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[Question]
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Inspired by the similar questions about [The Cold War](https://worldbuilding.stackexchange.com/questions/31096/what-single-change-would-have-given-the-best-chance-for-the-soviets-to-win-the-c) and [World War 2](https://worldbuilding.stackexchange.com/questions/30758/what-single-change-would-have-given-the-best-chance-for-the-axis-to-win-world-wa),
As worldbuilders the most common question asked is; What if? These what if question usually focus on factors leading up to, about and after a major event, such as a war. Sadly these changes are rarely depicted in a realistic way: it's either not discussed why the change would happen, or even worse, attributed to a superweapon or deus ex machina.
One of the more recent wars was the Iraq War. Because it was a fairly complex and controversial war, with a huge number of social and economic factors in it, there is no realistic way to create a miracle guaranteeing a certain different outcome. Therefore I list a number of disclaimers, in order to make this question fit into the topic of this site.
1. It doesn't have to guarantee an American loss, but it has to significantly increase its probability.
2. The change should have a realistic justification (so no secret Atomic bomb)
3. A loss doesn't necessarily mean that America is taken over (which Iraq didn't have a realistic chance of achieving). If the Iraq power continues to control its area of the middle east, with the United States unwilling to continue fighting in a far off land, or with a peace treaty with the opposition at least slightly favorable to Iraq, it would count as a victory.
4. The change has to be a single event, or a collection of compact, tightly coiled events occurring in a short period of time. It has to happen during, or slightly before the war. The war should, at least for the first few battles appear similar to what happened in real life, even if at different dates or different order, events and participants should remain the same.
With these factors in mind, what single change can I apply to history in order to significantly increase the chances of Iraq winning the Iraq War
[Answer]
At the time I did read some analyst comment that speculated that, had Saddam Hussein really pushed South and attacked Saudi Arabia before the deployment of coalition troops, he would have controlled so much of the oil supply that he would have been able to get a negotiation. In these he would not have been allowed to keep all that he got (too much power in one hand) but could have got some important concessions (the territories in dispute with Kuwait, reparations due to Kuwait alleged illegal extraction of Iraq oil, etc.)
Otherwise, the other has that Saddam tried to make himself the champion of oppressed Palestinians against Israel.
This variation has that Israel government, instead of promising the Palestinians a fair settlement after the war1 and holding tight without answering the attack by Scuds, Israel government orders the expulsion of Palestinians as suspected pro-Iraq sympathisers, and taking part actively in the operations. Then Israeli planes fight Jordan's or Syria planes when crossing over their air space, and tension escalates.
Soon the USA finds that no country (except Turkey) can support them because it would make those countries practically allied with Israel, and that would be politically too costly unless they were directly attacked by Iraq.
1 I bet they are still laughing at how naive the Palestinians were to believe that.
[Answer]
The most probable event(s) I can think of would be the Iraqis getting lucky in their Scud strikes on Israel. Instead of a few civilian casualties, let's say a day care center was hit, followed closely by the destruction of a synagogue during a service, in both cases with massive loss of life resulting.
In this case, Israeli public opinion might well have forced the Israeli government to start attacking Iraq, potentially sucking most of the neighboring countries into the mess. (This, in fact, is exactly what the US worried about.) The resulting massive conflict would engulf much of the mid-East, and the US would, at the least, have been forced to divert forces from the Iraqi effort.
Of course, in the worst case (from the Iraqi point of view) the Israelis might have been so threatened that they would have resorted to their (publicly unacknowledged) nuclear option, and they probably would have been sure that Iraq would have received some reward for starting the whole mess.
Another possibility would be a decision by the US not to trust GPS, which was untried at the time. With no GPS for navigation, the Coalition would have had to try a frontal assault, and would have played into Hussein's strengths (such as they were). In this case, there is every reason to think that the US losses would have been much higher, although I'm doubtful that the end result would have changed much. Conceivably, US opinion would have been affected to the point of accepting a negotiated peace which would have left Hussein in power. I'm not convinced that this would have happened, but it's an interesting possibility.
[Answer]
Imagine a major terrorist attack in the West, with a clear money trail pointing to the Saudi and Kuwaiti political establishment. Keep the unrest of the Kurdish [PKK](https://en.wikipedia.org/wiki/Kurdistan_Workers'_Party#Armed_rebellion_1984.E2.80.931999) in Turkey and the mischief by Iranian proxy groups at historical levels.
The US/the West might decide that Saddam isn't much worse than [Marcos](https://en.wikipedia.org/wiki/Ferdinand_Marcos) or [Zia-ul-Haq](https://en.wikipedia.org/wiki/Muhammad_Zia-ul-Haq#Reign_as_President_of_Pakistan). And "our champion" for a secular, democratic Middle East against those terrorists. At least, he might be excused for going after those fanatics.
[Answer]
Which Iraq war? The one with Iran? They one where Iraq invaded Kuwait to avoid repaying loans from the Iran/Iraq war? Or the one where Bush jr. was to afraid of Iran? Assuming you are talking about the Kuwait conflict, had Saddam been able to goad Israel into preemptively attacking the Scuds and causing civilian casualties on TV, the alliances would have been severely weakened. If Saddam then opened the door to neutral observers who found evidence of WMD's at the site of the Israeli attack that could be traced to or associated with Israel and/or USA, then the the war would have been over. The Arab countries would have united against the west, and the UN would have been severely weakened and might have collapsed (it would certainly have been reformed). The US would have lost most or all its influence in the region and the security of Israel would have been in question. On the good side, the Muslim extremists would have never have got the finance or the support that made them a power for the next twenty five years so there would never have been a 9/11 or a second/third(?) Iraq war or an Isis today.
[Answer]
Had the US exceeded its stated war objective - the liberation of Kuwait - and undertaken to "liberate Iraq" or "save the Shia" (both of which Papa Bush faced strong political pressure to do) we might have seen the events of the second Iraq War and occupation play out a decade ahead of schedule.
For the US to lose, it has to face a war of attrition with its resulting political costs. Occupying Iraq creates the best opportunity for that to happen. It's not a very exciting "What If?" however, because we already witnessed the 2003-2008 version.
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[Question]
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Start with a powerful space-faring civilization. They are Kardashev Type II, having harnessed the total energy output of their sun.
To do this, they have encapsulated their star with a tight-fitting Dyson Sphere which is totally dedicated to energy capture. None of their star's light or radiation penetrates the sphere.
The planets of their system still orbit the imprisoned star, but they do so in almost absolute darkness. The inner planets are all populated, but none of them still have their original atmospheres. Instead, they have each been encased in a defensive shell, then terraformed into planet-wide urban cities.
There is no wild plant life, no living oceans and no undomesticated animals. All of those things have been abandoned on their quest for the stars.
Now as a Type II civilization, they obviously know a lot more about the universe than we do. One of the most important examples of that greater knowledge is a real understanding of how dangerous the universe is. There are lots of militant Type II and imperial Type III civilizations out there and any one of them would be thrilled to conquer and enslave these peaceful people.
So they hide.
It is for concealment that they have blacked out their sun and worlds with opaque shells. Similarly, they use only line-of-sight lasers for inter-system communications.
**The Question**
How close could this civilization's planetary system be to our own, without our noticing the effects of its gravity on objects that we can see?
[Answer]
This is a tough question to answer because any planetary system with more than one planet is tough to analyze. When two planetary systems collide, the result is overwhelmingly difficult to analyze, even for computers. It's safe to say that we would notice effects before the planets even got near each other. Perturbations of comets in the Oort Cloud would be evidence enough that something funky is going on. This would be hard to figure out at first, but eventually, we'd figure it out.
I'll use the [Hill sphere](https://en.wikipedia.org/wiki/Hill_sphere) approximation to make a really rough lower bound on the distance. For this, I'm assuming that the other star and Dyson sphere have a much greater mass than that of the Sun. Therefore, the radius of the Sun's Hill sphere is
$$r=a\sqrt[3]{\frac{m\_\odot}{3m\_{\text{star}}+3m\_{\text{sphere}}}}$$
where $a$ is the distance between the two bodies. Inverting this, we have
$$a=r\left(\frac{m\_\odot}{3m\_{\text{star}}+3m\_{\text{sphere}}}\right)^{-1/3}$$
Let's set $r$ to the minimum outer radius of the Oort Cloud, 50,000 AU. If we set the masses of the star and the Sun equal, and assume that [$m\_{\text{sphere}}\approx9.15\times10^{-5}m\_\odot$](https://en.wikipedia.org/wiki/Dyson_sphere#Dyson_shell), then we have
$$a\approx62,500\text{ AU}$$
This sets a lower bound on the distance the star would have to get to. The star would have to be relatively close to perturb these comets enough to start to attract them to itself. But we'd notice some fishy effects a bit sooner. Just how soon depends on how good our detection methods are.
[Answer]
It depends on our technology and how long they've been out there.
## Our telescopes are getting good
No one who's answered so far considered [microlensing effects](https://www.smithsonianmag.com/air-space-magazine/ultimate-space-telescope-would-use-sun-lens-180962499/) from the stealth system, but it looks like that gives a detection range of around 550 AU - well within the Oort clouds mentioned in the two current Answers. [All-sky surveys](https://www.digitaltrends.com/space/roman-space-telescope-predictions/) of microlensing effects to pick up faint stars, wandering planets, and the like are [current research projects](https://www.osti.gov/pages/servlets/purl/1660505). If your stealth system comes within a few hundred AU while one of the all-sky microlensing surveys is active, it will be detected.
Similarly, the [James Webb Space Telescope](https://en.wikipedia.org/wiki/James_Webb_Space_Telescope) is really good at seeing in infrared - the region of the spectrum which would be hardest to hide a star with current understanding of physics. To decrease the surface temperature of your stealthed star, you'd want to increase the radius of the Dyson sphere - probably to also enclose the habitable planets as well, but that means a larger patch of sky would be anomalously warm - even though it wouldn't be as warm as if there were no sphere. JWST is able to distinguish planets' temperatures from background for many nearby stars, and able to resolve the distances between the planets and their host stars - so the thermal signature from a Dyson sphere might be detectable out to tens of light years. The weakness of JWST is that it's not made to do rapid all-sky surveys, so a fast-moving Dyson sphere or one which happens to be in a direction where JWST doesn't look would be able to pass unnoticed.
## How long is the stealth system in the vicinity of ours?
Comets kicked out of the Oort cloud could take centuries to fall close enough to the Sun for us to detect. If the stealthed system is [just passing by](https://www.science.org/content/article/can-suns-siblings-be-found), we might not notice any effect until the comet rate increases - and by then it might be very difficult to figure out the trajectory of the triggering mass.
...
If you want a "drive-by" interaction, you can probably pass within 1000 AU safely, provided your stealth system is moving very quickly compared to the sun's orbital speeds at that distance. There will be lots of disturbance in the Oort cloud, but if folks are invading / surveying Earth during the brief interaction, a Kardashev Type II ought to be able to get up close well before we notice the disturbance. If you want a hidden presence for thousands of years, you're going to have a hard time harding a star within 100 LY that won't be found by JWST, Roman, Hubble, or one of the big survey programs.
[Answer]
This answer is very short but as close as the middle of the Oort cloud
[](https://i.stack.imgur.com/hYUyq.jpg)
The only way we would notice it is aperiodic and missing comets.
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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.
I want to play with the idea of a sapient species evolving on a world where at least part of the world experiences a permanent day. The obvious way to doing this would be where part of the world faces the sun always and part of the world phases away, though I'm not limited to that approach so long as a reasonable portion of the world will always have day-light.
I would like to imagine a world as similar to earth as possible given this criteria; or to be more specific a world that applies the most similar evolutionary pressures that earth placed on evolving creatures; other then the obvious no-day part.
In reality I can't just say earth, but without a night. The physical world would be different. Most obvious the constant sunlight being absorbed all day would have an impact on temperature, to keep the world the same temperature the sun would have to have lower radiance or the worlds atmosphere less likely to trap heat. I think this would also encourage more severe weather patterns, particularly near the border between day and night?
Thus I'm wondering how close could a planet get to earth-like, or encouraging of earth-like creatures evolving, while having a permanent day? What are the most significant differences such a planet would have compared to earth, beyond the obvious day itself.
[Answer]
There isn't a lot of `hard science` for something like this, unfortunately. The nearest exoplanet to us is lightyears away. That said, I am an enthusiast of astronomy, so I definitely enjoyed doing some research.
**As Smoj points out in their answer**, *Tidal Locking* is the idea you're looking for. An exoplanet which is (likely) tidally locked that we have (possibly) discovered within the *Goldilocks zone* of its host star is [Gliese-581g](https://en.wikipedia.org/wiki/Gliese_581_g). If it had an atmosphere like Earth's, it would be in for a rough time - well over half of the planet would be very, *very* cold (remember, seasons on Earth are caused by our [23.4 degree tilt](https://en.wikipedia.org/wiki/Axial_tilt#Seasons), so sunlight would not effectively distribute close to the day/night border).
**However**, something interesting I found out when researching this is that with a thicker atmosphere (or even a thinner one containing appropriate proportions of CO$\_2$ and H$\_2$O, and likely less N$\_2$), a planet *may* be able to effectively distribute heat from its lit side to its dark side [via longitudinal winds](http://www.sciencedirect.com/science/article/pii/S0019103597957936).
There would indeed be severe winds and ocean currents (not necessarily water oceans), which could make the evolution of life difficult, but hey, "life finds a way".
Your sapient species likely could not be one that evolved on Earth, as if they visited this planet with large amounts of CO$\_2$ they would be subject to [Hypercapnia](https://en.wikipedia.org/wiki/Hypercapnia) (CO$\_2$ poisoning). If your species evolved on this fictional planet and then traveled to Earth, they would likely suffer from *Hypo*capnia, or a lack of CO$\_2$.
**From Jay's answer:**
>
> Anyway, if multiple stars were close enough that a planet would receive daylight-level sun from several of them, would such a system be stable? I'm sure someone's worked out the physics of that to say if it's possible.
>
>
>
[](https://i.stack.imgur.com/pLV6P.gif)
Someone has worked out the physics - in fact, Binary and Trinary star systems are incredibly common! The closest star system to us, [Alpha Centauri](https://en.wikipedia.org/wiki/Alpha_Centauri) (4.37ly), is a binary system of Alpha Centauri A, Alpha Centauri B, with a third star Proxima Centauri just hanging out in the outskirts. There has been some evidence to indicate the system may harbor at least one exoplanet, but nothing conclusive.
There is also this [game](http://www.stefanom.org/spc/) that allows you to (attempt) to build a stable solar system with all sorts of objects.
I mentioned that game because you'll quickly find it's incredible difficult to make a solar system where an exoplanet is in a stable orbit with two other stars, such that it lies between the host star and the orbit of another star around the host star - and I'm not aware of any real world examples found to date.
**To answer your initial question:**
>
> What are the most significant differences such a planet would have compared to earth, beyond the obvious day itself.
>
>
>
From my research, I'd say, more than anything else, the **atmosphere**. It would need the correct ratio of greenhouse gases, and the correct density, in order to allow heat to propagate about all sides of the planet.
[Answer]
I don't claim to be expert in the science involved here. (But then, there really is no true "science" here, as we don't have any examples of such a world available to study. There can only be speculation and extrapolation based on science.)
Assuming one side of the world always faces the sun and the other side always faces away:
Most plants as we know them could not survive on the night side, as they would never get sunlight to power photosynthesis. That would make it tough for animals to live either, as they wouldn't have plants to eat to make a foundation for the food chain. Presumably animals living near the boundary could travel back and forth.
Presumably the day side would get much hotter than the night side. But if the night side is mostly dead anyway, that's not much of a direct problem from a world-building point of view: You just posit distance from the sun, atmospheric composition et al sufficient to make the day side a reasonable temperature for life. Then the dark side is very cold. How much colder depends on thickness of the atmosphere, weather patters, whether there are moons, etc.
The hotter day side would mean that air gets heated and expands, and then must move toward the dark side where it cools. Of course air can't continually flow from light to dark so there must be currents bringing it back. In short, I think you have some pretty constant high winds.
Similarly with ocean currents. I think the surface will tend to be moving dark-ward while there's an undercurrent flowing light-ward.
If the people basically live on the light side, the dark side is a barren, unknown, mysterious land. In early days a few brave souls probably venture there. As technology advances eventually they reach the point where they can launch serious expeditions and truly colonize the place.
Another scenario may be for the planet to be in a system with multiple suns, so that all or most of the surface is getting light from at least one of the suns at any given time.
(Isaac Asimov wrote a story about such a world many years ago called "Nightfall", where it is only night for one day every thousand years or some such, and when that day comes people go insane. It was a well-written, entertaining story, but it seemed to me to have a lot of plot holes. Like, given the whole multiple-star premise, any particular spot on the planet might have night only on these rare occasions, when it happens that given the dynamics of the system, that part of the planet is facing away from all the stars, and/or they are eclipsed by moons. But the whole planet wouldn't go dark at the same time, it would be one piece here, one piece there. So even if we accepted that the darkness drives people insane, it wouldn't be the whole planet at once, just part of it, so it's not clear why civilization would collapse. And why would darkness drive people insane? Even if it's never night, people don't normally go insane because they experience a previously unknown natural phenomenon. I didn't go insane the first time I saw a tornado. And even without night, don't people on this planet have caves, windowless basements, shipping boxes, etc, that they would experience darkness now and then? Oh well, whatever.)
Anyway, if multiple stars were close enough that a planet would receive daylight-level sun from several of them, would such a system be stable? I'm sure someone's worked out the physics of that to say if it's possible.
[Answer]
An example, at least in terms of the mechanics involved, is the moon. [Tidal locking](https://en.wikipedia.org/wiki/Tidal_locking) explains this.
If you looked at Earth as a star instead of a planet, the moon would always have one side heated, and the other side cooled, as it has one side facing and the other side facing away at all times during its orbit. A night and a day side, with a temperature gradient from one to the other.
For an Earth-like planet orbiting a Sol-like sun, the nature of the day/night hemispheres of the planet would depend on how far away it was from the sun.
The closer it is to the sun, the larger the heated day side would be, and through atmospheric convection forces, the hotter the night side would be too.
At a Goldilocks distance away from the sun (not too hot, not too cold, just right), you'd end up with a band around the planet as a tangent to the orbit, separating the two hemispheres.
The temperature within this band could be suitable for life. The hemisphere closer to the sun would be too hot, cooling as it approaches the band. The hemisphere away from the sun would be too cold.
So you'd have a permanent day side which is within the temperature gradient suitable for life, and part of a night side which is also suitable for life.
[Hugh Howey](https://en.wikipedia.org/wiki/Hugh_Howey#The_Bern_Saga) in one of his Molly Fyde books (The Bern Saga series) has a scenario much like this.
Half of the world is scorched, the other half frozen. With habitation in a narrow band.
Actually, from memory the world in the story had two suns. But the principle would work with only one sun.
[Answer]
Explore this. Chris Wayan does an excellent job of exploring what the parameters of a tidally-locked earthlike planet with permanent day/night sides would look like. He takes an imaginative, entertaining and reasonable approach. Hope you find this informative!
<http://www.worlddreambank.org/L/LIB.HTM>
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[Question]
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Set in 2100 CE a group of scientists and engineers developed a working time machine that can send group of people into the past and back reliably and safely.
**Specifications as follow:**
* Can accommodate up to 10 passengers at a time.
* Time travel back into past in an instant and with great accuracy and precision.
* Time travelers are allowed to wander freely independently anywhere while in that timeline.
* Time travelers can observe any historic event unfold live.
* Even if multiverse exists, the machine is only capable of going back into the same timeline each time regardless how god throws any amount of dices.
**Limitations as follow:**
* Cannot travel any faster into the future than it is already doing.
* Cannot travel more than 100 years into the past.
* Each visit into the past lasts 10 minutes before being forced to return back to original timeline.
* All time travelers become 5th dimensional entities during the visit, any attempts to interact with history guarantee disappointment.
* Each trip cost a fortune unless the Government provides subsidy.
* No image or video recording device is allowed.
**Assumptions as follow:**
* This concept/device works flawlessly every single time.
* No man or animal is harmed in the making of this post.
**Questions**
1. What good reason would the government have to ***not*** cease and confiscate the time machine program which can allow public to see the real history and instead pour flows of cash into it?
2. Government security agency can be notified earlier of potential terrorism act or any tell tale sign of crime about to happen, privacy is virtually non-existence so what will become of our present day society?
3. What possible abuse of time travel into the past can cripples present day stock market on a global scale?
[Answer]
**Propaganda**
This machine shows the truth, and everybody know it. However, it only shows a ten-minute slice of the truth and that can be a very misleading. It is also limited to a small area, which can also be very misleading. The government knows this.
So, the government invites selected historians to witness carefully selected parts of history. These publicly trusted historians then publishes descriptions of what they saw. And thereby the public thinks they have been told the truth.
As the years go by, I can also imagine the government staging ten-minute "plays" just so they can later go back and watch them with their selected witnesses. Maybe multiple different plays if they aren't sure of which will be needed later on.
**Intelligence**
It was not clear if you could send these expeditions to any part of Earth or not. If you can, Intelligence will indeed be drooling. If you are limited to were you can place a time machine today + ten minutes walk, not so interesting. There will certainly be uses for this, but in most cases there will be cheaper ways.
**Privacy**
Privacy is already non-existent with today's surveillance technology, but society seems pretty unchanged by it.
Both for ordinary surveillance and the new time surveillance, the only defense is to seem uninteresting. As a terrorist you have to make sure to look utterly normal until it is time to spring the bomb. To late to do anything afterwards.
Imagine compressing your time line just a little, so that they could study the events leading up to Sept 11, 2001 without being rushed.
Where and when would you look? Trying to backtrack the terrorists one ten-minute slot at a time would be hideously expensive before you got anywhere interesting.
Lesser criminals would know that they are not worth the machine's time.
[Answer]
Stig Hemmer answered parts one and two pretty well, so I'll just talk about part three.
The mere fact that this technology exists would cripple the stock market.
See, you would have to effectively ban anyone rich enough to fund their own trip from trading, because that's the only way to protect against outside insider trading. There would be nothing stopping, say, Bill Gates from going back a few hours to listen in on a private executive meeting at Google so that he knows what they're doing -- and can then trade accordingly. Imagine if someone knew that Apple was going to release the iPod a week before it was announced publicly. They'd probably buy a lot of Apple stock and get stupid rich off of it, which would then allow them to fund another trip, which would get them stupid rich, which would allow them... Get the picture? Only now imagine that everyone who could do it was doing it.
Average people couldn't do it, true, but over time that would cause resentment. Soon the stock market would be seen as a plaything of the uber-rich, designed to make them richer with 100% accuracy while keeping the average people poor and guessing at what will perform well.
**This will happen whether the rich use time travel to manipulate the stock market or not.**
The knowledge that the rich *could be* using this technology to make themselves richer at the expense of the lower and middle classes will be enough to ruin trust in the stock market. It wouldn't be long before people start pulling their money out en masse, ultimately causing another recession or even a second Great Depression.
Which, coming back full circle, could cause the government to fund it, to show the public that they're monitoring it and not allowing this sort of misuse.
[Answer]
So that they don't make the mistake again. I think that governments often want to do the right thing rather than serve a self serving agenda. Showing what happened in the past could prevent things from happening in the future.
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[Question]
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Follow up question to: [How long time would it take for a space hulk to lose orbit?](https://worldbuilding.stackexchange.com/questions/28839/how-long-time-would-it-take-for-a-space-hulk-to-lose-orbit)
Let's assume that [the spaceship crashes](http://wh40k.lexicanum.com/wiki/Tempest_Frigate) into the planet, I used the [Impact Calculator to get some result of the crash.](http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=200&distanceUnits=1&diam=400&diameterUnits=1&pdens=25&pdens_select=0&vel=11&velocityUnits=1&theta=30&wdepth=&wdepthUnits=1&tdens=2500)
>
> **Your Inputs:**
>
>
> * Distance from Impact: 200.00 km ( = 124.00 miles )
> * Projectile diameter: 400.00 meters ( = 1310.00 feet )
> * Projectile Density: 25 kg/m3
> * Impact Velocity: 11.00 km per second ( = 6.83 miles per second
> )
> * Impact Angle: 30 degrees Target Density: 2500 kg/m3 Target Type:
> Sedimentary Rock
>
>
> **Energy:**
>
>
> * Energy before atmospheric entry: 5.07 x 1016 Joules = 12.1 MegaTons TNT
> * The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 3.3 x 103 years
> Major Global Changes:
> * The Earth is not strongly disturbed by the impact and loses negligible mass.
> * The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
> * The impact does not shift the Earth's orbit noticeably.
>
>
> **Atmospheric Entry:**
>
>
> * The projectile begins to breakup at an altitude of 104000 meters = 342000 ft
> * The projectile bursts into a cloud of fragments at an altitude of 18900 meters = 61900 ft
> * The residual velocity of the projectile fragments after the burst is 0.0382 km/s = 0.0237 miles/s
> * The energy of the airburst is 5.07 x 1016 Joules = 12.1 MegaTons.
> * No crater is formed, although large fragments may strike the surface.
> Air Blast:
>
>
> **What does this mean?**
>
>
> * The air blast will arrive approximately 10.1 minutes after impact.
> * Peak Overpressure: 528 Pa = 0.00528 bars = 0.0749 psi
> * Max wind velocity: 1.24 m/s = 2.78 mph
> * Sound Intensity: 54 dB (Loud as heavy traffic)
>
>
>
Would it be right to assume that the calculations are correct in this matter or do the somewhat aerodynamic shape, or other features change this?
I'm looking for the effects on the planet, not the spaceship, that if the calculations are correct - evaporate before it hits the ground.
[Answer]
The aerodynamics matter hugely in this scenario, as does the material of the ship and it's properties.
For example: If you put the numbers in for the Apollo capsule, but assume it's made of rock, it never reaches the surface.
The biggest question here is whether or not your ship was designed for atmospheric re-entry or not. If it was, then it will probably have a shape that lends it well to entering the atmosphere shielding down. I'm making assumptions about your ship design here, it could be that it expects to use active thrust to make sure it's shielding down, but I'd design a ship to self-orient. That shielding will probably be capable of absorbing the brunt of the atmospheric impact. If the shielding is uncompromised by whatever process led to it being a derelict in the first place the ship will survive re-entry intact. At this point you have a massive kinetic impactor, which will hit the ground in one piece and will cause one heck of a crater.
If the ship isn't designed to withstand re-entry, then it's possible it might break up sooner or later. It depends on the manufacture and stresses put on the vehicle. If it has significant stress points (joins between sections etc) and little internal bracing then it will come apart sooner. If it's been designed for rigorous high G burns and is reinforced to the gills then it will have to experience a bit more burn before fragmenting. If it's covered in easy to burn off sensor blisters/guns they'll burn off and cause weak points, if it's a sleek outer hull all shiny and chrome then it might last a little longer. It's really a question of design.
Looking at the Tempest: I'd assume it would break up. It's not designed for uncontrolled re-entry, its covered in weak points (gothic architecture does not good re-entry shielding make) and it's not exactly aerodynamic.
On the other hand: There's a lot of 40K canon about imperial warships ramming... ooh... *everything*. So it might make it all the way to the ground.
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Working from the facts I can see from your links on the spacecraft it has no chance at all of entering the atmosphere in one piece without power. From the illustration <http://wh40k.lexicanum.com/wiki/Tempest_Frigate:-> The armored prow will immediately initiate a pitch "down" tumbling the ship into a top or bottom exposure to re-entry pressures. All of the bits sticking out will break off but not before tumbling the ship more leading to a catastrophic break up of the hull.
The lighter sections will either burn up or impact without any real impact to the planet.
The worry is the heavy dense bits within the ship. Bits of armor, reactors and shielding, heavy pressure tanks etc. These can reach the ground as has been evidenced from deorbiting earth satellites. See <http://news.nationalgeographic.com/news/2011/09/110909-nasa-space-debris-uars-satellite-top-five-science/> . You are going to get a "shotgun" blast of these producing small impact events scattered over a wide area. Total impact to the planet as a whole, about zero. However you would not want to be standing where one of these bits hit.
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It's absurdly low density & thus terminal velocity, coupled with the fact that it isn't ice only held together by convenience, but rather incredibly tough and built for battles that involve using relativistic weaponry and ramming space orks...
It would certainly go into a spin(though not likely nose down, a more dense object might go nose down, but here the thermal effect from the leading edge and the widened nature of the prow would create lift in the forward section), which could potentially (stupidly enough) increase it's chances of surviving orbital entry (at least until splashdown) because of the increased drag (slowing it down) and the dispersion of heat across the entire body.
That is, until we consider shearing forces, which the calculator doesn't deal with.
I have to question the mass, I don't think johnson was too worried about it tho.
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So, imperial college's calculator assumes the object is an asteroid which it's not.
For the purposes of the calculator.
So first we approximate the volume of the ship, it's pretty much just a cuboid, getting fancy with the spires and stuff is :S
Then we cut a cross section to derive an approximation of 'diameter' for the calculator, for whatever it does with it, and to determine density(combined with the provided mass) and with those we find it's terminal velocity.(it's not under power, it's a hulk)
I just left the angle of attack as I found it.. I guess I should check that link of yours to see if there was any retained momentum and direction.
We don't need to shift the surface density at the point of impact because..well, it could be anything.
1.5km depth, approx 200m w & 200m h (the max beam is listed at .4km at the grossest point, 200m is a total guess to the average.)
The mass is listed at 6.1mt (or 6100000000kg)
Which gives us a density of 101.6666kg/m3
I used a drag coefficient of 1.5, arbitrarily.
So we have a impact speed of 1.62246 km/s
I'm well aware that this is entirely different to what I posted as a link earlier, and have no idea why (except probably I was disgusted with such a low density.)
<https://impact.ese.ic.ac.uk/ImpactEarth/cgi-bin/crater.cgi?dist=10&diam=300&pdens=101&pdens_select=0&vel=1.6224&theta=30&tdens=2500&tdens_select=0>
But I'm not sure it makes a material difference to the answer, because the results of the calculator presume that it is a natural body that formed, essentially, out of convenience, whilst the Imperium invested the power of magitech into forming fabulously strong synthetic compounds.
This ships has an accel rating of what, 41m/s2, which of course doesn't mean it's hull or internals can survive terminal velocity even without an impact at the end.
Problem with that are it's nature as an object of war that survives impacts from relativistic objects of significant dimensions and continues fighting. Judging it's ability to remain intact is all but impossible without a rulebook assertion, drawing analogs from armor/hitpoints whatever the system uses.
If we assume it survives to the surface due to magitech(which I would, throwing synthetic materials is not the same as throwing clay) the total energy release is similar anyway, and the scatter of debris can just be more earth thrown into the air instead of more ship.
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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.
A good summary of the Zerg race is given on wikipedia as follows:
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> The Zerg are a collective consciousness of a variety of different races assimilated into the Zerg genome. The Zerg were originally commanded by the Zerg Overmind, a manifestation of this hive mind, and under the Overmind's control the Zerg strove for genetic perfection by assimilating the favorable traits of other species.After a species has been assimilated into the Swarm, it is mutated towards a different function within its hierarchy, from being a hive worker to a warrior strain
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In other words, if the zerg see some biological feature they like, they assimilate the creatures that possess that feature to evolve into more adaptable creatures.
Furthermore, the starcraft wiki goes into some details about the Zerg's genetic structure:
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> zerg genetic material consists of DNA, seemingly in the shape of a double helix. However, when a zerg strain's DNA evolves, it becomes less flexible.
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The question is, given what we know about biology and evolution thus far, would it be possible for such a race of aliens to exist in the real universe?
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The first part is definitely possible- humans can already artificially modify the genomes of living organisms to do pretty much whatever we want. One of the means we use to do this, in fact, is retroviruses, which I suppose technically **are** the zerg if you wanted to loosen the definition a bit; they inject their DNA into living organisms' genomes, and those organisms produce copies of the virus.
Then there's bacterial conjugation; bacteria directly swapping sections of genome. It's one of the ways genetic traits manage to proliferate between bacteria.
Now, whether the "hivemind" thing would work depends on the precise mechanism of hivemind communication. Faster-than-light? Very unlikely. Not actually theoretically impossible (just locally impossible), because wormholes and black holes, but (as far as we know at the moment) the living organisms would need to be slingshotting their radio signals around orbiting black holes with relatively precise trajectories, or they'd need to be somehow producing enormous amounts of exotic matter / negative energy. Staggering quantities. Suns' worth.
However, if they just coordinated thoughts with massless particle transmitters-receivers (like your TV remote) while still maintaining separate brains and coordinating multiple thought processes (like a distributed operating system), that'd work just fine. In a very real sense, your brain is itself a hivemind, because all of the cells which comprise it could survive separately from each other in the right medium. Even the organelles within those cells (cf. mitochondria) can maintain a degree of autonomy under the right conditions.
I have no idea what they mean by the DNA becoming "less flexible", so I can't really comment on that.
Also, full disclosure, I'm not a geneticist or physicist.
So, if any of you are, and feel I've misrepresented something, feel free to call me out on that / edit and correct.
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I think there is an animal that is kinda similar to that. The ants, Zerg tend to be like a colony and the queen (which can be the overmind) can tell them what to do. Also, specific ants do specifics things. For example: Honey Pot Ants recolect food and then provided to other ants; Worker make the colony bigger; Warrior Ants fight to protect the colony, etc... Which is how Zergs work (I play SC2).
However, the only way to assimilate another living attribute doesn't really exist. I mean, there may be some viruses or bacteria that can do that or something similar, but not an animal or plant. The only way to change the genetic of a living thing is manually, and by that I mean artificially modify their genes.
EDIT: I just found this website where it shows how Ant and Zergs are similar <http://thwacke.com/2012/10/heart-of-the-swarm-insects-may-have-had-the-zerg-figured-out-before-blizzard-did/>
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Some pioneering humans get stranded on a planet which has exactly the same conditions as the earth in the Triassic period. They decide to stay and build a society/colony from scratch with the available resources of the planet. How will they go about doing it in terms
1. Food
2. Fuel and Resources (There should be no petroleum, and fuel wood must be hard to come by. Isn't it?)
3. Shelter and Protection against natural hazards
Also, how would the environment bring about changes in the humans?
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1) If it moves and isn't toxic, it's lunch. Dino eggs are excellent food and start damaging the number of local nuisances. Young dinos are also vulnerable unless they can outrun and out-think humans (as in not fall for dead-fall and pit traps). There's also shellfish, besides fish, and maybe large insects.
It ain't pretty, but the best way to get digestible green stuff may be out of dino stomachs, where they have been so good as to pre-digest it for humans. It's how many carnivores get their vitamins. (Fermentation tanks -- brilliant suggestion.) They need to look at edible fungi, lichen, and sea plants.
Considering Wikipedia info as a refresher ...
"On land, the holdover plants included the lycophytes, the dominant cycads, ginkgophyta (represented in modern times by *Ginkgo biloba*) and glossopterids. The spermatophytes, or seed plants came to dominate the terrestrial flora: in the northern hemisphere, conifers flourished. Glossopteris (a seed fern) was the dominant southern hemisphere tree during the Early Triassic period."
This means you have all the spermatophytes for possible food, conifers for a bitter tea with vitamin C in lean times (normally, you get all you need from eating fresh meat, fish, shellfish, eggs, &c), and you eat tender little fern sprouts (you can buy canned fiddlehead ferns if you want to taste some).
Humans don't need grasses/grains to have a regular starch supply. In Southern California and Arcadia in Greece, acorns provided an annual harvest. Manioc was grown in South America for its tubers (you know it as tapioca). So the spermatophytes may supply some large harvests.
2) If you want them to land where there's no petroleum, so be it. You're God. But if this is the Triassic, then there must have already have been a Carboniferous, so there's petroleum. They would just have to find it. Unless of course you're a Velikovskyite on where petroleum comes from.
Peat bogs. This is what becomes coal eventually. Look into peat as fuel. Kept the Irish warm for thousands of years.
When they first land, the most immediate local fuel is dried herbivore dung. Look into the use of buffalo chips on the Great Plains.
Coal. Don't see why there wouldn't be any.
Why no firewood? You have conifers. Early pine trees! Junipers! Freakin' sequoias! Cycads have burnable masts, as ginkos have usable trunks.
Which brings us to 3. Building teepees of long trunks, like lodgepole pines, and hides. Big enough dino, you don't have to do much sewing. If I were them, I would be looking for a butte that has to be climbed, with a spring, clear it of most native life, and settle up there. They're not primitives: they know farming. They can domesticate what they like. I can also see them living like Anasazi, but walling off their fields with stone across valley mouths.
They might treat herbivorous quadrupeds like elephants: catch them, use them at least for baggage and draft, feeding and confining them, then when they get too large, release them (or eat them). Archive.org has a pile of late 19th C books on elephant use that may help you imagine their use.
Cynodonts may actually be better choices as permanent domesticated animals.
Stone, wood, and leaves are available for buildings and thatched roofs. Hell, *dirt* is. I don't just mean adobe: there's rammed earth housing or stuff like pisé. See *[Cottage building in cob, pisé, chalk & clay](https://archive.org/details/cottagebuildingi00willrich)*. These work in almost any climate, including wet cold Northern Europe. Then there's log cabins, especially double-walled ones in the French style used in Canada.
I also have to note you have "pioneering humans get stranded on a planet" which means they were already set to build a society out of nothing. They will have training to get along without high tech (or they may come from an immoderately stupid culture that thinks nothing can ever go wrong, in which case I don't bet on this lasting twenty years). Where's their farming supplies, including seeds? They won't have much that requires petroleum, unless the first job on landing is to dig oil wells and build refineries. They will have to set up early to produce their own metals.
I would recommend you look at the Foxfire books for how to smelt ores, build wooden turbine water wheels, dry fruits, make soap, and a whole lot else.
If this is a result of a crash, they probably lost all the animals they were carrying as embryos, so you can eliminate that, but having human survivors and absolutely none of the seeds make it through seems implausible, unless the humans got out in the lifeboats while the main ship went confetti. But for pioneers likely to land on an uninhabited planet -- again, I would expect some supplies aboard lifeboats, not just food and water but tools and seeds.
Your 4, "Also, how would the change in the environment bring about the change in the humans?" makes the rash assumption environment *would* bring about changes. Since modern humans haven't much evolved physically for 15,000 years, I don't see anything radical here. They're going to have to handle only 80% of the oxygen they're used to, and a lot more CO2, but I don't think there's going to be any more difference than with, say, Tibetans or Quechua adapting to the high mountains. The landing generation will miss their normal atmosphere, but the children won't know anything else. They'll probably favor developing more red blood cells for oxygen delivery. Of course, without a pharmaceuticals industry there's going to be a premium on a healthy immunosystem and strong teeth for a long time.
Now, throughout this I've gone along with biological determinism as if this *were* the Triassic reformed.
I would like to say that if biological determinism isn't what you're doing ... More realistically, the possibility of compatible proteins developing on two planets is close to zero, especially in complex life. Odds are, humans stranded on alien planets will have to sterilize their area and terraform it, at least as far as plants and food animals go, or die.
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Conditions? Like temperature and weather? There is no telling what life will exist and its usefulness to us, other than oxygen producing photosynthesis.
If you mean like time travel so that they have to deal with the life forms that existed in the Triassic:
Have: fish, meat
Have Not: fruit, cereal
Need more research: other vegetables. Plants were "low grade" food so digestible stems and leaves would be hard to come by. *maybe* roots? Look up the lineage of various options and see if they existed back then. A clue is that anything that blooms is *not*.
What plants that do exist are far from the domesticated food crops. Perhaps necessary vitamins are not available: no citrus fruit to keep the scurvy away. No brown rice, ...
They could build vats to act in the same way as a sauropod's stomach, a more extreme form of modern cow's stomachs. Ferment the plant material to break up the indigestible woody parts and somehow process that into something nutritious to us. Maybe cultivate micro-organism like fungi to then eat.
The people might end up as obligate carnivores with hard-to-produce supplements to get enough essential substances.
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I got this from a book called *The Lost World* by Arthur Conan Doyle.
Because most hostile creatures from that time period were pretty large, you could live in caves with entrances just large enough to fit a human.
You could get food by setting up traps that are essentially hidden pits with spikes in the middle. This would be enough to catch some of the more soft-scales animals.
Also, it would not be too hard to figure out what plants are edible by observing what herbivorous dinosaurs eat.
Edit: The only immediate change I could see this bringing about in humans is improving their dexterity - they would still occasionally have to run away from someone. Also, in the long term, it might bring about adaptations that allow humans to eat a greater variety of plants and animals from that time period.
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Suppose I have world, which is flat, meaning that there are edges on the side you could fall off into space, but it is actually still quite thick, thick enough to have Morias, underground castles, hellscapes and deep chasms.
Do note that the world is not the Earth, it is a fantasy world, with magic. The world is also in the center of the universe, with anything that is not the world in "orbit" around it.
I say "orbit", as the sun, moon, stars and other planets were all placed there by some great divine power of yore. The only requirement I would have for the celestial bodies would be that they do move, and in a constant orbit-like way, but completely disregarding gravity wells, and one planetary body does not affect the path and orbit of any other planetary body. This means that there could be large planets in orbits that would not be physically possible in our universe.
Another thing to note is that the sun can be of any size, brightness and distance, as there can be a hand-waved magical atmosphere that regulates the temperature of the world.
What would the orbits of the sun and the moon be like, for the world to::
* Have a day-night cycle? Do note that I would like an Earth-like day-night cycle, with the day beginning earlier in the east, stretching to the west, so that east is always seemingly "ahead" in the day.
* Have a season cycle?
* Be able to see the stars and the moon at night?
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The trickiest part about having time zones on a diskworld is explaining why the light doesn't just spread across the whole disk as soon as the sun peeks above the horizon.
Extreme refraction of the light in the atmosphere (or at least in the bubble which keeps the atmosphere on the disk and even many levels of refraction from multiple layers in the atmosphere) could explain this - the light hits the world edge-on and the direction of travel sharply bends diskward. The edge closest to sunrise gets sunlight right away, but the sun has to get high enough for the angles to work out. This would imply the potential for the poles (ends of the axis perpendicular to the sun's path) to be forever dark, as the sunlight might not get that far out, and the night will always be a little longer than the day.
The moon would have to glow with its own light, as the disk will block the sunlight from reflecting off of it at night. This is ok, because it is a magical glow, thus justifying the fantasy concept that moonlight has special powers different than sunlight. Phases of the moon will be trickier - a crescent shape isn't likely, so you could go with an always full moon, but I like the other suggestion for a spinning disk-shaped moon for phases (even get 2 different sides of moon to play with).
Seasons depend on what you mean by seasons - different parts of the planet have different kinds of seasons. The arctic has periods of no sun and periods of no dark, equatorial regions have wet-dry seasons, etc.
Options for temperate warm/cold seasons could be the sun rotating its path - rises in the 'north' at the beginning of the 'year' (very arbitrary notions which could be completely different depending on which culture on the disk you are in), slowly migrating clockwise throughout the 360 degree/day year. The sunrise/sunset areas are warmed by the proximity of the sun, while the bits halfway around the edge are colder (the rock of the disk over there hasn't been heated in a while). The hub wouldn't experience any seasonal changes though, so either always winter (never gets close to the sun) or always comfortable (always gets maximum sunlight), depending on your preference.
Alternately the orbit could expand/shrink - the wider the orbit, the less the warming effect of the sun. This would change the length of the days so probably not a good solution - not like the real world where there is a tradeoff between day and night, but both getting longer/shorter together.
This next one is going to be a little tricky, so bear with me.
Gravity - I'm assuming it just magically pulls 'down', else the edges of the disk would be like climbing a cliff as you are pulled toward the center of mass. This has implications for the atmosphere and any oceans (sail off the edge?), as where does the stuff go that falls off the edge?
If we imagine the center of the disk being a hole to the other side, it could be a font returning all the air and water. The air return is usually just air, but the water accumulates on the 'bottom' of the disk until it reaches a critical level of buildup, at which point it overflows and 'spills' through the hole to be ejected on the inhabited side (like a geyser of mist into the upper atmosphere).
This air could be cold, bringing winter snows, or it could be hot, bringing the rainy season of monsoons.
This would also imply the wind is always blowing out of the hub, but you could go with a whole smattering of different vents which are active at different times (changes the wind directions, and allows for different areas to have different seasons).
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**Day and night**
This one is actually really easy. Simply have the sun orbit the Earth. If you think of the Earth as a small surface (rather than a big one), it's easy to see that solar movement would be just as intuitive as you would like it to be.
**Seasonal cycle**
We need to put some wobble into the orbit of the sun. Seasons come because the sunlight comes in at more of a glancing angle. Wobbling north or south would work to create a winter. Summer would be when the sun was dead center.
**Be able to see the stars and moon at night**
Stars are easy, they will just work. Its up to you if you want them to rotate or not... you could just fix them in place.
The moon could be done with just another intuitive 1 month orbit. The one detail is that the moon would not rise and set every night. It would just hang in space. You could have it rotate opposite the sun, but then it wouldn't have phases (because it would always be lit from the front).
If you want both phases and rising and setting, my advice would be to apply a little ironic world construction, and make a "flat moon" which rotates about its axis to create a phase-like effect, and rotates around the planet directly opposite the sun.
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So, how about something like this?
[*Source*](http://www.zazzle.com/flat_square_and_stationary_earth_poster-228391247680679327)
In order to have seasons you can have the orbiting sun and moon move slowly back and forth along the world. Imagine the sun moving into and out of the page over a year's time. The increase in distance from the far edge of the disc would create a winter there, while the decrease in distance from the near side will create summer.
The stars and galaxies can just be stuck out far away from all of it as a backdrop.
Very simple.
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Let's say that I have two places with the same climate and the same geography and everything. The only difference is that one civilization is nomadic and the other has settled cities on the land and practice agriculture.
It is a medieval or renaissance era.
**How many people are living in the sedentary territory compared to the nomadic territory?**
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And are both areas filled to capacity with humans? Do they have draft animals to pull farm equipment and carts of produce? There are many factors to consider.
As a rough estimate, take a roughly self-sufficient island population in modern times but with relatively primitive agriculture. Say Flores, in Indonesia.
Mind that this has pretty much optimal climate for agriculture but is mountainous, so you're limited to what crops you can grow.
The sea also provides a lot of food in the form of fish.
Population, roughly 2 million. Area, roughly 20.000 square kilometers. That leaves you with 100 people per square kilometer.
Flores of course has some industry, but it's by and large an agricultural society outside of the cities.
Compare that with central Kalimantan (Borneo) which has more of a hunter/gatherer society in general (though certainly not exclusively) combined with a similar climate.
It has a surface area of 150.000 square kilometers with a roughly similar population of about 2 million, for 0.75 persons per square kilometer.
I don't know if the land could support more people, but the difference is striking.
Even were Borneo to support 10 times as many people, it's still have a population density 10 times lower than the agricultural/industrial society on Flores.
These are of course rough estimates only. Flores has a net excess of food (iow, it exports food) and its population is mostly restricted by available land. Being an island in a very rich sea, it has a large amount of sea food all around, the area of Borneo described is land locked on 75% of its borders (though it has rivers and lakes).
But it's a starting point. Similar climate, roughly similar geography, 1% the population density for the nomadic/hunter gatherer society as compared to the industrial/agricultural one.
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I would say that, on average, a nomadic society would have a lower population density. After all, by definition, they wander about (well, perhaps "wander" isn't the best term). The point, though, is that nomads take advantage of natural resources - open land, for instance. For example, [Mongolian](http://en.wikipedia.org/wiki/Mongolia) nomads used open land to graze their horses. [Plains Indians](http://en.wikipedia.org/wiki/Plains_Indians) (if you'll pardon the phrase) often followed herds of buffalo. But when the buffalo weren't there, they weren't there. And when the grass in a certain region wasn't good, the Mongolia herders weren't there.
In a "settled-down" society, however, things would be different. People would take all the land they could get, for farming. Also, cities would spring up - greatly increasing the population density. You wouldn't see cities in nomadic societies!
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Here you are: you are building your world, have come with a nice looking map for it, and now you are asking yourself if that map is realistic or if there is something you have overlooked.
And you want to ask us on Worldbuilding to help you with that. Here below are some of the points you need to check.
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**Tectonics and volcanoes**
The total surface of a planet doesn't change because of plate tectonics. Therefore surface creation at divergent borders and surface destruction at convergent borders must balance.
Volcanoes can exist on both types of border: divergent borders tend to give more fluid lava and eruptions (see Iceland), while convergent borders tend to give more viscous lava and more explosive eruptions (Japanese, Indonesian volcanoes, for example).
Hot spots, like Hawaii, can exist in the middle of plates, just ensure that their migration on the plate is coherent with the shift of the plate over time.
**Mountains and rivers**
Tectonic plate boundaries decide where mountains are.. Rivers can have snow or glacier contributions, the origin of many rivers will be in the mountains. Rivers may also originate from places on the map with a lot of rainfall.
At the mouth of a river, variations in flow conditions can cause a river to drop sediment it is carrying. This sediment deposition can generate deltas, and sometimes islands. When there is no delta, a river mouth could become very broad before it reaches the sea, or consist of a narrow fjord, with mountains on either side.
**Oceanic currents**
Drawing up ocean currents is fortunately not that hard, as they follow some straightforward rules, but [this example](https://www.cartographersguild.com/attachment.php?attachmentid=97136&d=1498925035) of Earth's currents will likely be useful. For this, you're mostly going to be using latitude lines, so make sure your map has those on it.
You start with two currents flowing westward near the equator (around 5N/5S). Whenever those currents hit a major landmass, they will be deflected north or south as appropriate towards the poles. They will generally go more or less straight at first, but at around 35-45N/S they will be deflected eastward by wind patterns; if they run into a landmass jutting out before then (see India), they will bend sooner. Follow them eastward on that latitude line (around 45N/S generally) until they hit land; generally, the current will split at that point into north and south currents (one going to the equator, the other heading to the relevant pole). There will be polar currents as well, flowing eastward at around the 60N/S lines.
The general rule with ocean currents is that they should always make closed patterns, typically circles; if you have a current that just stops at land with nothing continuing it, you've probably made a mistake. You might have to draw in some additional currents to have it make sense. Currents tend to run in force only through deep water; a continental shelf (which tends to be shallow for ocean water) might as well be the continent proper.
It's important to separate the currents by type (warm, neutral, and cold) for the later steps of making a world map, since these types have different impacts on local climates. Basically, currents heading towards the poles are warm, while currents heading back to the equator are cold, and everything else is neutral. It's entirely plausible to have a warm current at 70N/S (see the coast of Norway) and a cold current at 10N/S (see western Africa). A quick tip: the western coast of a continent tends to have a cold current when between 10-45N/S, but a warm current from 45-60N/S (reverse this for the eastern coast).
**Wind patterns**
To do an accurate map for an Earth-like planet, you will require separate maps for winter and summer for this stage. I'm going to refer to this as northern summer and northern winter, because the southern hemisphere will be in opposite seasons, but you can call them the hot and cold seasons or whatever else suits you. This is necessary because air temperature has a significant impact on these matters.
*Part One*: Air pressure systems. You can't make a useful diagram of the prevailing winds until you know where they're coming from, and that means knowing what areas will have higher or lower air pressure.
You need to chart the ITCZ line first. This is near the tropics and is a consistent low-pressure zone, but it does move slightly over the seasons. Draw a line at about 10N/S (whichever hemisphere is in summer) across the ocean eastward until you hit land. Your line is going to get pulled slightly towards the pole by continents, most noticeably on the eastern coast, but not too far; the strength of the effect depends on the landmass, and if the ITCZ hits the 20N/S line, either you've made a mistake or your map has something with the general size and placement of Asia. If you go past the tropic lines (23.5N/S), that's a problem unless you have a giant Pangaea in one hemisphere. Note that this assumes an axial tilt equal to Earth (23.5 degrees); adjust the axial tilt, and the suggested latitudes for the ITCZ will need to shift appropriately.
High-pressure systems are likely to form over the sea at around 30N/S in winter, generally on the eastern side of an ocean (near the western coast of a continent); in summer, move them to 35N/S. Overland, you only get high-pressure zones in winter; as a rule, a larger continent means higher pressure and a larger high-pressure zone (Asia has a monstrous zone in January). Smaller islands are effectively negligible in this section; overland refers to large continents, so something like Hawaii or Iceland has no meaningful impact.
Low-pressure systems in oceans tend to form around 55N/S in winter, and at 60-65N/S in summer; these will span most of the ocean at the relevant latitudes. Overland, they only form in summer; draw them mostly closer to the eastern coast, and once again a larger landmass reflects a larger low-pressure zone.
*Part Two*: Wind patterns.
Usually, wind currents flow from high to low-pressure zones, subject to the interference of mountain ranges and the like. They flow in a clockwise direction out of high-pressure zones in the south, but a counter-clockwise direction out of northern high-pressure areas: [this diagram](https://www.cartographersguild.com/attachment.php?attachmentid=76626&d=1444248370) might be helpful. Low-pressure zones reverse this; northern zones generally have winds entering in a clockwise fashion, or counter-clockwise in the southern hemisphere.
High pressure zones will blow winds out in all directions, so you're going to be drawing lots and lots of arrows. Anything going towards the poles (>45N/S) will quickly shift direction eastward due to the westerlies. Winds blowing towards the equator will gradually be blown westward as they move towards the equator; these are the trade winds. For obvious reasons, mountain ranges will tend to block or divert winds blown into them.
Low pressure zones (including the ITCZ) will act like magnets, drawing in nearby winds, but it's quite possible to have wind passing between high and low pressure zones without entering either one if the rotation mentioned above results in the correct direction; if both zones are sending winds in the same direction, winds in between will likely be following that same direction instead of moving into the low pressure zone. This can also happen if you end up with a mountain range blocking the way, like the Andes.
Also make sure to draw the winds (following the clockwise or counter-clockwise rotation as appropriate) even inside the high/low pressure zones. These winds will be weak, however, if the zones are of significant size.
**Temperature**
This is a tough one. As with many other steps, you're going to need separate maps for summer and winter, as unless your world has no axial tilt, there's obviously going to be a big difference between January and June. Make sure your diagrams of ocean currents and winds and so on are on hand, since you'll be referring to them frequently.
First, map out some key influences. Ocean currents (warm/neutral/cold, as noted in that section) and continental influence are the relevant ones here; if necessary, get an extra pair of maps to track these. The current influences are coastal, and affected to some degree by wind; if your wind map has air blowing over the appropriate current type onto land, draw the relevant influence a little further into the land. Continental influence tends to fall under high pressure zones in winter, or low pressure zones in the summer; if you have something like Asia, expect its continental influence to be exaggerated near the center. Also, any ice pack situations (see northern Canada and Russia) will be continental as well, since the water moisture isn't really accessible.
For the temperature guides, I'm relying on these images (source is from [this excellent tutorial](https://www.cartographersguild.com/showthread.php?t=27782)):
[](https://i.stack.imgur.com/zoXyP.png)
[](https://i.stack.imgur.com/wQTN6.png)
The latitude guides are a general pointer for temperatures at a given latitude, assuming sea level; temperatures will drop roughly 6C for every 1000m of elevation, so mountains will be significantly colder. The last image is a color guide relating the colors in the latitude guides to the appropriate temperature ranges. Continental plus, essentially, is to be used in a central-Asia type of area, so it's not relevant unless you have large continents with probable ice-packs blocking the north or south.
Be warned that these guides aren't exact (climates being by nature rather inexact when trying to apply what amounts to educated guesswork), so there's a fair bit of fudging involved. Coastal areas tend to have milder temperatures (warmer in winter, cooler in summer), but this doesn't typically apply to inland seas or ice-pack conditions. If you're using the extreme edges of the scale (dark red or purple) in more than very small areas, you'll probably want to do another draft; applied to Earth, this method maps the greatest heat only to small parts of Africa and Australia, whereas the nastiest cold is only in Antarctica or Siberia, or perhaps something like Everest.
*A warning here for complex worlds*: this assume Earth-like conditions. Changing the axial tilt, the solar constant (essentially the relation between average orbital distance and the sun's luminosity), orbital eccentricity, albedo, and so on will have a serious impact on the latitude guide. Adjusting the latitude guide to match changes in these parameters is probably a matter of educated speculation, but I'll try to give a few pointers. Changing the axial tilt will have a greater impact at higher latitudes; a larger tilt translates to greater extremes in temperatures. If solar luminosity or orbital distance changes, that will affect your planet's average temperature.
A non-trivially eccentric orbit (I would think e <= 0.03 would be trivial, but that's just my opinion) poses particular difficulties, since orbital distance will not remain effectively fixed. This obviously will affect temperatures and probably require you to make separate latitude guides for the north and south hemispheres as well as for the seasons; you'll also need to place perihelion and aphelion in relation to the seasons. The likely result is doubling the number of diagrams you'll have to make, as the guidelines around summer and winter will be different for each hemisphere.
**Precipitation**
This one is possibly the single ugliest topic (being the most subject to estimation and interpretation), so you should expect to do multiple drafts before you get this right. This is essentially going to be painting a lot of influences, and then estimating total precipitation based on how many overlap at any given area.
Make very sure you pay attention to wind direction; a lot of these factors change drastically if wind is blowing onto shore versus being parallel to it or from land out to the ocean (the former scenario results in more precipitation, while the last one likely means none). Note that a mountain range will, under most circumstances, block any significant rainfall on the other side unless precipitation can come from both sides. Also, inland seas will generally not offer significant material for precipitation, although unusual circumstances might come up; North America's Great Lakes, for instance, have occasionally been the source of truly alarming blizzards.
Start with the ITCZ line; check your wind map if you don't remember what this is. This one is a huge influence, because it draws any winds coming from the equator and more besides: it effectively is worth double any of the other influences. It's not quite a guarantee of massive rainfall, it must be noted: the Sahara sits under the ITCZ for half the year, yet it's a desert; to my understanding, this is because the Sahara is too hot for any moisture to really precipitate, no matter how much evaporated from the Mediterranean. Still, this is where the great majority of tropical rainforest is going to turn up. Paint a reasonably thick line (around 10 degrees of latitude) over the ITCZ, and expect a lot of rainfall over this area unless you get a mountain range or something like that in the way.
Next come some effects from westerlies. This starts at around 30N/S in winter (moving poleward), or around 45N/S in summer, and is mostly present on western coasts. You'll get a fairly strong effect on the coast, but it quickly weakens. Winds can carry the effect a long ways inland if blowing in the correct direction, but rainfall will diminish over distance; for any map with an Asia-like continent, it's likely to end up with a desert near the center.
Storm paths are another influence. These are mostly on eastern coasts from 25-50N/S, and are found west of high pressure centers over oceans. These bring a lot of precipitation several degrees of longitude inland if the winds blow directly onshore and still quite a bit even farther inland, but like other influences this one diminishes with distance. As the name suggests, you may want to note these areas as being storm-prone; the best examples of this on Earth are the eastern coast of the U.S.A and the Caribbean, with the hurricanes that so often roll through.
Orographic lift, also known as rain shadow, is another crucial point to take note of. If rain-filled winds get blown onto mountains, the clouds will rise. As they rise, they get colder, and the moisture condenses and falls out of the sky: when they descend on the other side, they warm up again, so any moisture left is unlikely to precipitate. The end result is a lot of rain on one side of the high ground but very little on the other. This is what gets you temperate rainforests like southwestern Canada has, and it's also why plateaus like Iran will generally be dry. The greater the elevation change, the stronger the effect; a mountain range will be more significant than a plateau.
It is crucial to note that ocean currents may play a role here. If you have a cold current near a high pressure zone, any winds blowing onshore over cold currents are very unlikely to lead to precipitation, even if orographic lift would normally occur. This leads to areas like northwestern Africa, which has almost no actual precipitation.
As a general rule, precipitation drops as you move towards the poles; high pressure zones also tend to have reduced precipitation, due to winds rushing out of them instead of into them. Temperatures are notable for certain cases: if you have a sudden rise in temperature, you probably won't get much precipitation. Winds blowing from polar regions are likewise improbable bets for any real precipitation.
**Climate zones**
This is what you're ultimately working for, if you've gone through all the previous steps, and it's almost anticlimactic that the final step is actually one of the easiest. Take your temperature and precipitation maps (there should be four in all, since you need summer/winter maps for both) and correlate the data at given regions to find your climates; I would recommend the [Koppen climates](https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification) for classification.
I don't think it necessary to spell out all of those climates in detail here, but be warned that your precipitation map is only an approximation and should be used as such; think of precipitation in terms of low, moderate, high, extreme, etc., rather than in exact measurements. If you've got a tropical region that's drenched in one season and bone-dry in the next, for instance, you probably have a savannah climate (Aw or As). If you're not reaching at least moderate precipitation in either summer or winter, you have steppes or a desert (the B-range climates). Coastal regions outside the tropics will almost always be temperate (the C climates) unless you're in the polar regions, as the ocean is a powerful moderating influence on temperatures. Regular snowfall does not automatically mean a continental climate (the D climates), since cold days happen even if the monthly average is above 0C, but lingering snow that sticks around for a few months is another matter.
**Cities location**
tbd
**Story-dependent information**
* Other information on a map will depend on your story. If there are political angles, there will be some boundaries involved, like country borders.. resources.. and in case of a war: front lines, army strongholds, castles, fleet base.
* A tip.. since februari 2022, there is a guide website for fictional maps online, with directions and lots of tips and software tools <https://rocketexpansion.com/fantasy-world-building-maps/>
[Answer]
Just going to chime in on this.
Your world will seem realistic enough if you just get a globe and look for actual land and corresponding weather on the real Earth, and then copy it. If you want island settings, look for chains of islands, and understand what formed them.
If you want a tornado alley, copy Oklahoma. Find your livable soaring mountains, look to the Rockies or Andes.
If you want deserts, look in the American southwest, the Sahara, and elsewhere.
A black sand beach, you can find it in Hawaii. Vast forests, there are several rain forests available.
All natural world examples are based on Earth; you can pretty much cut and paste the elements together, if you include their transition-to-something-else areas, and be good enough.
99.99% of readers are not climatologists, they aren't going to lose immersion in your story because for plot purposes you put the rain forest on the wrong side of the mountain. They won't even notice.
Just copy some answers from the real world and you'll have done more than most authors.
I needed an imposing cliff for a story, I just googled "tallest cliffs" and found [Biggest Cliffs In the World](https://topbiggest.com/biggest-cliffs-in-the-world/). I checked out the conditions, my story was indeed shore-adjacent, I picked a mile-high cliff and transplanted it to my shore. Were the wind and currents and soil and rock composition right for that? Beats me, I did not mention them; it was just a sheer cliff of a few thousand feet I needed for dramatic purposes.
World building can be a fun game and hobby in it's own right, but it isn't 'writing'. The world, consisting of nature and culture, is there to be an antagonist or an ally to your heroes and villains; to provide conflict or advantage for either one.
If what you want to do is write, then build the world as you build your plot, considering it an antagonist, or an ally, or (not too often) a neutral element for your characters. Like any character, always consider the nature and culture of a scene; the world has a role to play here too.
In my opinion, the time spent world building for the fun of world building is not time spent writing. I cut and paste my world elements from the real world, and build my world to suit my specific plot, not as a canvas for a dozen stories. If I have done a decent job, I am able to build more plots that fit into it, and perhaps make some use of the less specific areas of my map.
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[Question]
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A long time ago in my world, a people, who lived alone in a continent-sized island away from any significant other landmass, had a schism. Half of them departed in a fleet with numerous ships into the unknown sea.
They eventually found other big islands in the horizon, some made home, but the majority continued on the endless trek. At some time, they built a gigantic ship of wood and sails (and magic surely) to float endlessly.
By gigantic proportions i am thinking some kilometers in width and lenght. Buildings built on deck, parks with growing trees, farms, and ports with a small fleet of common sized ships to embark on short expeditions.
In this world minor magic is particularly common (protection amulets, healing remedies), while flashy and fantastical feats are rare, but known of. I think some hundred magic-knowers, a dozen mages and only one true (and old) wizard per 10.000 people is a good measure. One extra thing is that magic is always connected to art (poetry, painting, dance, music, etc.)
Is it's construction plausible, considering a technology level of maybe late medieval china and surely the help of magic? Would they be able to sustain a good and healthy life only seafaring? Will societal life have any incredible problems?
[Answer]
# Some questions you need to consider:
### What can your magic do for the ship and its builders?
Does your magic make the ship stronger or more resistant to storm damage or easier to build?
### How big are the trees on your islands? How strong is the lumber? How plentiful / fast growing are these trees?
Bigger ships mean more lumber which means more/bigger forests. And that lumber must be stronger, unless magic is reinforcing the design (see 1st question). A 2 square kilometer ship would require tens of thousands of planks, which would be thousands of trees. How much forest do your builders have access to?
### Some assembly required
The larger the ship, the larger the shipyards. Sure, the ship floats. But it can't float while it's being constructed (again unless magic somehow suspends the structure during construction). From the first beam until the hull, at least, is complete, the structure needs to be dry-docked.
### Labor force?
The bigger the ship, the more people it will require for construction. Sure, your wizards can help, but unless magic is extremely powerful, it's not going to build the ship. At best, it's probably going to do things like lift heavy objects into place or provide mortars or act as power tools, not wish-level full assembly. So how many people will it require to build this ship?
How many people run the ship? You'll need full-time repair crews to manage anything that breaks, plus anyone who manages navigation, steering, and so on?
### Structural integrity
How is your ship held together? How do you prevent the ship from breaking under it's own weight? More magic?
### Movement
How does your ship move? Sails? How large a sail (and how strong a mast) would it take to move a multi-kilometer-sized ship? Would it just drift with the currents, then? How do you steer it? How do you not run into things and get stuck (coral reefs, islands, icebergs, wales....)
### Planning
Where in the evolution of your society did everyone stop moving and devote all their resources to building this thing? How did they come up with the design plan that would conquer the various engineering challenges it faces, and then divide their labor between resource gathering, the many construction specialties, and the support roles like medical, food, and so forth? And who trained the engineers and construction specializations for this monumental task?
## Maintenance and Defense
How do you get to parts of the massive vessel that need repairs while it's under way? How do you replace broken timbers -- or even become aware of them -- when it's so large? If a fire broke out, how would it be contained? How does the ship defend itself from outsiders (pirates, invaders, etc.)?
# A possible alternative:
Rather than hand-wave all of the above problems with "Magic! [insert glitter here]" have you thought about using a flotilla instead?
If, rather than one giant ship, you have hundreds of smaller ships, all lashed together, then you solve most of the problems I raise above.
* The entire flotilla could have grown organically over time as new ships were built or acquired, and then added to the flotilla. No need for a genius master plan up front!
* The resources to build the flotilla wouldn't have to be gathered all at once, but could be gathered over years or even generations.
* If a storm is on the horizon, the flotilla can separate into mini-flotillas or into individual ships, making survival of the whole far easier and safer -- the loss of any ship won't risk the entire structure.
* It's far easier to navigate a smaller ship than a larger one. If the flotilla needs to steer around an island, a shallow sea, or whatever, then they simply break apart, each sails under its own power, then reform once past the blockage.
* It's much easier to build a small boat that floats than to build a massive floating city or mini-continent. Fewer resources, easier engineering, safer for workers. Faster, too.
* Defense from attack or fire is easier: unlash the ships and spread out. If the pirates attack a ship, then other ships break free of the flotilla and surround the pirates. Suddenly the pirate ship becomes part of the flotilla and the pirates... well.. that's their problem.
* Fire? immediately unlash from the burning ship and spread out until the flames are under control or the burning ship sinks. *Safety first!*
* Magic isn't as necessary to make it work. But it still helps! Your mages can be useful for gathering sufficient food, for reinforcing the links, for gathering materials, for navigation, etc. etc.
* Each ship is a family home. Each has it's own character -- custom paint jobs, decorations, designs... Each ship tells a story, just like homes do. Entire regions of your flotilla may have similar designs as they were formed at roughly the same time, but travel a few dozen ships away and the designs might be completely unique. Personally, I think that makes a more interesting storytelling framework than 1 giant ship. Picturing this big conglomerate of mismatched ships, all tied together into one giant community? I can see that in my mind, the whole undulating with the waves. But 1 super-ship? That's much harder to picture as a thing that could exist. (Pure opinion, here)
* Not as susceptible to storm damage. One big thing can break under the strain of rough seas like during a hurricane. But a a flotilla of smaller ships can ride out storms, for the most part. Sure, a bad hurricane might cause some losses, but not catastrophic losses to the entire flotilla.
* History. In general, human-occupied locations grow over time. There's history as people expand a city and as technology changes. Very rarely does an entire kilometer-wide area just spring forth, fully planned in advance. The flotilla concept easily accommodates the way historical cities grew from small towns into the chaotic maze of streets and buildings and parks that the residents know and love.
* Food gathering is more readily handled, since the outermost layer of ships can all be fishing vessels that break away during the day to set out nets, then come back. The flotilla becomes their harbor, so to speak, rather than trying to feed the entire civilization from the deck of a single ship.
* Harbors can be used without special treatment. A massive ship simply can never approach land. But smaller ships can break free of the flotilla, come to harbors/ports to trade or collect supplies and then return without any special effort. The flotilla stays at sea, but traders can move freely between flotilla and shore as needed.
[Answer]
**The ship is nearly uninhabited.**
A colony ship designed for thousands now hosts a population of a few dozen. Large areas of the ship are unvisited by the main characters and what goes on there is unknown. Magic tenders (I am thinking of the robots in Castle in the Sky) keep the ship floating and moving. There is easily enough food for all inhabitants growing in the farms and gardens.
The ship at one time had weapons, smaller ships and many other features. Nearly all of this is unused by the current residents. The younger ones who were born on the ship know little about these other aspects of the ship, which can be discovered in the course of the story.
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Storywise this lets you sidestep big societal issues and instead concentrate on the adventure of a few characters. The fact that the boat is an ancient think and current users are more or less ignorant of its construction and maintenance lets you finesse all that as well. The boat is a fine place for an adventure and you can have adventures with the things they encounter, with the meta-story being your young characters wondering about their place in the world and if the boat is their only possible destiny.
[Answer]
## Use Live Wood
The thing about wooden ships is that once they get too big, large waves cause them to resonate and shatter. In general, wooden ships more than about 30m long can't survive rough seas. While some ships like the Chinese Treasure Junks or the Greek Tessarakonteres were much bigger than this, they could only safely leave port during calm weather, and had to be dry-docked to survive major storms... but that is because of how dead dry wood behaves. Live wood however can be very pliable.
Since you have magic, consider having your wizards magically grow a living massive colony of intertwined floating plants. So in your case, the the "ship" is in fact "made of wood" but because it is green wood, it will not shatter from resonating with rough seas. This also makes it self healing, much more resistant to burning, and easy to have start off small and grow over time which should address many of the concerns CaM brought up in his answer.
It could be that the original ship was the result of a spell just meant to make a living normal sized ship, but because it was alive, it continued to grow and spread out until reaching its present size.
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[Question]
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My world is as close as possible to contemporary real life under the constraint that orcas (and maybe other cetaceans) are significantly smarter than humans.
**What is smarts?**
We *define* it as *information processing that machines cannot in the near future do.* This precludes tasks humans need their dexterity and six senses for if said task could be within the range of our AI for a robot with similar "hardware". However, it gives a reasonable metric of what kinds of skills will be most needed (and thus most plot-driving) in an increasingly automated society.
**How the intelligence stays hidden (for a while):** Humans are *very interested* in orca and in general cetacean intelligence. *Human brains have over twice the neurons as elephant brains, but orcas have [twice the human level](https://en.wikipedia.org/wiki/List_of_animals_by_number_of_neurons)*. But curiosity is not enough.
Firstly, the aquatic behavior is hard to understand for landlubbers. Behavior would have subtle uses, and humans wouldn't have the "bigger picture" such as exact location of prey sonar echos, etc to understand what is going on. It's all too easy to see a cultural ritual that isn't your own and mistakenly think of it as primitive.
Secondly, in my world the language sandbags itself. Researchers manage to find some orca words that correlate to simple concepts, and from that it seems that most of the language must be similar. But it's the parts that *don't* get deciphered that are more complex and involved than even the [Navajo](https://www.huffpost.com/entry/learning-the-lingo-the-5-_b_997685#:%7E:text=Navajo%20%2D%20Not%20only%20is%20Navajo,during%20the%20Second%20World%20War.) language.
Thirdly, captive orcas get trained more slowly than humans because of this language barrier, not because of less intelligence, which could also mislead people into thinking that they aren't as smart.
Fourthly, humans conflate intelligence with technology. The lack of orca tech is due to the difficulties with the aqueous environment, lack of opposable thumbs (or suction cups or elephant trunks), and much smaller population sizes. Not brainpower.
Given these (human) difficulties, **how would humans "discover" and utilize this super-human intelligence?**
[Answer]
**Multiple Dimensions of Intelligence**
Humans are obviously superior to most animals in the kind of intelligence that concerns the manipulation of your environment with tools.
However, we have expanded beyond the concept of a one-dimensional IQ to terms like logical, interpersonal, or artistic intelligence. Maybe its just one of these facets where your cetaceans are clearly superior to humans - they could even have a language optimized for that purpose.
**Artistic Intelligence**
Your Cetaceans may follow a completely different purpose than the Humans in their collective drive for Exploration and Expansion. Maybe orcas are content with their place and numbers, and are more interested in passively examining and praising the beauty of their universe.
Their whole language and thinking is perfected towards communicating things they perceive as curious or beautiful to other members of their species. Every Orca is a natural Poet and in large groups, they weave intricate pictures of 3D sound and bubbles - vastly more complex than any Opera or Symphony.
**What did we miss?**
We typically just point a single microphone at a group of whales and just marvel at their singing, but we are missing the greater context. From the perspective of an 'audience' orca, passing through the soundscape created by the orca 'choir', they are transported to another place and receive an emotion-packed 3D picture of the northern Atlantic the day the Titanic sank. Or maybe of the heroic fight of the [Sperm Whale that sank the Essex](https://en.wikipedia.org/wiki/Essex_(whaleship))
**How did we find it?**
We actually have an Installation that might help finding these patterns. The [Antares Observatory](https://en.wikipedia.org/wiki/ANTARES_(telescope)) is a huge array of statically suspended aquatic probes. Though primarily used for astrophysical purposes, they are also equipped with microphones which from time to time pick up whale signals.
[](https://i.stack.imgur.com/9k0GF.jpg)
By coincidence, a group of orcas holds a conversation inside the array, and for the first time scientists get their hands on an expansive 3D dataset of the ocean space surrounding a chatting group of Whales. And with some clever data reduction, they find that the sounds and interference patterns are bafflingly close to the [ship formations of the battle of Trafalgar](https://en.wikipedia.org/wiki/Battle_of_Trafalgar#/media/File:Trafalgar_1200hr.svg).
**Now What?**
The parts of the language you already observed were just the tip of the iceberg. There is a set of very simple 'words' which are just flat 1-dimensional noises, used in a similar way to conjunctions and auxiliary verbs. Earlier your scientist just found those and thought they were done. But the part that actually carries the most meaning are those 3D-patterns which can be compared to our nouns and verbs - and may be as complex as a full playback of a thing the whale *heard/saw*.
Once we know where to look, we can start to take these sound-transmitted 3D-Pictures and play them back through a similar array of mics and speakers suspended below an exploration ship. As I already hinted, for things which are of common interest to humans and whales look for important events of naval history - those might be things that are preserved in the collective memory of both humans and whales, and a nice starting point for a conversation that could lead to a slow deciphering of more complex language constructs.
For the most obvious use - think about the implications for historians and ocean researchers. All those lost ships and planes just lie in their backyards. Secret nuclear submarines might not be that stealthy to an Orca. They can tell you where those 'rogue nations' dump their nuclear waste, and show you the way to undiscovered resource deposits.
[Answer]
**Alien cetaceans show up.**
[Star Trek IV: The Voyage Home](https://www.imdb.com/title/tt0092007/?ref_=fn_tt_tt_24)
>
> /To save Earth from an alien probe, Admiral James T. Kirk and his
> fugitive crew go back in time to San Francisco in 1986 to retrieve the
> only beings who can communicate with it: humpback whales./
>
>
>
In the movie, aliens show up looking for their whale kindred. Humans had wiped them out some time ago which poses problems. It has been 35 years. You can borrow from the finest of the original Star Trek movies. There is a scene with Dr McCoy meeting a lady in a hospital elevator that I still think of sometimes.
In your world aliens show up but there are still cetaceans doing their thing because we did not kill them all. Ignoring we landlubbers, the aliens enter communications with their primitive brethren and ... sistren? Hmm.
Anyway, kind of like when celebrities show up in your school and only want to talk to the quiet nerd whom no-one thought much of, humans realize there is more to our whales than we had realized. We approach the aliens with uncharacteristic tact and humility and ask to participate in the conversation.
[Answer]
This question is (unintentionally) fallacious.
If cetaceans were intelligent in your story, or even super-intelligent, what would it mean? You want a story where they've been secretly doing "intelligent things" (even if these things amount to little more than "intelligent thinking"), and humanity eventually realizes that it is so.
If there are no overt signs of technology (which, I add, could include signs that would be invisible to more primitive species), then we can conclude that the only mechanism by which humanity could discover their genius would be some magical science fiction tech that can peer into minds themselves.
I do not consider that technology to be implausible... we already have crude versions of it with medical imaging. We can see parts of a brain "light up", and we can sometimes decode what is happening in that brain. If we were to follow the projections of that technology into the future for a few decades/centuries, it might get to the point that would seem magical to you and me. Presumably, you could see inside the whale's brain (maybe even from a distance), and know exactly what's going on in their head. And with the proper software to translate it (developed and refined in tandem with the imaging), you could make sense of it.
Provided of course, it's not so far advanced that we simply can't understand it at all.
So, what is it that the whales have been up to all along? Were they calculating pi to a trillion digits? Working out the mass of the Higgs boson from first principles? You have to come up with something they've been doing that is both plausible and not woo-woo nonsense.
None of those things can be done by a whale. While the raw computational power might exist within their brains, there's no reason for them to develop thoughts along those lines. They serve no survival purpose, and so no evolutionary pressure exists to compel such. Furthermore, these things are impossible to work out from first principles. Humans only discovered chemistry and physics after banging rocks together and mixing reagents (mostly accidentally) for a long, long time.
Without such concepts, their language will be simple, not complex. You don't need a complicated language for a simple environment. You for instance, when's the last time you spontaneously coined 2,488 new words for variations on the idea of slippery? How about new conjugations for the verb *to slip*?
While this doesn't preclude them having language, it will be no more complex than that of non-human animals in general, or at most of being like the languages of our distant ancestors with limited vocabulary/complexity.
Thus we are limited to scenarios that match reality. Cetaceans are clever animals that can be taught some symbolic languages, and are clever compared to most other animals but not to humans.
I'm sorry, but your premise doesn't work, and I cannot see any minor adjustments to it that would make it work. There's just nothing to uncover here.
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Following the issues raised in the question [How to limit population growth in a utopia?](https://worldbuilding.stackexchange.com/q/190654/32451) I'd like to ask a related question. In a stable utopia, would the population be old-aged, compared to less-than-utopian societies?
I define "utopia" as a society where all traditional ills are kept at the minimum possible: hunger, poverty, diseases, substance abuse, violence, crime, wars etc. The society achieves that (somehow) without relying on magic or futuristic technology. Also, this utopia is stable - it occupies a fixed land, its use of non-renewable resources is negligible and its population size is fixed (somehow). There is no immigration or emigration in or out of the utopia.
After considering these conditions, it looks like average life expectancy (and consequently, the age) of utopian citizens should be higher than in any of the real world countries.
Thus, would the "real" utopia be a society more aged than any real world country?
[Answer]
### Yes. Your average age depends on life expectancy and is $L\over2$
For your society to have 0 growth, and everyone dies of old age, you need to have a child born every time someone dies of old age. This would lead to a perfectly flat population distribution.
If everyone lives to 100 due to your excellent medical system, at any time half the people will be under 50, half will be over 50. So the average will be exactly 50. It's half your life expectancy.
Japan's average age is [48](https://www.statista.com/statistics/604424/median-age-of-the-population-in-japan/#:%7E:text=The%20median%20age%20of%20the,behind%20the%20Principality%20of%20Monaco.), Australia's is 37. Your country would be the oldest average age.
However that 100 was chosen arbitrarily. If everyone dies at 60, your average age would be 30, but dying at 60 doesn't sound very utopian to me.
[Answer]
**Real world countries could be older, because they are not in population equilibrium.**
In your utopia, each woman would have two children, to replace herself and the father. Add in one extra child occasionally to account for circumstances where a child dies before reproducing.
In some first world countries that is not happening. On average, women have less than 2 children. Japan is an example.
<https://worldpopulationreview.com/countries/japan-population>
>
> The main cause of Japan’s population decline is the rapidly decreasing
> number of births, which is currently at the lowest it has been since
> data started being collected in 1899. In 2019, only 864,000 babies
> were born in Japan – 54,000 less than the number from 2018. The
> fertility rate in Japan is 1.4 births per woman – far below the
> population replacement of 2.1.
>
>
>
Your country would have lots of old people but percentagewise not as many as Japan - especially the predicted Japan for 2060.
[Answer]
**TL:DR: If the society were perfectly utopian and perfectly disciplined/controlled, yes there would be children and young people equally in proportion with very old people.**
A few assumptions are in order.
The fundamental assumption is that there is procreation. That is, there is a continual supply of babies. Otherwise, your question is moot - with no babies, either everyone stops aging at, say 30, and so everyoe in the population will be 30 years old, or the population will just keep getting older and older, with zero young people.
So, given procreation, the society may be utopian in the sense of health, but there still must be death at the end of life. Otherwise, the population keeps increasig to infinity. It is not a stable population, which violates one of your criteria.
Let's pick some arbitrary age, say 150, that everyone lives to, on average. More than likely, there will still be accidental deaths. No utopia can get around the zap/splat factor, there will always be lightning, for instance, or rocks falling from cliffs. But lets limit this to just a few exceptions here and there.
Given these conditions, for a stable population, there will not be a population pyramid, there will be a **population cylindar**. Every decade will have the same number of people. Say 100,000 from 0 to 9, 100,000 from 10 to 19, 100,000 from 20 to 29, 100,000 from 30 to 39, all the way up. A total stable population of 1,500,000. (feel free to scale the numbers by any factor to get the population size you want). It might tapper off towards the top, say 90,000 from 140 to 149, and then a steep drop-off. Perhaps 10,000 from 150 to 159. People stay perfectly healthy, until they aren't. Death comes suddenly, maybe in their sleep. They just don't wake up. All body systems shut down at once. No more telomeres, everything unravels. (As a bananas-cuckoo-crazzy side bar, google 'telomeres' and right at the top of the list, you will be pleased to know that you can buy them on ebay.)
If essentially everyone lives to reproduction age, say 30, then for a stable population each person can reproduce only one child. If the society is a binary split 50 males to 50 females, then one female can have two children - one for the mother, one for the father. If the people are asexual, then each person can have only one baby. This would be on average, of course, because some might decide to have no children, so their ration would have to be assigned to someone else.
Assuming 20 years from birth to maturity, then most people would spend only 20 years of their 150 raising a child. Perhaps 40, if they reproduced their two children (perfectly binary population) serially instead of in parallel. Perhaps 100 years would be spent either in child-free boredom, or bliss, who knows which. It does beg another question be asked, exactly what would be the puropse of living, if it was not reproducing? Would it become a completely hedonistic society? The up-side is that in a binary society the typical 140 year old would have two children, four grand children, eight great-grand children, and sixteen great-great grandchildren, given 30 years to a generation, if my math is correct. Note that there would be an initial population pyramid until the population stabilized into a cylindar, after one 150 year cycle. That is, the singular baby would go throug 150 years of children and grand children until they died at 150, then each person who died would roughly be replaced by one child who was born.
But exactly what would one DO, for the last 50 years, being able to plan how long they had left to live, almost to the year?
[Answer]
## No, a society cannot be stable without growth
No society can be stable without growth. An aged society is a ticking time bomb because a time will come when there's too few replacement workers in the queue, causing all kinds of problems when there's work to be done.
It's theoretically possible, but impossible from a practical perspective (due to random issues like disease, accident, etc. that brings about the need for redundancy) to have a society that's so balanced that the replacements exactly balance the aging. However, avoiding those random problems requires such high technology that you might as well invoke magic and simply keep everyone from aging at all.
From a very practical perspective, no matter how high your technology, entropy exists. Buildings, tools, and infrastructure ages requiring renewal that an older or aging population cannot perform efficiently (if at all). People need things to do to feel useful and satisfied (meaning new adults need jobs currently held by the older generations). Etc., Etc. What this means is that you always need growth. Perhaps not a lot of growth, but growth, nonetheless.
Which means your society cannot be aged. By definition, it cannot be a utopia unless it is preparing for the workload of future maintenance.
If you want some hard-core insight into the issue of stable societies, check out "[The Concept of a Stable Population](https://www.un.org/en/development/desa/population/publications/pdf/manuals/model/stablepopulation/chap1.pdf)" from the United Nations.
[Answer]
The answer varies along with the country's ethics. In *The Giver*, the elderly are usually sent to the House of the Old, which is basically a nursing home. The actual ages are not disclosed, but most of the elderly are treated as children, while the actual responsibilities are given to the presiding rulers. After the elderly become no longer useful, they are killed. In this sense, *The Giver* is a dystopian, authoritarian ruler. The elderly are not given a chance to continue living and contributing to society.
So it depends, yes there are aged people in the advanced society, but they are often removed or killed, making the average population middle-aged.
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[Question]
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Imagine a world very similar to Earth (and about the same distance from its star as we are to our star (it's the planet from my other [question](https://worldbuilding.stackexchange.com/questions/188699/what-traits-would-plants-have-if-no-animals-or-humans-existed)). But in another solar system (let's say in Alpha Centauri). How big would a space station in low orbit need to be to support three humans for about five years compared to the ISS?
* It needs sleeping rooms, a kitchen, at least three storage rooms, a small farm to grow easy crops (lettuce, carrots, etc), and an electricity room.
* It needs to hold fuel and lift fuel (after liftoff, it would primarily use solar power).
* It needs to hold a lander capable of bringing two people to the surface of the planet and back to the station.
* It needs to be able to hold water (or a way to get water (it can get water from the planet on its third year)).
* This can be in the future. Preferably as close to our present-day as possible.
* I'm willing to take some creative liberties.
* Partial answers are ok, as long as they add something to the information.
If you have any questions, please ask.
[Answer]
**Living Compartment:**
For this you can look at underground bunker floor plans to get an idea of what space limited people need. A floor plan similar to [this](https://www.ussaferoom.com/products/underground-bunker/10x30-bunker/) 10x30ft (600 sqft) bunker could easily accommodate a 2-3 person crew's living space needs.
**Life Support Needs:**
In general, any mission as short as 5 years is better off using stored food than trying to grow it. Growing food takes a LOT of power per person, uses up a lot of space, and needs a lot of specialized equipment that might malfunction before your mission is over. The average person needs about 2 kg of food per day, and food weighs an average of about 1g/cm^3; so, for a 2 person, 5 year mission you need 7300kg of stored food which has a volume of about 260 cubic feet. The average person consumes about an equal volume of other consumables to food (toilet paper, soap, cloths, etc) So you could actually cram your entire consumable needs into a storage space about 8x11x6ft; though, for organization reasons, assume you need walkspace to get to everything. So what you really need is a storage room that is about 200-300 sqft with a ceiling about 6-7ft high. For comparison to farming, you would need about 2000sqft per person to grow your own food during the mission even using stacked aeroponics; so, for a mission this short, just bring the non perishables.
Air and water recyclers are not that big for a two person crew. They'd fit into the flooring or walls of your habitat rather than needing a whole module. You'd probably need a few hundred gallons of water to cycle through and some extra air storage to compensate for any loss of atmosphere over time; so, assume maybe an extra 300-600cuft of space for some large tanks.
**Power Needs**
Since you are not growing food or running extensive scientific experiments (like ISS), your solar needs would not be anything extraordinary. However, you will need to know how far you are from Alpha Centauri you are. Assuming you are aiming for dead center of the goldilocks zone, you can assume similar energy density to getting solar in orbit of Earth. That said, Earth's atmosphere absorbs about 50% of light before it hits the ground and we can not maintain peak daylight for more than 5hrs per day; so, satellites can get a lot more power out of solar than we can on the ground. Infact, a 600cm^2 solar panel in space can produce enough power for a standard American Household. Obviously, in space you need a lot more power to run your recyclers and climate controls, but in total, you'd only need a few square meters worth of solar panels to run everything.
**Lander & Lift Fuel:**
The specs on this will have a LOT to do with the planet in question. Earth like worlds need HUGE rockets to get off of. The average Earth rocket needs 83-96% of its mass to be fuel; so, even small space stations need huge rockets. But a smaller world like the moon could use something like the [Apollo Lander](https://en.wikipedia.org/wiki/Apollo_Lunar_Module) which is more craft than fuel. See The [Tyranny of the Rocket Equation](https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html) to get a better grasp on how to figure this out for your situation.
**Conclusion:**
All-in-all, I'd assume your station only needs a pressurized volume of about 6000ft^3. This is ~5 times smaller than the [international space station](https://www.nasa.gov/feature/facts-and-figures); so, you could for simplicity just ignore everything I said and scale ISS down 5 fold.
Your lander may need some hand wavy fuel source if you are orbiting an Earth sized planet, Otherwise it will need to be bigger than your whole station to get to the ground and back.
Humans also don't do well in Zero-G for as long as 5 years; so, you'll need some manner of artificial gravity. Centripetal force is often used in Hard Sci-fi to simulate gravity, but this station is much too small for that to be practical without doing some very interesting engineering. In general, any spinning vessel that is too small will have significantly more simulated gravity at your feet than head which would is quite disorenting just in the short term. In the long term who knows what kind of health issues it could cause; so, again you may want to consider hand waving in some "gravity plating" or else your station will need to be very heavily engineered around solving the gravity issue.
[Answer]
### About the same size as the current ISS (915 cubic meters)
**Lets start with food**
It takes [6-8 weeks](https://www.saferbrand.com/articles/hydroponic-growth-rate#:%7E:text=When%20you%20put%20them%20in,in%20six%20to%20eight%20weeks.) to grow lettuce in hydroponics. One head of lettuce gives [120 calories](https://www.calorieking.com/au/en/foods/f/calories-in-vegetables-fresh-lettuce-cos-raw/uBnIIJMQTFSbKwz_G4uDzQ), which in useful energy units is 500kj. You need ~6600kj to keep your bodies critical systems running if you sleep/watch TV all day, ~9000kj a day for a mostly idle human moving around a bit and doing some light work, and 14,000 for an astronaut doing lots of complex tasks and exercising. Lets assume they're idle. You'll need to eat 18 lettuce heads a day. cycling through 1000 lettuces growing can feed 1 person full time, to feed 3 people nothing but lettuce you'll need 3000 lettuces growing in hydroponics.
I don't know exactly how tightly you can pack them in, heat and light sharing complicate this problem, but assuming 30cm x 30cm x 60cm of space is required for the plant and it's proportion of shared light, water, nutrient, and all support systems, that's 162 cubic metres for your farm.
**Bunks for 3 and 3 storage rooms**
The current ISS has room for 6. So turn 3 crew bunks into storage rooms. If you need really big storage modules use one of the extra lab modules.
**Kitchen and electricity room**
I don't know what you do in an electricity room, but it would have a counterpart on the ISS. There are basic food prep facilities on the ISS, basically a microwave and hot water source. However you can steal some space from a lab module for a nicer kitchen if needed.
**Manoeuvring**
The [Zvezda service module](https://en.wikipedia.org/wiki/Zvezda_(ISS_module)) has an engine for manoeuvring
**Lander**
Assuming there's no fuel depot on the ground, getting them back to the space station is going to be a nightmare without future-teching this. You'd basically have to keep a space shuttle (and external fuel tank, and 2 solid fuel boosters). Docked in orbit. The space consumed by the rocket on the station is the size of the docking door, so I'm going to exclude it. Handwave your fuel source and then dock it to the tiny door I've included.
**Water**
ISS is capable of perfect recycling of water. So you'd have a tank like they do (perhaps water in the walls to protect from radiation and act as an emergency water source).
[Answer]
I mean it just depends on what you are looking for. Or what the Station is suppose to do, besides keeping everyone alive.
**Food**
To make it simple, there is no point in investing into any kind of on Board food Production. The Avg American eats 900kg of Food each Year. So even with a very unhealty diet and a bit of extra on top of that, you would not even reach 3 Tons of Food. In terms of Space, thats like maybe one big Module worth of Space at worst. And again, 3000kg is more than you would need.
**Water**
Water too will be brought from the Planet and just Recycled. I would guess another Module worth of Space. Maybe a bit more or a shielded Backup or something.
**Rooms**
If you want to go all rich people, you give each person one Module worth of Space. It can be smaller though. In the end, that just depends on the Missions budget.
So all in all, we are at 5-6 Modules. The size of those also depends on the budget but something like 12 Meters long and a Radius of 4 Meters or so is probably more than enough.
Energy is another Module and then another one for the Lander. So plus 2. This sets us at 8-9 Modules. I would assume that Ventilation and Air recycling are in the same Module as the Water supply.
This leads us to conclude that such a Station would be rather small. Maybe 100 Meters long. Of course, this Station dosnt do anything funny. It just keeps people alive for 5 Years.
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[Question]
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I'm building an artificial growing environment for a heavily overpopulated world (because you can always build up, right?). When I started thinking about this, I thought it might be as simple as "calculate the energy output of the sun for the growing season of wheat...." But as I thought it through, I needed:
* Sunlight for photosynthesis
* Sunlight (or something else) for warmth
* Water distribution
* Air distribution and purification/recomposition (right % of chemicals, etc.)
* Fertilization and soil control
* All the equipment...
And probably a bunch of other things. That might make this question too ambiguous, but I'm giving it a shot. Asuming I have a big, future-tech fusion generator, how much energy does it take to grow an acre of wheat?
* I have the seeds and an acre of soil that needs no other treatment to plant the seeds - but they're not yet planted.
* Don't include the energy needs of the human staff (how much energy is needed to run a human for the season is outside the scope of this question). However, you can't use this limitation to justify not using machinery. In other words, you can't assume an army of scythe-wielding humans to replace the combine they'd actually use and the energy it needs, which is part of this question.
* I'm asking for energy because I'm assuming (for the sake of simplification) that I can reasonably convert everything to electric motors with better-than-average batteries and just recharge them off my fusion generator.
* The question does include harvest. The end result is a field full of wheat stubble.
* Processing the wheat *after* harvest isn't considered. In other words, once the kernels are in the hopper that part is over. Removing the bailed straw is part of the process, but once it's in off the field, that part is over, too.
* Edit: Hydroponics are ***not*** part of this question. I'm working on a much more complex agri-industrial complex than just growing wheat and I'm looking for the energy number to help design the infrastructure supporting it. I'm not interested in alternatives to an acre of soil — just the energy needed to grow the wheat.
*I recognize that I'm going to get a best-estimate because there are a thousand little details that would require a couple books to answer.*
[Answer]
Even before doing any research, I can tell you that all other power expenditures are pretty negligible compared to the the amount of energy required to produce the light that feeds the plants... but here are all the numbers anyway:
**Water distribution**
Water distribution is pretty cheap in terms of power because of how hydraulic systems work. If you have water to store in an elevated place, then every pipe attached to it will have water pressure no matter how far laterally it travels. If you build a dam that raises a reservoir above the level of your farms, then that means your water is absolutely free (in terms of energy to distribute.) Even if you need to pump the water <https://www.engineeringtoolbox.com/pumping-water-horsepower-d_753.html> show that a 1kw pump can life over 100 liters 15 meters per second. Wheat needs 100-125mm of rainfall a year. That is about 455 liters per year per acre; so, unless your farm is at the top of a highrise building, whole system could generally have it's entire annual water pumping needs meet off of the power stored by a AA battery.
**Robotics (aka Fertilization/soil control/all the equipment)**
Farming indoors requires a lot less of things like weeding, pest control, etc. While this is hard to find exact specs on, I'd imagine you probably are not using much more power than a laptop consumes simply because there is not really that much to do 99% of the time but have systems on standby waiting to scan something or controlling a few nozzle servos to start/stop watering. This is just a ballpark guess, but I would be surprised if you actually needed more than 4-5 kWh/day.
**Air Conditioning**
Air conditioning and filtration will vary a lot relative to your setup. In general, wheat prefers [70-80°F (21-27°C)](https://www.ehow.com/info_8583493_much-light-wheatgrass-need.html). If you are building in an archaeology located in a desert, this could take a lot more A/C to keep cool, but if you are in a cooler region where you design your vertical farm buildings to have a natural heat-sink shape, your AC could be practically passive. If you assume a home needs a 20 BTU/sqft AC running an average of 3 hours a day to maintain these temperatures during growing seasons where wheat is normally grown to offset the heat of the sun, then an acre of enclosed farmland should be fine with an 871,200 BTU HVAC system. That will make your HVAC system require about 261.36 kWh/day.
**Grow lights**
Cannabis and wheat have similar light requirements; so, your indoor farm will probably need about 40-50 watts worth of LED lighting per square foot to grow. That means your wheat will need a total of 1960.2 kW worth of lighting which will need to be on for an average of 14hrs a day to simulate grow season daylight time. That is a total of 31,363.2kWh/day.
**Harvesting**
My personal experience with my battery powered weed wacker is that a 2Ah 20v battery can take out about 100sqft of tall thick grass which would be comparable to the process of harvesting wheat. 2Ah @ 20v = 40Wh so a similar device used to harvest your whole field would consume about 17.4kWh per acre making this another negligible energy cost.
**Conclusion**
By maintaining ideal grow conditions, you should be able to grow about 37 bushels of wheat in about 6 months, which will yield a total of about 1550 pounds of flour after processing. This gives you a cost of about 5,756,600 kWh or 3814 kWh/lb of flour. Your civilization better have some pretty cheap power though or this flour is going to cost you hundreds of dollars a pound to grow.
Since you mentioned in comments that this is an archaeology the size of Connecticut, you have a total area per story of 3,548,427 acres which will meet the annual wheat consumption at current demand for about 30.5 million people per floor at a cost of 2.04e13 kWh per floor per 6 month growing cycle. This is about 10 times the United State's entire energy budget in 2019.
As a final suggestion: vertical farming is already horribly inefficient, and wheat is a particularly bad crop to do it with. If you need more room to grow your wheat it might be better to do it on barges taking advantage of all that unused flat space we call oceans, plus it makes use of an otherwise wasted part of our planet's thermal budget so that you aren't causing massive global warming by generating thermal energy at levels that are proportionally significantly compared to direct sunlight. There might also be some other creative scifi solutions like growing grains without the plants (sort of the same concept as growing meat without the animal) which could give you a wheat like GMO that could be 10s of times as efficient both per acre and per kWh.
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[Question]
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I just recently started my first proper worldbuilding project and I've encountered an issue. Most of the races in my world are pretty standard height, but some of them are pretty short or even very tall (average heights include 3-3’5 feet for one, 4’4-4’6 feet for another and 7’8-8’4 feet for another). In lore, flintlock muskets have been popular for a while by this point, although medieval-style melee and armor is equally popular because of the threat of magic, and because a fully armored knight with a musket is sick as hell. But the issue I've found is that smaller (and in lesser fact larger) races would need guns more similar to their size, which in the case of races like the Gnomes, would probably cripple their chances at fighting another race with larger weaponry, wouldn't it? I'm hoping I'm wrong, and a smaller musket would be just as effective as a bigger one, but if it would be less effective, do you all have any ideas for work arounds?
[Answer]
**Going Small**
36-40" is not tall, but their build and stature will make a huge difference. With a human stature, you are looking at the frame of a 4-5 year old child which would might just barely be able to shoulder a .44cal musket. Depending on the quality of gnomish muskets, the recoil would be expected to be somewhere between firing a modern .22 LR and a 9√ó19mm Parabellum round. These guns could still be effective against unarmored human at close range, but since we are talking muskets and not modern rifled weapons, you will not have the muzzle velocity to penetrate human plate armor. Instead these races will probably rely on anti-material rifle like weapons. Weapons much to large to fire when carried, but something they can set up on a bipod to shoot. Since most of the recoil would go into the ground, they could then handle a man killing firearm. In this case your Gnomes would lose mobility, but their smaller profiles would make them quite hard to shoot back at.
Also, being small means you can support a larger population off of the same resources. If Gnomes weigh 40lb and Giants weigh 400lb, then when two kingdoms of equal size and resources go to war, the Gnomes may likely have a 10:1 numerical advantage. So, even if a Gnome can't pierce the giant's armor, they may still be at a huge tactical advantage. If the Giant has a 50% chance of shooting first and is 100% accurate, he can fire at and kill 1 gnome per reload, in the same time the gnomes can reload, then the Gnomes will get an average of ($\sum\_{n=1}^{10}$ - 5) = 50 shots in per giant before being wiped out. Even against impenetrable plate armor, in an idealized situation like this, it seems likely that one of those shots would find an opening to exploit.
**Going Big**
Bigger races will generally have an easier time carrying enough firepower to punch through a smaller race's plate armor, but this comes at the disadvantage of being a bigger target. Also, being bigger does not necessarily give you a proportionally larger weapon. Because of the [square-cube law](https://en.wikipedia.org/wiki/), bigger animals are proportionally weaker than smaller animals. That said, 8'4" is still close enough to human sized that your giants would not exactly be frail.
Because being big may put you at a numerical disadvantage, larger humanoids may opt for fragmentation or shotgun type weapons instead of muskets when fighting smaller races. If a Gnome scale musket is a .44cal and can punch through Gnome armor, and a giant scale musket is 1.40cal, then a single grape shot could hold 21 balls able to penetrate Gnome plate armor with a proportionally similar round size. This might not clear out an entire formation of 10 Gnomes, but it might force them to spread out enough that they can no longer 1 vs many you.
**Strength variance by size is HUGE.**
All these factors assume your creatures are roughly human strength in scale, but many primates are proportionately much stronger than a human even without looking particularly strong. Chimps are not much bigger than your Gnomes, but 4 times as strong as an adult human, and Gorillas aren't just stronger than humans because they are bigger, they can lift anywhere from 4-27 times their own weight meaning your giants could conceivably carry full sized cannons on their shoulders. Because strength variance is such a manipulable factor, you can really adjust the strength of your bigger and smaller races to balance however you need it to for your setting.
Also, if your gnomes are just as strong as a full sized man, then the only difference between them and a man firing a musket will be ideal barrel length. The gnomes may want shorter barrels so they can get their hands under the weapon's center of gravity and load it more easily, or if this leads to accuracy/range issues they could opt for an over-the-shoulder breach-loader design and fire their muskets like an RPG.
Either way, you have some pretty extreme variables to work with so that you can balance these races in whatever fashion you deem most appropriate for your setting.
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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 am working on a new SciFi book and need your expertise to help nail-down mission profile, fuel use, acceleration, mass, etc. for my ships.
The books are Hard-Sci-Fi in the sense that everything should be possible, but the technology level is about 100 years into the future so I am not too worried about the details as long as I am not breaking any of the big-ticket laws of thermodynamics. e.g. we can assume meta-material gamma-ray reflectors, thermal-super conductors, and more.
The technology is based on micro-fusion torches, small (40x8cm) tubes which use stimulated gamma-ray emission from charged Hafnium slugs to initiate a fusion reaction.
[see Hafnium Controversy](https://en.wikipedia.org/wiki/Hafnium_controversy)
Magnetic confinement and meta-material 'magic' keeps things small. The torches generate electricity directly from the charged particles escaping the fusion reaction, and also by throttling the fusion torch and extracting kinetic energy from the main fusion 'flame' using magneto-electro-dynamic effects.
Four torches are arrayed as ignitors for the larger fusion engines in 'dagger skiffs' - smallish 4 person shuttle sized craft. (see crude diagram below). These 'skiffs' provide thrust for larger un-powered habitation and transport vessels.
That is the background. At the moment I need to work out some rough details, such maximum thrust for the "dagger skiffs" when not coupled to the habitat, max acceleration of the whole stack, fuel burn rate, power output, etc.
I am not a physicist or mathematician, so am finding it tricky to come up with the engineering.
I think I need to come up with some equations with realistic parameters for the technology I describe above. *e.g. one mission is moving a 150 ton (dry mass), 200 person habitation module from the Kuiper belt to Earth or Mars. The habitation module holds all the fuel, but the thrust would come from the dagger ships pushing it like tugs.*
acceleration = power/mass
power = fuel per sec / efficiency
Does this look right at all?
I would very much appreciate any physics hand-holding you guys can give.
Many thanks in advance.
Toby
[](https://i.stack.imgur.com/iQJtj.jpg)
[Answer]
Ship's characteristics:
* Powerplant : fusion
* Size : 35 m (length) x ~ 17.5 m (width) x ~ 10m (height)
* Fuel : offboard
* Desired Performance : deep interplanetary (kuiper belt)
Power per reaction:
* Deuterium ($^2H$) + Tritium ($^3H$) = Helium ($^4He$) + 3.5 MeV ([source](https://en.wikipedia.org/wiki/File:Deuterium-tritium_fusion.svg))
* Helium to Carbon ($^4\_2He + ^4\_2He \rightarrow ^{12}\_6C$) = 7.275 MeV (net; by way of Beryllium) ([source](https://en.wikipedia.org/wiki/Triple-alpha_process))
* Helium + Carbon to Oxygen = 7.162 MeV
Events per volume of material:
[](https://i.stack.imgur.com/qqt76.png)
Thinking that "100 years from now" technology could give you the best available $10^{-21}$ reactions per cubic meter, per second.
Let's say most of the ship (35 meters long, 17.5 meters wide, 10 meters high) is engine, and about nearly all of that is reaction vessel (which is a big assumption compared to today's technology).
Reaction vessel is $35 \times 17.5 \times 10$ = 6,125 cubic meters
Power generated is $3.5 MeV \times 10^{-21} \times 6,125 $ = $2.14 \times 10^{-16}$ MeV
That's not gonna work.
Assuming "100 years from now" technology can also give you better reaction rates. Since we're going bold, let's say 25% of $\dot{m}$ is reacting.
So, each gram of 50-50 Deuterium/Tritium mix (assuming hydrogen fuel) (avg. molar mass 2.5) contains ${1 \over {2.5}} \times 6.02 \times 10^{23}$ reagents, 25% of which react, and produce 3.5 MeV on each reaction (and assuming the energy imparted the fast neutrons is unrecoverable). 2.107 $\times 10^{23}$ MeV $\approx$ 3.3 $\times 10^{10}$ Joules of energy (33 gigajoules) per second. Or 33 GW. Scaling up to kilograms of reactants would give 33 TW.
Let's say the deductions of power to run accessories is negligible (but maybe it isn't). What's the $\dot{m}$ and $v\_e$ out the back? $3.3 \times 10^{13} = {1 \over 2} \times 1 \times v^2 \rightarrow 6.6 \times 10^{13} = v^2 \rightarrow v\_e = $ 8,124,038 meters per second (2.7% c)
$\dot{m}$ is 1 kilogram per second. The rocket equation (excluding nozzle effect) is $F = \dot{m} v\_e$
Thrust, therefore, is 8,124,038 Newtons (8.1 MN) per kilogram of fuel mix. That's in the same region as the 764 kN produced by space shuttle main engines.
What's the peak amount of fuel that can flow through the ship?
Say the fuel is stored in liquid form, and the fuel line can be no bigger than the ships' width (17.5 meters). And let's say it's circular. $A = \pi r^2 \approx 240$ square meters. The volume is equal to that area times the rate in which fuel is being brought aboard by the pumps. The density of liquid hydrogen is 70 kg per cubic meter.
Let's say 1 $m \over s$ for now, giving $\dot{m}\_{fuel} = 70 \times 240 = $ 16,800 kilograms per second.
Applying that to the thrust per engine : 16,800 $\times$ 8,124,038 Newtons $\approx$ 136 giganewtons.
You can go higher or lower on fuel flow rate. And select a different fuel. Or re-adjust down the huge "future technology" boost to reaction rate.
## Performance
The mass-energy efficiency of this set-up is the $E\_{extracted} \over {\dot{m} c^2}$. You only get 33 TJ per kilogram. That's a mass-energy efficiency of $3.6 \times 10^{-7}$ or 0.000036%
This is important for evaluation long-range performance (like interplanetary travel). To accelerate your load to a cruise velocity of 0.01c requires a mass-energy of $(0.01c)^2$, times the mass of your ship (or 0.0001 m in this scenario).
How much fuel mass your motor requires to confer this energy is taken by dividing the mass-energy requirement (0.0001 m) by your mass-energy efficiency (3.6 \times 10^{-7}) getting 277 kilograms of fuel mass required for every kg of payload (and does not include deceleration).
That's clearly not going to work. So, let's try a lower top speed: 0.001c ~ 2.7 kilograms per kg of payload.
Considering both acceleration and deceleration, then, for every kg of payload, you'll need 2.7 / (2.7 + 1) = 72% of your mass to be fuel. And another 72% of the residual to be fuel for deceleration, giving 72% + (72% x 0.28) = 92% of your payload mass will need to be fuel.
Maybe an even slower top speed. Let's try 0.0001c ~ 0.027 fuel/pay = ... most of your cargo capacity can be payload, instead of fuel.
What's that do to performance? 0.0001c is a cruise velocity of ~ 30,000 meters per second / 100,000 kilometers per hour. To travel a distance of 1 AU at this cruise speed (approx. 8 light-minutes) takes about 55 days.
## Thrust Performance
To push a 150 ton load (150,000 kg) with 4 ships each providing 8.1 MN of thrust up to a cruising velocity of 0.001c, you could get accelerations up to 216 $m \over {s^2}$ (or ~21 gees). Not sure you wouldn't want to limit to only a few gees. At that acceleration, you'd reach cruise velocity of 300,000 $m \over s$ in 23.1 minutes.
If 150 tons is not inclusive of fuel, you'll need 1,725 tons of fuel. Total weight = 1,875 tons. Acceleration in this case would be 17.28 $m \over {s^2}$, and it would take 4 hours, 49 minutes (approx) to reach cruising speed.
Acceleration will actually vary over the course of the burn (as the weight being pushed starts to drop), being lower than the average value at the beginning of the maneuver and higher than the average at the end.
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[Question]
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Imagine a supercolony of bees (I'm using bees as a metaphor; they're not really bees) which are the constituents of a massive globe-spanning hive mind. The government wishes to exploit this supercolony for its own use: as a weapon to use against enemy forces, which would be a big help.
There's one problem, however. The bees can't be coordinated very easily with external stimuli. They have to be controlled internally, from the central intelligence of the hive. The government begins the search for a person who can be inducted into the hive.
**Why would a human be predisposed to joining a hive mind?** Preferably, the answer is simple, science-based, and plausible.
[Answer]
**He is a weird kid.**
He is different, and weird, and crushingly lonely. He was born different and weird but he is still little and so people give him the benefit of the doubt. He wants to connect with others and he tries hard but he cannot make it happen to his satisfaction. He feels isolated and lonely and struggles to communicate this feeling.
His parents thought he might be autistic. He is not. He is something else. His mind craves a closeness and connection that is not possible with human biology - we are each stranded in the lonely island that is our body, calling out to the other islands across the void.
In the hive mind, he finally finds the connection that he craves. And there is much, much more to the planetary hive mind than the government realizes. It is not just bees.
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[Question]
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So, when you use a dragon for military purposes, it's probably for the best to keep them close and keep them happy. Which means building them a place they can call home.
Now, housing a dragon is quite difficult, you have to proof the place against hissy fits when the dragon start flipping tables, you have to make sure the home is defensible if assassins come around, and most importantly, you have to make it comfy! A warm fireplace, a soft bed of the right size, etc...
## The dragon
So, your typical western dragon with six limbs in total. Size is generally where I have a breakdown but I say 2-2.5 meters at the highest point (where the wing's humerus is located) and 500 kg in weight, thanks to pneumatization. The wings span at around 12 meters and are the broad soaring type.
The dragon's scales provide some protection and the pneumatized layer between the skin and muscles makes laying on a hard floor more bearable, still, the dragon demands to have soft things they can lay on.
The total body length is 10 meters, half of which is the tail, their main weapon. Dragons have flexible necks and usually keep their head up, further adding to their effective height.
While dragons have a breath weapon, they never use it indoors.
Dragons have human intelligence. Though they can manipulate things with their wings and forelegs (they can opening a door) and with their mouth (like horses), they're rather gawky/clumsy.
This dragon doesn't really like humans but does like cooked and baked food, so he'll tolerate them.
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**Assuming late-medieval tech, what would a house for a dragon look like?**
[Answer]
Like a cross between a castle and a church.
Castles are better protected against fire, at least one side is (the outer walls). They are also build to withstand a lot of blunt force such as a battering ram or a rowdy dragon after a bit too much to drink.
Churches are less fireproof (see the Notre Dame or other churches that burned down). However their style of building would suit a dragon. Large open spaces and a lot of height because of the arches, which have their own supports outside of the church. If you put stairs at the far end of the doors you can have sentries keep watch for assassins in the wide open space that they have to travel through to reach the dragon. The height has another advantage: any heat will rise up and have more room to expand, allowing the humies that keep him company to keep breathing air instead of noxious fumes and reducing fire hazards.
The furniture would mostly be metal and stone. A table out of a big stone slab, or just more masonry, would suit the dragon fine. Although a dragon might enjoy a large heap of sand as well as it is reasonably soft and malleable to his desires. And all you need is a bunch of humies with brooms and buckets to get it in a heap again!
Any visible wood support beams would be ironclad and treated so it is less likely to catch fire.
[Answer]
The dragon can manipulate objects but is too clumsy for hobbies requiring refined motor skills. That means there's barely any activities left, recreational or otherwise that have to be done indoors. So the house just got a lot smaller.
I don't think stone would necessarily be the main construction element. It depends on whether these are permanent quarters meant for coddling the dragon, or temporary housing in order to utilise it, but I lean more towards a yurt design. Ask the Mongols; those tents are easy to keep warm; and it can be broken down and reconstructed wherever the dragon is needed. He could even carry the materials on his back as he flies to a new destination.
I think of an elongated tent which he can easily fit in, and have dinner delivered inside, but for stretching he should move out. The main materials would be rough cloth like jute; you don't need silk if you cannot tell the difference under the scales. Plus this cloth would be sturdy enough not to wear out too quickly, and easily replaceable if it did, because the whole thing is meant to be routinely disassembled.
Think of these as field quarters at the least, and maybe as permanent housing if I surmised correctly that he doesn't have any indoor hobbies.
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[Question]
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We already know how to heat things up, but what about cooling them? How do we make Earth's climate like that of Mars? Or go further: can we, by any hypothetical ways, make Earth somewhat like Pluto?
[Answer]
**Reflect sunlight**
* Release particles into the atmosphere that reflect more light than they trap (think [nuclear winter](https://en.wikipedia.org/wiki/Nuclear_winter))
* Deploy a massive [sunshade](https://en.wikipedia.org/wiki/Space_sunshade) at the Earth-sun L1 point
* Increase [albedo](https://en.wikipedia.org/wiki/Albedo) by painting the surface white, or growing white GMO crops, etc
**Reduce the greenhouse effect**
* Knock off some of Earth's atmosphere with a [giant impactor](https://dailygalaxy.com/2019/06/the-death-of-mars-asteroid-the-size-of-pluto-ignited-ancient-climate-change/)
* Shut off plate tectonics - which should slow the mantle convection that produces Earth's magnetic field, allowing the atmosphere to erode due to solar wind
* Pull greenhouse gases out of the atmosphere
You're limited in part by the mass of the Earth. Without drastically shrinking the planet or reducing its density, its gravity will be the same, meaning it still holds on to its atmosphere relatively well.
[](https://i.stack.imgur.com/Yn2hj.png)
Compare the locations of Earth and Pluto on this graph. Without moving Earth so far away from the Sun that it's as dimly lit (and therefore cold) as Pluto, or reducing it in mass to bring it to such a low escape velocity as Pluto, Earth will always be able to hold a much thicker atmosphere. That insulating air should always retain a little more heat.
Luckily, once the planet cools a certain amount through some of the aforementioned methods, you might get a **runaway refrigerator**. [Astronomynotes](http://www.astronomynotes.com/solarsys/s10.htm) describes how this contributed to the cooling of Mars:
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> Since Mars was slightly further from Sun than the Earth, Mars' initial temperature was lower. This meant that the water vapor condensed to form a liquid water layer on the surface. Gaseous carbon dioxide dissolves in liquid water and can then be chemically combined with rocks. This would have happened on Mars long ago. The removal of some of the carbon dioxide caused a temperature drop from the reduced greenhouse effect. This caused more water vapor to condense, leading to more removal of atmospheric carbon dioxide and more cooling, etc. This positive feedback process is called a runaway refrigerator.
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In theory, once your sunshade and impacts cause enough cooling, it might progress into a positive feedback loop that finishes the job.
[Answer]
A volcanic eruption dispersing aerosol and ashes in the high atmosphere can already cool down the planet, since those substances reflect back the solar radiation which is our main heath source. Famous example is the [year without a summer](https://en.wikipedia.org/wiki/Year_Without_a_Summer) following the eruption of Krakatoa.
Therefore I would say that a substantial amount of similar substances in the high atmosphere would be an effective way to lower the surface temperature.
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[Question]
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**I haven't used tag "magic" because while the process is magical, I am interested in resulting material, which is itself completely unmagical and follows physical laws of our world.**
So, I have a problem. My magic civilizations are due to reasons magical unable to use most metals in pure form or as alloys for most typical uses, only being able to use their compounds[read rocks]. Instead, some of them are able to refine organic material, and for example alter its shape or join it together similarly to how smiths can smelt. They mostly use bones and wood as materials for their weapons. **I already have wood covered(found out about densified wood), now I need to focus on bones.**
While metalwork is not in use, they're able to alter the material to some extent. **While the process of alteration is magical, the result of the process isn't. The material simply changes its structure or content, and there is no sustained magical effect after the process is over.** They can't(at least not yet) do anything as drastic as produce nano materials, but they can remove things that were useful for a bone in a living organism, but are bad for bone as a material.
**List of all restrictions:**
* no nano-materials
* they can remove things that were useful for a bone in a living organism, but are bad for bone as a material(marrow, microholes for blood flow, etc.).
* they can alter composition by removing material to make the quality better (it is possible to remove some of the calcium or colagen, but it's not possible to replace them with something else like metals).
* they can introduce new organic materials(not in the meaning of organic chemistry, but in meaning recently originating from organism, such as shells, teeth or recently cut wood, but not anything that was abandoned by the organism years ago) to the bones. (Yeah, I've read about [limpet teeth](https://www.bbc.com/news/science-environment-31500883) and I do plan to use that, but only for extraordinarily expensive weapons for nobles, as it is a rare material in my setting, but I also need standard weapons for common soldiers)
**So, How much can bones be improved as a weapon/armour material under these restrictions?**
[Answer]
Good is a relative term, but weapons and armour are relative things anyway.
Bone and stone tipped spears are good enough if all your opponent has is bone tipped spears but not if they have bronze. Bronze is good enough if they don't have iron. Iron is good enough if they don't have steel. etc.
So how good can bone be? It doesn't matter if that's the best anyone can have. If someone is better at making bone harder than you are then you'll struggle, but it remains a relative factor. Any bone is good enough to pierce flesh.
Limpet teeth (5GPa) are stronger than flint (600MPa, 7 Mohs Hardness) in the headline values, but the two are not directly comparable as the value for limpet teeth is tensile strength and for flint is single axis compressive strength.
Teeth and bone (both around 5 Mohs hardness), tusks (2.75-3.50 Mohs), and horns, all tried and tested for penetration weapons, and all come behind flint as a primary option for weapon tips, but bone is easier to work. (Claws come in at a mere 2.5 on Mohs, horns I can't find a value for.)
So no matter what you do with bone, it's likely flint will still be a better option.
[Answer]
I think their ability to craft good weapons out of bone-material depends entirely on how fine structured shapes the can produce and how much they can learn from natural bone structures.
Bone is not stronger than rock, so solid blunt weapons (like hammers or maces) made from bones will likely never outshine rock counterparts. However, natural bones are not a solid chunk of material, instead - especially the strong adult bones that mostly consist of lamellar structures - bone is organised into a lot of parallel fiber structures that distribute material stress and strengthen material *in one specific direction*, this is why bones can easily hold (much more) than your weight if you stand on them, but moderate force applied from other angles can break them.
This allows bones to be both flexible and/or light while still being quite strong for their intended/necessary purpose. If the magic shaping the bones allows your people to understand and more importantly recreate these features they should be able to create weapons that are exceptionally light and strong at a single point (good for piercing arrow heads or spear tips, maybe inspired by bird bones) or flexible but strong along the edges (good for slashing weapons like swords or scimitars).
[Answer]
First let's get one thing out of the way. Bone material and density varies a lot from animal to animal, so you can't just pick up a hawk bone and expect it to have the same properties as a dog bone. So what creatures have the best bones?
Luckily the animal kingdom is full of creatures with strong bones. Think large and sturdy animals like cows, horses, even exotics like rhinos (which may have the strongest bones out there). So let's source our bones from slaughter animals, because they're already getting killed for food and leather.
Now that we have a strong animal bone to begin with (I'm assuming cow or horse femur would be a great start), let's look at the composition. [Animal bones are mostly collagen and calcium phosphate](https://www.google.com/search?sxsrf=ACYBGNR6WsEQTcuIk1e_9p-bMNdINLPYZw%3A1574345061123&ei=ZZnWXeSDB4-otQXHzYeoAw&q=what%20are%20bones%20made%20of&oq=what%20are%20bones&gs_l=psy-ab.1.0.0i273j0l9.109617.110936..112303...0.2..0.161.1075.0j9......0....1..gws-wiz.......0i71j35i39j0i67j0i10i67j0i20i263j0i131.KpkA7SIQrmg). Collagen is the soft part, but according to those sources it is also necessary to make bones flexible and durable, so maybe we should leave it. You don't want a weapon to be too stiff or it will break. So what else do we have to work with? Well, [the internal structure is spongey and full of marrow](https://www.google.com/search?q=structure%20of%20bone&sxsrf=ACYBGNSG8Eayo6gM14x9-QziMQtcrxUv8g:1574345452092&tbm=isch&source=iu&ictx=1&fir=FbhFkkVJcA1kbM%253A%252C4dHIKPLldyetOM%252C_&vet=1&usg=AI4_-kTuMUsSy_OIG0gD1RWHynLZv3FlbQ&sa=X&ved=2ahUKEwjkzLPrvfvlAhVFOKwKHcqACs4Q9QEwBHoECAcQMw#imgrc=FbhFkkVJcA1kbM:), so there's an opportunity.
Let's take your example of metal compounds (rock). Your mages could translate the marrow into a metal-dense stone for added weight and core strength, leaving the outside bone to provide the structure and a surface from which to carve an edge.
This would make bludgeoning weapons very easily, and with someone to shape the bones into blades you could end up with some interesting-looking swords. Take a look at the images in the second link and try to picture what it would look like shaved into a flat blade with a solid core.
All that being said, weapons made from the strongest bones (like rhinos) could be very sought-after, leading to poaching like we have today.
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[Question]
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In this fantasy world magic users are called rankers are graded into three grades:
**1,soldier grade** (Anyone with a magic weapon can become one.)
**2,champion grade** (requires years of training, only one in a thousand can
reach this level)
**3,general grade** (Very very rare. A nation will be super power if it can have more than hundred general grade rankers.)
Anyone above this power level will not be participating directly in battles, (like nuclear deterrent). This group will not be relevant to the question, just mentioning for completeness.
So, the gun technology was fairly undeveloped due to availability of magic.
-No Automatic reload.
-No precise sniping etc.,
A soldier grade ranker is similar to ancient warriors on earth with slightly powerful cold weapons. Mostly they will be killed if he/she meets a gun wielding enemy as rankers don't use guns (as they will be obsolete in later stages).
A Champion grade ranker can use powerful magics and can kill a gun wielding enemy before the bullet is fired. But even they will be in trouble if they meet a gun wielding enemy battalion. In front of hundreds of bullets, they cannot do much individually. At most they will kill tens of enemies before dying.
General grade rankers have domains of their own and can easily stop large number of projectiles as long as they don't contain large amount of energy (like a cannon shell). Of course, they have limits and will be defeated if you keep on sending human waves against them. However, it would take thousands of soldiers to kill a single General grade ranker.
Now my question is: *What will be the composition and deployment patterns of troops in such a scenario?*
**Assume that:**
Cost of arming a soldier with gun is equal to a magic weapon.
General grade experts are equally matched on both sides.
*Clarification about abilities:*
Rankers need catalysts to use magic. Catalysts can only be procured from dungeons. So most of the times rankers has to learn magic compatible with available catalysts than vice-versa.
Depending on the method of usage of the catalyst, rankers are generally two types. Warriors who embed the catalyst in some kind of melee weapon and mages who use catalyst directly.
Warriors use magic as an enhancement to their strength, so they use magic spells with little or no activation times and spend lot of money on making a perfect weapon for their catalyst.
Mages on the other hand design complicated magic spells to extract the maximum output from the catalyst.
These are only rough styles and every ranker is a mix of the two styles. Warriors also have flashy and powerful abilities and mages can cast instant spells.
*Clarifications about stamina and other requirements for magic:*
In this world there are three kinds of energy good, bad, neutral (called rajas). Gods and demons use good and bad kinds of energy. Humans manipulate rajas using catalysts. This is called magic, with different magic systems corresponding to different methods of manipulating the rajas.
Every mortal ranker (i.e not a singularity) has some kind of limit in usage of rajas. If a general grade ranker used too much magic for too long he/she would need some rest before being able to use magic. If they forcefully try to use magic in that time it will cripple or even kill the user.
Also Catalysts also have limits on their maximum output and will be destroyed if overloaded.
*Info about magic weapons:*
People need training before using catalyst or they would go mad. That is one the reasons soldier grade rankers use magic weapons (contains traces of catalyst) to get used before using the real thing.
Magic weapons are made from materials mined from dungeons. Even normal resources contains some traces of rajas. For example iron ore found in a dungeon can be extra hard or super light.
As said earlier, magic weapons are just slightly stronger than normal cold weapons. They generally don't rust or break down easily. May have resistance to temperature changes etc.
Only nations with huge manpower can take control of dungeon and mine resources from it.
*Relative strength of grades*
A General level is not invincible (A next grade of rankers called Singularities would take that honor). A group of twenty champion grade rankers can battle a general by attrition. Especially if the champions have abilities that counter General's domain.
As I mentioned generals are very rare and are treated as strategic assets. Every loss of a general grade expert will be a blow to nation's overall strength. In fact, most of the noble clans were headed by a general grade expert.
*About tech level*
Very crude guns with a need to reload manually after every shot. Mobile cannons were recently invented but not well received as most of the champions can do the same thing much faster.
It should be noted that the backwardness of technology is not due to lack of knowledge but rather lack of interest in the field. So no large scale assembly lines and standardized equipment. Magic can do what science can do and even what it cannot do. Especially since dungeons are a constant source of fear to the society, the powers that gained from dungeons are source of admiration.
Medical field is developed but is a hybrid between science and magic. In fact, dungeons were ingrained so deeply in the culture that development of technology mostly means finding new methods to use catalysts.
*About Singularities:*
The singularities (above general grade) are legendary existences in this world. They can reportedly even bend space and time. Legends about them inspire every youngster to become a ranker.
They are bound by an restriction to not fight in this world. If they break the restriction a heavenly tribulation will descend from sky.
It is said that singularities are resistant to passage of time. The possibility of immortality is another reason many people take the path of magic.
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> A related question which can make this question more clear.
> [Warfare-in-the-presence-of-magic-users](https://worldbuilding.stackexchange.com/questions/159884/warfare-in-the-presence-of-magic-users)
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[Answer]
Due to the proliferation of firearms (even if they're primitive) and their effectiveness against sub-champion level opponents, I don't think you'd see any "traditional" battle tactics with battle lines, cavalry charges, shield-walls, etc. Instead, I'd expect such a world to have military strategy be more akin to a modern military conflict, where small squads of soldiers move from cover to cover and it's essentially a deadly hide-and-seek game.
After the invention of modern firearms (notably rifling), the "stand in a line facing your enemy in a field and shoot" style of combat died out very quickly. For example, during the American Revolution against the British, the world saw how one of the most powerful military forces in the world was defeated by farmers with muskets and guerilla-tactics. While there were still some "stand in a line and shoot" conflicts after that, the practice quickly died out when weapon accuracy improved above drunken dart-throwing accuracy.
Modern combat is often about small squads of soldiers (groups of 10 ish) who move from cover to cover and attempt to seize control over valuable areas such as tactically important points, important infrastructure, or civilian locations. I imagine your world could be quite similar except:
* Substitute armored vehicles, tanks, or air support for "champion grade" fighters
* Substitute destroyers, tank regiments, or aircraft carriers for "general grade" fighters
In this situation, I'd imagine that a "squad" could consist of a dozen soldiers who are led by a champion. This would allow rapid movement and high combat effectiveness and still prevent the group of soldiers from being instantly slaughtered by an opposing champion. Other champions could be called in in "support roles". For example, in a modern battle soldiers could call in air support to deal with enemies in an entrenched positions, In your world, groups of soldiers could call in "champion support" who rove around the engagement area and solve problems that regular grunts can't.
General rank individuals would most likely be in a heavily "support role" and be the center of bases and represent FOB's or airfields. Their role would be to provide a safe place to retreat to and counter other general rank individuals from striking at "home base". In rare situations, they'd take to the field themselves but as they're quite valuable, direct combat would probably be kept to a minimum.
[Answer]
This is a resource war above all else, when you control dungeons, you control a region which gives you new soldiers, revenue, and labor (which is vital to mine the dungeons). In this world, manpower is everything. The entire conflict is a quest for enough military might to overwhelm Champions or Generals to force them into using rajas when they are exhausted. Armies have developed ambush and deception strategies specifically to begin a battle with expendable cold weapons, saving their rajas for the final blow.
**In the generic composition description below, replace the word “National” with the name of your protectorate or empire.**
1. **Military organization:**
$$ \underleftrightarrow{\hspace{32 pt} \fbox{Emperor} \hspace{32 pt}}\\ \tiny \fbox{Imperial Ministry} \hspace{80 pt} \fbox{Homeland Ministry} \\ \Downarrow \hspace{2em} \Downarrow \hspace{2em} \Downarrow \hspace{6em} \Downarrow \hspace{2em} \Downarrow \hspace{2em} \Downarrow \\ \hspace{1em} \small \text{501 401 301 201} \normalsize \{Legions\} \small \text{ 501 401 301 201} \\ \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \hspace{6em} \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \downarrow \\ \swarrow \hspace{1 em} Battalions \hspace{1 em} \searrow \\ \fbox{Conquest Brigade} \hspace{3 em} \fbox{Defense Brigade}$$
A nation has Imperial and Homeland department, for conquest and national defense strategies respectively. Each Department is led either by a Singularity who holds the position of Supreme Minister (if you’re lucky enough to have one), or a Ministry of National Supremacy (a panel of at least 3 elite generals). This means each Nation has at least two Ministries who report directly to the Emperor, and only the Emperor can direct them.
The National Army is divided into Legions of 8,000 to 12,000 troops. The number of legions a Nation has depends on their size and population. A small nation of 10 million may have up to 50 Legions to secure their borders and conduct conquest campaigns.
Legions are specialized to their region, with knowledge of the unique mountains, forests, coasts, or desserts in their area. Normally a General Grade (lower) commands a Legion, with one Champion serving as *Chief Security of the General* to protect the general and arrange his safe passage into battlefield arenas. Attacks on any General will have to get through this Champion first.
Each Legion commands several Battalions of 1,000 to 4,000 troops. Battalions are lead by Champions who hold secret conferences with their Legion generals (using magical telepathy, like the Force). This ability allows Champions to remain on the battlefield, get instructions, and give situation reports without bringing the General into the fight. As long as the Champion is not directly involved in combat he can use his raja this way.
Battalions command their brigades of any size depending on the special mission. Brigades are specialized first into either Conquest operations or Homeland operations. Within each of these each Battalion has a special warfare skill, commanding troops trained in their areas.
# Infantry Battalions
* By far the largest force in your army is the Infantry battalion. 80% of your forces are in the infantry, and of these more than 75% are using cold weapons. The advantage of cold weapons is they are cheap to produce, they don’t need catalyst, and they can overwhelm an enemy running low on raja. The cold weapons are always the first to attack, forcing the enemy to burn all their raja on defending themselves. Forcing a champion into overloading on raja is a key strategy, and once that is accomplished you can come in with your own Soldier Grade with magical weapons.
Infantry is divided into specialized divisions based on terrain. There is a **Mountain Division, Dessert Division, Woodlands Division, and Coastal Division.** They each have weapons, skills, and tactics unique to fighting in these environments. A Legion may not have all
# Airborne Battalions
* These troops include falconers, seers, and rarely wyvern riders. Their primary responsibility is to provide reconnaissance of enemy movements and to scout for safe passage.
**Falconers** send falcons over a territory and their soldier’s basic raja skill is communing. The falcon is their magic weapon, when the bird is adorned with an amulet made from catalyst.
**Seers** are Champions who can commune with nature and use wildlife to scout for them. Generally birds are better suited for this. Although a Seer can not control the birds like a falconer can, there are usually very many birds they can use, especially in woodland regions. But seers are not normally used in dessert campaigns due to the lack of wildlife.
**Wyvern riders** are Champions who have communed with a Wyvern and bonded with it. The Wyvern is a large dragon-like animal which can fly, but has no magical powers and has an average animal intelligence like a horse. Some airborne Battalions can use Wyvern riders for field command, allowing the Champion rider to see the entire battlefield when making decisions. The Wyvern can fly above the lethal range of most guns. If they do get hit, the bullet has slowed down so much it cannot break the scaly armor. Wyvern are also valuable to carry messages from the battlefield to Legion commanders quickly and securely without using raja.
# Marine Battalions
* These troops are equipped with magical weapons with specific strengths in water. They do not corrode, they can fire underwater, and so,e can even allow the soldier to breathe underwater for short periods. Marine Champions also develop special aquatic skills. They have normal sight underwater, as if they were in land. They are extremely efficient swimmers, and can assault a ship from the water. Their primary mission is overtaking coastal regions by surprise from the sea.
# Police Battalions
* One of the smallest Battalions, but also the most magical troops will be in the police battalions. They will either be Sentry class or Guard class, depending on what they are protecting. A sentry protects friendly assets, such as catalyst ore, hideouts, fortress gates, or treasure rooms. Their mission is to simply control access whatever they are protecting so no enemy can take or even see it. Their weapons and skills include things which can hide or lock the thing they are protecting, and fight off anyone trying to pilfer it. **Guards** are protecting dangerous assets such as war prisoners, captured generals, or anything else which could be hostile to the Nation. They have the same mission as a Sentry but also must be skilled in controlling the hostile prisoner. They have some very advanced weapons which will subdue their prisoner and prevent escape, without killing the asset.
Films often show guards and sentries as the weakest fighters but in real armies they are the most difficult to defeat. Several failed real attempts to break into Fort Knox demonstrate how tough these soldiers are. Your Police Battalions will use Champions to move high level prisoners around, and sometimes a Champion may dress as a regular Soldier and stand routine guard duty, surprising enemies who try to rescue their prisoners or steal your goods.
# Intelligence Battalions
* These elite troops include spies, interrogators, and tactical specialists. Legion commanders rely on the Intelligence Battalion to get the information needed to plan attacks on enemy fortresses or camps. These soldiers can look and speak like an enemy, use special language skills to collect information, and interrogate prisoners. Champions in this Battalion combine all their intelligence and form plans to maximize the effectiveness of the ground battle.
# Legions
A Legion is in command of a certain region. They will be numbered according to their location and territory. They can contain as many Battalions as they need to cover their area, and may or may not need every type of battalion. For example, a Legion in the Mountain region will not need dessert infantry or a Marine Battalion. Legion commanders report directly to their ministry. Conquest legions have missions involving expanding the empire and capturing new dungeons. Homeland legions have a mission to prevent loosing any Territory or Dungeons to enemy fighters.
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[Question]
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Scenario :
Due to the effects of a magical overload, there are people in my world who lose their magic. Those that don't go outright insane are left with damaged nervous systems and a high body temperature for the duration of their lives. This is supplemented by an increase in physical strength and endurance, partially due to increased ability to gain muscle mass, broken limiters, and magical handwaving stuff.
Potentially useful details :
* These people can still rarely have children, but the children will be born into and permanently be in this new state.
* They have no super healing, but there can be external healing factors applied to them. They're immune to any magical healing things, it has to be standard healing.
* Technology available is basically 1700-1800 USA
# Question
**The big question I have is how would it effect the human body to be in a long term state of mild fever (38.5-40 C) for the duration of their lives?**
Primarily what would their mental state be like, and what body systems would be struggling the hardest due to increased core temperatures? Would anything physiologically need to change to allow them to survive for a long duration (10+ years)?
[Answer]
A scientific article from the US National Institutes of Health titled [The pathophysiological basis and consequences of fever](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4944485/) gives a good review. From the abstract:
>
> Where heat generation exceeds heat loss and the core temperature rises above that set by the hypothalamus, a combination of cellular, local, organ-specific, and systemic effects occurs and puts the individual at risk of both short-term and long-term dysfunction which, if severe or sustained, may lead to death.
>
>
>
It goes on to describe damage caused by fever in three main categories: (a) cellular damage, (b) localized effects (vascular stasis, inflammation response, etc), and (c) systemic effects. These are summarized in the following graphic:
[](https://i.stack.imgur.com/QADtz.jpg)
## Cellular damage
While direct cell death occurs around 41 C, protein and DNA synthesis is disrupted at lower temperatures. This means cells replicate more slowly (or not at all). This makes sense: your body normally achieves a fever state for *fighting off infections*, so activating your immune system and slowing down the ability for cell growth is helpful. Chronic, long-term fever would mean more stress on organs (including organ failure), a slower repair rate for bruises and broken bones, et cetera. It would also mean, with some caveats, a lower risk of infection (because foreign invaders would not be able to replicate as easily. Furthermore, gut flora would also have difficulty replicating which means more stomach aches and problems with digestion.
## Localized effects
A slower blood flow (vascular stasis), increased risk for cancer (extravasation means white blood cells "leak" through the capillaries - good for fighting infections - but also means that cancer cells "leak" into different parts of the body), and overall inflammation. Inflammation means joint pain, muscle fatigue, digestive issues, increased risk of cholesterol blockage and therefore heart attacks, and, of course, organ damage or failure.
## Systemic Effects
Gastrointestinal bacterial translocation means bacteria in your gut ends up elsewhere. The biotics in your gut help you break down food (literally do part of the digestion for you). These same bacteria in *other* areas besides the gut suddenly become dangerous foreign invaders. As such this could lead to not only more stomach issues (fewer bacteria in the gut) but bacterial infections caused by those bacteria being elsewhere. Furthermore, "endotoxemia" means stuff that's produced by the bacteria in your gut getting into the bloodstream. So not only does the bacteria end up elsewhere, but the stuff the bacteria *produces* gets dumped into the bloodstream, which is not good.
All of these effects kick on pretty quick (they can be measured after 30 minutes of mild fever in animal studies), and are inconveniences in the short term (up to a few days), but chronic, long-term damage would likely result in serious organ failure and death. [The article](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4944485/) goes on to describe damage to neurons (cognitive dysfunction), issues with the cardiovascular system, serious liver damage, haemostatic system issues (how the blood coagulates in muscles and damaged skin), and so on.
In heatstroke (which is temperatures above your quoted range), a 28-day mortality rate was 58%, and a whopping 71% at 2 years. Furthermore, 33% (one in three) survivors of heatstroke have some moderate to sever functional damage, and 41% requiring institutional care after a year. Granted, this would be temperatures above your quoted range, but I would anticipate similar issues with lower fevers at longer times (such as 10/15 years).
Take into account the increased rate of water and caloric expenditure, and decreased ability to metabolize food, and your people would have to eat and drink *a lot* while dealing with fatigue, mental issues, organ failures, and cancer.
[Answer]
**They have syphilis.**
Chronic infection can cause chronic fever. Of the chronic diseases that cause fever, the big three are malaria, tuberculosis and syphilis.
<https://jramc.bmj.com/content/jramc/85/3/117.full.pdf>
Notes on the Significance of
>
> Fever in Syphilis with a Reference to Hypopyrexia" fever...may be
> accompanied by various symptoms including generalized muscle pains
> and gastric disturbance; suggesting typhoid and paratyphoid fevers.
> These latter are not uncommon in syphilitics in the secondary stage
> ; in a patient without marked gastric upset, in good general
> condition with a clean moist tongue suffering from this type of fever,
> syphilis must be considered. This continuous fever rarely
> :persists longer than six or seven days, but sometimes a true
> syphilitic fever lasts two or three weeks, or shows 2 or 3 plateaux
> each lasting about seven days
>
>
>
Syphilis has a lot of weird symptoms that are not well remembered now and would serve well in a fiction - examples being mental disturbances, neuropathy, rash and a host of others - syphilis is called "the great imitator" because of all the different symptoms the infected can manifest. It would be understandable if you did not want to actually use syphilis because youi consider an STD inappropriate for your fiction. But you could definitely have your people have a chronic infection.
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**They have lymphoma.**
Chronic cancer is another reason for fever - persons can live for years with low grade lymphomas, which cause lumps and bumps and intermittent fever. I think the white-skinned transfusion dependent warriors in the Road Warrior remake were supposed to have lymphoma because many had a lot of lymphadenopathy in their necks, and lymphoma can compromise blood production in the marrow.
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Fever means you burn calories faster and water evaporates from you faster; tjhere is a greater risk for dehydration. Higher fever can break down muscle - rhabdomyolysis. Fever can cloud the mind but these folks would be used to that. They might sit out the action if they were having a high fever day or they might chew willow bark for the natural antipyretics in it; willow bark was the precursor to aspirin which is excellent at lowering fever regardless of the cause.
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[Question]
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In my fantasy world, there are several species - both sapient and non-sapient. They all originally evolved from a group of insects that, after millions of years of isolation and no competition, have managed to evolve out of their anatomical constraints such as their respiratory system and exoskeleton.
Ignoring the sheer unlikelyhood of such a occurrence happening (which does have an in-universe explantation), **what would these changes to the insect anatomy form and look like?**
Let's assume oxygen levels stay (roughly) the same as modern day Earth without too much deviation, so no super bugs due to increased atmospheric oxygen.
Go, bring out the inner biologist within us all!
EDIT
Due to fact that this question is apparently a duplicate, I would like to clarify. This question is asking about land based insects and how the respiratory, visual, circulatory, skeletal etc are changed due to an increase of size after enough time to evolve.
[Answer]
The respiratory system and exoskeleton are not actually as strict of constraints as most people have been led to believe. For example, it's not actually the use of trachea in and of themselves that limits access to oxygen--it's reliance on passive diffusion. Improving the circulatory system and adding pumping to the function of the trachea (which some insects already have!) take care of that problem just fine.
Exoskeletons are more of a problem, but not in the way that is most obvious. Yes, they can be heavy, and that limits the growth of terrestrial arthropods somewhat--but in areas where there is little or no competition from tetrapods, arthropods can get *really big* already--and that's without even considering extinct clades like the famous carboniferous-era meganeurans. Consider, for example, the coconut crab, which can be up to 1 meter long!
The biggest problem with exoskeletons is the need to shed them as the animal grows. Molting gets harder as the organism gets larger, and it can become a very stressful and potentially deadly experience. Lobsters, for example, are sort-of functionally immortal, in that they show little to no signs of senescence, and just keep getting bigger as they age--but if they don't get eaten first, they will eventually die from the stress of necessary molting as they just keep growing. In fact, there are plenty of insects that just *don't* ever molt in adult form, because it's just not worth it--it wouldn't extend their lives enough to justify the risk. On the other hand, though, molting does come with advantages--it gives you a way to heal from *massive* injuries. Every molt is basically a full morphological reset.
Exoskeletons are thus not *as* good as endoskeletons for growing large, but they aren't *inherently bad* either. In competition with tetrapods, large arthropods tend to lose out--but your whole scenario is about eliminating that competition! Thus, I would expect to see quite a variety of quite large insects with little to no major development in their externally-obvious features.
To improve oxygen delivery, you'd want a more developed circulatory system, with more closed components; it need not evolve into a completely closed system, but it would be helpful to have better specialization of haemolymph vessels dedicated to picking up oxygen from the trachea and distributing it to the rest of the body. Additionally, you could see the evolution of "diaphragm" muscles designed to flex the body wall, thus changing internal volume to actively pump air in and out of the trachea; this sort of development has already happened once with the development of insect wings from the body wall.
In order to deal with the exoskeleton, you can imagine basic structural changes to make them more efficient at large size, like thinning out the skeletal wall on one side of a limb and thickening it on the other, with reinforcing spars extending into the interior of the limb, so it acts structurally more like an endoskeleton with muscles clumped on one side. None of that would be externally visible, though. The jackpot would be evolving a method of digesting and remodelling chitin after it has been laid down, thus eliminating the need for molting as the skeleton could then grow with the rest of the creature. That seems like the least likely option, but it would also not be externally visible.
Another way to sidestep the molting issue is to just not molt that much. You can have large eggs that produce large initial larvae, that grow even larger and metamorphose directly into a pretty-darn-big adult, which then does not have to molt as many times (or perhaps at all) to attain its final size. Adult molting may be retained in some clades as a response to serious injury, though--sure, the molt might kill you, but if you don't molt, you'll die anyway, so might as well roll the dice! If you win, you get a full reset and more years to reproduce.
As for what changes would actually be visible in adults--what they would *look like*--it's all basically square-cube stuff. You either get creatures that all stay very low-slung to the ground, distributing their weight over a large area, or you take the basic design of grasshopper back legs and apply that to all the weight-bearing limbs--i.e., move them closer to the body and more up-and-down, rather than splayed out to the side--to permit taller-standing creatures, and you increase the relative cross-sectional size of the limbs compared to the body as the whole creature increases in mass. Thus, a meter-scale mantid, for example, would probably have four enormous beefy grasshopper-like legs, with the front two oriented nearly straight up-and-down (and the back ones bent solely so that the positions of the feet form a large and more stable box than the close-together thorax attachment points would otherwise permit), rather than the wispy legs and wide-box stance typical of present-day mantids, while the non-weight-bearing forelimbs could remain essentially unchanged in relative scale.
[Answer]
The use of [trachea](https://en.wikipedia.org/wiki/Trachea#Invertebrates) limits their size very sharply. A higher partial oxygen pressure might help a little, but not much. You mentioned they are supposed to evolve beyond that, but what does that mean? You get a species that is ...
* Egg-laying.
* With compound eyes.
* Six legs.
* Endoskeleton.
* Circulatory system for nutrient and oxygen transport.
Within these constraints, you could get something that looks almost like a dinosaur, or a mammal. The length of limbs is a minor change compared to the basics.
[Answer]
Some insects like the Stalk-Eyed fly are able to grow their own anatomy to enormous size. Their eye stalks small when they are born, but within fifteen minutes or so after birth they rapidly expand them extremely long. It is reasonable to assume that fantasy insects would have functions like this.
<https://thesmallermajority.com/2013/01/21/stalk-eyed-flies/>
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[Question]
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On the Earth, with our atmosphere, even small objects entering the atmosphere such as [Tunguska](https://en.wikipedia.org/wiki/Tunguska_event) or [Chelyabinsk](https://en.wikipedia.org/wiki/Chelyabinsk_meteor) can do devastating damage due to the shock-wave travelling through the air. People could be injured by the shockwave itself, which can knock down trees if strong enough, or be bombarded with flying debris (usually glass from broken windows). Most asteroids themselves won't even touch the surface before burning up from air resistance.
What would happen on the moon? Assuming this Wikipedia article about the properties of [lunar craters](https://en.wikipedia.org/wiki/Lunar_craters#Characteristics) is accurate, what would an astronaut in a pressurized spacesuit experience if standing at varying distances from the impact of a small meteroid? (I suppose "small" is a relative term here, so I'm going to say that the crater generated would be about a 20m radius). I'm using [this video](https://www.youtube.com/watch?v=q1n-XgNKY2I) as a reference for the behavior of Moon dust after being hit by a crater.
What would happen if 3 *very* unlucky Moon colonists were standing:
1. A meter away from the impact point? (NOT being hit by the object, but very close)
* In my head, I imagine they'd be tossed upwards with all the moon dust and probably die from whiplash or having their suit torn open by flying debris. Does that sound about right, or could the ground be blasted away from under their feet and leave them in midair?
2. At the edge of the future crater? (15-25 meters away)
* According to the wiki article, the rim of the crater is where much of the ejected material builds up after gravity pulls it back down. Would astronaut #2 be hit by debris launched sideways from the impact, or be buried by falling dust shortly thereafter?
3. Dozens of meters away, close enough to see the impact?
* In Earth's atmosphere, they'd be hit by the shockwave in air. On the moon, would there be an earthquake-style tremor or anything of the sort?
[Answer]
# Dead, dead, and – you guessed it – dead.
For all three of your scenarios, the astronaut would be utterly destroyed.
1. The inside radius of the future crater is instantly vaporized. It temporarily becomes liquid-like and ripples due to the high energy impact. Nobody would survive within that radius.
2. At the edge of the crater, the resulting shock wave and the amount of debris (called ejecta) would kill anybody close to the crater.
3. You are unlikely to survive if you are even remotely close to the crater. Perhaps a few kilometers away you'd be safe, depending upon the size of the resultant crater. Either way, if the size is being measured in meters like the question describes, you are definitely dead.
[Answer]
This [550 pound WWII bomb](https://www.washingtonpost.com/world/2019/06/25/mysterious-explosion-left-crater-german-field-it-may-have-been-wwii-bomb/) produced a 5 meter radius crater in soft farm soil. To make a 20 meter radius crater in moon rock would require at least the equivalent of several tons of explosive. The insta-kill radius is going to be at least 10's of meters out from the edge of the crater. Quite likely everybody within the distances you described is automatically dead. Quite possibly at distances 1 and 2 they are dispersed to an extent it is difficult to be sure that anybody was there. At distance 3 it might be tough to be sure how many people were there.
Note added to respond to comments: The atmosphere is not very important in such explosions. The blast effects are not created by the atmosphere, but by the rapid expansion of the material that is being drastically rapidly heated. This is why the crater forms in the first place. The expansion of the material involved in the explosion is negligibly affected by the air. In the cited example there were about 550 pounds of explosives, which dug a crater roughly 3 meters deep and 5 meters in radius. Assuming that the soil is typical density for dry soil of about 1.33 g/cc, that as much as 300 tons of soil moved. The amount of air in the hemisphere above the soil is something like 700 pounds. The air has not got energy to do anything with the soil.
The primary reason the left-over WWII shell had this much effect was that it was at least partially buried. An impact crater is formed because the impacting object begins by at least partially burying itself. This is why, when using explosives, they are nearly always implanted in the object to be blasted.
A crater in rock that was 4 times the radius would move 16 times the volume of rock. (Assuming the depth stayed the same. If the depth was 4 times as much, it would be 64 times the volume of rock.) And rock is typically about double the density of soil. So a 20 meter crater involves explosively moving possibly as much as 2000 tons of rock. (Or 8000 tons if the depth increased.) A little air will make no difference.
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[Question]
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Speedsters like Quicksilver and the Flash run far faster than a real human ever could. A human body could not withstand the force of friction, survive the rapid acceleration, or process stimuli fast enough.
An Android, however, could have far faster reaction times than a human, as well as survive far greater stress than us meatbags. With our current knowledge of materials and engineering, how fast could a robotic flash run?
[Answer]
Your principal problem is the aerodynamic profile, center of balance and grip.
We run inclining our torsos and waving our arms, forearms and hands to and fro. That creates turbulence. To say nothing of our frontal profile, created by Face + Torso.
Center of balance.
The head of a cheetah is at our hip. To maneuver around an obstacle we would need a gentle course correction, instead of turning on a dime.
Grip.
When a pneumatic hammer strikers the asphalt, it tears it apart. There is only so much force you can apply before tearing the surface you are using.
The alternatives are: increase the surface or increase the time of contact.
In order to "run", the maximum time the soles of the robot are touching the ground is going to be finite given a certain speed and leg length.
Boston Dynamics got a mechanical cheetah to clock below 50 km/h.
[Boston Dynamics Robotic Cheetah Clocked At 28.3 MPH](https://scitechdaily.com/boston-dynamics-robotic-cheetah-clocked-at-28-3-mph/)
That gives us a nice baseline for real and proven data.
Even if we indeed could reach the same speed as a F1 300 Km/h, there are inherent limits to the ROBO-FLASH body if it needs to be humanoid.
Unlike the F1 car, you don't have spoilers to generate down force in order to squeeze out more traction. Human body shape lacks spoilers. Unless you twist the Robo Flash ears :-P
Seriously, this is IMHO the main limit. The F1 cars generate extra downforce in function of speed. In excess of 2000 kgs. Some even generate so much force that it makes the asphalt ripple. Without it, the tires would rotate in place, overcoming the ground friction limit.
2 legs. The feet size is finite so you could theoretically make it run on all fours, giving you extra 2 points of contact with the aid of hands.
No tail provides fewer means to control the sharp turns. Soo good luck if there is a single obstacle in front. We are already hammering the floor with RoboFlash powerfull servo legs. A jump means extra force -> pneumatic hammer effect.
All of this without even a single mention of energy considerations, heat, etc.
I have no clue on how to determine the maximum speed for RoboFlash.
**I would start with the maximum mechanical force a shoe sized piece of asphalt can take and go from there.**
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[Question]
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Plasma weaponry is a staple of science fiction, but is often objected to on the basis that it expands too readily. There's no way to effectively deliver it to a target without spending a lot of effort of containment.
This is inspired by [this question](https://worldbuilding.stackexchange.com/questions/73959/a-sufficient-justification-for-the-infantry-using-lethal-directed-energy-weapon) which describes two directed energy weapon systems, with the second one originally labeled plasma, then struck through and labeled [ball lightning, silicon vapor theory](https://en.wikipedia.org/wiki/Ball_lightning#Vaporized_silicon_hypothesis).
The part I'm most interested in is how you'd actually create and throw the ball lightning. Firearms use a chamber and barrel, lasers use a lasing medium and lenses, railguns use capacitors and, well, rails. If I was building an infantry weapon that fires ball lightning, what would its main mechanical parts be?
[Answer]
We did it in the 1990's.
A railgun firing a plasmak (ball lightning) that is. Since the plasma is electrically conductive you can use it as both the armature and projectile. Muzzle velocity is insanely high, the projectile hits pretty hard just due to the speed, and as the plasmak impacts an object and is destroyed it releases a localized EMP - so the Star Wars ion cannon was actually not that far off. The big drawback is that the ball lightning disintegrates in a pathetically short distance in atmosphere, the structure is too unstable. In space however, you could get more respectable range out of this type of weapon.
Use a rail gun where one rail is an inner cone and the other rail is the outer cone. A donut of plasma between the cones acts as the armature/projectile. As it's forced out, it forms a stable(ish) structure called a [field-reversed configuration](https://en.wikipedia.org/wiki/Field-reversed_configuration) which works exactly like a smoke ring - it's rotating about it's axis and rotating so that the inside of the ring moves forward and around to become the outside of the ring. This semi-stable plasma ball is ball lightning.
See also:
[MARAUDER](https://en.wikipedia.org/wiki/MARAUDER) the Air Force Research Lab railgun plasma weapon.
General Fusion's [Plasma Injectors](https://generalfusion.com/2017/12/first-plasma-in-worlds-largest-plasma-injector-brings-general-fusion-commercial-fusion-energy-step-closer/) (the largest in the world) use the same type of design. Definitely check out this [paper](https://generalfusion.com/2008/11/development-of-merged-compact-toroids-for-use-as-a-magnetized-target-fusion-plasma/) as it breaks down the basic design. Their [research library](https://generalfusion.com/research-library/) is full of all kinds of cool stuff.
This one is a bit different, but is also a type of plasma weapon. The US Army used a pulsed laser to create an ionized path in the air and paired it with a tesla coil. Lightning follows the path of least resistance through the air, so paint a target with the laser then blast it with [lightning](https://www.army.mil/article/82262/Picatinny_engineers_set_phasers_to__fry_/)!
[Answer]
The Gungan method to launch ball lightning, or "boomas", is via catapult.
[](https://i.stack.imgur.com/kKthb.png)
<https://starwars.fandom.com/wiki/Gungan_energy_catapult>
The boomas seem to be ball lightning, plus goo.
>
> The booma consisted of blue plasma from the depths of Naboo's oceanic
> core, pressurized and forced into a shell that would burst if thrown
> hard enough. It was very effective against droids and vehicles because
> the plasma was electrified, and seemed to have the properties of an
> EMP weapon. It could also burn biological material and leave a trail
> of plasma "goo" upon impact.
>
>
>
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I've been toying with the idea of a global highway that completely circles the globe. Ideally it would (on average) be as close to the equator as possible but also hit or at least come close to major cities.
The technology doesn't have to exist now or even be completely realistic, for example we could theoretically cross the Atlantic Ocean using a tunnel or floating bridge at the closest point in the doldrums between South America and Africa.
I know that road travel would probably not be ideal for getting across the globe like this, but for the sake of this let's say it's required.
My initial thought was from Brazil, across the Atlantic to Lagos, Across Africa, Cross the Red Sea and Persian Gulf to Asia, Through India/China/Japan, Across the Bering Strait, Down through North and Central America and back to Brazil.
[](https://i.stack.imgur.com/3fD36.png)
What would this highway look like? What path would make the most sense?
[Answer]
Orbital Ring
This approach might be a bit too far out of the box thinking, but it would allow you to get an exactly equatorial highway. In summary an orbital ring is a space elevator for grown-ups and allows extreme feats of engineering.
Crucial to an orbital ring is the concept of active support. Whenever you build a structure you want it to stay stable. Buildings do this by relying on passive support, i.e. their own structure can carry their weight. This approach is limited by the ability of the building materials to resist the force the rest of the structure exerts on them. This is Newtons third law, actio = reactio. Actio is the force the structures weight delivers and reactio is usually the force the material must be able to muster. Yet nowhere it is said that reactio must be provided passively. Imagine a friend of yours is walking over a thin plank, which would break under his weight. The passive support of the plank isn't sufficient to counteract the force your friend exerts. Now you go under the plank and push it up, so that it can hold your friends weight. You are providing active support. The great thing about active support is that you aren't limited by puny compressive or tensile strength, you are dumping energy into the system to keep it stable. And you can dump infinite ammounts of energy into a system.
Secondly some basic orbital mechanics are important for the ring. An object moves through space on an elliptical trajectory corresponding to it's speed. The faster the object moves (i.e. the more energy it carries) the higher it will move. If the object is restrained from moving into a higher orbit appropriate for it's speed it will exert a upward force on the restraint.
Now imagine bringing a stream of orbiting, magnetic slugs in a circular orbit arround earth, lets say 200 km high. They will move at orbital velocity. Arround each slug we have a a metal ring containing electromagnets. The rings are loosely connected and under power. They too move at the same orbital speed as the slugs. Then we activate the magnets, forcing the slugs to move though the center of each ring.
Finally we start decelerating the rings with their magnets. This will transfer their momentum to the slugs speeding them up. The now faster slugs want to move to a orbit higher than their current 200 km. The now slower rings want to move to a lower orbit. But the magnets force both to interact. To be precise the rings want to fall down with the same force the slugs want to go up. Like on the plank with your friend, the situation is stable and the structure stays in place. We continue this until the outer structure sits statically over the earth. The rings, also called stator, sit fixed 200 km over the earth and levitate magnetically over the slugs, also called rotator, which keep the structure in the sky.
At this point you can drop tethers down from the ring to ancor it and to install elevators. One of the rings many advantages is that normal nylon ropes will work for this and that no fancy carbon nanotubes are required. You can send tethers down to everywhere within a ca 500 km distance from the ring.
As for the highway you can simply builed it on top of ring. Call it skyway 001. You just need to speed up the rotator to counteract the weight and this force the roads and vehicles will exert on the ring. You might want to roof over the road though, as most cars do poorly in hard vacuum.
You feel fancy and concider it indignifing to be carted up in an elevator? You want to get the road trip going by driving up inti the sky to cross the atlantic? I got you covered. Just use the tethers to have a road ramp with a manageable slope hang under the orbital ring.
As for how it would look like? Imagine sitting in your car, driving down a highway in Ecuador. There is the lovely nature with mountains and dense, exotic forests on both sides of the road. After winding up a steep serpentine you stop in on the top of the mountain gaining an amazing view of IT. A gentle, impossibly thin silver ark spanning beyond the horizons on both sides. It shimmers in the light reflected of its solar pannels and seems to sit in the sky on a silvery cobweb of tethers, connecting towns and people with their elevators. Your gaze wanders eastwards, towards the point where you will reach the ring, slightly above the horizon. At that point the ramp branches of the ring, arcing gently down to our ancient earth. Its base lays hidden behind the next mountain chain. You will climb the ecalera del sol.
Later that day you race over the skyway. Right and left views only granted to the few privileged occupants of the old international space station in the beginning of the 21st century are yours to enjoy. In the distance you can see the gold and green colors of Africa.
[Answer]
For all of the land based sections of this roadway no particularly new technology would be required, just a huge sum of money and standard engineering.
The tricky bit is building it across the Atlantic Ocean. One obstacle facing all options is the immensity of the distance. Even building a road on a solid surface for this distance would be an extremely expensive and time consuming undertaking. Building across this distance of water is preposterous. But putting aside the problem of scale how might this be achieved?
A standard tunnel running below the ocean bed would not work for a number of reasons. The pressure at such a depth would be enough to crush any normal tunnel, ventilation would be a nightmare and crossing the mid oceanic ridge would be particularly problematic.
A bridge would be better but would suffer from the difficulty of having a lot of very (very) deep supports or be an entirely floating structure. Floating structures would have to withstand hurricane force winds over hundreds of miles of open water.
I propose a hybrid system. The entrance would be on land near the coast into a conventional tunnel dropping to 100 metres below ground level and running out to sea. When the water depth exceeded 100 metres the tunnel would emerge into open water. Large sealed tunnel sections would be built in a suitable coastal area and floated out to sea above the end of the existing tunnel.
These would be weighted down with ballast to give them neutral buoyancy. The sections would then be lowered down until aligned with the existing tunnel to which they would be joined and sealed. The process would be repeated extending the tunnel across the ocean 100 metres under the surface. At regular intervals floating platforms similar to small concrete oil rigs would be built supporting tubes to the surface to allow ventilation and emergency access. These points could be anchored to the ocean bed by mooring cables. The subsurface tunnel would extend right across the ocean in this way and into a similar coastal tunnel on the opposite side.
[Answer]
You have been beaten to the punch
[](https://i.stack.imgur.com/RsBGA.jpg)
*[Transglobal highway](http://www.transglobalhighway.com/)*
The major issue with this is the insanely long transit times that road traffic would take. Driving cargo by truck halfway around the world wold be a very long and expensive undertaking. There is a reason people use ships, railways and aircraft to transport things long distances.
The only way this might be somehow viable would be to make this some sort of global high speed railway system to carry container freight which is then offloaded and carried by trucks on short point to point routes. By high speed train, we would need to have trains moving at the speed of a Hyperloop (800 KPH) or even faster in evacuated tunnels using magnetic levitation. By combining the "throughput" of rail and the speed of aircraft, we would likely have a viable economic model to pay for the system. From the outside, it would mostly look much lie a giant pipeline.
[](https://i.stack.imgur.com/sKRrv.jpg)
*Hyperloops and evacuated magnetic levitation systems would look like this from the outside*
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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.
How would I calculate if it is possible to have an eccentric enough orbit around a gas giant to dip the periapsis some depth(how deep?) into the atmosphere of a gas giant like Jupiter or Saturn and taking into account the atmospheric drag, still escape to a stable orbit? Is this even possible or is there a calculator online that might help?
CLARIFICATION
I intended this to be a one time pass through with a man made ship or probe. Sorry for the confusion.
I want to use a story element where a spacecraft is setups up a high enough apoapsis to have the momentum and orbital velocity so they can "dive" into the planet's atmosphere to whatever depth is possible and have the energy to get back out to space. I can allow for them to add to the speed at Periapse if needed but I wanted to determine how deep they could dive and still get out with a margin of safety.
[Answer]
*Technically,* yes, but probably not how you’re envisioning.
If what you’re picturing is a craft dipping far enough into the atmosphere to look like it’s “in the clouds,” so to speak, and then exiting again back into space, then probably not.
However, you may be able to achieve something that at least somewhat resembles what you're imagining. Here's some factors worth considering:
It sounds like you need your craft to be in orbit for a while before it performs this maneuver. If instead you want your object to originate from someplace outside the immediate system (e.g., launched from another planet) and directly descend into the atmosphere once it arrives, then essentially what you're describing is an extremely dramatic version of [aerocapture](https://www.nasa.gov/vision/universe/features/aerocapture.html).
Either way, the key here is drag. Notice that with an aerocapture maneuver, the portion of the atmosphere targeted for increased drag is still extremely thin. This is because, at orbital velocities, just a tiny amount of gas molecules is enough to cause a whole lot of heat and friction. So, to a casual observer, craft undergoing an aerocapture maneuver do not appear to be noticeably “inside” any perceptible gaseous medium.
If you absolutely need to construct a craft that is able penetrate deep into the atmosphere of a gas giant at orbital velocities and then exit, then it would need to be:
1. traveling an order of magnitude faster than satellites typically travel, in order for atmospheric drag not to slow it down below escape velocity;
2. composed of magic space-metal to withstand the extreme heat.
If your craft is originating from outside the immediate system, then as long as it’s traveling fast enough to maintain atmospheric escape velocity, but slow enough not to exceed orbital escape velocity (and it doesn’t vaporize from the heat), then, yes, you could *theoretically* perform an insertion maneuver this way.
Alternatively, if your craft must perform this dive from an already-stable orbital position around the planet, it would need a crazy amount of thrust to begin the maneuver. (E.g., you include some propulsive means on the craft strong enough to boost the object back up to an appropriate speed or altitude. But again, the thrust needed would be enormous.) Otherwise, you'd just be initiating a [skip reentry](https://en.wikipedia.org/wiki/Boost-glide).
In both cases, it all depends on the aerodynamics of the craft, the atmosphere of the planet, the altitude and speed of the craft, and so on. There are many variables.
[Answer]
Consider the [Orbital Mechanics Wikipedia article](https://en.m.wikipedia.org/wiki/Orbital_mechanics), particularly the fourth main bullet point under [Rules of Thumb](https://en.m.wikipedia.org/wiki/Orbital_mechanics#Rules_of_thumb): "If thrust is applied at only one point in the satellite's orbit, it will return to that same point on each subsequent orbit, though the rest of its path will change. Thus one cannot move from one circular orbit to another with only one brief application of thrust." This is enough to show that what you want is not possible as you state it.
The last thrust applied to the spacecraft is from the drag of the atmosphere. That means that the resultant orbit will go through the atmosphere again, and the spacecraft will continue to do so on each orbit until it has decayed to the point that more of the orbit is in the atmosphere. There is no stable orbit that goes through the atmosphere.
There are two ways to get around this. One is to keep escape velocity after leaving the atmosphere, so the spacecraft returns to deep space and hence is not in an orbit. The other is to accelerate at the high point of the orbit, which will raise the low point, and that can remove the orbit from the atmosphere.
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I know of the conceptualized "Sinkers", "Floaters" and "Hunters" that Carl Sagan and Edwin Salpeter of Cornell conceived of - as possible life forms that might inhabit a gas giant. At the time they conceived of this, there was no real info about the amount of amino acids that might exist in the atmospheres of planets like Saturn and Jupiter. We have also learned a lot more about the composition of these planets. I am wondering if these life form ideas are still possible alien life forms that could develop in a gas giant of some type.
Based on the temperatures and composition of Sudarsky class II planets - which are closer in to the star. Supposedly temperatures become too warm for ammonia ice to be stable. Instead, Class II gas giants have clouds of water vapor, giving them a high albedo and a beautiful blue-white coloration.
Would the possibility of life of some kind be able to develop there and thrive? Would it mostly be microbial if anything? Would larger multicellular beings be possible in the forms Sagan and Salpeter dreamed of or some other form? Would it have to be Anaerobic? Could it have developed on a more terrestrial form of the planet before it grew to a gas giant?
I am curious about the possibilities of this for a story, but I want to make it at least believable even if it is just an unlikely chance of a life form of a kind we might not even recognize as life as we define it.
[Answer]
In terms of life developing on a gas giant? Sure, it's possible. At best you could have some form of single cell extremophile organism in the uppermost atmosphere. Even this however is unlikely, as Gas Giants are stupidly hot; what their outer atmospheres lack in heat they make up for in cell crushing pressure.
## Gas Giants
Heat, pressure and agitation (cause by the rapidly moving atmosphere) all increase entropy, which is bad for life. In fact Schrodinger coined the term negentropy, meaning negative entropy or tendency towards order, to describe the fundemental characteristic of life. Thus, an environment with super high entropy seems unlikely to produce life of any form, let alone complex multi-cellular organisms.
## Gaseous Terrastrial Planets
Instead you should look towards something like venus. Venus is not a gas giant, but it does have a super dense atmosphere. For this reason it is pretty much impossible for multi-cellular organisms to form, however those extremophile organisms do have a chance of existing in its outer atmosphere.
To increase the chances of these organisms existing, Venus used to be an earth like planet, perhaps even with large water deposits on it's surface. These oceans (if they existed) would have been ideal breeding grounds for life. Unfortunately the runaway greenhouse effect made all the oceans evaporate and thus destroy these breeding grounds.
If you want to continue with this concept, you could say that during this pre-evaporation period complex intelligent life evolved. Predicting their planets eventual demise, they could move to floating cities. While living on these floating platforms, they could evolve further to survive independantly of the platforms; perhaps developing wings to travel between cities and lungs capable of breathing in the new atmosphere.
[Answer]
**My idea:**
* Living in gas (dense gas): let's image the environment is a large sea of gas. Species could be a fish-like species that swimming in gas planet, or balloon like species (jelly-fish, maybe) at consume gas and floating around, becoming food for others gas predator.
* Living in gas (not so dense gas): let's image the environment is a large sky with no bottom. Species could be bird-like or balloon-like
* Living on island: there are floating piece of land in gas planet where creature can live on. Those creature can look like Earth, land-based creature (including tree)
A planet could have multi layer
* outer: not-so-dense gas, large sky, not many animal live here because not enough gas, difficult to breath.
* middle: not-so-dense gas, with a lot of island. People could live on those island.
* inner: dense to very dense
(perhaps toxic as it go deeper) gas.
**Some point of reference:**
In Star Wars, there are creature called [Purrgil](https://starwars.fandom.com/wiki/Purrgil), perhaps you can use as point of reference.
"Purrgil were a species of massive, whale-like creatures that lived in Deep space, traveling from star system to star system. It was their natural ability to fly through hyperspace that inspired sentients to develop the hyperdrive technology"
"n order to breathe, these space-whales needed to inhale stores of a specific green gas, Clouzon-36."
Purrgil is a whale that flying in space, and it feed on gas (Clouzon-36 - a kind of fuel for hyperspace) on specific gas planet. They do have ability to dive into the gas planet to inhale the gas.
See cartoon [Star Wars Rebels - The Call](https://starwars.fandom.com/wiki/The_Call) for Purrgil behaviour.
The game [AIRHEART - Tales of broken Wings](https://store.steampowered.com/app/531180/AIRHEART__Tales_of_broken_Wings/) build the world of floating island. It is good idea to check it out for the concept of "floating island" in not so dense gas planet.
I suggest reading [Can airborne floating/flying islands be scientifically possible?](https://worldbuilding.stackexchange.com/questions/33513/can-airborne-floating-flying-islands-be-scientifically-possible?rq=1) for more reference on floating islands.
[Answer]
As an additional reference you might want to have a look at the [origins of the hive](https://www.destinypedia.com/Hive#Fundament) in Destiny, which were living on floating islands somewhere within a gas giant. It might also be interesting to see how they described the world and how this story developed, so I recommend looking at the [books of sorrow](https://www.destinypedia.com/Grimoire:Enemies/Books_of_Sorrow#I:_Predators) which flesh the story out a bit.
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**The Scenerio**
In the very near future a NASA probe returns to Earth with a soil sample from an asteroid containing a strange substance able to catalyze cold fusion reactions. The economic value of this substance makes space exploration for more of this element promising.Soon, returns are soo high, that mining becomes a profitable business, resulting is dozens of Governments and Corporations pouring hundreds of billions of dollars into an exploration fund to search for more of the element.
Within a few years, the human population living in space explodes into the tens of thousands. While many of the colonies are mostly self-sufficient they were made with the expectation that they could be resupplied every few years. That said, the technology that went into them is not significantly more advanced than what is available today. The only major things that sets them apart from modern space stations is that they have the ability to mine and refine ore from asteroids down into their constituent parts, and the fusion catalyst gives them a nearly limitless supply of power as long as they can get access to hydrogen.
Then one day, without warning, the Earth is destroyed in such a way that it is no longer a viable source of any resources. *Description of how I plan for the Earth to be destroyed is available for discussion here [Apocalypse by Atomic Catalyst](https://worldbuilding.stackexchange.com/questions/136917/apocalypse-by-atomic-catalyst)*
**The Question**
Using only technology that could realistically be incorporated into space stations today (plus the 2 exceptions), could mankind use what is found in asteroids to survive indefinitely in space or would certain things simply be too difficult to supply, repair, or replace without Earth to continue the survival of the species?
**Conclusion**
Based on feedback, I see a there is infact a big hole in the basic principle of how long it would even take for this "near future" to happen; so, I'm gonna conclude my original model here as not worth passing the reality-check phase of development until I can get some key details worked out. Before I even begin to further speculate on this topic, I think I need to answer the more fundamental topic of [What is the minimum timeframe required to colonize the asteroid belt?](https://worldbuilding.stackexchange.com/questions/137026/what-is-the-minimum-timeframe-required-to-colonize-the-asteroid-belt)
[Answer]
# No
This question is similar to a previous one:
[Post-Apocalyptic Earth. Escape from Warehouse Moon](https://worldbuilding.stackexchange.com/q/129990/21222)
If people are going to space to mine stuff and bring it to Earth, they will probably take food from Earth with them because it's cheaper to make food here than in space. The oxygen here is free, for example, and cattle can [redacted] on the ground without compromising life support. So no space station would be farming-ready.
If you wanted to jury rig them for farming, you'd face a huge challenge. Space stations are lacking in two things that would be required for prolonged human survival:
* Arable land
* Cattle
Notice that if you wish to plant stuff and raise cattle, you need to add life support for those plants and animals.
Even to feed just a few thousand people with hydroponic farming, you'd need a space station larger than anything we've ever seen even in sci-fi.
We've had a question on how much infrastructure would be needed per perdon in a generation spaceship before:
[Ideal size for a relativistic generation ship?](https://worldbuilding.stackexchange.com/q/58043/21222)
The best answer so far says, and I quote, emphasis mine:
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> (...) Thus, a cruise ship has about 26 tons displacement per person on board with quite a bit of crowding and only a week or so's supply of food, but also with fuel and engine space in addition to areas intended to be occupied (we will need to account for fuel and engine space separately in this case because the fuel and engine requirements of an interstellar ship are very different from those of a cruise ship).
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> (...) It takes roughly 10,600 square miles of arable land with crops growing on them to feed the population of Seattle (with a population of about 652,000), while the city itself has less than 84 square miles of land area and not all of that is arable land (i.e. land that it is possible to grow crops upon). This is about **10 acres per person**. And, any interstellar trip is going to need to grow most of its own food (with artificial light because starlight is too dim). Even if you could be significantly more efficient than terrestrial farming on Earth which isn't optimized for land being extremely scarce, by an order of magnitude, you'd probably need at least an acre per person of space for food production.
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> **State of the art terrestrial farming techniques and a vegan diet leave you at about 2 acres per person**. The most optimistic estimates I've seen are as little as 1/4 to 1/8th acres per person, but some of the assumptions that go into that aren't well proven or demonstrated in practice. So, an estimate of 1 acre per person is fairly reasonable middle ground.
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> (...) So, in round numbers you'd be talking 23,000 tons per head of living space and food production space and nuclear power production for ship life support operations from which to feed and house them assuming an order of magnitude improvement in food production per square foot relative to Earth would be possible (e.g. by reducing less efficient animal food relative to more efficient plant food proportionately).
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I suggest going there for further reading and sources.
[Answer]
**Long agony but with chances for success.**
Drawbacks:
* with cheap energy there is not much point in creating manufacturing infrastructure in space. Under such conditions one orders all electronic or medications from Earth. In the day of doom, there would be no production facilities in space, but just a few labs or repair workshops.
* no chances for economics of scale
Assets:
* self sufficient colonies, that with moderate maintenance could last for centuries
* plenty of highly skilled engineers on board, who wouldn't go down without a fight
The thing is that it would be impossible to recreate global supply systems which produce for mass market. Everything would have to be produced in workshops with insane amount of work. On the other hand, Apollo 11 was flying with 2 MHz computer, so one does not require top computers for space travel.
Could one use high tech 3d design software to develop a primitive computer chip that would be produced with crude lithographic technology? Maybe. On the other hand after a few decades of jurry-rig maintenance such bases could be one step away from catastrophic failure.
One of things that mandkind would soon give up... would be space travel. It would make much more sense to clump all movable outposts together to save in future on transport. Yes, they need people together.
[Answer]
**No:**
The scenario ("*population in the 10s of thousands*") indicates limited space-based industry. Early space-based industry would be based on reducing the amount of mass that must be launched from Earth. While handy for, say, reducing the cost of food production and ore refining, complex and lightweight precision gear will surely still be manufactured on Earth when it is blotted.
That means the lightweight, precision equipment required for accurate ship navigation, engine control, and reliable communication will be irreplaceable.
As these components begin to fail, ships and crews will miss rendezvous and be lost. Without their vital cargoes (like ordinary vitamin supplements and space suit parts), outposts will die off.
You need a much larger space-based or Luna-based population, supporting space-based semiconductor manufacturing, habitat production, engine rebuilding, space suit manufacturing, hospitals and schools, etc. Consider moving your timeline a few decades farther into the future to make it more reasonable.
[Answer]
Yes.
Things such as radiation protection, technology in space, growing food, and even artificial gravity (via a rotating reference frame) are solvable with today's technologies. There are of course improvements to be made but these are all doable, just not necessarily done.
So the problem comes down to supply lines, logistics, and infrastructure.
Essentially each of these space habitats are the consequence of a supporting infrastructure, and every piece of it still needs to exist post-earth in order for them to survive.
That infrastructure is feed by, and interlinked by supply lines. Imagine the process required to assemble a wooden chair. There is a carpenter, a logger, a forester, a machinist, smelter, miner, real-estate agent, law courts, contract law, lawyers, managers, share-holders, bankers, sales-people, clerical, ... and the carpenter hasn't even picked up a tool yet.
Finally someone needs to ensure that supplies are being supplied to the relevant habitats in a timely manner, which is the heart of logistics. Given that you have a lot of hydrogen and energy potential in the solar-system, transportation is doable though slow. If logistics were disrupted you might expect the more distant habitats to succumb and fail. Those that were relatively self-sufficient, or recently restocked would last the longest.
Presuming that enough of the system was already in space aboard the other habitats or in orbital factories, then the loss of Earth itself will at most cause some short term turmoil as the infrastructure reorganised itself. That turmoil might be a civil war, but there is a good chance that it would re-structure itself eventually.
[Answer]
Maybe, if the stars (and asteroids) aligned.
They are mining stations. They might be small, but the asteroids they exploit could be quite large. So, lets make some assumptions:
1. The stations are mobile. Ideally, they could move from asteroid to asteroid to chase the resource they were mining, or, conversely, they have the means to bring arbitrarily large asteroids to them
2. Unlimited power
3. Low maintenance resource recycling supplies - the stations should be able to break down water in to air and fuel (hydrogen).
4. Air/water/waste recyclers are low maintenance (they do not rely on components from Earth to continue to operate)
With these in place, they need to find asteroids containing sufficient water and then asteroids that can be hollowed out and sealed against vacuum, as well as contain sufficient internal surface area. Since many asteroids are likely to be unstable accumulations of smaller bodies barely held together by weak gravity, this might be a significant challenge, but with unlimited energy, its mostly just a time constraint (finding and moving to it before supplies run out).
Since the recyclers can operate indefinitely, air and water is not your issue. Since you have unlimited energy, heat is not an issue. Since you are surrounded by endless space, non-recyclable waste disposal is not an issue. Only food is.
If you have the ability to hollow out an asteroid, seal it form vacuum, fill it with air (extracted from ice), and supply water (from ice) and fertilizer (from people), and impart rotation for gravity, then you are halfway to success. Now the real problems start.
Problems:
1. Plants take time to grow, so your existing store of food has to persist until you can harvest a crop
2. Do you have seeds? Likely, most of the food in your stores is processed. If you don't have raw fruits and vegetables, you likely don't have seeds
3. Do you know how to farm? Hydroponics and land farming both require somewhat more knowledge than just burying a seed in soil and watering it every so often.
4. Nutritional balance. Even if you have seeds and know how to farm, do you have the right seeds? A vegan diet is exceedingly tricky to pull off while maintaining proper nutrition. You'd need a fair variety of fruits and vegetables to make this work.
Solutions:
1. No real solution. If you can't wait for the first harvest, it's game over
2. No real solution. You can't grow what you don't have
3. With luck and trial and error, plus maybe they happen to have a copy of Wikipedia handy, this can be overcome.
4. No solution I can think of. Nutrition is a complex subject, and I'm no expert.
However, there are non-fruit and vegetable options that could help. Things like fungus and grasses grow quickly and easily (potentially solving 1 - 3) and certain kinds (so called superfoods) contain a large amount of nutrients, possibly helping solve 4. If it just so happens that one of the folks on the station was a smoothie freak and kept [spirulina](https://www.healthline.com/nutrition/10-proven-benefits-of-spirulina#section1) and such handy, then that could make the seemingly hopeless situation solvable.
A simpler solution might be to have a more permanent base on the moon or Mars (or a larger asteroid) that the smaller mining stations could attempt to evacuate to. This larger station might be a prototype or test for a fully self sustaining colony (I mean, come on, if Musk was still around at this point, you KNOW he would fund such a thing).
Long term, without the self-sustaining colony mentioned above, this will be rather un-enjoyable, and the lack of variety will likely have serious health effects as any number of micro nutrients are lacking. Without livestock (and there's very little reason to have live animals on a space station that doesn't grow its own food, much less the dozen or so mating pairs required to sustain a species), this will likely result in little more than delaying the inevitable.
[Answer]
**There are apocalypticists.**
<https://en.wikipedia.org/wiki/Category:Apocalypticists>
>
> Apocalypticism is the religious belief that there will be an
> apocalypse, a term which originally referred to a revelation of God's
> will, but now usually refers to belief that the world will come to an
> end time very soon, even within one's own lifetime.This belief is
> usually accompanied by the idea that civilization will soon come to a
> tumultuous end due to some sort of catastrophic global event...
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And they were right. The Amish colony in the lunar lava tubes uses some pieces of modern tech out of necessity. They have a fusion reactor and an air scrubber and a water recycler. But they are not supplied by Earth, out of principle. The fusion reactor is stunningly simple, with no moving parts. They are otherwise independent, with large sunny farms, trees, and industry appropriate for 1801. Large areas of the old tubes have been reclaimed; more than the Amish population needs. Much of this area has been allowed to turn to forest.
Earth kept a lot of the mining asteroids dependent on Earth goods because that is a way to keep them dependent generally and keep them from seeking a better price for their products or banding together in a kind of union.
When the Apocalypse does come, the moon Amish are ready. They are Christians and they are going to help their fellow humans in need. They have stores of supplies and educators. They have extra space and know how to make more. They save who they can, and that turns out to be a lot.
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Also as it turns out there were other colonies of apocalypticists elsewhere in the solar system. These others were not as public as the moon Amish, and their agendas are less altruistic.
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[Question]
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Humans have some genes that allow for a precise sense of smell, but they were turned off millions of years back, just like in many other primates. To name an exeption, lemurs are primates with a developed sense of smell, complete with a [VNO](https://en.wikipedia.org/wiki/Vomeronasal_organ). I would like for the humans in my story to have developed VNOs and a sense of smell similar in application to that of a lemur. Of course, there are structural limitations on the humanoid nose, so the sense of smell may not be *as good as* a lemur's, but much like it.
In particular, the humans in my story are nocturnal and eat fruit. They are [tetrachromats](https://en.wikipedia.org/wiki/Tetrachromacy) and have sharp vision, slightly better than that of real humans to see fruit at night. Would that evolutionarily detract form their olfactory sense? Most importantly, would a stronger sense of smell hurt intelligence?
[Answer]
Nothing, humans already have an excellent (if underused) sense of smell.
<https://www.theguardian.com/science/2017/may/11/not-to-be-sniffed-at-human-sense-of-smell-rivals-that-of-dogs-says-study>
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> In the latest paper, published in Science, McGann points out that in absolute terms the human olfactory bulb is bigger than in many mammals and a literature search revealed that the absolute number olfactory neurons is remarkably consistent across mammals. “We went to the medical school and looked at a human brain,” he said. “We put the human bulb next to the mouse bulb and gasped. It was gigantic.”
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<https://www.scientificamerican.com/article/the-human-nose-knows-more-than-we-think/>
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> The lack of a standard metric for scent is the main challenge, McGann says, in comparing absolute olfactory abilities across species. “It’s tempting to say humans are way more sensitive than mice at smelling human blood, and that sounds like a good ecological story,” he says. “But then you look at a whole range of other odors and realize that actually it just seems like there’s quite a lot of odors that humans are better at detecting than mice, dogs or rats, and other odors that we’re less good at detecting.” It’s impossible, therefore, to make sweeping generalizations about which species has the winning nose.
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The issue for us in modern life is that we don't need to use smell much and so don't develop a great deal of use for it. Trained professionals can use their noses much more effectively, and can follow scent trails through fields, distinguish between perfumes and food types and such. The VNO genes turned on wouldn't provide much of a buff. Ours already works fairly well.
<https://academic.oup.com/chemse/article/26/4/433/266106>
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> Opinion: The EVG constitutes evidence for a selective and sensitive response to human-derived chemicals located in the region of the VNO. Systemic autonomic responses and emotional changes elicited by stimulation in this region suggest some chemosensitivity, even though the anatomical substrate is difficult to demonstrate and seems unlikely to be conventional VSNs.
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<https://biology.stackexchange.com/questions/62624/why-do-humans-not-have-a-powerful-sense-of-smell>
Related.
[Answer]
The short answer to whether or not intelligence is affected by a better sense of smell is **no**, but the one thing you can say about evolution is that it trends towards efficiency and the question must be asked whether you need great vision AND great olfactory senses AND intelligence.
The brain (depending on the scientific paper you read) uses around 20% - 25% of the body's energy every day. That means that it's a massive energy sink that has to provide a substantial benefit to us to make up for that energy cost; and it does. It originally made us better hunters, more efficient with the resources around us, then better at building and refining tools that we use to achieve our ends.
Our five senses are in essence a part of our nervous system and provide key inputs to the brain. That sensory input also costs energy to sustain. I don't have exact figures on how much that cost is exactly, but there is a cost just the same. So the question becomes whether or not the development of an advanced brain is necessary if the combination of heightened visual and olfactory senses already make us better gatherers and more adept at avoiding danger.
Of course, there is another consideration here. Most evolutionary biologists believe now that the brain development in humans was only possible after the introduction of some meat into their diet. There are certain nutrients that proto-humans could not get from fruit and vegetables alone, and that the introduction of small amounts of meat, that transition into an omnivorous organism, was a key component of the development of modern human intelligence.
If that is the case, then it's arguable that heightened olfactory and visual senses has made your proto-humans adept in their environment; being able to forage and avoid danger sufficiently that the further investment in neural advancement (especially without the key nutrients provided by meat) may never happen.
Of course, the *other* consideration here is that most anthropologists believe that while we had the *capacity* for intelligence for many millennia before we actually started using it, the manifestation was brought on by our control of fire. Before that, we spent all our time surviving. After we harnessed fire we could sit around one, relatively safe from predators, and spend time actually thinking.
In other words, being capable of intelligence is not the same as having it.
What all this means for your proto-human stock is that by giving them a better sense of smell, you don't necessarily deprive them of intelligence, but you do very much change the priorities which evolution would apply to humans as improvements, and you also change their preferred environment to such an extent that two key contributors to the development of human intelligence (meat and fire) may not occur.
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Humanity, with modern science, has established that the Big Bang happened 13.8 billion years ago. The universe appeared in a low-entropy state, and for billions of years has been expanding and moving to a high-entropy state. We await, and dread, the [heat death](https://en.wikipedia.org/wiki/Heat_death_of_the_universe) ahead of us... and the end of all life.
One day, we discover a civilization that perceives time in the opposite direction. They have, with modern science, established that the heat death happened 10100 years ago. For them, the universe appeared in an extremely random and large state, and they're terrified of the Big Bang coming up in just 13.8 billion years.
Is this realistic? I understand that physical laws are valid in both directions of time, and that's why I'm asking this question. I can't imagine how a biological system could have memory of the future. Even with the computing tools we have today, it's very difficult to study the future, whereas it's relatively easy to study the past (e.g. we know much about the history of life thanks to paleontology, but we know almost nothing about its future evolution).
I'm also wondering how humans would communicate with this kind of life. What we see as "first contact" would be, for them, the end of contact. Before we even meet them, the aliens would know everything about us, and our entire shared history. Including how we watched them devolve, technologically and biologically. Standing on even footing with them, at any point in time, would be incredibly difficult.
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EDIT: I think some people may have misunderstood the question. To clarify, these aliens see the universe as contracting, as entropy in an isolated system going down, and as room-temperature water spontaneously freezing into ice cubes. This is because they have memories of the future, not the past; there is no "reverse time flow". This takes place in our universe, and time works exactly as it does now, on Earth.
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## The aliens are machines.
They reached a very singular singularity (pun unintended), in which they were able to precompute all that there was to precompute until the end of the universe. This is a massive task. The issue is that such a feat comes at a cost, and their hardware is slowly fading. Every moment that passes their immense memory storage experiences a loss and a piece of their knowledge gets lost. These singularly intelligent machines, however, have foreseen this as well and decided to arrange their memory storage so that the loss will never lose information about what is to come. They eventually reach a stationary state in which every knowledge of anything before the present instant is lost.
## How do they perceive time?
Past, present and future are our concepts.
We perceive time due to memory. We can't have a perception of time unless we can recall a time before the present. Further, we associate with the concept of future "the unknown direction", the one that has not been fixed by the flow of time.
Let's therefore consider a different time-dimension of "known" and "unknown". The known is fixed and immutable. The unknown is open and harbor of possibilities. The machines in the question have only a memory of the future. Hence, the future is "known" and immutable. The past on the other hand is unknown. It is hard for us to imagine, but for them, the flow from the "known" towards the "unknown" actually goes towards the past. Yes, we can argue that it is a bogus argument, because none of us is capable of perceiving it that way. That is exactly the point: it is not ours, it is their perception.
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**No**
Sorry. The reason we even came up with the theories and math supporting the universe's heat death was (among other things) noticing that everything is more-or-less expanding. For your society to legitimately believe as they do, they would need to view the universe as contracting.
Now, move backward in technological history long enough, say 1842 and the discovery of the [Doppler Effect](https://en.wikipedia.org/wiki/Doppler_effect), and people wouldn't know the universe is expanding.
However, they also wouldn't know about the "big crunch theory." The Big Bang Theory was [popularized after a BBC radio broadcast in 1949](https://en.wikipedia.org/wiki/Big_Bang#History) based on a lot of prediction that isn't important here. What is important is that the theory developed after the discovery of the Doppler Effect.
Which means your species would not develop a "Big Crunch Theory" unless they lived in a universe that actually was contracting. Otherwise, they'd figure out it wasn't happening before anyone popularlized the idea in the first place.
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If by past/future you mean cause and effect, as in, what happened in the past shapes what happens in the future, a society that perceives the future before the past would essentialy become omniscient. Since their "place of origin" is the point in time where everything that could happen has already happened (I assume the end of time itself would be to them what the big bang is to us), whatever reality they're in at any time is a direct result of something that is yet to happen to them, and since they know how things are in their "present" they can extrapolate (pretty acuratelly I'd think) how thing will be their "future", e.g.: They know there is a burnt down forest therefore they know a forest fire is coming. Their whole reality would be self fulfilling prophecy.
As for the plausibility, I'm not sure it's anywhere near possible with our understanding of how time works. The "flow of time" is intimately connected to our movement through space, the faster you move the slower time passes (btw, that's been proven by experiment, which basically means we've alredy perfomed time travel, I personally think that's pretty awesome), so when you reach the "speed limit of the universe" aka the speed of light, time is completely still. However, it's called the speed of light because only light can reach that speed since light is currently the only "massless thing" we know, anything with mass could pottentially reach speeds close to but never quite light-speed (it has to do with how particles stay together, if they move too fast it all just breaks apart). All that means that to travel back in time you would need to, not only be mass-less, but have negative mass, right now we know of absolutely nothing like that (no, anti-matter ain't it). There are however **theoretical** particles called Tachyons that travel faster than light (therefore back in time) but they're just speculation.
Hope I could help, I'm not a physicist by any means, but that's what I understand of the topic at hand, if there's any physicist out there, please correct me on all the stuff I probably got wrong.
EDIT: Oh, by the way, if you're thinking of maybe using tachyons, something that is interesting to point out is that the energy to movement dynamic kinda works in reverse. With "normal" particles, the more energy you use, the faster it goes and to get it to light-speed you need infinite energy, with tachyons it's the other way arround, you would need infinite energy to get it to move slower than light. I'm not sure what happens when there's no energy (I'll need to research some more) but I'd assume an "energy-less" tachyon would have infinite speed(?), so it would kinda be omnipresent(??), maybe(???), I really don't know, just speculation from someone that, again, isn't close to being a physicist.
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Inspired by [this question](https://worldbuilding.stackexchange.com/questions/122192/can-i-produce-a-true-3d-orbit):
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Consider a trinary star system, in which the three stars are arranged in an *xy* plane and all revolving the same direction, equidistant from each other. The inward pull of gravity is balanced by the [centrifugal](https://xkcd.com/123/) force, establishing an orbit about a common barycentre.
Now consider adding a fourth star, displaced in the *z* direction directly above the barycentre of the system (along the axis of revolution). This fourth star will, as far as I can tell, be pulled downward along the axis, past the barycentre, reach a distance away from the plane of revolution equal to the distance from which it started, and begin oscillating indefinitely along the axis of revolution.
The other three stars will gain degrees of freedom as a result of this fourth star. First, they'll move up and down along the z axis as their barycentre is displaced by the gravity of the fourth. Second, they'll begin to move in and out so that their circular orbit becomes more of a sinusoidal ring, as the gravitational attraction of the fourth star will increase until it passes between the other three, then decrease as it moves away from the plane of revolution.
This star system might be best described as a modified [Klemperer rosette](https://en.m.wikipedia.org/wiki/Klemperer_rosette), which can be in an ideal sense dynamically unstable - one perturbation and the system collapses. However, I’m wondering whether it’s possible for this system to be dynamically unstable in the same way that a traditional rosette is.
**Can such a modified Klemperer rosette ever be dynamically unstable?**
How this configuration came to be is out of the scope of the question - blame it on an incredibly powerful toddler alien who is learning to play with galaxies much as human children learn to build towers out of blocks.
Although I describe the system as "adding" a fourth star, I'm only interested in the stability of the end result (the simple harmonic oscillation of the system) and am aware that creating an additional sun in this way would destabilize the initially stable trinary star system.
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A set of N isolated bodies will always orbit around the center of mass of the system, and the orbits will end up being a conic curve.
What you describe as "adding a 4th star out of the plane containing the 3 stars" is already offsetting the center of mass, thus it won't go as you picture.
Either some of the stars will be kicked out of the system along an hyperbolic trajectory (which is a conic curve) or the orbits will be flattened out to roughly be contained in a plane. That's why galaxies are disc shaped, even though they collide with each other at random angles.
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Yes, you can arrange four stars in tetrahedron, provided the following conditions are met:
* the stars all of equal mass;
* the period of revolution of each star around the common barycenter is exactly the same;
* each star orbits in a perfect circle around the common barycenter;
* the plane of the orbit of each star is exactly perpendicular to the ground plane formed by the other three stars at any given point in time;
* the star's initial position is that of a perfect tetrahedron.
With these conditions, the tetrahedron maintains its shape and symmetry and there are no intrinsic perturbations in the system. In fact, any [platonic solid](https://en.wikipedia.org/wiki/Platonic_solid) can be formed this way. A configuration of five stars with one star in the barycenter which may then differ in mass from the other four will also work.
Note that these systems, like [Klemperer Rosettes](https://en.wikipedia.org/wiki/Klemperer_rosette) are unstable under any perturbation, because any deviation from the perpendicular brings a star closer to a number of neighbors and further from a different number of other neighbors; the gravitational imbalance becomes greater towards the closer neighbors and less for the farther neighbors, pulling the perturbed object further towards its closer neighbors, amplifying the perturbation rather than damping it. An inward radial perturbation or deviation from the perfect circle causes the perturbed star to get closer to all other stars, increasing the force on the star and increasing its orbital velocity—which leads indirectly to a perpendicular perturbation and the argument above. Differences in mass work the same way as deviations from the perfect circle.
You cannot create this system by just adding a star to an already existing formation of stars in the manner you described because the polyhedral configuration is a [repeller](https://en.wikipedia.org/wiki/Attractor) in the systems phase space, in other words, if the initial conditions are not just right (which holds true for the construction method you envisaged), then the system will evolve away from the tetrahedral formation to more stable configurations such as two binary systems or a binary system and two solitaries or four solitaries.
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The year is 2050, and genetic enchancement is now commonplace in society. People can currently opt to improve their bodies through the form of gene packages. These are geared towards increasing certain traits, such as strength, speed, hand-eye coordination, eyesight, etc, by manipulating certain genes in their biological makeup. An individual can pay for one package, or several to be implemented incrementally, with expense and quality being varied.
These changes don't take affect immediately, as the body needs time to adjust to these enchancements. It can take a period of five years for the results of the gene therapy to take place in a person's body. This creates a problem when it comes to sports, as you would have certain people adapting to the changes quicker than others, or benefit from simply having had more enchancements than others, or having paid for higher quality enchancement. This can lead to an unbalanced playing field in various sports, like football, boxing, basketball, and others.
Does the situation as it stands leads to imbalances among players, creating unfair advantages? How can leagues implement genetic enchancement in a way that prevents this?
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Take lessons from the auto-racing industry. Auto-racing is an inherently technologically driven sport. Your 6 year old Camry will *not* compete with a modern stock car or F-1 car... period.
The first thing you'll notice has happened in auto-racing is that every auto sport is carefully tailored with a specific set of rules stipulating what is allowed. There are a handful of "unlimited" classes, such as those we find for land-speed records, but they are the exception to the rule.
Each class will have to adapt as new abilities come to light. F-1 ran through a phase like this recently. It had to add additional rules regarding what cars could do because the manufacturers all agreed that it was getting too expensive to win.
You'll also see rules placed on *how* you can use things. F-1 currently permits some *very* limited regenerative braking. You are only allowed to use it to pass someone. Why? Because passing makes the sport more exciting (more revenue for the races), and because it was found that was a decent way to limit the new technology such that driver skill still mattered.
You see these things in other sports (weight classes or gender classes, for instance), but auto-sports is so wed to technology that it provides a great set of examples for what to do once other sports become dominated by a technology.
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In the year 2071 the Dysnomia incident happened. The *Dysnomia* (a mining ship) suffered a catastrophic failure and violently exploded sending its payload, an aged comet, hurtling towards earth. The comet proceeded to rip apart in the atmosphere distributing a massive amount of dust in the stratosphere leading too catastrophic global cooling. This global cooling forces a large portion of the human race to move into arcologies and urban areas, mostly abandoning the country side.
But is this series of events even plausible? That's what I'm stuck on is how to physically have these series of events unfold without:
* a massive impact (smaller ones are acceptable)
* blocking out the visibility of the sun (dimming is fine)
* Not too severe cooling that GMOs couldn't be bred within a few years to adapt to the new climate (most agriculture would move to vertical greenhouses however)
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At the right angle of impact a comet could get reasonably deep into the atmosphere before skimming off back into space. Usually that wouldn't leave behind a lot of material but a comet that had lost most of it's surface volatiles may be coated in a thick, but loose, crust of materials with a higher boiling point. Some of that crust would slog off into the atmosphere due to mechanical friction and heating during the comet's dip into the air. This crust forms naturally on comets as they get exposed to repeated doses of solar radiation and has been observed on an number of objects by comet survey probes.
To cause long term (more than a year or two) cooling the compounds you want to dump into the atmosphere are [Sulfur Aerosols](https://en.wikipedia.org/wiki/Stratospheric_sulfur_aerosols). Comets usually do have some sulfur but it's not usually a major component of their chemistry so the ship would have gotten lucky, or unlucky, to find one with that much sulfur in it. The degree of cooling is directly proportional to the concentration of sulfur that eventuates from the atmospheric impact event.
If the angle and momentum of the object is just right, or wrong depending where you're standing, when it first skims the atmosphere it will enter into an unstable orbit with deeper and deeper brushes into the atmosphere until it burns up completely or what's left of it lands, but usually it will hit once and then carry on.
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### Been there, done that!
This apparently happened already 1,500 years ago. [Scientists at Cardiff University, UK, believe they have discovered the cause of crop failures and summer frosts some 1,500 years ago – a comet colliding with Earth.](https://www.sciencedaily.com/releases/2004/02/040204000254.htm)
So the only part that is tricky, other than fine-tuning the size of the comet to come up with just the right amount of sun-dimming dust, is to figure out how a ship would capture a comet. Based on other things I've read, I think capturing an asteroid or two would be a lot easier than a comet. Comets have very large orbits, so they are moving pretty quickly when they get near Earth. Asteroids have more "typical" orbits. There have even been serious real-world proposals to capture & mine small asteroids using near-future technology, though to capture one that would be large enough to cause a nuclear winter would require some significant engineering advances.
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First, start with massenkatz' answer above. Then let us change 'comet" to "icy Kuiper Belt Object". Now if we accept what is valuable about this comet is the water, I think we have a possible scenario we can imagine that makes some economic sense.
We are no longer dealing with objects with highly eccentric initial orbits, but we do have the new problem of getting an Icy rock from Pluto's orbit back into the "industrialized space zone" closer to earths orbit. But the water resource is valuable and expected to remain so for generations as water itself is needed by the vast human population for life and the heavy hydrogen isotopes present in the ice are needed for energy production, so governments and companies can take a long view when designing their water supply chain. At any time there will be tens of thousands of icy bodies at various stages of de-orbiting towards earth in a process that takes generations to complete.
They arrive at this: manned or robotic survey ships travel to the belt. They locate good prospects by water/mass ratio, industrial value of non-water content, and viability of revisable orbital dynamics.
They have brought a host of small tugs. These are simple ion drive engines capable of delivering small but constant thrust continuously. They are attached to the target object along with a control module and this package begins the job of returning the object to orbit between mars and earth. Meanwhile, the survey ship moves to find its next target. It has supplies to recover 1000 such objects.
The return orbit of any body is very slow and complex. The ion thrust is very small, so even with an initial boost from another more energetic engine, changing the bodies orbit will take a long time. So, objects use gravity assist whenever possible. First with other Kuiper belt objects, then with planets and asteroids, the planned deorbit involves a series of encounters to first boost velocity and adjust trajectory, then degrade velocity and park the object in an orbit where it can effectively be harvested.
No two deorbits are the same. Companies deploy surveys to take advantage of possible gravity boosts from known high mass Kuiper Belt Objects and outer planets and their moons to return payloads as rapidly as possible using the fewest tugs but only the rarest and most favorable orbital dynamics result in return journeys of less than 250 years.
The incident that eventually sends one of these bodies to earth could happen anywhere along the supply chain, leaving earth with a lot, or almost no warning of the coming catastrophe.
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It sounds good but the population would have to move to the countryside rather that urban areas to be closer to food and water and it would be pretty massive.
The dust would likely cause respiratory issues. It would be possible for the dust to be thin enough that the sun shines through but then the dust would settle quickly.
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If you want realism, I'd be a bit concerned about the comet's contents. We have [visited a comet now](https://en.wikipedia.org/wiki/67P%2FChuryumov%E2%80%93Gerasimenko), so we have good information to go on.
If your comet was worth bringing back to earth, then whatever it is made of, must be valuable enough to justify the effort, and also capable of creating a persistent aerosol of dust or other material on atmospheric breakup, that is capable of triggering a cooling episode. Combined with current knowledge of comet contents, that might be quite a limiting problem.
If a warming effect was needed, then methane might be a valid answer. But for cooling - that amount of dust suggests a solid rocky comet, not a frozen one, and I'm not sure how well that fits current scientific knowledge.
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Later: I was just passing by, and noticed that I got carried away and forgot perhaps the main point — “*without*… massive impact…”. Sorry about that.
New thought. I know you can “drill” through rock using sound vibrations — or at least there are YouTube videos on this that look very convincing (they run the sound vibrations through a piece of metal that is pressed against the rock). (I just searched “youtube sound rock drill Egypt”; perhaps use “melt”.) Perhaps you could have some industrial-level system for vibrating a rock into dust. In the outlier case, the rock would be completely powdered before the mining ship ever arrived in orbit. (They could even have it already neatly sorted into bins by material type!)
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From the other answers… it looks to me as though it would be handy for the accident in question to disintegrate the comet. Offhand, you could have
* an object of sufficient mass, travelling at sufficient speed, collide with the ship/payload,
* the ship/payload crash into a sufficiently massive “stationary” object (at a sufficiently high speed), or
* an erroneous or accidental military attack (perhaps with an energy weapon?).
Alternatively, you could have the comet on a collision course with Earth, because of an engine/steering malfunction or failure on the Dysnomia — the comet thus does not have to be moving especially fast — and have someone deploy a nuke/laser/whatever to blow it up, as an act of self-defence — rightly or wrongly. This might give you the option of having nuclear fallout play a part in the disaster — perhaps from the ship rather than from the weapon. (Or maybe the Dysnomia was also carrying some other cargo that is dangerous to human beings (or bees…), or simply *might* be dangerous.) (This frees you from having to have the comet be both valuable and dangerous (citing “Stilez”).)
[ Edit — response to “L.Dutch - reinstate Monica” comment.
Hmmm. I guess I was thinking of an arrival decelerating to an orbit height… but, as you have pointed out, that is not orbit [blush]; it would involve accelerating laterally, and coming in at a tangent would be better. …And everything (else) is moving fast.
Two objects in the same orbit but in opposite directions would do as I described; this would require either multiple orbital directions or catastrophically bad navigation (or perhaps mostly just being “upside down“ (and blind) ). Another thought: maybe it is the other object that has the dangerous cargo.
Another possibility: a third party comet coming in obliquely through the orbital traffic — perhaps another Oumuamua, for the unexpectedness. (In this case, the Dysnomia would not have to be carrying a comet (and could be the one carrying the dangerous cargo).) ]
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You know how there are some beaches in the world where tons of sea glass or other random sea trash washes up, just because the currents and the shape of the land naturally collects it all there? I was wondering if something similar could happen out in space. Certain planets or solar systems where interstellar space trash is more likely to collect into asteroid belts, planetary rings, or just fall to earth. Completely naturally though, it's not being propelled by anything, it just floats there naturally over millions of years. How would that work? Could solar winds and gravity wells have a similar effect as tides and deep-sea currents in this sense?
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Yes, absolutely. Every planet has 5 locations around it or near its orbit where the planet's and the star's gravity cancel each other out. These are called [Lagrange Points](https://en.wikipedia.org/wiki/Lagrangian_point). L1, L2, and L3 are unstable, an object in them is only balanced in a very specific location and a slight nudge will knock it out of the Lagrange Point. L4 and L5 however, are stable; it takes more than a slight nudge to knock them loose.
There's a lot of other situations that fit the bill a little less, but you might still count them. For example there's a large number of bodies, including Pluto, that have ended up in a few specific orbits, guided into them by the influence of Neptune. In short, gravity fields involving 2 or more bodies are really complicated, and you can certainly get situations that are somewhat analogous to currents.
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Mostly no.
There are currents in liquids and winds in gases, but interplanetary space is very, very, very thin. Interstellar space is even thinner.
So subatomic particles, atoms, molecules, and particles tend to follow ballistic trajectories in outer space.
There are some exceptions. Stars emit "stellar winds" of particles which mostly radiate in straight lines in all directions from the stars.
If astronomical bodies like planets, moons, asteroids, comets, stars, neutron stars, black holes, nebulae, etc. have magnetic fields, those magnetic fields will alter the courses of any passing particles which are electrically charged.
Thus the Earth's magnetic field traps many charged particles in the "solar wind" and keeps them orbiting Earth in the Van Allen Belts, and similar things happen in the magnetic fields of other astronomical bodies.
And the gravity fields of various astronomical bodies can interact with passing particles or objects and bend their courses in various ways. Thus the gravity of large astronomical bodies produces zones that are relatively free of smaller objects, because they are pulled out of those zones over time, and zones that have higher concentration of smaller objects, because they are pulled into those zones over time.
Stars sometimes emit many times as many particles as in a normal stellar wind. The biggest such times are when a supernova explodes and expels a significant proportion of its mass, including heavy elements produced by the supernova, into space. The particles expelled travel outwards for thousands and millions and billions of years, and many collide with interstellar dust and gas particles and push them away from the supernova. Thus a expanding region of very thin interstellar matter is produced around the supernova. As expelled particles and the interstellar particles they hit move outward, the interstellar matter becomes denser at the edge of the wave of matter. And if that wave of matter density encounters another wave of matter density moving outward from another supernova, they may make a region of very dense interstellar matter that collapses under it s own gravity and forms stars and planets.
As for space flotsam ending up on space beaches, that is sort of true since there is very, very thin matter in space and every speck of space dust, asteroid, comet, moon, planet, or star can be considered a moving space beach.
Every object moving through space, be it a speck of space dust or a vast star, hits many smaller objects or particles as it moves through space. Those smaller objects or particles either bounce off or become part of the larger object due to chemical stickiness, magnetism, or gravity. So the object grows larger and larger over the eons as it moves through space, and leaves a tunnel of pure vacuum behind it, though that tunnel gradually becomes as dense as it was before as particles and objects pass through it.
Each day, Earth acquires many tons of space dust as it moves through space.
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> A micrometeorite is essentially a micrometeoroid that has survived entry through Earth's atmosphere. The size of such a particle ranges from 50 µm to 2 mm. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs).[1](https://en.wikipedia.org/wiki/Micrometeorite)
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> An estimated 30,000 ± 20,000 tonnes per year (t/yr)[2](https://www.sciencefriday.com/articles/up-on-the-roof-a-handful-of-urban-stardust/) of cosmic dust enters the upper atmosphere each year of which less than 10% (2700 ± 1400 t/yr) is estimated to reach the surface as particles.[14] Therefore, the mass of micrometeorites deposited is roughly 50 times higher than that estimated for meteorites, which represent approximately 50 t/yr,[15] and the huge number of particles entering the atmosphere each year (~1017 > 10 µm) suggests that large MM collections contain particles from all dust producing objects in the Solar System including asteroids, comets, and fragments from our Moon and Mars.
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Micrometeorites have been found on the seafloors and on land. Places on land to look for micrometeorites include:
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> Terrestrial sediments also contain micrometeorites. These have been found in samples that:
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> Have low sedimentation rates such as claystones[22] and hardgrounds[23][24]
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> Are easily dissolved such as salt deposits[25] and limestones[26]
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> Have been mass sorted such as heavy mineral concentrates found in deserts[27] and beach sands.[7
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So a beach where you might find macroscopic terrestrial flotsam like driftwood can also be a cosmic beach where tiny micrometeorites can be found.
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> Amateur collectors may find micrometeorites in areas where dirt and dust from a large area has been concentrated, such as from a roof downspout.[28]
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<https://en.wikipedia.org/wiki/Micrometeorite>[1](https://en.wikipedia.org/wiki/Micrometeorite)
<https://www.sciencefriday.com/articles/up-on-the-roof-a-handful-of-urban-stardust/>[2](https://www.sciencefriday.com/articles/up-on-the-roof-a-handful-of-urban-stardust/)
And of course Earth also acquires larger space rocks, up to the extremely rare asteroids and comets miles in diameter that could cause extinction events.
So space is mostly too thin a vacuum to have winds or currents in it, but there some situations vaguely resembling currents in space. And every astronomical object functions as a sort of a cosmic beach sweeping up cosmic flotsam.
And you might as well check out Isaac Asimov's novel *The Currents of Space*, which has an ingenious, though now obsolete, theory for the cause of novas.
It is the second story, by internal chronology, in the "empire" series *The Stars Like Dust* (1951), *The currents of Space* (1952), and *Pebble in the Sky* (1950).
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I have had an idea for a possible story, where the protagonists are some kind of future, sapient hominid descendants (Not descended from humans; bonobos or gorillas or something).
The main premise of the setting is that there is a huge diversity (In terms of number of species) of large mammal carnivores, specifically big cats, hyenas, bears and canines. I want to justify this scenario with some kind of plausible explanation, rather than "there just is".
The removal of humans is obviously going to help, and I never saw humans as being part of this age. I have my own idea, but I won't put it here; as I wouldn't want to start a discussion, which this site is obviously not for.
So, my question is; **What scenario would be a plausible way to justify the appearance of all these large predator species?**
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I tend to agree with YElm and TheTimeVoyager, and I'm mostly repeating some of their points hoping to say them clearer.
Gause's Law says that no two species can fill the same ecological niche. This is kind of self-fulfilling -- if two species coexist we can look for some way their ecological niches differ and always find something. It's kind of related to the Law of Fives. But it's related to reality.
To have more predators you should have more ecological niches for them. You need enough herbivore numbers to support many predator species. You want at least a breeding population of 10,000 for each predator, right? So if all the herbivores put together can only lose enough predated individuals to feed 100,000 predators, you are limited to 10 species.
One way to support a lot of predator types is to have a lot of herbivore types. Then the predators can specialize. Of course it's no good for a predator to specialize on a rare form of prey, so you need a lot of *common* herbivore types.
To get a lot of herbivore types you might want a diverse climate with diverse plants living on it. Maybe fifty kinds of dominant forests, with not 2450 but still hundreds of mixtures at their boundaries. Fifty kinds of scrubland with hundreds of mixtures. Dry land and moist land maybe not real close together but both present. Steep hills and flat plateaus.
Different habitats, different plants, different herbivores, different carnivores. Some specialized for particular situations. Some that generalize and can't compete in any one situation but can move in, get some benefit, and move on to something else.
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You need several ingredients:
## 1. Get rid of humans
As you correctly stated in your OP, humans are currently the greatest predators on earth. Get rid of them and evolution can take its course.
## 2. Big prey
Big predators need big prey to survive. We can see this dependence in dinosaurs like [Tyrannosauridae](https://en.wikipedia.org/wiki/Tyrannosauridae) and [Sauropoda](https://en.wikipedia.org/wiki/Sauropoda) and later again in [Entelodonts](https://en.wikipedia.org/wiki/Entelodont) (giant pigs) preying on camels and [Phorusrhacidae](https://en.wikipedia.org/wiki/Phorusrhacidae) (giant birds) hunting down horses. Evolution works like an arms race in these cases: herbivores get bigger to get *too big* for carnivores, so they become bigger as well.
## 3. Extremely diverse biotopes in the same location
The reason why there are so many different species in the Amazon rain forest is that there are thousands of islands separated by the Amazon river. Any species that cannot cross the river will eventually evolve in a different way than their neighbors.
Additionally there is the annual flood that swamps enormous areas for several months. Aquatic and land-based species circle through times of seemingly limitless space and times of very limited space. During the flood, land animals can only live in trees and during the dryer season aquatic animals have to cope with the risk of falling dry.
These conditions offer many niches for many species to evolve.
## 4. Separation between species
There can only be one prime predator. Entelodonts and Phorusrhacidae wouldn't have evolved at the same time in the same area because they are direct competitors for the same resources (big herbivores). You can have one big predator and one big scavenger in the same area, but never two species that are too similar.
So let the continental drift rip Africa apart, push the Antarctic into habitable temperatures, remove land bridges and pile up mountains between habitats to separate species.
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If you look at [speciation](https://en.wikipedia.org/wiki/Speciation) charts for the time immediately after major population bottlenecks there are often explosions in particular families but most of the new species don't go anywhere. For example immediately after/above the K-T Boundary mammals diversified greatly but most of the new species have since died out. They were able to diversify because there were many empty [niches](https://en.wikipedia.org/wiki/Ecological_niche) in the life web. Given the way humans suppress (read kill) large predators their sudden decline would have a similar effect, suddenly opening many ecological niches for which a number of species are competing, this would explain a massive, but short-lived, expansion of species diversity among large predators.
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Although it isn't incredibly common to have many large predators in one locality, it has actually happened before. One case of this occured in the Late Cretaceous of Northern Africa, preserved in places like the Kem Kem Beds.
Here, we have many large theropod dinosaurs running around together in the same place, including Carcharodontosaurus, Sauroniops, Abelisaurid dinosaurs, Sigilmassasaurus, and Spinosaurus. One hypothesis regarding their coexistence is that each animal inhabited a separate niche, hunting a very particular food source or inhabiting a particular habitat. For instance, Spinosaurus and Carcharodontosaurus might not have needed to compete because one hunted primarily in and around the water while the other preferred dry land.
These types of specialist animals might be your best chance for a plethora of large carnivores.
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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 want to put a circular city in geostationary orbit. The city will have a radius of 20Km. I was thinking of using quantum trapping/levitation to achieve this.
Here's what [quantum trapping](https://en.wikipedia.org/wiki/Macroscopic_quantum_self-trapping) is:
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> Macroscopic quantum self-trapping. In quantum mechanics, macroscopic quantum self-trapping is a phenomenon occurring in the state of matter called the Bose-Einstein condensate between two superconductors linked by a non-conducting barrier known as a Josephson junction.
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There's more information on [Physics Stack Exchange](https://physics.stackexchange.com/questions/15855/how-does-quantum-trapping-with-diamagnets-work).
Using earth's magnetic field would it be plausible to use the above method to put the city in locked geostationary orbit? No handwavium, please.
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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.
Any object placed into a geostationary orbit will remain there purely due to the virtue of gravitational and centrifugal forces. While external factors such as the gravity of other celestial bodies or the uneven mass distribution of the Earth will perturb the orbit, some light maneuvering thrusters will work just fine in the long term, provided you supply them with enough fuel. So the problem isn't keeping the city there, that happens almost by itself. Getting all that mass up there will be trickier.
Conventional rockets will work fine, as long as you have enough money and time. You can then construct the city directly in orbit, which shouldn't be a problem if you can get over the hurdle of launching that much mass up there in the first place. But there are better options than chemical propulsion available. Perhaps the best-known is the [space elevator](https://en.wikipedia.org/wiki/Space_elevator), a very long tether attached on one end to the Earth's surface and on the other end to a counterweight somewhere above geostationary orbit, kept erect by the centrifugal force generated by Earth's rotation. This dramatically reduces the cost of space launches, but it has its disadvantages. The material you're using [has to be extremely strong](https://space.stackexchange.com/questions/2/what-technological-barriers-do-we-need-to-overcome-to-build-a-space-elevator), beyond any material we have available today. Additionally, it can only be built at (or at least near) the Equator, and there are issues with security and orbital debris, among others.
Another option is an [orbital ring](https://en.wikipedia.org/wiki/Orbital_ring). This is a ring that spans around the Earth, kept from falling down by the angular momentum of a stream of orbiting material. I won't go into the specifics of how they work, but if you could build one of these, it would have tremendous benefits. An orbital ring can have sections that are stationary with respect to Earth's surface, and therefore you can build a tether from the ring to the ground relatively easily, requiring much less tensile strength than a space elevator would. Once you're in space, you can use a variety of techniques (perhaps something similar to a [skyhook](https://en.wikipedia.org/wiki/Skyhook_(structure))) to boost yourself up to geostationary orbit.
Incidentally, the ring would also provide a surface to build railways on (for ultra-high speed passenger/cargo transportation) or solar panels (without pesky weather to affect power generation). They're pretty spiffy. :p
There are many other options besides these, such as launch loops or space fountains. They are all grounded in hard science, more or less -- meaning they don't break the laws of physics, but they *may* require enormous feats of engineering and/or unplausibly strong materials.
One last note... all of this assumes that you're set on building your orbital city by lifting mass from the Earth's surface, but honestly, a better solution would probably be to mine a few asteroids for raw materials and use that instead. Depending on the specifics of your world, this option might prove much cheaper.
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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.
Macroscopic quantum self-trapping, at any scale, occurs only within/between Bose-Einstein Condensates, such condensates are by their very nature both homogeneous and unstable. If you reduce a complex system to a "Condensated" state, which, currently, we can't by any known practical or theoretical means (I know this because I'm writing material about using a similar effect for completely different purposes), what you would get back when it was "de-Condensed" would be a random distribution of individual [Bosons](https://en.wikipedia.org/wiki/Boson) at a uniform density within the space formally occupied by the Condensate in question. In other words you would have to reduce the city want to move to [Quark](https://en.wikipedia.org/wiki/Quark) soup *before* you could move it and you couldn't get it back in any recognisable configuration. This ignores the fact that the self-trapping process itself only works at magnitudes on the order of half a dozen particles at a time.
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So far as I can research, all rivers on Earth are flowing water. There are other substances that are liquid at room temperature. Are there any natural processes that could create a river of something other than water? I'm not talking just emptying a reservoir... I'm taking like a grove of maple trees making enough syrup to canoe on (not plausible, just for example) or similar renewable cycle to keep the river flowing. I've been trying to design one with no luck. (Acceptable would be a natural pump that recycled the fluid back to the start. I only need it to flow about 50 km.)
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The simplest answer is theoretically "yes" because there are many chemicals that are liquid at Earth's surface tempeatures.
But there aren't many (other than water) that have the right combination of all the attributes you need.
* Liquid at surface temperature & pressures (T&P)
* Available on the surface
* Evaporates at surface T&P
* Condenses at atmospheric T&P
* Light enough to be airborne at atmospheric T&P
Water isn't the most common liquid on Earth. Magma and the liquid iron we think is at the core are. Oil comes after water, if I remember correctly.
The problem is magma and iron don't remain liquid at surface temperatures and oil doesn't evaporate/condense in the atmosphere. So, no rivers.
As Dubukay points out in his comment, you can have *temporary* rivers, if there's enough volume. As you point out, there isn't enough maple syrup (a pity, that). I'm also a fan of honey, but there's not enough of it, either. Oh, and Willy Wonka's river of chocolate. But that's not naturally occuring (and that's the greatest pity of all).
Adding to this, you could use methanols, ethanols, alcohols, gasoline (not naturally occuring, but we'll include it), but they're all so volatile that they don't remain liquid very long and won't condense in the atmosphere.
It's really staggering to realize just how much water there is... and how magic it is... It's the goldilocks "just right" stuff. There's enough of it to consistently make rivers, it remains liquid at most surface T&P, it evaporates and condenses. It does everything you need to make a permanent river. And it's the only thing that checks all the boxes.
And I'm assuming that water-based solutions aren't part of the question, such as blood. But, frankly, there isn't enough of that, either. But it's worth pointing out that it doesn't count because it's just a water solution with something in it. If it counted, you'd need to differentiate between muddy water and pure water. So, "rivers of blood" must remain the provence of poets.
So, assuming what you're asking is whether or not it's possible to have *natural* rivers of anything other than water, the answer is no.
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## Water-less Options
[This Stack Exchange Answer](https://chemistry.stackexchange.com/questions/30976/what-elements-and-or-substances-without-water-are-liquid-at-room-temperature) describes some non-water materials that are liquid at room temperature. I'd say your best bet here would be oil or some type of hydrocarbon.
Maybe you have a natural oil well that happens to produce enough liquid that a surface pool forms and begins to flow downhill, like a spring-fed stream.
## Watered Options
You could more easily make a stream or river that is some parts water and some parts your mystery substance. Rivers and other natural bodies of water are not 100% H2O; they contain impurities, silt, and tons of organic material.
What sort of properties you need out of your water feature would of course determine what substance you mix and how much is mixed in.
For example, perhaps your water source comes from a spring that contains a great deal of 6,6′-dibromoindigo, turning the water bright purple, or some other natural dye turning your river the color of your choice.
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A river of urine would be feasible as long as there is a high density city upstream. Imagine a regular water river next to the city, which is used for water supply. Assume the residents or city planners don't want to pollute the river by dumping sewage into it. So instead the pipe the sewage over a small hill into the next valley over which happens to not already contain a river (of water). The sewage now flows down that valley, where it will either evaporate after several miles, or maybe will eventually reach the sea (or perhaps join up with the water river farther downhill)
Evaporation is only needed as part of the cycle if we assume a single substance cycle, but in this case the cycle involves, rain, water, human body, urine, ocean, rain.
Other more complex cycles involving syrup or beer may be possible as well. For example. A civilization has invented beer, and aquaducts, but not the wheel or the keg. The may brew their beer in the hills, and ship it by aquaduct (or "beerduct") down the valley to the port city. The cycle is now rain, water, brewery, beer, river, pub, human body, urine, ocean, evaporation, rain
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Slime molds apparently are incredibly smart for a single celled amoeba and where their smarts lie is in building efficient transport tubes for nutrients, which rival our own highways. They do this by rhythmic pulsating, allowing them to think with their whole bodies. They have also put them into robots and had them guide the robots so I know complex motor control is achievable in them as well.
My aliens are very much similar to these slime molds, but there is one big difference, mine are human sized and have a human level of intelligence.
**Could this method of thinking work for such an advanced creature and produce things like abstract thought, detection of symbolism, and all the other things that humans enjoy from their brains?**
They do have a neuron system (an alien equivalent), but is entirely dedicated towards sight and is meant only to react with the rhythmic pulsating and cause changes. Also the rhythm in them, unlike in the actual slime molds does't need to be universal: different parts of different pulsating structures could be producing the thoughts. But if possible I would prefer to squeeze as much intelligence out of as simple a system as possible.
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**Unfortunately, you have a major problem:**
Mechanical is not as fast as electrical. It isn't. See [this](https://what-if.xkcd.com/1/) for why. And, no. Liquids don't fair better because of [this](https://what-if.xkcd.com/147/). Now the brain doesn't just act electrically, it has a chemical component. But that chemical component is really just regulating the electrical component.
However, just because a mechanical pulsating brain is out performed by an electrical brain, doesn't mean you can't have a pulsating brain that isn't mechanical.
**Just make your pulsating brain work on the electrical piece**
I mentioned that the chemical part of the brain worked to regulate the electrical part. That's because of ion channels and electrical potentials which work to regulate the charge across neurons, among other things I don't understand as I am not a neuro biologist.
However, I do see a way that your concept can work, but the inspiration is not the brain, but the [spleen](https://www.npr.org/sections/goatsandsoda/2018/04/24/604059598/the-secret-to-deep-diving-may-lie-in-the-spleen). According to recent research, the human spleen contracts to release blood cells into the blood stream when the body is deprived of oxygen.
Now imagine a situation that your creature was constantly in danger of facing as it evolved, that gave it close to no time to react and this situation had a (simplified) yes or no choice. But it had to make it in almost no time. The survivors might evolve some kind of organ(s) in the brain that could squirt neurotransmitters out into the brain as a hyper fight or flight response. It would need to keep a supply of neurotransmitters ready in a sac of some kind. There is the inflate part of the pulsating brain.
The deflate part comes when they are forced to make a decision quickly. Their brains would contract quickly to given them more neurotransmitters to act more quickly. However, this could lead to your creatures being terrible negotiators as their brains would pulse if they were stressed or lying. The species might need to convert to space Buddhism to ease their minds before negotiations, but honestly I don't see them performing well as emissaries.
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I am using duck typing here. You know the saying? *"If it walks like a duck and it quacks like a duck, then it must be a duck."* The fact that the duck takes one whole solar year cross the street doesn't make it less "ducky".
It's the same with your alien. If its processing system has as many parts as the human brain, and each part can act like a neuron - only through mechanical means, rather than electrochemical ones - then it should be as intelligent as a human.
As Jake states, mechanical processing is slower than electrical. This is related to how fast information flows within the system. But it does not mean that the same processing cannot be done. [This XKCD comic comes to mind](https://xkcd.com/505/).
I'd also like to remember that an artificial neural network may be constructed to run in a regular computer with a single core CPU with relatively short bus and clock - which means it would be much slower than a natural neural network, despite being purely electric - but it would still be able to do much the same processing. You could replace the electronic parts with a series of servomotors and sufficiently large abacus'es and it would still be able to compute the same signals, just not as fast. By following this train of thought, a giant amoeba could be as capable as computer or an animal when it comes to processing. It just needs more time to think.
This might be relevant to you as well: [How would hormonal sentience work and affect the way a brain works in a plant or fungoind?](https://worldbuilding.stackexchange.com/q/43962/21222)
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Building off of [Jake's answer](https://worldbuilding.stackexchange.com/a/110580/39583), I'm going to suggest a completely different approach to make your brain pulse. Your alien brain still uses electrical signals, but they are MUCH stronger than in humans (handwave how/why, or ask in a new question!). Additionally the brain has large amounts of ferromagnetic elements in it. Now as each electrical pulse fires, it creates a magnetic field that causes the nearby brain to twitch.
This would probably be more of a vibration than a pulsing, but the brain would definitely move.
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So dragonflies are the sky’s perfect predator, and while their are many adaptations that make this one big one is their wings. And one character in my story has these along with other mammalian versions of dragonfly/damselfly adaptations, but for this question I will just focus on the wings. So could a wing like this exist and work in a genetically modified human, and if not is their another way to do it?
So these wings are an extension of the rib cage with a membrane connecting them a lot like bat wings. They look like dragonfly wings and use powered flight similar to insects. There are four of them(two on each side) and they allow the person to fly just like a dragonfly and with the elegance of one.
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This seems really impossible, the only thing you could do to archieve something close to this are mechenical wings combined with a jetpack like thing. The jetpack would give you enough height and you could use the wings to glide.
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No.
Dragonfly wings beat 30 times a second. Now try beating a 20 foot wing 30 times a second. It's not going to happen.
Dragonflies can get away with it because they're small. That method of flying fails to scale upwards. Once you get to large birds, they hardly flap at all and try to do most of their flying by gliding and riding thermals.
Next problem is humans. We have dense strong bones and heavy muscles which are not made for flying. Birds have light bones. Dragonflies have inflatable wings.
It can't ever happen. You might be able to engineer dragonfly wings on a human but they're never going to get airborne.
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The [Parachute Cities](https://worldbuilding.stackexchange.com/questions/38698/how-big-can-the-parachute-cities-be/38751) fall endlessly, ploughing their way downwards through an infinite blue sky.
The Big Blue is a universe of sorts. It certainly has no bottom, but it does have a concept of ‘down’. Objects, airships, people and whole islands plummet through the occasional clouds, permanently lit and heated by suns that float through the sky in the far distance.
But the air doesn’t move. Everything has a terminal velocity caused by air resistance, yet (as the famous philosopher Aristocralopholes points out) if the universe is endless, has no bottom, and everything is accelerating downwards, the air too should be moving downwards. The fact the air doesn’t move means the cities aren’t in freefall, so the residents feel gravity.
The question is why the air is still, or at least why the residents of the Parachute Cities can’t observe it’s movement through the universe.
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For the sake of clarity: in this particular universe gravity is uniform (but not necessarily 1g) the universe is infinite, and all points are filled with breathable air (save those filled by something else). Don’t worry about habitability of the universe or how objects come to be there, the focus of this question is by what mechanism the atmosphere can be prevented from falling at the same rate as everything else, leading to the phenomenon of terminal velocity and hence ‘gravity’.
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# The air's gravitational and inertial masses are different.
You could have something similar to [this](https://worldbuilding.stackexchange.com/a/103029), except the concept is more flexible for reasons I will explain more shortly (and of course it doesn't need to be frictionless since air resistance is an integral concern in your world).
First of all, since gravity is already different in your universe (where there's a downward gravitational pull without any mass-energy generating it), there's no need to keep gravitational and inertial masses identical. For anything. This could open up far-reaching consequences for all sorts of things, not necessarily just why the air and the falling objects are moving at different rates. At a bare minimum, the air alone could have zero total gravitational mass, and everything else could have its normal gravitational mass. Alternatively, all sorts of different elements/materials/forms of energy, including but not limited to air, could have varying or even negative gravitational mass, allowing all kinds of interesting effects à la [The Edge Chronicles](https://en.wikipedia.org/wiki/The_Edge_Chronicles).
Secondly, if one decides not to throw out *every* single principle of general relativity, gravity and acceleration can still be equivalent. In this case, it doesn't even matter that the air's gravitational mass is exactly zero, simply that it differs from its inertial mass (or even that the ratio between the gravitational and inertial masses of air differs from the same ratio for the falling objects). This way, the air and everything else will fall at different accelerations, and if you observe from a reference frame in which the air is stationary, the air *will* be stationary, with everything else falling through it at a rate that may be adjusted by adjusting the strength of gravity. It can even be falling "upward", and no one would be able to tell the difference. (Just swap "up" and "down" and it's the exact same universe.) Another option is that the air is the *only* thing that has nonzero gravitational mass, and it is actually what's falling upward. All of these are (basically) entirely equivalent descriptions of the same reality — that is, one in which air falls at a different acceleration from everything else.
Decoupling inertial and gravitational mass could also partially solve the issue you identified in your previous question. The cities need not fall at 1 g; they could be made of a material with a much lower gravitational than inertial mass (measuring, of course, from a reference frame stationary with respect to the air, as might be standard in-universe), and hence fall slower and probably more stably. In order to experience gravity ordinarily, the same cannot apply to humans, but the terminal velocity for a city (to the best of my limited knowledge) is going to be higher than, say, a human-sized chunk of city material, simply due to higher volume-to-surface-area ratio. It could be that the terminal velocities of humans and cities are in the same general range, allowing humans to skydive between cities after all.
In all, substances with differing gravitational and inertial masses might be able to solve this problem, and possibly more.
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This is not a question for an Einsteinian, for sure. Neither is this answer.
I picture this as a universe that is encased in an infinitely large torus, such that something would fall forever, while circling around. However, this image is not absolutely necessary for the solution.
In quantum field theory, it is implied that the fields occupy the universe, equally, and are equally distributed throughout. The fields never move in this universe. That is, they are static. Okay, hard to quantify when field theory is point-oriented, but nonetheless.
So the air molecules in your universe are just very large special bosons, which are captured within the 'net' of a corresponding field. This field, like every other field, fills your infinite universe and is static. In terms of the torus, it 'fills' the torus and defines its shape. Think in terms of this 'field' making the torus 'solid' or 'frozen', as an allegory. Everything moves in this 'solid' (field). The air molecule bosons can not move within this 'solid' stationary field, as there is no mechanism for their movement. They are a field unto themselves, independent of the other fields that are responsible for movement (gravity, mass, the Higgs boson, electromagnetism, the strong and weak fields, etc.) However, the independence is not absolute. These molecules also contain Higgs bosons on steroids, which therefore add 'mass' effects (inertia), and thus air resistance for terminal velocity.
However, the theory behind this would require a physics textbook much, much thicker than the one we have today. One in which Einstein was but a footnote. It posits a boson and a field which, frankly, we haven't even conjectured.
The fact that these bosons are uniformly distributed, explains why there is no increasing pressure. These bosons, as I stated, do not interact with gravity nor do the molecules contain any bosons that DO interact with gravity.
**Edit**
In this scenario, I envision your 'islands' to be like asteroids, which would have their own slight gravity, but the movement of everything around the torus would not be due to gravity, but some rotational force, like a particle in a toroidal magnetic field. Again, another boson and another field, apart from gravity.
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So I have a super-Earth that has 2 moons. Moon 1 is a bit smaller than our moon, and has an orbital period of 19.25 earth days. Moon 2 is larger than our moon and has an orbital period of 147.15 days. A year on the planet itself is about 708.5 days (similar to Mars, actually) if it helps. I was thinking a lunar calendar would be easiest, but I'm not sure entirely on how to set it up. Would it follow the first moon or the second moon? How long would the weeks/months be? I've been entertaining a few ideas, but I'm not sure what would make sense, so I'm hoping you guys could help.
If I've missed anything, or if this isnt the right place for this question, please let me know :)
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~~Two~~Three ideas: i) a specific one (orbital resonance) ~~and~~ ii) a more general one (with the calendar itself), **and iii) a play around with a possible calendar**
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An interesting idea to explore is both satellites to be in some kind of **[orbital resonance](https://en.m.wikipedia.org/wiki/Orbital_resonance)**, meaning that the periods of both moons are related by a simple arithmetical ratio (1:2, 2:3, 2:5, etc.).
Said ratio is not *necessarily* exact at every point in time, but in the long term. The periods you suggest *could* be compatible with a 1:7 or 1:8 resonance, if such a configuration is stable (I don't know).
The phenomenon is pretty common in the solar system and has been observed between exoplanets too.
For example, you could have long and short months. The former could look more like seasons and/or the latter could resemble weeks, it's up to you.
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Anyway, with the periods you suggest, **your year could be made of** five long months and every long month made of seven or eight short ones. The ancients tended to have little problem with months or years having variable lengths, as long they remained stable in the long term and periods were divided in an integer number sub periods (this integer number could vary —usually by one—from one super period to the next). Your five "long months" are slightly (about 27 days) longer than a year, meaning that you'll need a four-long month-year every five regular years or so.
Re: the **naming** of the months, bear in mind that the word *month* itself derives from Moon (just as in other languages), so you can get as creative as you wish to name them (actually, I'd advise against calling them months or weeks, except maybe when explaining the concept). Proper names of long months could be aligned to an adapted set of seasons. Short month names could be ok with numerals (something like "the fifth *shimi* of the *borth* of Sommerish.)
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**Update:** There's a proposed calendar:
Let's stick to the name ***borth*** for the long month and ***shimi*** for the short month in the following.
It turns out that the lengths of your year and Moon 2 cycle (*borth*) make for a nice ancient-looking lunar calendar. Specifically, 27 solar years ($27\times708.5=19129.5\,$d) correspond to exactly 130 borths ($130\times147.15=19129.5\,$d.)
This allows to build a stable 27-yr cycle of alternating 4- and 5-*borth* years. Namely one *short* (4-*borth*) year every 4 or 5 long (5-*borth*) years. For example:
* 5 long years ($5\times5=25$ *borths*)
* 1 short year ($4$ *borths*)
* 4 long years ($4\times5=20$ *borths*)
* 1 short year ($4$ *borths*)
* 4 long years ($4\times5=20$ *borths*)
* 1 short year ($4$ *borths*)
* 5 long years ($5\times5=25$ *borths*)
* 1 short year ($4$ *borths*)
* 4 long years ($4\times5=20$ *borths*)
* 1 short year ($4$ *borths*)
This totals exactly $25+4+20+4+20+4+25+4+20+4=130$ *borths* and $5+1+4+1+4+1+5+1+4+1=27$ years.
Assuming a circular orbit (equal season length) and arbitrarily choosing the Winter Solstice (just because) as a reference point, the following figure illustrates a possible resulting lunar calendar. Each row is a year, with each *borth* in a different color. (Dark) red is the 5th *borth* in the year, and can be seen not to occur in every year (sorry for the size).
[](https://i.stack.imgur.com/I1JuF.png)
The first *borth* of the year roughly corresponds to winter, the third nearly every year includes the longest day, etc. Hence you can pick names in their language that make reference more or less to seasons.
Your peoples will be celebrating the New Year up to half a *borth* before or after the actual date, but no more than that (this is what happens with lunar calendars).
Unfortunately, the *shimi* doesn't fit so nicely with the other two cycles: The *shimi*-year cycle would take 77 years, and the *shimi-borth* cycle is even longer, it would take thousands of years for all the three to repeat exactly. My advice here is to look at what we (contemporary folks) do with weeks and months: just choose to what *borth* a *shimi* belongs if it overlaps with two of them and call them using ordinal numerals. Just as some call it the first week of August starting on July 28, You'll have the 1st through the 8th *shimi* of every *borth* and everyone will get it.
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The simple answer is to do a calendar for both moons and then choose the lunar year that fits closest with the solar one. For longer ages you can have it as the time between a double eclipse (where both moons line up with the sun).
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The most important thing to recognize is that there is no one best answer. Different societies will have different calendars, just as they have on Earth. If your planet has a global industrial civilization like ours, then it's reasonable to assume that one calendar has become dominant, but it's *not* reasonable to assume that the dominant calendar is the most sensible one. There are a lot of accidents in history.
If your setting is pre-industrial then you have a great opportunity for different societies to have different choices about which moon, if any, drives the calendar.
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**This question already has an answer here**:
[Can I have a planetary liquid or gas ring system?](/questions/40564/can-i-have-a-planetary-liquid-or-gas-ring-system)
(1 answer)
Closed 6 years ago.
I have been reading through Larry Niven's The Integral Trees, which concerns a gas ring around a neutron star with a habitable center that humans became stranded on., The atmosphere of which was stripped from a nearby gas giant. I was wondering if such a gas ring could exist around a world that is just like earth aside from there being no moon.
How could this come about? I was thinking a series of ice comet impacts could have blown part of the atmosphere away from the planet where it became locked into orbit, meanwhile the planet's atmosphere was replenished due to the water from the comets.
This does seem unlikely but thought I would ask.
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Mr. Niven's book allowed us to suspend our disbelief because of the gravitational pull of the neutron star. An horrendous amount of matter could be held in orbit around the star — enough to permit the idea of a habitable jelly-filled donut with the star at the center.
Regrettably, you have two really big cons for a planet the size of earth to have such a thing.
1. **We're probably not be big enough.** A simple gas within the ring would simply bubble off into space no matter how much there was. Give the ring enough mass to hold the atmosphere together (you know, like a jelly donut...) and you might have enough competing gravity to simply yank the ring to the ground. That's why the neutron star was such a brilliant idea. There was so much gravity in play the ring was believable.
2. The bigger problem, however, was one Mr. Niven didn't need to worry about: **the Van Allen Radiation Belts** (why? Because (a) a neutron star's magnetosphere is massive and (b) a neutron star isn't spitting out solar wind like our boring G-type star). That protective aspect of our magnetosphere permits life on Earth at all. Those belts are a whole lot closer to the Earth than the moon, and a whole lot closer than would permit a habitable ring system. This is where I just ache to say it, but without those rings, you can have all the atmosphere you want and the ring still won't be habitable.
**HOWEVER** Please do not give up on the idea! I believe you can overcome the problems with some adjustments to your planet.
* **Make your planet larger than earth.** Indeed, make it as large as astonomers believe a habitable world can be. The larger the world, the more substantial the ring system, and the larger the radiation belts.
* **Modify the core** such that a stronger magnetic field is generated. Make it more dense, or a higher percentage of iron, or inject the core with an unusually high oxygen component to induce greater ferrousnessness... ness... Or have the core spin faster (which would even be believable with a larger world). Anything to justify a larger magnetic field.
* Finally, you might consider **really dense "rocks" as part of your ring.** Something to exert a bit o' gravity to hold the ring together and keep the atmosphere from bubbling off into space. Make the rocks magnetically repellant so they create a shield around the jelly donut with the atmosphere at the center.
And if none of that works, consider a habitable moon around a gas giant sporting a habitable ring between the planet and the moon.
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Nope. Gas torii are real things (there's one around Jupiter created by Io, and Enceladus produces one around Saturn), but they are wispy things. They are the result of gas being ejected or stripped from an orbiting body, so right away we can say that no such thing could exist around an Earth with no moon, because you need the moon to create the ring! Stripping gas from a moon produces such a ring because the individual gas particles remain in orbit around the primary, pretty close to the orbit they started in--that being the orbit of the moon itself!--with the relatively minor perturbations caused by whatever stripped them from the moon causing them to spread out into a torus.
There is, however, no restoring force holding those particles together as a coherent ring against internal pressure. They persist only due to a combination of being so thin that any individual gas particle is highly likely to complete a whole orbit without actually bumping into any other gas particle, and being continually replenished by the source moon. If a ring were thick enough to have noticeable pressure in the middle, it would simply blow itself apart.
Note that Niven's Smoke Ring is fed by the continual loss of gas from Goldblatt's World, which is stripped off by Voy's (the neutron star's) tides. It takes a *huge* continuous input of new gas to maintain it. Even so, the Smoke Ring is not particularly plausible itself. Niven gets away with it because the story is good, the Rule of Cool is in operation, and the environment is exotic enough that the average reader can't immediately recognize it as implausible. After all, who knows what can happen in the extreme environment around a neutron star stripping gas from a close gas giant? In reality, what should happen is that you get a hot, violent accretion disk, which spirals inwards due to loss of energy to internal friction from tidal shear--not a cozy, habitable Smoke Ring at all! Try to put it around an Earthlike planet instead, and familiarity kills your suspension of disbelief.
You could, however, go with an *artificial* gas torus, held in by a thin, solid, artificial membrane, with active stationkeeping. That's the approach taken by the Orion's Arm worldbuilding project, for example.
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Small gas cloud of near atmospheric pressure in vacuum dissipates almost instantly. Why Niven's torus does not? Even though it is huge, it's self-gravitation is too weak to hold it together - gas has low density. It is held together by tidal forces from neutron star.
A planet would be several orders of magnitude lighter than star, and it's tidal forces would be accordingly smaller. So it would be able to hold torus with 1/1000 pressure of Niven's torus at best.
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A gas ring is possible, but would be most likely in a highly reactive environment. Perhaps caused by high levels of meteoritic bombardment, extreme volcanism or similar. A major problem would be reactive elements such as oxygen reacting with other elements in the vicinity especially hydrogen. So yes to the gas ring but no to an oxygen rich gas ring, unless you can invent some form of special pleading.
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After playing some [HyperRogue](http://tvtropes.org/pmwiki/pmwiki.php/VideoGame/HyperRogue), I got interested in the use of [hyperbolic geometry](https://en.wikipedia.org/wiki/Hyperbolic_geometry) in WorldBuilding, in particular how an area grows exponentially with respect to its radius.
Let's say that the universe is a [hyperbolic space](https://en.wikipedia.org/wiki/Hyperbolic_space). The world itself is a disc with a radius of 30 miles and an area with 196.9 million square miles. This would mean that you can get anywhere within an hour if you travel in a straight line at 60 mi/hr, and the area is as large as the surface area of our whole entire earth!
This world is necessarily non-euclidean, of course, since it has negative curvature. The angles of triangles will add up to less than 180 degrees, for example. It will appear euclidean at sufficiently small scales though (the angles of the triangles will add up to only slightly less than 180 degrees). It will be noticeable at large scales (the sum of a triangles angles will be close to 0 degrees).
My question is, at what scales will the negative curvature of the space be noticeable to humans? Will the non-euclidean geometry only be relevant to a world traveler, or would an artist have to be familiar with it while painting, or somewhere in between? (If you wish to add flavor to your answer, you can present it as problems for the *flat space society*, which denies the reality of non-euclidean geometry).
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Your answer depends on what is meant by “notice”.
Consider a parking lot. Perhaps a pedestrian won’t see the curvature by eye as he walks through it. But the contractor who paves it will consume some amount of material, and his tolerance in *that* depends on the accuracy and uniformity of his paving technique. Maybe ±half a wheelbarrow of concrete will cause concern; maybe differences in a truckload or two are chalked up to the crew’s raking technique and go unremarked.
You should make a chart (program a spreadsheet) showing the ratio of area to radius, percentage difference from Euclid's, and absolute difference; for patches of different sizes in a logarithmic progression. Another pair of columns shows the relative and absolute difference for expected lengths of the sides of a triangle, for each patch size.
Then, use this chart to decide whether someone will notice based on **specific context** of the activity.
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Using [this formula](https://en.wikipedia.org/wiki/Hyperbolic_geometry#Circles_and_disks) we can calculate the curvature $$K \approx -0.313339 \text{ per mi}^2$$
Using this, we can the radius of a Euclidean disk v.s. a disk in this world.
```
Area Euclidean Radius Actual Radius
---------------- ------------------ ---------------
1 mi^2 0.56 mi 0.56 mi
10 mi^2 1.78 mi 1.72 mi
100 mi^2 5.64 mi 4.42 mi
1000 mi^2 17.84 mi 8.26 mi
10000 mi^2 56.42 mi 12.34 mi
100000 mi^2 178.41 mi 16.44 mi
1000000 mi^2 564.19 mi 20.56 mi
196900000 mi^2 7916.77 mi 30.00 mi
```
This means that over the size of a building, distortion will not be noticeable. In a small town, probably only builders will notice. In a small city, everyone will start to notice, but it will still be mostly Euclidean. In a bigger city, the curvature will be quite noticeable, and people will have to take into account if they do not want to get lost. At the size of countries, you will need to follow a navigation system very carefully if you want to get to the right place, and it will very non-euclidean.
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A follow-up to my previous question-barrage:
[Properties of magnetically confined plasma shielding](https://worldbuilding.stackexchange.com/questions/75994/properties-of-magnetically-confined-plasma-shielding)
After some of the feedback, I'm splitting it into several smaller questions.
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In the world I'm building up for a game, one of the factions have magnetically confined plasma shielding technology. I'm changing it up and making the shield an active defense, rather than a passive barrier as most forms of science fiction use them. The way they're defined, the heat from this plasma would dissipate quickly and would likely cook the hull and crew/pilot if the temperature could be maintained for an extended period of time.
Not to mention the other effects:
* The energy emitted by the shield would saturate the EM sensors, blinding the ship's instruments to all but higher frequency active scans.
* I imagine this being fairly bright and/or obscuring to the pilot's vision.
* The shield would block fire in both directions and may even make thrusters useless while active.
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**How it works**
The plasma is stored in a magnetic bottle and kept at high temperature. The gases used for the plasma are the byproducts of the ship's fusion reactor (so anything between helium and iron on the periodic table,) meaning it passively replenishes as the ship's reactor is running. The plasma is vented through a series of ports around the hull then confined in a magnetic field to enclose the ship. The shield lasts up to a few seconds and gives the ship protection to most weapons.
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So, what I'm trying to figure out is what this shield would actually look like. Would it look like a miniature star in the shape of the ship's magnetic field? Or would it more resemble a glowing cloud around the ship?
Would the pilot simply see a blinding light from all directions outside their ship?
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The radiance will be very bright. Stefan-Boltzmann law applies to plasmas in thermal equilibrium, and for 10,000K gives us 567,000,000 watts radiation power for every square meter shield surface. By 100,000K it's 5,670,000,000,000 Five freaking terawatt on each square meter. It increases 10000fold for every 10fold increase in temperature.
Altough your engineers could be able to help a little, (who said it has to be in equilibrium) a realistic plasma shield dense enough to have meaningful effect on material projectiles would shine like sun.
Your pilot will not sit behind an armorglass window. He will be in the well armored, closed bridge, and follow the action on screens. Before shield activation armored doors will cover the external cameras, and fire control will be accomplished by X-ray LADARS and computerized extrapolation.
WARNING: I never said that such a shield will work in reality. Even fusion reactors proposed so far are far from the required power, and no calculations were made about the magnetic confinement.
Edit: yes, it would look like a small, very bright star. But with naked eye, simple telescope or camera you wouldn't be able to see it's shape. It is too blinding for this.
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[](https://i.stack.imgur.com/MRshF.jpg)
The shield would probably be shaped like ferrofluid covering the ship with magnetic spikes. Check [this amusingly narrated video that shows some detail features of ferrofluid spikes](https://www.youtube.com/watch?v=L8cCvAITGWM) I've not seen elsewhere.
The shield would not be a round "bubble" but would flow along the contours of your ship, especially along any sharp protruding edges:
[](https://i.stack.imgur.com/xLFkl.gif)
Not to mention it is damn sexy and I have never seen anyone use this shape for shields before, so it might be a unique design for your game.
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A magnetic bottle will do a lot in stopping particulate radiation from the plasma from damaging the ship itself, but you will need to come up with something to stop the ship being damaged by the EM radiation being emitted from the plasma.
A plasma kept at high enough temperatures will - as previous replies have mentioned - basically look like the entire ship is aflame, or a star. However, this depends on the temperature of the plasma itself, the color and spectrum of the emission will be identifiable from a combination of the Stefan-Boltzmann laws and the Wein Displacement laws (as an interesting meta, this could be used by an attacker to find the peak temp of the defensive plasma).
Radiation from the plasma will not just be limited to the visible spectrum, however, and - even in a vacuum - can cause a huge amount of damage to the defending ship's external hull through infra-red emission.
What is this shield used for? If it is for repelling solid slug ammunition - whose offensive capabilities rely on sheer kinetic energy - it's doubtful this would be stopped by a superheated plasma. Even if it were to be stopped, the resulting momentum transfer would be incurred to the plasma itself. If you can counter momentum change of the plasma with the magnetic bottles, then it behooves that the magnetic bottle *itself* is going to be a more effective shield.
The best application for such a shield would be for dissipating harmful EM fields. As plasmas are extremely high conductors, an EM wave would be critically damped by such a volume of plasma through excitation of plasma currents.
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So I created this thing called 'eye clusters', which makes a human or animal start to develop eyes on random parts of its body. The eyes can't see or blink. Would something like this be possible(maybe without the use of magic)? I was thinking that whatever makes up the eye begins to form in wounds or pores of a creatures flesh? Also, could infected animals transfer the disease by biting or being bitten?
[Answer]
Here you go.
[](https://i.stack.imgur.com/Z8pUK.jpg)
I found this image on reddit, but here is an article describing how these flies come to have eyes growing all over them.
<https://clarionfoundation.wordpress.com/2011/03/10/spec-tech-more-monsters-or-the-beast-with-a-million-eyes/>
Organisms have "homeotic" genes which kick off the development of organs. If you cause expression of one of these genes at a site, it kicks off development of the organ at that site. This fly had the gene to kick off eye development plugged in next to the one to kick off leg development - so eyes for legs.
Your eyes could be infectious cancers like the poor Tasmanian devils get.
[](https://i.stack.imgur.com/QgMly.jpg)
From <http://www.bbc.co.uk/news/science-environment-17062091>. This is the least horrific of the images "Tasmanian devil cancer" gave me. It is a contagious cancer. Tasmanian devils fight and bite each other, of course, and they are immunologically so close to one another that cancer cells dislodged from one can take root in the wounds of another and grow.
If you had a cancer cell that expressed the eye initiation gene, the cancer would make an eye instead of a worthless tumor. If you had a contagious cancer like the devils, or a virally driven cancer (like cervical cancer) it could be transmissible. Crazy, but not magic crazy.
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Yes. The [Ophiocordyceps unilateralis](https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) is a fungus. It takes over the brain functions of its host, leading it to its inevitable death. While doing so it creates spiny growths on the body.
Another is [Green-banded broodsac](https://en.wikipedia.org/wiki/Green-banded_broodsac). Broodsacs are parasites that take over the eyes of their host. They tend to flash brightly, attracting the attention of the natural predators of their host. They wish to be eaten so they can get into the larger predator.
Either changes the look of their hosts. I guess eye like growths are possible. Perhaps it's to attracts the attention of other animals or scare them away. Maybe the main predator refuses to attack within sight. Thus growing fake eyes reduces the chance of attack of their host.
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I have seen from various questions here (and from my research), that a Pangaea-like supercontinent would be very dry, with lots of deserts, since rainclouds couldn't travel a great distance inland.
However, I am pondering the possibility of worldbuilding a Pangaea-like supercontinent with a higher likelihood of temperate, life-favoring environments, by placing seas inland.
The most extreme example I can give is a donut-shaped supercontinent with an ocean at its center.
By bulding on this extreme example, we could gradually fill the central ocean with earth, but maintaining lots of great seas. These seas would be very large and interconnected between themselves, so that they would never dry.
For example, the Black Sea is a large sea connected with the Mediterranean Sea, which in turn is connected with the Atlantic Ocean. Multiply this phenomenum the number of times you wish, in order to create a vast network of large seas and you get the picture of what I'm getting at.
Would this produce the desired effect of creating a supercontinent with more mild climates?
*Note: For this question's purposes, let's assume the majority of the landmass is located on equatorial and temperate latitudes, in an Earth-like planet.*
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Allow me to offer clarity to this mistaken view: Supercontinents do NOT need to be all desert.
[](https://i.stack.imgur.com/SxWdv.jpg)
What folks typically mean is that Supercontinents tend to be dryer in the middle. What that means is that, as rainclouds flow from the sea inland, they'll drop all their rain closer to the coasts. This goes true for most continents, though: in North America, forests line the coasts, and prairies and deserts are nestled in the center. In Asia, there's a desert in the middle of the continent northwards of the Himalayas. Heck, Australia is a desert surrounded by shrub forests.
The key to understanding this is geography and climate.
[](https://i.stack.imgur.com/Ll8e2.jpg)
Here's a diagram of how winds work on a rotating planet (let's call it Earth, for simplicity's sake). As you can see, there are places where wind flows to and away from, due to the convection of air currents. Where winds tend to flow towards, there'll be greater chances of rain, and thus forests. Where the wind flows away, there'll be less rain, and therefore more deserts. You can see this in the simulated image of Pangea above. even though it's all one continent, there's a clear band of forests dividing the desert where the equator roughly is.
In addition, whenever rain hits a mountain face, there will be a rain shadow. The rains will all be deposited on the windward side of the mountain, whereas the opposite side will be considerably dryer. The best example of this is the Himalayas; the Monsoons of India are all bottled up by the mountains, which leaves the Gobi Desert to the north dry and barren.
[](https://i.stack.imgur.com/9s5LC.png)
So ultimately this is what determines your world's climate. It depends on the shape of the land, and how the winds hit it. Even if all the continents are together in one great landmass, it's rarely so simple as it seems. If you can determine where the mountains and lakes exist, then that'll determine the deserts and forests.
Hope this helps, I'd love to help more if ya need it!
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So in the process of creating my world, I came across a question that I could not find the answer to. **When do you decide that a nation is a City-State, a Kingdom, or an Empire?**
I am going to start by saying that any small settlement or town that is not at least a "City-State" (ie, with an army and a local government of some kind) are not relevant to this question.
Throughout history not all City-States had Kings, but some did. Some Kingdoms only had a single city in them, and some Empires were only a single Kingdom.
**So where do you draw these lines? Are these definitions arbitrary?**
*What makes a Kingdom a Kingdom and not a City-State or an Empire? etc.*
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Dictionary definitions:
City-State:
>
> a city that with its surrounding territory forms an independent state
>
>
>
Kingdom:
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> 1. a country, state, or territory ruled by a king or queen.
> 2. a realm associated with or regarded as being under the control of a
> particular person or thing.
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>
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Empire:
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> an extensive group of states or countries under a single supreme authority, formerly especially an emperor or empress.
>
>
>
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But these don't hold water. Here are some examples:
There are [The Ten City-Kingdoms of Cyprus](https://en.wikipedia.org/wiki/Ten_city-kingdoms_of_Cyprus) which are essentially City-States but called Kingdoms.
There is the [Neo-Sumerian Empire](https://en.wikipedia.org/wiki/Third_Dynasty_of_Ur) which was basically a City-State.
And [The Holy Roman Empire](https://en.wikipedia.org/wiki/Holy_Roman_Empire) which Voltaire himself famously claimed was "neither holy, nor roman, nor an empire".
*So, What gives?*
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The categories "city state", "kingdom" and "empire" are somewhat arbitrary, and depend (1) on what the state called itself and (2) on how it was categorized by later historians.
Let's look first at empires.
The archetypal empire was of course the Roman Empire. In Roman Latin, *Imperium Romanum* simply means "Roman power"; it was the expression used to designate not the state, but the territory over which Roman power prevailed. The state was *res publica populi Romani*, the common-wealth of the Roman people; the person whom we call "emperor" was, from a purely legal point of view, [just another citizen](https://en.wikipedia.org/wiki/Principate) who happened to occupy three key positions: he was *princeps Senatûs* (speaker of the Senate, thus having legislative initiative), he had *[tribunicia potestas](https://en.wikipedia.org/wiki/Tribune_of_the_Plebs#Erosion_of_the_tribunician_power_at_the_end_of_the_Republic) majus* (great power of a tribune of the people, so that he could veto any bill he didn't like and his person was inviolable), and he was *imperator* (commander in chief of the army). Of those, the most important was his position as perpetual tribune of the people, and when we say that for example Trajan became emperor on 27 January 98 CE, what we mean is that at that date the Senate gave him the perpetual and greater power of a tribune of the people. It was only in the late 3rd century CE, under Diocletian, that the position of an "emperor" [became a legal reality](https://en.wikipedia.org/wiki/Dominate) and the emperor stopped being just another citizen and became officially the supreme ruler of the state.
In the early Middle Ages there was only one emperor in Christendom, namely the emperor in Constantinople. The title was revived in the West for [Charlemagne](https://en.wikipedia.org/wiki/Charlemagne) by Pope [Leo III](https://en.wikipedia.org/wiki/Pope_Leo_III) in 799 CE; at that time the pope had a spot of trouble with the populace of Rome and, as he was seeking the favor of the king of the Franks, had the bright idea of bestowing upon him a title equivalent to the *basileus* in Constantinople. From that point onward there was one emperor in the west and one in the east; when Constantinople fell to the Ottomans in 1453, the ruler of the Ottomans inherited the designation *emperor* in the eyes of western Europe.
Sometimes rulers titled themselves emperors to make a political statement; for example, the Grand Duke Ivan IV "the Terrible" of Moscow titled himself emperor ("[tsar](https://en.wikipedia.org/wiki/Tsardom_of_Russia)" in Russian, from Cesar) to make it clear that he saw his state as the legitimate heir of the Christian empire of Constantinople. Sometimes rulers simply took the title *emperor* simply because it was more prestigious than a mere *king* (and was higher in the medieval order of precedence); for example, there was nothing particularly imperial about the [Empire of Germany](https://en.wikipedia.org/wiki/German_Empire) or the Empire of Japan, which were ordinary nation-states, at least in the beginning. Only in the later phases of existence of those states did they try to build actual empires—and they both failed spectacularly. Sometimes the empire in question was not even a state; for example, the [British Empire](https://en.wikipedia.org/wiki/British_Empire) was not a state in any meaningful sense, the various components having different laws, different currencies and verious degrees of international recognition. The British monarchs were not emperors of the British Empire, they were kings of queens of the United Kingdom and their various dominions, and emperors or empresses *of India*. Sometimes we call a state an empire because it was large and multi-ethnic; the best example is the Chinese Empire. Or we use the word emperor as the best way to translate a native title; for example, the emperor of Persia was actually *[shâhân shâh](https://en.wikipedia.org/wiki/King_of_Kings)*, king of kings, but *emperor* is more easily understood.
A *kingdom* is simply a monarchical state ruled by a king. Not all monarchies are kingdoms; in the Middle Ages there was an [order or precedence](https://en.wikipedia.org/wiki/Order_of_precedence_in_England_and_Wales), with the position of emperor as the most prestigious, then king, then prince, then grand duke, then duke, etc. Some states were kingdoms, some were principalities, some were grand duchies, some were duchies etc. depending on where in that order of precedence they stood. Sometimes a ruler was *king* in his country, but a mere *prince* or *duke* in foreign relations, for example [Frederick William I of Prussia](https://en.wikipedia.org/wiki/Frederick_William_I_of_Prussia) (the father of Frederick the Great) was king *in Prussia*, but *elector* of Brandenburg elsewhere.
City-states are easier. A state is said to be a city state if it is or was small, and it calls or called itself a city. Athens, Corinth and Sparta called themselves cities, *[poleis](https://en.wikipedia.org/wiki/Polis)*, so they are city-states, although Sparta ruled over a reasonably large territory and at one point Athens had a rudimentary empire. The Free Hanseatic cities of [Bremen](https://en.wikipedia.org/wiki/Bremen_(state)) and [Hamburg](https://en.wikipedia.org/wiki/Hamburg) are city-states within the German federation. [Singapore](https://en.wikipedia.org/wiki/Singapore) is a city-state in Asia.
To summarize:
* A state is called an *empire* because:
+ It calls (or called) itself an empire; example: Japan, French Empire (1st and 2nd), German Empire, Roman empire (from the 4 century onward).
+ In the case of states no longer in existence: it was large and multi-ethnic; examples: Roman empire, Chinese empire, Russian empire.
+ Quite often the two reasons co-exist.
* Some structures called empires were not actually states; examples: British Empire, Holy Roman Empire. They are called empires because they called themselves empires.
* The actual powers of the emperor varied widely; the *elected* emperor of the HRE had little direct power, whereas the self-made Napoleon I, Emperor of French, was essentially all-powerful.
* A state is called a kingdom if it calls or called itself a kingdom, or the best translation for the foreign title of the ruler of that state is "king".
* Sometimes we use different translations, such as prince or duke, or use the foreign title as such--tyrant, pharaoh, voyvode, maharaja, sultan, khan.
* Some monarchies use lesser titles--Principality, Grand Duchy, Duchy, etc. In particular, most of the states which made up the HRE were not called kingdoms. For example, the Grand Duchy of Luxemburg, the Duchy of Bavaria, the Margraviate of Brandenburg (a *[margave](https://en.wikipedia.org/wiki/Margrave)* is the ruler of a border duchy), the Landgraviate of Thüringen, the Palatinate of Burgundy, the County of Jülich; in fact, for a long time the only Kingdom in the HRE was the Kingdom of Bohemia; only later was Austria elevate from Duchy to Kingdom.
* A city-state is a small state which (usually) calls itself a city.
[Answer]
Empires, kingdoms, and city-states are entirely modern concepts of the modern historical sciences.
The states in your examples were at the time not styled in these categories. Let me emphasize 3 aspects:
* A distinction between various levels of sovereigns became necessary when large powers started to conquer huge swaths of territory that they could not possibly micromanage without replacing the local administration. They would call themselves something like "Ruler of rulers", which has variously been interpreted as "Emperor" in modern historiography (see [nəgusä nägäst](https://en.wikipedia.org/wiki/Emperor_of_Ethiopia), [Shahanshah](https://en.wikipedia.org/wiki/Shahanshah)). The Western concepts of Emperor ("Imperator", "Tsar", "Kaiser", ...), however, are corruptions of ancient roman names (Caesar) or honorific titles (Imperator) that came to be used as hereditary titles (this also happened to other roman rank titles such as Princeps, Judex, ...). The Japanese and the Chinese Imperial titles (Tenno and [Huángdì](https://en.wikipedia.org/wiki/Emperor_of_China)) are still different; the Chinese case, [Huángdì](https://en.wikipedia.org/wiki/Emperor_of_China), for instance, is a contraction of two earlier sovereign titles.
* Diplomatically it carried meaning whether two monarchs were assigned titles of the same level. The Byzantine era is particularly confusing. At some point, they start to use the older Greek title "Basileos" ("ruler", "king") for their Imperatores. At this point, they stop applying this title to lesser kings (such as the contemporary Germanic rulers, thereafter only referred to with the Latin loan word "rex", "regas" (also meaning "ruler", "king") while "Basileos" is also used for the Persian Shahanshah and the Axumite nəgusä nägäst. See [here](https://en.wikipedia.org/wiki/Basileus#Romans_and_Byzantines).
* And as @AlexP mentioned, the names differ widely throughout history; the ruler of the Neo Sumerian Empire would have called himself LUGAL; the 10 "kingdoms" of Cyprus were called that by the Assyrians (who would again have used the cuneiform symbol LUGAL but pronounced it differently) but were Greek and Phoenician states of various sizes whose rulers would have called themselves something like Basileos (Greek) or MLQ (Phoenician). Modern historians would translate all three terms, MLQ, Basileos, LUGAL as "king" but this is obviously not very accurate.
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[Question]
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In OTL, [Takeda Katsuyoui](https://en.wikipedia.org/wiki/Takeda_Katsuyori), son of [Takeda Shingen](https://www.britannica.com/biography/Takeda-Shingen) leads his clan to battle against [Oda Nobunaga](https://infogalactic.com/info/Oda_Nobunaga) and [Tokugawa Ieyasu](https://infogalactic.com/info/Tokugawa_Ieyasu) over the objections of his father's "24 Generals" (high ranking military advisors and war leaders). While the Takeda's were in a strategic location and capable of fending off potential challengers for the unification of Japan, it was always clear to Takeda Shingen that they were only strong enough to maintain the balance of power, and could be defeated by the combined might of other clans, or if they threw in with another clan, they themselves would be subsequently defeated.
However, Takeda Katsuyoui was rash and ambitious, and at the [Battle of Nagashino](https://infogalactic.com/info/Battle_of_Nagashino), led waves of his cavalry and infantry against the forces of Oda Nobunaga and Tokugawa Ieyasu, who were sheltered behind wooden palisades and shot the oncoming forces to pieces with volley fire from their matchlocks. Cinemaphiles may watch a stunning recreation of the battle at the end of the film *[Kagemusha](http://www.imdb.com/title/tt0080979/)*.
[](https://i.stack.imgur.com/JivhE.jpg)
*Battlefield and force layout OTL*
So in an alternative universe, Takeda Katsuyoui still wants to defeat the forces of Oda Nobunaga and Tokugawa Ieyasu at Nagashino, but is willing to listen to suggestions by his "24 Generals" once he sees the wooden palisades and gunners arrayed before him. What changes to his strategy (including changes to his force composition and equipment, remembering this is 16th century Japan) should he make to defeat the enemy and give the Takeda clan the opening to unify Japan and take the Shogunate? As the daimyo of one of the most powerful clans in Japan, he is not going to take "no" or "retreat" for an answer, so be prepared for ritual suicide if that is your solution....
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This battle can be compared in some ways to a reverse of the classic bypass of the Maginot Line by the Germans at the beginning of WWII. Oda and Tokugawa have their forces nicely dug in with wooden barriers in place to protect them and sophisticated (for the time) firearms to kill enemies from a distance as they approach the line. Basically, they have a prepared, fortified position with superior firepower at range.
To defeat them, think the same way the Germans did when faced with the elaborately prepared Maginot Line. Again, it was incredibly well dug in, with basically invulnerable gun emplacements that could totally control the direct approach to the Line. Simply charging at it would have resulted in a catastrophe. The Germans simply flanked the line, went around, and attacked from behind.
To the same extent that an enemy is dug in and prepared, they are also nailed down in one spot. The more dug in they are, the less mobile they are. If they are immobile, you should be MORE mobile (paraphrasing Sun Tzu). There is a story from Israel that before the 1956 war, Moshe Dayan was inspecting his troops at the front line with the Egyptians. They proudly showed him an array of elaborate trenches that they had just spent days digging. Dayan is said to have immediately ordered the men to fill them in, saying (again, paraphrasing) "We are outnumbered 6 to 1. If we stay in one place and wait for them, we will lose. The last thing I want my soldiers to be doing is sitting still; I want them charging forward!"
So, Takeda should do this:
Line up some infantry that are not too fast, but carry banners and polearms and whatnot. Make them look like a bigger force by staggering the formation and tying more banners and whatnot to their packs. This infantry has to be brave, because they have a dangerous assignment: they are going to feint right at the center of the enemy forces where they have their barricades set up. It's even better if he has someone who looks like him with his personal banner on a horse with this group, so the enemy thinks this is the main attack. If he wanted to be really tricky, he would give this guy his own personal armor.
The more mobile elements (Mostly cavalry) set out before this attack launches, use cover of darkness, and bypass the wooden screens, coming at the enemy's flank from the top of your map (I assume that's North?). If he has enough men, he can split his force and have the second group do the same thing from the other flank. This is very risky though: I would probably keep all my cavalry together in one huge mob and count on morale and momentum to keep them rolling forward once they overwhelm the northernmost enemy position.
He still has a very tough fight, but if the main bulk of the enemy have already started firing their guns at the decoy force, they aren't going to want to stop doing that when they hear something going on elsewhere. Plus, the guns of the time put up a lot of smoke, which will add to the time it takes for them to figure out that they are shooting at ghosts. Meanwhile, you have to totally destroy the northernmost group, push forward, and hopefully start a rout before the enemy can react. You move to the next small group with your entire force before they can abandon the now useless firing line emplacements, and if you keep up a very fast pace, you may be able to concentrate your forces against a dispersed enemy and take them out piecemeal.
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Considering that Katsuyori did literally everything wrong in that battle, there are a number of things that he could have done differently.
# Abandon the siege
Facing an army three times your size isn't the best in the first place. If he abandoned the siege and used the superior mobility of his cavalry forces compared to Nobunaga's gunners, Katsuyori could have struck at an easier target.
# Don't play fair
Heavily armored cavalry are most effective when used on an unsuspecting enemy. Attack at dawn before the day the battle actually occured, or even better, attack the enemy camp late in evening the night before.
# Retreat and find cannons
Cannons were around in Japan at that time. At the very least, they could be bought from the Dutch. Retreat and buy some canons. Shattering wooden stockades with cannon then a heavy cavalry charge into the carnage sounds like a good strategy.
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Katsuyoui's main issue was mindset in two manners.
First - Samurai did not use guns, they were a peasant weapon after all. Unfortunately for Katsuyoui, matchlocks proved to be far superior to horses and traditional tactics...gunpowder is a game changer in war.
And Second - Katsuyoui won a battle earlier in a similar setup and he assumed these tactics would work again. Oda on the other hand learned from his earlier defeat and heavily prepared. Katsuyoui made no effort to scout enemy positions and used the same tactics that won earlier for him. Scouting his opposition prior to the attack would have told him his straight charge at a fortification he couldn't breach was a bad idea. Katsuyoui badly underestimated his opponents ability to adapt (If you forgive the example, He figured rock would crush all forgetting his opponent could choose paper) and the effectiveness of their firearms.
The biggest change he could have made was to attack the night prior. June 17th saw a heavy torrential downpour. Oda's forces effectively preserved their gunpowder stocks keeping it dry for the eventual battle on the 18th. There was water on the ground and a muddy environment, however it was ultimately a dry and sunny battle. Had Katsuyoui attacked on the night of the 17th during the heavy downpour, Oda's muskets would have been rendered ineffective as they did not function in the rain. Whether this would have been a win for Takeda forces is another matter to speculate at, but it would have given Takeda's an additional advantage.
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I know how they could have won. Instead of using cavalry, they could have adapted to the fact that they could not use cavalry at that point because of the barrier. I would have sent scouts ahead to take a look at the enemy's position first. Than, I would have had my best men dig tunnels under the cover of darkness. I would also have them attack during the heavy downpour as that would render the guns useless.
A full frontal assault with no knowledge of the enemy puts the entire army at risk. The bastard son of Takeda Shingen basically thought he would win again using the same tactic he had used before. I would have sent my best men equipped with unlit torches, hay, flint, stone, oil and an escort of archers to protect them from the gunners and other Oda troops just in case. Once they reach the wall, they pour oil all around the wood cautiously and with stealth plus placing hay underneath without being seen and than they burn the wall up.
When the wall burns up, this will cause panic, which gives the Takeda troops time to take out as many Oda troops as they can, gunners included. I take down the wall before the downpour. Once the skirmish is done before the downpour, I'd have the Takeda tactically retreat and take cover in the tunnels, hidden. If the Oda and Tokugawa pursue, the Takeda will wait and take them out one by one in the maze of tunnels. If they stay though and decide to attempt to shoot the Takeda soldiers, I would have the Takeda attack during the downpour which would render the guns useless.
My tactic here is basically guerilla warfare, to lure them into a trap. If there are any left over areas of the wooden wall that are breached large enough for cavalry, that's where I would send the best elite Takeda cavalry plus some infantry units to charge in by surprise and BOOM, Oda is defeated along with Tokugawa. I would also use feint movements to trick Oda because he is easy to trick and has been tricked before. He is no god. He is just a man playing god.
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I'm well aware that a Sun-like star is incapable of producing a supernova at the end of its life. However, would removing the core or a fraction of it, trigger an explosion from the star collapsing in on itself? Removing, in this case, means actually taking somewhere else, both the mass and energy that may be present. Would the collapse be violent enough to light a more energetic and runaway fusion reaction or produce antimatter as may be the case with a hypernova?
If an explosion occurs how might it compare to an actual supernova?
Don't worry about the mechanism that removes the core; for the sake of the question I'm only concerned with the effect.
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Let's think about why a supernova happens in a massive star. You probably know that after a star develops an iron core, further nuclear fusion is not possible on a large scale. Yes, you can produce heavier elements via [neutron capture](https://en.wikipedia.org/wiki/Neutron_capture), which indeed happens during supernovae (via the [r-process](https://en.wikipedia.org/wiki/R-process)) and [inside massive stars](https://astronomy.stackexchange.com/a/11888/2153) (via the [s-process](https://en.wikipedia.org/wiki/S-process)), but conditions simply aren't suitable enough to form them at any significant rates inside massive stars, let alone the Sun. Therefore, you no longer have a source of outward pressure in the core (although the outer layers will still be fusing lighter nuclei in [shell-burning](http://www.astro.princeton.edu/~burrows/classes/403/shell.burning.pdf) processes).
Previously, the star was in [hydrostatic equilibrium](http://www.astro.caltech.edu/~george/ay20/Ay20-Lec7x.pdf); the outward pressure balanced the inward gravitational force. However, the inner pressure is now gone - as is the case with your coreless Sun - and so the core begins to collapse. What happens next is a little complex; I'm going to quote from [an answer I wrote on Astronomy](https://astronomy.stackexchange.com/a/18425/2153):
>
> 1. At high enough densities ($\rho\sim10^9\text{ g/cm}^3$), [electron capture](https://en.wikipedia.org/wiki/Electron_capture) becomes important, where a proton and electron combine to form a neutron and an electron neutrino:
> $$e^-+p\to n+\nu\_e$$
> Simultaneously, [beta decay](https://en.wikipedia.org/wiki/Beta_decay) may occur, where a neutron decays to a proton, electron and electron antineutrino:
> $$n\to p+e^-+\bar{\nu}\_e$$
> However, beta decay becomes less important than electron capture at this point.
> 2. Electron capture reduces electron degeneracy pressure in the core, which leads to accelerated core collapse. Degeneracy pressure is important in the cores of many stars, but in extremely massive stars - red supergiants included - it simply isn't enough to stop the collapse.
> 3. At densities below $\sim10^{11}\text{ g/cm}^3$, neutrinos can carry away energy, and the initial burst leaves the star within about ten seconds. However, core collapse quickly leads to much greater densities, and when $\rho\sim4\times10^{11}\text{ g/cm}^3$, neutrinos are trapped. They scatter off nuclei, and transfer energy to electrons. Electron-nuclei scattering is also important, and may be dominant at higher energies.
> 4. At $\rho\sim2.5\times10^{14}\text{ g/cm}^3$, the core undergoes a "bounce", and the supernova explosion fully begins. A shock wave propagates into the outer core, and more neutrinos are produced via electron capture.
> 5. Neutrinos still trapped in/by the stellar remnant are released about ten seconds later. Neutrino pair production, too, leads to rapid cooling. Some of these neutrinos may contribute to a revival of the shockwave.
>
>
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What if we could quickly stop the densities from reaching high enough that electron capture becomes less important, stalling both accretion and the outward rejuvenating burst of neutrinos? That would provide support against further collapse, and stop the outward shockwave from every forming, because there would be no bounce. In fact, we can do this easily in the case of the Sun, given that we should expect to see a lower core density than in massive stars.
Now, those lower densities mean neutrinos are less likely to interact with the outer layers of the star; thus, they should escape, carrying their energy harmlessly away. This should make the bounce weaker, if it happens at all - another reason I'd argue that the supernova may not occur.
Another advantage we may have is that the Sun's core is not degenerate; rather, it is supported by thermal pressure. I suspect this should make it more stable. The analogy I see used a lot, and which I prefer, is that of a thermostat, which was mentioned in the linked notes above. In a star, if the pressure decreases, so does the temperature and fusion rate. The star then collapses a little until it reaches higher densities, increasing fusion rate, temperature and pressure until it is stable once more. I'm guessing that this is what would happen for a coreless Sun. The density would presumably never be high enough for electron capture to occur, and so the shockwave would never happen. You wouldn't have a supernova, because you'd have something to counter the collapse: nuclear fusion.
Here's another little tidbit: electron capture is more likely to happen with free protons than with heavier nuclei (see [Balasi et al. (2015)](https://arxiv.org/abs/1503.08095)), meaning that if you had plenty of heavy metals in your coreless Sun, perhaps electron capture could happen less dramatically, slowing the core collapse and perhaps preventing the bounce.
Finally, I've been debating whether or not I should mention a [helium flash](https://en.wikipedia.org/wiki/Helium_flash). Again, I have no idea how fusion in the coreless Sun would occur as material moved towards the center, but there's a chance you could see brief runaway fusion (similar to what happens in a helium flash) that would then be damped, albeit a reaction of hydrogen fusion, not helium fusion. I'm still not sure how that would affect the possibility of a bounce.
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### Additional references:
* [Balasi et al. (2015)](https://arxiv.org/abs/1503.08095)
* [Janka et al. (2007)](https://arxiv.org/abs/astro-ph/0612072)
* [Mirizzi et al. (2015)](https://arxiv.org/abs/1508.00785)
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[Solar core](https://en.wikipedia.org/wiki/Solar_core) is 34% of the Sun mass, so sun will continue to be a star, at some point after the event. It will implode and probably intensify the processes compared to previous conditions and to a comparable star with 66% of the Sun mass. Dynamics of collapsing processes, may lead to ejection of plasma, so it definitely not recommended for planets like our at current state of our technological development.
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> The core of the Sun is considered to extend from the center to about 0.2 to 0.25 of solar radius
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$$U = -G\int\_0^R {\frac{(4\pi r^2\rho)(\tfrac{4}{3}\pi r^{3}\rho)}{r}} dr = -G{\frac{16}{3}}\pi^2 \rho^2 \int\_0^R {r^4} dr = -G{\frac{16}{15}}{\pi}^2{\rho}^2 R^5$$
From [Gravitational binding energy](https://en.wikipedia.org/wiki/Gravitational_binding_energy) wiki article, but in this case core is out, so is out 0.25R
$$U = -G\int\_{0.25R}^R {\frac{(4\pi r^2\rho)(\tfrac{4}{3}\pi r^{3}\rho)}{r}} dr = -G{\frac{16}{3}}\pi^2 \rho^2 \int\_{0.25R}^R {r^4} dr = -G{\frac{16}{3}}\pi^2 \rho^2 \cdot \frac{1}{5}(R^5-0.0009765625 \cdot R^5)$$
They assume even distribution for mass, which is definitely not the case, but we will continue assumption farther, let assume that a thing called radius will not change significantly for star with 66% of its original mass (not true but lets hope it is enough true for our purposes)
With these assumptions energy stored as kinetic energy/heat energy/etc as result of this collapse will may be like:
$$ 0.0009765625 \cdot \frac{0.4356 \cdot 3GM^2}{5R} = \text{9.68176538754e+37 J}$$
That is a Lot, even compared to 3.828e+26 J/s which sun produces, according [Sun Fact Sheet](http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html)
* I'm **not** sure in any assumption and calculations here, I'm just try to estimate orders of magnitude of orders of magnitude. Looks like it have potential for nasty things.
The question is -- will it be enough? What happens to supernovas is not because they collapse, collapse itself is consequence of what actually happening, and happening changing the fuel they burn. (I do not posses deep knowledge about the processes there, but this is one of them)
Hydrogen burning is a slow process, if we compare it to other types of thermonuclear reactions, as it can be seen in example with thermonuclear bombs, they do not need such extreme conditions as sun have constantly in the core, and they produce more energy per given mass, then sun does per same mass in same time.
Removing core, have potential to slow down burning, as it contains heavy atoms like maybe carbon which maybe helps to catalyze hydrogen burning.
But this potential energy of collapse will heat hydrogen to higher temperatures and maybe compress it in to more dense state for some amount of time, which may not linearly improve speed of hydrogen burning. Which will lead to expansion of matter, slowing down the reaction and create circumstances to collapse again.
I will not wonder if collapsing/expanding cycles will continue for next million of years. How long it will continue will be question of how good will be that system as oscillator.
During that dance solar ejecta will have place, that is for sure, and it will be spectacular to observe from a safe distance.
Will it act really as supernova - probably not, depends, mmm interesting question. I mean sure not any star will, some stars may really become supernova from that, specially if core removal is done in the way to maximize that probability, but others will not.(basically these who may be supernova in a future they can, who will not, they probably will not)
Will this situation lead to some nasty things happening in the star system in a supernova fashion way of bad and good(depends who and for what uses that). Yes, it probably will have some elements of supernova - energy bursts, plasma bursts etc.
Will it be a apocalypse for star system, for planets probably not, for some one on a planet, probably yes.
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It would probably be the same as a regular supernova.
A supernova is caused by the core of the star suddenly collapsing, which can actually happen for a number of reasons (the most well-known type being related to running out of "fuel" and collapsing under gravity), leaving an empty space which the rest of the star "falls into". This infalling matter collides with other infalling matter, rebounds, and the intense forces from this collision blow the star apart.
The reason why normally only large stars experience supernovas is because only large stars have cores massive enough to undergo this kind of rapid gravitational collapse (the other types of supernova also only happen to large stars, but for different reasons). But if you simply removed the core entirely (I'm assuming you're doing this through some kind of hyperspace method and not physically reaching through the star's outer layers to pluck it out), this wouldn't matter. Even a small star like our Sun could suffer the same effects. Perhaps not quite as intense as a large star's supernova, but still a supernova.
There would be no stellar remnant though (neutron star/black hole), since these are the remains of the collapsed core and this star has none.
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What conditions might make a planet more likely to develop silion based life, the factors I need to kmow are listed below
* Temperature of the planet
* The solvent that they can use in their biology
* The type of star the planet is likely to form around
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Probably extreme cold. Organosilicon compounds are very unstable, so lower temperatures give them the best chance at sticking around long enough to create life. Of course, chemical reactions occur more slowly at lower temperatures, so there needs to be a balance between molecule stability and reaction frequency. There is no perfect temperature where this balance could be struck, but assume that silicon based life would have a **MUCH** slower metabolism and rate of evolution than carbon based life.
Because of the low temperature required, hydrocarbon solvents would be ideal. For example, methane is liquid between -182 and -161 degrees celsius. The problem with using hydrocarbons is that (duh) hydrocarbons contain carbon, making the emergence of silicon based life far less likely.
Liquid hydrogen is your next-best bet, and exists at much lower temperatures (-253 to -240 Celsius). But the problem is that, like methane, liquid hydrogen is non-polar. In order for life to exist in non-polar environments, complex lipids beyond the scope of organosilicon chemistry are required.
It's not ideal, but ammonia is probably the best solvent. It's liquid at somewhat cold temperatures (-33 to -77 C), is polar, and doesn't contain carbon.
The type of star your planet has is less important than the planet's distance from it. For a solar system similar to ours, this planet will be somewhere between earth and mars.
For more info check out this great article on atomic rockets:
<http://www.projectrho.com/public_html/rocket/aliens.php>
EDIT: Another option is fluorosilicones. They are far more stable than silicon-based molecules, but they use carbon as well as silicon to help them stick together. If you wanted something that was technically "Silicone based life", have those lifeforms use fluorosilicones, and stick their planet somewhere so it'll be about 500 degrees celsius.
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The results summarized on [this answer](https://worldbuilding.stackexchange.com/a/44581/885) indicate that it doesn’t look good. Warm Si life needs carbon *too*, and (as quoted there) Freitas points out that the increased temperature tolerance is modest and probably not worth it to to enable Si to out-compete C.
You need some further advantage beyond what we see from the chemestry. Perhaps some element is *missing* (or not bio-available) that carbon-based life needs to get started. E.g. I like the example of fixing nitrogen in a pre-biotic world.
Why would pure carbon life not emerge, simply getting rid of uses of Si, since so many carbon compounds are needed in the side chains? I suppose that once the *essential* kernel gets going (the equivilent of DNA) it will be locked in and can’t be changed. Any further attempt to start new life simply becomes food for existing life.
So, moderatly high temperature, and luck in having a silicon bearing molecule emerge as the successful replicator early on.
The alternative is *cold*. Pure use of si as an analog of familar carbon molecules work at cryogenic temperature using liquid nitrogen as a solvent. Would life emerge with such low energy? Things happen slowly. So make it a red dwarf star that’s stable for many billions of years, and allow life to *take* billions of years to start on a cold planet orbiting a dim star.
If we find such a thing today, and discover the star is 10 billion years old, you need to make sure there us enough dirt to make planets of rock and provide for organic material—elements were cooked up with succeseive generations of stars, so an ancient star can be expected to have less.
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That's an interesting question, since we have absolutely no idea what conditions are ideal for developing even carbon-based life. For instance, for carbon-based life, we would expect something like an atmosphere high in ammonia or other simple nitrogenous compounds(you need some 20-30 distinct proteins for DNA replication) to even have a shot in hell at producing life, yet there is no evidence for this kind of atmosphere existing on earth; based on our current knowledge, it is exceedingly improbable that on an earth-like planet(or any planet really), carbon-based life would arise by chance. Yet, it did. The bottom line is that nobody has any idea what chemistry is likely to produce life.
But why try to use science to answer a question that it cannot answer? The origin of life in your universe could be a mystery in yours as much as it is in ours. Perhaps in your universe, the panspermia theory is correct, and life arose only once, somewhere incredibly far away. Perhaps your silicon-based life was created by carbon-based scientists, whose civilization was eventually destroyed without a trace. Perhaps your universe is a simulation in the mind of a deity. There are so many ways you can go with this.
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Actually you don't have to go to a different star system to find one. The innermost large moon of Jupiter, Io fits the bill. It has subsurface molten sulfur and magma, freezing vacuum surface, an extremely high level of ionizing radiation, and is almost completely devoid of water. As hostile as these conditions appear for carbon water life, you have to look deeper and realize that you are looking an environment with the potential for complex chemical interactions and available energy gradients that might be perfect for silicon based life. Obviously trying to simply plug carbon biochemistry into elements one level lower on the periodic table is not going to work. Anything alive that originated in the seething subsurface witches brew that likely exists on Io would be alien indeed as alien as the little moon appears.
[](https://i.stack.imgur.com/Kdwuq.jpg)
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*Disclaimer*: This question is the third of a new series of questions of mine about *introducing hexapeds to the fauna of my conworld*. There are/will be other questions addressing i.a.: [characteristics](https://worldbuilding.stackexchange.com/questions/56329), ecosystems, [taxonomy](https://worldbuilding.stackexchange.com/questions/56360)
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*Setting*: In my [conworld](https://worldbuilding.stackexchange.com/questions/19788/) the world is divided into two humongous continents, each taking up about half of the total landmass of the planet. Each located at the Northern and Southern poles respectively.
```
1 Equatorial Belt | Saltwater
2 | Saltwater
5 Northern Polar Sea | Saltwater
6 | Sweetwater
```
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*Evolution*: The Beast-of-Burden (further BOB) has six legs and lives predominantly in the northern part of the continent. Its half-dozen legs have given it an advantage in areas where there's lots of uneven and loose ground, as well as more sole-area which helps it stay aloft in marshland.
It is generally agreed upon that features & traits such as mammary glands and live birth can be attributed to convergent evolution. The same goes for its rather long gestation and its multiple young with each birth.
The BOBs live in comparatively small groups of three dozen individuals at most. There doesn't seem to be a predominant alpha male or female and it has been observed that the whole group cares for young.
They're ruminating herbivores that feed mainly on grasses, mosses, bushes, etc.
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**Question**: What (prehistoric) sea-dwelling creature has the BOB likely evolved from? And how could its evolution have looked like?
This question assumes that the hexaped strain of life coevolved with the quadruped strain; for example on different parts of the continent (e.g. the quadrupeds in the south and the hexapeds in the north).
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Can I suggest something along the lines of the [**Queensland Lungfish**](https://en.wikipedia.org/wiki/Queensland_lungfish)
[](https://i.stack.imgur.com/x6EF9.jpg)
If you split the anal fin into two separate fins and move the dorsal fins slightly more forwards, you'll have the ancestor for your BOBs.
Quote from Wikipedia:
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*Fossil records of this group date back 380 million years, around the time when the higher vertebrate classes were beginning to evolve. Fossils of lungfish almost identical to this species have been uncovered in northern New South Wales, indicating that Neoceratodus has remained virtually unchanged for well over 100 million years, making it a living fossil and one of the oldest living vertebrate genera on the planet.*
*It is one of six extant representatives of the ancient air-breathing Dipnoi (lungfishes) that flourished during the Devonian period (about 413–365 million years ago) and is the most primitive surviving member of this lineage. The five other freshwater lungfish species, four in Africa and one in South America, are very different morphologically from N. forsteri. The Queensland lungfish can live for several days out of the water, if it is kept moist, but will not survive total water depletion, unlike its African counterparts.*
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[Answer]
## Six legged creatures showed up about 370 million years ago and looked like frogs
Given that a plan form of six legs is so fundamental to an organism's body shape, this is a very very old feature. Assuming that the evolutionary tree of this world matches the progression in Earth's evolutionary tree, the body plan preference for six limbs over four limbs would need to happen at or before the divergence of Dipnoi (lungfish) from Amphibia (frogs) around 370 million years ago. Let's say that there is a further divergence within Amphibia where some developed four legs and some developed six legs.
Given the age of this divergence, the degree of speciation in four-leggers and six-leggers will be immense. Also, given the age of this feature, there won't be one single species that developed this feature. If there is, they will be long long dead by the time of this story (though it might have gotten lucky and survived unchanged for 350 million years. The nautilus has done something similar). At these ages, four leg species will be globally distributed as will the six leg varieties. 300 million years is just too much time for one phylum to stay completely geologically separated from another. But, just because they are found geographically mixed doesn't mean that in a given location the six leggers won't dominate the four leggers and vice versa.
It is not unreasonable to say that for the six leggers just do better up north and the four leggers do better down south. If there is some geographic isolation (that isn't clear in the provided map) then that should give the six leggers time to fill out more ecological niches at the expense of the four leggers. An example of this kind of domination is on the New Zealand islands. Till humans showed up, birds were dominant.
With the geographic isolation and time scales involved, the evolution of a domesticatable herbivore is highly likely. Progression from small six legged amphibians to lizards then into mammals might proceed nearly the same as here on Earth.
Having six legs also means that this world might see tool wielding griffons with two arms, two legs and two wings. Or birds with arms.
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You're positing a split a *very* long way back. Things like the quadrupedal form and the pentadactyl limb developed so far back you'd almost have to posit another Class entirely to make it reasonable.
Convergent evolution is all very well as an explanation, and happens reasonably frequently in nature, but what you're saying there is that these creatures are known not to be mammals. What are they, then? Saying 'what might this thing have evolved from' is far too broad without more of a description than 'they have six legs and live in small groups'. I'm assuming from the name that they're about cow size and morphology, but is that correct? Are they six legged horses, dog-size cockroaches, snakes with a compensation problem or elephants with a limb surplus?
Assuming these creatures are vertebrates, and therefore chordates, you have an interesting problem regarding the attachment of the third set of limbs. Do you have a second set of scapulae? Something approximating a second pelvis? A swung-cage like structure suspended from reinforced vertebrae developed from the last two or three ribs of something otherwise roughly mammalian?
If they're not chordates as we know them, you have further options. Insects already have six legs, have done so for a very long time, and their main reason for being small is a lack of lungs - the oxygen in our atmosphere isn't sufficiently concentrated to allow them to function. Positing that a large species of insect developed internal lungs of some kind, perhaps by merging bundles of their tracheal tubes and enlarging a couple of their spiracules (giving you an insect with proto-lungs and 'nostrils' on its 'shoulders') would mean that as the oxygen levels dropped, they were able to stay large and perhaps even grow, eating vegetation which the other species of insect were no longer able to consume as effectively. Group size would drop due to availability of food and costliness of raising young, the transition from oviparous to ovoviviparous (and perhaps to viviparous given time) has happened a few times in several different families, and various creatures give milk - the Pacific Beetle Cockroach, for one.
If you don't fancy insects but the extra scapula thing bothers you, how about a parallel evolution of the endoskeleton? Something that doesn't have a spine, pelvis, ribs and scapulae, but instead depends on a mesh of hollow long bones pivoting on rounded cubes (think a body composed entirely of carpals and phalanges); their organs protected inside a cage of bone while their nerves are distributed rather than having a CNS to speak of. They might be able to carry quite a bit of weight, as they would have to be tied together internally with tendons and would therefore be motile Hoberman Spheres. The legs would therefore just be the same construction with a set of much-enlarged cubic pivots within the body, two greatly-lengthened internal bones and a 'club foot' consisting of a very large pivot bone with padding and keratinised skin. That could have evolved from... well, almost literally anything you like, because the vertebral column developed so long ago.
My point isn't really to seriously suggest the foregoing, but to point out we could really do with some more information.
On a more serious note, this might not be as good an idea as you think. Hexapedal creatures are cool, but six legs is actually not as efficient in large animals as four legs. Legs are heavy and require lots of nutrients to maintain, while providing only small stability and motility benefits. They're also slightly harder to coordinate.
See [this](http://jeb.biologists.org/content/jexbio/158/1/369.full.pdf) for how hexapedal creatures have to be constructed to move efficiently.
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Superconductors will be a revolutionary enabling technology for many aspects of space construction. One such use is a magnetic field to protect a craft from solar activity, in the same manner that Earth is protected.
But interstellar space is filled with hydrogen atoms and dust, which are not charged particles.
A light-weight spacecraft will want to avoid massive shielding, but at speeds >10% c, the interstellar medium becomes a big hazard.
**How can electric/magnetic shields be used in combination with other techniques to provide safe passage at speed?** The problem with simply using an ionization laser shining ahead is the huge amount of energy expended.
Being a solar sail, can the launch laser help?
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I'm no physicist, so I will offer this as a springboard (or dart board) for smarter minds than my own...
Instead of using the superconductor's magnetic field itself to deflect approaching hydrogen atoms and dust, why not use it to hurl a spray of magnetically responsive atoms out in front of the ship. Those atoms (or whatever ity-bitty particle is most appropriate for the purpose) would act as really small anti-missle missles, knocking the non-magnetic particles out of the ship's path.
Then as the ship enters the location where the collisions have just occurred, another magnetic field can collect the now spent magnetic particles, draw them out of the way of the ship and prepare them for reuse against locations even further out front.
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The magnetic shield is only going to be one component of a protective system for an interstellar (or even interplanetary) ship.
As you note, the magnetic field will repel charged particles but uncharged particles will slip through the field. A magnetic field might be useful for protecting a ship against uncharged particles if it is being used to shape and hold a cloud of plasma around the ship. A plasma generator onboard can be used to "inflate" the magnetic field (making it larger and covering a greater area, while incoming particles will interact with the plasma. Since the plasma will be moving at high speed relative to the particles, very small particles like dust will most likely be vapourized, and the energy might be sufficient to ionize the particles and allow the magnetic field to displace them.
This is something like a Mini-Magnetospheric Plasma Propulsion (M2P2) system except that instead of allowing solar wind to push the plasma bubble, it is "anchored" to the moving ship and being used to push particles out of the way.
Of course this only works for very tiny particles. The ship should still have a wake shield to absorb the impact of larger particles that slip through the magnetic field and plasma. IF the ship is moving at relativistic velocities, the problem is even molecules of hydrogen will be impacting with massive amounts of energy. The wake shield may have to be a solid or laminated mass of ice several metres thick.
If the ship is powered by a light sail, then the laser itself can be used to carve a path head of the ship. The beam simply has to be fired along the path of the ship (this can be done during the testing phase) and the energy will have the potential to push a good fraction of the dust and gas out of the way, prior to the launching of the ship itself.
So you will have a multiple set of tools for your ships protection: shining the launch laser ahead of the launch to clear a path, using a powerful magnetic field to move charged particles out of the way and hold a plasma shield in place, and a solid ice wake shield to absorb the impact of anything which gets past.
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This is for a project where the electromagnetic pulse (EMP) from early US atomic bomb tests is somehow much more magnified than the destructive blast- so much so that it destroys electrical devices *all over the globe* (for the moment how is a mystery). The questions I have about this include the following:
1) Roughly how long would it take society to rebuild its technology, assuming it even can (the post apoc tag might not apply, I included it because in earlier drafts the society that followed remained fairly low-tech)?
2) The gritty details involving the atomic tests at the time were likely classified- how do I make sure people within and without American borders connect the disaster to the testing and hold the US responsible (In all likelihood outside forces tampering with the bombs contributed to this effect but most people wouldn't know that)?
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The problem is not that EMP is not possible, but that the sort of electronic devices in use in the 1940's were much less susceptible to EMP than the type we use today.
Most electronic items in this time period use vacuum tubes, which are far more capable of resisting the voltage surge than transistors and modern microelectronics. As well, the few electronic computers in existence are also powered by racks of vacuum tubes. They are far more likely to fail due to insects shorting out the circuits or vacuum tubes overheating or losing their vacuum.
Even long distance electrical generation and transmission is not as widespread as we understand this today. The transmission lines will pick up the pulse and deliver it to the end points, burning out transformers and generators, but the electrical grid does not connect as many people either in absolute numbers or percentage wise as today, a large fraction of the population might not even notice!
The only visible manifestation of the event would be a vary large and wide ranging aurora display in the night sky, probably extending almost to the equator if this is a global event. People will wonder what happened, but for scientists with no knowledge of the Manhattan project, they will most likely decide that this is the result of a solar flare, much like the Carrington Event of 1859.
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Is this what you were thinking of? <http://www.forbes.com/sites/peterdetwiler/2014/07/31/protecting-the-u-s-against-the-electromagnetic-pulse-threat-a-continued-failure-of-leadership-could-make-911-look-trivial-someday/#7fd799af7fcd>
Also look up faraday cages. Invented in 1944 these would have stopped the EMP from destroying all tech. However, I believe that most tech would be destroyed. However after all tech was destroyed this question answers the rest. [If all our technology disappeared, how long would it take to make a smart phone?](https://worldbuilding.stackexchange.com/questions/10133/if-all-our-technology-disappeared-how-long-would-it-take-to-make-a-smart-phone)
For the second question you could...
* angry scientists: Albert Einstein and quite a few other scientists knew about the Manhattan project. They may know how the EMP happened and rat on the US.
* witnesses: Someone sees the atomic bomb explode. Sees all the electronics get destroyed. And connects the dots.
* spies: There were spies... They would go back to their home countries and probably tell about how some top security project happened same day as the EMP.
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I am making a universe and I thought that it would be unrealistic for all life forms in my entire universe to be based upon carbon.
I am aware of silicon as a possible replacement, but I'm looking for a few more to have some variety.
My question is:
**What other elements could replace carbon as the base element of life?**
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In this previous answer to [Life on a molten world](https://worldbuilding.stackexchange.com/questions/18391/life-on-a-molten-world/18397#18397), I provided several biochemical regimes dependent upon temperature.
## At 400+ C, Fluorosilicones (silicon based macromolecule)
Each of the suggested biochemical regimes includes carbon as the backbone molecule for the chemical chain, except that of the highest temperature which is Fluorosilicone chemical chains dissolved in fluorosilicone solvent (our chemistry is proteins [carbon chains] dissolved in water) for temperatures in the 400 C - 500 C range.
$$\begin{array}{|c|c|}
\hline \text{Temp Range} & \text{Macromolecule in Solvent} \\
\hline \text{400° C to 500°? C} & \text{Fluorosilicones in Fluorosilicones} \\
\hline \text{113° C to 445° C } & \text{Fluorocarbons in molten Sulfur} \\
\hline \text{0° C to 100° C} & \text{Proteins in Water} \\
\hline \text{-77.7° C to -33.4° C} & \text{Proteins in Liquid Ammonia} \\
\hline \text{-183.6° C to -161.6° C} & \text{Lipids in Liquid Methane} \\
\hline \text{-253° C to -240° C} & \text{Lipids in Liquid Hydrogen} \\
\hline
\end{array}$$
This table suggests that our familiar protein in water form of life is only appropriate for a certain range of temperatures. When you develop worlds in other temperature ranges, native life will develop for the temperature range of that planet.
e.g. Mars (average temperature of -65 C) might require proteins in liquid ammonia while Titan (average temperature -180 C) might require life using lipids in liquid methane.
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Nothing. The only element that is chemically similar and abundant enough is silicon but it suffers from a serious flaw: It's too big. It doesn't like forming long chain molecules. Look in nature, you don't find big blocks of silicon. Rather, you find Si - O - Si - O type structures. For rocks, fine--but when you try to stick the normal structures of life on there you now have hydrogen and oxygen stuck to silicon when they would prefer to be stuck to each other. The result is at best unstable, at worst a high explosive.
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Arsenic, which is chemically similar to phosphorus, while poisonous for most life forms on Earth, is incorporated into the biochemistry of some organisms. Some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines. Fungi and bacteria can produce volatile methylated arsenic compounds. Arsenate reduction and arsenite oxidation have been observed in microbes (Chrysiogenes arsenatis). Additionally, some prokaryotes can use arsenate as a terminal electron acceptor during anaerobic growth and some can utilize arsenite as an electron donor to generate energy.
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Other elements that could be the basis for biochemistry are germanium, tin, lead, silicon, boron, sulfur, and phosphorus.
Specific polymers and chemicals that form possible biochemistries are:
* Boranes (B, H)
* Silicones (Si, O)
* Polydimethylsiloxane (Si, O, CH3)
* Phenylsilicone (Si, O, C6H5)
* Polymeric Diphenyllead Oxide (Pb, O, C6H5)
* Polymeric Diphenylltin (Sn, C6H5)
* Butylpolystannoxane Polymer (Sn, O, OH, C4H5)
* Polysilazane (Si, N, H, CH3)
* Polymeric Phosphonitrilic Chloride (N, P, Cl)
* Dimethyl Polyborophane (H, B, P, CH3)
* Polymeric Silyl Orthoborate (Si, O, B, CH3)
* Dimethylated Polygermane Organopolymer (H, C, Ge, CH3)
All information in this post came from Xenology[1](http://www.xenology.info/Xeno/8.2.3.htm). The info in parentheses is the ions and elements in the polymer.
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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.
**Setting**
[The US is waging a failing War on Drugs where cartels are quickly gaining power](https://worldbuilding.stackexchange.com/questions/34154/how-would-a-drug-cartel-claim-legitimacy-as-a-government-entity).
**Scenario**
In the near future, say 2030, with current technology, the Texas state government is implementing a unified surveillance program that will extensively use a variety methods, including :
* Street cameras
* Wi-fi location trackers
* 911 call data
* [Stingray
technology](https://en.wikipedia.org/wiki/Stingray_phone_tracker)
* Automated license plate readers
* Criminal record/vehicle registration database
* Passive social media monitoring
* Web traffic interception (NSA tech)
in an attempt to give their state the advantage when it comes to gathering intelligence on the notorious cartels that are waging a territory war which has been ravaging the state. However, this program is different from others in one way : it utilizes an experimental AI developed jointly with SRI International, the DHS, MIT and the FBI. Named the ADAS (Analytic Data Assisted Surveillance), it has the power to track and identify suspicious behaviors or patterns by taking in data from all of the sources listed above.
**Technical Details**
This AI is nowhere near sentient. It is closer to the purpose built AIs that are strictly designed to function as an automated data analyst. Think of it as a less advanced version of the Superintendent from Halo ODST, connected to a surveillance grid that is a somewhat more intrusive version of modern day Camden's surveillance grid. It can detect and interpret complex patterns using pattern recognition, natural language processing, image processing and machine learning.
Examples of how it would reason :
```
import sqlite3
import ADASpack
setloc(6700 Sherman Street)
cur = con.cursor()
scn_plate(E29346)
cur.execute(SELECT * FROM VEH_REGIST;)
df = pd.read_sql_query(cur.execute(WHERE plate_num = E29346;), con)
if theft_status == 1:
return(warn_veh_theft, plate_num, scan_loc)
veh_sus.append(plate_num)
else :
return()
veh_log.append(plate_num)
scn_face(ID9283498132475)
cur.execute(SELECT * FROM FED_PER_ID;)
df = pd.read_sql_query(cur.execute(WHERE id_no = ID9283498132475;), con)
if warrant_status == 'FELONY':
return(warn_felon, id_no, scan_loc)
act_felony.append(id_no)
elif warrant_status == 'MISDMR':
return(warn_misdmr, id_no, scan_loc)
act_misdmr.append(id_no)
else:
return()
per_log.append(id_no)
```
**The Problem**
How would this affect the lives of citizens? Each person knows that they are constantly being watched, so it would obviously have a chilling effect on dissenting speech, although that has already happened to some degree in my universe.
How would the cartels adapt? Assume that the larger ones have skilled hackers that are good enough to find holes in the system, and are skilled enough to keep up with the cat and mouse game of encryption against the government's programmers. Would they focus on disrupting the system, going back to old-school hand ciphers, or both?
What would the political ramifications be? Since whoever controls this system has a lot of power to do some serious muckraking, or cover it up as well...
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There will be a sort of bell curve response as people who don't have the skills or don't care settle into their day to day lives without worrying too much about intrusive surveillance, while the criminal, hacker and libertarian element are busy working out ways to circumvent it.
Some ideas are clearly "out". People hightailing it into the desert or other places where they think they can avoid surveillance will simply be telegraphic their intentions to the AI (and Predator drones can see you from a long way away). More subtle methods will have to be invented and practiced so that people can interact outside the parameters of the AI "in plain sight". Rather than smash and grabs, think more of con games, pickpockets and 3 card monte, or elaborate stage magic shows where the magician fools you with slight of hand, leaving you to wonder how exactly that was done.
Ubiquitous surveillance states are already in existence, and have had the better part of a century to practice. The former Soviet Union had things like FAX machines and photocopiers in locked rooms with limited access and hordes of people co-opted or forced to spy on their neighbours. East Germany had an incredible ratio of agents to population (over 174,000; over 2% of the population), and more modern states like Iran and China (and modern Russia) use the internet and social media monitoring and electronic warfare methodology to extensively monitor and filter the population's information.
Despite all this, there are a multitude of things people do, both high tech (various work arounds exist to penetrate the "Great Firewall of China", or you can be as simple was using "burn" phones for a single conversation), to low tech (Samizdat in the Soviet Union was basically conducted by hand copying information and passing sheets to trusted agents or through dead letter drops).
The real key is to ensure that your activities are not far enough outside the parameters considered "normal" to attract attention. If the backstory you wrote is accurate, there must have been a time where the various anti government groups infiltrated or subverted various government agencies, so can have inside people to monitor what the AI is doing and report back what is working and what isn't, or even manipulate the feeds or outputs of the AI itself.
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People (and cartels) will probably begin to meet in place outside the sight of the AI and controls, like in countryside, a baseball game, a busy street, or a lake river and talk, while doing something completely legal and unrelated.
Or they can use a method like the Italian Mafia, which used a code written on paper, the so called "pizzini".
In general, I suppose the the majority of the people probably will not care (not more than now) while the cartels will soon learn to avoid the surveillance, by technological countermeasures or going back to less technological methods that will probably beat the surveillance infrastructure
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One possible cartel strategy might be to overload the system.
* Make a point to have not-yet-convicted kingpins use the same barbers, the same grocers, the same country clubs as respectable citizens and political leaders. Suddenly those people are flagged as *associated* with criminal circles.
* Say they know one of their operatives is under suspicion. They cut that operative loose from their real operations and send him out to hand-deliver advertising flyers to a dozen random and not-so-random people. "Good morning. Have you considered to change your phone provider? No? Sorry, have a nice day."
* In areas with suitable climate, build a drone which seeds/plants MJ in upper-class suburban gardens. "Sorry officer, no idea where that came from." "Yeah, sure."
* They take some of their not-yet-laundered money and wire it to random people. Couple of thousand dollars each, no comment.
All those people would become *persons of interest* to the AI, right? They show up on no-fly lists, based on classified intelligence, they are denied jobs in even remotely security-critical sectors, with no legal recourse. Until those citizens dismantle the surveillance operation.
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The cartel and other organizations would try to find ways around the surveillance by communicating with systems that most wouldn't consider to have the AI search. Actual criminals have communicated over [video game systems](https://www.computerworld.com/article/2470702/law-enforcement--gangs--terrorists-plot-evil-over-xbox-and-ps3.html) and the dark web using coded messages to avoid government surveillance. They would also establish more of their own infrastructure to prevent government spying like [making their own cellphone towers](https://www.dailymail.co.uk/news/article-8525407/Drug-cartel-narco-antennas-make-life-dangerous-Mexico-s-cell-tower-repairmen.html). These methods would become more sophisticated methods of what these criminals use today to avoid detection.
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In a near future, Humans are reluctant as ever to release the grasp on outdated infrastructure. They end up building a highway that consists of a giant conveyor belt, with 'entry gates' that speed up vehicles enough to enter. The idea behind this is that the belt travels at 70mph while the cars on it also travel 70mph, decreasing travel times while keeping it relatively safe to travel at such high speeds due to the baseline of the belt.
Ignoring cost and energy requirements for such a structure, what challenges would one face using this method? How would a vehicle reliably and *safely* dismount the belt other than an exit ramp that slows you in stages?
EDIT: I was thinking perhaps something similar to the idea about [the train that never stops](http://www.zdnet.com/article/high-speed-rail-20-trains-that-never-stop/); a secondary platform that you merge on to which then slows down and deposits you back on to the normal streets -- but how would this work with high traffic density?
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There is still a danger. When a vehicle veers off the road into a pole they will hit at 70 mph + 70 mph = ***140 mph***.
Also merging in will be a problem. Relative to the static structures the cars on the belt will be going the 140 while those merging in will come on the belt at 70 (accelerated under their own power). A collision between those two will be a 70 mph collision. They will need to be separated until the speed difference is low.
Then consider traffic jams. The belt will force the cars ahead which is a problem when there just isn't space where they want to go. That's a pileup waiting to happen.
Actually getting on and off will probably be by first accelerating to 70 mph on a static road then coasting onto a new lane with the belt at 70mph and then accelerating again to 70 mph before merging into the main stream.
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Well to begin, you are still traveling at 140mph. the car is only traveling at 70mph in relation to the belt. so the trees going by on the side of the road are still going by very fast. What happens when there is an accident on the belt? do cars get sent off and pinwheel 20 times through the ditch and surrounding countryside? or do they all somehow get 'kept' inside the belt and bounce around like pinballs into each other?
You are also right, speeding up and slowing down to match speeds outside of the 'highway' would be problematic, especially since you are not going to get all 4 wheels to merge onto a different speed belt at the same time.
I think you'd be better off having a magnetic system, where the 'highway' is static but the 'force' it provides moves, like magnetic pulses.
Asimov had a similar system in the Robot series, but it was for pedestrians, and there were many belts of different speeds depending on how far you were traveling, and the got progressively faster toward the center, but in small enough increments you could do so at a walk. So you might be able to do it with vehicles if they are of the 2 wheeled variety, and you have several belts of increasing speed.
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Since changing speeds is so problematic, the belts should be subdivided into much finer gradients, so each time you step or drive onto a belt, your speed only changes by 10mph, for example. For a beltway designed to carry cars, this would lead to am improbably wide "highway" (and the machinery for the belt would make the right of way even wider)
Perhaps it would be more realistic to have a beltway sized for people. Each belt could be less than a metre wide per speed gradation, and so long as certain rules are enforced to keep people from being unbalanced and falling across the various beltways (for example, you could not carry a suitcase in one hand, you could become unbalanced or strike a person in a belt beside you. All luggage would have to be in roll along suitcases, or in "shopping carts"), then travel would be fairly safe and secure. Each direction would be enclosed to prevent people from being affected by wind or rain, and at the same time an enclosed conveyor belt like this might also diminish headwinds and buffeting inside the tube with some clever design (the air needs to be moving at almost the same speed as the people, so there will be a very interesting ventilation system inside).
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## Self-Guided Cars
Well, if this is in the near future, you could always say the cars are self-guided. Then there isn't as much risk of them going off the road or crashing into each other.
You could also say the cars are linked to some central traffic computer that controls the belt speed and the individual cars. That way, if there's going to be a traffic jam or other problem, the central traffic computer can slow all the belts and reroute cars to avoid accidents and such.
If humans want to drive, you can just have them drive on normal, non-belted roads. If they want to use the belts, they have to engage their car's auto-pilot.
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I want to raise some maintenance issues with this design.
First of all how would the belts be replaced as the wear out, if the belt is just one long continuous stretch, a couple of miles would be out of commission. Secondly. how would the belt be lubed, often times large belts like this need to be lubed, see space shuttle crawler. Also, how often would the belts need to be replaced? After all they are being worn from both sides (the wheels of the car and the conveyor wheels). Another thing what happens to the drivers if the belt snaps, how bad would the injuries be. So the maintenance issues alone would be a huge challenge for the average driver.
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A radiothermal generator uses the heat produced by radioactive decay of the radioisotopes contained to generate electricity. The main difference with nuclear reactors is that there is no "reaction", chain reaction or otherwise, just the natural decay of the isotopes.
Currently RTGs are used as power plants in situations where a power plant that works for several years without maintenance is needed. This is because an RTG doesn't actually **need** any moving parts to work. Such RTGs use thermoelectric systems and highly radioactive isotopes selected based on the desired lifespan.
But there is nothing stopping you from using less radioactive isotopes for longer lifespan or using more normal solutions for turning the heat into electricity. Using such RTGs instead of nuclear reactors would have some benefits.
Can use any radioactive material. Uranium, thorium, radon, nuclear waste... Since the RTG does not need to support a chain reaction it does not care what elements or isotopes you throw in. This should make fuel much cheaper to get.
Much simpler fuel refining. Since the RTG does not care about the specific isotopes and can't be "poisoned" by inactive material, chemical refining methods are sufficient. No centrifuges or other methods capable of creating weapons grade uranium are needed. Refining fuel creates no risk of enabling nuclear weapons development. Much lower level of technology and investment is needed.
Less waste. Much less waste. RTG works until the fuel is no longer radioactive. Normal reactors only use a portion of the fuel since using the rest would requiring refining the used rods to make new fuel, which would enable refining the fuel for weapons grade material. So much of the fuel is simply wasted.
Safer waste. The high neutron flux of a reactor creates new radioactive elements such as plutonium. The RTG generates less flux and generates less such material. And any such material would be much harder to separate even if somebody opened the generator while it is operating. So unlike a reactor the RTG does not help in generating material for nuclear weapons.
Safer. No reaction means the reaction can't get out of control no matter how many safety systems you disable. You still need a containment vessel and it still can rupture and release steam containing radioactive material, but since the RTG does not need or generate highly radioactive isotopes and a runaway reaction can't melt the fuel the level of radiation would be much lower than with a reactor. Which would help a lot with fixing the damage.
So if it is so safe and solves all nuclear proliferation issues, why aren't any being used? Economics. Such RTGs would be **much** larger than a reactor generating the same wattage. The RTG could operate almost indefinitely with little maintenance without ever needing refueling. But reactor fuel and maintenance are not expensive enough to make up the higher initial cost with any realistic interest rate. Although the fact that RTG would be much simpler and cheaper per volume would help.
So with that intro, here is the actual question. **Under what circumstances, if any, could using such large RTG systems for base power become economical?** Science based, but not real world. Alternate reality or history is okay if it makes sense and obeys the same science.
First question, btw. And something I have been thinking for a while.
**Important note.**
From the first answers it seems that I did not properly explain how different these base power RTGs would be, would **have to** be, from the RTGs currently in use. I'll note some specific issues that were relevant to those answers. (And really necessary to understand the question and why I am unable to even suggest plausible economics.)
Current RTGs have relatively short lifespans and use "artificial" isotopes with relatively low half-lifes. The RTGs I am suggesting use natural radioisotopes of uranium or thorium. These materials have half-lifes of more than a billion years! (That is why they are still common.) Obviously the power density sucks big time. On the positive side it will take millions of years before the power runs out. On the negative side the installation would need to be huge beyond belief to generate useful amounts of power.
So these are not small (relatively) devices spread around that can be lost or abandoned. these are a small number of installations you can see clearly marked on the world map. Or with your own eyes from the Moon. This is because the only way to even approach usability would be to take advantage of cube-square law of the radiothermal energy going up with the volume (mass really) but of the mass (and thus cost) of the containment with the surface area. Power generating systems would scale with the power generated (the overhead becomes insignificant at this scale), so they would be fine.
I might be overestimating the scaling issue, though. Even without chain reactions neutrons released by fission would occasionally hit other nuclei. So the rate of fission would almost certainly be higher than the normal half-lifes would suggest.
So these RTGs would not be so much devices or even installations as they would be artificial geology in (more or less) state of equilibrium. With a small building (or several) on top to house the actual generators.
So both the RTGs and the fuel contained, essentially large chunks of solid metal, would be stable and secure for probably few centuries, possibly millennia. You can ignore toxicity.
The issue is the economics of something that large and with that long lifespan. I have no clue how it could be possible. Maybe a society that takes a very long view. Maybe it really works better than I thought it would.
I apologize for not explaining properly. I have no idea how I thought people would get the scale issue when I forget to mention it.
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RTGs produce little power for many years, as such they are ideal for situations where the power requirement is small and where maintenance is difficult or impossible, i.e. radio beacons in far North, satellites and so on.
They are opposite of ideal for the conventional power though. A coal power plant can have output of 2~3000 MW, and RTG, maybe 2~300 W, that's about ten million times less, and it takes a lot of coal plants to keep country going.
Considering that there have already been incidents of people being poisoned by abandoned RTGs, it isn't hard to see that having an equivalent of tens of millions of there things is neither efficient nor safe.
One of the main issues with RTGs is that they are horribly inefficient, so making larger scale ones would likely lead to engineering complexity growing faster then usefulness. Much larger device also means much larger chance of leaks or other structural problems, which at a certain size will start to negate the lack of maintenance advantage, as it will require constant monitoring and fixes in a potentially dangerous environment.
In most real life situations it would be better to use solar or wind power, as it also requires relatively little maintenance with the main drawback being space, which is also true of RTGs. So they have the same drawback and similar advantage, but solar and wind are less dangerous and can produce more power.
So to answer the question: if the planet had no wind and not enough solar energy reaching the surface, and the people would only use electricity for only absolute essentials, while also not having enough time or expertise to run a regular nuclear plant (like say a remote space colony or a prison planet) I think it might be plausible to use a large RTG.
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We already do this. It's called Geothermal Energy:
<http://phys.org/news/2006-03-probing-earth-core.html>
and:
<http://en.wikipedia.org/wiki/Geothermal_energy>
Now if you wanted to (for some reason...) set up a world where you artificially exaggerate this effect, by say, filtering the various radiative isotopes out of the inner earth and moving them closer to the surface, I suppose you could - though I expect that there would be serious negative consequences.
<http://en.wikipedia.org/wiki/Man_of_Steel_%28film%29#Plot>
If you were colonizing a planet at the edge of the habitable zone, and judged it just a little too cold for comfort, it might make sense to bring lots of extra radio-isotopes and bury them to raise the overall temperature...
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Even if you could generate a nominal amount of power, the inputs required just for building and maintaining such a massive facility would be truly awesome, so you are better off doing anything else (whatever fuel sources you use to construct this facility, just use that for your power generation and still save most of it).
As a rough idea, radioactive materials produce energy in inverse proportion to their half-life (longer the half-life, the less energy you get out of them). If you want a material that will keep the radioactivity for very long periods of time, the amount of energy coming out of it is negligible. If you want it to run 'almost indefinitely' without refueling, it would be producing so little energy that it would be just a large art project. We use fuel with short half-lives not because we just don't care about a long-term, but because generating meaningful amounts of power requires something highly energetic as a power source.
Just scaling up is not a solution to using low energy fuel as the engineering complexity and construction costs rapidly increase when you build on a huge scale (actually makes the project more difficult). The challenge of thermally isolating that giant mass from the rest of the planet, because the heat conduction needs to go through the thermocouples or working fluid if you want to extract power from it (otherwise you are just using geothermal and mixing in radioactive ores you've mined elsewhere at great expense for no discernible benefit), would be an engineering marvel by itself. Building bigger gets more complicated, not less, as you have much greater forces to contend with while material strength stays the same, and eventually you start getting geologic forces to contend with (subsidence issues from the mass over long timescales could cause serious issues).
RTGs slowly reduce their power output over time as the fuel loses energy and the components degrade (they are not maintenance free but just have components expected to live as long as the relatively short-lived fuel). Even if the fuel lasts for a couple centuries, the components used for electrical generation certainly won't.
By holding this fuel until it is no longer radioactive, you also ensure that the facility spends much of its time sitting idle as the fuel degrades below a practical operating threshold yet still radioactive through the long tail. The waste is still there, and still needs to be dealt with eventually. If your big concerns are producing waste and not generating any material which could be used for nuclear weapons, there are plenty of designs for fission plants which meet those criteria for a considerably lower cost and with massively higher output.
Bottom-line: these would be giant art installations, requiring massive resources to construct, for comparatively little energy generation.
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My guesstimate is "not a feasible scenario." The reasons:
* RTGs provide relatively little power for their size. Taking just any random nuclear waste will only make less efficient.
* Most radioactives are not just radioactives but poisons on a chemical level. RTGs would require strict supervision. A rusty forgotten RTG on a scrapyard could poison the entire city if it leaks slowly, no fireworks required.
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The issue is cost. A pile has some amount of radioactive material in it. This is used to generate energy. At some point there is a term measured in kW/kg regarding how much power a kilogram of material can output. Note this is power, not energy. You mentioned they have to be big, but you did not mention that they have to be expensive. Uranium has a market price, and there will be a cost for packing it into the reactor. Now we can start talking about kW/dollar. Unfortunately, if you have to wait a billion years for a large portion of the uranium to decay, your ROI is not very desirable.
Perhaps you could do this once you start talking about being a Class I civilization, where massive earthmoving projects like this are reasonable.
Or, taking the other approach, you can look at codeMonkey's answer (which I +1'd), which is an example of how to do this at minimal cost... and by that, I mean not gathering anything at all and simply using the existing pile in the Earth to do the work for you.
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If you use artificial isotopes you run into cost issues, while at the same time, RTGs generally have lower power output than mechanical nuclear power sources and less durability. We have power stations in USA that are already 50 years old and running, while RTGs cannot beat this due to degradation of the photovoltaic panels due to the bombardment they suffer from ionizing radiation. A RTG is simply a radiological source contained inside a photovoltaic sphere. The gamma rays that the source emits are turned into electricity by the photovoltaic cells, but at the same time, those cells suffer a much higher degradation than when used under sunlight. Gamma rays have much more energy per photon than solar light, this means more power per square meter of photovoltaic area, but means that the semiconductors are destroyed much more quickly. This, coupled with the higher cost of the power sources (artificial power sources that are good at generating gamma rays). Those characteristics together prevents widespread use. RTGs are used where maintenance is hard to impossible (like Siberian light houses) or satellites. Anything that provides easier accessibility will be using Diesel generators or have a energy line connected to mainstream energy generation technologies. Thats why, for example, we dont use RTGs to generate large scale power.
Even if you have accessibility problems in a certain area, if your power requirements are too big, you will probably use automatic nuclear power plants of the thermal cycle type (usually rankine, but you might do brayton cycle nuclear power plants if your power needs are bigger than the usual for RTG and smaller than the usual for Rankine cycle based ones), not of the photovoltaic type. On the moon, if you trully need power sources that powerful, you will probably use robotic nuclear power stations, as the risk of explosion is not significant. There is no population on the moon, or wind to spread the escaping nuclear material. RTG use is limited by the technology itself.
TL;DR
Major factor against RTG is power density, cost and shorter lifespans than properly managed nuclear thermal power plants.
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What would happen to an Earth-like planet if its core completely and instantly vanished? Would the planet begin to pull in on itself due to asymmetry and the empty space in the middle, or would it begin to fail due to another factor? Or would it remain (relatively) unscathed? If so, for how long?
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# Collapse.
Gravity takes care of this. As soon as you remove the core from the Earth, you have a large void in the middle of it, and a lot of gravity acting straight towards the centre of that void. The void may also be a vacuum - depending on whether you replace the core with air or not - which will accelerate the collapse.
It is worth noting that this is only possible because the mantle is liquid. If it were solid, the spherical shape would hold it together and the Earth would retain its shape.
As Spacemonkey has said, the resulting loss of mass of the Earth *would* disturb the Moon's orbit. I'll go into some basic orbital mechanics to show why and how.
The Moon has a stable orbit around Earth because as its velocity carries it forward, the gravity of the Earth pulls it sideways, resulting in a perpetual circle:
If the mass of the Earth decreases suddenly, so does the sideways force on the Moon, so it moves more straight - away from Earth. As it does this, the force decreases further, so it moves even further away, and so on:
This is... bad. Not only has everyone *already* died because everything collapsed underneath them, but [scientists predict bad things](http://sciencenordic.com/what-would-we-do-without-moon) if we lose the moon.
---
In short: everyone dies.
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## The planet would implode.
You've instantly removed the core. So what's in its place? **Hard vacuum**. There is a [relevant xkcd](https://what-if.xkcd.com/6/) for a similar scenario.
Outside of the core-vacuum is a molten magma. The pressure exerted from the Earth on the other side of that magma is still present and the magma will be blown, violently, into the suddenly empty space. This rapid movement will ripple up to the surface of the Earth along the most fluid paths. This will take about five minutes. Basically, it would be like every volcano erupting, at once, *in reverse*. The entire surface of the Earth would likely experience double digit [Richter scale](https://en.wikipedia.org/wiki/Richter_magnitude_scale) values. The magma rushing into the vacuum would slam into magma coming the other direction at very high velocity and, five minutes later, the shockwave would make all the volcanoes and new fissures on Earth erupt at once, in the normal direction.
This would most certainly be an extinction level event. All life bigger than bacteria would die immediately, probably in the first ten minutes during the collapse. The rest of the life would die during the world wide eruptions and when the atmosphere escapes the Earth's corpse.
The moon would [probably stick around](https://worldbuilding.stackexchange.com/a/6524/3202) for a little while.
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I am writing a novel, in which the main character has their mind transferred to a wolf body, losing all their memories in the process.
My current explanation is that the state of every neuron in the human's brain was measured, and after some translation, the wolf's neurons were modified (perhaps by focused EMP's), so that it basically matched the human brain. Differences in human/wolf neurology and imperfect brain-to-brain translation account for the amnesia.
Are there any flaws in this method (other than the fact the technology doesn't exist yet) ? And how else could this be done? What side effects could be expected?
Answers *not* involving whole brain transplants or magic would be preferable.
apart from the mind swapping, I want my novel to be as realistic as possible
You can read the beginning of the novel over at <https://www.fictionpress.com/s/3200987/1/In-The-End>
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Number of neurons and skull volume would thwart your scheme. Wolf brain is much, much smaller. Human brain won't fit, even if surgically inserted there, never mind rewiring the wolf brain.
Your option is removing the two brains and enclosing them in life-support jars at the lab. Implanting a transceiver connected to neural endings in the wolf skull, and a similar transceiver attached to the stub of the spinal cord and remaining neural endings of the human brain in the lab. Map the nerve endings right, and have the brain sitting in the laboratory perceive whatever the wolf body perceives and control it as if it was its own body - remotely, over the radio.
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The thing to actually do is maybe that the wolf and the human had a physical morphosis too, so that the human brain and the wolf brain would fit in each of the corresponding skulls, and that the amnesia could count as a failed transition.
The Brain of the wolf is smaller and the human brain is bigger, so either you transform their bodies a bit, and they have a failed experiment or something else.
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**Simulation**
An organic brain would be almost impossible to manipulate in this way... it would require a complete rebuilding of almost every single neuron (which we aren't even close to knowing how to do), and there would be no continuity of "person" (no identity, no memories, etc.).
However, if you take a scan of both brains, and then simulate those brains in a computer... you could put those minds into a virtual environment in any kind of body you want.
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This answer will be a bit interesting....many people believe in their being a spirit, something inside that sustains life. How many of us have come to believe the body is just a shell, with the spirit being the true self? If this is true, then all that needs to be done is create technology capable of drawing out a spirit and putting it into another body.
This should work, but it'll be interesting; when the spirit and the body come together, it creates the soul (as far as I believe), and two influence each other back and forth. Our minds and hearts are often influenced by our body's built-in drives and instincts. A human spirit and intelligence with a wolf's pack predator mentality and aggression will be an interesting combo, especially vice versa.
A wolf's intelligence is more primal (driven by instinct), and less developed. Inside a human body, the wolf will be able to reason and think as well as a human, but the wolf will lack more self-control than most people do, instinctively following his or her instincts. That being said, this wolf will likely be more of a team player than regular people. (That and this person will have a thinh for raw, even *live* meat....)
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**The Setting:**
A [Gas Torus](http://en.wikipedia.org/wiki/Gas_torus) around a star. It has enough atmosphere and elements for earth-like life, and is roughly analogous (plants, animals, etc). Small asteroids are present throughout torus, but nothing large enough to collect significant gravity. Life does grow on and use these asteroids for material. Water is present throughout, but is rare enough that generally the entire setting acts as an arid desert because there's no natural gravity-based water cycle. There's no night or day, but uneven heating plus orbital rotation does mean that the torus experiences things we'd call weather - wind and storms.
It's absolutely huge in scale, being a ring in the habitable zone around the entire star. Think thousands of earths in volume, with enough atmosphere to allow radiation protection and still have a fairly large habital area.
**The People:**
A sapient species has developed in this torus, and are native to a zero gravity situation. They can fly, have manipulating structures similar to our fingers and have roughly the same visual spectrum that we do. They're significantly larger than us, but not by too much because they do have to worry about moving their mass around even if they don't weigh anything. Something on the rough order as the same mass of a horse. Like us, they developed as [cursorial hunters](http://en.wikipedia.org/wiki/Cursorial_hunting), and have recognizable social structures (if you think it matters, use western first world cultures as the baseline).
**The Tech:**
Pre-computer age - early 1900s America. They have domesticated animals for work, transport and food. If you want to put in some variation on tech, that's fine. Metals will be rarer than on Earth because they're more difficult to mine and smelt in free fall. Petroleum is available but very rare. Power is primarily generated through wind turbines and solar (no night, and they get some crazy wind).
**The Problem:**
What kind of cities would this species build? Specifically:
1. Would they have sky roads and buildings, or some other kind of organized structure?
2. How would they handle city logistics - water, power, trash, sewers?
3. How would they keep the city together and keep it from drifting apart?
4. Human architectural styles differ considerably based on culture, but are there any specific architectures that this species might develop as a result of their freefall environment?
**The Notes:**
As described I suspect this setting will require significant [handwavium](http://en.wikipedia.org/wiki/Unobtainium) to keep from following apart. Answers should still be as science-based as possible, no outright magic.
*Please ignore the feasibility of the setting in your answers.*
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In order to answer all the problems you pose, you must first understand the nature of your environment.
Everything in your proposed environment is *in orbit* around the primary. This means many of the fundamental notion of motion, forces, and propulsion to which we've become accustomed on Earth will not work the same way.
***The Motion***
Some principals of motion for things in orbit.
* If you release something (and it applies no other propulsion), you
and it will intersect in exactly 1 orbit.
* Once two object's orbits intersect, they'll continue intersecting in
every orbit until something exchanges momentum with one or the other
of them.
So getting rid of garbage would seem as easy as extending a cable with the garbage on the end until tidal forces are sufficient to pull them away from the habitat. Unfortunately, you and that garbage will return to the same orbit at the same time every full orbit. Ultimately, you'll need to provide that garbage with some ability to change its orbit.
Thought experiment: try to get rid of garbage using tidal forces and a parachute
1. Create a long cable
2. Put the garbage bundle on the end of the cable
3. Drop the bundle either inward or outward (for our purposes the
results are the same)
4. Play the cable out to its end
5. Tidal forces are pulling the bundle away from you (the amount is
proportional to the $ \frac {M\_primary}{r^3} $ )
6. With this configuration, the bundle keeps returning to the same spot
at the same time you do
7. If you included a parachute, the winds inward of your habitat will
be faster due to its smaller orbit.
8. This will tend to add kinetic energy to the bundle.
9. This will tend to push the bundle into a wider orbit.
10. Which pushes it back into your habitat.
In this case, parachutes are bad for garbage but good for a man overboard situation.
What you need instead is a small propulsion unit to alter the trajectory of the garbage package (ideally $ \frac {1}{2} $ orbit from the habitat but doing so shortly after release would be fine. Since the region is so big, the garbage need not have a powerful propulsive unit.
A good mnemonic to remember how the changing momentum changes your position relative to other nearby objects:
* Thrusting outwards moves you anti-spinward.
* Thrusting inwards moves you spinward.
* Thrusting spinward moves you outward.
* Thrusting anti-spinward moves you inward.
***The Forces***
To elaborate on the previous answer,
**Spinward & antispinward**
components will be subject to mild compressive and tensile forces. Pipe and wire connectors should be sufficient to hold members in place and provide for "pedestrian" & elevator traffic.
**Inward & outward**
These forces will be bigger than the other forces. The equation that governs this force is the tidal force calculation.
$$ F = m\Delta rG\frac{M}{R^3} $$
F - Force on the body away from it's center of mass
m - Mass of the smaller body
$ \Delta r $ - Distance between center of mass of the small body to its edge
G - Gravitational constant
M - Mass of the larger body (e.g. star)
R - Distance between center of mass of the two bodies
Components will be subject to mild tensile forces. Wire only connectors should be sufficient to hold members in place and provide for "pedestrian" & elevator traffic.
**Northward & southward**
Components will be subject to mild compressive forces. Pipe and wire connectors will be necessary (pipes for the compressive forces, wires for stability).
and of course you should read the book [Integral Trees](http://en.wikipedia.org/wiki/The_Integral_Trees) for more information about life in a "smoke ring".
***Answering the Question***
* All "cities" need to have each component physically connected or the
pieces will drift away.
* Because the forces are small very small compressive members and thin
cables, wires, tethers, ropes should be sufficient to keep outer
pieces of the city in place.
* Connectors for components of the inner city may need to be
substantially beefier in order to take their own forces as well as
those of any components latched onto them.
* Air breathing propulsion is possible (jet engines, propellers, and
wings). "Sky roads" in the city will be by way of the connectors -
they could be as simple as hand holds for "pedestrians" or cable
elevators or something else entirely.
* "Sky roads" beyond the city will require some sort of engine (you
could go steam punk and make them all steam powered rockets or some
such).
* I would think it'd be crazy to try to make a jump without knowing
your destination, so the amount of $ \Delta V $ required should be <
25 m/s.
* The city could harvest water by simply firing a harpoon with a tether
into it. I imagine surface tension forces ought to wick the water along the
tether
* The city's food would have to be cultivated in "farms" attached to
the city. This would require much more work to "capture" and anchor
to the city.
I would imagine the architecture would be open, 3 dimensional, and spacious. The place would have room to spare and then some. City expansion would depend much more upon the ability to capture and harvest resources floating around.
Think about this as you would a space station, you have to go and find everything that you need, maneuver it close enough to your city to utilize those resources, and then anchor it there. The original kernel of the city likely formed around especially valuable treasure trove of resources (dirt/mud ball, water ball, or tangle of native life and its "dirt"). This could still be around or totally used up by now.
It might experience "feast & famine" / "boom & bust" episodes as newly anchored resources leads to abundance. Then the famine sets in when they are used up and while you're waiting to capture the next resource. There might be periods where the city encounters lots of water but no soil or metals (or vice versa).
Steampunk like "airships" (only these don't require balloons to make them float) might ply the space scouting for more resources.
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I foresee hollow protoplanets!
Since this species develops in a free-fall environment within a space-based cloud of gas littered with resource-rich/-poor asteroids, the first major structures will be built on the asteroids for mining operations. Individuals rarely want to travel long distances to get to work (long is, of course, relative in space), so housing will be built on the same asteroid as the mining facility. As the facility grows, it will need access to more resources, so either the company will start another mining facility or haul other asteroids to an existing one.
Clumps of asteroids then become the foundation for larger settlements, which attract more attention, more business, and more inhabitants, which bring in more asteroids to support the growing population.
Independent facilities will produce a similar effect, though in this case "clumps" will be individual asteroids connected via trade routes. The collections will attract attention, which brings in business, inhabitants, and more facilities. To prevent unwanted drifting, asteroids would be tethered together to emphasize established trade and transport routes.
In either situation, the city is developing in three dimensions, expanding roughly evenly in all directions. This produces a spherical structure, with the oldest buildings at the center.
Tethers and nuts and bolts should be quite capable of holding things together; after all, they do quite well under constant gravitational stress from Earth.
The common architecture is going to be something much like what's on the ISS. There's no real *down* direction, so doors can be in any flat surface, possibly even in cones, corners, or hemispheres. In the case of asteroid clusters, paths of travel will be delineated by the structures themselves, where walls and solid connectors work together to create tunnels through the whole structure. In the case of asteroid collections, paths of travel will, in the macroscale, be defined by the inter-asteroid tethers, while local conditions will be like those for asteroid clusters.
The tethers and pipes used to connect structures and asteroids can double as infrastructure. Tethers can provide electricity and fiber optic cable. Pipes supply fresh water and remove waste.
(All of this ignores the viability question of your scenario, which I am in no way capable of answering.)
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The setting is actually more predisposed for the creatures to develop a nomadic hunter/gatherer existence rather than an urbanized one.
Since things tend to stay where they are in a free fall environment, one of the issues confronting any sort of life form is getting away from wastes. Unless a large impulse is given to the waste, it will remain in the same orbit that you are in. This is true for everything from exhaled C02 (assuming an oxygen metabolism like terrestrial creatures) to urine and feces to crumbs and dead bodies; hardly what you want to have hanging around next to you.
The ecosystem will then have to consist of various life forms devoted to scavenging wastes, plants that feed off clumps of "processed" matter (possibly resembling venus fly traps or other predatory plants on Earth), and highly mobile herbivores followed by equally mobile carnivores. This will resemble the ecosystem of an ocean more than anything else.
Your intelligent creatures may resemble schools of squid, which can organize to hunt schools of "fish", and eventually develop intelligence and a form of nomadic civilization.
Structures, if needed at all, will resemble nets of various size to keep important items secure in free fall and accessible to the creatures when needed. Since they will probably have evolved some sort of organized "school" structure (placing the young adult males on the outside to guard the more vulnerable females and young, for example), more permanent structures may be developed to mimic this (birthing rooms in the centre, and rooms radiating outwards organized by age, sex and status). To prevent the accumulation of waste, it will resemble a series of "bird cages" rather than a building the way we recognize it.
Slightly different ecosystems will develop around asteroids, and creatures evolved around there will resemble the creatures living in a reef, predisposed to hide in caves, nooks and crannies either for protection or to hunt their prey ambush style. If intelligence evolves here, then expect a predisposition to cave dwelling.
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**Concept**
Or for another perspective is based upon [The Millennial Project: Colonizing the Galaxy in Eight Easy Steps](http://en.wikipedia.org/wiki/The_Millennial_Project:_Colonizing_the_Galaxy_in_Eight_Easy_Steps#The_steps_of_the_project) - specifically the section on a space colony (I believe it is **Step 4**).
Consider the much of the terrestrial radiation shielding comes from its thick atmosphere. If you wished to have an extraterrestrial habitat with the same level of radiation shielding, then it would need about the same amount of radiation shielding.
You can create such radiation protection out of gases if you don't mind it being hundreds of miles thick. However, you could build it just 32 feet thick if you use water instead.
So imagine a giant hollow water drop. The water serves many essential purposes with radiation shielding being one of them. Interestingly, the water is transparent so it will transmit light for any gardens you wish to grow inside your water drop.
Your hollow water drop will require membranes (hopefully self-sealing) on both the outer and inner surfaces to keep the water where you want it.
**Scaling**
When I ran through the calculations to find a body whose self-gravitation would completely compensate for an interior membrane pressure of 1 atmosphere, I got something ridiculous like r = 32,000 km. This would be about the size and mass of Uranus. Clearly most of the space of such a large body would be unusable (either that or I made an error in my calculations).
So it'd be better if you instead scaled the thing so that the center was still habitable. Unfortunately, the integration requires me to do too much work so let's hope someone else will do it for us.
My *guess* is that it could be as large as 200 - 400 km in diameter.
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So, within my setting, I would like to also have a kingdom based in a special desert. Absolutely all of the sand in the desert would be ore sand. Ores of any and all kinds that you could traditionally find by digging underground, you can find it here in this desert as sand.
What I ultimately intend is for this kingdom to become very rich, as they are very easily able to simply dig for sand, sift through it and smelt it for metal.
Notes:
* Tech levels for this kingdom is pre-industrial, which is quite a lot more advanced than the rest of the world which is simply late-medieval
* There is magic
* Feel free to suggest fantasy plants and animals that can live in such a desert of ore to make it more like a real desert
For this first question, the clarified question will be as such. How would such a desert of ore be different from a desert of sand?
The next question I will then want to ask, but which would make this one question too broad will be over here, which is, [what would people living in such a desert of ore need to be able to survive.](https://worldbuilding.stackexchange.com/questions/10766/the-desert-of-ore-what-would-the-flora-and-fauna-of-it-be-like)
EDIT: [The flora and fauna portion of this question has been split and moved to this other question over here.](https://worldbuilding.stackexchange.com/questions/10766/the-desert-of-ore-what-would-the-flora-and-fauna-of-it-be-like)
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The short answer is that a desert of quartz sand isn't too much different from a desert of [insert name of economically significant ore here] sand for the most part. The common factor is that the surface is a finely divided, dry, non-cohesive substance, and there is very infrequent and light rainfall for the most part, leading to a depauperate ecology where plants and animals populations are limited by access to water more than anything else.
I presume that all the sand in this kingdom will be one economically significant ore or another, but not all the same type, with each ore occurring in a patch (with some overlap of course, unless magic prevents that - such magic would be almost essential to prevent extensive mixing over relatively short periods of time). You may well also find quartz sand - it has uses in glassmaking. However, you may also find heavy metal ore sands that are quite toxic, and if any plants can even grow in such sand, they will probably become quite toxic too. Heavy metal ore sand would be toxic if inhaled too, so dust filter respirators might be a necessity.
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If the ores in the desert are fairly equally distributed and mixed together, ore separation will be a serious issue. I would assume some sort of sluice system where heavier ores can be separated from lighter ores, but I don't think this would be the only part of the separation system. There would be many instances of a slightly larger but lighter element ending up mixed in with smaller pieces of a heavier element. Metal toxicity would be a serious issue and even relatively benign metals (copper, aluminum, etc.) can poison given a decent enough exposure. Dust storms could be seriously dangerous for anyone caught in one, as well.
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According to two RPG (role-playing game) systems, **Dungeons & Dragons and [Pathfinder](http://paizo.com/pathfinderRPG/prd/mastery/settlements.html)**, a metropolis is the largest category for a **medieval city**. The population of a **metropolis** starts at **25,000 people**. I remember that they also say a Metropolis is a city for a large kingdom and that you should not have many cities that large.
But this rule seems inconsistent with our past [history](http://en.wikipedia.org/wiki/Historical_urban_community_sizes). Many cities had more than 25,000 people. Some like Rome, Baghdad, Xi'An, Edo (Tokyo) and possibly others had over 1 million people at their peak. Many other cities were well over 25,000 people.
**Can anyone tell me what is a big pre-industrial city and how common these cities are ?**
[Answer]
[Here](http://www222.pair.com/sjohn/blueroom/demog.htm) is a site where they go over some of this quickly.
the relevant parts you are specifically asking for are
>
>
> >
> > Town and City Population: How Many In Those Walls?
> >
> >
> >
>
>
> For purposes of this article, settlements will be divided into
> Villages, Towns, Cities and Big Cities (known as "supercities" in the
> parlance of urban historians).
>
>
> Villages range from 20 to 1,000 people, with typical villages ranging
> from 50-300. Most kingdoms will have thousands of them. Villages are
> agrarian communities within the safe folds of civilization. They
> provide the basic source of food and land-stability in a feudal
> system. Usually, a village that supports orchards (instead of
> grainfields) is called a "hamlet." Occasionally, game writers use the
> term to apply to a very small village, regardless of what food it
> produces. Towns range in population from 1,000-8,000 people, with
> typical values somewhere around 2,500. Culturally, these are the
> equivalent to the smaller American cities that line the interstates.
> Cities and towns tend to have walls only if they are frequently
> threatened. Cities tend to be from 8,000-12,000 people, with an
> average in the middle of that range. A typical large kingdom will have
> only a few cities in this population range. Centers of scholarly
> pursuits (the Universities) tend to be in cities of this size, with
> only the rare exception thriving in a Big City. Big Cities range from
> 12,000-100,000 people, with some exceptional cities exceeding this
> scale. Some historical examples include London (25,000-40,000), Paris
> (50,000-80,000), Genoa (75,000-100,000), and Venice (100,000+). Moscow
> in the 15th century had a population in excess of 200,000!
>
>
>
[Answer]
Let's start with highest possible number - using the ancient Roman Empire. During the times of Roman empire, Rome peaked at 1-1.2 million at around 1st-3rd century.
Following that we had Constantinopole at 500 000 in 6th century, and Changan and Baghdad around 1 million pop in 8th, 9th and 10th century. 1 million remained cap until the 19th century.
Thus, I think we can conclude: 500 000 to 1 200 000 - maximum, imperial capital with extreme cultural significance to the empire (that is, empire needs to be capital-city centric). The empire needs to be large.
100 000 - 500 000
A capital city of a very prosperous kingdom. It is important to realize that number of people in a city can change depending. As an example, somewhat small Kingdom of Bohemia's capital city, during its golden era in 14th century reached 80 000-100 000. Larger kingdoms or smaller empire who are currently in their prosperous period will have around this amount of citizens, and so will large empires who're currently falling apart. Cities within 100 000 -300 000 range might also be secondary cities of an extremely prosperous empire, cities which hold sway over large region within such Empire.
Things like war, plague, etc. can massively decrease population of cities. In case of plague, cities tend to suffer a lot, and not only do you need to count victims, but also people fleeing the cities due to fear. When economy/food production is weak because of war, cities are also unable to feed their current population and people again leave.
50 000 - 100 000 population
This size would be a capital city of a kingdom that is currently in less prosperous phase. We're either talking about a small kingdom in quite prosperous phase, to a big kingdom in their bad times. For non-capital city, this could be a secondary city of a prospering kingdom, or a somewhat regular city of a very prosperous powerful empire.
20 000 - 50 000 population
These would be capitals of not too large kingdoms that are not too properous. If your kingdom is not the dominant power, and you're currently not in your gold era, this is the expected size of your capital. Example would be Vienna of 15th and 16th century(before Austrian and AH empires becaem a thing). As for non-capital cities, again, raise the bar of the country somewhat to at least a large kingdom during somewhat properous time.
Here, have a [source](https://en.wikipedia.org/wiki/List_of_largest_cities_throughout_history) for the largest cities of their time period and another [one](https://en.wikipedia.org/wiki/Historical_urban_community_sizes) for large ones.
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**The Question**
Is a theoretical 2/3rds - 7/10ths Earth big enough to have the magnetic field, atmosphere and plate tectonics to do this, or will I wind up geologically killing the planet?
I have been toying with the idea of some kind of 31st & 1/2 Century space adventure story. Basically, at this point, humanity has managed to come together enough to develop fusion technology, and explore space in earnest for the last few hundred years. There's no magic, no replicators (but there are nanobots and asteroid mining), no warp drives (but there are relativistic speeds attainable, topping out at about .95c; and suspended animation for people and robot ship crews). It is also assumed:
Lightspeed is a "hard" barrier for the foreseeable future, and affects travel and comms. Colonies are intended to be permanent. The Motherships can continue to sustain life to get the settlement established; if things go catastrophically wrong, there is a factor of safety timewise to abort the mission and return to Earth, or stay for a few generations; but it's an either-or.
There very likely are intelligent beings in the Universe, but they exist too far away from us to visit or communicate. If there are hyperintelligent beings that have surmounted these problems, we are too primitive to be of interest to them.
Humanity has, by this point, established permanent settlements beyond the Solar System. This one would be the 5th extrasolar colony, and still within 60Ly of Earth.
**The hypothetical Planet X would have the following characteristics:**
Edited based on contributions.
Star: FxV type; Planet X is in both the Conservative Habitable Zone and UV Habitable Zone (with a thicker ozone layer than Earth's)
Age: 1.3 - 3Gy. Not enough time to develop intelligent life, but that's not a problem, because humans are arriving from off-world.
Mass: 0.65 - 0.7 Earth-masses
Radius: 0.965 - 1.02 Earth-radii (less dense silicates, nearly pure iron core)
Gravity: 0.68-0.7 G.
Satellites: 1; with a large iron core, about 0.011 +/- 0.003 planetary masses. Appears smaller than Earth's moon due to much greater density. Slightly higher albedo than Earth's Moon. In stable orbit 105 +/- 5% of the distance the Moon is relative to Earth.
Atmosphere: ~1 earth-atmosphere at sea level; 25% oxygen, remainder inert and trace gases, more ozone, more xenon compared to Earth.
Average Surface Temperature: 278.5K, +5.35 C.
Rotation Speed: Somewhat faster than Earth's, resulting in a 17-19 hour day-night cycle, and likely strong winds and very apparent aurorae.
Axial Tilt: About the same as Earth's, resulting in distinct seasons.
Oceans of liquid water exist, as do large polar icecaps. ~30% of the surface is land, although extensive glaciation at the poles make it difficult to tell whether the poles are land or ice.
The planet is home to plant life, mostly algae and kelp-like plants in its oceans; early zooplankton may be starting to develop. On land, lichens, mosses; tall, spindly trees, but no multicellular animal life.
My biggest concern for a sub-Earth sized planet around a brighter and hotter star would be having a big enough active iron core to keep a strong enough magnetic field to resist the stronger solar wind, (despite the greater distance), and yet still have enough silicates left for plate tectonics. I figure a big, ferrous moon will help, through the tidal forces it will exert, along with the rapid rate of rotation.
Does this planet have all the necessary ingredients to maintain an active core, tectonics, magnetosphere and atmosphere, or would it be a geological time bomb?
[Answer]
Naively, yes, this world should be able to support human life. The temperature is low enough and the mass is high enough for it to be able to retain the necessary atmospheric components such as nitrogen, oxygen, water and carbon dioxide, without retaining hydrogen or helium.
Plate tectonics wouldn't strictly be necessary for the world to be able to support life.
However, there are innumerable other factors that may make or break this world as a potential home for humanity. Put simply, there are substances, such as cyanides, that the local life forms may produce that would poison the world for humanity, and require that humans use breathing apparatus. The low gravity may cause health issues long-term. The local life-forms may find humans to be an excellent growth medium and cause disease, or they may be incompatible with human biology to the point of uselesness or toxicity. The local plants will probably grow better there than terrestrial plants, which will make farming terrestrial plants difficult.
The low average temperature is going to mean that humans are going to need heavier clothing even in equatorial areas, which will mean that the colonists are going to have to grow or find things to make into clothes. Clothing will also be necessary in order to protect from excessive UV exposure from the F-type star.
As for the star, F-type stars have a lifespan of 2-4 billion years before moving into their giant phase, so this 1.3-3 billion-year-old star could quite easily be on the verge of turning into a red giant. It wouldn't happen overnight, but solar expansion might become an issue in a million years or less... not significant over a human lifespan or even the lifespan of a human society, but it ought to be an issue of concern for the colonists if they're thinking long-term.
[Answer]
Plate tectonics seems pretty much necessary.
1. In absence of plate tectonics there is no orogeny. Just erosion. In the 3 Gy timespan pretty much all the landmass would be washed into the oceans. That includes sulphur and phosphorus, which are essential to life.
2. In absence of plate tectonics there is no volcanic activity. The heavy elements percolated down below long ago. No lead, copper, iron within easy reach.
3. No fossil fuels obviously (no uranium within easy reach as well). Looks like a problem with heating for your colony.
[Answer]
# Orogeny
Not having plate tectonics is a bit of a problem because this would probably reduce the number of continents and islands. Without plate tectonics, the planet would not really be able to separate a supercontinent into several other continents or develop volcanoes. You would need volcanoes so that landforms could exist separate from the ocean. Maybe you could say that pressure built up and the volcanoes violently ripped through the crust, but that would probably take significantly longer because of the fewer eruptions. Or maybe you could have an asteroid collision release lava onto the planet, but this would be a one time event, and unlikely, too.
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# CO2 Cycle
Another problem with not having volcanoes is that CO2 might be in short demand. Plants would not be able to exist without frequent eruptions, because they would consume all the CO2 and then die. Maybe you could make “nocturnal” plants in addition to “diurnal” plants, because it is a known phenomenon that (“diurnal”) plants can consume oxygen and release carbon during the night.
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## Comments
Also, you are a world builder, you can really do whatever you want and many people probably wouldn’t even take the time to try to figure out whether your world is realistic. Anyone who might want to would need to program a complicated simulation with all the parameters listed in your question. The only people I can think of who would do that are the game theorists, and they closed off the opportunity for a ‘book theory’ when they made the style theorists.
Lastly, I wanted to mention that due to time dilation, you do not even need sleep chambers because at those speeds they will only experience seconds before they reach their destination. This also means that they can come and go without needing extra rations or something. The only disadvantage is that time outside the ship will pass normally, and relatives would pass with it.
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# Setting
The future, but not too far. No antimatter and no teleportation. Space travel is relatively reliable, but it's not cheap and it's powered by fusion. Space travel outside of the solar system is possible only via generational ships, which takes **very** long time, or via wormholes.
# Whormhole design
Wormholes are created by capturing a wormhole-carrying particle(WCP). This particle has an entangled counterpart, and both were created shortly after the Big Bang.
The size of the tunnel depends on the amount of energy dumped into the wormhole. The trick to trigger the opening is to archive very high energy density, so the tunnel opens via a laser-like device. It behaves like a proton-sized spherical mirror, but instead of reflection, it shows the other side. It is possible to look for the light and other EM radiation of the other side right after it opens. Dumping more energy makes the wormhole wider. Eventually, after years of growth, even a spaceship can traverse it.
Pairs of particles are scattered through the observable and unobservable universe. It is statistically impossible to capture two WCPs that belong to the same pair. It is impossible to know in advance what is on the other side.
Wormholes are fertile ground for all kinds of paradoxes. The solution for this setting is that wormhole opens *only* if its counterpart is on the *other* side of the [cosmological horizon](https://en.wikipedia.org/wiki/Cosmological_horizon). That includes other wormholes to avoid paradoxes entirely.
If it is possible for light to travel between two paired particles the tunnel will not open.
The most relevant cosmological horizon is [Hubble horizon](https://en.wikipedia.org/wiki/Cosmological_horizon#Hubble_horizon). The universe is expanding, and the rate of expansion is proportional to the distance. So some parts of the universe are unreachable by the light from Earth. In other words, these wormholes are leading only to parts of the unobservable universe.
# Consequences (world rules)
**Rule #1:** Once somebody opens the wormhole, it is the only way to reach the other side. The other side becomes part of the observable universe, and there is no way to reach it through other WCPs.
**Rule #2:** Independent of any particular WCP design, there is a very slim chance to create a second tunnel to the same spot in the universe (this is an exception to Rule #1). So once it closes there is no way to reconnect.
*The convenient side effect of Rule #2 is that it is almost impossible to wage war through the tunnel. It is somewhat similar to nuclear deterrence but in space. If there is a conflict between two solar systems, it looks more like the Cold War in space, instead of WW2 in space.*
The search for a useful wormhole is usually done via brute search through available WCPs and checking the surroundings on the other side as soon as the tunnel permits it.
No one wants a wormhole to empty space, except maybe for research purposes. The space is big, so the vast majority of the wormholes would lead to unusable locations.
# The Question
How to find aliens if the only way to travel interstellar (and greater) distances is to open a portal into a random place in the universe?
There are two ideas that I came up with:
* WCP properties. Originally, I thought that WCP could resemble dark matter, but it seems like its distribution (as dark matter is thought to be) would leave no chance of opening a portal into anywhere except galaxy centers and other places that are not friendly to any kind of life.
* Universe properties. According to the Cosmological principle, the universe is isotropic on a large scale. Thus there is no way to have some particular place to naturally meet. Maybe it is possible to come up with some feature that is significantly rare to be a meeting point, but frequent enough to encounter while opening wormholes.
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P.S. The intention behind WCPs is to remove wormhole creators, so the solutions involving those are not viable for me.
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EDIT:
Following @(Ethan Maness)'s answer, I think it is a good idea to make the wormhole decay if left unattended. This will prevent the situation when some civilization opened so many wormholes, the whole universe will eventually be connected by created Hubble volumes.
The other thing that came up during the discussion is that provided there is some civilization density in the universe and no growth restrictions for them, inevitably all the universe will be connected even with the decay. So some growth limit is highly advised.
[Answer]
# Frame Challenge
**Rule 1 has got to go.**
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The brute force strategy is required to find aliens, WCPs, or anything else. Just keep opening as many WCPs as you can to find whatever you're looking for. The problem is that ***everyone is going to be doing this***. No matter how you distribute WCPs, avoiding paradoxes by arbitrarily preventing light-cone intersection has two big problems:
* More advanced civilizations are completely unreachable
* The entire universe will become the observable universe
## Unreachable Aliens
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Ordinarily, the assumption in sci-fi is that it is much easier to find big advanced civilizations than small ones, because they are much bigger and louder. Humanity is entirely invisible from more than a hundred light-years away, but a million-year-old Dyson swarm could be spotted at a distance of, well, a million light-years. Since space is 3-dimensional, the volume of space from which something is visible scales cubically, so that Dyson swarm is visible from 1 trillion times as many planets.
Rule 1 totally flips this on its head by making space exploration mutually exclusive. If aliens open a wormhole within our Hubble horizon before we open one within theirs, it will be the only wormhole that can be created between us, and we won't know where it is.
This means it is actually much, much harder to find more advanced civilizations than less advanced ones—WCPs provide an easy way to find untapped resources, so any advanced civilization will have been opening many, many WCPs, constantly, for a very, very long time. The odds of us making the connection first are slim.
If a WCP is opened between the Hubble horizons of any two civilizations A and B, the probability $p\_{A}$ that it was opened by Civilization A equals the ratio between the number of WCPs opened by Civilization A and the total number of WCPs opened by both.
$p\_{A} = \frac{N\_{A}}{N\_{A}+N\_{B}}$
The number of WCPs a civilization has opened can be expressed as the integral of the rate at which they open WCPs over the time period since they started opening them.
$N(t) = {\huge\int}\_{t\_{start}}^{t\_{now}} \! R(t) \, \mathrm{d}t$
In other words, civilizations even slightly older than us will have created such a larger number of wormholes that it will be almost guaranteed that the single wormhole created between our horizon and theirs would be created by them. The universe is very old, so any civilization which already exists is likely to be many millions of years older than us and will be vacuuming up WCPs at an unfathomable rate.
Also, keep in mind that the Hubble horizon distance is *13,000,000,000 light-years*. The vast, vast majority of wormholes connecting the horizons of two civilizations will not actually result in them finding each other, since there are no other methods of superluminal travel.
#### An Example
Let's do some napkin math. For simplicity, we'll assume the following:
* All civilizations increase their power generation by 1% per year
* All civilization discover WCPs at around Kardashev 0.8 (for humanity, this is around 2200 CE)
* The proportion of all civilizations' power spent on wormholes is roughly the same
* The energy spent per wormhole is roughly the same
With these assumptions, $R(T) = k \cdot 1.01^T$, where $T$ is the number of years since discovering WCPs. This gives us formulas directly relating the age of a civilization with the number of wormholes they've created.
$N(T) = \frac{k}{\ln 1.01} (1.01^T - 1)$
$p\_{A} = \frac{N(T\_{A})}{N(T\_{A})+N(T\_{B})} = \frac{1.01^{T\_{A}} - 1}{1.01^{T\_{A}} + 1.01^{T\_{B}} - 2}$
Let's say Civilization A is humanity, and Civilization B is another young civilization which discovered WCPs a millennium before humans (in 1200 CE). By the start of the 24th century, one hundred years after humanity's first wormhole, a wormhole created between the Hubble horizons of Earth and Civilization B has a 1-in-300,000 chance of having been created from the human side. These will gradually improve, but they will *never* exceed 1-in-21,000, because exponential growth means that Civilization B will always be around 0.4 Kardashev ahead of us. Normally, advanced civilizations' growth rate would slow down over time due to the light speed limit, but with WCPs that's not an issue.
A civilization being such a similar age to our own is extremely unlikely. Every thousand years of separation reduces $p\_{A}$ by another factor of 21,000. If Civilization B is a million years older than us (which is still very close), the odds are roughly $10^{-4,300}\%$.
We are not finding any aliens.
## Causal Separation Collapse
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Let's pick some arbitrary numbers. The largest nuclear explosion in human history, Tsar Bomba, released 200 **petajoules** of energy. A modern nuclear power plant would have to run for seven years to produce that much energy.
Assume that it takes that much energy to open just *one* wormhole large enough to see through. In the setting of your story, let's say humanity uses about 10x as much energy as it does today, and that 0.1% of that is used for opening WCPs.
In this scenario, humanity would open about 20 wormholes a year. We would almost certainly find nothing of value on the other side of any of these wormholes. Nevertheless, with each wormhole opened we expand the volume of our observable universe by an additional Hubble volume, which is $361 \, \text{Gpc}^3$, or $12.5 \times 10^{31} \, \text{ly}^3$.
When a civilization starts opening WCPs, they are essentially building a connected graph of wormholes. If I create two wormholes, both of which connect our solar system to locations previously outside of Earth's future light cone, those two locations are now also casually connected, through Earth, like [nodes on a graph](https://en.wikipedia.org/wiki/Graph_theory). The more wormholes we create, the larger our graph becomes, but it will always be a [connected graph](https://en.wikipedia.org/wiki/Connectivity_(graph_theory)) because one end of the wormhole will always be within our observable universe.
Let's consider that civilization from earlier which was a million years old and opened around $10^{4,000}$ times as many WPCs. That means that their observable universe expands by roughly $10^{4,000} \, \text{ly}^3/\text{yr}$. To understand how big of a number that is, if we change the units from "cubic light-years per year" to "Hubble volumes per femtosecond", the exponent is still about 4,000. Yet, give it another million years and it becomes 8,000. Exponential growth, am I right?
Keep in mind, this is a *young* civilization on cosmic time scales. A billion year old civilization will be eating around $10^{4,000,000} \, \text{ly}^3/\text{yr}$. That's a lot of space. So, what's the issue?
**Rule 1 says that you can't create a second wormhole to a region that is already within your observable universe.**
Ancient civilizations will swallow the entire universe into one single causal bubble and WCPs will become completely inert. This will almost certainly happen before life on Earth ever crawls out of the ocean. Here is why:
If Civilization A creates a wormhole to a location inside of any of Civilization B's 13,000,000,000 light-year wide observable bubbles, their two previously-disjoint universes are now one casually-connected observable universe within which neither can ever create another wormhole.
When civilizations start popping up and making wormholes, they will eat up huge volumes of the universe. If the universe is infinite, there is an infinite amount of volume to eat up. However, there are also an infinite number of civilizations eating it, and this infinity is growing.
Once the oldest civilizations reach a causal volume larger than the civilizations-to-volume ratio of the universe, it's over. We don't know how early life could have started forming in the universe, but we know it's at least 4 billion years ago. By the time humans show up, the oldest civilizations' causal volumes will be at least $10^{10,000,000,000,000,000,000,000,000} \, \text{ly}^3$, *each*. Unless the universe is so sparsely populated that civilizations are, on average, at least that many light-years apart, we will be too late to make wormholes at all.
## Solution
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You need a different way to prevent paradoxes. Fortunately, wormholes are only actually "fertile ground" for *one* paradox, time travel. Subjecting one end of the wormhole to time dilation (e.g. via a gravity well or relativistic speeds), the two ends become temporally de-synchronous and travel through them becomes time travel.
All you really need to do to fix the causality problem is have wormholes operate in an absolute frame of reference, temporally at least. I know, Einstein is rolling in his grave, but it's sci-fi not sci-reality and frankly this requires less suspension of disbelief than Rule 1 anyways. If you just say that wormholes are always in sync, there's no way to time travel and no paradoxes can happen.
Without Rule 1, both of the big issues go away. Ancient civilizations will still dominate the entire universe thanks to the lack of a speed limit, but they might not notice you so that's fine.
# A Side Note
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[](https://i.stack.imgur.com/sFNoP.jpg)
You stated that you initially rejected the "WCPs are dark matter" idea.
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> Originally, I thought that WCP could resemble dark matter, but it seems like its distribution (as dark matter is thought to be) would leave no chance of opening a portal into anywhere except galaxy centers and other places that are not friendly to any kind of life.
>
>
>
This is false. As we currently understand it, dark matter is primary concentrated in halos around galaxies and galaxy clusters. Or, more accurately, galaxies are primarily concentrated in clusters of dark matter--dark matter is the driving gravitational force in the universe, and baryonic matter is sucked into its wells.
The baryonic matter of a galaxy typically occupies a much smaller volume than its dark matter halo. Furthermore, dark matter is distributed across the intergalactic space within a galaxy cluster, and along the filaments between clusters, so a randomly selected dark matter particle is almost guaranteed to be in the absolute middle of nowhere, with maybe one-in-a-thousand being inside of a galaxy. Queue the numbers game.
[Answer]
I'm not too clear on what a WCP would be in real life, but it seems that space-age civilizations are incentivized to open as many tiny wormholes as possible, scan the new solar system for liveable planets using the same methods we currently use when looking through telescopes, and chose to either ignore or colonize. Assuming that there are already one or more alien civilizations out there that have been using the same technology for a while, then once you get one lucky break and tunnel into an alien civilization's space, you can immediately tap into their entire network of wormholes.
However, it's far more likely that an alien civilization with much more resources at their disposal than humanity opens a wormhole into one of our solar systems before we open one into one of theirs. In a game of opening as many wormholes as possible and probing for alien life, aliens far away that have colonized many systems that produce enough energy to open hundreds of small wormholes a day have higher chances of finding us than we have of finding them.
It's kind of like that "paradox" that on average, your friends have a higher average number of friends than you. There are way more chances of being discovered by an alien than there are of discovering one because some wormhole tech early-adopter will be doing all of the discovering. This makes it very unlikely for humanity to meet a less or equally developed alien life-form so if this is what you want in your story, you might have to revisit the wormhole creation rules.
[Answer]
# Hole Ho!
The visible universe is homogeneous at large scales. Fortunately, at small scales, matter coalesces around the galactic centres:
[](https://i.stack.imgur.com/jjXNc.png)
You are free to declare that WCPs behave like regular matter in this regard, and there are more of them in the middle. That means to find many WCPs, simply head hole-ward.
As you get closer to the centre, you will find more WCPs. Open them all and check is the end any closer to the centre of its respective galaxy than the start is to its own centre. Proceed like this. You zip zap zoop between causal patches but you tend towards the centre of SOMETHING. And every step closer to the centre means more holes to open and more potential alien civs to encounter.
I think the best bet is an advanced alien civilisation discovering you, rather than you discovering them. The problem is that causal patches are big. Billions of Buzz Lightyears across.
Even if you and I are in different causal patches, and I know all the WCPs in my shoebox lead to your patch, then in all likelihood the first one I open will be many lightyears from your home planet. Plus opening that single WCP immediately kills off the potential wormholes from the other WCPs in the shoebox. So we both now have no hope to meet each other.
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In my world (based on D&D) orcs are a pre-metalworking society that clash with various agricultural humanoid civilizations. However, I would also like them to have metal weapons so they are a plausible threat to metallurgic civilizations, and I don't think that 'theft' is a good explanation.
Then, I realized I might be able to solve this problem in a way that ties in to other pre-established traits (high mortality rates, orc resistance to injury). What if the structural component of their bones isn't carbonated hydroxyapatite, but something different? I read a post which suggested that the issues of bone are that it doesn't hold an edge and tends to fracture easily: are there alternative molecules that don't have this problem?
Basically: is there a mineral that could plausibly be produced by biological processes, that'd serve as a structural component for bones, and that orcs could turn into workable spear tips and axe blades after extracting it from the fallen?
[Answer]
It has been already done by humans: allow me to introduce you the [leiomano](https://en.wikipedia.org/wiki/Leiomano)
[](https://i.stack.imgur.com/eLruX.jpg)
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> The leiomano is a shark-toothed club used by various Polynesian cultures, but mostly by the native Hawaiians.
>
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> Leiomano is a word in the Hawaiian language and may have been derived from lei o manō, which means "a shark's lei."
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> The weapon resembles a thick ping-pong paddle inset with shark teeth. The tiger shark is the preferred source. These teeth are placed into grooves in the club and sewn into place. The tip of the handle also may utilize a marlin bill as a dagger. The weapon functions as a bladed club similar to the obsidian-studded macuahuitl of the pre-Columbian Mesoamerican cultures.
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[Answer]
**Fecalith**
<https://en.wikipedia.org/wiki/Fecalith>
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> A fecalith is a stone made of feces. It is a hardening of feces into
> lumps of varying size and may occur anywhere in the intestinal tract
> but is typically found in the colon... It can possibly form secondary
> to fecal impaction. A fecaloma is a more severe form of fecal
> impaction, and a hardened fecaloma may be considered to be a giant
> fecalith. The term is from Greek líthos=stone
>
>
>
Fecaliths are extracted from the fallen. These stony masses are then crafted and polished by fecalithsmiths into deadly weapons. Among your people, it is typical for warriors to eat colored material and glitter so that they produce formidable fecaliths, in hopes that their spirits will endure after their own deaths, inhabiting the weapons they birthed. Or would have birthed eventually (and painfully (but they endure the pain being warriors)) if they had not fallen. A sort of warriorly post-mortem Caesarian birth; yes.
[Fecalith Causing Mechanical Bowel Obstruction Managed with Intracorporeal Lithotripsy](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843141/)
[](https://i.stack.imgur.com/wKM32.png)
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[Question]
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**Introduction**
A common image in time travel stories is an image of all time, either as a line or a tree form. Take this image from Loki as an example:
[](https://i.stack.imgur.com/nL2lo.jpg)
So a time traveller's organisation, like the one for my story, has a way to look at the "normal timeline", the one muggles live in, so that they can insert themselves at any point and make any changes necessary. They know the beginning and the end of the normal timeline and can see it all at once, so it is like they are looking from atop it - like a 3D person looking at 2D [Flatlanders](https://en.wikipedia.org/wiki/Flatland). This suggests they are in a different *temporal dimension* of their own. That is further supported by the fact that there is a timeline that the time travellers experience; events take place in their office which follow each other causally, there's a start of the time travel agency and an end to it. They are just as bound to time as we are, they are just natively on a different temporal dimension and they have the technology to look at the normal timeline as a whole.
**Multi-timeline specifics**
[](https://i.stack.imgur.com/xQt1O.png)
I have provided an illustration of my concept. The red flow of time (temporal dimension) is the "normal" one. On it is a timeline that changes over the course of the second temporal dimension. That means that at any given "moment", the red timeline starts at the start, ends at the end, and every event within it is causally related - or is it? I'll get back to that; but understand that it can't loop or branch, it's always a line. This timeline does constantly change as the blue time progresses; events move or change, the end may be expedited or delayed.
The blue time is the time of the time travellers. They exist natively to the blue timeline; they can see the red timeline from start to finish as it exists at that moment, and they of course keep records of what it used to look like. They can use that to make interventions, change events as they see fit, and add non-casuality to the red timeline. But the blue is causal; event 1 is followed by 2 and 3.
The blue time "interferes" with the red time passively, we call it quantum randomness. For every instance of a red timeline, the quantum dice were rolled in a specific way and that normally determined the order of events. When a *time traveller* visits the red timeline, they are manipulating quantum tunneling to materialise themselves at a place and time, seemingly out of thin air. Conservation of energy is still maintained in the red timeline however; they need to ensure those particles that form their body disappear somewhere else in the universe, or at least equivalent mass-energy.
**Question**
This idea really scratched an itch I have for stories featuring multiple dimensions, but it brought one issue to light. Can't the time travellers take their timeline-viewing machine, go into the normal timeline, turn the machine on and view their *own* temporal dimension from start to finish? Wouldn't they be able to see their *own* lives and deaths and actions? That would make plot involving the time travellers impossible and meaningless.
One can come up with mundane reasons why the timeline-viewing-tech may not be physically transportable to the Muggle Earth, but those feel like cop-outs. How can I make the impossibility of seeing the blue flow of time from start to finish an inherent property of the system, rather than something arbitrary like tech restrictions?
[Answer]
# Forced perspective
Let's take the flatland example even further lets say the flatlanders live on the surface of a table. Each timeline has a different table. On the underside of the roof is an extra flatland. Your time extra dimension.
Using the technology they can activate a camera in the ceiling, allowing them to see each of the tables. So far it is identical to the story.
Now what happens if the time travelers go from the ceiling to one of the tables and activate their device? The device shows just the tables. This is because the machine they take with them is just a display device. The technology picks up the cameras, allowing them to see through it. As the cameras are fixed to the ceiling the perspective never changes. As flatlanders they cannot interact with the cameras to change the perspective. They can never see the ceiling.
The technology only allows viewing from a forced perspective. The time travellers have managed to do things into higher dimensions, but are unable or not skillful/knowledgeable enough to change the perspective.
[Answer]
>
> Can't the time travellers take their timeline-viewing machine, go into the normal timeline, turn the machine on and view their own temporal dimension from start to finish?
>
>
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No, because their timeline takes place in the extra-temporal dimension that time-travelers use, meaning that it's not like a 3D looking onto a 2D flatland, its a 3D looking onto a 3D. In order to see a time traveler's timeline, you need the equivalent of a 4D view.
[Answer]
## No!
>
> Can't the time travellers take their timeline-viewing machine, go into the normal timeline, turn the machine on and view their own temporal dimension from start to finish?
>
>
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This question has a lot of assumptions baked into it that an engineer would laugh at.
To illustrate: a person might say, "my car radio in Milwaukee can receive transmissions from WGBH in Boston, so why can't WGBH pick up transmissions from my car radio?" I mean, gosh, they're both radios, right? Here, let me turn my car so it faces Boston -- is that better?
Of course, we know that it has to do with signal strength, energy requirements, and inconvenient properties of EM radiation, Earth's atmosphere and curvature: your car doesn't have a giant powerplant, an enormous antenna, or an array of repeating towers spread across the land. (Also, the typical car radio does not have a microphone.) My hypothetical questioner asks a question that is absurd because their understanding of how radios work is extremely superficial.
This is the same kind of mistake being made by a person who thinks that the timeline viewer can simply be relocated and pointed at a different timeline, as though that timeline were simply a different physical place and the viewer were a pair of binoculars. That is not what timelines are, and the question grossly misconceives what is involved in "observing" a perpendicular timeline.
First: information about perpendicular timelines is carried to the viewer via some kind of physical process. Maybe it receives waves/particles, or maybe it measures the motion of such things. There is no guarantee that this physical medium can carry information in the other direction. So, if you want it to be impossible in your story, then that's a real limitation.
Second: it assumes that the machine's observations depend upon its location and orientation, like a telescope. That does not have to be the case. Telescopes and binoculars capture and focus light, light which is already traveling in both directions between the observer and the observed, and so you *can* observe Hill 1 from Hill 2 by moving the telescope to Hill 2 and looking backward at Hill 1. But it's up to you to decide whether this mechanism works that way. Perhaps the physical medium is polarized, like light, and so a device like this can *only* see horizontal timelines no matter where or when it is located, rendering vertical timelines completely invisible to it. Or maybe they work like [cygnet detectors](https://apnews.com/article/74881d7999e15d58d22a49ef5e1c71c8), which are not "pointed" in any direction: one is built underground, where it waits to get hit by a cygnet coming from any direction at all.
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You ask:
>
> How can I make the impossibility of seeing the blue flow of time from start to finish an inherent property of the system
>
>
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For a start, you need to flesh out the fictional science of how timeline observation works. A straightforward approach might look like this:
1. Invent some kind of new particle whose job is to carry information about a timeline. Mainstream sci-fi sometimes uses "tachyon" for particles related to time/time-travel, so avoid that name like the plague. Call them "plagions."
2. Invent a story about how plagions interact with muggle spacetime such that they carry information about that spacetime. Questions this story could answer might include:
* Where do plagions come from?
* What is their movement like?
* Are they drawn towards anything, or repelled by anything? (Perhaps the timeline viewer works by using special materials or energies to *attract* plagions to it so that it can harvest their sweet info.)
* How is it that plagions are able to interact with an entire horizontal timeline instead of just its "present moment"? (Your answer to this might also explain why plagions aren't available to people or objects within horizontal timelines, which would then go a long way towards explaining why the timeline viewer won't work at all from a horizontal timeline.)
3. Invent a story about how the timeline viewer "reads" the information from plagions. Presumably, like a telescope, it must collect plagions that have physically visited the place you wish to observe. This might also be where you decide what kinds of information about the observed timeline is even available:
* Can the viewer read the thoughts of people in horizontal timelines?
* Does it only present some kind of fuzzy, imperfect information?
* Does it actually show a visual image of the observed timeline, like a camera or telescope?
* Does it have audio? Both? Neither? Maybe it just shows the heartbeats of every creature with a heart, and so events like wars and disasters are *inferred* by scientists when the data shows a drop in the number of beating hearts.
You only have to take this as far as you need in order to justify the limitation you're looking for. But, honestly, I think you don't even need to work out these details: the fact is that it's very common for laypeople to have absurdly oversimplified ideas about how complex technical or scientific things work, and so they end up with absurd notions when they try to extrapolate from that flawed foundation. You can do the same without having to handwave anything. And I really doubt that any audience will be interested in the gory details of a fictional new branch of physics.
Just say that the device can't work like that. Or say that they haven't *yet* figured out how to use it to observe their own vertical timeline -- which is probably how they would describe the situation, even if it were actually impossible, until they have conclusively proved that it can't be done.
[Answer]
Instead of having your travelers fully travel to a new universe and interact with it, they could “partially” travel to that universe. They are still tied to their native blue universe but able to interact with the new universe due to a field/device/technology which partially moves their bodies into the red universe. When that field is turned off, they revert back to their native universe. It becomes more like they are projecting a solid holographic body into the red universe, which can be affected by, and effect, that universe. This also avoids the issue of adding or subtracting matter between universes.
The reason why they cannot turn their timeline viewing machine on and look backwards into their own universe is because their machine is still technically in the blue universe. The thing preventing them from constructing a machine using matter from the red universe could be the lack of an element which is naturally occurring in the blue universe, but which never formed in the red universe due to slightly different laws of physics. Without the “temporium” element, there is no way to create a timeline-viewing machine and look outward from the red universes.
This slight difference in the laws of each type of universe could be what prevents them from fully transitioning between universes. Matter from one universe cannot exist in the other, as the laws of physics do not allow for it, thus the need for the “holographic” bodies. This would also prevent technology and biology from contaminating other universes. Alien microbes cannot fall off a time traveler and infect the locals since they are not actually there to begin with. A pickpocket which steals a traveler’s advanced tech smart phone would see that device disappear once the traveler left the red universe. Kind of a built in safety measure.
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[Question]
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I want to write a story that has a [Pangaean](https://en.wikipedia.org/wiki/Pangaea) like world, but human civilization already existed during that era. Basically, the earth just has one giant piece of land while the rest is the sea.
People don't venture to the seas, because there are no lands to find, only fish. And every single humans living there are culturally the same, due to being ruled by one ruler in the center of the unified land.
But, something happened, something tore apart the land, tearing the unified land apart into countless islands. It was so sudden, the people couldn't believe that their world could be torn apart literally.
Now my question :
What is a believable reason for the land to be split apart, but still have at least 50% of the human population survive? If that is not naturally possible, what kind of magic that will produce that result, but still makes it seem natural? I want my story to be low-fantasy.
Note :
The era of civilization when the "split" happens is the medieval era, the days of swords and shields.
[Answer]
**Sea level rise**
Pangaea doesn't actually have to split. A rise in sea level will leave the low-lying areas underwater, while the higher-elevation areas will form island chains.
One thing that could cause something like this would be polar ice caps melting. I don't think there is any way this could happen within one generation, so magic would have to be involved.
[Answer]
# The splitting of Pangea
There's actually an easy answer to this. Our planet has a molten core that isn't fixed to equivalent points on the crust. A mere 200 million years ago, the orientation of the core shifted in such a way that upward currents of magma that were previously directed at oceans were instead pushing up in the middle of the Pangean continent, splitting it apart.
The tectonic upheavals preceding the splitting of Pangea are one of the things cited as causing the Triassic - Jurassic extinction that allowed the dinosaurs to gain dominance. They did, however, take about 10,000 years to actually kill everything.
Our core is also magnetic. If a strong magnet happened to fly past the planet, it could easily have shifted the core in such a manner. Overall, there's plenty of leeway for you to insert artistic license in such a scenario.
[Answer]
**Postapocalyptic wastelands turn your surviving settlements into islands**
<https://en.wikipedia.org/wiki/Fallout_(series)>
>
> In the years after the Great War, the United States has devolved into
> a post-apocalyptic environment commonly dubbed "the Wasteland". The
> Great War and subsequent nuclear Armageddon had severely depopulated
> the country, leaving large expanses of property decaying from neglect.
> In addition, virtually all food and water is irradiated and most
> lifeforms have mutated due to high radiation combined with mutagens of
> varied origins. Despite the large-scale devastation, some areas were
> fortunate enough to survive the nuclear apocalypse relatively
> unscathed, even possessing non-irradiated water, flora, and fauna.
> However, these areas are exceedingly rare...
>
>
>
Fallout is just the latest iteration in this scheme. Postapocalytic wastelands are perenially popular for fiction. Sword of Shannara, anyone? Anyone? Hiero's Journey? Yes. Bad stuff is out there in the wasteland, and the people who are left hunker down in their walled communities which are for all intents and purposes the islands you request.
The reason this is popular is that the wastelands are unknown, full of monsters, schemers, treasures of the world that was, heirs to the throne, psychic mooses (best part of Hiero!) and whatever else you need. Not that your world cant have that stuff under the waves but you will need Kevin Costner to dive down and fetch it for you.
You can have the wastelands come to be in a way that makes sense. Maybe the Empire falls and there is no more law - monsters move back in. Maybe there was a war of some sort or a plague (some combo of those two I think are responsible for the ELden Ring world). Zombies? Restless spirits? Magic badness gone extra bad? Triffids? All time tested and effective.
[Answer]
Very soft fantasy,
The world is actually a millenium ship
The core itself is the machinary
The entire biosphere is basically just "grease growing in between the machine parts"
Well ok, algie and stuff that covered the real machine underneath
A sudden shift like that could be explain by the machine doing a regular "system check"
And there were legends that "the unified Pangea" were once upon a time many islands
Or maybe be a bit more cliche and just say something something accidentally awakened the machine,
Now time to figure out why there would be a millenium ship,
Maybe it's created by a advanced civilization to escape some great world ending Eldridge god, and the original biosphere within the ship failed, and life has slowly got it's way on the surface and revolved to popularize the surface,
Why would it be orbiting a sun if it's a millenium ship then?
Maybe that was it's final destination,
And it arrived eons ago,
But due the the failed biosphere on the way, no one was there to try recolonize the star system, until life naturally evolved on the surface of the machine,
And + a millenium ship as a planet, that can keep doing system checks, would require magic,
[Answer]
Pangaea existed here on Earth, and over time ours split into the continents that we know today. Eventually, they may return to a different Pangaea like formation, though possibly different than the one before it.
So as long as your world has those same tectonic plates, such a split is possible. Now for the (somewhat apocalyptic) solution, given that there is a fantasy tag in play here ...
**Magic went horribly awry**
What that magic was exactly, and how that relates to the magic now is not necessarily for the readers to know. What is known by the layman is that there was a calamity and the land heaved and the earth was torn asunder. Lands fled from each other and gaping waters flooded in to keep the lands separated. Who did it is up to you and the needs of your story.
The power of what happened, either by design, through failsafe, or through pure random chance, surged through the tectonic plates of the world. The process accelerated the natural process of your world's Pangaea splitting, causing the appearance of the land heaving. Effectively, your planet's tectonic activity has gone through millions of years in only a few years
Of course, such an abrupt shift in the world is bound to basically be an apocalypse waiting to happen. That is where the runaway magic comes in. The very magic of the world itself was consumed in preventing the end of all life as we know it by severely dampening the volcanic activities that creates the new lands, and preventing the seas from dropping in the chasms opened in the plates in the oceans, and all the immediate problems. There were still natural disasters, but compared to that they should have been -- the world got off lightly.
But not everything can be stopped. Some land masses will move into more inhospitable areas and people there may die out through starvation or predation. Entire villages will disappear into the earth where the fault lines gaped open and left naught but a void and doom. Floods and other disasters caused buy the shifting lands will rewrite the world, causing upheaval.
Depending on where the landmasses travel and how people were spread out over your supercontinent, will help determine those that would perish sooner over later.
The epicentre of the calamity, naturally, has been destroyed beyond recognition
**The Aftermath**
However such an calamitous endeavour has left the magic of the world weak and recovering very slowly, even as the aftershocks of a calamity long ago still rumble across the lands. Magic has been left permanently scarred and weaker, in the low fantasy state that you are desiring.
Without modern technology to fail, the people of the world can carry on without too much interruption to their skill sets. The main problem is that crops that might have thrived before could fail while others that failed could now thrive. But the practices of farming are still similar, and we humans are tenacious if nothing else.
Certain resources may be an issue in these spread out lands, which could be an interesting world building point.
The lack of technology at the time of the calamity means that there won't be a backslide in that regard. People will adapt to the new landscape and climate, as will the flora and fauna ... hopefully.
**Interesting points**
* Water travel should be at least known for its ability to carry goods more efficiently over water than land.
+ I would expect that the tech is stalled as really only river and small lake travel would be needed in quantity.
+ There could easily be a boom in shipbuilding triggered by advances if the condition is right
* There is likely an uneven split of resources in this newly split world
* There might be theories or inventions that were once regarded as novelties in the world before that become important now.
* A shift in the flora and fauna populations of the world will happen due to the changing of the lands -- how humans deal with that may be interesting.
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[Question]
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In an alternate timeline where Mars is the second Earth-like planet in our Solar System, the drive for colonizing it would perhaps have been much stronger. There would've been more resources spent exploring it and studying its countless species completety unrelated to life on Earth. The first manned mission might even have been launched right before the dawn of the 21st century! But for that to happen, there needs to be some prerequisites, prerequisites that strech all the way back to 4.5 billion years ago, back when the planet was formed.
Mars resides in the outer reaches of the habitable zone around the Sun. If it had an atmosphere like Earth, with the same greenhouse effect like Earth, it would've been just another colder, icier version of our planet, with a more turbulent global climate cycle (due to it not having a large moon to moderate its axial wobbling). The reason why it's arid and barren today, is because it lost its magnetic field, allowing the solar wind to blow away most of its atmosphere. Atmospheric loss was rapid because Mars only has 10.7% the mass of the Earth. The low mass might also be why the magnetic field decayed so early. Without sufficient atmospheric pressure, liquid water would boil away, split into hydrogen and oxygen, with the oxygen getting absorbed into minerals on the ground and the hydrogen blown off into space by the solar wind.
But what if, Mars formed with more mass, especially with enough iron to retain its magnetic field until today, or at least enough mass to hold onto a thicker atmosphere till today? How much more mass does it need from the start in order to be another Earth-like planet today, ready for human exploration?
[Answer]
It's not only a matter of mass...
We know that Venus, with 0.815 Earth masses, has been capable of retaining an atmosphere, despite being closer to the Sun than Earth, and thus experiencing a more intense solar wind.
However, [its magnetic field](https://en.wikipedia.org/wiki/Venus#Magnetic_field_and_core) is way weaker
>
> The lack of an intrinsic magnetic field at Venus was surprising, given that it is similar to Earth in size and was expected also to contain a dynamo at its core. A dynamo requires three things: a conducting liquid, rotation, and convection. The core is thought to be electrically conductive and, although its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo. This implies that the dynamo is missing because of a lack of convection in Venus's core. On Earth, convection occurs in the liquid outer layer of the core because the bottom of the liquid layer is much higher in temperature than the top. On Venus, a global resurfacing event may have shut down plate tectonics and led to a reduced heat flux through the crust. This insulating effect would cause the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, no internal geodynamo is available to drive a magnetic field. Instead, the heat from the core is reheating the crust.
>
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But, despite the lack of a magnetic field, the atmosphere is still there.
To answer your question then, based on the amazing statistics based on two data points, the mass should be at least 0.815 Earth masses.
[Answer]
**Nobody Knows**
For one thing, mass alone is not a sufficient determiner of habitability. Composition also matters, and the minimum mass may be wildly different for different compositions (even if we only want to consider planets with habitable *surfaces*, as opposed to subsurface oceans). This is kind of extreme, and may or may be actually realistic, but in *Still River*, for example, Hal Clement describes the planet Enigma-88, which is only habitable because it randomly started out with such a huge load of outgas-able volatiles that it is still replenishing a high-pressure surface atmosphere from internal supplies even after a billion years of losing atmosphere like a comet! (And in fact, we have found exoplanets that are billions of years old and appear to have cometary tails; granted, they are all gas giants, but given enough time to keep losing atmosphere, they eventually won't be....)
If you look at [the Wikipedia page for Planetary Habitability](https://en.wikipedia.org/wiki/Planetary_habitability#Mass), the references for planetary mass ranges are *all over the place*. Some people put it at 0.3 Earth masses--which is actually smaller than Mars! (I guess it just needed a different composition to maintain its magnetic field? Or a moon to stir its interior with tides?) Others conclude that Earth itself is actually right on the edge of habitability--so a habitable equivalent of Mars would actually need to be *at least* as big as Earth itself. This is the approach taken by Harry Turtledove for his alt-Mars (named "Minerva") in the novel [A World of Difference](https://en.wikipedia.org/wiki/A_World_of_Difference_(novel)).
So... who knows? We will need to see a lot more planets in a lot more detail before anyone can say for sure.
[Answer]
Actually I recently ansered this question about inceasing the gravity of Mars:
[What are the effects of Increasing the gravity on Mars?](https://worldbuilding.stackexchange.com/questions/230327/what-are-the-effects-of-increasing-the-gravity-on-mars/230359#230359)
One of many questions about the minimum mass of habitable planets I have answered.
Here is a link to a question which I answer in much more detail, too much detail for me to want to repeat here:
[Would 25% less gravity produce dramatic differences in animal morphology?](https://worldbuilding.stackexchange.com/questions/230258/would-25-less-gravity-produce-dramatic-differences-in-animal-morphology/230325#230325)
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[Question]
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I have some species of aliens that have pseudopodia, less like the temporary protrusions of amoeba but more like the retractable eye stalks of snails. Their body is covered in areas where limbs can protrude from by forcing blood into that area.
Their organs have a degree of movement within their body. They are similar to blob creatures but with less freedom and liquidity in their form. They can shape their body to most simple shapes and add detail with temporary limb structures. When they need to move or interact with things temporary limbs can protrude and retract when the their job is done.
Would a creature that can change its shape and has temporary limbs have a default/resting shape and what would be the most efficient shape if they did?
[Answer]
From what you describe, these creatures seem primarily composed of organs, muscle tissue, connective tissues, and vascular structures. The "default" resting shape can be determined by:
* Skin thickness and flexibility.
* Firmness of muscle tissue.
* Connective tissues between muscles.
* Blood pressure.
* Gravity.
* Shape of its immediate surroundings.
Invertebrates can hold their shape, even in a resting position. Relaxed muscles will probably make the creature conform more to its surroundings, but not become a puddle.
Generally, the resting position of an animal will balance energy conservation with positioning itself to react to changes in its surroundings.
Unless a scientific explanation for this shape is necessary for plot development, choose a shape that best fits the story and the plot elements this creature satisfies. For instance, if this creature needs to lay still in order to ambush prey or opponents, make the creature as flexible as you need to hide in whichever places and shapes that you want.
[Answer]
**What's the weather like?**
It occurs to me that the answer to this question depends quite a lot on the creatures environment. On a very basic level, if this is a cold environment, and the creature is concerned with maintaining body temperature, then it will seek to minimise its surface area by tucking itself into a ball shape, and therefore retracting its pseudopods. If, however, the creature lives in a hot environment, and is more concerned with venting out surplus body heat, then I can imagine it would want to keep its extremities elongated, specifically for the purpose of radiating out body heat.
[Answer]
I would probably say that a convenient resting position would be like a flat circle. To stick out a limb would imply the use of energy, so a circular shape would ensure that essentially no energy is exerted.
[Answer]
## It will probably be Worm or Slug like.
[](https://i.stack.imgur.com/iWMBL.png)
Before you can exactly answer this question you first need to figure out the organism's pattern of symmetry. Every multicellular organism can be generally classified as Asymmetrical (Sponges and some Plants and Fungi), Radially Symmetrical (Jellyfish, Starfish, most plants, etc.), or Bilaterally Symmetrical (Most animals).
If we assume your alien is evolved enough to be able to use these temporary limbs to some effect, we should assume it has some kind of complex organ structure as most animals, meaning it will probably have some kind of Bilaterally Symmetry which is helpful for designing things like uni-directional digestive tracts, and minimizing organ redundancy.
As for the other aspects of its shape, its degree of flexibility means it has a generally fluid like internal structure. This suggests that it's skin will probably obey some kind of surface tension like rules when at rest.
The best example we have of this in the real world is the Amoeba. Even though it's able to form itself into distinctly asymmetric shapes, at rest it prefers a generally worm like shape.
[](https://i.stack.imgur.com/8Pl6n.png)
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[Question]
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As we all know, King Midas wished that everything he touched would turn to gold - his wish was granted by the god Dionyssus. This proved to be his undoing. He couldn't eat because his food turned to gold.
We know from the myth that he was still able to breathe and bathe so we can **assume that only solids are affected by his touch**.
KM's advisors have found a way to feed him. They use a flexible gold tube to introduce liquidised mush directly into his stomach. The sages are not sure why this works (a) maybe he is fine because the food is liquidised and therefore not solid or (b) stomach acid and mucus prevent the food from touching his skin directly and so he is able to digest it.
They also make him bedding, clothes, shoes and gloves of finely-spun gold so that he never needs to touch anything solid directly.
I think he can now continue to live but am I right? Is there something I have missed that will make his survival impossible? Or is there always a way around it?
[Answer]
Animal bites and stings are a big risk:
* bees, wasps and mosquitoes would turn into thin golden needles stuck in his skin,
* cats happening to pounce him would turn into golden blades carving his skin
* dogs biting him would become stuck in the bite
* accidentally stepping on a sea urchin would gift him with dozens of golden needles
Also his private life would be affected: he will need to kiss farewell to any physical contact, no matter how intimate.
Going out will become a risk: anything or anybody falling or hitting him will become a golden burden. Falling twigs, sand blown by the wind, birds dropping...
[Answer]
As a monarch he would still be as, if not more, susceptible to attacks. For example a villager with a wooden club becomes a villager with a block of gold, making attacks more brutal. Why spend money on arrows when wooden ones will do the trick?
With more people wanting to get close to him for monetary reasons, increases chance of infection, disease, virus, plague, etc.
Any injury from smallest to the biggest has a higher chance of death.
* scrap: can't bandage it (either get golden bracelet or a curved golden piece that doesn't stick) so open wound has increase risk of infection
* broken bones from fall: can't brace it (how would you remove solid gold brace?), moving becomes difficult without risk of aggravating injury
* vision? if his vision goes would whole glasses transform or just the frames? (risk of missing step, threat, friendly)
Something else to consider that while it may not be a detriment to living maybe a concern is when he has to go to the loo, does he have a bidet?
[Answer]
# You'll have trouble in the long run
You've managed to feed King Midas. Great. Now what comes next?
There are two options: either the material he excretes is susceptible turned to gold, in which case he is due for a *very hard* time on his golden throne ... or it isn't, which means it counts as part of King Midas and will continue turning anything it touches to gold. The second seems more likely since I don't think his tears, etc. turn to gold (otherwise can he see?)
This means you now have a Golden Toxic Waste Dump in which you carefully deposit excreted substances. Either that or you make Golden Landmines out of them to kill enemy troops, with the caveat that I'm not quite sure why they or Midas' footsteps don't convert "The Earth" to gold, or at least a contiguous rocky part of it.
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**Aqua Regia**
I am not sure exactly how he would use it, but I think Midas would have some use for [aqua regia](https://en.m.wikipedia.org/wiki/Aqua_regia), a.k.a. Royal Water, one of the few things that can dissolve gold.
Perhaps his servants would keep spray bottles of it on hand for emergencies.
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What is the fastest rate a star could be flung out of our galaxy and by what mechanism(s)? (i.e. from a gravity kick by a hypothetical passing hypervelocity black hole)
Secondary question: how far away would it need and how long would it take for Earth to have no naked-eye visible stars in the night sky?
Alternatively, I am trying to build an alternate reality where some or all of human history was not influenced by the backdrop of the star field in the night sky, if leaving the galaxy is too unfeasible, I’ve considered applying these questions to a scenario where Sol is flung into a dark nebula—would that be better? (Thinking about the timescales, it would need to be shrouded from the rest of the stars long enough to cover a significant portion, if not the entirety of human history)
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There are a couple of ways to produce hypervelocity stars. A common one involves an interaction between a supermassive black hole and a binary system, leading to one star being ejected at speeds potentially exceeding 1000 km/s. I believe the current record is held by S5-HVS1, which appears to have been ejected from the Galactic center at a speed of $\sim1800$ km/s ([Koposov et al. 2019](https://arxiv.org/abs/1907.11725)). Assuming that the star doesn't slow down significantly, it could reach a distance of about 100,000 light-years (roughly corresponding to the edge of the Milky Way's disk) in about 17 million years. Not bad!
This isn't ideal for your scenario, though, since you want to remove the Sun from the galaxy, and we're about 25,000 light-years from our central supermassive black hole, Sgr A\*. It would take an extremely improbably sequence of events to send the Solar System to the Galactic center and have it undergo encounters with multiple bodies in order to be properly ejected. So we might want to look elsewhere.
Another scenario would be to have the Sun, when newly-born, be bound to a companion star which subsequently goes supernova. The explosion would cause the system to become unbound and send the Sun moving away at speeds akin to classic hypervelocity stars. US 708 ([Geier et al. 2015](https://ui.adsabs.harvard.edu/abs/2015Sci...347.1126G/abstract)) was likely ejected in this manner, and has achieved a speed of $\sim1200$ km/s. If the same thing was to happen to the Sun, it could travel the remaining 75,000-ish light-years to the edge of the disk in roughly 19 million years. As supernova progenitors typically live for no more than millions or a couple tens of millions of years, the whole process could happen very quickly compared to the lifespan of the Sun and the time it would take life to subsequently evolve on Earth.
Would planets survive the explosion - and, furthermore, remain bound to the Sun? Well, we've found [planets orbiting supernova remnants](https://en.wikipedia.org/wiki/Pulsar_planet), so it's quite possible for a system to have planets after a supernova has taken place. That said, it's unlikely that this alternate-history Solar System would look the same as ours; I'm worried about the outer giant planets in particular. It seems quite possible that planets in tighter orbits, like Earth, could be retained, though - particularly if they formed in the wake of the supernova.
Another possibility, as noted by Adrian Colomitchi, is to utilize interactions with another galaxy, such as [the future collision between the Milky Way and Andromeda](https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision). While most stars won't be ejected, some certainly will, accompanying the formation of features like tidal tails.
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If you assume that we've been kicked out of the Andromeda galaxy, that galaxy is still visible to the naked eye along with [a few others](https://en.m.wikipedia.org/wiki/List_of_galaxies)
If you want a night sky devoid of stars, your best bet would be to hid Sol in a dark nebula..
However, you'd still have planets to deal with.
Sol could be lighting up the nebulae gasses from the inside. So, you might need to deal with that too.
If you need the planets' lights blocked out too, you'd need to convince [Hactar](https://hitchhikers.fandom.com/wiki/Hactar) to surround Earth like he did with the planet Krikkit.
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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.
Imagine a universe full of water. A comfortable 22 degrees Celsius warm, density of about 998 grams per liter, and it fills up everything for as far as can be observed. There's nothing else; neither empty pockets nor denser planets. Just water.
This would be an extremely massive universe, but if I understand the physics correctly there would be no spontaneous black hole formation. The density and temperature would be totally uniform, and so would the gravity: every H2O molecule would be pulled in every direction at once, with the resultant force being zero. No movement in the water, no build-up of mass, so no black holes.
What if some people from a different dimension pay a visit though... They venture through the Phlebotinum portal, find themselves in their spacecraft-turned-submersible in this weird universe, and be adding their denser-than-water selves to the mix. Suddenly water is pulled slightly in their direction, increasing local pressure (and local density, and thus local mass) even further... cascade into a black hole begins!
Or would it? Water doesn't like being compressed, so there is a high amount of force required to make water locally denser. That means there's a hurdle to overcome before the gravitationally compressed water becomes sufficiently dense (compared to standard water) to have sufficient gravity of its own to continue compression, and eventually collapse into a black hole.
I think it may just hold up against the addition of a single spacecraft, which would have minute gravity of its own. But I cannot tell for sure.
Can you quantify what local density variation would still be allowable in a water-filled universe, without collapsing the lot into a black hole? Could, for example, this universe have an Earth-sized rocky planet in it? Or would the addition of one grain of sand be enough to begin a cascade?
Assume all of our known laws of physics apply, except this universe is not expanding or contracting. I am primarily interested in the short-term effects of a new mass added to the water universe, not whether this universe would suffer a big crunch eons into the future.
How this strange universe came to be is out of the scope of the question :-) (short version: simulated universe)
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Perturbations in a medium resulting in the formation of black holes have been studied extensively in the context of [primordial black holes](https://en.wikipedia.org/wiki/Primordial_black_hole), though to result from density perturbations in the early universe. There are plenty of analytical and numerical studies of the required amplitude of such perturbations $\delta\_c=\delta\rho/\rho$ (e.g. [Harada et al. 2016](https://arxiv.org/abs/1609.01588)). Unfortunately, these largely focus on perfect fluids (with equations of state of the form $p=w\rho c^2$, with $p$ pressure, $\rho$ density and $w$ dimensionless) and the radiation-dominated era of the universe. Water isn't a perfect fluid and this universe isn't radiation-dominated (!), so unfortunately we can't invoke those.
It's been argued ([Carr 1975](https://ui.adsabs.harvard.edu/abs/1975ApJ...201....1C/abstract)) that perturbations leading to the collapse of a region and the formation of a primordial black hole would need to be on the order of the [Jeans length](https://en.wikipedia.org/wiki/Jeans_instability#Jeans%27_length), a quantity more commonly used when studying the collapse of molecular clouds into stars. The Jeans length is
$$\lambda\_J=\left(\frac{15k\_BT}{4\pi Gm\rho}\right)^{1/2}$$
with $T$ and $\rho$ the temperature and density of the medium and $m$ the mass of its constituent particles - in this case, water molecules. Plugging your conditions into this yields a length of $\sim$1600 km - large by the standards of spacecraft but small by comparison to the typical lengths of molecular clouds and the early-universe perturbations that form primordial black holes.
(As a side note: There are two ways to think about the Jeans length based on two different derivations, which agree to within a factor of a few. One equates thermal and gravitational potential energy and says that beyond $\lambda\_J$, gravity wins over thermal pressure. The other calculates the collapse time and then derives the distance over which a wave could propagate across the region of interest and back within that time to stabilize the mass. I prefer the latter, you can think about the criterion with either interpretation.)
From this argument - which I believe is applicable to your scenario - this spacecraft would not cause a black hole to form; its length is much less than $\lambda\_J$. I would expect some black holes to form anyway due to natural random (possibly Gaussian-distributed) fluctuations in density, but this particular perturbation doesn't seem large enough to be problematic.
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# Your space ship is limited to an inch long, unless you increase the cosmological constant a tad.
[The critical density of the universe is 9.9E-30 g/mL](https://map.gsfc.nasa.gov/universe/uni_matter.html). The density of your liquid water universe is (before any subsequent cosmology occurs) 1 g/mL. That means that your rho/rhoc is about 1E+29. Put into [this StackExchange problem](https://physics.stackexchange.com/questions/560499/how-do-you-calculate-curvature-from-the-density) and that means k=1E+58 (H/c)^2, where I'm going to go out on a limb here and assume that question intends H to be the [Hubble constant](https://en.wikipedia.org/wiki/Hubble_constant), 1/(4.55E17 s). H/c is about 7E-27 m, so this tots up to 50,000 / m^2 . Now not having had any coursework in this physics (sorry, should have mentioned that before) I'm not entirely how to interpret inverse length squared as a curvature, but taking a wild guess, ... I should listen to Logan, whose keyword [Gaussian curvature](https://en.wikipedia.org/wiki/Gaussian_curvature) is most helpful. The radius of a sphere (actually a hypersphere here) should simply be the inverse square root of the 5/cm^2 above, or 0.45 cm. The circumference of a circular cross-section is 0.45 cm \* 2 \* pi = 2.8 cm = just over 1 inch. The space ship had better be smaller than that, or it is going to have trouble parking. *(Have you ever tried to convince an insurance adjuster you rear-ended yourself?)*
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We can work out the pressure on the space craft from the water.
*(I'm assuming a static universe that is not expending)*
Now for a small change in radius, $dr$, the resulting change in pressure, $dp$, (assuming its inside an incompressible material of density $\rho$) is
$$dp=\rho g(r)dr$$
Now $g(r)$ is the strength of the gravitational field at the radius $r$.
Now from the [shell theorem](https://en.wikipedia.org/wiki/Shell_theorem) the gravitation field, for an enclosed mass, $M\_{enc}$ is
$$ g(r)=\frac{GM\_{enc}}{r^2}=\frac{G(M\_{space ship}+M\_{water})}{r^2}$$
Now the approximate (accurate in the case of large $r$) mass of water is give by
$$M\_{water}=\rho \frac{4}{3}\pi r^3$$
So the pressure change is
$$ dp=\rho \frac{G(M\_{space ship}+\rho \frac{4}{3}\pi r^3)}{r^2}dr$$
which simplifies to
$$ dp=\rho \left(\frac{GM\_{space ship}}{r^2}+G\rho \frac{4}{3}\pi r\right)dr$$
from this we can see the problem as $r$ gets larger the increase in pressure grows. So for an infinitely large sphere of water the pressure would be infinite.
So I don't think your ship\universe would survive.
The collapse wouldn't happen before the ship arrived, as there would be no variances in the gravitational field.
hopefully that helps
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UFO's are real and fighting around the Earth!
I have an alien spacecraft in modern Earth's atmosphere, and rival alien spacecraft in Earth's Orbit. Both aliens are capable of maneuvering at great acceleration (100 G's?) equivalent to what is commonly portrayed for UFO's as seen in various videos in the atmosphere (and faster in space). They are aware if any kind of weapon is targeted at them with light speed, and are capable of accelerating any mass from subatomic particles up to a neutron star to near-light speeds in extremely short distances. Assume a spherical hull 100 feet in diameter with strength equivalent to battleship armor and near-infinite heat resistance.
The attackers in space are unwilling to cause massive collateral damage to the Earth (defined as any event causing the death of more than 1000 humans). With advanced notice, the defender aliens are willing to position themselves invisibly over urban centers to increase the odds of collateral damage.
**Given the limit of matter, but the choice of ANY matter from particle beams to neutronium slugs, and any velocity, can the aliens in orbit successfully target the aliens near the surface despite their early warning and great speed, or is the atmosphere too dense to allow projectile matter to enter fast enough without causing massive shockwaves or crust-damaging impacts from misses?**
The attacker entering the atmosphere more than superficially, or sending smart projectiles to pursue the near-surface craft, violate the limits of the question. They can carry or manufacture any exotic materials (like antimatter or exotic elements) on-board to use as projectiles or particle beams.
Bonus points if you can minimize the conflict being seen by humans and avoid any human casualties.
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Any form of particle beam energetic enough to damage armor will also excite the atoms in the atmosphere to plasma and therefore create a small and brief flash visible to half the planet.
Any solid projectile entering the atmosphere, even if it doesn't ablate away, create a small plasma trail by pushing the atmosphere out of the way, also visible to half the planet. Beyond that, even 1 gram of matter at 99% lightspeed delivers the equivalent of 131 kilotons of energy, which is guaranteed to cause collateral damage even if it hits the target.
To guarantee a hit on the target UFO, the attacker's beam/projectile needs to reach the UFO before it can move out of the way. 100 gees is 981 meters per second per second of acceleration, meaning that the UFO can move ~30 meters, vacating the 30 meter (100 feet) space it was previously occupying, in 0.25 seconds. Therefore, a lightspeed projectile needs to be fired from less than 0.25 light-seconds away from the target, which is 74,948 km. Earth's atmosphere is about 480 km in height, so the attacking UFO can indeed land a hit on the defending UFO without entering or even really approaching the boundaries of the Earth's atmosphere.
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1. Overload the passive sensors of the target to a level on which the launch of the projectile registers as noise. If you can, make the jamming come from multiple directions
2. Launch the projectile at a speed that [doesn't allow enough for the reaction time](https://worldbuilding.stackexchange.com/a/216427/26061)
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## Part #1: How to don't miss
What your projectile needs to no miss is to travel a certain mean speed $v$ so that the target cannot move fast enough to avoid the impact. This speed is given by our target maximun accelaration $A$, target's detection computing time $\gamma$, the distance to the target $d$ and the target's shape and size.
The target's shape and size determine the value of the distance $\Delta x$ that the vehicle must move to avoid be impacted by a incoming projectile in some certain part of it. To compute the $\Delta x$ of some part of some of some part of the target you must take some point inside the target and draw a line until nearest point that still is part or the target and is desired, the lenght of this line is equal to $\Delta x$.
Finally the required mean veolocity of the projectile is given by the equation
$$ v = \frac{d}{\sqrt{\frac{2\Delta x}{A}} + \gamma} $$
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## Part #2: How to no explode the world
For no produce a unreasonable big explosion we need to the Energy $E$ to be enough to penetrate the tank but less than the needed tomake a explosion able to make collateral damage the we will call $b$.
The Energy of the projectile on impact (assuming the only force that acts in it is gravity) is determined by $$ E = \frac{1}{2}mv^2 + mg\Delta h $$ So, for no explode the world the inequality $$ b \leq \frac{1}{2}mv^2 + mg\Delta h $$ must hold, there is a lot of variables to tweak to archive this, therefore this time no will be a simple equation and good luck with the algebra.
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## Part 3: How to avoid shock waves
Aerodynamics says that every particle that travels in a medium faster than the speed of sound of that medium will produce a shockwave, and in general it it travels fast it will produce increassly loudest sounds. So, at least the target is really big is likely that it projectile will be very loud.
Except if the projectile is small enough so it can travel in bewteen the atoms (I am no refering to collide/enter inside molecules) of the atmosfere, and therefore no produce shock waves or sound. (Note this probably requires to being computed a projectile path that avoid interactions).
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## Part #4 How to no leave a visible plasma
First of all follow part #3 instructions, because if some of your subatomic projectiles hits a molecule this will be very exited and will make some visible plasma. Secondly you also have to consider the relevant magnetic interactions that you projectile can experiment in their path. If you acomplish this steps (And I am no mistaken) your projectile should no be noted by anyone.
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As last note, depending of the case is possible that the energy required to hit/damage the target is bigger than the limit to no explode the world.
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# Radiation Poisoning
You fire highly penetrating radiation, like high energy neutrons or high-energy photons or neutrinos. This radiation will interact with the atmosphere, armor, computers and flesh of stuff along the beam-path very little, but because only a small portion of it interacts with anything it "hits", it doesn't care what is between it and the target.
You fire enough of that its interaction with the flesh of the targets causes lethal radiation poisoning. Biology is more fragile than atmospheric gasses and steel armor.
Your shots may even be able to penetrate the planet, so you will want to ensure there is nothing behind them besides the atmosphere and space, and/or have accurate GIS data and fire through the planet, killing mostly only the humans along the firing path.
# You will always hit
Your beam is going to move at basically light speed. The enemy being aware you fire isn't going to be able to dodge; they can, however, move so they aren't where they where when they last saw you.
Their knowledge of your position is going to be about 40 ms off (assuming they are on the far side of the Earth; lower if they are closer). At 100 G, they can vary their location to any spot in a sphere of radius $\frac{1}{2} (40 ms)^2 (1000 \frac{m}{s^2})$, or 80 cm. Dodging is not practical.
# Or just Cook them
While you'll deposit some energy in the atmosphere and in the armor, the amount you need to kill a biological creature is so low it won't make much difference.
It is harder if your goal is to instantly kill the target. Suppose we want to deposit enough energy that it cooks them -- increases their temperature by 100 C (to boiling), and that the energy is deposited in proportion to the mass of what the beam goes through.
A cone that is 12,000 km long and 100 m wide (the size of the enemy flying saucer) has a volume of 3.14 \* 10^10 m^2. If the density is on average 5 times higher than water (we are firing through the planet), that is 6 \* 10^17 J of energy in the beam, or 10^5 KT of TNT.
However that energy is deposited uniformly over the entire length of the cone. As the amount of energy isn't a world-destroying explosion, you won't even have a noticable Earthquake.
The only remaining problem is the waste product of the beam. Highly penetrating radiation (of whatever kind) doesn't cleanly make heat; when the radiation interacts with the matter, it won't produce thermal energy, but instead end up emitting more radiation of whatever kind. If it is high energy photons, deflected almost as high energy photons will spread out from the beam path. Other beam particles will generate other "debris". Due to conservation of momentum, they will still mostly stay within the beam path.
If the Earth is a backdrop, the real danger is on the far side of the planet (when your beam is wider and has generated more near-light-speed "debris" by interacting with the planet). Tuning the beam to cook the target but not penetrate the planet may be possible.
The defending target may do the equivalent of gluing humans to their ship. Fly *inside* skyscrapers, and keep 1000 humans in the firing line between them and the enemy, and arrange is so when you crash you also knock down a building.
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## The ship is a sitting duck.
Neither the aliens nor any missile/construct can enter "the atmosphere". The alien courts have decreed this to begin at precisely 100 km (Karman line) based on Earth precedents. The ship is essentially on the ground, 100 km from the attacker. 1E5 m / (3E8 m/s) = 3E-4 s = 0.3 milliseconds of warning. Accelerating at 100 \* 10 m/s^2 = 1E3 m/s^2 for that time, that gives an average velocity of 0.15 m/s for 0.3 ms, which gets the ship ... less than a millimeter. Ouch. If it could get to the speed of light instantly it would be up to 100 km away, but it's just not that fast.
## Cook it with X-rays
Hard to see, highly penetrating, without cosmic ray style light shows all over the night sky. The lethally irradiated aliens will hopefully slink off to someplace civilized and discreet to die.
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## You're Looking for Missiles
The traditional way to kill a fast moving aircraft is to hit it with a faster moving missile. I think you're attempting to rule that out with the "no smart projectiles" restraint, but honestly how can you call them "Advanced" weapons if you exclude concepts that those dumb humans have already built?
## Switching to Guns!
If you really are sticking to the no missiles rule, then the most important issue becomes your firing angle.
If you fire straight down, any misses are going to hit whatever is below your target, which could include a city if the enemy positions themselves properly. So you're going to want to pick a different angle to avoid collateral damage.
But the Earth is roughly spherical, and the enemy ships are hovering in mid-air. You can position your ships such that any misses fly off into space.
Don't do this:
```
* (ship)
| (bullet)
* (ship)
_
/ \ (Earth)
\ _ /
```
Do this!
```
* --- *
_
/ \
\ _ /
```
Now your misses fly off harmlessly into the void, to kill something far away a long time from now. Probably not a human!
## Minimum Mass, Maximum Speed
Shoot Lasers. They're technically particles, which means they have mass. They can also reach your targets without spontaneously fusing, which most other forms of matter would when moving through the atmosphere at significant fractions of light speed.
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## Weaponize converging wave forms.
Whenever two waveforms overlap you get either [constructive or destructive interference](https://en.wikipedia.org/wiki/Wave_interference)e based on how the waves line up. What you are looking for is a wave based weapon (like a laser) that packs too little energy to be harmful... and then you want to get a few million of those little guys, point them all at the same spot, and synchronize their wave patterns. Anywhere in front of or behind where all these beams converge will be relatively harmless places to stand, but that tiny place right where they all come together could very quickly become several million degrees.
Since the ship you are targeting is pretty much temperature proof, this will not melt its way through the enemy ship, but what it will do is create a thermal explosion like a tiny nuke that will send a very powerful shockwave through the ship ripping it apart.
Because the beams move at the speed of light, the enemy ship does not have time to dodge. Also, if you miss, the weapon will still create a detonation at the prescribed altitude creating a ball of plasma that will be opaque to the lasers... so there is virtually no chance of the weapon actually reaching the surface.
**How is this a mass based weapons?**
The beams do not have mass, but they are not the weapon, just the ignition system. The actual weapon is the burst of plasma made up of Earth's own atmosphere where the lasers all converge... basically think of it like a depth charge, but with a much less dense medium and a much more energetic explosion.
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Many others have suggested designing a weapon fast enough to hit them before they can move out of the way. That's a very hard task, and leaves you with a projectile that's moving fast enough that misses are very dangerous.
Instead, go with a slower weapon using a projectile that will burn up before it gets to the surface. The enemy ship will be able to dodge it easily, but that's fine because you're not actually aiming at them. You're simultaneously launching *thousands* of them, creating a ring of fire centered on their current location. If the enemy ship can travel X meters between firing the projectile and impact, than your ring of fire should have a radius about 20% larger than X. Now, maintain your wall of fire, squeezing that ring tighter and tighter over several seconds until the radius is zero.
The falling projectiles will essentially form a cone shape. The enemy ship can't flee without flying into the projectiles raining down around them. As long as you ensure the space between two adjacent projectiles is smaller than the width of the target, they'll have no way to avoid being hit.
A few humans *might* see the rain of projectiles falling from the sky. If they burn up before getting close to the surface, however, those humans won't think too much of it. Micro-meteorites and other bits of space debris enter the atmosphere and burn up all the time. People really only pay attention to them when they make it to the surface or violently explode and damage something.
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**Neutron beam bank shot.**
/They are aware if any kind of weapon is targeted at them with light speed/
This does not mean they are aware of all incoming projectiles, only being targeted. Your attacker will fire in the opposite direction. It will send a beam of neutrons at a high fraction of c, banking it around the moon in a tight curve such that it comes back on a path to hit the defender in the atmosphere. The neutrons will be largely unabated when they hit the defender. The neutrons will pass through the targeted ship disrupting electronics and biological systems. They will eventually hit the earth.
The beam will produce the same effect as a neutron bomb. Living things in the path of the neutrons both in the target ship and on the ground will die within a few days from acute radiation toxicity. The beam of neutrons spreads en route and is wide enough to encompass the entire targeted ship. It will be slightly wider when it hits the surface. Odds are good it will hit the ocean. Odds are low it will hit a human.
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This is something my sister and I have argued about a lot and we can't figure it out ourselves. So help me out here.
In a world where both four-legged (dragons and griffins) and two-legged (humans and anthropomorphic animals) beings live, do you think it is possible to make an amusement park that would work for all of them?
I mean like the sitting place and safety in coasters, or what type of amusement are possible to all types of species?
I have my doubt becauses of the different sizes of all beings, but please tell me if I am wrong if you can figure this siblings' debate out.
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Human amusement parks have already different attractions for different sized humans.
In many cases a minimum height is required to access an attraction, and in some cases even a maximum height, in order to ensure safety of the visitor.
[](https://i.stack.imgur.com/MqPEe.jpg)
The same concern will apply in your case: a seat designed to hold a human won't work for a rabbit or a cow sized creature.
It's very likely size separation will be enforced. To make it economically viable they might use compartments, like wagons 1 to 3 for dog sized quadrupeds, wagons 4 to 9 for human sized bipeds, wagons 10 to 15 for cow sized quadrupeds.
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Almost everything would have to be an enclosed ride with a back strap that held them in place i'd think unless they want to lay on the ridge of their spine.
Other than that alot of water rides :P
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**The glider coaster**
Make a roller coaster that has a 20 foot long carriage (for Humans) or a 40 foot long carriage (for Dragons) with a 20 or 40 foot foot pole (20 for human 40 for Dragons) coming off the front and back it and an attachment point for a 10 foot elastic that attaches harness to user. These elastics will be designed to ensue that the user is constrained to never hit the coaster under and circumstances. This is done by having the elastics essentially confine the user to a flight envelope in-between the front and back coasters. The roller coaster design will be constrained by a lack of overhead and sideways clearance, but otherwise most mid-G coaster designs will work.
**How it works**
Griffins and Dragons spread their wings like they are about to fly and use the speed of roller coaster to fly at full speed while effectively gliding (unpowered by their own wings). Humans can do the same with artificial wings attached to their arms designed to constrain movements that would accidentally put snapping staring on their bones (high drag maneuver that places stress on collar bone). The coaster would also effectively guide dragons into doing complex and typically difficult maneuvers that only expert fliers could perform, but to perform them they would simply keep their wings flat and let the coaster guide them.
**The circle glide coaster (for beginners)**
A simple glider coaster would be a simple circle that would let a dragon or human do as many orbits as they want without any external forces. The humans would get to experience personal controlled flight, and dragons get to fly without having to manually propel themselves. This could also be used for sports as it would give dragons and humans an even playing field for demonstrating interesting flight maneuvers. a large enough glide coaster could even have multiple coasters going at the same time and introduce new ones in the same way cars enter a round about.
**Advanced coasters**
These might have loops, cobras, and other maneuvers to show case different maneuvers. However, these will have to be tested so that they are safe weather you go full drag, minimum drag, roll, or move around to anywhere in the flight envelope.
**Safety and popularity**
Glide coasters like these would be a huge attraction to dragons and humans alike, but there would be a good reason for that. Even basic versions of this would be very rare since it is definitely more high thrill and high risk. You would need to ensure that no dragon has a lift or drag capability that exceeds the limits of the coaster, and the activity would have more in common with sky diving than a spinning tea cup. That said, a place like Coney island may be able to justify it as a high thrill ride or spectator sport for the non-rider onlookers.
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**There are a two main considerations to take into account**
1. volume of visitor
2. wings or lack of wings of visitor
When you think of rides that dragons can't ride you of course think of roller coasters, but stuff that is designed for human butts isn't going to work on dragons
Volume disqualifies small chair rides, like roller coasters, tea cups, any thing tracked that only has smaller size carriages.
Wings can be accounted for if the riders keep their wings in the dart or have them bound so they don't accidentally create drag, but you would want a ride that doesn't have these pitfalls and work with everyone.
I present the [Graviton](https://en.wikipedia.org/wiki/Gravitron). The gravitron is a spinning chamber that produces moderate G forces with centripetal force. The key thing is that volume and wings have little effect and people can be placed anywhere in the ride interchangeably. You will want to build the ride a little stronger than normal since more G acceleration on a larger mass like a Dragon or Griffin will apply more force to the walls.
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# Dragon's Breath (Frame Challenge)
I would suggest that the biggest hurdle to your amusement park is not the size or number of legs of your guests. It is dragon's breath.
Traditionally, dragons breath fire. Other versions spit acid or shoot lightning. In some universes they can do more than one or it can vary by dragon.
Why is this an issue? Because in many modern amusement parks, the rides are thrill rides. Rides designed to make the guest feel fear and exhilaration. To make you scream and to make your heart race.
The problem is, when a dragon gives into their primal fear and roars, it tends to come out badly for whatever is in front of their mouth. Be it another guest, or the car or other element of the ride.
Your dragon thrill rides need to be able to take into account what kind of breath a thrilled dragon might uncontrollably emit. Protect the other guests. Have struts that can survive both steel melting flames and stone melting acid. An enclosed cart might do it, but will reduce the effectiveness of the ride and might also put the individual dragon at risk from splash back. Even then, the cars would be heavy and expensive, and might not be viable as a ride vehicle.
Unless you are allowing for magic, I think a dragon amusement park ride is going to be a non-starter.
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I remember reading in another question about Time Travel here on the forum, with the subject of your being stuck in medieval time.
That if you where lucky, you could have a good life serving your local noble/lord, as an accountant and maybe as a writer, and with your modern day high school math would be able to elevate his status in the king´s courts.
How exactly would such a thing as you knowing modern day math and being able to read and write, do anything for the nobleman's status in the king´s court?
Surely even if the nobleman wasn´t the brightest, he would still have people hired to do something so basic as laying down a budget? Or have I misunderstood something about medieval society worked?
If so, I would be grateful, if someone could explain or point out a post where this explained?
Because as said I have a hard time seeing how modern day high school math and maybe being bright enough to learn how to read and write in medieval language, would in anyway shape or form help the nobleman in any way shape or form that would help his rise in status in the kings court.
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[From Wikipedia, on accounting:](https://en.wikipedia.org/wiki/Accounting)
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> Double-entry bookkeeping was pioneered in the Jewish community of the early-medieval Middle East and was further refined in medieval Europe. With the development of joint-stock companies, accounting split into financial accounting and management accounting.
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> The first published work on a double-entry bookkeeping system was the Summa de arithmetica, published in Italy in 1494 by Luca Pacioli (the "Father of Accounting").
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[And about Descartes:](https://en.wikipedia.org/wiki/Ren%C3%A9_Descartes)
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> One of Descartes's most enduring legacies was his development of Cartesian or analytic geometry, which uses algebra to describe geometry. Descartes "invented the convention of representing unknowns in equations by x, y, and z, and knowns by a, b, and c". He also "pioneered the standard notation" that uses superscripts to show the powers or exponents; for example, the 2 used in x2 to indicate x squared.
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We often take these things for granted.
I have been in the position of someone transported to a place where people don't know basic math often enough that I can sympathize with any time travelers going to the middle ages. In my case, it was more like being an IT pro with more than one boss who got their position through the Dilbert principle. Seriously. I once made a piece of software that would keep some people from using some company accounts if they went overbudget for the month. I had to explain this to my boss multiple times, and he still wouldn't have it.
"How come we are over budget if there is still money in the account?"
"Well, there are some expenses that the company has to pay for in a few days. You use that money now, you won't be able to pay everyone's salaries and the electricity bill"
"I still don't get it, this system sucks! Turn it off!"
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There's this book I really love, called "The Richest Man of Babylon". It tells the story of a filthy rich merchant in ancient Babylon who is tasked by the king with teaching basic math to his subjects so that the realm can generate more wealth. In one of the lessons, rich guy tells everyone that they must have a budget. A young guy gets mad at the notion that he must be a slave to a table and ragequits the class. He ends up poor while most others end up rich.
You've seen it too. Every one has at least one friend or relative who sucks at budgets, and is always either wasting money on superfluous things or getting into debt without actually having to. In order to stop sucking at budgets, the very least you have to do is a table with incomes and expenses, which is a rudimentary way of bookkeeping. People who suck at math or can't read and write will have a very hard time at this. In the middle ages most people would fit into one group or the other, sometimes both.
So if you are able to make good choices with money, you could keep your overlord from going bankrupt. If you're really smart and clever, or if you graduated in a STEM course you can probably come up with a system of your own that will improve the local economy a little bit. But if you are an actual accountant? You might be interested in reading about the Medici family in Italy. They opened a bank that lasted from 1397 to 1494 and made them the wealthiest family in the western world until incompetence caused the bank to be liquidated. You could probably replicate the feat in earlier dates, and even make it more durable since you'd have further financial and historical knowledge.
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**Money supply**. The medieval noblemen probably have little idea of the concept. If your accountant can educate his nobleman in the art of lending money he doesn't have as paper promises to pay in exchange for future goods, waiting for the ensuing inflation to increase the price of gold and grain before selling his reserves, and then calling in his paper debts ... well, the peasants may not live to see the 20th century, and the accountant's descendants can take their place.
**Lending options**. The noblemen probably only have a few ways they lend out money, and those are likely subject to the quaint tradition of usury laws. The accountant can instruct the noblemen in the art of extracting a *fee* - not *usury*, mind you - to issue a workman's payday wages *early*, just this once - well, the sky is the limit. He could find himself moving to a royal court if he's not careful.
**Credit rating**. Peasants have a credit rating - stinking, ignorant, base-born nobodies ... wait, no, there's a better way to do it! When the nobleman sends his henchmen around to "tax" the peasants for all their accessible cash, they can explain that prompt, courteous compliance (plus sufficient cash) will get the peasants a Good Mark that will follow them and their descendants until the mountains crumble into the sea. The same for other financial arrangements of benefit to their Lord. If their dear mother takes ill after the tax collectors have taken all the money, how will they buy medicine if they don't have a good Credit Rating? Before long the peasants will be diligently turning up for occasional high-priced payday loans to try to show their noble lord that they are Good People and should be rated as such. Taking time to sneer at their weaker-fortuned fellows on the way out.
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If this is a time traveler to earth's medieval past there is a problem. Modern finance is not relevant to banking at that time.
The problem was that the Catholic Church forbid charging interest. This killed banking as we know it today.
What was done which was allowed and was done in part to get around this were Bills of Exchange. With these, one could pay in one country in one currency for a payout in another country and currency at another time. You could borrow by getting the payout now and pay back later. It was also a way to transfer money between cities.
Traveling merchants and merchants buying inventory from other cities used these. They could have a financial family pay for the purchase of inventory in another city. The goods were transferred to the retailer who would pay on the Bill of Exchange from the sale of the items.
Although you could not charge "interest" you could charge for foreign currency exchange. Banks do this by baking there fee into the ratio of the currencies that they exchange. You will notice the ratio of currencies a bank lists is different depending on which one you are exchanging for the other.
So this became the only banking going on in Catholic Europe. So a modern accountant would face this problem. Their skills would not match and they would have to learn how finance works here.
Maybe the account could try setting up commodity futures trading. This is a modern notion which could be seen as a way to stabilize prices so might not get disagreement with the Church.
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It would have absolutely no effect.
The problem with time travel that is so often missed is 'memory'.
A time traveler could not 'remember' any data that was obtained in the future, because of the light cone. Causation would have to come after the effect.
So even if an accountant today could travel back in time, his memory would not follow him. He would not be able to remember any modern-day information, as the cause of it would not yet have occurred. The only thing he could 'know' or 'remember' was the information available in the time period he was in.
In point of fact, it is doubtful if he could even know or remember that he was a time traveler.
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
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I'm determining some of the biochemistry for some artificial organisms created for various commercial tasks, from industrial to military use. I'm trying to figure out if augmenting the energy molecules could make the metabolism any more efficient. The main reason why I'm focusing on modifying ATP into Ap4 (adenosine tetra-phosphate) or even adenosine penta-phosphate (which I will call Ap5 for ease) is because the biochemistry of these organisms is going to be relatively similar to that of known life, so molecules such as phosphoenolpyruvic acid (PEP) *may* have other functions like signaling or producing ATP itself that using them in the same way that ATP is used could interfere with, though I could be wrong on that.
I'm thinking that the compounds with "extra" phosphates will help in times of high energy need, such as during exertion or stress. Most of the time, when the creatures are at rest or not under exertion, they would primarily use ATP for energy. But because some of the created organisms have extra dense muscle or complex structures such as internal computers that require extra energy to use, I figured that adding extra phosphates could prolong the time that the Ap4 or Ap5 can be used, as instead of going from ATP → ADP + phosphate, or ATP→AMP + PPi, there could be longer reactions such as Ap4→ ATP + phosphate that can energize more locations, or even larger bursts of energy at once coming from Ap4→ AMP + PPPi, which could provide greater amounts of power to more demanding structures.
Ap4 and Ap5 occur in nature already, as [it has been observed to be synthesized by yeast Acetyl CoA](https://jb.asm.org/content/176/10/2986.long). Ap4 has also been found in rabbit eyes and rat aortas.
My main concern is that this is not actually that effective. Dephosphorization of ATP to ADP and ATP to AMP yield about -31kJ/mol and -38kJ/mol in Gibbs free energy respectively, and dephosphorylating ADP leads to about -31kJ/mol as well. But would it be as energetically valuable or even worth it to attached on an additional one or two phosphates? I'm not a chemist (obviously), so I don't want to just go right out and say that for example, dephosphorylating Ap4 into ATP leads to -31Kj/mol, Ap4 into ADP leads to -38kJ/mol, and Ap4 into AMP leads to -45kJ/mol (my unscientific assumption that each additional phosphate bond adds 7kJ/mol afterwards, though this could probably be a lower amount.)
I think that the conditions for **equilibrium** would be the major factor, as in theory, the extra phosphates will make the molecule less stable and easier to accidentally hydrolyze. Perhaps with exertion, the cellular chemical equilibrium can shift, allowing for these extra phosphates to come into play?
My first thought was that raising the pH of the cells that need energy to around 7.1-7.4 as exertion progressively increases, as mammalian skeletal muscle cells tend to have lower pH values around 6.8-7.1, and human muscle cells at rest have been [recorded at 5.99](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC297096/). The reason why I hypothesize raising the pH could make Ap4 or even Ap5 more stable is because Ap4 has been known to occur in the [aqueous humor in the eyes of rabbits](https://jpet.aspetjournals.org/content/308/2/468). At least in humans, the pH of the aqueous humor is around 7.1-7.4.
Not sure how well this could hypothetically work, or if it even makes sense. Raising the pH of various cells would definitely require some overhauls of other parts of the cell such as in enzymes or signaling molecules, particularly in muscle cells, which for my purposes is totally fine because these critters need to be built (almost) from the ground up and use artificial directed evolution in addition to computer simulation to make "blueprints."
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You are correct that ATP is not particularly energy dense. For its primary use, that is good thing.
### Lowest common denominator
Its the rough equivalent of a one dollar cash. Usable for all your day to day financial transactions.
As much as you don't want to use gold bars or stock certificates for day to day transactions. Cells don't use long chain fatty acids and carbohydrates directly to pay the energy cost of processes.
Its like you are asking if we use hundred dollar bills instead of one dollar bills, can you make bigger purchases? Currently cell processes just use more one dollar bills/ATP as needed. If you increase the minimum bill size the increase the minimum energy cost. An efficiency penalty.
### Bodies will overheat before energy limits hit
You seem to be concerned about high energy demand systems. It is my understanding that thermal dissipation will be concern long before lack of ATP for said process becomes an issue. Cells (as a large group) can use enough energy to cook other cells(ie fever), The cash(ATP) in circulation, is not the limiting factor for cell processes.
### Not impossible, but inefficient, and not the limiting factor
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This may be not the answer you are looking for but I will approach the problem from a worldbuilding perspective, as I'm too rusty and there are chemistry and biology SE's. Plus, there is a big hole in your plot which I would like to address.
## You may be heading in the wrong direction
When we talk about high metabolic rates, the first thing which comes to mind is birds. Google for "bird metabolic rates", and sure enough there are different studies that investigate different aspects of avian metabolism, including the factors which affect it to be higher, among others.
On top of my search results, I see [Avian Energy Balance & Thermoregulation](http://people.eku.edu/ritchisong/birdmetabolism.html), which is simple enough and can be useful for the case. Let it be our source of data.
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> Birds have high basal metabolic rates & so use energy at high rates. Among birds, songbirds (passerines) tend to have higher basal metabolic rates than nonpasserines. And, of course, the smallest birds, hummingbirds, have the highest basal metabolic rates of all birds. In general, basal metabolic rate (or BMR) is related to mass, with larger birds expending less energy per unit weight than smaller birds.
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[](https://i.stack.imgur.com/baC3s.png) [](https://i.stack.imgur.com/77adA.png)
As you can see, small birds have 10-30 times faster metabolic rates than humans. So if you dive deeper into the topic of what makes them be so energetic, you can draw scientifically accurate reasons for your artificial soldiers or creatures.
## Some Fundamentals
To be more specific to your question, you are missing some vital parts which have a greater impact.
Let's look at [Krebs cycle](https://en.wikipedia.org/wiki/Citric_acid_cycle)
[](https://i.stack.imgur.com/dPzAd.png)
The details are not important for us, but the overall picture is relevant. Observe that there are 10-11 reactions at least - and each of those can be a bottleneck. So your most significant mistake is to consider that ATP part is the only source of the bottleneck, and if one looks at it from the perspective of excursion power, it may look true but it's more like burst power at best. More important is how fast AMP is restored to ATP and that is defined by Krebs and(or) others.
As we saw on Hummingbird, the difference it can make is over the order of magnitude of continuous power. And if there is need for more burst power, changes in concentrations of ATP can have more impact than Ap4 or Ap5, which may or may not bring +20% of something, when a simple 2 times increase of concentration brings you +100%.
Reactions of metabolic cycles have low potential barriers (not sure how it is called in English, energy to initiate the reaction is low, relatively) and for this reason, small changes in temperatures have a good impact on the intensity of the reaction - but it has to be understood that it is a function of many factors, and there is a limit to how far we can ride the vehicle.
## Difference between Artificial and Natural
Are birds fundamentally different from others since they have metabolic rates higher by an order of magnitude? Unless there is data indicating otherwise, we probably have to stick to no, because of evolution and all that.
With naturally evolved species we have to understand that metabolic rate is not the goal, survival is. Therefore, those rates are a tool and are a function of means, environment, and seasonal changes in which the birds have to survive. And burning at max is not necessarily beneficial to survival.
So naturally evolving species have to compromise. Even a 0.01% improvement that shines in some specific situation that doesn't necessarily occur all the time, can be beneficial over generations and population numbers.
Hence the food sources, nutrition values, scaling down the concentrations of enzymes that work in metabolic cycles, etc.
Synthetic life does not have most of those restrictions, so its goal is defined by those who create them and it probably isn't survival in a natural environment. So we can create a big body (at least by mass) species with the metabolic rate of a hummingbird, say as big as an elephant for example. From the perspective of natural survival, it would be insane just by size and accessibility and the extent of the area/territory which is needed to feed such a creature. But for us, it is a lesser problem as we can probably attach some energy converter and supply that creature with the energy it needs.
For our 5000kg elephant hummingbird it will be 390kw per organism. Quite a lot actually, it can be directly compared with some lower-tech versions of combustion engines. Inefficiencies aside, injecting the energy to our elephant as waste heat from that process can be kept external, but still, we hit some physical limitations which synthetic organisms are subject to, which we have to solve through the design of such an organism - but in the shape of an elephant, it will be quite hard to dissipate 390kw. This again depends on the technology available - we still can solve that by an external embedded cooling system, but again such things will obviously be subject to physics.
* Just a side note about how much 390kw is in nature. 1 tonne of dry grass/straw contains about 3900kwh of energy. Coincidentally, that number is quite close to what we need. So our elephant hummingbird needs to digest at least 100kg of dry grass per hour and about 2.4 tons of it per day. Again, coincidentally that amount of grass grows on 100x100m area (yields are 1-3t per hectare). *Dino descendant is that u?*
By itself, it looks doable, but they have to procreate, and that occupies some common area, causes competition, etc. Again possible, I guess in dino days things were good enough to allow that, but we all know what happened - the environment was shaken and they didn't make it.
As grass is not necessarily the best food source there is - efficiency-wise and factoring in speed of digestion - actual numbers including those factors will bring a few times higher consumption rates and therefore area necessary. Since grass grows for 3-4 months, a season - the total area needed to feed one organism will be a few square km per creature.
* Energy dissipation depends on the surface area, so a flat body plan can dissipate 390kw better - idk probably a centipede?
* Connected google overlord just to check and they have answered:
**How much do elephants eat and drink per day?**
*Adult elephants can eat between 200-600 pounds of food a day. As herbivores, elephants consume grasses, tree foliage, bark, twigs, and other vegetation daily. Elephants can also drink up to 50 gallons of water a day about as much as a standard bathtub holds.*
Hence, I have to conclude that I didn't shoot high enough with our elephant hummingbird, they still do not put nature to shame.
## Summing Up
In general, limits of what's already available in nature are higher than what we observe typically, and those limits encompass low and high extremes. Biological systems use the building blocks available to adjust themselves to the conditions they survive in.
Synthetics are freer from evolutionary restrictions, so we can have performances higher than anything that is typical in nature, combining the best from all different species. For example, humans do not have the best muscle tissues, there are creatures that have more robust muscles as tensile strength goes (and that can mean more strength in a smaller package). However, a trained human is a top predator because they can exhaust any creature (land ones I guess, so again it mammal vs mammal) by not stopping in pursuit of them over days. Sure, it's more from our hunter-gatherer times, not many tribes of today can do that(my guess), but there are some which can still do that(seen about them).
So the whole biological system/library is our lego blocks, we are more restricted by our knowledge and how much we have read in that library. There is still a long way to go, but in the future, we can imagine it not being as big of a limitation as it is today. Hopefully, we won't burn it down like The Great Library of Alexandria before we do read it, lol.
But also, physics trumps all the systems, including biological ones, so do not forget physics is king.
## Things I forgot.
With metabolic festivities, I totally forgot about the respiration problem, and more like blood capacities specifically. But respiration limitations is probably out of the scope of the question, but they also have some science behind it and works studies on that subject, and after all it still connected to ATP. It's more archeological as of today's, biological differences environments in previous eras. So it may have the sense to dig in that direction, however, it may be less applicable to synths as we may address this and other problems in ways not accessible to biological systems, which I forgot to mention as well, did I? hm, I forgot ...
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Here's something I've been pretty curious about for a while. So a common trope with immortal characters, most commonly vampires, is that they have to periodically move to a new town in order to keep people from noticing the fact that they haven't gotten any older in all the time they've known them.
Vampires are *also* typically depicted as frozen at the age they were turned at. This can make the above problem *especially* frustrating for, say, vampires who were turned as children, who are expected to change radically in appearance over just a year or two, and thus would have to move all the time, barely able to stay more than a year or two in the same place.
...But what about the opposite? Which age is it *ideal* to be turned at in this regard, where you aren't expected to change much at all in appearance over the years, to the point that it takes *ages* before anyone notices how weird it is that you don't look any older than you did the day they met you?
**If your goal is *solely* to be able to live in one place for as long as possible without anyone getting suspicious of the fact that you haven't visibly gotten older, what age would it be most ideal to be frozen at?**
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## Queen Elizabeth, hello?
I think she's just the perfect example ( besides being queen, if you want to hide something probably not the best ).
Why she's the perfect example? Well, do you even know how old is she? Do you remember the last time you saw anything change in her appearence? Well, she's 94 years old according to wikipedia and I bet that at least 10, 15 years earlier she wasn't **THAT** different.
**So what age would be the best to freeze?**
Well, let's think first, if we choose to be frozen too early:
* **20's:** I'm currently at 25 and I'm pretty anyone could see my changes from 20 y.o. to 25 nowadays and I'm also pretty sure that from 25 to 30 I will also change a lot, so I would consider this to be too suspicious to choose.
* **30's:** Now it starts getting interesting, there's a few people, mainly rich ones and healthy ones that really doesn't change that much, from let's say 30 to 40, some people stay the same if they don't gain or lose weight, at maximum some white hair. But this won't last long since entering the 40's can be tricky without changing.
* **40's:** Well, where I live there's something we call *The 40's crysis*. Which mainly concerns getting old and changing a lot ( most of the times negatively, that's why there's a crysis ), you start feeling older now, I think, therefore, also not a great time to freeze.
* **50's:** Now it's getting better, but also I think some people still change a lot at 50's, besides the really rich ones but I don't think people can hide the aging proccess here.
* **60's plus+:** This is where you would like to freeze. **Maximum discretion.** At 60's you are already old, people can see you're old and they start specting you to die or to stay alive while you can, but the changes aren't **that visible** anymore. White hair is common, you start gaining benefits from society, more respect from younger people (at most cases), therefore, I think that people would only think: *"Yeah he's old, must be healthy to be alive for so long."* After 10 years ... They would say: *"Wow, how old is he now? He must be healthy and like to live a lot to be alive still, he still looks the same, I wish I be like that when I grow older ..."* and so on ...
**TL;DR:** Freeze on 60+ years old to be unoticed for longer time. I think from 60 to 90 you are good to go without being noticed.
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For humans, there is really no age at which one ages the least.
Life in the real world, and presumably in your fictional world as well, is a progression with small changes occurring constantly. Not only the forces of normal development, but various emotional stressors, physical illnesses, spiritual transformations, events that occur within an individual's family as well as in a person's broader community: all of these things push and prod at the little levers that age one.
At best, one could possibly say that any given two or three year stretch is about the longest timespan wherein one doesn't appear to have changed very much. Take a picture of yourself today, then find a picture from this time last year, and also get one from this time next year and chances are good you'll appear fairly similar. But compare a picture from two or three years ago to one two or three years from now...I think the differences will be much more startling.
The problem for your scenario is that no matter what age you're frozen at, the people around you will be onto it as they age and you don't. People your age will grow old and die and will wonder why you haven't. People younger than you will have associated you with people of their parent's generation, and as their parents age & die, while you don't, they too will wonder why. And then as they grow old and die...
You see what I'm getting at.
I think your best bets will be to either *play it up*, like Gandalf or Saruman, and simply be ageless in the midst of ordinary society. They'll get used to it. Or, alternatively, *go on the road*, and take up the life of a permanent wanderer. Call no place home for more than three to five years, then move on. Depending on the time period, you may not have to move far! Or you may have to move to an entirely different planet.
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### From mid 20s, growth is shown more through behaviour rather than biology.
In your mid-20s:
* You have no more "expected growth". Puberty is done. Youre at your full height.
* You have no evidence of ageing - no wrinkles, no grey hairs. Back and knees still work.
* Growth starting in this period is mostly societal rather than biological, and you can fake getting older by changing your behavior - people finish college and get a real job, turn from a batchelor into a father, stop partying and become a mother. They get a mortgage and a more practical car.
You could last 25 years without standing out around your non immortal peers by copying their behavior, and when they're turning 40: - "you exercise and mostly avoid junk foods and dont smoke and arent staying up to 3am with a sick child" that's why your not getting wrinkles or grey hairs.
When they're getting into late 50s theyll start to get suspicious, you should move on by then, or go just "move to warmer climate" only to have your "child" return a year later and "move into their parents place". You then make friends with a new batch of mid 20s and continue the cycle again.
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I would say the teens and mid twenties.
There's little to no difference between a 16 yo and a 26 yo looks wise.
A simple hairstyle can make a 16 look way older or a 26 way younger.
Also consider beards, teens can grow beards and adults can cut them.
Also height... There's people who stop growing at the age of 12....there are twelve year olds way above the average height of an adult.
With enough makeup and some hair styles you could pass for any age you want.
Usually rounder hair that goes around your head makes you younger, hair that goes sideways or upward makes you look more mature not older but more mature.
And long hair makes you look older, that's why a lot of moms cut their hair short in an attempt to get back their lost youth.
Also muscle mass plays an important role, there are strongmen and powerlifters of age 14 to 18 that lool like 50 year olds grown men.
So my best bet would be 20 years old, experienced it first hand too with people thinking I look like a 14 yo boy when I cut my beard and 28 or 30 when I go bald and let my beard grow long.
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There is not a single age which can be valid for every individuals, since each person shows the sign of ageing in a whole different way, according to their DNA and their lifestyle.
When I was 16 I used to play basketball in a nearby town, and used to hitch a ride from another teammate who had the driving license when going to the trainings. One day he asked me why at my age I didn't have a driving license myself, and when I asked him how old did he thought I was, he said I looked 25. And the other day, watching myself in a video taken about 13 years ago, I have seen that I am not changed that much.
On the other hand I have seen a classmate from high school, who in those years looked like Britney Spears in her golden times, looking like a 50 years old at the tender age of 35. And I could name a lot of celebrities who seem to have some sort of secret pact for looking way younger than their real age.
If your vampire is wealthy and can appear to have a healthy lifestyle not many people will question its apparent lack of ageing, within limits.
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This question assumes that aging is a linear process, which it isn't.
Growing from infancy to puberty is as much aging as growing old and frail and dying. They're just two different forms of progression of the human body in different life stages.
That said, it seems your question is more focused on the degradative changes of aging, those in which the body is in decline, rather than the constructive changes of aging, where the body is growing into its final form.
This degradative aging begins at around age 21, when you begin to lose the strong healing capability of youth.
This means the time of "least aging" as you put it is going to be between puberty, in the mid teens, and age 21, when the body begins its slow decline, so between the ages of 16 and 21 or so. Since the decline doesn't begin immediately, you can stretch the upper part of this to the late twenties, so say between the ages of 18 and 30.
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Harpoons are cool, but as far as I know in the real world they've only been used in hunting marine animals so they don't float or sink away. Stone age hunters managed to hunt down mammoths using only spears, so I don't really see how a harpoon would be much of an improvement. Also, could harpoons even penetrate deep enough to prevent an animal from moving, but not deep enough to kill it instantly? Because if it can kill by penetrating deep enough, why be a harpoon at all, instead of just being a spear? Is there any reason to use harpoons on large land animals?
I'm asking this because I'm writing a story about an ancient fantasy world filled with large, dinosaur-like creatures in it, and I want to have a reason to include harpoons in it. So if you could also tweak a real animal's characteristics to justify using a harpoon against it, it would be welcome.
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A harpoon is a barbed spear with a tether, used at sea so you don't lose your prey after spearing it. On land it's usually not as necessary - if you prey starts limping away then you can just run after it and throw more spears - humans are very good endurance hunters. If it falls down dead, well then you're done, just go get it.
At sea, you need to hold on to what you speared because you can't just run after it. Let's make the same be true on land. I propose not a change to the hunted animals as such, but to the terrain. The areas where the beasts live are, for some reason or other, difficult or impossible to run through for humans, but not for the dinosaurs. It could be sharp rocks, big boulders, some kind of plant growth - whatever stops you when you have human sized feet but not when you have dino sized feet.
Let's say a jungle with thorny vines covering the ground. Humans can get thrugh by moving carefully or climbing the trees, but it's not fast. If they just throw a couple of spears at a dino it will bellow and run away, easily stomping through the underbrush. It would take some time to bleed out and collapse far away, by the time the humans got there lots of scavengers would have already done a number on the corpse.
Instead, harpoons. The hunter teams throw their harpoons and when they hit, quickly tie the tether to a nearby tree. This won't hold the target forever, but for long enough for the rest of the group to surround it and impale it a dozen more times. Each harpoon makes it more and more immobile, and finally it collapses at the spot. Dangerous hunting, but rewarding.
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Yes. Functionally a harpoon is little different from a snaring trap; it needn't be fatal, it just has to slow the beast down or hold it in place until the hunter or others in the group can move in for the kill.
The barbed tip of the harpoon acts like the tightening noose of a snare or teeth of the classic bear trap:
The only differences are the spear-like form, and you throw it rather than wait for an animal to stumble into it.
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What if kangaroos (specifically **eastern grey kangaroos**) became invasive in the eastern part of North America?
How would they effect native flora and fauna? What would they compete for resources with? What might eat them? How fast would their population grow? Stuff like that.
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Kangaroos are basically (for a broad definition of "basically") just upright deer. Indeed, a side-by-side comparison of the eastern grey kangaroo and the ubiquitous white-tailed deer suggests they share much the same ecological niche:
* They are ruminants with similar diets, mainly consisting of grass and low-lying plants of various descriptions. Deer in the eastern US mostly consume scrub and brush because that's what's most available, but in the west they're perfectly happy to graze on grasses. Conversely grey kangaroos are mostly grass-eaters but there are other species of kangaroo that prefer brush.
* They have broadly similar social habits, revolving around small family units. Kangaroos are more inclined to former larger groups, in the ~10 member range, though this appears to vary with geography.
* Their natural predators are similar... to an extent. Coyotes and dingos are very much akin to one another, being predatory canids of about the same size. However, North American predators can get quite a bit bigger than (extant) Australian ones. In the western part of the continent, kangaroos would have to contend with wolves and bears, but in the east they are less common.
* Their interactions with humans are similar. They are relatively skittish and typically pose no threat to humans (except on roadways, where they are both menaces to careless drivers).
* What kangaroos have, and deer lack, are a wide variety of coping mechanisms for extreme aridity that will virtually never be useful in the eastern US. (They might find some use for it in the west, but never to the same extent as in the Outback.) This suggests that they would be outperformed by native species until they manage to adapt. Wikipedia suggests they require a particular habitat to reproduce but doesn't say *what*; if this is taken to mean that they need access to the covered part of their range (with trees and brush) as opposed to the open grassland then they're fine. If their needs are more specific, it could be a problem.
* Conversely, kangaroos are probably less adept at surviving winter. They can readily survive temperatures down to the single digits Celsius, but rarely have to encounter multiple months below freezing as occurs in the northern part of their proposed range. They might fare better in the south.
* As for how fast they can grow: in theory, *very* fast. Finland has a population of about a hundred thousand deer descended from a handful of animals shipped over in the mid-30s, meaning a tenfold increase in population every 20 years or so. Your kangaroos will probably not be so fortunate, because of the different climate than what they're used to, but if they thrive in North America they could grow quite rapidly.
Tl;dr: the main problems would be adapting to a wetter, colder environment and potentially large predators such as bears. Their main competition would be medium-sized grazers like deer, and their main predators would be coyotes and the like.
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Eastern North America is heavily forested with high-density forests. Eastern Grey Kangaroos live in grasslands and low-density forests. The main advantage of being a kangaroo - the ability to jump - would be completely negated. They couldn't possibly compete with deer and would soon die off completely.
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If someone invented a field manipulator that created a region through which no form of light could enter or pass through, effectively making a sphere of complete darkness, what sort of practical applications might such a thing have?
It would appear from the outside to be a solid black sphere, and when inside it you would feel no ill effects other than maybe a little disorientation from the absolute darkness.
The size would be theoretically as big as someone could build the generator, but power wise, the biggest anyone would be able to make and sustain would be the size of a typical sports arena.
The zone would be spherical with the generator at the centre.
Sound, and physical passage through the field would be absolutely normal, so such things as RADAR would not be impeded, (from a "Stealth" perspective).
From a narrative point of view I'm trying to reconcile the funding that would have gone into such a device. Someone needed to say, "Ooh, I could use that for XX, here's lots of money... go do it."
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## Solve Global Warming and Climate Change.
Orbit the device around the Sun at the L1 Lagrange Point - and if the strength of field is related to its radius, change the sphere of darkness's radius to the point where it partially eclipses the sun and reduces the sun's light from reaching part of Earth.
Position it at the same location as DISCOVR:
[](https://i.stack.imgur.com/to3am.jpg)
By reducing the energy received from the sun it would be possible to control the amount of heat energy on Earth, and this could solve Climate Change and be desirable for:
* Oil companies, so they can continue to sell oil without everyone worrying about climate change due to fossil fuels
* Coal and Gas Power companies, so they can continue to burn fuel to supply power to the world, with the double benefit of harming their solar industry competitors
* Governments who don't want to change too much of the status quo without harming fossil fuel industry employment
Such a device could easily receive billions in funding from these interested parties.
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## **Military Origins: Spec Ops**
Perhaps this is not a commercial application, but most innovations start off with military applications, and then work their way into normal day to day life.
The darkness generator is the newest weapon developed by the army. Against a technologically underdeveloped or unprepared enemy, it provides a massive advantage by completely blocking off all vision as well as communications equipment (by also blocking off electromagnetic waves).
A specially trained Darkness Squad can set up the generator around their target, and have their own portable sonar devices and dead reckoning systems to guide them in the darkness. As @Matthew pointed out, they can communicate among each other using modulators and demodulators for their voices using sound frequencies beyond the range of the human ear (ultrasonic or infrasonic transmitters and receivers) which can be encrypted and decrypted for added security. Specially created weapons that fire based on sound cues, and melee weapons would most likely be their go-to method of attack.
With the Darkness Squads' superior communications and sensors, the enemies plunged into darkness and blocked off from any form of communication don't stand a chance.
An area the size of a football field is more than enough to shut down operations and communications in an entire building, and it makes it extremely difficult to send in reinforcements, due to the communications block off and lack of visual confirmation in the generator's area of effect.
## **Commercial Use: Agriculture**
Eventually, the world will have seen enough use of the generator, that easy ways to counter it will be found, discontinuing its usage for military purposes. Instead, it is now used in areas around the world for the agriculture industry.
Farming is one of the applications of the darkness generator. By employing the darkness generator, it is possible to fine-tune the amount of light any farm receives. This would be especially useful for areas that are too hot to plant certain colder-climate plants.
Farming in the desert could be achieved as well, as long as the soil and water conditions can be provided, the amount of heat and sunlight can be fine-tuned through use of the generator.
## **Commercial Use: Space Colonies**
Perhaps the most useful application would be the use of the darkness generator in space colonies on the outer planets.
By using the generator on habitation areas of a planet, it is possible to bring down the amount of sunlight, and thus heat, in certain habitation areas, bringing down the total temperature. Of course, this will not reduce the heat brought through the air from surrounding areas, but should help alleviate some of the heat wave from the ground in the generator's area, which will make otherwise uninhabitable areas much more bearable for habitation.
Also, with the blocking of electromagnetic waves, the darkness generator could drastically reduce the amount of radiation humans experience while on certain planets, such as Europa, where the radiation is enough to be [fatal in just one day](https://theplanets.org/europa/) (although blocking off just the sunlight for temperature related purposes would not be useful, considering Europa's temperature is something like -170 degrees).
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**Parents of young children and night shift workers**
People sleep better when it's dark. People who have to sleep during the day have a hard time. [Santhi et al (2005)](https://search.bwh.harvard.edu/new/pubs/Santhi2005.pdf) found that controlling the exposure to light and darkness can help the circadian rthyms of shift workers. When I was an overnight policy analyst, no amount of eye masks, blackout curtains, and other tools could replace the darkness of night. I would have gladly paid for a darkness generator that could generate a field the size of my head. That would have also let my wife go about her life and turn lights on in the apartment without waking me.
Sleep is also a big deal for young children. My wife is pregnant and we're already thinking about it. Being able to cast true and total darkness would benefit both parents and children. People spend [billions of dollars every year](https://www.grandviewresearch.com/press-release/global-baby-products-market) on baby stuff. I've recently realized that slapping the word "baby" on a product means you can charge extra for it, so the "GizTech 84A Baby Darkness Generator" could conceivably cost $1,000+.
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You want to write some fiction based on science, right? Because what you describe is either trivial or impossible.
Make one darkness generator with a cross-section of 1sqm. Put it in the Sun light. Every second, the thingy absorbs [about 1000J](https://en.wikipedia.org/wiki/Solar_irradiance) from the Sun's light when placed at sea level.
Now:
1. *trivial*: if the thingy heats up due to the absorbed energy, that's OK. The same happens with a piece of black cloth placed in the sunlight under vacuum - it absorbs visible light, heats up and radiates IR lights (thermal radiation) until it reaches a thermal equilibrium. You just created some sort of a [black body](https://en.wikipedia.org/wiki/Black_body)
2. *trivial*: if the thing doesn't heat up because it's somehow forcingly cooled down (the heat is evacuated), that's also OK - you just apply a cooling of the black cloth with a thermal pump instead of letting it emit a higher amount of IR light as before. Nothing wrong, you'll just create more heat in total.
3. *impossible*: if the thing heats up but continues to absorb energy for unlimited times, then you are in big troubles with the thermodynamics. The pesky second law says that the heat always flows *naturally* from hot to cold and if the thingy keeps heating from Sun light at one point will heat above the Sun's temperature (>5700K) but... say what?... continue to absorb light?
4. *impossible*: if the thing doesn't heat up and continue to adsorb energy - you have an infinite heat sink. Couple it with any heat source through a working gas in a piston and you have your contraption that allows the conversion of heat to work without increasing the entropy of the environment.
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A lot depends on how the tech works, and I like these ideas. Here are my thoughts.
* Power generation- If this absorbs power rather than reflecting it, it can be the world's best solar panel, with the advantage that it can be switched on and off, and not take up huge amounts of space. The energy use vs production issue would determine if it was practical or not.
* Alternative chemistry - Somehow this thing alters the output AND transmission of energy, so some specialized chemical reactions would behave differently inside the field.
* EMP protection - If this thing doesn't outright act like a Faraday cage, It would VERY likely help shield things from electromagnetic pulses, and could be switched on and off at will. If you placed this field around a computer and had really good surge protection, the computers could survive nearby nuclear explosions, solar flares, etc.
* Radiation shielding -A giant solar flare is coming at your space ship? NO PROBLEM. Switch on you gadget, and all those nasty gamma rays just (reflect/dissipate/convert/power your systems).
* All-thermal nuclear bomb - What would a nuclear explosion look like inside this field? It could either cancel it (which raises it's own interesting questions) or convert all that nasty output to something less, well, radioactive. I don't know enough about the physics, but I bet there would be a different KIND of bomb, one with more neutrons, all-thermal (ideal for a big but non-toxic explosion), or something like that. Whatever you decided, it could shake up global balance, and any military would throw money at answering the question.
* counter-surveillance - I'm guessing this isn't super-portable, but you could erect fields around a building or other sensitive target to block surveillance, lasers scanning windows to detect sound by measuring vibrations, etc. If you can create the field in a sphere and then cancel it in a smaller sphere, you have a shielded environment where no one can see in.
* Energy weapon force field - While the practicality of laser cannons is debatable, this would give you the ability to shield a space ship from a laser cannon or something similar. It could also block communication lasers to interfere with secure communications by enemies without actually damaging anything (again, more of a space application).
* Fusion power - If you field absorbs all light, including infrared, gamma rays, etc., could this be the means by which you could generate and store power from a fusion reaction? Not sure what the physics would look like.
* If you can adjust the wavelengths of the field to start affecting infrared, you start REALLY changing things like chemistry, manufacturing, the efficiency of power plants, or even stuff like how a furnace outputs heat vs infrared. On this one, the opportunities boggle the mind. That could be it's own answer entirely (feel free, anyone)
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Let us assume at some time in the near future, medical science perfects a biologically safe liquid air solution. It can fill up the lungs of the adult human subject and they can breathe it potentially indefinitely, the same as normal room temperature air at sea level.
Would the use of this solution for spaceflight applications have any noticeable benefits in terms of spacecraft maneuverability? Would it increase the g forces that the pilot can safely sustain far enough to make a kind of hard scifi "space gunship" possible? How about aerobatic spacecraft capable of performing tight racing turns and other flashy stunts?
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The filling the lungs in an incompressible fluid will increase the the g forces a pilot could handle since g-forces would be uniformly distributed evenly across the body, in side and out.
The pilot might need hydraulic assistance with respirating. The thinker medium might be too much load for the diaphragm and ribs to move in and out of the lungs. But, a device similar to a mechanical respirator wouldn’t be difficult to integrate into the pilots gear.
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**This would be a very bad idea if the liquid is like water.**
Alright, we need to explain a few things here about the difference between straight line acceleration and the kind of agile moves you describe in this question, and how a medium like water reacts in each case. To start with though, we have to explain something else; for all intents and purposes, water is non-compressible.
This is important because it's the **rate of change** that is going to get you killed in the above scenario. Water is heavy, and non-compressible, just like (say) a baseball bat. You drop a bat on someone's head from a height of around a metre, and they're going to have a sore head. You drop it from 50 metres, or worse, put some force into a downward swing on their head, and you'll kill them.
Now, a bat is solid, water is not. So dropping around 1.5 litres of water (about the same weight as a competition baseball bat) from 50 metres onto someone's head is going to give them a minor headache, but it's mostly going to just make them wet as the water can divert around the head in the atmosphere; a bat can't. In other words, the atmosphere is the MOST compressible element in that scenario, the water next, the head next, and the bat last. That is why you get the effects you do in this scenario.
BUT - Heads are the hardest part of a human body because it is protected by the skull. The torso, where all the internal organs that keep it running are housed, is far more compressible, and in your scenario, you've just taken the air out of the equation completely, making the water and the body, especially the torso, about the same compressibility but your body is now the most *deformable* element in the scenario, not the water or the ship.
In real terms, what does this mean? Well in the case of straight line acceleration, it means that the body can probably withstand *more* constant acceleration than it could in an atmosphere. Sure, there is a greater mass pushing on it, but the liquid is probably going to support the body better as the compressibility is similar, especially in the lungs where you would expect the first collapses to occur if you were breathing air scuba style in a liquid environment.
But agile combat moves are going to kill you.
The reason for this is that the rapid changes in direction caused by the moves means that there is a massive amount of energy in play because of the increased mass. The inside of your ship now is far more massive than you are, and it means that doing the same speeds takes far more energy, and the momentum changes are far higher than they are doing the same moves with only a small amount of atmosphere in the ship instead. Every banking turn therefore is throwing huge amounts of mass against you at speed and the impulses alone are going to do you internal damage if not kill you.
The good news is that you're not going to snap your neck because of a sudden turn, the liquid will support you far better than that. The bad news is you won't live long enough to enjoy it as the combat moves will likely liquify your internal organs.
You're actually going the wrong way; since the Apollo missions we've known that filling spaceships with less air is the better way to go. The Apollo ships carried around 0.3 ATM of pure oxygen, allowing astronauts to breathe normally and need less fuel (because they carry less mass), less ship (because the pressure differential with vacuum is smaller meaning you an get away with thinner hulls) and causes less stress on the ship during maneuvers (for all the reasons described above).
On top of that, if you are really talking for military purposes, especially a gunship, you'll find that future space gunships will go into a battle with their crews in spacesuits and NO atmosphere in the ship. Why? Well, first of all a single hull penetration doesn't kill the crew by evacuating the air, and it also means that if the hull IS penetrated, the escaping atmosphere doesn't cause unpredictable velocity changes in the ship by acting as a thruster.
So; if you really want to do liquid breathing, do it in a space suit so that the overall mass is lower and you get at least some of the benefits of liquid body support with far fewer of the drawbacks.
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**No**
You may be confusing two different tropes, namely filling the lungs with a fluid to help equialize the body while under constant environmental pressures (such as deep sea) vs G-forces.
G-forces impact the human body greatly based on the direction of the force. In some directions, it causes blood to pool in the lower extremities, keeping blood away from the brain because the heart is not strong enough to pump against these forces. Filling lungs up with fluid would likely make this effect marginally worse, but certainly not better.
If you want to try to make space craft more maneuverable using tech, maybe consider a gyroscopically stabilized, centrifugal-based pilot's chamber which will try to counteract the external g-forces, or at a bare minimum, make them impact the human body at the least negative angle.
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I normally ask sci-fi questions, but oh well...
It's fairly well established by this point that gills, while fine for fish, wouldn't work for mammals, as we need more oxygen than can reasonably be found in the water. This goes double for humans, since our brains use a lot of oxygen. Whales, however, don't use gills. Whales breathe on the surface, and stay underwater for anywhere between 20 to 90 minutes. And if you take a look at the tail of a traditional mermaid, you'll notice that it actually resembles the tail of a whale more than it does a fish (the exception is shown in the fourth Harry Potter movie. Those merfolk had fish-like bodies, which made them a lot creepier). If we go with the traditional depiction of a mermaid/merman having a human upper body and a whale-like lower body, it strikes me as being more realistic that merfolk would be air-breathers that need to come up periodically for oxygen.
We don't have to explain how merfolk could have possibly evolved. Let's assume that they were created via magic, or genetic engineering. Let's also assume that that upper body only has to LOOK human, internal organs can be rearranged. For instance, the upper body could be filled by a massive set of lungs twice the size of a human's, while the digestive tract has been mostly moved down into the whale body.
With this in mind, is it physically viable to have air-breathing merfolk who can routinely stay underwater (actively moving around, not just sitting to conserve oxygen like human record-breakers do) for at least 30 minutes, or are there too many biological problems with the whole concept?
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Your 30 minutes of underwater activity limit is tough, but it is eminently achievable... as you've noted, whales can already manage dives far in excess of that. Even looking at something a bit more human in scale, such as the [habour seal](https://en.wikipedia.org/wiki/Harbor_seal), you can see that they're capable of diving for [30 minutes](https://www.bbc.co.uk/news/science-environment-22870944).
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> For instance, the upper body could be filled by a massive set of lungs twice the size of a human's
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Seals and their relatives *exhale* before diving. They store their oxygen in [myoglobin](https://en.wikipedia.org/wiki/Myoglobin) (closely related to haemoglobin, but specialised for storage rather than transport) which is found in much higher levels in their muscles than in yours. There are other adaptations in other species which could be handwaved in, such as [crocodile haemoglobin](https://www.researchgate.net/publication/23111643_CO2_governs_the_oxygen_affinity_of_crocodile_blood) which is better at releasing oxygen than yours is.
You haven't specified diving depth, I note, and that *is* important. Seals and walruses and the like tend to dive deep, and for them having full airspaces that could get squished at depth is undesirable. For a shallower-living species, the ability to keep their lungs inflated gives them a little extra oxygen and a little more CO2 rejection capacity and both these things might help extend dive times.
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> are there too many biological problems with the whole concept?
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The major problem is habitat. Water sucks heat away quickly, and if your merfolk don't live in the warmest, balmiest places they can find, they might have problems. That harbour seal I linked above? Pretty round and a bit furry, you may note. Lots of blubber. Any mermaids (or merblokes, for that matter) you might meet in the north Atlantic, sitting on a rock and brushing their hair and singing away will have a generous layer of what some divers term "bioprene". "Rubenesque" ain't gonna cover it.
Those arms are also quite unhydrodynamic. Or that hair, for that matter. For a given time period, fairly human-looking merfolk aren't going to be able to swim as far or dive as deep as better adapted marine mammals, though they could use tools and have a *slightly* easier time of getting around out of the water.
The basic idea doesn't seem impossibly far fetched, though.
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FWIW, I always assumed that merfolk were not fish... the females are famously mammalian, after all. Sure, they're traditionally drawn with a scaled tail, but so were whales and even giant cephalopods, back in the day. The illustrators of antiquity were not necessarily very rigorous.
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First question: if you melted Europa's ice, would there be any land?
Second question (assuming the answer to the first question is no), how much water would you have to remove after that in order to get any land?
Another way of asking the question would be, what are the highest underwater volcanoes/mountains on Europa? I understand that currently it's about 10-15 miles of ice, and then 40-100 miles of ocean underneath that. So I'm guessing a lot of water would have to be removed to get the first islands but I'm having a lot of difficulty finding an answer online.
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[According to NASA:](https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth/)
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> From ground-based telescopes, scientists knew that Europa's surface is mostly water ice, and scientists have found strong evidence that beneath the ice crust is an ocean of liquid water or slushy ice. In 1979 the two Voyager spacecraft passed through the Jovian system, providing the first hints that Europa might contain liquid water. Then ground-based telescopes on Earth, along with the Galileo spacecraft and space telescopes, have increased scientists’ confidence for a Europan ocean.
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> **Scientists think Europa’s ice shell is 10 to 15 miles (15 to 25 kilometers) thick, floating on an ocean 40 to 100 miles (60 to 150 kilometers) deep.**
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So melting all the ice would reveal no land.
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As others have already explained, it would not be feasible to melt all of Europa’s ice, even for an alien species with advanced technology and nearly limitless energy resources. Even if you were to melt all of its ice somehow, you would just have a water world like many that already exist within the habitable zones of distant stars—one that would freeze over immediately. And that water world’s oceans would be dozens of miles deeper than any on earth. The only rock in Europa is the rocky core, which is way too deep to be exposed by melting ice.
Some context would be helpful. If you’re looking for an ice world or an ocean world with volcanic islands, there are literally trillions of those out there—just not in our solar system. Have you considered either Titan or Io as a possible alternative setting? Io is the most volcanically active body in our solar system, and Titan has oceans of liquid hydrocarbons on its mostly rocky surface.
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I think the answer has to be no land. Would be visable. As to how deep the ocean is and how far beneath the sea the nearest land is we simply don’t know for sure. I would estimate tens to a few hundred miles deep.
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I'm currently working on a fantasy world with a medieval/mythological setting, and I'm trying to do a bunch of research for several non-human races (dwarves, mermaids, etc.).
However I don't want to simply copy the versions of modern writers/cinema and would like to avoid sources that are based on novels, movies, franchises, video games, etc. (like orcs from Middle Earth or lamia from Monster Musume).
**I am looking for a source that contains traditional depictions and mythological lore of non-human creatures.**
I'm not asking you to describe different races.
Side note: I'm new here and doing my best to follow this site's rules. I apologize in case the question is wrong or vague and I'm glad for every answer.
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I don't think there is a single website or book I can point you to, but since I've spent a lot of time on similar searches, I'll try to give some general pointers.
First of all, keep in mind that the franchises you mention in turn got their information from somewhere else, so you can start by looking at their influences. Let's take Dwarves in Middle Earth: Tolkien got their names from the Poetic Edda to start, and used that plus other germanic mythology to create their characteristics, before putting them through the filter of his own imagination and free associations. **Look for books or interviews with creators to see what the sources of their fantasy races were, and keeping moving back until you get to one or more folklore sources.**
Second, keep in mind that folklore is messy, there is rarely one codified source that says what a dwarf is like. If there is such a source (like the Poetic Edda), keep in mind that this source was compiled by someone, taking centuries of sometimes conflicting versions of stories and trying to weave them into a coherent narrative where there was none originally. Therefore, know that you will never find a single definitive origin of a folklore creature. **Instead, look for how the description of a folklore creature varied over time and place, and choose the version or versions that appeal to you most as a writer.**
The first place I often start in trying to find out about how so and so author came up with a creature is just googling something like `Tolkien dwarves origin` and seeing what comes up. If you can at least pinpoint a cultural folklore that the creature came from, you can search your library or worldcat.org for books about that culture's folklore. Start with a survey work, and from there you can follow footnotes to find specific stories about the creatures you're interested in (hopefully translated!)
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The surface of Venus is about 492ºC, under a sky containing 92 atmospheres of mostly carbon dioxide, and it probably has been for many millions of years. This means the entirety of the planet's 50 km thick crust is at least that hot as well; the mantle and core being even hotter from radioisotopic decay.
If we magically removed 91 atmospheres of the Veneran atmosphere, and then made the remaining one identical to Earth's, how long do you estimate it would take for the planet to radiate away its internal heat to a point where an unshielded human could stand on its surface and survive? Hundreds of years? Thousands? Longer?
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You can actually observe most of the answer here on Earth. The key point is the heat conductivity of the Venusian rock is not very large. If the dense atmosphere was removed, the surface of Venus would be losing heat by radiating it into space. (It's also losing heat by convection into the atmosphere, but I believe that is a much smaller effect.) It is gaining heat by conduction from the bulk of Venus which is hot rock. As the surface cools, the rate of heat loss into space decreases and the rate of heat flow from the interior increases and the end-point temperature is where those two come into balance.
You can get a useful estimate of the time by considering the cooling of lava from a surface flow on Earth. We know that a flow only a few tens of feet thick will solidify entirely on the surface while the interior remains liquid (this is how lava tubes form), so we know that the lava is thick enough to be a good model for the much deeper hot rock on Venus.
A new lava flow cools to a solid surface within hours and is cool enough to walk on in days (provided no new lava underneath cracks the surface and allows new liquid lava out.) See [this web page](http://volcano.oregonstate.edu/how-long-does-it-take-lava-cool) for some specifics.
This is a lower limit for the time needed on Venus, since atmospheric cooling is much more effective on Earth than it would be on Venus, but it points strongly to the time needed to cool to be safe to stand on being days to months and definitely less than years.
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A friend of mine has a race of creatures in her headworld and has been wondering about a biological answer to justify the color of her race's blood even though magic is a bit sprinkled in there.
One character has black blood, so she wanted to know how would it be possible, or what explanations would be reasonable for a fantasy/otherworldly creature to have different shades of blood (different colors outside the red spectrum possibly)? What factors are possible to bring the creature to have this color in their bloodstream?
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That shouldn't be a problem. All it takes is another pigment in the blood that overshadows the red color of hemoglobin.
From an article:
<https://www.smithsonianmag.com/smart-news/some-reason-these-lizards-have-toxic-green-blood-180969103/>
*"A group of skinks that live in New Guinea and the Solomon Islands have blood that is lime green. Now, researchers are beginning to figure out just how and why the little reptiles developed such an unusual and vibrant vital fluid.
The lizards, which are all classified in the genus Prasinohaema (meaning “green blood” in Greek), were discovered in 1969.
“The bones are green, the muscles are green, the tissues are green, the tongue and mucosal lining is green,” he says.
That’s because they are stewed in a green pigment called biliverdin. “There’s so much green pigment in the blood that it overshadows the brilliant crimson coloration of red blood cells.”
In most animals hemoglobin cells die after about four months of service. The liver then gathers them and takes out the iron, creating the green waste product biliverdin, which is later transformed further into yellow bilirubin. If too much of these toxins build up in the blood, it can cause a yellowing of the skin called jaundice. If excessive amounts of the pigments accumulate, it can be fatal.
But not for Prasinohaema lizards.
They can keep going despite having 20 times the highest concentration of biliverdin ever found in a human. And for the person, the level was fatal.
Whatever the reason why the skinks have green blood, the fact that they can survive so much biliverdin is interesting and could provide biomedical insights.*
To have black blood, you just need something like a liver that works differently than in humans, which release a black pigment or substance into the blood. Or is produced by a specific gland that does nothing but producing the pigment. This would color the otherwise red blood black. The reason for releasing the black substance into the bloodstream? All I can think of is that it has certain properties regarding healing, immune system, sexual selection, a sign of vitality (a tongue that is not totally black means less pigment in the blood, and the individual could be sick or something and will not be selected as a mating partner), or it could have magical properties. There should be plenty of ideas out there to pick from.
(I also noted some anonymous member gave this thread a downvote, so I voted it back up. It really annoys me every time someone abuse the downvote function. Just mentioning it because it shouldn't hurt to point out the problem.)
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Yes, it would be possible, especially in a fantasy world. Our blood is red because of the oxygenated iron it contains. Their blood would simply need to use a different method to transport their vital gas fuel through their body. The first thing that comes to mind is carbon, which also bonds to oxygen, forming CO and CO2. If they use carbon dioxide, perhaps the race is more animate plant than animal, and uses CO2 to process food directly in its cells? Fungal base form would also be an option. Of course, fantasy allows (depending on if it is high or low fantasy, but as we are already talking non-human race so more high than low) magical corruption, artificial creation, etc are always options.
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**EDIT:** As many have pointed out, the whole Lunar Collision aspect I originally envisioned is probably more extreme than I predicted. I don't know where to start as far as the math goes, although my gut instinct says that a series of smaller collisions could make it work, but **I could take or leave the Moon getting enough mass to be habitable.** That's just a thought I had mostly for spectacle. **The important part is that in modern times, a K-Pg level impact or series of impacts occurs, so what organisms are likely to survive that?**
**Original Main Body:**
An origin I'm considering for the Science Fantasy world I'm building is that in the not too distant future, next Sunday A.D., a foreign celestial body or cluster of asteroids/comets joins Earth's orbit, then collides and merges into the Moon, adding enough mass to it that it eventually gets oceans and an atmosphere, and spreading debris around that peppers the Earth with meteorites for the eons to follow. The first wave of meteor crashes causes a mass extinction event comparable to the K-Pg impact.
So here's my question: **What notable modern organisms will have died out or diversified after a new K-Pg type event**, which also includes the moon's mass drastically increasing?
I of course searched for more generally related threads before asking. I'm *not* talking about:
[Would animals really mutate in the post-apocalypse?](https://worldbuilding.stackexchange.com/questions/106164/would-animals-really-mutate-in-the-post-apocalypse/) This thread is just talking about radiation-induced mutation.
[What is the next dominant species?](https://worldbuilding.stackexchange.com/questions/3226/what-is-the-next-dominant-species) This is asking what non-primates might become like humans, not quite what I'm looking for.
[What aquatic creatures would survive a large-end mass extinction?](https://worldbuilding.stackexchange.com/questions/106176/what-aquatic-creatures-would-survive-a-large-end-mass-extinction) This is too specific to the ocean, and also assumes that no life larger than an insect survives the impact. My apocalypse isn't quite that extreme.
In my scenario, humans just barely survive, evolving into at least 8 species and reverting from modern/futuristic to stone-age tech until about 10,000 years before the actual story begins, and they make some pretty drastic adaptations to make it through, even with their intelligence. So with that as a benchmark, what other life forms will make it, and which ones won't?
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Since you mentioned K-Pg: All animals above a certain (small) weight went extinct. They could not hide fast enough nor could meet their food demands after the event.
But your event will be much worse then K-Pg was, I don't think anything above bacteria, some tough bugs like the tardigrades or fungi will survive. It won't be a single rock, but thousands of huge, [Sudbury Basin](https://en.wikipedia.org/wiki/Sudbury_Basin) level impactors.
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**Anything on land larger than a cat will die**
No ifs, ands, or buts. In the actual K-T, large animals across the board were wiped out with little fanfare. These include things like [terrestrial pseudo-tortoises](https://en.wikipedia.org/wiki/Nanhsiungchelyidae), cat-sized [multituberculates](https://en.wikipedia.org/wiki/Meniscoessus) and [marsupials](https://en.wikipedia.org/wiki/Didelphodon), and other members of groups that otherwise had low losses.
So your small generalists like raccoons, rabbits, and the Virginia opossum? They will die. They're just too large to survive in a post-apocalyptic neo-K-T hellscape.
This includes humans. Humans ***will not*** survive a K-T scale extinction, whatever you throw at them. It's thought that after the meteor impact you didn't have any new plant growth for as little as a few years to as much as a century after the impact. Most plants likely regrew from dormant seeds in the Earth, and even then it took a long time on a human timescale for "normal" vegetation to reassert itself (the immediate aftermath of the K-T is characterized by a "fern spike" where weedy plants like ferns were the dominant plants until trees and shrubs got established). Imagine years with no new plants. Humans barely survived [one year without a decent growing season](https://en.wikipedia.org/wiki/Year_Without_a_Summer). Our species isn't going to survive off of seeds in the earth, hibernating squirrels, and whatever we can dredge out of rivers. Our megafaunal butts put too much demand on a post-crisis ecosystem for us to survive long-term.
**The largest proportion of survivors will be from freshwater aquatic ecosystems**
Freshwater ecosystem are what are known as "brown" food webs. They are food webs that are less dependent on the sun than either marine or terrestrial food webs, because if the sun is cut off they can survive off of dead or decaying organic matter and aren't intrinsically tied to photosynthesizing land plants or phytoplankton. Semi-aquatic land animals that are otherwise tied to freshwater food webs are more likely to survive. For example, in the K-T most crocodilians actually went extinct, the ones that survived were either those that lived in freshwater all their life (eusuchians) or returned to fresh water to breed (dyrosaurs). Even sebecids, which were mostly terrestrial in the Cenozoic, are suspected to have survived in the form of semi-aquatic freshwater representatives and re-evolved terrestriality, some of the earliest Cenozoic sebecids are semi-aquatic. Modern birds are suspected to largely be descended from waterbirds that could feed off of brown foodwebs until plants re-established themselves. Notably, modern birds (Neornithes), were a minority in Cretaceous ecosystems, whereas the dominant bird groups (Enantiornithes, Hesperornithes, Omnivoropterygidae, etc.) all died with no survivors.
This is why the fact that freshwater ecosystems are disproportionately affected by human industrialization and pollution is such a big deal, because we are basically killing our back-up drive for the biosphere. Expect higher than usual casualties compared to the K-T because rivers, lakes, and wetlands are some of the most degraded ecosystems in the present day, and therefore will be less robust to mass extinction events. I'd still rather be a shorebird than a land bird in this scenario, though.
**Mass casualties even among the groups that survive**
One thing that is often underappreciated in the K-T is it is not as if the dinosaurs and other megafauna were selectively removed from the environment and the mammals all got through with little casualties. Many of the groups we see as "victors" of the IRL K-T barely squeaked through the extinction. For example:
* Crocodilians suffered mass casualties in the K-T. Only generalized freshwater taxa survived. Casualties included the herbivorous *Simosuchus*, the mahajangachampsids, the terrestrial baurusuchid sebecosuchians, the small, generalized allodaposuchids, etc. Specialized freshwater taxa like the turtle-eating *Brachychampsa* also went extinct.
* Only one clade of birds (Neornithes) and possibly as few as five lineages (ancestor of modern palaeognaths, ancestors of modern ducks and geese, and *Qinornis*)
* Upwards of 75% of all mammal species died in the K-T, including many groups of multituberculates, placentals, and marsupials
* Insects won't care. Insects barely even blinked in the IRL K-T, the only mass extinction to ever significantly affect them was the P-T. You might get a big die off among insects that specialize in parasitizing or living symbiotically with particular plants and animals, like ichneumon wasps, bees, etc.
**Generalized mammals will be more likely to survive than specialists**
This is one that's kind of a no-brainer, but it bear repetition. [Before the K-T extinction in North America marsupials and multituberculates were actually both more diverse in terms of species and ecological niches than placentals, which were mostly omnivorous generalists](https://pubs.geoscienceworld.org/paleobiol/article-abstract/39/3/429/110457/Mammals-across-the-K-Pg-boundary-in-northeastern?redirectedFrom=fulltext). Marsupials were the ones that included specialized fruit-eaters, most of the specialized carnivores, and even semi-aquatic and burrowing colony-dwelling forms. However, marsupials and multis were disproportionately affected by the extinction because of this (As well as the few specialized placental lineages like the zalambdalestids), and as a result it was the few generalized placental lineages that took over the place after the meteor hit.
**Disproportionate extinction of arboreal animals.**
Arboreal animals did really, really bad across the K-T boundary. Mostly because the forests they lived in all burned down.
**Most survivors among mammals will be hibernators or can go into torpor**
[This is something that has actually been studied in some detail](https://royalsocietypublishing.org/doi/10.1098/rspb.2014.1304). One factor that has been suggested to have aided in mammal survival across the K-T, especially since so few of them are associated with brown food webs, is the fact that they could just hibernate through the extinction. So mammals that can hibernate or go into torpor to conserve energy will do better than those that cannot.
Similarly, mammals that burrow or dig their own burrows will have a disproportionate survival rate, since they have ready-made shelter for when the impact hits.
**Complete collapse of ocean food webs**
The real K-T showed a complete collapse of ocean food webs, with animals with a planktonic lifestyle or dependent on plankton as the base of their food web disproportionately affected. For example ammonites, which were the dominant free-swimming animals and had a planktonic larval stage, were wiped out with no exceptions. The dominant reef-builders (rudists and inoceramid clams) also all went extinct. With the exception of sharks and some marine crocodilians, all of the marine megafauna present in the late Cretaceous (ichthyodectids, carnivorous pachycormids like *Protosphyraena*, protostegid turtles, mosasaurs, plesiosaurs) was wiped out. Large filter-feeders (pachycormids) were completely wiped out, and notably *none* of the living large filter feeders (whales, basking sharks, megamouths, manta rays, etc.) seem to have origins that predate the K-T.
**Wherever the meteor actually hits will be disproportionately impacted**
You can see this in North America. Prior to the K-Pg North America had a diverse fauna and flora which included a large number of non-teleost actinopterygians, marsupials, multituberculates, gingko trees, and dawn redwoods. Then the meteor hit and just about sterilized the North American continent, made worse by the fact that the angle of impact would have showered North America with the worst of the debris. Most of the groups that had North America as their stronghold of diversity pre K-T are reduced to relict groups today largely because of that impact, whereas North American ended up being mostly recolonized by groups that had their centers of diversity in Asia (like placental mammals).
**Winners**
* Shorebirds (esp. seagulls
* Crocodilians (it's time to reconquer Earth...again)
* Rodents
* Small ground squirrels like chipmunks are of particular note here, as they are 1) hibernators, 2) burrowers, and 3) omnivorous
* Shrews
* Smaller opossums like *Marmosa*
* Native marsupials and rodents reclaim Australia from the foxes, cats, rabbits, and other Holarctic invaders
* Sharks (they won't win, but they won't suffer huge losses either. Just keep trucking on.)
* Grass (will do better than most plants because they are highly resilient and wind-pollinated)
* River turtles
* Amphibians (surprisingly enough despite predictions of acid rain there are little to no extinctions among amphibians across the K-T)
* Freshwater fish (no more humans to pollute their water, plus an entire ocean that's just begging to be re-invaded)
**Losers**
* Ungulates
* Xenarthrans (armadillos have a better chance than most, but they're still too large)
* Primates (no forests, mostly frugivorous, large)
* Carnivorans (the smallest weasels or civets might survive, but it's unlikely)
* Marine mammals
* Tortoises
* Coral reefs (will probably go completely extinct and be refounded by some other reef-building organism in the aftermath)
**EDIT:** With regards to your moon question, it just won't work. The moon right now isn't habitable, it has no atmosphere, isn't large enough to maintain it's own magnetic field, and unlike Titan or Europa isn't in orbit around a gas giant where tidal flexing can provide those things for it. Adding enough mass to make the moon habitable will make the moon *stop being the moon*, it's gravity would be so great it would either end up impacting the Earth (which *will* probably end all life on it by turning the entire surface into molten slag, akin to the Thea impact), or it will break free of Earth's gravity well and establish its own orbit (this seems less likely based on my understanding of physics, but I'm not a physicist or astronomer). Either way losing the moon means Earth loses its habitability, as it no longer has a large orbital body to stabilize its orbit.
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With the amount of energy in a collision required to *drastically* increase the mass of the moon, the amount of matter raining down on Earth would be enormous. A significant portion of the Earth's crust would become molten (bye bye Oceans). We say life always finds a way, but there are no reservoirs of life in the mantle. The chances are that no life would survive, unicellular or otherwise.
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Assuming the impacting body has about the same mass as the Chixulub asteroid, the effects are going to include massive global cooling (one or more "years without a summer", followed by a long-term trend of significantly colder weather), reduced sunlight levels from atmospheric ash, and widespread forest fires in the area of the new impact basin.
In the K-Pg event, the ecological niches that were hit the hardest were large land-dwelling animals and shallow-seafloor biota. Animals with a smaller overall body size (fewer calories needed to survive) and that were adapted to colder climates tended to survive and diversify. For instance, birds (being dinosaurs, taxonomically) have diversified so much over the Cenozoic that there are as many extant species of Dinosauria now as there were in the late Cretaceous.
So, the fauna that would be most likely to survive this hypothetical mass extinction would be deep-ocean and arctic species, as well as generalists- anything that wouldn't be wiped out by the loss of one particular food source.
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The Crystal Desert is a Sahara-like expanse of sand, dotted with numerous large clusters of crystal, and containing numerous monolithic sandstones. What would we expect Thra geologists to determine are the processes that led to its formation?
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## It might be salt!
The most likely explanation is one that occurs frequently on Earth already. Here, massive salt deposits are formed when oceans are temporarily connected to inland basins, flooding them with seawater and massive quantities of salt. Later, that tenuous connection is severed and the salty water is left to evaporate, [leaving behind crystals of all shapes and sizes](https://www.youtube.com/watch?v=Nw0aY3SXIdg). [XKCD's What-If article](https://what-if.xkcd.com/152/) on a similar topic is also required reading.
### Considerations:
Salt is a highly likely candidate, but is a little underwhelming coming from the realm of science fiction or fantasy where such crystals are large enough to build houses in. The main disruptive force when creating crystal deserts out of salt is that the water is often turbulent, stirred up by wind and tides. Crystals grow best in hypersaturated, tranquil waters, so regular disruption will place a maximum probable size on the crystals you'll get from a desert formed like this. Many of the pictures of Dead Sea salt, for example, are slightly deceptive - these crystals are rarely found more than an inch or two in size.
[](https://i.stack.imgur.com/Ub7iJ.jpg)
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> Photo: Ievgen Sosnytski / Shutterstock
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To maximize salt crystal size, one tactic might be to use an incredibly deep basin that's later uplifted. Crystals at the bottom of this basin would grow slowly but steadily, with less disruption from the surface and the added bonus of the extra-salty brine that sinks to the bottom
## It might be glass!
[Fulgurite](https://en.wikipedia.org/wiki/Fulgurite), better known as lightning glass, is an alternative option. This wouldn't be *crystal* exactly, as glass is technically an amorphous solid, but it'll look much the same to travelers. When lightning strikes silica-rich landscapes like beaches or deserts, it melts the silica and produces glass. Once the nearby non-lightning-ed sand is eroded away, you're left with the glass itself sticking above the surface.
[](https://i.stack.imgur.com/nkZLL.jpg)
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Alternatively, meteor impacts also produce glass if they strike deserts or other silica-rich areas. This aptly named impactite is often larger and more striated than fulgurite, but much rarer and harder to establish on a world with pre-existing life. Credit goes to [this Worldbuilding question for this idea](https://worldbuilding.stackexchange.com/questions/152504/how-can-glass-marbles-naturally-occur-in-a-desert)
### Considerations
Again, this is probably too small-scale for what you're hoping for. Fulgurite specimens rarely get above a few feet in size, despite [what the internet would like you to believe](http://blogs.discovermagazine.com/but-not-simpler/2013/07/02/what-really-happens-when-lightning-strikes-sand-the-science-behind-a-viral-photo/#.XXKOLihKiM8).
One of the joys in working with Worldbuilding is that we can play with the environmental variables a little bit. Here, we'll need really big lightning bolts. I don't know enough of the physics involved in what exactly causes lightning, but [neither does anyone else](https://xkcd.com/1867/).
From [NOAA's website](https://www.nssl.noaa.gov/education/svrwx101/lightning/):
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> The creation of lightning is a complicated process. We generally know what conditions are needed to produce lightning, but there is still debate about exactly how a cloud builds up electrical charges, and how lightning forms. Precipitation and convection theories both attempt to explain the electrical structure within clouds.
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> Precipitation theorists suppose that different sized raindrops, hail, and graupel get their positive or negative charge as they collide, with the heavier particles carrying negative charge to the lower part of the cloud.
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> Convection theorists believe that updrafts transport positive charges found near the ground upward through the cloud while downdrafts carry negative charges downward.
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If even NOAA scientists don't know exactly what's happening, it's simple enough in a fictional story to assert that your world has enormous lightning storms that can fuse huge areas of the desert into glass. The bigger the lightning, the larger the area fused, although you'll start getting gaseous silica above 2,200 oC. Then again, [lightning strikes are getting bigger on Earth](https://www.smithsonianmag.com/smart-news/longest-thunderbolt-ever-recorded-rewrites-definition-lightning-180960508/) too so maybe all we'll have to do is wait and find out.
Alternatively, you could have a desert-wide area bombarded with meteorites during something like a junior version of the [Late Heavy Bombardment](https://en.wikipedia.org/wiki/Late_Heavy_Bombardment) but this one has the difficulty of 1) probably wiping out all life on the planet and 2) each successive meteor strike would likely shatter any pre-existing glass, turning it back into sand.
## It might, in fact, be crystal!
This is probably what you wanted all along, right? Beautiful images of [Naica's crystal cave](https://cen.acs.org/physical-chemistry/geochemistry/Naicas-crystal-cave-captivates-chemists/97/i6) have been circulating the internet since its discovery in 2000, and the crystals seem to be exactly what you're looking for. "Luminous beams of gypsum bigger than telephone poles, nearly 12 m long and 1 m wide, jutting in all directions out of the brown limestone walls, floors, and ceiling."
The Naica cave is truly a marvel. Those crystals are estimated to have been growing for literally millions of years in the perfect conditions. The connected Cave of Swords has more abundant, but less sizable crystals because the conditions were slightly different, and many places have no crystals at all.
### Considerations
This type of crystal formation is certainly the most fantastic, in the literal sense of the word. However, the conditions need to be absolutely perfect, and maintaining those over an area the size of the Sahara is nigh-impossible. Given also the time required, this is a less-feasible solution - or at least less likely. Then again, it's your story! There's a lot to be said for doing what works best, and if a few geologists complain it won't be the end of the world.
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This isn't an exact match, but a similar situation could do it.
[Geology of White Sands](https://www.nps.gov/whsa/learn/geology-of-white-sands.htm)
Essentially, water disolves the minerals from surrounding mountains into a central depression. While there is enough seasonal rainfall to gather this mineral-enriched water to a central area, during the dry seasons much of the water evaporates and leaves the concentrated minerals to grow crystal formations.
These formations break down into smaller and smaller grains, eventually forming the sand which the wind forms into dunes.
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There is a group of people who can shapeshift. They send out hunting parties, scout teams, etc. In a circumstance where a group of ten people can look like ten different species (one human, one wolf, one demon antelope, etc.) is there any way they can communicate effectively across team members without having to change shape back to a species with greater vocalization ranges? Telepathy is excluded as an option.
The best answer would be that which allows for the most complex information to be shared in the most quick and efficient manner. For example, "scent glands" could feasibly be integrated into just about any form a person takes, and used to emit smells for communication, but one weakness as an answer is that it seems difficult if not impossible to convey more detailed information using this method. My benchmark for a useful method would be the feasibility of saying something basic, but with details, like: "two people, north, armed with spears, riding horses."
I should probably also clarify we are talking all generally "person-sized" animals here, not a three-inch-long mouse trying to communicate with a two-story-high dragon. The shapeshifters are limited in the extent that they can re-proportion their mass, and can only turn into physically possible animal species.
Edit: Some clarifications that came up in the comments.
For the purpose of this question, let's use humans as the baseline for the shapeshifters in their natural form, with all the assumptions inherent to them (possessing a developed verbal language, high intelligence, etc.) Any differences that suggest themselves as significant I will try to state and clarify as necessary.
The shapeshifters have some degree of adaptability, but have to start with an existing animal as a blueprint. basically they can't do anything not biologically practical. AKA you can start with a giant cat beast, then proceed to make the fur longer or change its color, change your build a bit, etc., but if it wouldn't be functional on the actual animal, it isn't going to work for you either, and may be prevented due to inbuilt shapeshifting failsafes. You probably can't add unbalanced tentacles to your giant cat, but you can likely make your tail longer.
There is an extent to which the shapeshifter's own inherent internal structure is required to be retained as well. For instance, the biological components (such as a shapeshifting-devoted internal organ, their brain, and their blood) related to the shape-shifting process can't be altered or eliminated. Nor can the shapeshifter's cells turn into anything not a natural organic part of their body. So, they can create hair (or fur), bone, skin, muscle, claws (or horns or tusks or scales) etc. etc. But they cannot turn a part of their body into metal, being non organic, or bark, since, despite being organic, it isn't made from the same sort of materials their natural body is (I think?). So while you might be able to shapeshift a bone exoskeleton or scales as natural armor when fighting, you couldn't turn your arm into a steel sword or your skin to iron.
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**Charades**
You could have them shape shift into what they are trying to communicate, in the example you used, a shape shifter would turn into: a person, the number two, a compass pointing north, a spear and a horse.
However, this seems too comical and does not feel like it is in the spirit of what you are asking. Instead, i propose a more serious answer:
## Morse Code
Perhaps one of the easiest forms of communication, it is simply a series of short stimuli and long stimuli. This could take the form of anything, the flashing of a light, the noise from the tapping on glass, even tapping on someone’s shoulder so they can feel it. With morse code you can say literally anything in the English language (or any language really, assuming you have sequences that correspond to all of the letters in its alphabet).
One issue with Morse code though is it takes a long time to communicate a message, every sentence is made up of a number of words, each word is made up of several letters, each letter is made up of several short and long stimuli. In short, it takes a long time, you want sentences to be as short as possible to be communicated as fast as possible.
**Abbreviated Morse Code**
As Morse code takes a long time to communicate, you could instead have codes for words or phrases. You would need a list of common words that your shape shifters would communicate and attach codes to them. For example “... - - - ...” means SOS. In English, SOS is not a word, it is however an abbreviation of Save Our Souls, indicating someone is in danger and needs help.
In your case, you may have abbreviations such as SRD (sword), SPR (spear) MAN/MEN (person/people), HRS (horse) etc. If you then string several of these abbreviations together, you can communicate phrases quite quickly.
You may even have secret phrases communicated through abbreviations. For example, “XRT” may mean “Be alert, the king has left the castle, ready your archers” but there is no possible way you could have guessed that is what XRT meant, not in the same way you could guess SPR means Spear. Only those who were told what the code meant would understand it, preventing spies from intercepting it.
[](https://i.stack.imgur.com/sRwbo.png)
<https://en.m.wikipedia.org/wiki/Morse_code>
Here is a chart for International Morse Code so you can create your own abbreviations and know how to communicate them.
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# Ultrasonic clicks.
Albeit this is much more efficient in a liquid medium (so it's used by dolphins), an acceptable range might be achieved with an ultrasonic "clicking" organ and suitable ears (they needn't be too big).
This could also double as an active echo-location sonar, very useful for scouts.
Once the clicking mechanism is in place, you have a choice between a click-language or using clicks to code another language (this would be Morse code for example).
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Just out of curiosity I've googled 'the minimal number of sounds in a language' and arrived at the Wikipedia page for [Rotokas](https://en.wikipedia.org/wiki/Rotokas_language).
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> The Central dialect of Rotokas possesses one of the world's smallest phoneme inventories. (Only the Pirahã language has been claimed to have fewer.) The alphabet consists of twelve letters, representing eleven phonemes. Rotokas has a vowel-length distinction (that is, all vowels have a short and long counterpart) but otherwise lacks distinctive suprasegmental features such as contrastive tone or stress.
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It means, that eleven distinct phonemes is enough for a functional language. If your shapeshifters are humanoid with developed vocal apparatus in their base form, they can communicate normally in this form. So, they need only a secondary, limited, purely functional code-like language for their shifted forms. They do not need even that many phonemes for their 'hunting cant'. I think, for the purpose of communicating in the shapeshifted form, they would be able to make do with a language with 5-6 distinct phonemes that is possible to pronounce by all the animal forms. They need only a small dictionary to quickly coordinate in the field, after all, not a developed language to communicate abstract terms - I'm thinking about something similar to the 'battle languages' in Dune.
([Here](https://worldbuilding.stackexchange.com/questions/45328/what-phonemes-would-a-snouted-animal-e-g-dog-or-cat-be-able-to-pronounce) is an interesting older answer on the topic of animal speech).
[Answer]
**Option 1**
They can shapeshift their skin to mimic the one of some octopi. In that way the skin can act as a screen, where messages can be displayed and read up to a certain distance. This would enable silent communication, which for certain types of mission is or paramount importance.
**Option 2**
They can keep a human vocal system, so that they can still articulate speech while in another form.
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The square-cube law holds true only for objects that are similar. In evolution, you can't make big leaps forward, but since most fantasy worlds are created by gods or people who think they're gods, I'm free to abuse Intelligent design.
Dragons have six limbs, the 2 wings are situated near the front legs, but just far enough not to interfere. Their (the wings') anatomy as of now is pretty much the same as avian wings and flight muscles.
That being said, assuming dragon bones are much stronger, thanks to some nanoscale engineering and a hint of graphene, how could the wings' pectoralis major, and the bone connecting to it, be rearranged to produce more power for the same mass?
Note: Before we veer off into the deepest insanity, I was thinking more of the "If strength is the function of muscle cross-section, can't we just shorten the fibers and increase the cross-sectional area, like a boss?" path.
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When I was a teen it was common for us to have a 50 cc scooter which, by law, could not exceed the speed of 50 km/h. When some of us wanted to tune up the scooter and get more out of the engine, one of the trick was to change the carburetor or the exhaust (or both). (**don't try this at home, going at 110 km/h on normal roads with something designed to go at 50 is not only illegal, but also mighty stupid and a fast way to have an early funeral**)
This trick would have allowed the engine to output more power with the same volume of the cylinder and the same structure.
How does this apply to your dragons? Well, you don't need to redesign the muscles/engine, just increase the metabolism of the beast, allowing it to burn more nutrients and output more energy with the same structure.
Incidentally, this is the same trick used by birds, which allow them to be able to fly.
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Your dragons are currently big pigeons: giant pectoralis for downstroke, presumably proportionately small supercoracoideus for upstroke. [Background reading](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130450/#RSTB20100353C40)
But you could take advantage of graphene and the rule of cool and model your dragons on a unique bird: **the hummingbird**.
<https://en.wikipedia.org/wiki/Bird_flight>
>
> Most birds that hover have high aspect ratio wings that are suited to
> low speed flying. Hummingbirds are a unique exception – the most
> accomplished hoverers of all birds. Hummingbird flight is different
> from other bird flight in that the wing is extended throughout the
> whole stroke, which is a symmetrical figure of eight, with the wing
> producing lift on both the up- and down-stroke. Hummingbirds beat
> their wings at some 43 times per second, while others may be as high
> as 80 times per second.
>
>
>
Hummingbirds fly like insects. Their wings move with a sort of sculling motion, and the pectoralis and supercoracoideus are closer to symmetrical in their contributions. They generate vortices as part of their lift mechanism, which would be so cool for a dragon because it would generate dust devils close to the ground.
One could argue dragons are too big and heavy to fly like hummingbirds. I refer these naysayers above to "graphene and rule of cool" and suggest they devote their skeptical energies to the problems inherent in breathing fire.
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>
> how could the pectoralis major, and the bone connecting to it, be rearranged to produce more power for the same mass?
>
>
>
The *pectoralis major* connects to the arm bone, so I am going to offer a solution that is biologically plausible:
Due to some mutation, some dragons are born with thw front legs and the wings partially fused. This adds a lot of muscle power to each wing stroke.
Over millenia (or maybe longer spans), the dragons evolve to have only four limbs. The wings get ever more muscular, achieving your desired result.
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You could look at the pterosaur called [Quetzalcoatlus](https://en.wikipedia.org/wiki/Quetzalcoatlus). It is thought to be the largest flying animal ever, with a wingspan estimated to be 10-11 m. Modern estimates put its weight at 200-250 kg. Earlier estimates put their wingspan at as much as 21 m, so we must assume that this much is possible for such a beast - and a dragon with a 20 m wingspan and a weight of (say) 400 kg would be quite impressive.
There are differing theories as to how well they flew, but a recent computer model suggests that Quetzalcoatlus was capable of flight up to 80 mph for 7 to 10 days at altitudes of 15,000 ft.
Quetzalcoatlus was built very differently from a dragon, with wings far to the back (see figure), but the important thing is that a flying of that size has existed, and hence, a dragon of similar size should be possible without bending physics. If your dragon is firebreathing, it could possibly blow fire beneath itself to create brief thermals for quick lift-me-ups.
[](https://i.stack.imgur.com/BeYQ6.png)
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No, the square cube law applies to many aspects of flight, the wings have to move enough air to counteract the weight of the animals.
As for changing the muscles it will not help, making a muscle shorter also makes the distance it can travel, that is the length change during contraction, smaller, your muscles will be super powerful but move all of half an inch. Which means your dragon can't really flap its wings. trading length for thickness doesn't gain you any flight capabilities. the total lift generated does not improve by making the muscles shorter and wider.
Making the bones stronger helps by reducing the overall weight of animal and reducing the weight of wings specifically, a lighter wing requires less force to move the same amount of air (because the muscles have to move the wing as well as the air). Because of this the gains you can get are pretty small, not insignificant but not all that great either. The wings still have to move enough air to counteract the weight of the animal, that is the real killer about the square cube law, the mass of the animal and the amount of air you need to displace to counteract it.
The power to mass relationship of muscles is a pretty hard limit, birds have done everything they can while keeping the muscles functional. You can have system to reclaim so of that energy (kangaroo tails) but the initial energy still needs to come from the muscles. As long as dragons are carrying around superfluous limbs they will be hard pressed to even reach the same size as birds.
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The main problems with a big dragon are, by increasing order of importance:
* Muscle power density
There can be linear motors (in a broad sense, what muscles are) that are powerful enough per mass or volume. For an unusual evolution that solved the latter problems, this would be straightforward enough. As we'll see later, this is not even the limiting factor in human strength under normal circumstances.
* Muscle strength
The muscle has to not tear itself and its supports apart (something human muscles *will* do if you use them at max power). Look up tetanus symptoms - or not, muscles at full power are horrific stuff. But there are materials stronger than human tissues that exist, and that could reinforce dragon tissues. Carbon nanotubes and graphene are rather popular choices, nowadays. Aggregated diamond nanorods can make for pretty nice bones as well.
* Fuel intake
Muscles need oxygen and sugar (or whatever this organism may use). Those are carried by blood. Sugar level could be increases quite a lot with the right biochemistery, as long as it can metabolize its reserves (probably fat) fast enough to keep up. Oxygen is a bit trickier. Blood could carry more, but oxygen intake is limited by the lungs. They would need not only big ones, but probably something more efficient [like a biological supercharger](http://www.projectrho.com/public_html/rocket/aliens.php#wings). Waste products like carbon dioxyde need to be removed, but solutions to intake should double as exhaust here.
* Heat management
Probably the most critical, and often considered the biggest limiter in muscle strength for large organism, due to the square-cube law: muscle volume (and theoretically, strength, but also waste heat generation) goes up with the volume, while muscle surface (and its ability to evacuate waste heat) goes up with the surface. So the dragon will need an extremely efficient circulatory system to get rid of heat - you won't get much better than water, so you will have to pump more blood faster and through more vessels. This is both for heat and fuel intake, in fact, as fuel intake is also limited by surface.
Then, this heat will have to go somewhere. The aforementioned supercharger would help, but also the gigantic wings that a dragon needs to fly anyway, and that will make for nice radiators - wings must also grow larger due to the square-cube law. you can even have fun and have the supercharger pointed down, with its scalding hot exhaust a bit similar to a breadth weapon.
Increased perspiration through, especially through the supercharger, may be necessary. There could also be small cold nodules in the muscles to help get rid of heat during a brief, intense effort, though designing such biological system to be small and light enough may be a challenge.
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There will have to be a balance between impractically large wings (to better glide) and impractically powerful muscles (for powered flight), depending on how efficient those systems are and how strong dragon tissue is. Anyway, this may either require artificial design or a very unusual evolution, but those may help grow dragons just a bit larger. I suspect the dragon would only be capable of punctual intense effort to take flight, and then mostly glide, like the extinct Quetzalcoatlus mentioned in the answer of Klaus Æ. Mogensen.
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The dragon would have a very shallow and wide profile much like a manta ray but this might fit the question.
The up and down strokes of the wings will be very different than anything on earth.
If you had the shoulder girdle fused, with the upper wing bone with a very small range of motion, the muscles of the torso would work to torque the upper wing bone(our humorous bone), rotating the lower wing in your up and down motions(elbow to wrist), this portion of the wing will be short and stout compared to what we usually picture as a wing.
The vast majority of the wings surface area and lift power will be the "hand" much like a bat. Any thoughts and possible problems with this?
Btw a special system of tendons would likely be needed to transfer the great force down out to the wingtips to prevent your dragons light weight skeleton becoming pulverized.
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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/140903/edit)
I have the idea to have the engineer of a spaceship discover a "microfracture" in the ship's key structural framework (that was overlooked when prior battle damage was fixed) that has been slowly getting worse every time the ship "jumps" (you know, enters warp, FTL, crosses out of normal space, whatever you wanna call it). This means that the ship is stuck, and can no longer jump without risking the ship ripping itself apart. This microfracture was small and in a difficult to detect area, so the shipyard that fixed the ship didn't notice it, and even though it's gotten bigger, the only reason they found it was because the engineer is of a species that has heightened senses and noticed something off with the vibrations of the ship, especially during the last jump. I know I've given pretty basic details here, but does this sound plausible to you? And if not, what would make it work?
Edit: I should probably also mention that the ship's repairs were cut short. Half the weapons aren't even functional, for instance. Essentially, the people in charge decided that they couldn't spare a fully functioning warship for the task this crew gets sent on, so they rush the yard to just finish the "necessary" stuff, pull the ship out as soon as they can, and send it off understaffed. (yes, a terrible idea; yes, the ship's captain was furious). So this might help explain why the yard wasn't as thorough?
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# Yes and no
Yes because this is the story of the [de Havilland Comet](https://en.wikipedia.org/wiki/De_Havilland_Comet), the first commercial jet airliner. Fractures developed around the windows that caused it to crash and several did so before they managed to trace the problem.
No because sensing the vibrations is something that's done as a routine part of maintenance, even old steam engines had someone whose job it was to [tap all the wheels](https://en.wikipedia.org/wiki/Wheeltapper) to listen for fractures.
Some fluke event that causes them to discover this problem, yes, but not something that could be considered under routine maintenance like vibration testing or sensitivity.
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While I fully agree with Separatrix'answer, there's a wrinkle that I think is worth considering; scale.
If your ship is effectively some sort of small yacht or cargo carrier, like the space equivalent of a Ford Transit or Renault Trafic, then your engineer is far more likely to know the ship well and sense a vibration that could cause trouble.
If your ship is more like a massive cargo or personnel carrier, like the Exxon Valdez, then less so. This is not because the engineer's skill is lower, but simply because larger ships are going to have creaks and groans anyway, and identifying a creak that just happens to indicate a very small tear (which is now a MUCH lower percentage of the size of the ship) from the more conventional noises of microshifts in the structure is going to be much more difficult.
So, I'd argue that one of the key probability factors in being able to sell the plausibility of what you're describing would in fact be the size of the ship itself.
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**Have the ship rip itself apart.**
Being afraid something might break is kind of a wuss reason to be stranded. Having it dramatically break is a great reason to be stranded. They jump and their FTL drive keeps going. The ship falls out of hyperspace, minus the drive and some other parts.
You can have the engineer be sensitive. You can have the engineer warn the captain about the consequences of the micro fracture. "The ship canna take it, Captain!". Except the engineer is right.
Not your question, but I envision the engineer disappearing with the FTL drive and most of engineering when the ship breaks apart. If you need your stranded characters rescued, the engineer can show up at the end of the story with a ship it has built around the FTL drive.
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Make it a micro fracture in the hyperdrive itself.
More specifically, make it a fracture in the mountings for one of the MacGuffin arrays (Named for engineer Michael MacGuffin, inventor of the Hyperspace Stabilisation Equations)
The fracture is tiny at first. Completely irrelevant to the operation of the ship. With each jump, though, the fracture widens, pushing the MacGuffin array further and further out of alignment until it's almost outside its design tolerances. After the last jump it *is* outside its tolerances, and any further attempt to jump without a brand new set of MacGuffin array mountings *will* result in the ships destruction.
Luckily for you one of your engineers has superpowers and can detect this misalignment simply by being close enough to the hyperdrive during the last jump. He picks up on it and one thorough drive diagnostic (involving several labour intensive manual checks and dismantling parts of the hyperdrive) later it is discovered that the MacGuffin array is now well outside of tolerance, and it's just blind luck that the ship made it this far.
"But why wasn't this picked up in the shipyard?" I hear you cry.
There are two reasons that work together:
1: That kind of drive check is hard to do, since it requires dismantling and then reconstructing the hyperdrive.
2: This kind of fault is the kind of fault that generally just blows up the ship on the first try, since it's very rare for misaligned MacGuffin arrays to be out by such a small amount that a jump can still be completed successfully.
With both those points in mind: Why would a rushed repair and refit job bother diverting resources to run a drive diagnostic on a drive that clearly worked well enough to get the ship to the shipyard?
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My story takes place hundreds of years in the future after global warming has made life at the surface uninhabitable for most life forms. What’s left of mankind survived because it became popular to build cities underwater before things at the surface became dire.
Obviously these cities would have to be self sustaining in order for humanity to survive. I envision them growing food in hydroponic pods, raising livestock, using 3D printers, desalination equipment for a water source.
I would like some of these cities to be more advanced than others because they discovered ways to make new infrastructure and technological advances while stuck underwater.
I’m not writing hard core science fiction but I don’t want the infrastructure and technology to sound like complete fantasy. Is it possible for humans to build a completely sustainable city underwater if money was no issue?
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Soan's answer raises some really good questions that deserve answers. I was gonna make this a comment but it got way too long; so, full credit to him for what variables to consider.
The ideal place to build cities would be on the continental shelf within a few kilometers of the shore. While this would not put it in still water, there are many logistical reasons to do it this way. First is that these cities are built by land dwelling people; so, the closer they are to these now defunct infrastructures, the easier they are to build. Secondly, is that if you try to build past the shelf, you would be building on a cliff side of the continental slope which would be much more risky in the case of erosion, and the abyssal plane is way past the crush depth of modern submarines (that have large enough of interiors to support long term life). Apart from being at non-crushing depths, this also ties into the power grid issue because you could build hydro turbine power farms around your city to harness the tidal current of the continental shelf.
For building materials, you could replace steel with aluminum. Unlike iron alloys, when aluminum oxidizes, it becomes stronger; so, structures made out of it would be able to last for centuries under water. There is also the option of using portland cement to make concrete structures that cure underwater. While not as watertight as aluminum, this would solve your erosion issues. By planting your aluminum structures in heavy, porus, concrete foundations, your foundation would become overgrown and built up with coral faster than it erodes. As for structural shapes, while a dome (or sphere) is an ideal shape for underwater construction, you are likely picturing a giant glass dome but that creates a lot of seams and structural issues. The most logical configuration would be a series of hundreds of modular, interconnected, submarine like structures with plain metal or polymer exteriors, concrete bases, and minimal portholes and waterlocks.
While things would grow all over your exterior (bacteria, coral, barnacles, etc.) it would not make for any hernderance to survivability. Over-time, your city may be completely buried by sediment and coral, but things that are often used like water locks for your mining subs or outlets for bilge pumps would be be used often enough that they would stay clear with occasional maintenance
As for temperature, the average depth of the shelf is ~140 m (450ft), but only the top 100m of the ocean are particularly affected by surface whether. At 150m, the temperature does not vary nearly as much; so, where on the land might see an 80deg variance throughout the year, at this depth, your variance would be so much smaller that it may always be a bit warm, but you would not see fatal heat waves like on the surface. Also, photosynthesis is possible at depths of up to 200m, meaning you can farm with sunlight at this depth (though probably using specialized low-light crops or seaweed farming).
If you want to make "advanced" civilizations; you could have them build in the deeper waters in the Abysmal plane. Instead of hydro-turbine power, they could harness geothermal power and mine the exposed bedrock of the continental rise giving them access to vastly more power and resources. Their structures would be similar in shape and layout but be made from much more advanced materials like graphene laminates to be able to endure the greater pressures.
As far as plot hooks, it's pretty easy to see how superstitions and mistrust would build overtime between the high-born people who live in the light of the sun, and the low-born people who live in the total darkness of the abyss.
**[edit]**
As for industrialization, unlike a space station, these colonies have the option of building "smoke stacks" that lead up to the atmosphere. This means that you could pipe in the Oxygen needed for your smelting equipment. While this air may be toxic and rather hot, it would still be suitable in a closed system for doing all the industrial things you can do with an abundant atmosphere on the surface.
This also means when mining or expanding structures, you can just pipe in more air to fill the new spaces after cooling, filtering, and compressing it.
With this in mind, I suspect mining would look one of three ways depending on the resource. One type would involve making a waterlock a little bit away from your city that just leads to a tunnel going down deep enough into the bedrock to make for a mostly airtight seal. Then you would use bilge pumps to clear any water that drips through and fill the tunnel with air conditioned surface air as you expand it. The second type of mining would be for the silicates and diatoms that make the actual sea bed which would probably just be shoveled up by specialed submarines. The third type would be for things that you have to return to the surface for. For this people may need to go back to land in what basically look like EVA suits to mine for things that may only accumulate under non-sea bed conditions or to recycle rare pre-fall materials that they can not manufacture with their limited surviving tech.
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Yes it would be possible.
**Things to consider though:**
* These cities would need to be built in an area where the water
doesn't move much because of erosion.
* Also most metal constructs would degrade within decades/ bit more
than a century [like the titanic](https://news.nationalgeographic.com/news/2010/08/100818-titanic-3-d-expedition-shipwreck-science-collapsing/). Extensive and regular cleaning
might keep metal constructs viable for a few centuries. Building with
rocks would be another solution.
* Also micro bacteria would probably infest everything exposed to the
ocean.
* Depending on the heat on the surface temperature your cities would
need to be deep within the oceans. So the high pressure needs to be
dealt with a dome enclosing the cities could do the trick but the
dome would need to be very thick depending on the deepness of your
cities. With the dome you could also deal with all of the micro
bacteria as it would only infest the dome.
* Power generation. You could use differences in heat (warm air or water from the surface and cold water from around your city) to create a heat exchanger when your cities are deep enough they could use the heat from the [earth crust](https://www.universetoday.com/65631/what-is-the-temperature-of-the-earths-crust/). They would need to do a bit of drilling to get away from the water cooled part of the crust and into the heated part. You could also use under water currents your cities should still stay away from them for longevity but with a long cable to your cities it should be fine.
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Don't try to grow land based plants and animals, the ocean is already very abundant in these.
Windmills and solar panels could still just out above the city, but you could also harness waves.
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There are some organisms that can generate electricity (eels, for example). And some others can detect magnetic fields and use it for navigation (birds, for example):
<https://www.nytimes.com/2012/04/27/science/study-sheds-light-on-how-pigeons-navigate-by-magnetic-field.html>
But, is it possible for an organic entity to generate a **steady magnetic field** somehow by means of organic functions?
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Yes. All the time.
Creatures regularly use bioelectrical fields within their bodies. Cells can pump ions into and out of tissues using energy. These ions are charged, and their movements produce electrical charge. If there is steady movement of ions from one area to another, an electrical current is formed. A example is the electrical field formed when a wound happens.
<https://en.wikipedia.org/wiki/Bioelectricity#Role_in_wound_healing_and_cell_guidance>
>
> How are the electric fields at a wound produced? Epithelia actively
> pump and differentially segregate ions. In the cornea epithelium, for
> example, Na+ and K+ are transported inwards from tear fluid to
> extracellular fluid, and Cl− is transported out of the extracellular
> fluid into the tear fluid. The epithelial cells are connected by tight
> junctions, forming the major electrical resistive barrier, and thus
> establishing an electrical gradient across the epithelium – the
> transepithelial potential (TEP).[129][130] Breaking the epithelial
> barrier, as occurs in any wounds, creates a hole that breaches the
> high electrical resistance established by the tight junctions in the
> epithelial sheet, short-circuiting the epithelium locally. The TEP
> therefore drops to zero at the wound. However, normal ion transport
> continues in unwounded epithelial cells beyond the wound edge
> (typically <1 mm away), driving positive charge flow out of the wound
> and establishing a steady, laterally-oriented electric field (EF) with
> the cathode at the wound. Skin also generates a TEP, and when a skin
> wound is made, similar wound electric currents and fields arise, until
> the epithelial barrier function recovers to terminate the
> short-circuit at the wound.
>
>
>
Any electrical current will generate a magnetic field.
[](https://i.stack.imgur.com/2Cj7K.png)\
<http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/Biosav.html>
So bioelectric currents will produce magnetic fields around them.
[Answer]
Is it possible for an organic species to generate a steady magnetic field?
[Hemochromatosis:](https://www.hemochromatosis.org/#overview)
>
> The human body cannot rid itself of extra iron. Over time, these
> excesses build up in major organs such as the heart, liver, pancreas,
> joints, and pituitary.
>
>
>
Iron is [ferromagnetic](https://en.wikipedia.org/wiki/Ferromagnetism) in it's metalic elemental state
>
> is the basic mechanism by which certain materials (such as iron or iron oxides) form
> permanent magnets, or are attracted to magnets.
>
>
>
Therefore:
>
> Skin color changes (normaly noted as hyperpigmentation in the condition): Deposits of iron (compounds) in skin cells can make your skin
> appear bronze or gray in color.
>
>
>
But can magnets [lose their attraction](https://en.wikipedia.org/wiki/Ferromagnetism#Magnetized_materials)? Yes, but:
>
> it is metastable, and can persist for long periods, as shown by
> samples of [magnetite](https://en.wikipedia.org/wiki/Magnetite) from the sea floor which have maintained their
> magnetization for millions of years.
>
>
>
As far as I can find, there is no current example of a magnetised organism (or organism which emits no electromagnetism) existing. But if somehow hemochromatosis, and increased skin pigments of magnetic material were to be advantageous to survival and reproductive success, then yes, it would be possible that such an organism could evolve, over sufficient time.
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<https://physics.stackexchange.com/questions/4637/electromagnetic-fields-vs-electromagnetic-radiation>
I would also add that in theory if an animal lives in an iron rich environment, eats iron or manganese or nickel or something and also has charged ions around it, from lightning storm, etc. it is possible for such a ‘moving’ body to create a magnetic field.
You also might want to consider radiactive elements and static electricity.
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First question so go easy! I've been looking around for the carrying capacity of Elephants, hoping to extrapolate that to a Woolly or Columbian Mammoth. I know logging Indian elephants can lift half a ton with their trunks, and I know historical War Elephants (typically Indian) wore armor and carried small defensive structures on their backs, but I'm struggling to find specifics.
Does it at least seem plausible that a Columbian mammoth (twice an Indian elephant's weight) could bear armor effective against most hand held ballistic weapons? Crafted from salvaged human bulletproof vests, say, made of Kevlar and ballistic ceramic plating. How many armed men seems like a reasonable cap on an 11 ton mammoth? This hypothetical takes place in a post-apocalyptic Ice-age environment, with limited fossil fuels and airpower.
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**Don't think of your mammoth squad as armour. Think of them as tactical transport.**
The problem you are hitting here is that a mammoth is like a tank in only the worst way - it is the most attractive target on the battlefield if you have heavy weapons. Unfortunately the mammoth has none of the advantages of a tank - it does not have:
* a low silhouette,
* angled plates of thick armour to deflect heavy weapons projectiles,
* stabilised heavy weapons
* protected compartments for the crew.
Taking a look at the Wikipedia article on [mammoths](https://en.wikipedia.org/wiki/Mammoth) a wild guess would be that a reversed "cloak" of barding that covered the front, top and sides of an 11 ton mammoth would require about 48 square metres of ballistic material. To achieve even moderate protection against minor fragments and small calibre rounds the article on [body armour](https://en.wikipedia.org/wiki/Body_armor) uses an example of 5.4 kg/sq m. So there goes about 260 kg of offensive payload. If the barding is going to give second chances against heavier rifle rounds, this needs to be doubled, at least. Now half a ton of offensive payload, or about 4 fully equipped troops, is lost, but the mammoth is still vulnerable to heavy weapons or multiple hits in the same spot. If the howdah (thank you AlexP) on the back of the mammoth is armoured to protect the troops then more weight is lost. With this much carrying capacity dedicated to armour, plus the weight of a driver, the mammoth can probably manage two armed troopers. The troopers would be limited to light weapons on even the best trained mammoth - 40mm grenade launchers would be my recommendation, used to designate targets from their elevated (and very exposed) place on the battlefield.
Now the situation is this - a mammoth with a terrified driver and a brace of grenadiers, struggling under the maximum weight it is able to carry, will attempt to to charge troops equipped with modern firearms. The outcome would be depressingly predictable and a reminder of why horses and elephants are not used to conduct charges any more.
**A better option**
However, the noble mammoth *does* have a place on the post-apocalyptic Ice Age battlefield. It grants tactical mobility to move larger loads than can be transported by human muscle-power alone. *Provided they can forage,* mammoths can pull sleds through the snow very efficiently. (If they can't forage then they are of very limited use, as much of their capacity will be required to carry their own food.) Assuming that a mammoth can tow a 2 ton sled over level ground, a couple of mammoths can be used as a means of transporting a mortar platoon's equipment (for example) into position quite efficiently and tethered some distance away while the platoon is firing missions. In short, they are far more valuable as a transport asset than as a front-line combat asset.
If you really want a mammoth charge in your story then it should be an encounter battle. One probable advantage of mammoths would be relatively quiet movement. Scenario could be that a body of troops are moving in a column (with the mammoths in the middle) through a wooded area. Enemy troops emerge on one flank at close range in an unplanned encounter. The troops friendly to the mammoths open fire first, this panics the mammoths into charging towards the slow-reacting enemy. With a short distance to cover and effective suppressive fire from their allies the mammoths could get in close and do some damage. (It would bring a new meaning to "stepped on" when referring to confirmed enemy kills.)
And if things go pear-shaped, a mammoth will feed a lot of troops for a long time in cold weather.
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You have some misconception here. While body armors CAN protect your animal from being hurt seriously, you have to consider the following.
1. **Temperature**: you're wholly mammoths are hairy, for the reason that they needed it due to cold weather conditions. Covering them with armor will increase their body heat, and if they don't cool for sometime, they will die of dehydration or heat stroke. You haven't given us the information about the climate of your post apocalyptic era, but its safe to say that, you should not be using your mammoths in summer.
2. **Psychology**: different humans, different animals. Yes, soldiers are trained to hold their grounds during fights, but have you even asked these soldiers if they where scared when under fire? I assure you, even war veterans will tell you that, they will run from that fight if they could. Because we have lots to lose from death by war, but less to gain from it. Now enter an animals mind, he does not need money, nor fame, nothing, he only has his life. Do you think he will be stampeding towards the enemy on the first shot? Your animal will save himself **INSTINCLY** because he knows he only has one life. F\*\*\* human orders.
3. **Exlosives**: Modern human best friend in war. Yes, we love it, explosives do short work on anything our enemies throw at us. Incoming tank? BOMB! A whole lot of infantry? BOMB! Your ex GF? BOMB! A cool looking enemy mammoth parade? BOMB! From missiles to land mines to hand held grenades and IEDs, humans will try to create bombs no matter what, because as I have said. Short work.
4. **A Whole lot of armor**: So lets say you have negated heat, Psychology and Bombs in your story, you'll be giving too much armor for an animal which if you just used them for your infantry, would be more cost efficient, a fully armored wholly mammoth might have covered 10 or 20 Infantry men that are more mobile, more versatile, and more intelligent (and a whole lot of plenty) than your mammoth.
In conclusion, I would really like to suggest that you put your mammoths in parks where kids could see them and maybe ride them, best give your humans their armors and do what they have to do.
BUT if your really really want your mammoth squad in your story? Best switch to medieval setting.
[Answer]
I note that there were many different species of mammoths. You would prefer one of the largest species for a fighting war mammoth. Different species of mammoths lived in different climates. Not all mammoths lived in snow covered regions.
Because most species of mammoths have tusks that curved a lot, most mammoth tusks were almost useless for stabbing. Thus it is often claimed that mammoth tusks were useless as weapons. But it seems to me that mammoth tusks would be terrifying war clubs.
So suppose that your battle involves two phalanxes of spear men facing each other. But one phalanx has several gaps in it. War mammoths stride through the gaps to reach the enemy phalanx.
Each war mammoth pushes the spears facing him to one side with a swing of his neck, head and tusks, steps forward and swings his head and tusks again, sweeping a bunch of men out of his way with many broken bones. The war mammoths step forward and sweep their tusks again, smashing away men deeper into the phalanx.
They are followed by sword men who attack the spear men at the sides of the paths the war mammoths cut through the enemy phalanx. The mammoths smash their way through to the back of the enemy phalanx and turn around to attack the undefended back of the phalanx. Etc., etc., etc.
So war mammoths would be very effective against pre-gunpowder opponents. And they would be useful against armies using primitive black powder firearms. Some war elephants have carried machines guns or cannons.
[Answer]
I'm going to make quite a few assumptions, and include a significant disclaimer to my answer.
First, the disclaimer: I will not list a practical carrying weight, or even an estimate of such, as I lack the mathematical skill and biology background to attempt that. But I believe I can contribute to the question anyway. [Possibly useful comparisons here.](https://en.wikipedia.org/wiki/Pack_animal#Load_carrying_capacity)
Now the assumptions:
1. "Hand held" I understand this to mean something intentionally designed to be primarily carried and used by a single person, as opposed to just anything someone can manage to pick up (like removing a mini-gun from a helicopter or a 50 caliber from a hum-v, etc).
2. "post apocalyptic" In any scenario I can imagine that could be termed an apocalypse, any militaries that were not immediately wiped out would be very active immediately following the event, and would therefore be actively using their resources, including weapons and ammo. So 'post' apocalypse, the amounts of specialized military equipment available, including more unusual firearms variations and the accompanying ammo (heavy caliber, tracer, armor piercing, etc.), would be negligible. This leaves only the weapon and ammo types that are available to either civilians or the 'run-of-the-mill' 'grunt' soldier, so something on the scale of a big-ish hunting rifle (or military equivalent) is about the most dangerous the mammoth would face.
3. "anything an elephant can do a mammoth can do better" at least as far as the desired information for this question is concerned.
4. "could be of a different temperament and intellect than the historical species" (from comments) To me this means my answer can disregard the animals' reactions to the chaos of battle as unrelated to the question and as a topic to be addressed by the OP some other way.
Now, there is a reason that "elephant guns" were called ... "elephant guns". Elephants don't go down easy (compared to most other animals), even with no armor at all. Granted that weapons technology has improved since the era of elephant gun use, modern hunting rifles can still have trouble with knocking down something as small as a deer with a poorly placed shot. And even a (eventually) fatal shot on a deer can leave it alive long enough to run for miles before collapsing. Accounts tell of elephants taking up to 35 rounds before going down, again with no armor at all.
So, a Mammoth would (theoretically) be even more resistant and durable, even without armor. The weapons it would be facing would not be specialized to the point of significantly overriding it's natural defenses (even a few well placed, body mass, but not brain or heart, shots on an unarmored Mammoth will not bring it down, and it may even make an effectively full recovery). So additional armor, such as salvaged Kevlar vests, would certainly help, but would not need to be particularly highly defensive by themselves. Rather they would complement the Mammoth's already significant defense. What would protect a human from only the smallest and slowest of calibers, on a mammoth would make the smallest and slowest rounds a non-issue (other than things like shooting out the eyes), it would turn medium 'level' rounds from a flesh wound in to a bruise or pinprick, and it would turn injuries from heavier calibers like hunting and assault rifles from severe internal trauma in to a graze.
So the armor intended to protect the mammoth itself would not need to be of (relatively) significant weight. If carrying a structure meant to protect driver and passengers, the armor there would be the heaviest weight requirement other than the passengers themselves (I imagine mounting the remains of an armored military vehicle, like a hum-v, on it's back). If an elephant can carry the weight of just the visible bodywork of a normal car and passengers, then a similarly structured animal should be able to carry just the armor portions (no motor, drive-train, wheels/axles, or other unnecessary heavy components) of a small derelict military troop carrier originally built with plenty-enough armor to withstand most small weapons discussed here.
And there you have it, no exactly defined weight, but certainly an answer to "is it plausible", and some useful points to consider along with it.
]
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[Question]
[
This is the premise: the occupants of a spaceship die hundreds of millions of years in the past orbiting above a Earth-sized planet. It has a supercomputer that allows the ship to still fire its rockets if it detects even slight orbital decay. The ship has enough power (i.e., a megaton neutron reactor, generating 7.50x10^13 joules of energy per kilogram) to sustain its orbit and to power its machines.
However, when the occupants died, the organisms that live on them didn't die. So, now when the bacteria-analogues evolved for hundreds of millions of years into metazoa and all the machinery has rusted except for the rockets, would the ship still stay intact?
I'm asking if the spaceship will stay intact under the radiation of the extreme proximity of a white subgiant star (maybe an F0IV or something like that), stellar wind, interplanetary particles, and cosmic radiation, if that clears it up. I gave the information about the metazoa for background.
The neutron generator works on beta radiation so electrons and protons come out of the rockets. Whatever energy is not used for powering the ship is not drawn from the electrons and so let them fly out of the rocket unhindered. It does not generate neutrons; it generates electricity from beta decay. Once a neutron decays, the electron is launched out of the neutron core. This would mean that when the core decays completely, the products would be a proton core, which would cause the ship to explode because there are too few neutrons. This won't happen anytime in the near future. I found the energy density of neutronium by the mass of a free neutron and the energy that the electron has once it undergoes beta decay.
The atmosphere would be nitrogen dioxide.
Instead of using beta decay, would it be better if I use metallic hydrogen and rely on that to recombine to provide electricity and use something like hydrogen peroxide as propellant?
[Answer]
Power is necessary but not sufficient, since the purpose of the power (technically the energy) is to propel mass in the "opposite" direction.
Thus, the amount of time your derelict spaceship stays in orbit is based on:
1. the amount of mass in it's altitude control motors, and
2. the initial altitude.
The higher the orbit, the longer it will stay in orbit. Specifically, if it's significantly above 26,200 miles, then it could last for a **long** time.
If you're asking how long before the ship falls apart, that all depends on how durably it's constructed, if it's got "anti-meteor lasers" (hey, it's sci fi!) and whether it's lucky enough to not get hit by something Really Big.
As for whether it could maintain structural integrity for as long as you ask... well, **trees** are only **370 million years old**. In other words, "hundreds of millions of years in the past" is a **Really Long Time**.
But... it's your story. Just *say* it's that old, make some comments about how beat up it is and that "they don't make 'em like that any more!", then continue with your story. Readers will accept that.
]
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[Question]
[
My **Calisota**, which is located [in the north of what we know as California](https://upload.wikimedia.org/wikipedia/commons/thumb/0/01/Calisota_location.png/220px-Calisota_location.png) and largely resembles the universe seen in German-language Disney comics (Lustiges Taschenbuch), except for the absence of anthropomorphic animals and the presence of humans in turn, largely speaks German due to the German heritage of the majority of the population. Being a melting pot of cultures, Calisota will likely have a strongly americanized vernacular dialect.
My question is:
* To what extent and how will a.) the dialect of Calisota and b.) its Standard German Language be influenced by American English and others? To what extent will it likely diverge from Standard German over the course of the existence of Calisota and Duckburg? Which non-German words and phrases are most likely to enter it?
Take into account that:
* Calisota was first sighted by English and Spanish explorers in the late 16th century.
* During the course of the 17th century, German settlers, mostly from Rhineland, arrived and constructed a wooden fort.
* The city-sized colony became a medium settlement and most likely acclaimed a fairly large territory by the 19th century. There was a further influx of German settlers, but also of settlers from the eastern USA and Scotland (Scrooge McDuck). A small minority of fanatics from Deseret seeking religious freedom also moved to Duckburg.
* Calisota most likely fought small wars with the USA and successfully prevented it from absorbing it.
* During WWII, German Americans and Canadians, mostly from Pennsylvania and Ohio (Pennsylvania Dutch), fled to Calisota, which stayed neutral, in fear of repressions.
* In the late 20th century, Germans still stayed the main immigrant group as the number of new settlers decreased.
[Answer]
[Wikipedia on Pennsylvania Dutch](https://en.wikipedia.org/wiki/Pennsylvania_German_language#Adoption_of_English_vocabulary) is the German spoken by persons from insular communities whose immigrant ancestors spoke German.
>
> Adoption of English vocabulary
>
>
> The people from southern Germany, eastern France and Switzerland, from
> whom the Pennsylvania German culture and dialect sprang, started to
> arrive in America in the late 17th and early 18th centuries, before
> the beginning of the Industrial Revolution. To a more limited extent, this is also true of a second wave of immigration in
> the mid-19th century, which came from the same regions, but settled
> more frequently in Ohio, Indiana and other parts of the
> Midwest. Thus, an entire industrial vocabulary
> relating to electricity, machinery and modern farming implements has
> naturally been borrowed from the English.
>
>
>
> >
> > Numerous English words have been borrowed and adapted for use in
> > Pennsylvania German since the first generations of Pennsylvania German
> > habitation of southeastern Pennsylvania. Examples of English loan
> > words that are relatively common are "bet" (Ich bet, du kannscht
> > Deitsch schwetze = I bet you can speak Pennsylvania German), "depend"
> > (Es dependt en wennig, waer du bischt = it depends somewhat on who you
> > are); tschaepp for "chap" or "guy"; and tschumbe for "to jump". Today,
> > many speakers will use Pennsylvania German words for the smaller
> > numerals and English for larger and more complicated numbers, like
> > $27,599.
> >
> >
> >
>
>
>
Easier though if you are writing in English for English readers would be [**Pennsylvania Dutch English**](https://en.wikipedia.org/wiki/Pennsylvania_Dutch_English); an English cake with German icing. There are great turns of phrase which are easy to understand for English speakers but clearly influenced from German.
>
> Make wet? = Is it going to rain? Outen the lights. = Turn off the
> lights. The candy is all. = There is no more candy. Don't eat
> yourself full. = Don't fill yourself up. There's cake back yet. =
> There is cake to come. It wonders me. = It makes me wonder.
>
>
>
I love "Outen"!
[Answer]
>
> To what extent will it likely diverge from Standard German over the course of the existence of Calisota and Duckburg?
>
>
>
Very, *very* much! There are not many German speaking countries around because the Germans didn't have many colonies, but if you take someone from Germany and put them into Switzerland or Austria, they will not understand the local dialect unless the locals take pains to speak slowly and clearly. It's even enough to take someone from the north of Germany and someone from the south and they *will not understand each other*. The reasons lie in the history of Germany as an accumulation of more than 300 kingdoms and principalities, each with their own local dialect.
A real-world example is German South West Africa (nowadays Namibia), which was a colony of the German Empire from 1884 until 1919. The local dialect resembles Low German (or Plattdeutsch), a dialect only spoken around the coast and on the islands of the north sea. The regular German tourist in Namibia doesn't understand a word.
---
>
> To what extent and how will a.) the dialect of Calisota and b.) its Standard German Language be influenced by American English and others? Which non-German words and phrases are most likely to enter it?
>
>
>
As it is, words and names for new technologies are commonly assimilated into the German language (called Anglizismen). Every-day examples include: internet, laser, smartphone, Googeln (to google), laptop, computer, tablet [computer], streaming, fast food, disco and so on, and so forth. Here's a list of [English words used in German](https://de.wiktionary.org/wiki/Verzeichnis:Deutsch/Anglizismen) (please note that some of them are more like slang).
A few decades ago, there was a custom of creating German names by writing English names in a typical German way (called Eindeutschungen). Examples are Telegraf, Telefon, Technik (technology), Keks (caces), Scheck (cheque), Streik (strike) and Schal (shawl). If the Calisotans wanted to make a statement how much they differ from their English speaking neighbors, they would have more such adaptations in their current dialect.
In recent years, even things that *have* German names are commonly substituted with English terms (called Anglizismen). Most notably are things like exit, workflow, info point, deadline, flyer, flatrate, meeting, sale. For a while, it was simply "in" to use english terms. If the Calisotans relationship with their English speaking neighbors were quite friendly, similar assimilations could have taken place.
---
Another notable difference is that Calisota would probably use the metric system.
]
|
[Question]
[
The most recent common ancestor of the HIV-1 M group, responsible for the HIV pandemic, dates back to the Belgian Congo city of Léopoldville (modern Kinshasa), circa 1910. And the genetic history of the virus indicates that there have been several separate "jumps" of the virus from the simian version, SIV, dating back to possibly as far back as 1884, though evidence suggests that the true date is somewhere between 1908 and 1924. Bearing this in mind, I'd argue that we're definitely far closer to the best case scenario than the worse case scenario when it comes to HIV.
So, let's imagine this- instead of spreading from Kinshasa and being transmitted outside of West-Central Africa for the first time in 1952, as in our timeline, let's say that in a different timeline, a sexually prolific European picks up the virus from frequenting a brothel in Leopoldville in the early 1910s, then travels back to Europe to fight in WW1 on the Western Front, carrying it back to the military brothels there.
In our timeline, an estimated 20-30% of the entire population of Europe (including civilians) had been infected with syphilis by the end of WW1, with the STD transmitted to the population via these brothels and those who frequented them- a similar or even greater percentage of the population (once we add unsterile injections by medics and doctors to the mix, along with blood transmission), as much as a third of the total population, could have easily contracted HIV if it had spread from this timeline's 'patient zero' across Europe during WW1. And with anti retro-viral drugs still more than 70 years away, HIV had an 80-90% mortality rate.
Now, let's compare this scenario to the 1918 flu pandemic. That also infected roughly a third of the world population; however, it only had a mortality rate of 10-20%, 4-8 times lower than that of HIV. In other words, you'd have been looking at a projected death toll for this timeline's WW1 HIV pandemic which would be projected to be 4-8 times higher than that of the 1918 flu pandemic- and even worse, you'd have both pandemics coinciding with one another and spreading at the exact same time.
In our timeline's 1918 flu pandemic, current estimates say 50-100 million people worldwide were killed, 3% to 6% of the entire world population. In this timeline though, in the worst case scenario, even if we assume that both pandemics have no impact upon each other (i.e, that no extra people are affected compared to our timeline's flu pandemic, that HIV doesn't exacerbate the mortality rate of Spanish Flu and vice-versa), the death toll would be projected to be between 200-800 million people worldwide; 12% to 48% of the entire world population.
To put that into perspective, the realistic mid-estimate for the death toll of this worst-case scenario alternate HIV pandemic, 24% of the world population killed within 3 years (the maximum life expectancy for those infected with HIV, with no treatment available at this early stage), would be equivalent to, or worse than, the reduction of the world population by the Black Death pandemics over the course of more than a century.
So would this earlier HIV pandemic have constituted a plausible, hard-science historical apocalypse scenario? And what sort of dystopian post-apocalyptic societies would you envision developing in this timeline? Our timeline's Fascists and Communists were bad enough; how much worse might this timeline's equivalents wind up being?
[Answer]
It may looks strange, but HIV is, in this regard, less efficient than flu.
Flu is airborne: it is perfect for a rapid spread in a world where ships could still carry large amounts of people fast enough from point A to point B and happily spread toaward unsuspecting targets. And once it gets a hold of its target, symptoms rapidly incapacitate it.
HIV requires direct blood exchange: in this regard is not worse than other venereal diseases. It will kill a lot of people, like those diseases did, but since it is slower in acting, once symptoms are visible on the body, medics and authorities can start tracking it down to the closest to patient zero. Triage and precautions can be refined and applied better than with flu, which is also a mutant and can hit again regardless of precautions -that is why we need to vaccinate, to keep it at bay from the weakest targets (sick people, elders, kids and babies)
So no, **the answer is**: HIV wouldn't change a thing unless all soldiers on all fronts had had sex with infected people, coincidentially in the right time frame so that at the end WWI they got sick with AIDS as well
In regard to the Fascism, once it has been determined that sexual contact is directly involved, it will cause authorities to push for stricter laws regarding monogamy and racial purity, but the whole legal corpus would be unaffected for what the general fascist philosphy is concerned.
[Answer]
**Mass HIV infection did not cause a population crash in pre-HAART subsaharan Africa.**
The scenario you posit really happened and is happening in subsaharan Africa. Botswana has the third highest prevalence of HIV of any country and is the biggest of the top 3. 21.9% of the population is HIV+ and that has been fairly constant since 2000.
<http://www.unaids.org/en/regionscountries/countries/botswana/>
[](https://i.stack.imgur.com/hjN0q.jpg)
The problem for your mass dying scenario is that HIV really is very much like syphilis in Western Europe. It is not that lethal. A lot of people have it but not that many die. Considering pre-HAART rates, about 3-5% of persons with HIV die of it in any given year. Check out the unaids website liked above; it is a very nice interface for viewing the data.
[](https://i.stack.imgur.com/AEOPR.jpg)
This projection from 2000 noted that in the best case scenario, population growth in Botswana would just barely stay positive.
<http://www.undp.org/content/dam/botswana/docs/Old%20Publications/BotsDemogrepFinal.pdf>
>
> Botswana total population growth is declining rapidly due to HIV/AIDS.
> Only in the best case (S2) will growth remain positive (at 0.2%) by
> 2010. By 2010 the total population is projected to be between 1,53 million (S1) and 1.72 million (S2) • HIV/AIDS will profoundly alter
> the population age profile. The greatest reduction in numbers compared
> to a no-AIDS scenario by 2010 will be among adults aged 35-45 (a 40%-
> 50% reduction) and children aged 0-9 years (32-40% lower). • Under-5
> and infant mortality will both increase. Under-5 mortality is expected
> to be 67-98/1000 higher than in a no-ADS scenario by 2005. The IMR
> will be 20-25/1000 higher than in a no-AIDS scenario in 2000, rising
> to a 24-33/1000 increase by 2005.. • Life expectancy is falling
> dramatically. It is projected to be only around half (46-52%) of
> no-AIDS scenario levels in 2010.
>
>
>
This best case came to pass. Population growth dropped but stayed positive in countries hit hard by HIV.
[](https://i.stack.imgur.com/8oBOE.jpg)
[population growth data for selected African countries](https://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_pop_grow&hl=en&dl=en#!ctype=l&strail=false&bcs=d&nselm=h&met_y=sp_pop_grow&scale_y=lin&ind_y=false&rdim=region&idim=country:BWA:LSO:SWZ&ifdim=region&hl=en_US&dl=en&ind=false)
Positive population growth in this resource poor time and place means to me that your HIV scenario for Western Europe would not cause a plague like dieoff of the populace. HIV is like any other chronic endemic disease - like syphilis, or tuberculosis, or malaria.
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