squares to fill up a 3D cube.
But then, I realized that given that each square had zero height, an infinite number stacked on top of each other should still have zero volume. Essentially, one can't talk about the volume of a 2D object. Similar reasoning can be applied to argue that 3D matter cannot fill up 4D space, regardless of whether it is infinite or not. Is this reasoning sound?
---
Consider these hypothetical scenarios: suppose a unit cube of space, relative to Earth so that it 'moves along' with the planet... suppose, a unit cube of such a space submerged in the oceans opens up into a 4th space dimension. Assume that the surround universe is not immediately destroyed.
1. Can the water be pushed into the 4th dimension via say natural movement of the oceans? Why I'm asking this is because an object in 2D space cannot be pushed into 3D space by forces in the 2D space itself.
2. Suppose it can be pushed by 3D forces: will it start draining immediately? How fast would it drain?
Basically, I'm writing a story about a 4th spatial dimension interfering with everyday life, and trying to make it as logically coherent as I can.
[Answer]
# filling
Look at [space filling curves](https://en.wikipedia.org/wiki/Space-filling_curve). You can apply the same idea to filling a 4th dimension with a 3d ribbon.
You still need an infinite amount, though.
You might also consider how 3d matter exists in the 4d world. Just like sheets of paper (or even ink on a sheet of paper) in our 3d world is not *really* 2 dimensional but meerly extremely thin in the 3rd dimension, you can postulate that the 3d objects, in order to exist at all in the 4d realm, are actually paper thin in the 4th dimension rather than having zero extent.
# pushing
See [my answer to *interactions with higher dimensions*](https://worldbuilding.stackexchange.com/questions/10666/interactions-with-higher-dimensions/10834#10834) for details. Of note:
>
> you don't have to stand beside something at w=5 inches for example to push in the −w direction. The physics is not "closed" over the domain of the dimensions of the current arrangement of particles. **Effects can operate at right angles to the participants.** That is the general thing you see with cross products. Gyroscopes would produce torque in that direction, electromagnetic effects would have more right angles to reach out to.
>
>
>
[Answer]
**Disclaimer, none of this should be regarded as proof since it's all theory.**
# The 4th Dimension
The 4th dimension is by humans incomprehensible, the same way that the 3rd dimension is incomprehensible for a 2D entity and the 2nd dimension is incomprehensible for a 1D entity.
A 2D entity simply can't view its existence from a 3D perspective. Just like we are incapable of imagining viewing something from the 4th dimension, quite similarly how we cannot imagine a color outside our spectrum simply because it's outside of our perceived reality.
# Dimensions
A 1D object simply has one dimension, "forward" and "backward" along a line. (so to speak)
A 2D object has two dimensions, "forward", "backward" and "side-to-side".
A 3D object has the dimensions of a 2D object with an added "up" and "down",
In short, 1D has one axis, 2D has two and 3D has three.
[](https://i.stack.imgur.com/XOl8p.gif)
Now, some argue that the 4th dimension is "time" but that does not quite represent the entire picture.
We, as "3-dimensional" beings, comprehend the world and our universe as infinite 2D "projections" so to speak. In essence, we are viewing an infinite number of 2D planes. The same way a 2D being would observe their universe as an infinite number of "lines" of the first dimension. (this is not a 100% correct statement, but I hope you understand what I mean.)
So, A 4-dimensional being would be viewing their universe as an infinite number of 3-dimensional "projections". An "angle" or perspective we are simply unable to comprehend, the same way a 2D being is incapable of comprehending the angle a 3D being would observe it.
Thus, the 4th dimension would be an infinite number of 3D "instances" or projections. Now, some argue that this is what "time" means; "An infinite number of 3D projections over time". In other words, moving through a 3D space and through time.
However, for us to comprehend this fourth dimension, the fourth dimension needs to be presented in a "3D" format.
The interstellar movie had a pretty good take on this, as can be seen here:
[](https://i.stack.imgur.com/VtYsG.gif)
Essentially, the fourth dimension would be presented as infinite instances in 3 dimensions; "up, down, forward, backward, left, right", that we would be able to traverse.
**Note that these 3D "instances" should actually exist in the exact same place at the exact same time.**
But that would mean that we would perceive it as only one instance, the one we are currently in.
# In regards to OP's question:
If this theory is correct, your 4D cube of space would not "fill up" or suck water into it. It would probably merely be an infinite number of instances of the same water. (through time? maybe? nobody knows)
What this would mean that if the 4D "cube" was 1x1x1 meters in 3D size, the water inside it would be an infinite number of 1x1x1 meter instances of the same 3D water. In essence, an infinite number of the same 1 cubic meter of water.
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The thing is that you have to realize that there is no such thing as a 2d object. Even sheets of paper, no matter how thin, are 3d. Looking at it from a 3d perspective, we live in a 3d world and all objects in it are 3d. 1d and 2d are theoretical constructs that we use to incrementally understand our universe.
So then, when you start thinking of our universe in 4 dimensions, you realize that nothing in it would have zero length in that 4th dimension. Say you think of time as that fourth dimension. If an object had zero length in the fourth dimension, it would exist for 0 seconds, i.e. it would never exist. Ergo, no such object can exist, and it should not be hard to see how this would extend to any dimension (1st or 2nd or 3rd or 4th or ...).
Here is another thought experiment to help you think in terms of four dimensions - Our perception allows us to look "backwards" through that time axis, so we can "see" an object projecting back in time. I can see my car out in the parking lot, and I have a vivid memory of it when I was getting into it in my garage. But our perception does not allow us to look forward, so we do not see the extent forward of an object in that time axis, but that is ok as a backward look is sufficient for this experiment. Now, look at your computer; it's there. Then remember it at a time before, and realize that you are looking at a 4d object.
As far as filling a 4d hypercube with 3d cubes of water, realize that there is no such thing as 3d cubes of water. They are 4d, because they exist in a universe that has more than 3 dimensions. If your 4th dimension in your 4d hypercube is a real dimension that exists in the same universe as those 3d cubes of water, for example "time", then those "3d" cubes of water are going to have some sort or extent along that dimension in order for them to exist in that universe. Therefore you could extend their length or stack them, end to end, along that dimension and fill that hypercube.
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Your reasoning is sound. This is impossible, almost by definition of what a dimension (and multidimensionality) is.
1. There are an **infinite** amount of points (0-dimensional) on a given line (1-dimensional), as a point has no width.
2. There are **infinite** lines on a given plane (2-dimensional), as a line has no thickness and therefore doesn't quite "stack".
3. There are **infinite** planes in a space (3-dimensional), as a plane has no thickness and therefore doesn't quite "stack".
4. Logically, you can therefore fit an **infinite** amount of 3-dimensional objects in a 4-dimensional space (note that this logical consequence is consistent **regardless** of whether you consider the 4th dimension to be time, or something else).
>
> In order to fill an N-dimensional space, your object must have a defined "thickness" in all N dimensions.
>
> But an (N-1)-dimensional object inherently does not have a defined "thickness" in all N dimensions, since it only has N-1 defined dimensions.
>
>
> **If it did have N defined dimensions, then it would be an N-dimensional object**.
>
>
>
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As for your hypothetical scenario's, we simply cannot say. As it stands, we perceive the universe as having exactly as many dimensions that we ourselves consist of.
Every object with a different amount of dimensions (points, lines, planes, 8-dimensional space) are all just **abstract theoretical** constructs. We can reason about them, we can make representations of them, but we can never truly **see** one.
From a tangible point of view of an N-dimensional observer, non-N-dimensional objects are as abstract as concepts such as *love* or *awkwardness* or *cynicism*.
They are not tangible in any way, even though they can be **represented** by a related N-dimensional object e.g. we could construct a cylinder, and then point at its base and say that it's a circle. But we cannot create a circle by itself, without it being part of an N-dimensional representation.
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Hmm. Do you really need to "fill up" 4d space, or do you just want 4d objects?
If you just want 4d objects, that's easy. First note that you can create 2d objects from 1d objects. Behold the triangle
a rigid 2D object made from 3 1D objects. In 3D, we get the tetrahedron
a rigid 3D object made from 4 1D objects. We can even get to 4D this way. Behold the [5-cell](https://en.wikipedia.org/wiki/5-cell)
a rigid 4D object made from 5 1D objects.
So, you only need 5 1D objects to make a 4D object. If you insist on using 3D objects, there are other ways you glue them into rigid 4D objects. It won't *fill* 4D space, but it allow you to make rigid objects.
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I think you are right with the 2d analogy. Draw the vectors. How can a 3d object produce a vector force into a 4th dimension? You are right about the stack of squares too.
A bummer thing about the infinite number of third dimensions is that you (3d person) would not be able to see from one to the next unless you give light some special properties.
Other weird thing is that all infinite number of stack of squares are in the same place. There is no order to them. If you have infinite number of 3d dimensions and you leave yours, be sure to take your stuff with because you are never finding your original one again.
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My thought is this: all of the fundamental particles (electrons, quarks, and photons (NOT protons or neutrons)) are zero dimensional if you don't believe in string theory, and one dimensional if you do. This means that protons, neutrons, and atoms are all just collections of zero/one dimensional particles, relative to eachother in space. The only reason atoms are three dimensional is because these fundamental particles are only situated in, and moving in, three dimensions. If a force were applied to a three dimensional atom, in a direction perpendicular to the normal three, the fundamental particles would settle into positions in four dimensions. You would then have a four dimensional atom which could, with enough of them, fill a tank.
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A cube of arbitrary dimension that is higher than 3 can be 'filled' with 3-cubes (but not with 2-cubes or 1-cubes, no analogy with Peano and Hilbert). This is a so called 3-cube theorem proved in the forties by L.V. Keldysh and published in 1957. Find a place to read about it.
The article is hard to find and written in Russian, but see [this summary](https://math.stackexchange.com/questions/1692266/open-mapping-and-space-filling).
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Assuming a spinning space station shaped like a wheel. With the inhabitant living on the inside of the Wheel to get spin gravity. Something like the station discussed in this [post](https://worldbuilding.stackexchange.com/questions/49106/is-my-space-station-feasible).
The needed speed and radius to achieve a certain gravity can be calculated using this [page](http://www.artificial-gravity.com/sw/SpinCalc/).
How large would the radius have to be for the people living in the station to feel that the ground is flat. I'm thinking that there are two aspects that to the feeling of flat ness that can be discussed separately.
1. The ground looks reasonable flat
2. It feels like flat ground when walking on it
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## Looking flat
This will be a problem if there are long lines of sight - you will notice the ground sloping upwards even if it does so 10 km away. We can see ground sloping down and Earth's radius is over 6 Mm. The shorter the line of sight, smaller the radius can be without people noticing. Also, humans are used to ground sloping up due to hills, so I guess that as long as you restrict the line of sight to about 0.2r (so you see ground slope by at most 10 degrees), people will be (mostly) fine as far as sight goes. With somewhat claustrophobic design, this allows for a radius on the order of 100m. Also, in a station with a radius of approximately 200m and low ceiling, the floor would disappear behind the "horizon" of the ceiling close to the 40m line. Making the station 10 times larger would allow for view range of several hundred meters, which (judging by human depth perception limits) should be more than comfortable.
## Feeling flat
I guess humans lack the ability to feel a difference of less than 1 degree (or at least can ignore it). While standing still, the length of your feet would require a radius of about 15m. Walking would increase this to about 50m and spreading your arms would require about 100m radius. Running involves losing contact with the ground completely, so I expect the problem shifts to you needing to gain angular velocity as you accelerate. At full sprint humans reach up to 10m/s, meaning that if we wish to keep angular speeds below 1 degree/s we'd need a radius of about 600m.
## Physics
If you wish to simulate Earth-like gravity, physics is your enemy. You'd want little variance between the gravity at floor and head level - the difference is proportional to change in radius, so a 1% variation would require about 200m radius. Also, precession forces are significant above 2 RPM, requiring over 200m radius to maintain 1g.
## NASA research
According to the wiki, NASA research led to the conclusion, that radii over 500m (implying about 1 RPM) are comfortable for people.
## Good news
Humans adapt to almost anything non-lethal. Reducing gravity and forcing the brain to get used to some weirdness can easily push the required radius down. Visitors would hate it, but the locals would consider it natural. Other than that, a radius of 500m or more should be fine for most people.
## Sources
Wikipedia pages on artificial gravity, space habitats and a few related concepts.
(Yes, I know, wiki is a bad source but this is not academia so give me a break.)
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They are two very different things. Virtually any radius would *feel* flat when walking on, as long as the circle wasn't so small as to actually be noticeably circular underfoot.
Looking flat is a whole other issue altogether. On a clear day you can see maybe 20km - so you're going to need a circle big enough that a curve is not really visible at that sort of distance. If it's allowed to look a bit hilly (say 6 degrees slope up) then your circle will need a circumference 60 times that - 1200km, or a nearly 400km diameter circle.
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The problem of "flatness" is that a line, horizontal at eye level in point A, will inevitably hit the deck. So you will see the "ground" in front of you, and the brain will tell you that you have a steep hill ahead, climbing towards the "sky".
[](https://i.stack.imgur.com/sclJ0.png)
To avoid this, you must either:
* have a radius so great that even with good visibility, the "dip" towards the ground of the horizontal light ray is not perceivable. For this, not even the radius of the Earth is enough.
* reduce visibility. Assume that a dip of less than X% is not perceivable, then you can calculate the dip from the radius, and from there determine how much to restrict visibility; or, assuming a minimum required visibility, determine which radius will allow the dip to be below X% at that distance.
* **cheat**! It should be possible to dope the atmosphere with a combination of a denser, innocuous gas like [sulphur hexafluoride](https://en.wikipedia.org/wiki/Sulfur_hexafluoride) and water vapour. The purpose of this is to change the atmospheric refractivity index with altitude (i.e. distance from the ground) in such a way that a light ray traveling from "higher" to "lower" altitudes is refracted *upwards*. On Earth you can get this effect by heating the air nearer the ground, which causes light rays to bend upwards so that when looking at the distant ground, you actually see the sky, which the brain interprets as the road being "wet". The problem, of course, lies in having and maintaining a stable gradient; otherwise, you'll have a disturbing "heated air" shimmering effect in the distance.
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This doesn't answer all the points if the question.
I once tried to design a ring space station that would take one day to make a full rotation (1,1574 \* 10^-5 Hz) and where "gravity" (normal acceleration) would be constantly 9,81 m\*s^-2.
I gave up on keep going with the world building because the **radius** gave 1.854.992.492,543 m = 0,01239 AU.
I'm pretty sure that a straight line wouldn't be noticed. Half a degree would be 16.187.863,297 m long. That's more than Earth's diameter.
-Edit: I've recently watched a [video](https://www.youtube.com/watch?v=b3D7QlMVa5s) about artificial gravity and, as the angular speed would be 0,00069 rpm, there would be no canal sickness. Also, the Coriolis effect would be minimum.
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I had the idea to make an artificially constructed planet which is terrestrial, but has the diameter of Jupiter. Instead of being a solid sphere, it would be five spherical layers, with land on the outside and inside, connected with pillars and with holes to let sunlight through to deeper spheres.
My current design is to have each sphere resemble a complex polyhedron (I don't know which ones yet.), with the edges being spars of land that curve and the sides being the holes, and connected to the sphere above and below with pillars. Each spar and pillar would have crust, mantle and core layers, with the core made of unobtainium that was enchanted so that its structure would be stable no matter what (which means ignoring hydrostatic equilibrium). It would also alter gravity so that 'down' is in the direction of the nearest land, and project a magnetic field (though I'm not sure if that particular aspect needs to be handwaved like the others).
What I'm curious about is, assuming there's enough magic handwaving to make it possible for humans to live on most of the planet, what other factors would make life different there?
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* If the all the spars and columns are close enough to each other, I would expect an increase in flying and sailing creatures. And, if there is a biome made of massive vines or anything like that that could connect one spar to another, there would be an increase in climbing and swinging animals.
* Depending on the amount of open space between struts, the might be species that like to dive in and out, maybe some might race in and out really quickly, diving deep and the sailing out the other side for fun, hunting, etc, and you also might find flocks of slower moving migratory flying animals. People might domesticate some for racing or transportation.
* Depending on the tech level of the inhabitants, and the distance between struts, I could imagine some making structures that connect struts.
* You could have major spars and columns, and then smaller ones, and then smaller ones, on and on, like this:
[](https://i.stack.imgur.com/FiUFO.jpg)
That could allow for some greater connectivity. You could also have regions where some of the struts are missing or broken, if you wanted an ancient, partially falling apart feeling.
* Obviously, dark loving creatures would be deeper inside the planet, since that will be the darkest area.
* Day and night cycles could be odd, depending on how many struts there are obstructing light from the opposite side of the planet. For example, if you have only a few struts very far apart, then even when the sun is facing the other side of the planet, the far side (night side) might still be getting enough light that it never really gets dark.
* Instead of oceans, you might have some struts composed mostly of water, with only enough unobtainium to mantain their shape. Or, similarly, you could have struts made mostly cloud/gas with a bit of solid structure for shape. Maybe you could have gas mining colonies in those struts, depending on their size.
* You might have some "faces" of the lattices be made/filled of a sheet of translucent or transparent materials, such as cloud, gas or water, or maybe even plasma, lightning, lava or fire. That could give very exotic atmospheres to different areas:
[](https://i.stack.imgur.com/YlVMC.jpg)
* You could also have the 3D volume of some polyhedrons filled with water, gas, fire, lightning, etc., rather than just a 2D face
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So, you have a diameter of Jupiter. You'll need to make sure that you don't have anywhere near the mass of Jupiter. So let's assume the layers are sparse enough to avoid a soul-crushing gravity on the outermost surface.
I assume you want atmosphere to breathe? You're going to need airlocks to keep the air from all drifting to the lowest level over time. Or pumps to pump it back out. Either way, there's a big mechanical component (doors or pumps) that someone is going to be responsible for maintaining. Whoever is responsible for maintaining those systems is going to have a lot of power. I'm reminded of Mad Max Thunderdome... the real power is held by the guy who keeps the electricity going, regardless of any military or elections or whatnot. <https://www.youtube.com/watch?v=Hgq4w4dqKsU>
You will have people who think in terms of three dimensions more than people on Earth typically do. Ask any kid who likes to climb trees just how rarely adults look up... they'll tell you it's very rare. It's something you have to consciously maintain as you get older... we get used to living in a plane. If we truly have cities constantly overhead and under foot, there will be a good deal more consideration of that dimension.
You're probably going to have some prime real estate on the surface with a view of the sun, even if you have a good mirror system or sun lamps down below. The view of the stars cannot be really replicated.
Military tactics of taking and holding the staircases/elevators would be interesting... there are various "conquering the starship" bits of fiction that are relevant here. I don't know enough military sci-fi to really comment, but I suggest you explore it. One thing I will point you toward is the book "Wool" by Hugh Howey. The first book stands by itself, even though it is the first of a trilogy, and it is the first book that is really relevant here. It's all about life in a vertical column "silo". <https://en.wikipedia.org/wiki/Silo_(series)>
Depending upon how long it takes to get from the inside to the outside -- it might be stairs all the way, with no automation, making it a generational trip to migrate from bottom to top -- you may have folks who disbelieve in the world outside or who are terrified of open space. Likewise, if the mesh of the world has enough metal, radio transmissions through it may not be possible, leading to populaces that are very cut off from the rest of the world except at specific landline terminals... which might be controlled/filtered. We're back to those staircases potentially being very easy control points to keep a populace in check.
That's all that comes to mind right now. I may add more if comments yield interesting inspirations.
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## Most of the differences between this world and Earth stem from unequal daylight hours across the world.
Areas will consistently receive less light throughout the year as sunlight headed toward them is blocked by other segments of the planet. You will see cold patches, altered seasons, and a host of other changes because of these.
---
## Here's a list of what I can think of:
### Complex scenes in the sky at all times
Depending on how spread out your layers are, you may see the other parts of the planet, in detail, in broad daylight. This is the most obvious change, and it may affect developing cultures. (You could come up with a hundred possible local myths, such as spiders in the sky that spin webs of terrain, or how the sky "cracks" every day and is saved when a god (the moon) appears)
### Daily eclipses
Segments will constantly separate the landscape from the sun, most likely in a predictable way, and native life will get used to it. As a result, timekeeping systems may develop from this (instead of 24 hours per day, 15 eclipses per day - etc).
### "Poles" at the joints
Terrain where multiple segments connect will be in shadow for most of the day. Therefore, it may be similar to Earth's poles - colder due to less direct sunlight. This would be be extremely interesting, as it yields a plethora of effects:
* **Exploration difficulty**. Intelligent species seeking to move outward from the segments they inhabit will find that it gets increasingly colder the closer to the joints they move. Harsh temperatures, combined with mountainous terrain due to high gravity and "segment fusion", could even separate populations of people until they developed space faring technology.
* **Strange winds**. Warm(er) air from the centers of the segments will rise, moving toward the joints; cool(er) air from the segments/poles will move toward the centers of the segments. This may be an additional obstacle for travelers, and keep them at home. To add to this, gravity will pull the planet's atmosphere(s) inward, but centrifugal force will pull them outward, potentially causing more strange winds at the segments connecting spheres.
* **Biodiversity**. Intelligent species aren't the only ones affected by segment isolation! Most species will not be able to cross the segment divides, meaning evolution may look completely different all across the planet. Biodiversity is also fueled by surface volume - there's so much space to cover that you're bound to end up with variety.
### Coldest at the "true" poles and on the inside
Sunlight will be least direct at the "poles" of the whole structure - the top and bottom - so they will be the coldest regions. Additionally, the inside, while receiving more direct light than the poles, may see much of it obstructed by the surrounding shells - also making it slightly cooler. The converse of this is true - the outer shells will be warmest, and the equator(s) will be warm as well.
### Screwy satellites and unsafe orbits
If the majority of would-be impacts just pass through the lattice, and every segment is as thick as the Earth, some objects may orbit specific segments. You may see regions with their own local moons, whose orbits don't stray into other regions. Additionally, comets, asteroids, and other bodies may fling themselves in and out of the planet, or in a complex orbit inside the spheres. Imagine how culture could change as a result of so many objects to see! Consider also that some of these may be their own (spherical planets) within the main one.
### A true core
This planet's center of gravity will likely be close to the center of all of the concentric spheres. Some bodies passing in and out of the planet may even lose momentum and settle in this region! Consider a planet or two, or at the very least a gas cloud, to put in this area.
### Rich culture overall
This setup has produced regionally divided groups of people, huge biodiversity, potentially large temperature gradients with such a large sphere, and a ton of astronomical phenomena to influence mythology, timekeeping, and more.
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## Moving Parts
These are very "outside of the box" ideas, not what you mentioned in your description, but if you are interested in exploring variations on lattice worlds, they might give you some ideas you like:
## Rotating/Flexing Columns and Spars
This idea was inspired by some [mathematical artwork](http://www.bugman123.com/Math/index.html) an old friend of mine, Paul Nylander, made. He was very interested in exploring polyhedral structures, and many of them flexed and rotated:
[](https://i.stack.imgur.com/213VS.gif)
[Here is a higher resolution version](https://youtu.be/I8Xv3j1oAyM), so you can see all the details.
## Rotating Layers
The different spherical layers could rotate, perhaps in synch with each other or not. You could remove the columns, or have them be loosely attached to each sphere, perhaps utilizing a non-solid, yet connecting joint, such as a repelling magnetic connection. Or, perhaps the columns could be on solid tracks.
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Below is an image of the French Empire in 1812:
[](https://i.stack.imgur.com/ZwxP4.jpg)
Circled in red are France and its allies before Napoleon's doomed-to-fail campaign on Russia. Outlined in blue is the Confederation of the Rhine. In dark purple is France in 1804 and in light purple are its acquisitions post-1804. Finally, in dark blue are the states dependent on France. This was a huge empire, one of the largest ever seen in Europe. But sadly, Napoleon foolishly attacked Russia in the winter, losing over half of his army in the process.
What is the smallest change I can realistically make in history to prevent this empire from falling?
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# Have France accept the [Frankfurt proposals](https://en.wikipedia.org/wiki/Frankfurt_proposals).
In 1813, [Klemens von Metternich](https://en.wikipedia.org/wiki/Klemens_von_Metternich), Austria's Foreign Minister and one of the most powerful conservatives (read: pro-monarchy, anti-Napoleon) in Europe, offered Napoleon the Frankfurt proposals. Under them, France would relinquish
* Spain
* Poland
* The Netherlands
* Italy
* Germany
However, it would keep its "natural frontiers":
* Modern-day France
* Belgium
* Savoy
* The Rhineland
Napoleon declined because he thought his victory was assured. However, he underestimated the strength of the coalition against him. The conservatives of Europe (see above) wanted to maintain a balance of power among the top nations (chiefly Russia, Prussia, Austria, and Britain), which would be shown again in the [Congress of Vienna](https://en.wikipedia.org/wiki/Congress_of_Vienna). A powerful France did not fit into that picture, and so they would do whatever it took to stop Napoleon. They had enough force on their side to do it, too. And if it didn't happen in 1814, it would happen later, because *none* of the major powers would be willing to align with France for anything.
At that point, it was France vs. the rest of Europe. France lost. But it could have salvaged the war. And yes, it could regain its power with time, even if it accepts the proposals. It just has to wait for Europe to become unstable again.
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**Make the U.K., Russia and the Ottoman Empires offers that they can't refuse.**
Rather than making war with Russia and tempting war on other fronts, make deals with them that make them happy.
Secure their support with trade deals that are unfairly favorable to them. Offer to take their prisoners and dissidents. Offer to squelch activists in the empire who dislike them. Offer to build rail lines that connect their capitols to your empire at your expense. Trade them your colonies abroad for their cooperation.
Imagine how the world would have changed if the Louisiana Purchase had sold French North America in the Mississippi basin at a discount to the Ottoman Turks or the Russians or Portugal, instead of the Americans.
**Carefully manage local elites**
Co-opt existing business leaders and aristocrats in a manner that allows them a bit of control of the dramatic rate of change brought about by joining your empire and assures them a prominent place in it. Meanwhile, put local elites who refuse to be co-opted in fear for their lives.
**Secure the full blessing of the Church**
Do what it takes to get the Church on your side.
**Consolidate your military position**
Rather than further expanding, expand the French mass army (one of the first in history) to other countries, raising citizen armies and training them in every country. Then deploy them in each case far from home where they will have no local allegiances. Resupply your troops during the lull with weapons and logistic supplies.
**Devote resources to propaganda**
Hire pitch men and artists and playwrights and musicians to tell the story of the miraculous enlightenment of your empire for everyone to hear everywhere all of the time.
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I have a world that has unexpected lifeforms detected. There are to-be-revealed reasons for it, but the way the ecosystem is set up is:
* Microbial life is abundant everywhere
* There is a single species of plant form that has colonized the land
* There is a single avian species that feeds on those plants
The rest of the life exists in the oceans, in which significant biodiversity exists. I am willing to change things slightly so that, for example, near the shorelines there is more land-based biodiversity if the planet itself seems completely unrealistic.
What would the consequences be of such an ecosystem? At the very least it would be extremely susceptible to microbial disease, since it's basically a planet-wide monoculture. What rules would have to exist on that life to work? I can imagine that the life should only exist at a certain latitude range, but is there anything else?
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This would be highly unstable.
You already mentioned susceptibility to disease but there are many other things such as drought, flooding, etc where variety leads to survival.
The main thing though is that your two single species would immediately start to specialize. Some plants would be in wetter or dryer or warmer or colder areas, they would adapt to those environments. Some birds would become heavier and take to the ground, others would fly further. Some birds would become predators, others prey.
It would take time, thousands, even millions of years, but the process would begin immediately as the original forms exploded out to fill every available niche in the biosphere.
For the short time it did match then yes, you are right. The plants would be limited to a certain terrain and conditions. Salinity, Ph level, sunlight, temperature. Can they survive frost? The birds would then only live where they could feed on the plants.
The birds would either need to store food/hibernate/migrate over winter or the plants would need to be active year-round.
With the lack of predators the bird population would tend to explode until they ate all the plants. The plant population would then collapse, the birds would starve to death, and the plants would regrow. This population boom-bust cycle would repeat every few generations.
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**Spoilers ahead for the *Ender's Game* series of books**
One good model for the kind of non-diverse ecosystem that you are looking for is the planet *Lusitania* from Orson Scott Card's "Speaker for the Dead" (and further detailed in the subsequent novels).
>
> On this planet there is an intelligent virus called the
> [*Descolada*](http://enderverse.wikia.com/wiki/Descolada) whose primary goal was to create a suitable
> ecological habitat for an alien race that meant to colonize it. The
> mechanism it utilized basically destroyed the DNA of most organisms,
> guiding the evolution of all life on the planet. This took a healthy,
> diverse ecosystem and over thousands of years whittled it down to a
> handful of planet-wide species.
>
> The ecology of the planet was thus forcefully placed into a rigid
> symbiotic lifecycle. Species spent their lives in stages. One such
> started out as bipedal mammals that spent their lives among trees.
> Once they were deemed mature, they were "planted" and became trees
> themselves. Those trees gave genetic rise to new mammals. Or
> bison-like creatures that have the grass they graze on in their
> life-cylce.
>
> The stability of the system was enforced by killing outside infuences
> (the planet was deadly for humans).
>
>
>
Without going any more into details, the main point I'm trying to make is that if you want a very low-diversity ecosystem, you may need to come up with some outside force shaping the genetic outcomes of the planet (solar radiation? I dunno).
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Earth has only one dominant species of animal life, including the oceans. You can have a look at the various environmental disasters and just scale them down a bit if your world's life doesn't also rule the oceans.
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## How to get humans that can change their skin color?
Approximately 1.6 million years ago, hominids lost their hair and gained dark skin (so says the [New York Times](http://www.nytimes.com/2003/08/19/science/why-humans-and-their-fur-parted-ways.html)). Evidence shows several several population [bottlenecks](http://mbe.oxfordjournals.org/content/17/1/2.full) where the number of hominids dropped to less than 100,000. Every population bottleneck is an opportunity for radical and broad transformation in any population.
Let's assume that in one of these early bottlenecks, a very large ground-bound avian predator (think [terror bird](http://blogs.pjstar.com/mindingbiz/files/2013/09/terrorbird.jpg)) was introduced that preyed on early hominids, drastically reducing the hominid population. Since avians almost always hunt by sight, it's advantageous for humans to camouflage themselves. During this bottleneck, a mutation appears that permits a group of hominids to mottle their skin color to match the background much like [octopuses](https://www.youtube.com/watch?v=eS-USrwuUfA) (video). While the ability is primitive at first, it conveys sufficient survivability that chromatophores spread to all hominids.
The giant avian predators disappear (extinction from whatever cause) but the color change capability remains in hominids. Sexual selection takes over and those with the prettiest and/or most extensive color range mate more often ensuring that chromatophores stay in the population while also increasing in complexity and color range. Assume that after the giant killer birds go away, that the evolutionary path to get to modern humans resumes.
Now granted, the communication methods of these early hominids will be very different compared to how this all happened on Earth.
Is this a reasonable series of events to explain humans with color changing abilities? Have I missed something?
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Cephalopods [change their colors](http://ocean.si.edu/ocean-news/how-octopuses-and-squids-change-color) using [chromatophores](https://en.wikipedia.org/wiki/Chromatophore). Mammals on the other hand (along with birds) use [melanocytes](https://en.wikipedia.org/wiki/Melanocyte). Chromatophores can do the crazy coloration techniques you are looking for, melanocytes cannot; or, at least they have not.
Cephalopods have [chromatophore organs](http://tolweb.org/accessory/Cephalopod_Chromatophore?acc_id=2038) to control their complex color changing patterns. This is a pretty complex piece of evolutionary machinery. I don't know if there is a definite answer on 'rate' of evolution, but this seems too complex to evolve ex nihilo on a scale of hundreds of thousands of years.
Chameleons and other vertebrates which have color changing abilities. They do not have chromatophore organs but instead have use [cell signaling](http://www.thenakedscientists.com/HTML/questions/question/2634/) to tell each chromatophore cell what colors to make. This is a less complex system, but it is also slower and, more importantly, it is evidently used in chameleons more for temperature management and signalling (as in, mating) than for camouflage. So while this system is easier to evolve, it would be less useful to your people for hiding from killer pterosaurs.
One last problem. How hairy were people back then? If you are putting chromatophores onto, say, a chimpanzee, they aren't going to do much good since there is fur in the way. That is why it is the mammals and birds that lost the vibrant colors: most of their skin can't be seen anyways.
In conclusion: Humans already have a different cell for skin pigment, one that cannot change colors (except as slowly as getting a tan), so the evolutionary advantage of developing chromatophores would be low until a fully developed system of color changing developed. Given that such a system in squids is very complex, and that a less complex system in chameleons is only marginally effective, the evolution of chromatophores seems unlikely.
A more likely response to avian sight-hunting predators is to become nocturnal or stay in forests.
So if you really want color changing humans you need a. humans that evolved from squid, b. humans that evolved from chameleons, c. mammals never lost chromatophores and most mammals (or at least primates) are hairless and have brilliant colors like tropical fish or d. magic.
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Avian predators are not that fascinating and can be killed easily by humans, it requires humans to be always in groups of 3 while moving, with spears, tomahawks, and so on. predators that put evolutionary pressure on humans from hunting havn't been seen, except for the fastest pack animals, wolves, lions, who use mostly scent, in fact all mammals have scent disadvantage.
Animals that hunt in packs, (which would be fascinating) would be a cross between a locusts and bees, and swarming crows. Note that there are no flocks of eagles, because there could be, except that they could empty the entire ecosystem and flocking eagles would be so effective that they would starve themselves.
A equally scientifically likely cause of a color change mutation would be sexual attractiveness, communication, and active hunting ability...
There are different types of metachrosis, spiders even have it sometimes from to adapt to plant colors.
The most cool is the chameleon. It has crystals similar to your nails and hair, contained in soft tissue, which can expand and contract and change density, probably platelets or grains of some kind, and depending on the squeeze, they can reflect light like an LCD crystal or petrol, in fact it's the same as a blue/green/red insect, which all have platelets in their shell which gives a metal reflection.
Chameleons and insects can only do bright colors with protein horn material which is arranged in platelets similar in size to light wavelengths, check TEMicro pics for it... they have expanding melanin organules/cells, black to change them black. images here - <https://www.google.fr/search?espv=2&biw=1195&bih=723&tbm=isch&sa=1&q=color+chitine+microscope&oq=color+chitine+microscope&gs_l=img.3...2510.4451.0.4700.13.10.0.0.0.0.332.809.1j1j1j1.4.0....0...1c.1.64.img..10.2.357...0i7i30k1.k9QQZn_J9tc>
human eye color changes help humans to indicate the direction of prey and to communicate pathways or dangers without talking, and makes it easier for humans to communicate in groups as it avoids danger within a group. communication seems like a more likey cause for a color change.
Humans with color change would be very communicative about mood and for hunting indications and dangers. long distance communication without waving hands about.
So a human with color change would learn to talk, left right, now, later, etc with colors.
The microbiology is difficult. if humans could do like squids they would have seaslug mucus skin because it would be so flexible and spongey. squids have muscle pores containing red,yellow, black white colors. you could say that they at first developed hair which had iridescent colors, like birds, or even feathers, and learnt to communicate by making color patterns with feathers or by turning their hair like petrol reflections or lcd cells and opals... that's oddly enough one of hte few physical pathways for that trait.
So you haev to figure out a way for humans to show and hide freckles with hair or with other freckles that slide over the first freckles. the most likely way is for humans to develop chameleon skin, so essentially their freckles would become highly developed platelets and humans would have actual muscle or electricl signals going to their skin to make colors by changing platelets or freckles density/postion/rotation.
mammals don't have bright colors, birds do, which is an illustration of the unlikelihood of it happening in mammals, even 60mn years of mouse generations didnt make red/blue/green mice.
Evolutionary pressure by improved communication rather than simple camouglage amd mimickery, and mutation of human pigments to be similar to chameleons, is the mostly likely cause for humans.
because human color blue green red is mostly in the eye, you can say that humans developed colors in their mucus membranes first, eyes, lips, like blue baboons even, and then they developed rgb hairs or even?
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Here are a series of bottlenecks that could be used to justify this.
1st bottleneck.
One branch of Hominid creatures suffer massive infestation of mites. Infestations are so bad that individuals can die of infections. An evolutionary advantage is given to those with less hair.
2nd bottleneck.
An extreme lack of sources of vitamin D occurs at the same time (many generations in length) that the Sun's output of damaging radiation is abnormally high. While darker pigmentation is advantageous to block the damaging radiation, it also blocks creation of vitamin D. A small portion of the population has a trait that allows pigmentation cells to steadily darken in proportion to the intensity of the sunlight, fired off by nerves. The lighter skinned population suffers from skin cancers, or becomes primarily nocturnal, and the darker skinned population suffers from Vitamin D deficiency. The variable skinned people are able to produce Vitamin D in the mornings and evenings, and can hunt on the open plains during daylight hours.
3rd bottleneck
The avian predator (which could be a Golden Eagle) starts heavily predating these plains-hunting hominids. A small portion of the population has some limited control of their skin, allowing a "splotchy" appearance. Rather than the tans and browns of current humans, some ability to produce actual color is available, but very rudimentary.
From here, it continues along your path. As these Hominids grow larger, they are no longer suitable prey for the avian (or the avian died out). Fine control of the color changing ability becomes a primary attractant for mates, giving heavy advantage to those with even slightly better ability.
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I don't think this is justifiable. The Kingdleon made is a strong one, though I would also through in that i"m not sure sexual selection could justify maintaining such a trait for so long as you described it in any case. Once the bird died the odd skin color would be a handicap, allowing some parts of the body to be vulnerable to skin cancer while still risking vitamin D deficiency, getting the worst of both pigmentation. Now it's true that sort types of 'harmful' traits in males can spread due to the 'handicap principle', but this wouldn't be a good example of a trait to be encouraged via the handicap principle. long term monogamous herd species wouldn't depend on the handicap principle for mate choice anyways, the means for selecting a mate in social herd species is very different and more complex, physical appearance is no longer the sole definer for picking a sex, with intellect and social skills growing more important, limiting the effect that sexual selection can drive physical features towards a harmful extreme.
However, all that is moot for a far more basic reason. There would never be a flying species that hunts humans, were too big. There is an upper bound on how large any flying creature can get, a side effect of the square-cube law and the difficulty of maintaining flight. No flying creature could ever be large enough to pick up grown humans in order to carry their body somewhere safe to eat (it wouldn't be safe to eat the body where killed, surrounded by angry humans who may not approve of your killing them either).
Furthermore, humans are kind of bad prey. Were bony and provide poor meat content and if were in the middle of a human bottle-neck as you suggest were not even common enough to be worth hunting. There is not going to be a creature capable of regularly hunting us, to the frequency to play any noticeable role in our evolution, and which would find us worth hunting.
Even if such a bird did exist, this sort of camouflage wouldn't work for us. Were a social species, we move in herds; and were *tall* species that stands out from a distance. It would be easy to find humans in the plains and other areas we would be traveling once we were bipedal. We won't be in areas that we could realistically hide from something flying with our upright stance and herd movement, and our instincts would be less to hide and more to defend each other by attacking the bird most likely, since the bird would barely be big enough to attack our young and thus vulnerable to adults attacking it to protect their children.
If you want variable coloration I wouldn't have it evolve at all, make it an 'accident'. Mutations can occur all the time that do rather random things, and as long as those mutations aren't harmful they can potentially stick around, even if they are not beneficial either. If a random mutation happened to cause odd spread of melanin in skin cells appeared during a population bottle neck it could have spread by 'luck' to most of the population without it necessarily being an evolutionary advantage, simply not evolutionary disadvantageous either.
Of course since random skin tone *is* going to be a mild disadvantage you would need to offer some advantage to counter it, but it need not be a significant one, which offers a few options.
1) the mutation provided some odd protection against UV light similar to what comprehensible said, though if you see my comment there are limits to his suggestion; but I think bit's an interesting idea that may be persuable
2) The mutation causing random skin color provided a completely different advantage. This seems easier to justify. Mutations are not random changes to one or two things, most mutations have many affects, and even many 'harmful' mutations have significant benefits justifying how they managed to spread. Sickle cell anemia, far more harmful then random skin coloration, provides a defense against malaria explaining how it likely managed to spread so rapidly in our gene pool, to give just one of many examples.
Thus I would say that this completely random mutation happened to prove useful for reasons unrelated to the skill change. The mutation also happened to somehow provide some minor defense to some sort of disease or cancer etc. The ladies would notice that children of multi-pigment males live longer and prefer to mate with them, spreading the gene rapidly during the bottle neck where it was relevant. Given enough time if the disease or other thing the random pigmentation mutation protected against was less of a threat I would expect women to stop being attracted to it. However if you set this mutation as occurring during the most recent bottle neck it's possible the preference will still be around, having not had enough time to evolve away. Though it would likely only be prevalent in the appropriate parts of the world where neither Vitamin D deficiency or cancer caused by UV rays were too common. So perhaps it would mostly be prevalent in those about mid way between equator and the north/south poles.
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Imagine you're on vacation in Greece. It's a nice sunny day, so you decide to go for a swim. The bottom of the sea is full of some greenish-brown ugly seaweed, every stone is covered by some fuzz and all around are scattered these things that look like poo and many more things.
That's why I decided to do something. I took control over the world and now I will destroy all life in the oceans! (Muhahahahahaaa!)
Just a little problem - I don't know how. I want to destroy all (or as much as possible) visible life of Earth's oceans in less than, let's say, 10 years
Bonus points for an answer:
* Not destroying all life on Earth, leaving terrestrial life as untouched as possible (anyway it will slowly die out without the ocean life support)
* Destroying even deep-ocean and bacterial life
* Cleaning up after the wipeout and making the seas accessible to humans
* Doing this as fast as possible
I thought of various methods, like poisoning the sea, but I'm not sure, what to do.
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The answer is (fortunately maybe?) no, you can't. The ocean is home to some of the Earths most hardcore extremophiles that can withstand conditions we couldn't perceive. What is poison to one species is essential to life for another.
The largest extinction event in the globes history was actually caused by oxygen, not lack of oxygen...known as <https://en.wikipedia.org/wiki/Great_Oxygenation_Event> (oxygen catastrophe is how I know it) started when the first photosynthesis plants started creating oxygen. With nothing to consume the oxygen, this process went out of control and killed the vast majority (98%?) of life on the planet (oxygen is actually toxic to this life). Even if you were to rid the ocean of free oxygen and kill the majority of that life, these little guys <https://en.wikipedia.org/wiki/Obligate_anaerobe> would be in seventh heaven and begin taking the place of those that died off.
That will follow with any attempt to rid the ocean of life. No matter how extreme you make the conditions in the ocean, there is already an extremophile ready and waiting to thrive in these new conditions.
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This isn't hard science...
The [Great Dying](http://science.nationalgeographic.com/science/prehistoric-world/permian-extinction/) at the end of the Permian was a period when most sealife perished. It was caused by anoxia: for various reasons large part of the ocean had no oxygen in them.
You release a microbe that breeds prodigiously, produces an oily secretion, that floats (and rapidly builds up to a great thickness: several metres of rancid oil) and an acid waste product that raises the pH of the oceans. The microbe rapidly uses up the oxygen in the oceans, producing acetic acid, and the oily secretion prevents oxygen from getting in.
Sea life needs oxygen, so the seas are killed.
But then, the population of the microbes crashes as they use up the resources of the sea. The oily surface reacts with the air, becoming denser and sinking to the bottom (where it festers, releasing toxins that poison the sea bed). The surface,however is now clear, but dead.
The death has been dramatic due to the incredible speeds of growth of your microbes. The seas are dead, and we are still here.
We die soon though, since we have just knocked out the most important plants that regenerate oxygen: phytoplankton. So the climate is knocked right out of kilter. Global warming follows since there is nothing to absorb the CO2. The carbon cycle is badly disrupted. Food becomes scarce. Human megadeath occurs.
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Some of the creatures that live in the Ocean are so durable that the only way you would wipe them out is to dry up the Oceans and irradiate the remaining puddles. But that has a serious effect on terrestrial life.
So my next best thought would be to bio-engineer a series of highly invasive super-creatures (generally micro-organisms) with a kill switch. The aim of at least one of those creatures is to wipe out the lower end of the food chain by either breeding into the main food source(propagating the kill switch) or killing its competitors and damaging its own food-source (so even if the species dies off competitors still cannot survive.) It would probably take many long years but when the creatures have ran their course (when they have completely taken over a link in a food chain) you just trigger the kill switch. Killing the bottom of the food chain off means that the creatures higher in the food chain also die.
Because there are a large variation of creatures at the bottom of the food chain, you would need quite a few variations of predators/invasive-creatures to do the job.
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One of the Stack Exchange's most popular topics is remaking mythological and fantastical creatures with realistic, believable anatomy. Usually, the answers go that for an angel's anatomy to be believable, he'd either have wings like a bat instead of a bird (the former's being essentially very stretched-out hands connected by skin) or have very long arms, a very large chest and hollow bones.
But all these angelic posts have just one thing in common--the angels have the traditional number of wings, that being two.
But millions of years ago, there once lived an aerial vertebrate that is a cut above the rest.
[](https://i.stack.imgur.com/nyZcl.jpg)
Meet *Microraptor zhaoianus*. This small dinosaur is unique in that all four of its limbs had been upgraded into wings.
It should make sense, therefore, that the existence of a four-winged dinosaur should make a four-winged angel a possibility. Even so, since the anatomical differences between an aerial dinosaur and an aerial primate are vast, questions need to be taken into consideration:
* What advantages could an extra pair of wings bring?
* How would the wings be positioned during flight?
* Would powered flight be possible?
* If the legs had been converted into wings, would that hinder one's ability to walk on the ground?
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There have been many questions investigating large flying creatures. The ones who try for any kind of realistic biology/physics estimate basically boil down to:
* Flying creatures above some 70kg (some say 200kgs) are simply **impossible** in Earth like circumstances, and even these estimates may be pushing it.[1](https://worldbuilding.stackexchange.com/questions/819/what-is-the-maximum-size-of-a-flying-creature)
* All flying creatures had/have supremely light builds, and large wing spans.
* The biggest creatures ever to fly were only able to glide and ride updrafts, not the kind of flappy and fast flight we know from movies.
Sorry to break it to you, but when using the [biology](/questions/tagged/biology "show questions tagged 'biology'") or [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") tags there will be no Angels, no Griffins, Hippogriffs, Dragons, etc.
--> Adding a second set of wings to your angel creature will really not help your case: the physical limitations apply independent of the amount of wings as they're based on the creatures mass (depending on volume) vs. its muscle strength.
For detailed explanations see also:
* [What is the maximum size of a flying creature?](https://worldbuilding.stackexchange.com/questions/819/what-is-the-maximum-size-of-a-flying-creature)
* [Wing surface area for large flying creatures](https://worldbuilding.stackexchange.com/questions/30184/wing-surface-area-for-large-flying-creatures)
* [Can you simply scale up animals?](https://worldbuilding.stackexchange.com/questions/316/can-you-simply-scale-up-animals)
The fundamental principle which lies behind the size limitations is called the Square-cube-law. There is a [Wikipedia Article](https://en.wikipedia.org/wiki/Square-cube_law) explaning it in detail.
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[1](https://worldbuilding.stackexchange.com/questions/819/what-is-the-maximum-size-of-a-flying-creature) Some [sources](http://blogs.bu.edu/bioaerial2012/2012/11/24/quetzalcoatlus-largest-flying-animal-or-not/) suggest that the [Quetzalcoatlus](https://en.wikipedia.org/wiki/Quetzalcoatlus), the largest known (supposedly) flying animal would have been unable to take off with a weight of 200kg.
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Your 4 questions are all answered by reference to the noted dinosaur. I’ve seen it reported on TV with studies trying to figure out what flight posture it would use etc. [Here](http://blogs.scientificamerican.com/tetrapod-zoology/flight-of-the-microraptor/) is a more recent study:
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> The tail operated as a lift-generating structure, meaning that Microraptor can accurately be described as a five-winged flier, not just a four-winged one.
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Even cooler: **five** wings!
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> Notably, Microraptor was never an efficient flier: it suffered from extensive drag in all simulations and was aerodynamically unstable, performing best when moving quickly. It was well able to glide no matter what the feather or wing configuration: in fact, we concluded that all Microraptor needed in order to glide effectively was a flat wing surface – feather asymmetry, anatomy and configuration didn’t make that much difference (Dyke et al. 2013), a discovery which supports the view that the evolution of theropod wing and feather anatomy did not occur within an aerodynamic context.
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So, not particularly good, with structures just beginning to be repurposed for flight but far from optimized toward that new purpose.
It doesn’t have advantages. That’s why birds don’t look that way now. Yes, it hinders the ability to walk on the ground (they were aboreal anyway) and again that’s why they don't look like that now. Powered flight? Maybe, barely. Posture: limbs straight down (see the linked article).
[](https://i.stack.imgur.com/o1iEf.jpg)
So an *angel* or other creature like this would clearly show that flight is an accidental possibility of anatomy evolved for other purposes, only slightly evolved toward that new direction. This might also have compromised the old purposes, perhaps more significantly than the gain of new purpose.
So, not good at flight. Needs another hundred million years to compare with what we’re used to. Maybe OK for (e.g.) making a tent over a clutch of eggs, especially handy for incubating a larger brood since it wasn’t as warm blooded as modern birds and didn’t have the huge flight muscles to generate warmth. The anatomy shows its history more than its future.
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As it turns out, [David Attenborough's Conquest of the Skies](https://en.wikipedia.org/wiki/David_Attenborough%27s_Conquest_of_the_Skies_3D) episode 2 was on PBS yesterday. It features the Microraptor, including realistic CGI reconstruction of its appearance and behavoir walking, climbing, and flying.
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I have been thinking about the 4-winged angel and how to broaden my scope beyond the sadly stereotypical. And get that green checkmark!
The problem with bilateral symmetry is that vertebrates are so committed to 4 limbs - as has been pointed out. But our cousins the echinoderms, bilateral as larvae, acquire a more open-ended approach to limb number by switching over to **radial symmetry**. A radially symmetric creature with 5,6, 10 or more limbs is no stretch at all for the echinoderms. Lovecraft's crinoid-like Old Ones were angelic in that they had wings (3, though often drawn with 2 - stereotypes again!) and were radially symmetric.
[](https://i.stack.imgur.com/vKU7o.jpg)
from [deviantart.net](http://img14.deviantart.net/ffa3/i/2008/356/2/2/elder_thing_the_return_of_the4_by_skullbeast.jpg)
So: how might a radially symmetric echinoderm angel look? Sea cucumbers are radially symmetric with 5 major poles; here I have used 4 for wings with the 5th left for another appendage. Please imagine it flying high above that gravel.
[](https://i.stack.imgur.com/jUrPb.jpg)
For a more standard angel I used a 10 arm starfish - all 4 wings and arms and legs! The head had to go in the middle.
[](https://i.stack.imgur.com/SBTyu.jpg)
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Seraphim have 6 wings.
[](https://i.stack.imgur.com/ERiXS.jpg)
These 2 are cuties but there are many other depictions on line. Interestingly seraph translates as "burning one" and also "serpent"; googling for seraph turns up some Hebrew pages on various snakes.
In any case - maybe your 4 winged angel is a seraph who is keeping 2 folded up.
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Imagine a species that evolved almost identical to our own, except for one difference. A child's sex is not decided by the presence of a Y chromosome, and all embryos have the potential to evolve into either sex. The mother can decide the sex of the child she carries through regulation of hormones released during early development, which she has at least partially-conscious control over.
I'm wondering rather we would have the same sex distribution as we have now? Keep in mind that in the wild a sex distribution of 50/50 would be expected due to [fisher's principle](https://en.wikipedia.org/wiki/Fisher%27s_principle). However, technology tends to modify the way humans view the world. I suspect primitives humans would have the same 1:1 ratio, but would modern humans with modern technology and culture still maintain this ratio? what factors may cause a change in this ratio.
P.S. Keep in mind the evolutionary psychology. They would have evolved to have an instinctual understanding of fisher's principle which would likely limit extremes shifts either way.
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I suspect that you would get boom and bust cycles. Girls would be more valuable when they became scarce and people would have more. Boys would be more valuable when girls were too abundant and people would have more. But group think in relation to current conditions would probably prevent a stable equilibrium without some sort of legal requirement.
In the same vein, at least until the New Deal, boom and bust cycles in agricultural commodities were commonplace due to the same sort of mechanism each season until a certain degree of governmental guidance was inserted into the process, because farmers responded to very limited information and decision making was very chunky (you only get to decide what to plant once a season) rather than a continuous feedback process.
A side effect of that is that social mores would oscillate a lot. This is because a lot of quite complex dating/marriage/gender relations/gender power structure/etiquette turns out to be powerfully influenced by the male-female ratio. This is a quite general phenomena. For example, the way young men and women interact in small town residential colleges where women significantly outnumber men (e.g. at historically women's liberal arts colleges that went co-ed) differs greatly from how they interact when the proportions are reversed (e.g. at military and engineering schools). It happens at the level of whole societies as well.
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The exact ratios will **depend on cultural influences** in any society though large deviations from 50/50 will naturally be self limiting over time.
Given the prevalence of patriarchal societies throughout human history, a strong preference for male children would probably prevail because males are stronger and can work in the fields. Males also make good soldiers. Parents want wives for their sons thus making daughters valuable too though they will be under the same pressures for males.
For example, the One-Child policy in China showed that culture's preference for males. India also has strong preferences for male children.
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Boys would likely outnumber girls.
A modern society doesn't last long because the rate of technological change is so rapid. Cultural behaviors remain long after technology makes them obsolete.
If we look back at our stone age ancestors, the obvious best way for a male to pass on his genes is to avoid wars where he might get killed. However for the group to survive, the males must attack other groups (to keep them from becoming more powerful) and defend against other attacking groups. Failure to produce a new group of warriors with each generation leads to the culture of the group being destroyed. Thus most societies teach a warrior culture to boys so they are willing to sacrifice themselves for the good of the group.
If parents can choose the sex of their child, this warrior ethos will be expanded to include parents so that parents will have more boys to satisfy the needs of the culture. While this will limit the natural growth rate of the tribe (fewer girls to have babies), it will be made up for by capturing girls from other tribes to serve as child-bearers of the next generation. Obviously the parents wouldn't be making the best individual choice, but the culture would compel them and the culture would survive.
This could lead to an interesting situation where there are subordinate girl cultures and more powerful boy cultures. One powerful tribe in the area would birth an excess supply boys, and the other subordinate tribes would all birth an excess supply of girls. In this case the numbers might reverse and result in a larger number of girls being born.
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**This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information.
Note: This sprung from [some annoyance](http://meta.worldbuilding.stackexchange.com/questions/2211/a-hard-science-ultimatum) I've had with the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") tag, and the goal of this question is to attract some really high-quality answers that any question using the tag deserves. An answer that meets the tough criteria of the tag will receive a bounty, and my gratitude.
The Milky Way and Andromeda will collide a few billion years in the future. Stellar collisions will be rare because - as Douglas Adams put it - "Space is big. Really, really big." In the galactic disk, the number density of stars is quite low. Chances are, the Solar System will not be ejected from the galaxy or collide with another star.
I'd like the star in my planetary system - similar to the Solar System, for all intents and purposes - in a spiral galaxy like the Milky Way to collide with another star in a spiral galaxy Andromeda, during the collision.
Obviously, there's no way for there to be a 100% chance of this happening. I'd settle for a 90% chance, give or take.
What stellar number density would both galaxies have to have?
Or, [as Ayelis put it](https://worldbuilding.stackexchange.com/questions/19044/what-stellar-number-density-would-two-galaxies-have-to-have-for-another-star-to#comment47280_19044),
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> So basically, how many stars (of a typical stellar class distribution) would the Andromeda galaxy need to contain within its current bounds in order to pose a reasonable (90%+) threat of a stellar collision with our Sun when our galaxies collide?
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I am aware, by the way, of [this paper](http://arxiv.org/pdf/0705.1170v2.pdf) by Cox and Loeb.
Remember, this question has the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") tag. Make sure you understand what kind of answers are expected. I don't want to scare anyone off, but I really do want awesome answers here. Good work will absolutely be rewarded.
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Note: Yes, I know that the resulting number will be quite large. However, it will be finite and calculable. Simply saying, "It's too large because [x,y,z reasons]" is not enough. The equations do not lie.
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Well, this is easily answered, but first we need to get a few assumptions stated. First, let's assume that all stars are the same size as our sun, about 5 light-seconds across (I'll use ls often in the following, as a contraction for light-seconds). Second, we'll assume that our system will pass through the Andromeda pretty much on a diameter through the galactic disk, for a path length of 260,000 light years. Third, the Andromeda will be modeled as possessing a uniform density of N stars/cubic light-year. This is clearly not true, but we need to start somewhere. Finally, two stars will be said to collide if they pass within the Roche limit for the sun, 2.5 times the radius, or 6.25 ls.
The first thing to realize is that, at the current approach velocity, 110 kps, it's going to take a looong time to make the first pass through — about 700 million years. Second, the Milky way and Andromeda will continue to interact after they pass each other, eventually forming the Milkomeda galaxy, so looking at the first pass-thru is not nearly the whole story. Finally, the density of the Milky Way is irrelevant, since we are only dealing with the behavior of a single star.
So. Let's start by modeling the path through Andromeda as a series of volumes 1 light-year on a side. That will be 260,000 of these volumes. It is straightforward to determine the collision probability within any given volume. Actually, we start by determining the miss probability; that is, the probability that the Sun will miss all the stars in a volume, and raise that to the 260,000 power to get the probability that the Sun will miss all the stars in its path. As it happens $.9999911^{260000} = .0988$. Close enough. So the probability of collision in a single volume must be $1 - .9999911$, or $8.9 \times 10^{-6}$.
Now let's think about one target volume. Its area is 1 light year by 1 light year, or (if you do the seconds to years conversion) $9.94 \times 10^{14}\ {ls}^2$. The critical area around each star is $30.7 \ ls^2$. The miss probability is high enough that we can simply ignore the possibility of one star "hiding behind" another.
Then the number of stars required to block $8.9 \times 10^{-6}$ of the volume's area is given by
$$8.9 \times 10^{-6} = N \times 30.7 ls^2 / 9.94 \times 10^{14} ls^2$$
and $$N = 8.9 \times 10^{-6} \times 9.94 \times 10^{14} / 30.7 $$
so $N = 2.9 \times 10^8$, or in rough numbers 300 million stars / cubic light year.
In other words, assuming uniform spacing, the stars in the Andromeda galaxy would need to be spaced at 800 light-minute intervals, assuming cubic packing. Another way to look at it is that an equivalent spacing closer to home would result in 2900 stars between us and Alpha Centauri. Or, even better, this density corresponds to packing the entire Milky Way into a volume 10 light years on a side.
Can you say, "supermassive black hole"? I knew you could.
That's not to say such an assembly of stars would constitute a black hole - only that it's just a matter of time.
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**It's not that much about density**
I'm not an astrophysicist, I love reading about space and would love also to have a real awesome hard-science answer to this question, but while reading up on it this is what I came to conclude.
To answer this question properly (which I doubt I will entirely), you first need to determine two things. 1 - how star collisions happen, and 2 - how dense is your average galaxy.
1 - I'm basing this off of this page (which I think is plausible but does not make it hard proof) [Can Stars Collide?](http://www.universetoday.com/107244/can-stars-collide/). The probability no matter what the event of 2 stars directly crashing into one another is ridiculously low. If you consider the speeds at which stars travel through space, the vastness of space etc... Even if 10 stars were to pass through our solar system right now, the chances of any of them directly hitting the sun would be very slim. (That being said they would still completely mess up *everything*). What is much more likely to happen, is depending on the speed at which they *meet* the stars would either start orbiting themselves and eventually merge, or if meeting at ridiculously high speeds and passing close enough slingshot into one another and blow everything up. The latter however is unlikely to happen. [Scholz's star](http://www.universetoday.com/119038/a-star-passed-through-the-solar-system-just-70000-years-ago/#at_pco=smlwn-1.0&at_si=557affd274f2c9d6&at_ab=-&at_pos=0&at_tot=1) passed through our outer Solar system a couple of thousands of years ago and its trajectory was only slightly perturbed (and it is much smaller than the sun).
2 - Galaxies are fancy to look at from afar and seem to house ridiculously huge amounts of stars (and look rather dense). Once again that's just because the human eye cannot even begin to represent the vastness of space. From Wikipedia I found that the density of stars in space surrounding the Sun (which is far out from the center of our Galaxy which is denser) is of one star per 284 cubic light years. (That's not a lot — Scholz's star passed within .8 ly of the Sun) The core is thought to have about 500 times that density (or 1 star per 1.75 cubic ly) and that's ignoring the fact that dust, gases, and the gigantic black hole at the center of it accounts for most of that mass. Still even if it were 1/1.75, again probabilities are still ridiculously low, although making huge amounts of merges and orbiting stars much more likely.
All of that being said. When Andromeda *merges* with the Milky Way (because if you've read all of the above I trust everyone understands there won't be any explosions on a galactic level) a few dozens of stars will most likely merge or collide with one another closer to the cores. The galaxy will change, tidal forces reshaping it, but with the relatively low density of stars all around, most of that will occur with very little effect on the stars of the outer parts themselves. Many more stars will likely collide and merge near the core in the aftermath but not that much more than whats already taking place anyway.
What would be needed for the Sun to be hit.
* First off if we *merge* into Andromeda near its core, that would obviously up the chances of the Sun merging/colliding with another star by a lot, yet were still talking about low probabilities and that probably won't happen because I assume the cores will attract one another. Seeing as we're far from the center that leaves us relatively untouched, but then who knows how the two galaxies will merge. Maybe Andromeda will be coming at an angle and its core will pass through the arms of the Milky Way before reaching our core.
* Second, if that were to happen, we'd either end up sucked into Andromeda's core (which I don't count as a collision, even though it's just as world-ending) or get trapped in it which means that sooner or later the sun WOULD merge or collide with another star but only simply as a result of being near the core of the new formed galaxy.
So the only way it seems (to me) to have a high probability of hitting one of Andromeda's stars is to pass very near its core.
Most of everything I've written comes from searches on Wikipedia (which is not absolute truth or devoid of errors) and the links I posted. Hope it helps.
<https://en.wikipedia.org/wiki/Milky_Way>
<https://en.wikipedia.org/wiki/Stellar_density>
<https://en.wikipedia.org/wiki/Stellar_collision>
<http://www.universetoday.com/119038/a-star-passed-through-the-solar-system-just-70000-years-ago/#at_pco=smlwn-1.0&at_si=557affd274f2c9d6&at_ab=-&at_pos=0&at_tot=1>
<http://www.universetoday.com/117778/rogue-star-hip-85605-on-collision-course-with-our-solar-system-but-earthlings-need-not-worry/#at_pco=jrcf-1.0&at_si=557b0d5aa2f0b54c&at_ab=per-2&at_pos=0&at_tot=1>
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The criteria can't be met.
Lets look at the problem a bit differently—lets cast a ray randomly (but on the correct angle of approach) through Andromeda and see if it hits something. The ray needs to be a somewhat thicker than the sun because gravity will take over and turn a near miss into a hit. To get your 90% chance of a hit 90% of such rays must intersect at least one star.
Now, lets take one of those random rays and put an observer at its midpoint (relative to its passage through Andromeda.) He looks along the ray—there's a 69% chance he sees a star looking either way. I can think of no path for the ray that doesn't produce the same effect anywhere on a plane that contains the ray—thus anywhere I look along that plane I have at least a 69% chance of finding a star. If this is the plane of maximum density we would find fewer stars as we looked above or below it but galaxies aren't paper-thin, there will still be quite a few stars as you look some degrees away from this optimum.
Now, the sun occupies about 5 millionths of the sky and yet keeps us warm. What's going to happen when you have a band several degrees wide that's 2/3 stellar surface (and it tapers off beyond that, not an abrupt ending)? You will have an incredible amount of absorbed heat. Our observer is hypothetical and doesn't matter but the stars around certainly do—they're going to be substantially heated by the glow from other stars. That's not going to be one bit good for their lifespan. I don't think there's going to be a galaxy left by the time it gets here if it's that dense.
Note, also, that this math assumes the ray is on the path of maximum density. Since we see a glorious spiral in the sky the actual path is much closer to the one of minimum density—thus most spots in the sky will be star to our observer. With no ability shed heat stars would soon be destroyed. Even without any speedup to their life consider the sun: Energy output: 1.2E34 J/year. Binding energy: 6.9E41 J. It's going to produce enough energy to disassemble itself in 57 million years.
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OK, so we've reached the Clarkian "sufficiently advanced technology" stage, and we can hoover up all the mass in solar system and convert it to something with the tensile strength needed to build a Dyson sphere. See, for instance, [How many worlds would you need to mine in order to make a complete Dyson's sphere?](https://worldbuilding.stackexchange.com/questions/17683/how-many-worlds-would-you-need-to-mine-in-order-to-make-a-complete-dysons-spher) Can we live in it?
Dyson spheres were originally conceived as the ultimate in energy-collection schemes (for a single solar system), but are often described in terms of livable surface area, and I think this is not supportable.
If the DS collects all the energy from the sun, and converts some or all of that energy to "usable" energy **which is then used within the sphere**, the waste heat has to go somewhere, and must eventually be radiated away by the surface of the sphere. Since the solar flux at 1 AU is nominally 1366 W/sq meter, the exterior must radiate a similar power. Assuming the surface is a black body, this implies a temperature of about 390 K, or 117 C. Since energy is flowing outward, the temperature of the inner surface must be at least the same, with obvious consequences for habitability, and note that if the surface is not a black body, and has an emissivity less than one it will get even hotter.
In order to keep the outer surface at 300 K, the power density needs to be about 460 W/sq meter, and this implies a radius of about 1.7 AU. At this distance, the decreased insolation will presumably cause real problems with agriculture.
Much worse, the entire interior volume of the DS is both isothermal and nominally at zero gravity (excepting the equatorial band of the spinning sphere). The atmospheric pressure gradient behaves similarly to the existing earth along the radial direction, but the pressure gradient laterally (towards the poles of the sphere) will be much less, and without the installation of Rim Mountains (a la "Ringworld", or a Dyson Ring) the amount of atmosphere required to proved a breathable habitat at the equator becomes enormous.
Since the interior is isothermal, there would seem to way to produce much of a temperature gradient in the atmosphere, and thus no way to convert water vapor to precipitation. It's true that surface-heated air will tend to rise, since it is of lower density than the layers immediately above it, but it cannot radiatively cool once its density reaches that of a higher altitude. Or rather, it will do so, but only weakly compared to the situation which pertains with radiation to the sky in our current setup. Currently the upper atmosphere radiates almost entirely to space, at a nominal 2.7 K temperature, but in the DS the sky is maintained at the surface temperature. The result would seem to be that the "habitable" portion of a Dyson sphere will be nothing of the sort, with low solar illumination (1/3 of current levels) and virtually no rain.
Or am I thinking about this wrong? And are there other effects I've missed?
EDIT - Please note several points.
1) I believe the interior is NOT habitable. I'm particularly interested in either being proved wrong, or it's even less habitable than I think.
2) At 1 AU, the surface gravity of a solar stationary sphere is 50 ug, so living on the outer surface is not on the table. Furthermore, a space-based civilization outside the sphere must live in darkness, since the peak emission for a 300 K black body occurs at 10 microns.
3) Since the only livable area is in the interior, it seems reasonable (and has seemed reasonable to a fair number of science fiction authors, too) for the civilization to inhabit the interior. While there's lots of room, you only get equivalent gravity near the equator if you spin it.
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# A (Qualified) Defense of Habitable Dyson Shells
Habitable Dyson Shells in the 1-2 AU range seem a bit absurd from an efficiency standpoint. I'll be defending this as being a fundamentally tractable engineering challenge (without unobtanium materials or new physics), not as something we will actually be doing.
## Intro: To Begin With, Build a Dyson Sphere
The first Dyson sphere we create won't be a habitable (or unhabitable) shell, but a solar power collector that beams energy to wherever we need it.
Surprisingly, we can get started on that with something close to *today's* tech -- ability to harvest a bit of fuel and mass from near earth asteroids, solar sails to get around, plain old photvoltaics, rockets, lasers, and (most crucially) self replicating robotic systems. Since manufacturing systems on earth are *nearly* self replicating over all (i.e. they do replicate, with human help), and since no particular step in the supply chain cannot be automated in principle, this is justifiably in the "near term" category, especially if we include robotic telepresence. So this is no mere thought experiment.
To take control of the solar system's available energy, the *prerequisite* for this grand scheme of a Habitable Shell, we'd probably begin by making a light-supported system with a density of around 0.78 g/m^2, aka a *Dyson Bubble*, comprised of statites (stationary satellites). This lets us generate (or rather, take control of) large amounts of energy, which we can convert to antimatter, high-intensity lasers, high velocity kinetics, and so on. Enough that we can more or less do whatever we want with the rest of the solar system, on a scale of years to decades.
We need to process about 200 quadrillion tons (200 exatons) of matter (the mass of Pallas, one of the biggest asteroids) to create this form of power collector if we want to do it near 1.0 AU. On the other hand, at 0.3 AU, it is closer to 20 eT, which is the mass of a medium sized asteroid. This seems to be far enough out from the Sun that we can probably engineer working systems without devoting excessive amounts of effort to cooling and radiation shielding. For mass, we can disassemble Mercury (which is ~300,000 eT), and have lots more left over (which can go towards producing large numbers of robots, habitats, and any other infrastructure we want/need in the mean time).
Energy wise, it appears feasible to disassemble Mercury even if we assume fairly dismal launch and construction efficiency. The energy requirement to pull a kilogram from Mercury's surface, given escape velocity of 4.24 km/sec, is about 18 MJ. Assuming that is being spread out to 0.78 g/m^2, the energy payback time (once you have converted it into solar collector) is only a little over a second! Also note that as we pull more matter from Mercury, the launch energy requirement diminishes, and the total gravitational binding energy is 1.8×10^30 J (an amount which could be harvested in a matter of hours if we had a whole DS).
The thin-film form of Dyson bubble might need more mature tech than we can get to right away -- such lightweight, fragile plates might be hard to control and so on. So there's the thought that maybe we would want to use thicker collection surfaces to begin with. Also there could be a lot of robotic equipment involved in fabricating it, which we might leave in a more traditional orbit rather than spreading it over the whole sun. So maybe we need to start out with 10g/m^2 or so, set up a slightly offset Dyson "ring" (with reflection angle used to modify the orbit of each component slightly so we can spread them out and ensure they never block the light from the earth). In that case, 18 MJ launch cost results in 100m^2 of collection surface, which takes more like 20 seconds to pay for itself. Not really a big deal even so. In fact, we can posit substantial efficiency losses (assume we need 100 times that much mass for the manufacturing robots, etc.) and still make progress on the sphere as a whole in a matter of weeks or months.
The next phase in my mind, after a few months to decades of disassembling Mercury, or partway through that process, ends up being the development of a Saturn-like ring consisting of Mercury's mass mostly converted to asteroids, a razor thin line as seen from earth, with the major solar energy collector systems stretching north and south along the sun's equator (remaining out of line-of-sight from the planets), just far enough to harness 1-10% of the total solar energy. This collected energy gets beamed to sites within the ring that are optimized for reception.
The ring (which I think of as a "manufacturing belt", being 20 times as massive as the asteroid belt and far denser, but still fairly diffuse, and populated with a large number of self replicating robots) could be a decent place to live. Habitats with people in them can be set up to be shielded from radiation with several kilometers of rock, with smaller structures on the inside for gravity. However, really the only reason we'd want people out here is in case some tasks require active telepresence, so we can get to sub-second response times. If too many tasks need human oversight for too long, the project eventually hits a bottleneck until we can either reproduce our way out of the problem or automate them better.
Finally, at some point the manufacturing belt starts churning out a large number of lightweight graphene-reinforced panels that can float over the polar areas. At this point, we can cover the whole sun fairly quickly.
## Creating a Shell
Now that we have a whole sun's worth of energy to play with, plus an obscene number of high throughput manufacturing systems capable of self replication, it's a matter of getting enough of the right materials into a shell.
Jupiter has plenty of matter, but as noted it's largely hydrogen. We might have to move Jupiter (or it's atmosphere) out of the way to avoid gravitational stresses on the sphere. Whether we can transmute the materials of that atmosphere to solids within a reasonable time is open for question. One thought is that, if we can get enough carbon together, we might be able to encapsulate "bricks" of highly pressurized metallic and/or liquid hydrogen within smaller shells of diamond or graphene, which can work as building blocks. It should also be possible to contain large stocks of pressurized H2 inside a series of smaller rocky bodies held together in spherical shapes mostly by their own gravity (gravity balloons).
In any case, if stick with the inner planets, we can build a shell a few centimeters thick (42 g/m^2). This shell could be held in place using ion jets, kinetic slugs, and so on, temporarily, but is nowhere near thick enough to hold against its own weight as a shell if we assume it's made of standard materials. Luckily, holding against its own weight isn't actually going to be necessary. We can instead create a system of strain relief mechanisms that use various forms of energy to hold it in shape.
## Strain Relief Mechanisms
One simple mechanism to consider is kinetic. A series of "tracks" could be mounted throughout the sphere, upon which high velocity chunks of matter (steel, for example) are moved around very rapidly. Niven's Ringworld actually spins fast enough to invert the equation and produce a gee outward, however we really only need a small fraction of that. A set of giant rings that exert outward pressure by spinning at over the natural orbital velocity could be imagined. However, it should be equally possible to use much smaller structures instead.
The total lateral force needed to make sure the structure doesn't collapse is not that much per square meter, the issue is that it needs to be enough to counteract the pressure of gravity upon each local area (which is slight). One possible way to do this would be to set up a series of circular loops, 1km or so in circumference, and induce momentum enough to produce a few gees on the weights contained inside (which could themselves be circular). They would impart constant pressure to the track, via magnetic levitation.
Another mechanism to consider is optical/electromagnetic. As with the solar collectors, 0.78 g/m gives the relationship between normal solar intensity and the sun's gravitational influence. Going to an average 42 kilograms is 5000 times as much. But as long as the light pressure is being used for pressure alone and not to alter velocity, it's not used up, so multiple reflections may be used.
We don't necessarily want to try to reflect too much light from the habitable area directly, but we could imagine a set of platforms comprising 0.1% of the inner surface area that reflect the sunlight 5 million times or so before exhausting it. At 1 AU, that's 5 gigawatts. A bit much, but maybe worth considering with a very efficient reflector.
A better way to do it might be to cover the whole surface with strain relief structures that reflect light laterally, instead of shooting it across the sphere. For example, every kilometer or so, there could be a series of lightweight fins sticking out the outside, designed to reflect light back and forth and transmit the pressure to the structure. Light could be slowly fed in from a laser, and allowed to escape after many reflections. The fins could be much larger than the area they protect, for example 10 km long for 1 km of separation. That reduces the radiation density they handle to 10% or 500 times that of the sun for our 42 kg model. The mass of such fins could be much lower than that of the shell, since they would be very thin.
There's another radiation mechanism to consider similar to the above, but it dovetails with a cooling mechanism, so see below.
A final strain relief source to consider would be magnets. This can be either diamagnetic materials sandwiched between permanent magnets, or permanent magnets oriented so as to repel from each other. This has the virtue of simplicity, and I can't really think of a down side.
## Cooling Mechanisms
If we decide build at 1.0 AU, it's going to be too hot if we can't rapidly cool the outside of the shell. The physics imply that there's no way to cool faster in a vacuum, other than to increase the effective surface area. One way to do this without increasing the sphere size is to string out a long tether made of carbon nanofiber, or something else that has high thermal conductivity per unit mass, every so many kilometers. What ends up happening is that each tether radiates heat in infrared form along the way, then reabsorbs the same heat again from neighboring tethers. This puts considerable light pressure upon the tethers, causing them to "fall" in the opposite direction of the sun's gravity, sort of like a balloon.
So you can string lightweight tethers out quite some ways -- multiple AU, perhaps. There isn't really much of a limit, since the light pressure from the infrared is greater than the solar gravity, and the tether's own gravity isn't very substantial. If the pressure gets stronger than the tensile strength of the tethers, the tether can be made thicker or mass can be distributed along it.
Another way to deal with the thermal energy is to transfer it to matter, move the matter out to a distant point, then move it back again. Hydrogen has a good specific heat density, so we could imagine a system of balloons filled with hydrogen which venture to the outer solar system to radiate, then return after reaching cryogenic temperatures, and reinflate/rewarm upon contact.
## Effects of Size
The OP suggests that 1.7 AU would not receive enough light for agriculture. I doubt that will be an issue. First, plant life could be adapted to need a little less light. Many plant species would survive fine (if growing more slowly) under 1/2 to 1/4 the light. Second, we could set up a gossamer bubble that reflects light half the time and transmits the other half, so as to produce a day/night cycle with twice as much light in the day. Third, we can use fluorescence to convert more of the radiation to visible spectrum. Finally, note that a large amount of visible spectrum light would naturally be reflected by the part of the sphere on the other side of the sun. So all things considered, a much larger sphere should be more reasonable than a 1.0 AU.
## The Problem of Gravity
This is the biggest issue with the whole idea. Solving it with a centrifuge is inelegant, as you don't get to use the inside of the sphere as a landmass that way. Moving to a white dwarf has the issue of not being the problem we are trying to solve. Moreover, gravity as we know it just doesn't work for the inside of a sphere. So we need more of a "clarketech" solution to make sure people fall to the floor and sustain a breathable atmosphere.
Fortunately, an idea that works for this purpose has been thought of that breaks no known laws of physics: [Utility fog](http://www.kurzweilai.net/utility-fog-the-stuff-that-dreams-are-made-of).
Utility fog is a system of microscale robots, which connect to each other using an octet truss configuration, with extensible arms and graspers, all too small to see. With careful programming, you can use them to simulate liquid, gas, solid, and weirder things still, i.e. gas that you can fly through, liquid that you can breathe. What we are interested in is something like the buoyancy effect of water, but made to run in reverse, so instead of floating, it pushes you "down".
Now, that effect alone might not be enough to fool your body. But the inside of your bones and even the matrix between your cells can be threaded with appropriately programmed foglets or comparable micro/nano systems. Thus, the effects could be very close to natural gravity as far as biology can tell, including the prevention of weakening of muscles and bones and the maintenance of normal appetite. As an added bonus, such foglets could be programmed to turn gravity "off" whenever you decide to do so.
Utility fog is a good setting for stories about "magic", since it's pretty flexible. But if you use it this way, remember that it has limitations: For example, you can disintegrate it with heat, and it has finite strength. (Aluminum oxide is preferred over carbon, since we don't want it to be flammable. However, it still obeys the physics that say very small things can be heated up very quickly.)
Another idea for pseudo-gravitation would be to imbue all life with magnetic particles (hematite, say, or maybe some rare earth nanocrystal that works better) and use a magnetized sphere. Since we're considering magnetic strain relief mechanisms anyway, it could make sense. Maybe both systems could be used by different factions on the same sphere -- the magnet people could be those who evolved in an area where the utility foglets broke down, or something like that.
The kinetic strain relief mechanism above might be adapted to become a series of ring-style habitats (actually, you could do away with the shell and make it a set of conjoined rings, each containing a magnetically coupled, spinning habitat that balances out the gravitational pressure). This would give you far less surface area to play with, but some authors might find it more plausible or interesting than programmable nanobots.
## Scientific Advancement Rate
The kind of advanced nanotech (nanorobotics) needed to produce utility foglets is, well, not here yet. Perhaps we need hundreds of years to break through using the current set of laboratories and scientific instruments.
However, if we had trillions of physics laboratories working in parallel, trillions of computers crunching the necessary math, and so on, it becomes harder to rule out rapid breakthroughs. We could also run new kinds of experiment with tougher materials, higher pressure conditions, exotic matter, and so on. So the assumption that we wouldn't make various advancements within years of the first DS is grossly conservative.
Nonetheless, mostly, we just need to intelligently apply what we already know. For the issues mentioned here, as far as I can see, you don't need new science to work around them.
## Conclusion
There's a lot of story potential in the Solar Dyson Shell Habitat idea, and it at least *can* fall under the auspices of hard sci-fi, though smaller habitats have more actual likelihood of happening. The prerequisites are thinkable, and not as far in the future as is generally assumed -- it is *primarily* a matter of having a self-replicating industrial infrastructure, properly organized, which makes use of space based resources. But it also takes some creativity and understanding of the obstacles.
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There are two assumptions that you make which doom the habitability of the Dyson sphere. They aren't inherently wrong, but I don't think they make much sense if such a thing were to actually be built.
Your assumptions are:
1. All energy captured will be used *inside* the sphere.
2. The external surface of the sphere will be perfectly smooth.
**Energy Use**
One of the main reasons to build a Dyson sphere for collecting the entire output of a star is because you've got a lot of things to do with the energy. If, for instance, we were generating antimatter to fuel our interstellar starships then that is a whole lot of energy which we're collecting and using *outside* the sphere. If we keep up our current efficiency for making antimatter we're going to need to grab a whole lot of energy to make usable amounts. For regular trips to other stars, a Dyson sphere will be an excellent source of extra energy.
**The Surface**
Extra surface area with the same radius is simple to achieve. Just look at golf balls. The dimples on golf balls add about 35% to the surface area of the sphere. That's a simple macro structure to add, if on top of that you add microscopic features you can easily increase the surface area required to radiate all additional energy from the Dyson sphere.
Evidence for increased emissive cooling by macro features [is here](http://www.sciencedirect.com/science/article/pii/S0378778810003531) and increased micro features [here](http://www.electronics-cooling.com/1997/09/highly-emissive-ion-beam-textured-surfaces-for-improved-cooling-of-electronic-devices/) for non-ideal black bodies.
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Increasing surface area via texture for an *ideal* black body sphere will likely not increase its radiating power. The Stefan–Boltzmann law applies, but will not change the amount of power radiated away (further detail [available here](https://physics.stackexchange.com/q/185452/45770)). The solution then is a more active release of energy, rather than the completely passive one described.
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The arguments against using a Dyson Sphere design are many:
* Zero gravity. Unless you have a gravity field generator, you're going to have serious problems using the sphere for anything productive except the collection of the star's emitted energy. You can't alleviate this by spinning the sphere. That might make certain sections livable, but others would become much much worse.
* Because of the Zero gravity, you have no atmosphere, no soil, no water, etc, etc. We can assume that, because they've built a Dyson sphere, they've alleviated a lot of these problems, but it's just doesn't seem very efficient to have to rely on artificially creating everything you need.
* Mass requirements. We can assume the mass requirements for a Dyson Sphere are high. Depending on the required parameters (very high tensile strength if you're attempting to spin it to almost nothing if you're not.) You'd need to devour each and every object from the inner planets to the Oort cloud to make sure nothing punches a hole in your new toy. And even then, I'm not sure that'd be enough mass to create it; even if you had a near 100% efficient conversion rate.
But what about this? Let's suppose, for a moment, we don't really want a Dyson Sphere - we just want to collect as much energy as possible. We could keep a strip of the Dyson Sphere open at the 1 AU mark and on the ecliptic plane. In that strip, we could build and orbit small spinning HALO rings. These rings are redundant - we'd fill the orbit with them - maybe put them in each others Trojan orbits, so they're not prone to wander. Next, we fill the 1AU orbit above and below the ecliptic with a gossamer thin material that collected nearly 100% of the star's radiation and beam it at collector stations inside. These... Dyson Hemispheres aren't being lived on, so there's no need to worry about making gravity or whatever and at the same time, we're capturing a very large part of the stars output as energy.
Our population? They're on the spinning rings. Plenty of room and we can make more as we gain more mass.
If anything comes into our solar system, we can fry them with the exo-joule lasers we can power with our Dyson Hemispheres. Put one laser on each 'pole' of the Hemispheres and you have more than enough coverage to safely protect your star system for the foreseeable future.
Just my 2 copper mate.
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This answer provides an alternative to the one you propose.
As an alternative to a Dyson Sphere around a Main Sequence Star, Turkish scientists argue that it makes more sense to build a [Dyson Sphere around a White Dwarf Star](http://www.centauri-dreams.org/?p=32788).
**Statistics**
The Sphere:
* diameter - about $ 1 \times 10^6 km $
* surface gravity - about $ 1 g $
* mass of sphere $ 10 m $ thick ~ $ 6 \times 10^{24} kg $ (roughly
Earth massed)
* stellar luminosity at this distance is roughly terrestrial normal
* temperature - the sphere size is tailored to the White Dwarf to yield the
correct gravity and temperature - so habitable
* living area ~ Earth's area $ \times 10^{5} $
**Safety**
A sphere around a white dwarf is much safer than around a Main Sequence star since you don't need to worry about the upcoming giant stage engulfing your construct.
**Instability**
The sphere still suffers from dynamic gravitational instability. I assume a civilization capable of building such a thing is capable of both figuring this out and fixing the issue.
**Engine**
If you leave a hole in the sphere, you now have an engine to push your construct around too (using radiation & solar wind). You'll need some sort of restorative force (electromagnetic? gravity?) keeping star and sphere co-centered. The acceleration of this engine would be absolutely miniscule.
**Living Area**
Everyone would live on the outside of the sphere under open skies. The atmosphere would remain gravitationally bound to the sphere on its own with no extraordinary measures. If you cut the hole for propulsion in, you'd need to rim it with 1000 mile high mountains (or equivalent) to keep the atmosphere from falling into the hole.
**Lighting**
Light the place by including transparent slices in the sphere and mounting mirrors high above the slices to reflect the light back onto the surface.
**Power**
Power can be generated by many methods. The most direct of these would be to line the inside of the sphere with high efficiency PV cells.
Alternatively, harness the temperature gradient across the sphere's shell (inner surface to external heat exchangers) to drive indirect (e.g. turbine) or direct power generation.
You will probably require heat exchangers to get maximum power efficiency out of your equipment. However, you might be able to utilize passive devices such as heat pipes.
[Answer]
To add a third point to what @Samuel said:
**Why are we living on the surface?**
Why would you be living on the inner surface of the sphere anyway ? After all the inner surface is where you are collecting the energy - living quarters would get in the way of that. Living quarters would make much more sense if they were **in** the ring.
**How many people are you accommodating anyway?**
The surface area of the earth is 510.1 million km^2 and presently supports 7 billion humans plus every other living thing that currently exists (that we know of). The inner surface of your sphere is 5.3x10^8 times bigger than this. This of course largely makes my first point irrelevant, even if you set aside an area 10 times the size of earth in the habitable ring part of the sphere as a "Spherical Park" (National Park being inappropriate in the context) this would make bugger all difference to the energy collection capacity of the sphere.
[Answer]
I am not a big fan of the spheres and I have no solution for the gravity issue, but I'll make a fake answer to make some points about the energy issues that are really bit too long to be comments.
## Outer shell temperature
Can be anything you want within upper and lower bounds set by engineering and the total energy of the star. There are lots more variables than trivial models assume since the structure of the sphere is realistically more complex. There is no one-to-one connection to the temperature of the inner shell. You can use insulation to make the outer shell cooler than the inner shell. You can use heat pumps powered by photoelectrics to make it hotter. Or more robustly simply connect it to hot areas of the inner shell.
## Inner shell is not isothermal
Yes, I said hot areas, there is no reason why areas of the inner shell must all have the same temperature. You can give different areas different albedo. Or simply link different areas on the inner surface to areas of variable size on the outer surface. If areas A and B on the inner surface have the same area but the outer shell radiator A is connected to has ten times the area of the radiator B is connected to, A will be cooler. The sphere is not, cannot be, made from homogeneous mass, it has structure.
## Radius is not that big a deal
Since the temperatures of inner and outer shell are not directly linked, you can use insulation to make the sphere habitable at a distance higher than usual or cooling to make it habitable closer. So you do not need to worry about what the insolation or habitability of a planet at that radius would be. For example if the sphere is larger, you can replace parts of the inner surface with mirrors reflecting light to the inhabited parts. If smaller you might give the inhabited parts higher albedo, so that radiation is reflected to the uninhabited parts.
## Dyson sphere is NOT a habitat
There is no known way to get a comfortable gravity to the inner (or outer) surface. Nor should there be. a Dyson sphere is not a habitat, it is an energy collector. You should build your spin gravity habitats separately and just use the power collected by the sphere to power them. Or just use planets. Technology needed for a Dyson sphere should allow building planets. And the mass needed would allow building lots of them. Just because having six planets on the same orbit is not stable, doesn't mean you can't make it so. It would be easier than building a Dyson sphere. And making the planets habitable would be much easier.
Like I said in the beginning this was not really an attempt to give an answer. Just some comments too long to fit into actual comments. You should not expect any of what I said to be true or accurate. Just some food for thought.
[Answer]
Assuming no [unobtainium](https://en.wikipedia.org/wiki/Unobtainium) you *can't* spin a Dyson Sphere, for the same reason that the Ringworld doesn't work without [it's particular unobtainium](https://larryniven.fandom.com/wiki/Scrith) so a 1g equatorial habitat band is a non-starter. The alternatives are:
* Build two layers, one of which is transparent and holds gas, and people, to stop it/them floating away into the sun.
* Put up with zero gee and cramped conditions similar to the ISS living in the sphere wall between the power capture structure and the external radiating surface.
* Accept that while this thing is huge it is only really good for power capture and build more palatable habitats that use that power, and it's products, elsewhere.
If there is unobtainium then, assuming the object has actually been built primarily as a vast habitat, gravity generators give you uniform surface gravity, a normal atmosphere and a use for most of the power that the sphere is harvesting.
When it comes to heat you're going *have* to refrigerate, on way or another, the areas you want to live in, and you can, to a point, but you probably can't make the whole surface a livable temperature without a lot of flat out hand-waving.
So you *can* create liveable spaces in/on a 1AU solar scale Dyson Sphere but it's not going to be the whole inner face without hand-waving a *lot* of inconvenient facts and almost certainly not the bucolic ideal that is often depicted even then.
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**This question already has answers here**:
[How would multi-race humanoid evolution happen?](/questions/10102/how-would-multi-race-humanoid-evolution-happen)
(5 answers)
Closed 8 years ago.
In the world that I am building, I have four (major) races: Human, Elf, Orc, and Dwarf.
Humans are the run of the mill; average in physiology, psychology and magical ability. They can survive almost everywhere.
Elves are tall, thin, and significantly faster than any other race. Higher than average intelligence, but significantly weaker in magical ability. They don't survive very well in colder climates, but can.
Dwarves are short, stocky, but proportionate. Their muscles are denser than humans and elves, so they are stronger than average. They are not fast, but can easily outlast their opponent in battle. Their magical ability somewhere between a human's and elves, with elves being behind. They do not do well in warmer climates.
Orcs are thick, massive, and brutish. Their race is the strongest in physiology and magical ability, and lacking in psychology. Literally can survive anywhere.
The way the races' bodies are set up are basically the same.
The problem I am having though, is what's a plausible common ancestor to all these races? Since all these races are humanoid, and bipedal, would they still come from a monkey like common ancestor? Or would it be that millions of years ago, a human was their common ancestor?
Knowing a plausible answer to this would impact how the Orcs and elves of this world would view the other races around them.
[Answer]
If one took a common ape ancestor, one could consider these as terrain-related specialisations:
Elves come from heavily forested regions where little light and little of value reaches the forest floor, so they have remained arboreal. Consequently they are light, deft in movement and have excellent spacial awareness. If you wanted to break from the classic fantasy forms, you could give them long arms and fingers, strong for climbing and swinging between branches.
Dwarves may come from one of two places- conventionally they may live in caves, so a smaller body is strongly selected for as it allows them to travel deeper and escape through narrower crevices, escaping dangers of various kinds. To break from classic forms you could give them some of the adaptations of cave creatures- loss of skin pigmentation, poor eyesight, enhanced spacial senses.
Alternately they could be a consequence of island dwarfism, a little like Homo Floriensis are believed to be, which is a very common evolutionary occurrence.
Orcs may be the kind of creature that one thinks of as being brutal and destructive, but their large body type and large population suggest to me that they might actually be more like a hominid bison. A bipedal body layout wouldn't make sense if they were grazing, but living on low-level vegetation would still make sense. This is quite an interesting concept to me as it indicates a very peaceful origin to these people.
Humans present more of a problem as the classic generalists - they will adapt and destroy the environments that produce these other subspecies if they can. Consequently they either need to have good reason to avoid them altogether during the speciation process or they need to be geographically separated- maybe on another continent with challenging sea conditions dividing them. Once the subspecies do meet, the humans are likely to force the others into more defensive situations through natural aggression and destructiveness, which would be a natural source of conflict.
[Answer]
Humans, elves, dwarves, and orcs (HEDOs henceforth) all have the same basic body plan -- they are upright bipeds with four limbs. So the same would be true for their latest common ancestor (LCA).
For reference, the split between humans and chimps occurred about 6 million years ago, and that between humans and gorillas about 10 MYA. So you are looking at a similar timescale between the "present day" and the time of the LCA for HEDOs.
Most likely, the LCA would **not** closely resemble any of the HEDOs. The common ancestor of humans, gorillas, and chimps was basically ape-like, but clearly different from all three modern species.
A more interesting question is what selective pressures created the differences between the HEDOs. As with the famous Galapagos finches studied by Darwin, adaptations occur because they provide a survival advantage. What was different in the environments of elf-ancestors and orc-ancestors, such that elves are slender and delicate while orcs are big and muscular?
[Answer]
As far as we know, developing sapience is a rare thing. So having four races develop sapience at the same time seems highly unlikely. Therefore there common ancestor should have sapience.
Now how would it look? Well as long as it keeps most of the traits common to all four races, that means that it is bipedal. However how much fur it would have is complicated given that we don't know where it lived. In any case knowing where this common ancestor lived could help. Maybe your four races then separated because they went and adapted to different climates?
[Answer]
Since the races are very similar, they are essentially all subspecies the same species, in fact, in fantasy it is common to have an ability to crossbreed.
So essentially some time in the last million years or, probably nearer the short end of the scale, but more than 100ky or so, an earlier species of humans was split by geography and the separated parts have evolved in different directions and have not have time to "fuse" back together. This implies the geographical obstacle was removed relatively recently, in the last thousand years or so, or that the species are still mostly separate.
In practice, seas and deserts are most likely separating factors as sea levels and rain fall patterns change with climate, so new seas and deserts are born. For example, you could have four continents that used to be linked by land bridges (like the Bering Strait), but the land bridges were lost to rising waters and drifting continents over 100 000 years ago, and Ur-humanoids on the continents evolved in different directions. This would have been helped by mixing with previous human population as happened when humans migrated out of Africa. But recently people have learned how to build ships capable of crossing the oceans...
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Most interested in effects during the first <75 years.
Things to consider:
* What type of organization is building the space elevator?
* How is the service sold/rented?
* What is its maintenance/security like?
[Answer]
This reminds me of Arthur C. Clarke's "Report on Planet Three" essay.
Space Elevator charges are per pound lifted - calculations based on electricity consumed
Space Elevator debarking (and charges) depends on whether you want to go into low earth orbit or geostationary.
Advantages of Having a Space Elevator:
1. Easier to transport materials to build Space Hospitals
Benefits of Space Hospitals
* burn patients would benefit because they don't have to lie down on their dressings.
* comatose patients would not have to suffer bed sores
* Amputees would be more agile (no need to move so much mass around in zero-g) they might make good maintenance personnel
* research for example insulin crystal growth
<http://science.nasa.gov/science-news/science-at-nasa/1998/notebook/msad22jul98_1/>
2. Easier to transport materials for assembling and deploying satellites (low orbit or geostationary).
3. Near space exploration (the moon) would be easier since you would not have to worry about rockets to escape earth gravity. Just transport materials needed to assemble ships in orbit. With a space elevator a Space dock becomes a definite possibility.
4. Transport materials for Space Factories. Space manufacturing Typically this includes conditions of microgravity and hard vacuum. Manufacturing in space has several potential advantages over Earth-based industry.
Excerpt from [the Wikipedia entry on Space Manufacturing](http://en.wikipedia.org/wiki/Space_manufacturing):
>
> The unique environment can allow for industrial processes that cannot be readily reproduced on Earth.
>
>
> Raw materials could be lifted to orbit from other bodies within the solar system and processed at a low expense compared to the cost of lifting materials into orbit from Earth.
>
> Potentially hazardous processes can be performed in space with minimal risk to the environment of the Earth or other planets.
>
> Items too large to launch on a rocket can be assembled in orbit for use in orbit.
>
>
>
5. Easier to transport materials for building Space Hotels (which would take the **form of a torus**)
Why would anyone want to go to a space Hotel:
* outer ring of Space Hotel to provide centrifugal gravity. Fine dining is always done in gravity. Tourists will not appreciate sucking steak out of a tube, same for fine wine. What's the point of having a great view if that piece of lobster is floating in front of your nose.
* Inner rings will provide lower gravity (space hotel now has multi-gravity sections)
* breathtaking views of earth
* a chance to do actual flying in zero-g (helmets, elbow and knee pads mandatory - 150 pounds of mass hitting a wall = lawsuit)
* zero-g movement training will be mandatory before entering micro-gravity or zero-g areas (free of course, that expensive hotel rate covers zero-g training). Also you have to unlearn some of your earth movement instincts
>
> <http://www.scientificamerican.com/article/what-do-people-feel-in-a/>
>
> (excerpt) "Beware losing your orientation, however. If your instincts take over, your brain starts telling you, 'You're falling, reach out and catch yourself.' Your arms and legs flail until you regain rational control and convince your brain you are okay.
>
>
>
* how about a zero-g pool a big floating ball of water with a bubble of air right smack in the middle (i still think Arthur Clarke thought of it first)
[Link](http://www.spacefuture.com/archive/artificial_gravity_swimming_pool.shtml) for the pool, which **also** contains economic, safety, health, law considerations for space tourism.
[Link](http://www.spacefuture.com/archive/what_the_growth_of_a_space_tourism_industry_could_contribute_to_employment_economic_growth_environmental_protection_education_culture_and_world_peace.shtml) for **What the Growth of a Space Tourism Industry Could Contribute to Employment, Economic Growth, Environmental Protection, Education, Culture and World Peace** (rocket propulsion from earth to orbit is assumed - but you can concentrate on the effects and amend to suit your requirements)
Space hotels will also provide real scenario examples for security and safety concerns
* can guest inadvertently by accident gain access to restricted areas.
* how do untrained space tourists react to fires
* is it advisable for space tourists to get (space) insurance
[Answer]
In a world that contains enemies of civilization, just one space elevator is not practical. Shortly after the first space elevator goes into service, it would be used to build other space elevators. This would allow the defense of each space elevator to be much like defense of an ordinary skyscraper, military base, AWACS aircraft, or other high-value target -- practical measures could be taken in the vicinity (or region) of the elevator, backed by credible threats of retaliation.
The credible threats of retaliation might include bombardment using kinetic energy weapons (that were deployed using space elevators).
Space elevators would greatly increase the value of land precisely on the equator, especially if a space tramline were built around the world, slightly beyond geosynchronous orbit.
Many of the bases of the space elevators would probably have low-tax regimes, and thriving immigrant-based economies, much like Hong Kong or Singapore.
See also:
* Economic and geopolitical effects of space solar power.
* Economic and geopolitical effects of lunar mining.
* Geopolitical effects of kinetic energy weapons.
* Economic and geopolitical effects of asteroid mining.
[Answer]
[Kurzgesagt says a space elevator on the moon help establish moon as a hub for economic development.](https://youtu.be/NtQkz0aRDe8?t=466)
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Like any reasonable billionaire, I want to breed dinosaurs on my private island - big ones. Like, T-Rex big. Of course, one needs a well-armed security force to guard such an endeavor, lest the merchandise escape and begin devouring tourists at will.
However, I'm also the sort of billionaire who loves experimenting with things, and I've also noticed that it's really hard for people to carry around big, heavy, long-ranged, powerful rifles capable of killing beasts like a fully-grown Tyrannosaur. You *also* really don't want your anti-dinosaur weapons to have the recoil of, say, a .50-caliber anti-material rifle - it bruises the collarbone, you know, and makes it harder for random tourists to use those weapons after the security forces get eaten.
As such, I've decided that my security forces will be armed with - as per the title - automatic shotguns that fire miniaturized anti-tank munitions. Reasonable thing to do, really. My choice of shotgun is the [Saiga-12](https://en.wikipedia.org/wiki/Saiga-12) - nothing out of the ordinary about that, either. However, my choice of ammunition is somewhat less conventional: I'm going hunting with [FRAG-12 ammunition](https://www.defensereview.com/1_31_2004/FRAG%2012.pdf).
Apparently, FRAG-12 rounds come in both high-explosive and armor-piercing varieties, and the armor-piercing variety is a [shaped charge](https://en.wikipedia.org/wiki/Shaped_charge) that can penetrate up to half an inch of steel armor plate - it's essentially a miniaturized [high-explosive anti-tank](https://en.wikipedia.org/wiki/High-explosive_anti-tank) munition.
Shooting FRAG-12 rounds out of a 12-gauge shotgun has a lot less recoil than shooting [big bullets](https://en.wikipedia.org/wiki/.50_BMG) out of [a big gun](https://en.wikipedia.org/wiki/Barrett_M82) (don't ask me why, I leave gun stuff up to [my chief of security](https://www.youtube.com/watch?v=JWEp1gLXhtM)). Miniature anti-tank munitions are also much cooler than boring old bullets, so they're clearly the better option.
**The question: does the shaped charge of a FRAG-12 armor-piercing slug have enough penetration capability to [stop](https://en.wikipedia.org/wiki/Stopping_power) a T-Rex if shot at its head or heart?**
Please get back to me as soon as possible - I might have (completely hypothetically, of course) have gone through with the whole "dinosaur breeding" thing *before* I actually placed an order for good anti-dinosaur guns, and there might (also completely hypothetically) be [a bit of a situation going on right now.](https://www.youtube.com/watch?v=Rc_i5TKdmhs)
[Answer]
# Enough to P\*ss it off:
A 12 gauge shotgun shell, even one filled with high explosive, is a relatively small projectile for anti-vehicle weapons. If I'm reading the specs right, it's actually a tiny rocket that extends the range of a shotgun shell. Then the shaped charge is designed to punch a tiny hole in a hard, metallic surface on a vehicle and destroy the vehicle. In theory.
The [Frag-12](https://en.wikipedia.org/wiki/FRAG-12) is a very small shell compared to the equivalent recoilless rifle rounds. It allows a shotgun user to potentially take on a vehicle with a shotgun rather than a more conventional rifle with an armor-piercing round. If you have a shotgun and need to stop a car, it might cut a small hole in some part of the engine that is vulnerable.
But dinosaurs aren't made of metal, and a shaped charge is good for making a fairly small hole in something. I think this would injure a dinosaur more than a regular shotgun shell, as the explosive force rapidly spread in the soft tissue and burned the dino. It would probably hurt like hell.
But military professionals who want to stop a vehicle will pick a bigger round than this if they have a choice. These rounds are considered pricey for the bang delivered and your link doesn't lead to actual evaluation **results**. Further, dinosaurs aren't made of metal, and the shells will detonate on impact with relatively soft materials like hide. If I'm reading the guide right, it's also unable to operate at close ranges, so once [anything smaller](https://en.wikipedia.org/wiki/Velociraptor) get close, you're pretty much screwed.
If you're going to try and stop a charging T Rex, I'd go with something with a little more oompf, like a [40mm grenade launcher](https://en.wikipedia.org/wiki/M203_grenade_launcher) designed to attach to an assault rifle (perhaps the [AR-500](https://nationalinterest.org/blog/buzz/introducing-deadly-ar-500-assault-rifle-ultimate-firearm-planet-42842) ). This gives you the standard option of bullets with a heavy backup and a bigger impact.
I fear the frag 12 will just make it angry.
[Answer]
Do you know the term Elephant Gun? Calibers like [.600 Nitro Express](https://en.wikipedia.org/wiki/.600_Nitro_Express) or [.460 Weatherby Magnum](https://en.wikipedia.org/wiki/.460_Weatherby_Magnum). Those are what a hunter needs to face an elephant or similar animal, and to bring it down with one well-aimed shot.
But poachers did't use such expensive, specialist gear to bring the African Elephant close to extinction. They used [assault rifles](https://www.nationalgeographic.com/animals/article/160112-Africa-gun-control-poaching-elephants-rhinos). If you talk about an automatic shotgun, you are clearly going the *spray and pray* route. The goal isn't to bring the dino down with a single shot from a Saiga, the idea is to bring it down with a burst. Possibly with [shotgun](https://en.wikipedia.org/wiki/Shotgun_slug) slugs rather than pellets.
The problem with that is what happens between the moment of the mortal injury, and the actual death. The dino might still be able to munch a couple of security guard while it is bleeding out. Do you worry about things like that?
[Answer]
**Maybe with Modifications**
[](https://i.stack.imgur.com/jRgmd.png)
[](https://i.stack.imgur.com/dk9SI.png)
This is the only image I can find about what these rounds do when fired. For scale the round in the top image is small enough to fit inside a normal shotgun casing.
The explosion looks about a foot deep into the target. Of course this target is different from a dinosaur. In the pictures we have a steel plate and then empty space. In the dinosaur we have space full of flesh and bone.
I'd be worried that since the charge is designed to encounter a steel plate, punch a small hole, and inject the explosion beyond the plate, it would explode wrong when it hits a wall of flesh. Worst case most of the explosion is projected backwards and wasted.
The round will certainly open up a large wound on the dinosaur. Dozens of shots might lead to the animal dying of blood loss a few minutes later. But it doesn't look like something that will make the animal fall down dead.
This is something you fire at the dinosaur as it approaches your compound to drive it off. Not something you fire once it is inside eating your men.
The FRAG is designed to shoot an armoured vehicle. Not a big bag of flesh and bones. When shooting a big bag of flesh and bones, you are better of with ammunition designed for bags of flesh and bones.
Do such things exist in the real world? Probably not since historically there was no need to develop a rifle round for dinosaurs. They are a sci-fi staple however, and do things like "splinter on impact, tearing through light armor and inducing profuse bleeding".
That sounds similar to the FRAG but with a different shaped charge that -- instead of making a small puncture wound -- makes a wide superficial wound and sprays it with jagged shards of metal and non-clotting agents. The goal is to make the dinosaur die of blood loss in 30 seconds instead of a few minutes.
[Answer]
You don't need a shaped-charge bullet to kill a dinosaur. Regular armor-piercing ammunition will work.
Sure, maybe a dinosaur has too much bone and meat for a normal, jacketed lead bullet to do the trick, but how about a steel or tungsten-cored bullet?
m955 is a common AP rifle round used in the US, and [it can go through a quarter-inch thick steel plate](https://youtu.be/26F6Sp2Hz_I?t=407). Sure, dino rib-cages and skulls are tough, but are they tougher than steel? I kinda doubt it.
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These would be very effective.
Doing my own research and definitely not stealing from Daron I got these pictures:
<https://i.stack.imgur.com/jRgmd.png>
<https://i.stack.imgur.com/dk9SI.png>
The FRAG12 shells would explode on impact with the T-Rex. Unlike the picture however the explosion will not need to expend energy eating through the metal, and will instead immediately start expanding inside the creature. This would likely make a larger hole.
An explosion like this inside the body doesnt just dig out flesh, it also heats up the flesh around the wound. This does not cauterize the wound, it flash-boils the water in the cells and bloodvessles nearby and causes them to burst. It also sends out a shockwave that also rips soft tissue like bloodvessles and the burned flesh, causing tears for blood to seep through.
With a foot or more depth these shots would be extremely powerful. Especially considering the T-rex width of about 1.8m.
* Any hit on the skull either kills or incapacitates the creature.
* a hit anywhere else on the head will disorient and incapacitate it (a sudden loss of a part of its mouth, nose, eyes or the muscles controlling them).
* a hit on the neck will incapacitate and kill it (arteries and spine)
* a hit on the chest will incapacitate it, a lucky hit or a repeat hit will likely kill it (lung tissue, Aorta, heart)
* a hit on the stomach will incapacitate and potentially kill it (muscle damage on the stomach causes a fall, nerve damage, lower Aorta)
* a hit on the legs incapacitates it, bleeding to death within an hour likely (muscles torn, nerve damage, femoral arteries).
While not every shot will immediately hit its mark, the sheer shock to tbe system it causes will likely incapacitate the creature. Also something that cant be understated: its an AUTOMATIC shotgun. I would say that any 5 hits would almost guarantee an incapacitation or kill unless you are actively trying to keep it alive.
[Answer]
You're going to face the inherent problem of guns: The shooter faces the same energy as the target. Modern heavy guns are about at the limit--some people take injury from them now and the very biggest have an appreciable risk of a broken shoulder.
Thus an anti-dinosaur weapon won't be a gun. Think RPG or grenade launcher, although with a warhead optimized for taking down dinosaurs rather than armor.
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After doing a lot of reading on space warfare on [Atomic Rockets](http://www.projectrho.com/public_html/rocket/spacegunconvent.php), [ToughSF](https://toughsf.blogspot.com/?m=1) and other websites, I was almost sold on laser dominance. Sure, a continuous wave laser could be countered by cooling the hull and hinders itself with the plasma it creates from penetrating deeply, but pulsed lasers circumvent these issues neatly.
However, then I came across [Children Of A Dead Earth](https://childrenofadeadearth.wordpress.com/2016/11/03/index-of-science-posts/), which is a physics simulation of space combat. [Kerbol Space Programm](https://www.kerbalspaceprogram.com), except that Jebediah Kerbin doesn't try to get himself killed anymore, instead he kills others with high yield rail-guns. In CoadE lasers are only viable at really short distances because apparently the [beam quality factor, M2](https://en.m.wikipedia.org/wiki/Laser_beam_quality) is horrible for high powered lasers.
>
> M2 is the beam quality factor, which can be considered a multiplier of the beam waist. So, an M2 of 5 means the beam waist is 5 times that of a diffraction-limited beam. In terms of area, this means the beam is 25 (52) times the area of a diffraction-limited beam, or 25 times as weak. As you can see, having an M2 even in the high single digits will yield beams a far cry from “perfect” diffraction-limited beams.
> In practice, it is not the pumping efficiency, nor the power supply, nor diffraction, which ultimately limits lasers. It is the beam quality factor. In the end, M2 ends up being the number one limit on laser damage in combat.
> In small lasers, M2 close to 1 is easily achieved without issue, but in high power lasers, M2 can easily reach into the millions if not accounted for. This is because generally, M2 scales linearly with laser power.
> Each optical component of a laser affects the M2. In particular, using a deformable mirror to focus a laser at arbitrarily long ranges (such as from 1 km to 100 km) is measured at reducing M2 to between 1.5 to 3. Problematic, but not exactly debilitating.
> But the main issue is Thermal Lensing (Note that this is different from Thermal Blooming, which only occurs outside the laser in the presence of an atmosphere). The heating of a laser gain medium generates a thermal lens that defocuses the beam, ultimately widening the beam waist, preventing the beam from focusing properly. Also note that thermal lensing actually occurs in every single optical component of the laser, though it is strongest in the lasing medium.
> Thermal lensing increases M2 roughly linearly with input power. This means if you have 1 kW laser with an M2 of 1.5 (which is reasonable), this means dumping 1 MW into that same laser will yield an M2 of about 1500.
>
>
>
Other sources only discuss the diffrection limit, meaning a perfect laser and then they call it a day. M2 actually seems to mean that a more powerful laser will perform worse than a less powerful one.
M2 can apparently be fought by cooling the laser (which means even more radiators) or making it physically bigger (more mass). None of these solutions are great.
**Does this really ruin the long-range death-ray, continuous wave or pulsed beam?**
[Answer]
CoaDE was made with a lot of pretty pessimistic assumptions about laser technology. That's resulted in an interesting space combat simulation. The assumptions they've made aren't *wrong*, per se, but in order for them to be present in *your* fictional future too, you have to assume that laser technology has barely progressed from the present day.
Now, I Am Not A Laser Scientist But...
$\mathrm{M^2}$ scales linearly with power due to thermal effects within a *single laser*. As you crank that laser up, even with a fixed and high efficiency, some proportion of the power it is developing will turn to heat, and the heat will affect that laser in some way. More power, more heat, more bad. Pretty clear cut.
*However*.
This is only a problem if your laser cannon is driven by a *single massive laser*. There are two obvious solutions to this.
1. Use a whole bunch of low-$\mathrm{M^2}$, low-power lasers and combine their beams.
2. Use a laser that's not subject to these kinds of thermal effects, such as a Free Electron Laser.
I'm not going to go into option 2 here, but be aware that it is a potentially practical solution to this problem.
CoaDE only has incoherent beam combining, and the creator sensibly observes that it isn't very useful, making option 1 basically uninteresting within the game. That's not the case in the real world, though.
The current [state of the art laser "weapons"](https://spectrum.ieee.org/aerospace/military/fiber-lasers-mean-ray-guns-are-coming) use [fibre lasers](https://en.wikipedia.org/wiki/Fiber_laser). The maximum power of an individual fibre laser is limited in various ways, and one of these is that you want to keep the power down to stop these troublesome thermal effects you've mentioned. For military use, you clearly need All The Power. This was solved by firing a whole load of fibre lasers into the same optics, chucking out one single high power beam. Early designs used incoherent beam combining and had terrible beam quality (lots of interfering out-of-phase beams do that). News designs use [spectral beam combining](https://www.rp-photonics.com/spectral_beam_combining.html). This uses multiple frequencies of lasers, which introduces its own problems (it requires more complex optics, for example) but has significantly improved beam quality whilst increasing power. There's another option which performs [coherent beam combining](https://www.rp-photonics.com/coherent_beam_combining.html) on multiple beams of the same frequency. This is quite difficult, and the technique is not used in industrial or military settings, *yet*.
In the future, having a bunch of phase-locked lasers which can be cleanly combined into a single high-power, high-quality beam is clearly the way to go. [Phase correcting optics](https://www.laserfocusworld.com/optics/article/16554883/photonic-frontiers-beam-combining-combining-beams-can-boost-total-power) or other techniques could be used to synchronise them. The individual emitters might be diode or fibre lasers or something else that forms a super-futuristic high power optical phased array, but none of this is *science fiction*. This stuff is very much an area of active research, and it will come in due course. Only when we do is it worth taking the scare quotes off laser "weapons".
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[Question]
[
Consider the magic power of being able to 'reset time' in the style of *Groundhog Day* or *The Edge of Tomorrow*, ie revert one's environment and physical state to that of an earlier time while retaining memories of the previous timeline, then being able to relive or change that timeline (and being the only person who is aware that there ever was an alternative). Let's say that unlike some examples, it is not necessary to die to invoke this ability, it can be done 'at will', and that the distance back in time that a resetter jumps is not fixed, but controllable within a range that reflects their own natural ability and training.
Given that, the 'level 1' ability to jump back, say, 24 hours, is actually nowhere near as convenient or powerful as the ability to reset a shorter length of time: instead of getting wounded in a battle and having to reset the whole day and fight the whole battle again successfully as you did before until you get to the part you wanted to change, it would be more useful to be able to just jump back 10 mins (or less) and only have to re-fight the most recent stages.
This is especially true since I'm imagining butterfly effects to have a pronounced impact at making the 'new reality' diverge fairly quickly from the old one, at least on a local level. In particular, stochastic processes (like rolling dice) can't be reliably reproduced more than a few metre-seconds from the warlock's world-line.
Fighting warlocks with the ability to do 'short resets' are therefore potentially more valuable than those who can only do 'long resets', and for an ordinary leader looking to hire a warlock as a bodyguard (because they make *great* bodyguards), testing the range of their power is important.
It's easy for a warlock to prove that they are able to time-reset *at all*: you choose a random phrase and write it down, then some time later the warlock tells you what you wrote; if they get it wrong you tell them what the phrase was so they can reset and know it (although if the warlock is legitimate, you'll never see this outcome); if they get it right then they must be legit. It's also possible to test that a warlock can reset *at least* a certain length of time: you write down a random phrase, then a few minutes later the warlock writes something down and gives it to you (having reset into that intervening period with the future knowledge of the answer); then after the designated length of time you open both papers and compare them, showing the warlock if appropriate; the warlock needs to be able to reset back at least as far as the gap to provide the right answer.
**What test can validate a warlocks' claim to be able to reset *at most* a certain length of time?**
If a warlock is actually only able to jump back six hours but claims to be able to do one, I can't seem to devise a test that can't be fooled by the warlock taking the necessary knowledge, waiting five hours until the required 'landing time' comes within their range, then going back and pretending they jumped back one hour when they said they did. Other than methods which involve the warlock getting executed, which I'd prefer to avoid.
A few clarifications:
* There is no way for a non-warlock to detect when a warlock has reset.
* The butterfly effect from the warlock acting slightly differently after a reset can be reduced with careful training, but cannot be entirely eliminated. For instance, asking the warlock to shake a cup of dice would almost certainly change the result of the throw if the warlock reset to before the shake.
* Multiple warlocks exist (and their interaction is something I'm still grappling with), but the test should not require additional warlocks, and ideally should be immune to cheating by them (ie the candidate is not a warlock themselves, but has the assistance of someone who is).
[Answer]
You actually gave the answer in your parameters.
Shake a cup of dice. Both you and the warlock memorize the results. Wait 59 minutes, then write your secret phrase. A warlock who has jumped back an hour or less will be able to write down both the dice roll and the phrase. A warlock who has jumped back further will have a different result on the dice roll. Do not yet reveal the secret phrase.
Edit in response to comments: Immediately roll the dice a second time and have the warlock memorize the result. He is now bound by two random events he cannot predict through time jumping. Wait 5 minutes and then have the warlock recite the second dice roll and reveal his written answers. A warlock who has waited past the second dice roll in order to jump back more than an hour and land in between will be wrong on the second dice roll.
[Answer]
There's a foolproof way you can test it, but it requires a special setup and program.
Basic explanation:
* Lock the testee in a special room for 24 hours
* Door is locked by a randomized password
* Every 15 minutes (or how ever frequently you want) the password is re-randomized
* At the end of 24 hours, the testee may request what the password was at ONE point in time
* They then go back as recently as possible and unlock the door, leaving the test room
* **See how close to the end of 24 hours they emerge**
If they go back too far, the passwords will be re-randomized and no longer valid by the time they would be activated.
Use a huge array of sensors to feed into the password randomizer to ensure high enough entropy, including biometric sensors, infrared and visible camera feeds,
pressure sensors in the floor, humidity sensors, and hell even use their browsing data or gameplay input for while they're burning 24 hours.
Generate passwords that are a long string of random words so its possible to memorize but impossible to brute force, such as: ["Correct battery horse staple"](https://xkcd.com/936/)
Example:
W6 can go back 6 hours. He goes into the cell at 00:00 and waits in the cell until 24:00. He then uses a terminal to request the password for 18:00-18:15 and memorizes it. He then goes back to 18:04, unlocks the door, and walks out.
If W6 gets the password for 19:00, goes back to 18:06, tries to unlock at 19:00, it will fail because it will have been randomly re-generated. Now he'll have to wait until 24:00 to try again.
EDIT: Oh and if they don't leave the room before 24:05, slowly flood the room with poisonous gas to force them to jump back in time. This prevents them from waiting around after the test to make a 6 hour jump look like a 5 hour jump.
EDIT 2: OP does not specify if this takes place in the modern age. However, this approach can still work without any modern tech. Use a well secured cell that the testee can't simply break out of. Then use your preferred physical random number generator to give you sufficiently large numbers, and use those to choose words from a dictionary.
Have this done at an undisclosed location decently far away, and have a messenger deliver the testee's time slot password request and then their ultimate answer. Also burn the password list after the 24 hour test.
No computers are necessary for this, they just makes it easier and less prone to human error / influence.
[Answer]
>
> What test can validate a warlocks' claim to be able to reset at most a certain length of time?
>
>
>
I think you are focussing on the wrong metric to measure warlock effectiveness. Rather, measure their effectiveness by how favorable an outcome they can get for you, by using their time rewind ability, in an independent set of events.
In real life, while this ability of time reset may be usable countless times, it is bound to produce some fatigue on the warlock. A good warlock then is one who can make use of his abilities to get the best outcome in as many resets as doesn't burn them out.
For example, set up a game of football such that you have the best 11 players of the state play against warlock + 10 very bad players, and the measure of warlock's success is how favorable an outcome he can get from those these 10 bad players. Like not being completely routed, to making good number of saves, to having level scores, to actually winning.
In fact, if you had multiple warlocks to evaluate, you could set a tournament of such matches - with every warlock having the ability to reset, the one who can stay the longest with the matches all swinging in his favor wins.
[Answer]
Give them multiple tests, with increasing waiting time.
First test: you reveal the answer after 1 hour, second test after 2 etc.
With this method sooner or later their landing spot will get out of range to answer the question in time!
When they start to get wrong, or hesitate, to get more time on order for their landing spot to get in range, that's when you get them.
[Answer]
Let's say we want to test a warlock for 5 minutes.
* Have 4 ten-sided dice in a cup.
* At t=0 roll the dice by inverting the cup onto a table. The result is now determined but no-one knows what it is until the cup is lifted up.
* At t=1 min the warlock must answer what the numbers are.
* At t=6 min The cup is lifted to reveal to answer to everyone.
* At t=7 min If the warlock was wrong, he is killed.
Only a good-quality warlock would still be alive after 7 minutes. He would have the t=6-7min period to memorise the 4 numbers and shift back to the t=0-1min landing-zone.
A poor-quality warlock would not actually be killed because he would just shift to a few hours before the test and try again (or decline the job). Each time he tries there will be a different number. Potential he could just keep trying until be gets lucky but it would take on average 10000 attempts. At one hour each, that's more than a solid year of 24/7 testing.
The only way the candidate would be killed is if they had no time-reset ability at all and you could screen out suicidal non-warlocks with a preliminary test.
[Answer]
Have all the warlocks stay in a special room for whatever your minimum timeframe for employment is. (let's say 6-8 hours for a minimum jump time as the upper limit).
Surprise them at the end with a situation that would force a quick jump (assuming they will go for a short jump by default). The shock should carry back with them causing a visible reaction in the timeline they jump back to. Use that to gauge the minimum jump distance.
Alternatively, have jumping have a visible tick by default as well (something hard to fake).
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[Question]
[
I am a post-human adapted for permanent life in vacuum and micro-gravity. How might my physiology and biochemistry overcome the following challenges?
*Please note I have a strong cultural aversion to augmenting my body in order to help me survive: i.e. enclosing myself in artificially-constructed protective shells, etc.*
## Current status
**See [Part 1 on radiation resistance](https://worldbuilding.stackexchange.com/q/129268/56294)**
**See [Part 2 on temperature control](https://worldbuilding.stackexchange.com/q/129311/56294)**
At this stage, I look similar to an enormous shining pangolin with interlocking plates of keratin-analogue that are alloyed with steel to protect against ionizing radiation. My radically engineered DNA and its unparalleled checksum and repair functions keep the doctor away. I can move these plates to help dissipate heat and - just like a Terran pangolin - curl up in a protective ball to shield my more sensitive parts. I have a reactive outercoating that allows me to alter my pigmentation (which I typically set to polished silver in order to minimise heat loss).
## **Part 3: Metabolism**
I've reviewed some [previous discussion around convergent solutions](https://worldbuilding.stackexchange.com/questions/122111/what-would-the-biochemistry-of-a-vacuum-dwelling-creature-look-like) but pretty much the only thing I know about my metabolism right now is that I am a liquid breather (e.g. perfluorocarbons). I may be post-human, but I'm guessing water or an equivalent solvent is still essential to my metabolism. My large surface area helps cool me and prevent water loss, but I think I need a highly efficient recycling mechanism to survive without regular access to it.
The molecules fuelling your baseline metabolic pathways - carbohydrates, lipids and proteins - won't do unless I can crack them out of raw materials I have access to in the interplanetary medium, from asteroids, comets etc. Eating, drinking, in fact orifices in general, are also a no-no. You think it's difficult to grow rice in space, but have you ever tried eating a sandwich out here?
Although I live in complex societies with other vacuum adapts and homo sap, and therefore have access to abundant fuel/sustenance, I would like to be able to function independent of industrial civilisation. To live off my 'natural habitat' so to speak - even if this comes at the cost of winding-down to a lower metabolic gear, kind of like hibernating, or stockpiling rawmat when the going is good for consumption over extended periods.
Essentially there's not much food/fuel to be had out here in the void, and I'm not always hanging around easy sources of volatiles like a Kuiper belt object. At the same time, I need to maintain a relatively active lifestyle - overseeing asteroid mining operations, undertaking deep space repairs - rather than floating in circumsolar orbit gazing at the pretty lights of the Milky Way and the CMB all waking.
If necessary, I can dedicate significant amounts of time to activities to generating or harvesting metabolic inputs.
**So, how do I convert fuel or food into energy to power my cellular processes out here in the big dark? What are said sources of fuel/food, and how does my body obtain and store them?**
**[See part 4 on locomotion](https://worldbuilding.stackexchange.com/q/129468/56294)**
**[See part 5 on senses](https://worldbuilding.stackexchange.com/q/129647/56294)**
[Answer]
1. Many comets have naturally-occurring deposits or constituents which are quite complex organic chemistry [see here](http://www.astronomy.com/news/2017/12/comet-67p) so perhaps you are a ***comet capturer and devourer***. This could involve an externaslised machination and initial dissolution apparatus (think like an arthropod here) or could involve a complex mouth which is in effect like an in-body airlock.
2. Obvious, I know, but as already stated, ***light harvesting*** across a wide range of wavelengths can help a lot - you already stipulated your plating was engineered to resist ionising radiation - why not engineer it to capture and convert it instead? Especially as your DNA has extra error checking, so a *little* breakthrough isn't the end of the world. Bear in mind that in open space, far from planetary magnetospheres or from our solar system's heliosphere, there are a fairly high number of UV photons and x-ray photons per cubic meter just... bopping about... so if you can effectively harvest and metabolise the energy ***they*** represent, you will be sitting pretty.
3. Depending upon ***where*** you are, if you are orbiting amongst planets, planetoids or transiting through their spheres of influence, you may be able with your metal enhanced carapace to ***gather energy via induction*** as you pass through magnetic lines of force - this can create a fair amount of energy and has in the past cooked some satellite electronics, so don't assume it's all microwattage - if you develop this one in concert with harvesting ionising radiation, you could for example transition near the lagrange point between Io and Jupiter and gain enormous energy - the interaction between Io and Jupiter's magnetosphere is ludicrously energetic, and there are high energy ionising radiation belts there too.
4. There is significant *interstellar gas* and potentially a fair amount of "dark matter" dust, dirt etc in the *interstellar medium* (estimates of ratios of gas to dust vary, but at a minimum 1% is assumed to be dust of some form) and most of that gas is ***neutral hydrogen*** (average density of about one molecule per cubic cm) but there are concentrations of this in the spiral arms of galaxies which are far higher - if you add hydrogen catalysis to your metabolic tricks, you'll have an unending, omnipresent food source, but one which will never be prolific enough for a surfeit.
4a. If you can detect microwave radiation, and can move yourself in space, you could *hunt* interstellar molecules, which tend to occur in the midst of gas and dust clouds - where they are cooled enough relative to overall higher radiation exposure to not be instantly broken down by UV or X-ray photons, which as we discussed earlier, abound in space.
I would posit that due to your being an engineered specie, your metabolism would in fact be highly multi-faceted and optimised, able to be actively managed, and could encompass multiple pathways, modes and approaches - heck, perhaps like a tardigrade, you can manufacture glasslike DNA and cell wall protective materials inside each cell as you dehydrate and enter a TUN hibernation state, with your metabolic rates dropping to 0.01% of typical, and survive a crossing between solar systems, only to resuscitate when you encounter adequate incident energies.
Hope some of this helps.
[Answer]
Well, if you are floating into space you know that your body will be showered by a lot of photons with all energy flavors.. from radiowave to gamma ray... why not thriving on them, especially the most energetic ones (UV, X-ray, gamma ray)?
You just need some molecules which can absorb the above said radiation, turn into an excited state and then relax back to the original state by releasing the absorbed energy into useful chunks, which you can use for your needs. Considering the energy per photon we are talking here, this might include also molecules which can break and reform.
By accumulating the excited molecules you can cope with times of photonic scarcity, at the price of a slower rate of action. But anyway, if you are floating into the Boötes void there is really not much to be active about, isn't it?
Let's give some figures for the needed surface: assuming an absorption efficiency of 100% at any wavelength, and assuming the only photons come from the Sun, to generate 10 W of power you would need a surface in $m^2$ of about:
* 0.007 at 1 AU from the Sun
* 0.73 at 10 AU (1/3 of the distance to Kuiper belt) from the Sun
* 73 at 100 AU
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[Question]
[
“Permanent” here meaning “significant over geological timespans”, so it would have to last at least 10,000 years and produce a thick enough layer of clouds that it would cover the entire planet in an everlasting dusk. No sun, no stars, no sky. Just endless, dark grey clouds. I have an inkling that a truly calamitous and unfortunate series of coinciding volcanic eruptions and large meteor strikes within a short enough time period might be able to accomplish this in part, but I’m not sure how long the ash cloud-induced ice age would last or how long the planet would remain dark.
Ideally I’m aiming for some civilization-destroying catastrophe that accomplishes everything I’ve described, but is still only just hellish enough that a medieval-level society might be able to survive and eke out a living in the aftermath by farming algae, large insects, and bioluminiscent fungi. This would be taking place in a fantasy world, but I’d like my supernatural disasters to remain explicable by conventional means as much as possible for personal reasons.
Is there any natural explanation for a disaster that would produce the effects I’ve described? What might some of the consequences of a planet like ours entering a ten thousand year-long Dark Ice Age be based on whatever explanation you can think of?
[Answer]
# A permanent cloud cover is tricky
To have a *stable* cloud cover you would need either much higher evaporation, or something that causes a higher rate of coalescing (and at lower water saturations). The former requires higher temperatures and is *unstable* (higher temperatures cause further evaporation etc., until you get a "runaway greenhouse effect" and cook the planet). There is an equilibrium factor given by the fact that more cloud cover raises the planet's albedo, leading to a loss of incoming solar energy; nobody knows for sure whether pushing the equilibrium from its current position to another can be done, and whether such a new equilibrium *exists*.
Increasing cloud formation can be done through [very fine dust](https://en.wikipedia.org/wiki/Cloud_condensation_nuclei) (volcanic dust might do), or through other mechanisms such as [cosmic rays](https://www.europhysicsnews.org/articles/epn/pdf/2015/02/epn2015462p26.pdf).
Both mechanisms, as well as a large cloud cover, are at risk of making the Earth uninhabitable in the long run.
# Cosmic Zones
However, the Earth's entering a region of space with stronger cosmic ray background, and/or a weakening of the Sun's [protective solar wind envelope](https://academic.oup.com/astrogeo/article/48/1/1.18/220765), would result in a cloudier planet. This too risks triggering a runaway effect, but this can probably be handwaved away (the equilibrium would simply move towards a more humid, hotter planet with higher albedo).
# Or... rogue silicon butterflies
The trick here is that what is *gloom* for a human eye is not necessarily a big issue for most vegetal life-forms. Yes, tomatoes and other plants using mostly lycopene and $\beta$-carotene would sort of get it in the neck, but lots of other possibilities remain.
[](https://i.stack.imgur.com/BDhdD.png)
Basically you need *something* high enough in the atmosphere - 4000 m, unless you want light to reach the tallest mountains - that will heavily absorb in the 460-630 nanometer range, where human eyes do most of their seeing. The line that interests us here is the blue one for scotopic vision, since photopic (full daylight, full colour vision) isn't going to do much good anyway.
As to *what*... several doped silicon compounds have a pretty sharp absorption area in that range, *and* can harvest solar energy; indeed, there are applications where the *invisible* wavelengths are harvested, to build something that is both a clear window and a solar panel.
All that remains is picture a self-replicating autonomous system that uses silicon "butterflies" to harvest energy -- in the wrong part of the spectrum. It could have started as a means of reducing the global warming and solving the energy supply problem, until the frequency switch turned it into a nightmare.
There is a problem here, however, no matter what kind of hazing material you come up with.
A lot of energy is going to *not* reach the ground, which means global *cooling* on a worrying scale - global glaciation scale, even.
Perhaps you could explain it off the other way - the global shield was designed to cope with an *increase* in the solar constant. When the necessary doping materials were exhausted and the shield started shifting frequency, the part of the program that controlled the energy balance remained in effect, and the required heating is now coming mostly from the near infrared and red wavelengths.
Vitamin D deficiency is going to be a big issue though.
[Answer]
# Greenhouse effect
Ash will eventually fall down, definitely within your 10,000 years so a greenhouse effect (much like Venus' atmosphere) was the next option to spring to mind.
There are [massive methane deposits in the ocean which can be released into the atmosphere](http://www.straightdope.com/columns/read/2719/are-there-deposits-of-methane-under-the-sea/):
>
> When methane hydrate is mixed with sediment on the ocean floor, it prevents the sediment from solidifying properly and leads to instability. Undersea slides are dangerous for two reasons: they **can release methane into the atmosphere**, already established as a bad thing, and they can cause tsunamis.
>
>
>
So, something triggering huge undersea landslides - a meteor, an earthquake or even just a landslide waiting to happen.
Now, this is pretty catastrophic. Venus is [pretty hot](https://www.space.com/18526-venus-temperature.html) (could melt lead on the surface), largely due to its greenhouse effect. On Earth a runaway greenhouse effect would [end up with temperatures of 1400 degrees Kelvin](https://arxiv.org/abs/1201.1593). There isn't a timescale given but perhaps, for the sake of the story, some measures were already in place to revert global warming and so it has drawn out the inevitable greenhouse effect - giving you a flexible period of time where, whilst hot, humans can still survive.
[Answer]
# You have to get rid of the water
There are a great variety of chemicals you could add to the air to make a hazy cloud cover. The problem is that Earth has an active hydrological cycle, and so will eventually remove most things from the air. Nearly everything chemically reacts with water one way or another, and a great many gasses are soluble in it. So most things you could put in the atmosphere will be stripped by rain and end up in the ocean, where they will be diluted to near uselessness.
So you have to get rid of the water. Now, this is much easier said than done. The Earth has a lot of water. The ocean is a little less than 1/10 the mass of the moon, to give you some perspective. Driving it off isn't necessarily super science based, but this is tagged [magic](/questions/tagged/magic "show questions tagged 'magic'") so lets go.
Once the water is removed, it is somewhat trivial to find something to cloud up the atmosphere. Sulfur dioxide, or example, makes wonderful clouds on Venus, reflecting nearly all the light striking the planet back into space. On Earth it is soluble in water to form sulfuric acid, which then rains back to the Earth, accumulates into the oceans, and eventually gets stripped into the sediment.
Without water, there is no mechanism for removing airborne SO$\_2$ gas, so it will just build up with every volcano. I'm sure you could come up with a dozen more chemicals that would work this same way. So you don't even need to pick a certain chemical; just say that with 99.999% of the water removed from planet Earth, hazy clouds of volcanic gases start to block out the sun.
[Answer]
All you actually need is something blocking incoming light. Still I see just a few non-disastrous possibilities for Middle-age civilization here.
**1. Comet**
Something big (think 0.001 Moon mass or more) crushed into fine dust in the nearest vicinity of a planet will eventually form a disc (after several million years), but initially it may be a widespread cloud wrapping around planet. Having magic around can explain why the comet is dispersed so thoroughly and no big chunks have reached the surface and killed everyone. Dust cloud can't be dealt with using our current capabilities, but will lead to a variant of the ice age that will make current civilization shrink and maybe step back a few tech levels.
**2. Microscopic flying life forms**
Beasts that have chloroplasts and can stay in the air indefinitely long. Those may form the ecosystem akin to multi-layered forest, where bottom layers feed off the wavelengths not consumed on the upper ones, thus blocking most light from reaching the surface. Where have they been before, and why have appeared is up to magic. Or it can be nanomachines in a sort of constrained "grey goo" state, if you wish. Another ice age scenario here, though scientists can discover ways to kill them.
**3. Long oceanic crust shift**
Somewhat mild disaster, that utilizes increased sea volcanic activity to continuously send more vapor into the atmosphere. Still, volcanoes change faster than required by OP, growing new cones and even islands in a matter of few months, which can cease vapor production. Also, more clouds mean higher albedo, lower temperature and more rains, because vapor will condense faster. Not quite disastrous, because it will probably end sooner than modern civilization.
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