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[Question]
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I've been going back and forth on my modern setting's magic system for a while now, but I've settled on a power-set that's closer to psychic powers than traditional magic, because of a couple of reasons:
* It's closer to my theme (the source of "magic" in this world is basically a psychic field generated by humans to protect them from invading creatures from other dimensions, with "mages" being humanity's white blood cells);
* It has more natural and obvious limitations (I always feel like open-ended magic systems like the Dresden Files are awesome but whenever I start to write them I'm boggled by the sheer possibilities for spells - like, where is the natural stopping point? If there's a spell for fireballs, why not flight? etc.).
Now, here's the thing though - I think it would be fun to be able to justify pyrokinesis / cryokinesis, because it's always fun to have an offensive power-set, right? Something for people to fling around and do damage with.
The problem is, those powers have never really felt like they naturally belong in the psychic power-set to me. I can't quite articulate why, but I feel like they stretch belief in a way telekinesis for example doesn't? Or perhaps are just not on theme? Is that just me?
In any case I would like to come up with a reason why they work. I've been reading up a bit on how fire works and I've read the pseudo-science explanation on pyrokinesis (it's about exciting the atoms in an object to ignite it), so what I was thinking is doing an huge handwave-y leap. Something like "They need something to ignite, but once they've done that they can manipulate the fire using air, like a fire whirl."
Does anyone feel like this works? Would you be willing to suspend disbelief if you saw this in a story, or is there a better way to think about it?
Thanks in advance!
[Answer]
In the tabletop RPG system G.U.R.P.S., pyrokinesis is included as a subset of telekinesis. According to the author, Steve Jackson (yes, the guy from the Munchkin game), this is using telekinectic power to make molecules vibrate faster instead of moving them from one place to another.
Do that in reverse and you have cryokinesis. A similar form of cryokinesis is seen in the animé *Saint Seiya* (*Knights of the Zodiac* in some countries), where characters with ice-based powers lower the temperature of objects by reducing the vibration of molecules.
[Answer]
I'll put this here to summarize things: The explanation of particle vibrations is as good as any from an in-universe attempt to explain things. However, you should think hard about how such an ability expresses itself so as to avoid issues in regards to what the characters can do, due to the vast amount of things one could do with such an ability as-is outside of creating/manipulating fire or ice/cold.
When it comes to Telekinesis, for example, different depictions vary wildly in regards to what they are capable of and what their limits are:
From characters that can lift a city's worth of material with their eyes closed, to those who can assasinate people by cutting off their arteries from afar, to those who can accelerate a grain of sand to hypersonic speed near instantly. Or, on the other end, those who can't use their TK on people and can barely life more than 100 pounds.
That said, I believe it depends on how far you are willing to extend the definition of "Psychic" powers. After all, from a real life perspective, Psychich powers and Magical powers might as well be the same, since there's not much difference between "Magic" and "Psychic" powers. The most commonly used "difference" comes from Magic using external energy while Psychic powers use *internal* energy and relying on the user's willpower.
As I said before; from a Watsonian perspective, people might reach a reasonable conclusion of what is happening when a Pyrokinetic manipulates fire, but it need not be exactly how it manifests. Good power systems focus more on a power's limits than the opposite, and it is often such limits that make magic/power systems memorable and satisfying.
Perhaps Pyrokinetics can only create/control fire/plasma as a whole rather than the ultra-accurate atomic manipulation, yet in-setting people can't explain beyond "He/She makes particles vibrate faster". Maybe Cryokinetics can only expland/guide a certain state of matter that is essentially "Frozen Solid" with only enough control to make things a tad colder rather than instantly freezing them.
Maybe the fire they create isn't burning physical fuel but the inner energy of the Pyrokinetic to stay alight.
Who knows?
Again, if you look really close, all answers will lead to "Particles are moving faster/slower" because at the end of the day that is what Heat and Cold *are*. What matters is presentation.
[Answer]
You mention the Dresden files, and that alone gives you some important take aways.
Dresden can call fire, but in one of the books he does explain that once he calls it, it still has to do business with the laws of physics. You can set something on fire, but once you do, thermodynamics takes over and entropy reigns supreme. Likewise with cold. Freeze something, and it will eventually thaw. This gives you a finite set of limits. Once your mage quits concentrating, for something to burn it will still need heat, fuel, and oxygen or the flames will go out.
Now for the mechanisms. I would keep this as a telekinetic type of power. That is the simplest and most rational explanation. Instead of gross telekinesis like lifting rocks, this involves the manipulation of tiny particles over an area. Here you have the opportunity to put an additional limit. Say a typical mage can only do molecular vibration over an approximately 3 cubic meter area of water. Anything denser gives you less volume. You may be able to heat 3 cubic meters of water to boiling, but to heat gold to 100 degrees c, you can only do an amount proportionate to the difference in density. You can change the numbers as you need, but that might be a baseline.
For the sake of consistency, I would have your mage be able to do both. It's all based on molecular vibration after all. Maybe one guy can do heat easier than cold or vice versa, but they should be able to do both.
Like in other magic systems, how your mage applies this talent and what imagination they bring to bear is going to show how powerful they are. If a mage is capable of killing someone by boiling their blood and because that is a very small volume, they can do it again and again, they would be scary as heck when compared to the guy who is only really good at setting the roof on fire.
So a pyro/cryo mage would be more properly called a heat mage, I guess. But you have some fertile ground to play in.
[Answer]
All of a sudden, Michael was on fire. For a second he could resist the sensation, but the knowledge that none of it was real was quickly being snuffed out by every nerve ending in his body screaming about stopping, dropping and rolling. He crumpled to the ground, hacking and coughing, as his lungs and brachia sent frantic messages of an unusable gas mixture.
Michael tried to will his watering eyes to focus, and clambered to his knees. He finally saw his adversary, a man, lost in concentration, obscured in a shadowy spot across the narrow pathway. Obscured by the shadows that confirmed the psychic origin of the bonfire that was searing Michael's flesh. He closed his eyes and focused on a defensive escalation.
A raging solar fusion engulfed him.
"Heat sink on an overclocked processor"
A fissile device reaching critical mass went off around Michael's left ear.
"Pressurized gas passing through an expansion valve"
A squadron of firebombers over London dropped their payload on him.
"An inclination in the planet's axis"
The flare dwindled further. Internal combustion in a freight ship's diesel engine now, and fading.
"The vacuum of interstellar space"
Michael was winning the dogfight, he knew it. The images themselves weren't important, they were simply framing devices for these exact situations, edging out your opponent.
Now he had fallen into a campfire, but it didn't even feel real. Where was the smell of s'mores? Michael grimaced and turned his thoughts to a basic counter-attack concept.
"Glaciers rolling unstoppably down a mountain"
The flames died off abruptly. Michael dusted himself off with shaky hands and walked over to the heap of a man that was moments ago attempting to stop his heart with unimaginable pain. The old man was lying nearly motionless, clutching his left arm in silent agony.
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Just because it's strictly psychic/illusionism doesn't mean it's not a fun plot device, and it can also help keep the magic restricted and avoid plot holes that tangible magic easily causes. In my opinion, the more hoops magicians have to jump through, the better.
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[Question]
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The dominant religion on my world (created by a race of dragon-like humanoids) believes that their species originates from an ancient being that sacrificed itself to defeat a great evil at the center of the cosmos. Its body remained adrift in space until it was eventually captured by the gravity of the young Earth-like planet that this species calls home. They believe this moment serves as the evolutionary beginning of the species, but also as the foundation of the land itself.
This idea is largely inspired by the [panspermia hypothesis](https://en.wikipedia.org/wiki/Panspermia) of distributing life across the universe, which I'll admit I'm still a bit shaky on the details of. In this case, this ancient being would be the vessel by which the necessary components of life were ferried to the planet, preserved in space within its body until such time that it just so happens to be lucky enough to come across a planet capable of harboring life. We can assume it managed to survive atmospheric entry, and that it crashed into a body of water if that helps the creation of life.
So this is of course a religious idea, but I'm curious to know if such a thing is actually possible:
(1) Could a life form (an utterly massive one, on the scale of [a continent](https://worldbuilding.stackexchange.com/questions/150899/what-impact-would-a-dragon-the-size-of-asia-have-on-the-environment)) remain adrift and preserved in space until its body collides with a habitable planet, introducing new bacteria/cells/genetic material that had remained dormant?
(2) Could this happen to the extent that some species that evolve from this event take on a similar appearance to the source, adapted by evolution?
[Answer]
**(1a) Pansermia is possible and arguably likely**
What you're looking for is a specific type of panspermia called **lithopanspermia** - the transportation of organisms [embedded in rock](https://en.wikipedia.org/wiki/Panspermia#Lithopanspermia) between worlds. The benefit of putting organisms inside rock (as opposed to clinging to the outside) is that they can lie dormant for thousands of years, unaffected by radiation. They'll need thousands of years, too. Space is vast, and orbits change slowly. Consider that the ALH84001 meteorite, which was blasted off of Mars, spent [16 million years in space](https://www.lpi.usra.edu/lpi/meteorites/The_Meteorite.shtml) before landing on Earth. Luckily, some bacterial spores may be viable [on the order of tens of millions of years](https://www.bbc.com/news/science-environment-14637109), so although panspermia takes a while, it could work.
**(1b) ...but it's hard to get such a big organism into space.**
A continent-sized animal [could not exist without magic](https://worldbuilding.stackexchange.com/questions/316/can-you-simply-scale-up-animals). Unless your life form is a tree like [Pando](https://en.wikipedia.org/wiki/Pando_(tree)) or an [unreasonably large fungus](http://www.bbc.com/earth/story/20141114-the-biggest-organism-in-the-world), it will be crushed under its own weight.
Assuming it does exist, my biggest question for you is: how did the progenitor organism get into space in the first place? A continent's worth of mass can't be lifted without smashing the entire planet apart. Such an impact might fry all bacterial life.
I would suggest only blasting off a part of the organism - or using the "progenitor" as a metaphor for smaller-scale lithopanspermia.
**(2) Similarities depend on the size of the life transported.**
The creatures on the starting and ending planets will be related only by their latest common ancestor - whichever microorganism is lucky enough to hitch a ride on a meterorite. If that organism happens to be a eukaryotic, multicellular microanimal, then the new life will share physiological similarities with it, at least for the first few million years. If that organism is a simple bacteria, expect only cellular-level similarities.
Fascinatingly, in really close planetary systems like the TRAPPIST-1 system, panspermia could occur [in as little as 100 years](https://iopscience.iop.org/article/10.3847/2041-8213/aa6b9f). On such a short timescale, you could transport some pretty big life on accident.
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[Question]
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The [Breakthrough Starshot](https://en.wikipedia.org/wiki/Breakthrough_Starshot) is a method of robotic interstellar exploration by launching thousands of small centimeter-sized probes, each equipped with a 4 x 4 meter light-sail. Thanks to their small weight, they can achieve speeds of up to 20% lightspeed even with technology currently available to us. As collision with even the smallest dust particles in space could destroy the probes at such speeds, thousands are to be launched so at least a few can arrive to their destination.
Let's assume that an intelligent civilization lives on the planet we launch these probes to, and they have a level of technology similar to ours, or at most only slightly more advanced. (Or that they launch such probes at us, arriving here within the next few years)
Could they be detected in any way? If so, could it be found out that they are made by intelligent beings in another solar system?
* if success only depends on a very narrow margin, the probes might be slightly larger (not by orders of magnitude!) or their speed might slightly differ from the 0.2 c in the question.
* I would guess they would be impossible or nigh-impossible to detect. Would this change if the arrival of such probes was theorized/expected, and special equipment was made beforehand to scan for them? (just as we have built Seti-radiotelescopes expecting aliens to try to contact us by radio)
* I would guess the probes would just fly by the planet making photos, taking measurements, and sending them home, and they wouldn't hit the planet. (they are not designed to slow down in the target system). If there is no other way to detect them, would this change if one (or a few) of them actually hit the planet? I would guess they would produce some gamma rays and such, but their small size would make them far from being catastrophic. Would such a crash be even detectable, and could it be assumed it was not a natural phenomena?
[Answer]
**TL;DR: Pretty unlikely**.
The objects are small (and hence faint), there aren't very many of them (astronomically speaking) and they're moving *very* fast so there isn't much time to spot them. Even if you knew they were coming, it might be tricky to catch a glimpse of them with today's technology. Basically, it would depend more on luck than judgement.
If a whole bunch hit Earth, we'd be more likely to notice, but the odds are even slimmer.
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Lets consider visible-light astronomy. This isn't totally unreasonable; the sail probably isn't very warm (being small, shiny and fast moving).
The faintest near-earth object in [this JPL database](https://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=neo;obj_kind=ast;obj_numbered=all;OBJ_field=0;ORB_field=0;table_format=HTML;max_rows=100;format_option=comp;c_fields=AcBhBgBjBiBnBsCkCqAi;.cgifields=format_option;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=com_orbit_class&query=1&c_sort=AiD) is [2008 TS26](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2008%20TS26), with an absolute magnitude of 33.2. We can [find the absolute magnitude](https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H)) of our solar sail by approximating it as a lambertian disk with [geometric albedo](https://en.wikipedia.org/wiki/Geometric_albedo) $a$ of 1 (this is wrong, but doing it right is quite a lot harder, so it'll do for now) and a diameter in kilometres $D$ of 0.004:
$$H = 5\log\_{10}\left({1326 \over D\sqrt{a}}\right)$$
This gets us an absolute magnitude of about 27.6... about a hundred times brighter.
2008TS26 has a semimajor axis of 1.92AU. Assuming that it is in [opposition](https://en.wikipedia.org/wiki/Opposition_(astronomy)) to the sun (a [syzygy](https://en.wikipedia.org/wiki/Syzygy_(astronomy)), an awesome word that is hard to use very often) it will have an apparent magnitude of 34.4, given that $$m = H + 5\log\_{10}\left({D\_{BS}D\_{BO} \over D\_0^2}\right) - 2.5\log\_{10}\left(q(\alpha)\right)$$ where $H$ is the absolute magnitude, $D\_{BS}$ is the distance from the body to the sun, $D\_{BO}$ is the distance from the body to the observer, $D\_0$ is the distance between Earth and the Sun and $q(\alpha)$ is something called the phase integral that I'm declaring to be 1 in this position.
With the same geometric relationship, we can rearrange the equation to find the equivalent distance of our solar sail where it would have the same apparent magnitude:
$$10^\frac{m - H + 2.5\log\_{10}(q(\alpha))}{5} = D\_{BS}^2 - D\_{BS}$$
Leaving us with a nice quadratic to solve, giving us a $D\_{BS}$ of ~5.35AU, the point at which we can *start* to see it with something capable of spotting 2008 TS26. We can solve a second quadratic with the non-constant parts $D\_{BS}^2 + D\_{BS}$ to find when we would theoretically *stop* seeing it, if the sun were somehow transparent, which would be 4.35AU on the far side of the sun.
These represent fairly optimistic figures, I think. They're slightly implausible, representing a trajectory that transects the Earth and the Sun, but you can perhaps imagine a closely grazing path which would behin and end at pretty similar distances, I think. An incoming probe travelling at 0.2c will cross that 9.7AU distance in approximately 41 minutes and 35 seconds. The points of peak visibility will be at the beginning and end of that traversal, and at some point in the middle when it is edge-on to observers it will be basically invisible. Any other trajectory through the solar system will have closer start and end of visibility points (because sunlight won't be maximally reflected towards us) and so the observation time will be reduced, but where the probe, Sun and Earth are at right-angles you might get a much brighter and easier to spot object. Too many variables, really. You might consider asking this question in Astronomy.SE where people might have a better idea of things like our observation capabilities.
Realistically, that gives us a few hours in which to have a suitably powerful telescope pointed in precisely the right direction (as such a powerful telescope will have a comparatively small field of view). I'm not sure how many such scopes exist, but the odds seem pretty vanishingly small, to be honest.
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> if success only depends on a very narrow margin, the probes might be slightly larger (not by orders of magnitude!) or their speed might slightly differ from the 0.2 c in the question.
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I'm not sure what the minimum flyby time would be to guarantee detection by current Earthbound observers, but I strongly suspect that it would be so long as to require very, very slow probes, and the chances of a civilisation bothering to fire such things out and hope they still work and people still care about them in a thousand years seems slim.
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> Would this change if the arrival of such probes was theorized/expected, and special equipment was made beforehand to scan for them?
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Maybe. The duration of the sail constellation flyby will be short, the objects will be hard to spot, and they'll likely to be widely separated. This seems like a pretty fearsomely complex challenge even with this huge advantage, given the potential margins for error.
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> If there is no other way to detect them, would this change if one (or a few) of them actually hit the planet?
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The sails pack a pretty substantial punch... about 4.3kT TNT equivalent. I don't think you'd get gamma rays, but you'll definitely get an interesting bang. I'm not sure what would be about to detect such a thing, but high-atmospheric flashes seem more likely to be spotted than distant, dim, tiny objects. If observed, the nature of the bang would probably be suspicious. I'm not sure of our capability to spot small objects entering the atmosphere, and this object certainly wouldn't leave a contrail so would be harder to spot (but more interesting if it were).
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Regarding Ghedipunk's comment:
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The laser array is powerful, at 100GW, but it only operates for 10 minutes per sail. That's a few hours for the whole constellation in which to spot the launch. The beams will be focussed on a spot very close to Earth (certainly within an AU) and so will be so enormously diffuse by the time it reached the target system.
I'm not quite sure how diffuse though. It is possible that some alien exoplanet survey might spot something funky happening with Sol's brightness during that very brief window of opportunity.
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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.
My heroine has been stabbed - run through the abdomen by a foot-long dagger - and is bleeding to death. She is currently crawling toward her salvation through a very cold place. She is magically immune to the harmful effects of low temperatures, but her blood, once it has left her body, is not.
I wrote a passage stating that as she crawled on hands and knees, her blood was dripping from the point of the dagger that has impaled her, and the environment was so cold that the blood didn't splatter on the ground, but instead froze solid and bounced.
My heroine is for purposes of this question a perfectly proportioned human female 170cm tall, weighing 70kg. Despite the extremely cold environment, her body temperature is a normal 37°C. The point of the dagger is protruding from her abdomen so that it's point is level with the lowest point of her belly. She is crawling on hands and knees, with straight arms. While she has been stabbed, and major organs are involved, the continued presence of the dagger is acting as a plug, preventing a rapidly fatal loss of blood. Most of her loss of blood is going into her abdomen, but enough is leaking out around the point of the dagger that it is dripping rather than gushing. Gravity is a normal 9.8m/s^2, and atmospheric pressure is around 60kPa, about average for an altitude of a bit over 4000m ASL. Please assume that the temperature of the blood droplets start at 37°C, and cooling does not begin until the droplet is falling freely, and the droplets must be frozen completely solid before hitting the ground, which for purposes of this question is effectively a flat surface. The blood droplets have not begun to clot significantly.
So, my question is this: Just how cold would it have to be for human blood to freeze solid before hitting the ground, so that the frozen droplets would bounce rather than liquid blood splattering? Is the required temperature realistic, in that Nitrogen and Oxygen can remain gaseous, and/or the temperature above 0K, or must it be "Magically cold"?
I am looking for answers that include all necessary proof and calculations, hence the hard-science tag. I am *not* looking for educated guesses without a basis on fact. While I mention magic, magic is only involved perforce in setting the starting conditions, and the answer will be: Possible, Possible but *x* atmospheric gases would not remain gaseous at the required temperature, or Not Possible due to the required temperature being below 0K.
**Edit:**
The droplets of blood will be falling a distance of approximately 30cm, though this may vary from 25-35 cm according to the exact position of the victim as she attempts to reach salvation. The blood droplets should therefore freeze solid after a downward journey of 25 cm at minimum.
[Answer]
# It's not possible
I don't believe it's possible to freeze a droplet in the time it takes to fall 25 cm. Here is why:
### Droplet properties
Thanks to Molot's link ([reproduced here](https://www.sciencedirect.com/science/article/pii/S037907381300090X)), a good estimate for blood droplets from weapons varies from 4 to 6mm. We can take the average and say 5mm diameter droplets. Using the density of water (1g/mL), we get 0.06 grams per droplet.
### Time of flight:
To fall 25cm from rest requires 0.225 seconds ($t = \sqrt{\frac{2\Delta y}{g}}$). Air resistance can be ignored in this case: compare the final speed before impact of 2.2 m/s ($v\_f = gt$) to the terminal velocity of 11.5 m/s ($v\_t = \sqrt{\frac{2mg}{\rho A C\_d}}$). Or put another way, the drag force is only about 2% of the weight of the droplet at the point of impact.
### heat of fusion of water:
Blood (aka water) has a heat of fusion of 334 J/g and a heat capacity of 4.148 J/gK. Therefore to reduce the temperature a droplet of water (with mass 0.06g) and freeze the entire thing would require the removal of 32 Joules of energy ($Q = m C \Delta T - m L\_f$ ).
### Rate of heat loss:
Removing 32 Joules in 0.225 seconds requires an average power of 141 Watts ($P = Q/t$). Blood (aka water) has an average [thermal conductivity of 0.5915 W/mK](https://www.engineeringtoolbox.com/water-liquid-gas-thermal-conductivity-temperature-pressure-d_2012.html) between 0 and 37 degrees.
**To pull 32 Joules of energy out of a droplet of blood 5mm in diameter in 0.225 seconds would require a temperature gradient of -7623K**.
($P = \frac{kA\Delta T}{L}$). This assumes the entire surface area ($A = \pi D^2$) transfers heat and the distance is across the radius ($L = D/2$). It also assumes a constant temperature gradient.
### Conclusions
It is not possible to pull 32 Joules of energy out of a droplet of only 5mm in diameter in 0.225 seconds. The coldest temperature gradient possible would be between absolute zero and 37C, or around -300 Kelvin. My estimate is something 25 times larger than that. Therefore, unless I have made an assumption that is over a magnitude off, I just don't see how you can freeze a droplet in such a short amount of time. Even re-running the numbers and estimating that only the first 1mm layer of blood need freeze (i.e. a shell of ice) produces an estimate of -6000K.
### Addendum
I don't want to leave you with a killjoy answer. Running the numbers in reverse, a droplet 0.5mm in diameter would freeze through with a temperature gradient of -76K. That puts the ambient temperature at 37C-76 = -39C -- very believable. While your heroine wouldn't drip droplets that small, she might cough up blood in a mist that would immediately freeze, the tiny beads making tinkling noises across the icy floor like throwing sand on glass.
[Answer]
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> The primary blood drop size ranged from 4.15 ± 0.11 mm up to 6.15 ± 0.15 mm (depending on the object), with the smaller values from sharper objects.
> [Source](https://www.sciencedirect.com/science/article/pii/S037907381300090X)
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Wound is blunt, and dagger handle is blunt, so $6mm$ diameter, $113mm^3$ volume and, lucky coincidence, $113mm^2$ surface area, is good bet within scientific range. Of course, each drop will be different - thus, selecting higher end of sizes makes sense, if big drops will freeze, smaller ones will, too. For completeness, drops from the point of the knife will be at $4.15mm$, $37.42mm^3$ volume and $54.11mm^2$ surface
Freezing blood is a complicated matter, as we can read [here,](https://www.jstor.org/stable/1676193?seq=1#page_scan_tab_contents) blood is frozen at $-3°C$, so we need to cool it by about $40°C$.
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> The specific heat capacity of water is 4.18 and of the human body (blood and tissues) $3.49 kJ/kg°C$, respectively. [source](http://www.zuniv.net/physiology/book/chapter21.html)
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So, it is a bit easier to freeze blood than it is to freeze water.
Blood density varies from source to source [see here](https://hypertextbook.com/facts/2004/MichaelShmukler.shtml) - it is up to $1066 kg/m^3$. This gives $120.45800mg$ of blood to freeze from wound / handle, and $39.88972mg$ from the tip
This gives us $16.8159368J$ of heat to remove from drop of blood to put it at the edge of freezing foe big drops, and $5.56860491J$ for smallest ones we can expect.
As per [this comment](https://worldbuilding.stackexchange.com/questions/139090/bouncing-beads-of-blood-just-how-cold-would-it-have-to-be#comment434221_139090) - I'm posting this as a partial answer with intent to finish when I'll have time to do further research.
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Heat transfer coefficient of air is up to 1kW per square meter per 1K temperature difference. [Source](https://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html). This source provides rather wide ranges, so potentially can be only used to prove "impossible"
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[Question]
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In [this paper by Bains et al](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284464/), an alternative to oxygenic photosynthesis is discussed. Apparently, 4 times the amount of biomass can be produced using hydrogenic over oxygenic photosynthesis.
Oxygenic photosynthesis is described by the equation:
$$n\, CO\_2 + n\,H\_2 O \rightarrow (CH\_2 O)\,n + n\, O\_2$$
And the hydrogenic process:
$$CH\_4 + H\_2 O \rightarrow CH\_2 O + 2H\_2$$
Both processes are endothermic, but the bottom one requires only a quarter the sunlight as the one on the top.
This process of interest because, since organisms that use it would have so much expendable energy, it would give rise to a *crazy* plant world.
As [this answer](https://worldbuilding.stackexchange.com/a/25736/53994) points out, you need some kind of reciprocal metabolism so that the super-plants don't eventually run out of methane and water. In addition to bringing an equilibrium to the planet, I would like this to be a heterotrophic metabolism, so that they can be herbivores that move around and do interesting things.
The only "solution" to this problem that's occurred to me is a metabolism relying on the combustion of hydrogen. But this is stupid because 1) it doesn't address the problem of methane 2) substantial amounts of hydrogen and oxygen in the same atmosphere is a recipe for disaster and 3) even if the combustion process was somehow perfectly contained and no lifeforms ever wanted to develop controlled use of fire, we would have to add another process which renews the oxygen content of the atmosphere.
The answer that I linked does speculate about the possibility of getting enough oxygen from terrestrial carbonate, is this feasible?
If not, what are some ways this could work? I'm open to adding any sort of compound to the atmosphere or crust of the world.
[Answer]
**Your reciprocal metabolism will regenerate methane and water.**
If your photosynthesizes generate carbohydrate and hydrogen from methane, water and solar energy, your heterotrophs will take the carbohydrate and hydrogen, liberate the energy and regenerate the methane and water.
I was interested to find in my reading that known methane-producing metabolic pathways all start with short carbons or CO2 and usually have a CO2 end product in addition to methane.
[](https://i.stack.imgur.com/9t6Yi.jpg)
<https://www.slideshare.net/SurenderRawat3/methanogenesis>
But methane production from CO2 and H2 yielding CH4 and H2O also happens. I don't understand why organisms don't skip over the CO2 making piece and just reduce carbohydrate right down to CH4 and H2O.
Ultimately, though, reduction of CHO to CH4 and H2O must happen all the time . Methane production starting with cellulose in biodigesters routinely make methane out of agricultural waste. Although I could not find a metabolic pathway described for a single organisms that did that, it is not hard to imagine.
[](https://i.stack.imgur.com/7L5Ro.png)
<https://www.researchgate.net/figure/Proposed-metabolic-pathway-for-methane-generation-during-WAS-anaerobic-digestion-Only_fig7_302978634>
Here too there is a CO2 step which must be necessary for reasons beyond my ken. If someone with strong chemistry can explain why methanogenesis must have a CO2 waste product, please do!
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You have the novel photosynthesis dreamt up by Bains. You could dream up another organism which uses the above pathway in its own cells. Or if you want to stick to terrestrial metabolic pathways you could have your heterotrophic herbivores have a rumen full of mixed microbes which cooperate in hydrolytically breaking down cellulose - not that edgy.
They will need hydrogen which your primary producers are making as a waste product. Unlike oxygen, hydrogen might escape a gas atmosphere. There are workarounds you could use to keep the hydrogen from leaving.
1: Water environment and hydrogen is dissolved. Or a liquid alkane environment - CH4 lakes can exist where it is cold, like Titan. Pentane / hydrocarbon lakes could exist on earth,. Absent oxygen(which is the case!) this could work.
2: [Hydrogen clathrates](https://en.wikipedia.org/wiki/Hydrogen_clathrate) - the hydrogen equivalent to methane clathrates, which do exist in high pressure environments on earth.
---
Here is a very cool thing. For heterotrophs like us earth, water is available, oxygen is available and reduced carbon is what we want to eat. In this environment, it might not be the reduced carbon sugars heterotrophs that is scarce. **It is the hydrogen product of the reaction.** The reduced carbon is easy to find lying around but hydrogen not so much - if it is not in the atmosphere the heterotrophs will have to drink a lot of hydrocarbon with dissolved H2 or scavenge up the clathrates to get the hydrogen they need for that half of the equation.
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Thinking about this, the "plants" will of course hang on to the hydrogen. They need to run the cycle backwards themselves, just as earthly plants oxidize carbohydrate for energy. Maybe these plants will have hydrogen clathrate "fruits".
] |
[Question]
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As you can probably guess from the title, I have some questions about the Hertzsprung–Russell diagram, especially how to use it to make plausible stars.
Some questions:
* Can stars exist in the black areas? For example, take a star of 30,000 K and $10^2$ solar luminosities.
* How likely is a star to be a supergiant, main sequence star, etc?
HR-diagram. Source: [Wikipedia](https://upload.wikimedia.org/wikipedia/commons/1/17/Hertzsprung-Russel_StarData.png)
[Answer]
To accurately answer your question, you might need to use a stellar evolution code, either doing your own modeling or looking up existing data tables. I'd recommend the [MESA code](http://mesa.sourceforge.net/) for the former approach, and [the Geneva grids](https://www.unige.ch/sciences/astro/evolution/fr/recherche/geneva-grids-stellar-evolution-models/) for the latter (see [Eggenberger et al. (2008)](https://core.ac.uk/download/pdf/159150281.pdf) for details). Numerical simulations are excellent, and as the results are often available to the public, you can get some nice results with a bit of effort.
That said, simply using these doesn't tell you anything about the population as a whole - in other words, how the masses of stars are distributed. This can be computed easily using an [initial mass function, or IMF](https://en.wikipedia.org/wiki/Initial_mass_function). An IMF is something of the form $\xi(m)\Delta m$, which tells you how many stars were born with masses between $m$ and $m+\Delta m$.1 This is usually in the form of a power law, i.e.
$$\xi(m)\Delta m=\xi\_0m^{-a}\Delta m$$
where $m$ is in solar masses and $\xi\_0$ is a constant. Essentially, if you want to find out the number of stars which have masses between $m\_1$ and $m\_2$, you integrate:
$$N(m\_1,m\_2)=\xi\_0\int\_{m\_1}^{m\_2}m^{-a}dm$$
where $\xi\_0$ is a normalization constant such that $N(m\_1,m\_2)=N$ for a sample of $N$ stars. A common IMF is the [Kroupa IMF](http://adsabs.harvard.edu/abs/2001MNRAS.322..231K), represented as a broken power law - in other words, $a$ is different for different mass ranges. This is really the answer to your question, if you're talking about the likelihood of finding a star in a given mass range.
I've written some code for this answer ([see on Github](https://github.com/HDE226868/Fun-with-the-H-R-diagram/blob/master/Kroupa%20IMF.py)) that generates a few plots. The first one is the Kroupa IMF, for a sample where $N=100$:
[](https://i.stack.imgur.com/FvKJm.png)
Here is the cumulative distribution function, the number of stars of mass less than $m$:
[](https://i.stack.imgur.com/QG2Bn.png)
However, stars are born and die at different rates. We can divide up their lifetimes into four stages:
1. Pre-main sequence evolution2
2. Main sequence evolution
3. Post-main sequence evolution
4. Stellar remnant
If you want to find the time it takes a star to pass through each phase, you can use some simple analytical approximations. [We can estimate timescales](https://astro.uni-bonn.de/~nlanger/siu_web/ssescript/new/chapter8.pdf) for pre-main sequence evolution ($\tau\_{\text{PMS}}$) and main sequence evolution ($\tau\_{\text{MS}}$). These give the amount of time a star spends in a stage as a function of its initial mass:
$$\tau\_{\text{PMS}}=10^7\left(\frac{M}{M\_{\odot}}\right) ^{-2.5}\text{ years}, \quad\tau\_{\text{MS}}=10^{10}\left(\frac{M}{M\_{\odot}}\right)^{-2.5}\text{ years}$$
The second exponent is often picked between $-2.5$ and $-3$; I've chosen $-2.5$ as a conservative estimate. Then, seeing that $\tau\_{\text{PMS}}\ll\tau\_{\text{MS}}$, we can see that at time $t$ stars of a given minimum mass won't have reached the main sequence yet, and stars of a given maximum mass will have already evolved off of it. Therefore, the total number of main sequence stars at a time $t$ is
$$N\_{\text{MS}}(t)=\xi\_0\int\_{m\_\text{min}}^{m\_\text{max}}m^{-a}dm$$
where
$$m\_{\text{min}}(t)=\left(\frac{t}{10^7\text{ yrs}}\right)^{-2/5},\quad m\_{\text{max}}(t)=\left(\frac{t}{10^{10}\text{ yrs}}\right)^{-2/5}$$
I've used these to create plots of the number of stars on the pre-main sequence, main sequence, and post-main sequence tracks over 100 billion years. Notice that even after 100 billion years, many of the stars still have not left the main sequence; they're low-mass red dwarfs.
[](https://i.stack.imgur.com/kQEfZ.png)
The answer to your second question - can stars be found in the black regions - is, essentially, a yes. All of the H-R diagrams here show the two large areas above the main sequence populated by giants and supergiants, but stars evolve back and forth along that area. For instance, a star may change from being a red supergiant to a blue supergiant (or vice versa), often including periods of violent activity. The evolved stars above the main sequence fall in a number of places.
You're not likely to see quite as many stars below the main sequence - the notable exception being white dwarfs - but some stars, called subdwarfs, do lie in that area. However, they're usually closer to the main sequence than to the white dwarfs. I don't think any are clearly visible on the H-R diagrams above, but they do exist. [Kapteyn's star](https://en.wikipedia.org/wiki/Kapteyn%27s_Star) is a good example of a fairly cool subdwarf.
If you want to get a better idea of which gaps are filled and which ones aren't, you can try looking at a star catalogue. [*Gaia*](https://gea.esac.esa.int/archive/) recently released a slew of new data this spring, and you should be able to determine temperature and luminosity for many stars. Assuming you can query that (or another) database, perhaps you can find some stars in unusual places.
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1 Bear in mind that a star may lose mass during the course of its lifetime, often through stellar winds (or, in a select few cases, violent eruptions).
2 You've heard of a protostar; a protostar is a pre-main sequence star that is still enshrouded by material from the molecular cloud that formed it, and is likely not visible.
[Answer]
I've grabbed an observational Hertzsprung–Russell diagram from the [wikipedia](https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram) article about the same.
In this case it's a plot of 22,000 stars and you can see that there's a lot more flexibility in where the stars lie, in practice a not insignificant number lie in some of the "black bits" of the simplified diagram you've posted. However there are still clear black areas.
[](https://i.stack.imgur.com/lnWp5.png)
[Answer]
1. Yes, stars can exist in the "black" area of your diagram. [Here](https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram) is a more detailed diagram, and this only plots 22 000 stars. There are more than a million times more stars just in the Milky Way galaxy.
[](https://i.stack.imgur.com/nKxqc.png)
2. That depends entirely on what region of space you are looking at.
And why is this even important? Are you going to be quoting statistics at your readers? You will make them fall asleep, just sayin'...
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[Question]
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Having looked for a few days I am pretty sure I do not have an answer on this question:
My intended planet will have the same density but double the mass of earth. I know this will increase the surface area a good amount but not to such an extent that I won't have earth-like terrain and oceans. Assuming everything else is nearly identical to earth, would this planet have the same Hadley, Ferrel, and Polar Cells? i.e. cutting the hemispheres at 30 and 60 degrees.
My intent on knowing this is to then map my continents and use the Köppen–Geiger climate classifications to fill in my expected weather patterns.
From here my only pieces missing is day and year length but given that I am not comparing to human terms I question the need.
[Answer]
## We have no idea.
As much as I hate to give up easily, atmospheric dynamics on Earth is not a solved system, let alone other planets. It was only ~30 years ago that we actually solved some of the equations that explain the Ferrel cells. More recently, there’s been some debate about whether changes in climate alone would be enough to create a single, dominant Hadley cell instead of the traditional 3-cell model.
What we do know, however, is that there will be an even number of cells on the planet and an odd number of cells per hemisphere as a simple result of heat flow. That’s why the bands on Jupiter have been theorized to be the result of Hadley circulation within the planet’s atmosphere, but we really aren’t sure.
If you’re curious for a more in-depth analysis, I’d strongly recommend the analyses done over at Harvard: <https://www.seas.harvard.edu/climate/eli/research/equable/hadley.html>
The second page has a bunch of scary math that justifies the conclusions on the first page, but even then the author isn’t confident enough to give a definitive answer. You’re probably okay with any number of circulation cells as long as it obeys the rules I listed above.
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[Question]
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So I'm writing a story about humans of the modern world being given various superhuman powers by an unknown entity, which eventually causes society to partially collapse and turn into a bizarre mash-up of post-semi-apocalypse and sword and sorcery adventure (various omnipresent powers render most of modern technology useless in a fight, causing people to fight exclusively with medieval-grade weapons and their various superhuman powers).
Now, one of the various things to result from this is the introduction of fantasy races into the world via giving humans the power to shapeshift, and one of the features I knew I wanted to add to one of the fantasy races in my story was an extra set of arms, since the possibilities that opens up both in combat and in everyday life are fascinating to me. But it occurred to me that most of the places an extra set of arms is usually placed on such races would probably run a serious risk of the arms getting tangled up or bumping into each other. So I spent a while trying to find a way to integrate an extra set of arms in a way that would sound right when described and actually work well in practice.
The idea that resulted is essentially that the four arms would all be mounted on the traditional human shoulder area (with a thicker upper torso to let them fit both shoulder joints side by side), but with more flexible shoulder joints for each and a special, additional, internal shoulder joint that, by a combination of weird biology and straight-up magic, allows them to actually rotate the relative orientation of these shoulder joints to each other so they can shift the positioning of them from back-to-front to up-to-down and even a little further upward, so that they can alter the most practical positioning of the arms for what they want to do and, more notably, if they use both arms on one side to grab a single object, they can swing that object around with two arms as if it was one arm and have the same range of movement that a human would have swinging around one arm. Each arm would have the strength of a human arm, and the internal pivoting shoulder joint would have the 1.5 times the strength of a normal human shoulder joint (keep in mind that most of the characters in this story have their strength further doubled by an omnipresent power as well).
Now to me this sounds like a *huge* advantage. Even realizing the practical limitations on wielding multiple weapons at once, being able to have 50% to 100% more force behind a blow, carry multiple shields, wield a two-handed weapon with a slight sacrifice to grip strength and still have two more hands, wield a bow and arrow *while riding a bike* in a world where cars are useless and horses are scarce, and utterly dominate hand-to-hand combat with terrifying grappling techniques and hybrid offensive-defensive stances (keep in mind that bare-fisted combat is much more practical here as everyone's hands, feet, head and neck are all but indestructible) sounds like the advantage they'd have over a normal human would be ridiculous.
In fact it seemed like such a huge advantage that when working out how to balance this race, I concluded that merely having their physiology, their arms combined with their generally slightly stronger and more durable bodies, would have to be balanced by severely reducing the types of magic powers they have access to (to keep humans from becoming the boring jack-of-all-trades race, humans are the only ones who can use all six types of magical abilities in my story, and each race pays for their advantages over humans by losing access to at least some of them, usually just one type). I realize it would be impossible to briefly summarize my design philosophy of the powers, so let's ignore them for now and just assume for the sake of argument that they're designed such that mages and physical fighters are pretty much balanced, all other things being equal, and that fighters have the same number of powers as mages, just generally in more physical abilities.
**Am I correct in thinking this would be a huge advantage in combat with medieval-level weaponry and that they'd need to pay a steep price elsewhere to be balanced? Am I overestimating how useful this would be? Am I underestimating it? Or is there some fatal flaw I'm missing with the arm setup I've described that I need to work out?**
[Answer]
Your shoulder knights would make very effective shield walls and phalanxes. Each soldier can carry two shields and two spears in some combination of overhand and underhand. Overhand is better for not hitting your friends with the butt of your spear. So your force has twice the covering per person and presents twice as many points to the enemy. With proper drilling the extra arms shouldn't get in the way if they restrict entirely to thrusts.
Another possibility is one shield, one or two rondel type daggers and two free arms for grappling. This unit would be a specialised at countering heavy armor. The idea is to close quickly, block the first blow, then grapple and opponent and stab through the neck/visor/armpits. Again sticking to the thrust there is less problem of the arms interfering with each other.
In all other forms of combat I see the extra arms getting in the way of each other. Four swords is certainly a bad idea since historically two weapons was just a substitute for one weapon and a shield.
For personal combat I see the shoulder-knights sticking mostly to two-arm style -- already superior to a human fighter -- but with the opportunity to decouple the inner arms and grab their opponents' arms if the opportunity presents itself.
Using two long weapons is probably out. But one advantage of four arms is the wider grip it offers on a weapon. So you might see a *three arm style* with a heavy shield and a long weapon like a halberd gripped about three feet apart with both right arms. Then you have the purchase to deliver the sort of swings a human has to ditch the shield to achieve. Still this is more for personal combat and wouldn't work in dense formation without chopping your friends' heads off.
**Problem:** This is your world, so maybe it is common to carry around large weapons for personal defense? But historically I think it was uncommon to carry around battlefield sized weapons unless you were on the battlefield and ready for mass combat. So there was no cause for a large weapon that is effective in duels but ineffective on the battlefield.
[Answer]
There's a significant advantage to holding a sword with two hands, and your four-arms guys could do that and still hold a shield (or two shields).
[The advantage of holding a sword with two hands instead of one is leverage, which gives much greater strength and control.](https://i.stack.imgur.com/Vferp.png) It either allows wielding a longer and heavier sword with the same strength and control as a shorter one in one hand, or allows wielding a more normal-sized sword with more quick movements and better leverage than one-handed.
Your four-arms guys have all the advantages of a two-handed swordsman but not the main disadvantage: the lack of a shield.
So oddly enough I think your four-armed men would do very well going into battle with a single large sword or mace held with both the arms of one side, and a shield or shields on the other side. Although you'd think using the conventional setup would be a waste of their unique traits, that wouldn't be the case at all. They'd wield the sword and shield with much greater strength and agility than other men. They'd be extremely hard to face by a man with two arms. When going up against a two-handed swordsman, you can't sword-fight with them, because their sword blows are just much stronger than yours. You try to catch their sword on your shield and then stab when they're exposed (because they have no shield). But your quad-arms have that same two-handed sword advantage...and also a shield.
An even deadlier setup might be a greatsword in the two right arms, a shield in one left arm, and a light stabbing sword in the other left arm. Swing the greatsword, they get knocked hard, but catch on shield, they thrust with their sword, you deflect with your shield, and finish them with the stabbing weapon you had tucked behind the shield.
[Answer]
I fully agree that these dudes would be a wrestler’s worst nightmare, to the point where grappling might the dominant strategy for this group. What you could is to say they have some issues with coordination, not because their arms get tangled, but because they have so many limbs to work with and balance. Learning combat skills could take longer for this species (race?), so humans and other peoples could be better combatants on average. Once a Shoulder-lord gets good, though, it can utterly dominate. Until then, they could have a real problem with overconfidence.
"My uncle Linny took on four humans at once. I can take one."
"Your uncle Linny practiced two hours every day for five years, Chuck. You're going to accidentally cut your own hand off half way through the battle, assuming you don't just fall over when you overbalance and get stabbed through the back."
Other than that, this race doesn't have that big of an advantage at ranged warfare, which other magically gifted species could exploit. If you keep the shoulder-lords at a distance, people can take them out with arrows, fireballs, and any other ranged attacks you can think of. Shields would be a good counter, but shields aren't perfect.
Because these dudes are top heavy, would they have slower movement speeds?
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[Question]
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A submission for the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798).
[](https://i.stack.imgur.com/2J1aA.jpg)
The plant genus Mandragora as we know today are nightshades that contain highly biologically active alkaloids that make them poisonous, with their roots in particular used in traditional medicine. But in old foklore, not only it was a powerful plant in sorcery and herbal medicine, many depictions were more human like.
Dioscurides, who documented it's medical uses, he described it to have a male (Mandragora officinalis) and female (Mandragora autumnalis) shape, so there's some sexual dimorphism there. And according to the legend, when the root is dug up, it screams and kills all who hear it.
[](https://i.stack.imgur.com/jhvrB.jpg)
So now we have a species that can live underground, and have roots and leaves that contain hallucinogenic, and hypnotic effects biologically. For this question we're to assume that the hypothetical Mandrake is a fully sentient species that instead of evolving as a plant, it evolved closer to humans. How would it evolve to it's plant-like form?
[Answer]
I have a suggestion for a partial answer.
The *mandragora* may have gradually evolved to absorb some forms of nutrition via its skin, in contact with the soil. Some creatures form symbiotic relations with algae and other creatures that live on/in their surface layers and produce nutrition from the environment or light, and our own mitochondria started as separate forms (I think), so perhaps this is plausible.
Over time the soil being rich they lost much of their mobility, and became a creature that is largely static and inert, and only slowly moves place to place. Mentally, if they were intelligent before, then they became introvert philosophers, and gradually thought and looked outwardly, less. If they were sentient but not highly intelligent perhaps they regressed.
(This would make sense; intelligence no less than other traits, is subject to evolutionary change, it takes a lot of energy and has no special privilege genetically speaking beyond any other survival/reproduction factor, so it may well be lost if the advantages are few and other changes to behaviour, environment, or other matters affecting their species push them in different directions).
As their food/nutritional sources became gradually more co-dependent with their symbiotic partners, they developed defences for the photosynthesising symbiotic creatures on what was their heads, and chemical defences in their dermal.layers below ground (slightly but not excessively rooty, and also home to soil converting bacteria/symbiots). In air, acoustic was less costly in evolution terms for reasons of past biology.
(Symbiosis often provides defence/favourable environment benefits to one of the partners and food for the other, so this is quite common and would be a sensible and even likely development.)
They only move slowly, but they live a long time. They give birth by partuition or external placenta equivalent (maybe that was more common in their ancestral world or life form and wasn't unusual), and as with humans, the young need a favourable environment and nutrients; they form underground. Chemicals given off by their symbiots deter the few underground predators such as moles or rodents that could pose a risk, until the new mandragora splits off and begins its own lifelong and very slow travel. This wouldn't be a difficult adaptation; even among real-world creatures many/most have neonatal stages inside bodies or below ground level. The new mandragorae have all their early needs met from parental nutrient (and warmth if needed, although cold blooded might fit better), and symbiots from their parental dermis quickly colonise their own dermis. Their banshee scream is for multiple reasons:
* to defend themselves
* to defend the was-head-based symbiots, and especially to defend the soil/below ground symbiots, which will die if exposed/dried, and which hurts them too. (The ancestral symbiots ensured they were cared for by dumping pain-causing chemicals into the mandragora if suffering; over time the mandragora evolved to take the symbiots' pain as its own.)
* because if it takes 20 years to move 1/4 mile to a nearby heterogynous mandragora, you'd scream too if someone tried to get in your way.......
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[Question]
[
My story is set in the 2100s. Everyone on Earth has a computer implanted in their brain that they use to interface with the technology of the era. A side effect of this is that most violent conflicts begin (and end) with a "psychic" conflict using the implants. This drives a lot of the concepts in my world.
Obviously, the best way for the bad guys to defend their HQ is to fill it with autonomous robots that can't be fought this way.
Is it a given that such technology would exist? Can I do something in my world that would make such technology:
* Nonexistent?
* Scarce (so it makes a good boss battle)?
* Easily defeated with the right tactics ?
To add some clarification about my agents:
* These are the equivalent of FBI agents. They aren't hackers.
* Hacking works in this world pretty much like it does now. It can't really be done with no prep in real time.
* They have both mental and physical combat training
[Answer]
If technology continues to develop as it has over the past ~15 years, robotic soldiers (that likely won't look humanoid) will respond more accurately, precisely, cheaper, and drastically, *drastically* faster than any human could by the late 20xxs, let alone the 2100s.
We've already seen leaps in autonomous drivers. In 2004 for the DARPA Grand Challenge not a single vehicle completed the course successfully. In 2005 23 of the 24 vehicles surpassed the furthest distance traveled int he 2004 race, with 5 completing the race.
Whenever soldier robots begin real development we'll likely see equally drastic improvement. It'll only be a handful of years--maybe a decade--before we go from prototypes to machines that can respond with gunfire (or whatever weapon) with greater precision and accuracy and do so in a small, small fraction of the time that humans take even to focus on the target. Humans, quite simply, won't be able to compete.
Not only would robots be the go-to against organics if they exist they'll be the go-to in general if actually troops are needed (they might not be).
So how can you stop this?
Stop them from existing, or at least wide-spread.
Make it against some internationally held laws, with fear of robotic soldiers so dearly held that anyone who tries to move forward with the effort sees globally-united efforts at stopping them. *Some* rogue nations and particularly well-off criminal empires might have them, but they only do so in very limited numbers and under considerable amounts of secrecy.
[Answer]
You ask about ways to make a particular technology nonexistent, rare, and common. I think the real key here is not to dig into the autonomous robots at first, but to dig into the implant and *why* people get the implant in the first place. Surely this is a major world-defining feature of your story, and it's worth fleshing it out.
First off, I'd like to introduce you to my first generation psychic-proof robot:
[](https://i.stack.imgur.com/8nOivs.jpg)
Now astute readers of this answer will note that the Brick v1.0 is not very mobile. However, everyone will have to admit that it is completely resistant to all psychic attacks via the implant.
Brick v1.0 is, of course, a straw man argument. Nobody is going to defend their HQ with an army of bricks. However, it turns out to be a very useful tool for exploring the issues with these autonomous robots. Our evil overlord would really like their robots to be able to do their bidding. The ability to communicate with the robots is essential, and if you think about it, that is probably the singular reason to have implants in the first place. You're better at conveying your intent to a robot psychically than you are with voice commands or a flash drive.
So I would recommend using this as your primary slider for adjusting how valuable autonomous robots are. If you want autonomous robots to be common place, weaken the power of the implant's ability to convey meaning to other robots, and naturally people will not be as dependent on them. They'll accept autonomous robots more because the autonomy really doesn't hurt them all that much. On the other hand, if you want these autonomous robots to be ultra rare, make the ability to convey meaning psychically into a very powerful ability. If there's a monumental advantage to using psychic communication, you will find people use it.
Once you've dialed in how common you want autonomous robots to be in general, you can fine tune how common they are for evil overlords. To do this, you need to identify a subtle weakness in the psychic system and have your evil overlord exploit this to bring good-dooers down to a level where autonomous robots can actually be a threat. There might be an issue with electromagnetic interference. Or perhaps there are positions where no amount of communication between devices helps, and might makes right (of course, autonomous robots would be designed to be mighty). Or maybe people are just plain lazy now, and literally wont lift a finger if they can help it.
Or, if you want to be even more nefarious, make them psychic, but have them not act on any psychically delivered instructions. Have them lure the good-doers into believing that they have psychic control over the autonomous robot when, in actuality, it's just playing them.
By tuning in the general societal treatment of the implant first, and then making the evil overlord's approach an outlier, you'll make the effects of these implants feel more realistic. Of course, this does mean you have to be creative enough to create a convincing evil overlord outlier, but that's where the fun is!
[Answer]
I think this question and Nex's answer make these drones out to be a bigger problem then they probably would be since electronics are highly sensitive equipment and a tiny static shock in the right place can destroy them.
Basically what I'm saying is that things like EMP, electrical, sticky (splatter goop in a large area to gum up robotics), and a number of other crafty small ordinance would be developed to combat these drones.
Yes, they would likely be hardened to EMPs and electrical attacks, however, they'll still need moving parts and visual capabilities so anything that messes with these would be deadly to them. They'd probably be able to recover eventually, but if you can stop them from killing you for a bit, you can take it out of commission even without completely destroying it. Lastly, humans are notorious for coming up with lots of ways to solve problems whereas an autonomous drone is going to follow a very basic set of commands and can thus be foiled through ingenuity like luring it into traps, etc. and even with lots of different possibilities programmed in, it's just a matter of finding a combination of circumstances it isn't programmed for and eliminating it.
[Answer]
Cool scenario. Psychics. Robots.
A true AI robot like R. Daneel Olivaw in *I Robot* does not need to be told what to do. If something of this ilk wanted to kill you it would be big trouble.
An autonomous robot which is not intelligent needs an interface: to update program, upload commands / routines etc. The robot needs to be told what to do and then it runs through its routines. Possibly it can cope with many variations on routine but not an infinite number. This leads to 2 counter measures.
1: Hack the interface and tell the robot to do something else. Commandeering enemy robots is always welcome. From Art of War *Hence a wise general makes a point of foraging on the enemy. One cartload of the enemy's provisions is equivalent to twenty of one's own*
2: Give the robot a scenario so far outside its routine that it does not have a response. The strategy exemplified with Monty Pythons Confuse a cat Ltd. Subtitulado! <https://www.youtube.com/watch?v=qGRgFpT-zkM>
[Answer]
You could always equip yourself with another sort of tropy future bad guy...The Nano Bot! Make it move fast and inject itself into gaps in the killbots armor. From there you have a range of options, such as the Nano bot gums things up, welds critical joints, or even interfaces with the machine AI to give the hacker psychic control. Then that killbot goes and kills a bunch of other killbots.
I like the idea of legal hurdles being in the way of creating killbot armies. If you outlaw kill bots, only criminals will have killbots. That sets you up nicely for bad guy boss battles and such.
You could create scarcity by making the necessary battery material required for an energy intensive killbot ridiculously expensive or difficult to create. If you need 30 kilograms of pure gold to make the necessary contacts, then this thing is going to be priced well beyond most ordinary bad guys.
[Answer]
It seems to me if the technology exists to create autonomous robotics then a true fully sentient AI is not far away, and if it can be done someone will do it. Probably several someones.
A sentient AI or two roaming the internet, would likely be impossible to delete, but governments could likely keep it mostly contained with ever evolving firewall's and "anti-virus" type software. Like the flu, some people get sick every year but it's more nuisance than plague. Between vaccinations and evolving immunity it's not really a big deal.
With that kind of AI roaming around intelligent robotics might be at higher risk for the AI to try and commandeer them. Building intelligent machines would then become a risk. That would keep the relative intelligence of such autonomous sentries to a minimum, out of necessity they would need to be easy to shut down or take out if necessary, but still dangerous enough to be worth building. You would end up with dumb networked machines, or intelligent but deliberately stand-alone machines, either of which a group of humans working together effectively should be able to deal with.
[Answer]
# Robotic Scarcity
We've had the technology for some *basic* battlefield-robotics for a while, and yet things as simple as unarmed camera-drones still aren't commonplace. It's not about them being vulnerable to hacking, or ethical concerns...
### It's all about the about money.
Consider, for a moment, that the average Private in the US Army makes less than 20,000 USD per year. Even a Staff Sergeant makes less than 30,000 USD in annual salary. That means that paying the yearly salary of an entire fireteam (Four people, usually several privates with at most one Junior NCO) costs around 90,000 USD - Less than a mid-to-high-end luxury car.
For comparisons sake, a *single* Javelin missile and command/targeting unit runs nearly 200,000 USD. A single shot for a vaguely high-tech weapon costs as much as 10 men. I don't have any hard figures on infantry-scale combat robotics, but I can only assume they'll easily reach into the millions of dollars.
### Unfortunately, life is cheap.
You might call it dystopian, but our world is already in a place where it's cheaper to pay people to die than it is to build robots and save lives. Now, I assume your evil crime-lord/ mad scientist has the funding to afford robot soldiers. Let's also assume that they're tougher, faster, more heavily armed and more psychically-resistant than your average non-hero. They can take a headshot and keep fighting, and they never miss (Unless they're aiming at protagonists.) Perfect fighting force for every situation, right?
But.... For the price of just one of those robots you could probably pay several dozen if not hundred undesirables to do your bidding. The more poor and destitute they are, the more cannon-fodder you can afford to simply throw at the problem. As an added benefit, if they die you no longer have to pay their wages, whereas your robots would require an astronomical repair and maintenance budget.
# Anti-robot tactics
As Nex Terren pointed out, these robots may have super-human abilities. However, since we're in a world of cybernetically-augmented psychics. By our standards, everyone is a superhuman. Therefore, I don't think it's a guaranteed win for the robots.
An important question to ask is what these robots were meant to do. Perhaps Nex Terren is right, and the battlefields of the future will be completely robotic. In that case, our big boss might have black-market military surplus, in which case the robots are built to fight... Well, other robots. While it's gruesome to think of what an anti-armor weapon would do to a human, a non-armor-piercing light machine gun is simply a better weapon to use against people. If this is the case, the tactics could be as simple as 'Trick them into firing, and attack while they're reloading.'
Or maybe the robots are stolen riot-control droids, or hacked construction units with a very.... Liberal definition of what requires sawing and welding. Maybe they're custom built sentries that shoot anything without a transponder on-sight. I could speculate robots and countermeasures all day, but it's very hard to come up with tactical level counters to a force you know nothing about.
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[Question]
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My question was inspired by that one on [robot police](https://worldbuilding.stackexchange.com/questions/42289/why-would-a-country-employ-a-robotic-police-force)
Imagine a world where police is mostly operated by robots, at least for the simple operations that does not need high-level decisions. Of course, like in any other worlds, there is a technology race between the warrants of public order and the criminals.
**How will criminals adapt and how will they use robots for their criminal activities?**
Will they use it mostly as weaponry? Use hacking robots? As a substitute ("go rob the bank")? Have they smarter ways to use robots, for exemple to commit new types of crimes that the robotic technology would allow?
For the sake of this question, robots need not to be humanoid, so drones apply. But are autonomous: they don't need human supervision, at least no more supervision than human police in our world. They can analyse a simple situation, and follow simple orders. For example, the effective operations of anti-riot force and SWAT-like units will be operated by robots, but the strategy will be decided by humans.
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I think the most likely, or at least most efficient way for criminals to adapt, and have no doubt they will, would be for them to start with hacking.
It doesn't necessarily even need to be overt control or an obvious hack that alters the day to day function of the police bots.
Criminals would be best served by hacking them and gaining access to the police network. With this access criminals could stay one step ahead of the police and ensure they have a heads up when police actions are imminent.
This would give them time to prepare or better yet relocate and avoid the police altogether.
It would also allow them to gather data on routes and coverage to better plan their nefarious deeds, and to avoid detection and capture.
Now, in the event that things get out of hand or a police operation takes place with regular old humans criminals could wait for an opportune moment and take control of the bots to throw the police into chaos and start infighting so as to cover an escape or turn the tide of a fight.
Police bots seem like they may be a bad idea...
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# Crime in a Robot-Friendly Setting
The *ability* to field a police force with robots implies advances in AI, telecommunications, and related fields. That means **the digital economy is *the* economy**. Only hopeless drug addicts go mugging people in the physical world, any successful criminal will do it in the digital world.
Advances in surveillance tech might mean that any criminal has to take much greater care to protect their tracks. Physical involvement with the victim is right out. The digital trace has to be laundered through "darknet" services, servers in Nigeria *and* Russia *and* some weird little possession of the British Crown, and so on.
# Specific Reactions to Robot Cops
* How heavy are those thingies? Set your headquarters in run-down housing where the floor can be prepared to break under the weight of a robot. The crashing noise gives enough warning to take the prepared escape route across the roofs.
* Which senses do they use to track people? Can they be fooled? For instance, can there be face masks that are designed against a (known) face recognition algorithm? Early systems could be thrown off by glasses.
* Is it possible to track the deployment of police robots? Do they have distinctive commo signatures that could be pattern-matched?
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**You zap all the police robots and drones with an EMP drone.**
All the delicate circuits within the machines will short out after a single burst of an EMP. Some might think [ElectroMagnetic Pulse](https://en.wikipedia.org/wiki/Electromagnetic_pulse) can only be created by nuclear weapons, but militaries have created [non-nuclear EMP's](https://en.wikipedia.org/wiki/Electromagnetic_pulse#Non-nuclear_electromagnetic_pulse_.28NNEMP.29) with cruise missiles and drones.
Imagine drones that fly over a city shorting out **all** the non-hardened computer equipment everywhere. Every machine in the city shuts down. All the criminals can get away with anything for a few hours until power is restored and police deploy any drones and robots that were in storage. (Think of [The Purge](https://en.wikipedia.org/wiki/The_Purge) story.) The criminals will know in advance when the Pulse occurs, but everyone else will go about their lives unsuspecting until all hell breaks loose. The criminal gangs will store their cars and their computers inside concrete basements until after the Pulse is over.
Everyone else will see their cars stop suddenly, their smart phones die, their laptops die, and their bank security systems fail. Criminals could just drive where they want, grab what (or whom) they want, and kill whom they want. Nobody's smartphone camera could record their crimes. The criminals would know **not** to use cell phones after the Pulse. They would
When the police finally deploy their backup robots from storage, the criminals use their many drones to Pulse again and again until all police drones and bots are zapped. Then criminal gangs will reign supreme for days until the governor or president sends in the National Guard to restore order. By which time, the criminals have left town.
To quote Wikipedia on the topic of non-nuclear EMPs:
>
> The range of non-nuclear electromagnetic pulse bombs is much less than nuclear EMP. Nearly all such devices used as weapons require chemical explosives as their initial energy source, producing only one millionth the energy of nuclear explosives of similar weight. The electromagnetic pulse must come from within the weapon, while nuclear weapons generate EMP as a secondary effect. These facts limit the range of NNEMP weapons, but allow finer target discrimination. The effect of small e-bombs has proven to be sufficient for certain terrorist or military operations. Examples of such operations include the destruction of electronic control systems critical to the operation of many ground vehicles and aircraft.
>
>
>
It would take a fairly sophisticated criminal organization to create and deploy EMP drones, but it is possible. Somebody with knowledge of physics, chemistry, and electrical engineering could do it. You would also need to channel a huge amount of power onto the drones. It's also likely each drone would be a one-and-done device. If you use a chemical reaction to generate the energy for each Pulse, that reaction would destroy the drone. Which is why you think of these drones as bombs, and not something you can fire again and again like a gun.
The criminals could only do this a few times until police harden their drones and bots against EMPs, and corporations store all their major computer hardware deep inside concrete bunkers in the bottoms of buildings. And the people would know the next time a Pulse occurs, the governor will send in the National Guard immediately to shoot on sight.
[Answer]
I hate to say this when you've put so much thought into the question, but basically by ignoring the matter.
Unless you've equipped these robot officers with marijuana detection sensors, they're going to be less effective on the street and unable to run a complex investigation.
The average idiot on the street being pulled over for running a red light or being over the speed limit might be more likely to get in trouble, but robots probably won't suffer from prejudice and, unless programmed to, will probably not profile people. This means that the rate of casual malicious enforcement is likely to drop. When told to random sample, they will pseudo-random sample, they won't randomly sample all the Arabs or Africans, they won't randomly sample everyone with dreads.
But the real professional criminals? That needs high level decision making, cross force communication, international co-operation. Investigative skills, human contact skills, and usually a great big load of luck. Robot law enforcement aren't going to be interacting with real criminals.
[Answer]
"It takes a thief to catch a thief."
I don't know who coined it, but the saying seems generally accepted as true, and highlights a commonly perceived obstacle in law enforcement, that a law abiding officer -- which, I must assume, is one reason to have a robot police force, so ideally human sin and error are minimized -- however skilled, simply does have a criminal mindset. Professional criminals perceive the entire world differently, so adaption will likely be in unexpected, criminally brilliant ways.
However, there are also criminals who inadvertently outwit the law, and by unconscious heuristics subvert the system, and not by being very intelligent, but intuitively or by plain luck.
For example, if robot/people cops only use the newest and best technology, and the fortunate criminal keeps using his or her legacy system for communication, either by chance or some belief that it's 'lucky,' such a criminal would be very difficult to catch, especially in an advanced society. So long as no major blunders were made at least. Another way of saying this is, what if it never occurs to cops in a future society to read snail mail?
I think two things from Murphy's Law of Combat are parallel to the criminal mindset which cause untold trouble to law enforcement, which make criminals difficult to handle, regardless of technology:
1. If it's stupid but works, it isn't stupid.
2. Professional are predictable, the world is filled with dangerous amateurs.
In other words, however numerous and skilled the hounds, they never see the world as a fox.
Starting with a precept that criminals will cleverly hack and subvert a system, using the Man's technology against Him is a rather academic view of people whom generally aren't. Practicality rules. And using tech in any way would tend to give an edge to law enforcement, not the other way around. The creator of technology always knows it better than a user, even a smart one. The Man makes/funds tech, criminals will almost always just be users who found a crack in the wall.
And anyway, technology aside, as I understand it, according to Mitnick, the best hacks have always been via social engineering, not device exploitation, though it helps sometimes.
For reference on your subject, check out the original Stainless Steel Rat trilogy by Harry Harrison. The series explores the topic of future criminals.
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[Question]
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*Disclaimer*: This question is the second 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, [evolutionary factors](https://worldbuilding.stackexchange.com/questions/56701)
---
*Setting*: In my [conworld](https://worldbuilding.stackexchange.com/questions/19788/how-would-flora-behave-on-a-two-continent-planet) 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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*Fauna*: The Beasts-of-Burden (further BOB) coexist with many other animals and have coevolved with them. They do not directly supplant any other group of *earth* animals; they fill their own niche as the largest docile herbivore of the more mountainous regions ([more info on its characteristics](https://worldbuilding.stackexchange.com/questions/56329)).
Other than BOBs, the conworld contains most of the [families](https://en.wikipedia.org/wiki/Family_(biology)) of *earth* fauna & flora but with much less variety in [species](https://en.wikipedia.org/wiki/Species) (thus there are [horses](https://en.wikipedia.org/wiki/Horse), [cattle](https://en.wikipedia.org/wiki/Cattle), [goats](https://en.wikipedia.org/wiki/Goat), [wolves](https://en.wikipedia.org/wiki/Gray_wolf), [and](https://en.wikipedia.org/wiki/Pig) [so](https://en.wikipedia.org/wiki/Cat) [forth](https://en.wikipedia.org/wiki/Bat)). There are also other hexapeds, although likely not as various as quadrupeds.
*Hexapeds*: Besides the BOBs there are a bunch of different, as of yet not clearly defined, hexapeds. For the sake of this question we assume there to be hexapeds fitting into different categories of land-based [mammalia](https://en.wikipedia.org/wiki/Mammal). Thus there are likely some more, maybe smaller hexaped-herbivores. There's likely to be some hexaped-[rodents](https://en.wikipedia.org/wiki/Rodent) (e.g. *hexarats* which can climb buildings easily), as well as there are bound to be predatory hexapeds (at least some will have evolved to more efficiently hunt *hexarats*, let's call them *hexacats*).
Still none of these will feature a pair of *hands*.
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**Question**: Where do BOB fit into [Linnaean](https://en.wikipedia.org/wiki/Systema_Naturae#The_Animal_Kingdom) taxonomy? And why did you put it there?
*Bonus* (for additional points): Where would the BOB fit in modern (current day) taxonomy?
The question only looks at this **northern continent**.
The question does not ask for the plausibility of a six-legged mammal in general.
[Answer]
This is rather antiquated as yourself allow, but it is a fixed system. There isn't much room to get it wrong.
These hexapeds are evidently Animalia, and incorrectly classifed as Mammalia. It should be evident that it doesn't belong to Aves (birds), Amphibia, Pisces (fish), Insecta, nor Vermes (worms). That part is easy...
Now, let's see...
* **Belluae**: *Fore-teeth*: obtuse, *Feet*: hoofed, *Motion*: heavy, *Food*: gathering vegetables. (?)
* **Bestiae**: *Fore-teeth*: indefinite numbers on the sides, always have one extra canine, *Nose*: elongate, used to dig, *Food*: digs out juicy roots and vermin. (✘)
* **Bruta**: *Fore-teeth*: none in any jaw, *Tusks*: in elephants and manatees, *Feet*: with strong hoof-like nails, *Motion*: slow, *Food*: (mostly) masticated vegetables. (?)
* **Cete**: *Fins*: pectoral instead of feet, *Tail*: horizontal, flattened, *Claws*: none, *Hair*: none, *Teeth*: in some cartilaginous, in some bony, *Nostrils*: none, instead of which is a fistulous opening in the anterior and upper part of the head, *Food*: mollusca & fish, *Habitation*: the ocean. (✘)
* **Ferae**: *Fore-teeth*: conic, usually 6 in each jaw, *Tusks*: longer, *Grinders*: with conic projections, *Feet*: with claws, *Claws*: subulate, *Food*: carcasses and preying on other animals. (✘)
* **Glires**: *Fore-teeth*: cutting, 2 in each jaw, *Tusks*: none, *Feet*: with claws formed for running and bounding, *Food*: bark, roots, vegetables, etc., which they gnaw. (?)
* **Pecora**: *Fore-teeth*: no upper, lower cutting, many, *Feet*: hoofed, cloven, *Food*: herbs which they pluck, chews the cud, *Stomach*: 1) the paunch to macerate and ruminate the food, 2) the bonnet, reticulate, to receive it, 3) the omasus, or maniplies of numerous folds to digest it, 4) and the abomasus', or caille, fasciate, to give it acescency and prevent putrefaction. (?)
* **Primates**: *Fore-teeth*: cutting, upper 4 parallel, (except in some species of bats which have 2 or none), *Tusks*: solitary, that is, one on each side, in each jaw, *Teats*: 2 pectoral, *Feet*: 2 are hands, *Nails*: (usually) flattened, oval, *Food*: fruits, except a few who use animal food. (✘)
So, I can only put it with: Belluae, Bruta, Glires, and Pecora. Or make its own division.
Now, Bulluae has horeses and things mistaken for horses. Bruta has a bunch of things classified wrong. Glires has rodens and rhinoceros for some reason. And Pecora got all the ruminants.
Since BOB is a rumiant, I'll say it is Pecora. But there is nothing on Pecora like it, so it will have its own division. Made up, of course.
The Taxnomy is as follows:
* Kingdom: Animal
* Class: Mammalia
* Order: Pecora
* Genus: Mactpora※
* Species: BOB
※: "Mactpo" Cortesy of [The Random Word Machine](http://randomwordmachine.com/).
Note: Linnaeus originally had "Quadrupedia" instead of Mammalia, which would have made things worse. In fact he had this "Paradoxa" for thing he didn't know where to put. I'm going with the final version he published. *Times has changed.*
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>
> Thus there are likely some more, maybe smaller hexaped-herbivores. There's likely to be some hexaped-rodents (e.g. hexarats which can climb buildings easily), as well as there are bound to be predatory hexapeds (at least some will have evolved to more efficiently hunt hexarats, let's call them hexacats).
>
>
>
If the staged digestive system is only incidental, they couldn't all be Pecora. Although, There is a problem. Because these hexacats eat exarats, thus they are not herbivores. In fact, they would be classified under Ferae.
We go from the field of antiquated taxonomy to the field of “necropsycology” anthropology: What would Carl Linnaeus think about these hexapeds?
Before Mammalia was stablished, there was Quadrupedia. So, it isn't hard to imagine Hexapedia as a class apart from Mammalia that would host all the hexapeds. In fact, since I consider mammary glands in these animals to be convergent evolution, I consider a separate class from Mammalia the correct solution for modern taxonomy (except the name is wrong, I haven't figured a better name).
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[Question]
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In a world I am working on, I have a wilderness-living, social, group-living species that for various reasons lacks access and ability to anything resembling modern medicine, including vaccinations. Yet, I want to keep it such that absent physical injuries, adults of this species very rarely become visibly sick or infirm, even when affected by what would ordinarily be relatively serious illness. The world they exist in is very much Earth-like, and might very well be Earth, but is not guaranteed to be Earth specifically.
These creatures are biological beings that evolved according to the theory of evolution as currently scientifically understood, with no superpowers, magic or "intelligent design" involved (except to the extent that I have an idea in mind and am working backwards to figure out how they might have evolved that way and if that is possible). I haven't yet decided on the exact form for this, but they have largely human-level intelligence.
**How can I arrange their environment such that adults generally do not become sick, and when they do, that the effect on the individual is generally limited such that they basically remain able to function at a level similar to that of healthy individuals while their bodies are fighting off the disease?**
It's perfectly acceptable and perhaps even good if *some* medical conditions cause a significant reduction in ability to function in some individuals (particularly very young and very old), but I want adults to for the most part be able to simply shrug off most illness.
Please don't just say "evolutionary pressure"; that's a given. Rather, *be specific* as to what could give the effect described. Bonus points for references and real-world examples, but any well-reasoned answer that would not break suspension of disbelief is welcome.
[Answer]
Although you can modify the environment, the best way to change things is often to change yourself. My point : change this species' **immune system**.
We humans have various difficulties facing diseases, due to our constitution, but certain plants do not have these difficulties.
Here is [a Wikipedia article](https://en.m.wikipedia.org/wiki/Plant_disease_resistance) about plants resistance to diseases.
---
Now, immune system isn't everything, you also have to **eat well**, **be happy**, **go out often**, and a few other things, as stated [in this wiki how article](http://m.wikihow.com/Rarely-Get-Sick)
Note that most of the pieces of advice in this article are easy to implement in your story, due to them living 'into the wild'.
[Answer]
## The antidote for any poison is always nearby
...the cure for any disease is also nearby.
It is a trope in some books (Discworld I think is one) where the poison and it's antidote are often found very near to each other. If one were to order a world in a similar manner, then even if an individual got sick they wouldn't endure any severe symptoms after taking the nearby cure.
## Evolution
If this world has a higher than Earth mutation rate in microbes/viruses/fungi then the immune systems of the creatures in that world will be optimized to identify and counter immunological threats very quickly and neutralize them. When everything that hits an immune system is new and lethal, the immune systems over time will get very good at countering those threats quickly.
## Evolution Combined!
Simply asserting in your story that a complex web of chemical and biological warfare existing in your world is plausible since modern science on earth is just now starting to get a handle on the biological interactions in stuff as simple as cheese. There are definitely complicated interactions between various plants and animals here on earth.
It is not unreasonable to assert that on this planet or in this ecosystem, it is beneficial for the poison and it's antidote to be close by. To use an earth analog, the antidote for botulinum toxin might be found by eating the mushrooms that grow on pig carcasses.
So, these creatures that can't get sick: they possess inspiringly powerful immune systems but in those times where the immune system is compromised, the antidote or cure is found in a nearby plant, animal or mushroom.
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A "wilderness-living, social, group-living" organism would (I assume) be in herds that move at the rate of their slowest member. If the slowest member is sick, then the herd will slow and that could be bad (predators, food source, climate, etc).
One stable strategy would be for the herd to turn on anyone sick and kill them.
Another stable strategy would be for the herd to help the sick in an altruistic, "selfish gene" way. How that is achieved practically is up to you - sharing antibodies via milk, slime or other bodily fluids; mobile immune system elements (something flea-like perhaps?); maybe the immune system is under conscious control so they can discuss and control how best to react.
[Answer]
To create an environment that minimizes disease within a “primitive” society, you need to discourage situations where pathogens can easily multiple or spread. The following factors can help:
1. Basic hygiene (i.e. bathe occasionally)
2. Basic sanitation (i.e. don’t
mix drinking water and waste)
3. Few, if any, domestic animals
4. Significant geographical distance from species’ point of origin
5. The climate is cold or otherwise inhospitable to the majority of pathogens
6. Contact between distant populations is rare (i.e. no Silk Road)
How do these help?
* 1 and 2 should be obvious; both are well known to prevent the spread of disease and eliminate conditions that allow pathogens to
thrive.
* 3 and 4 will vastly reduce the opportunities for pathogens to spread to your sentient species from another species; there would be
no hosts with a similar physiology
* As for 5, pathogens will have a
harder time surviving as a species if they can’t live outside a host
for long
* 6 is important for maintaining immunity; when distant populations interact on a somewhat regular yet infrequent basis (i.e. annually)
it provides plenty of opportunities for pathogens; it will mutate
within one population then spread to the other population that has
not had an opportunity to develop immunity to the new variant.
For an example of how these factors make a difference, compare the Americas and Europe in the Pre-Columbian era. All of the above factors were prevalent in the Americas, but far less common in Europe. (Regarding #5, it’s theorized that traveling through present-day Siberia and Canada killed off a lot of the diseases the first migrants would have brought to the Americas.) This disparity was a major factor in events such as The Great Dying, a massive plague that’s estimated to have killed as much as 95% of Native Americans in New England as well as many more throughout the Americas[1][2].
So, in short, a “primitive” society will naturally have few diseases without any special adaptations or accommodations beyond some basic hygiene.
1: <http://abbemuseum.org/research/wabanaki/timeline/great-dying.html>
2: <http://www.pbs.org/gunsgermssteel/variables/smallpox.html>
[Answer]
Provide the creatures with natural analogs of vaccines and/or antibiotics.
You could allow for more expansive capabilities to exchange antibodies from one individual to another. In mammals, this occurs but is limited to lactation. Invent a mechanism where once an individual survives a serious illness, they can transfer resistance to the rest of their group. This would seriously curtail endemic diseases.
For antibiotics, an idea could be to allow for symbiotic/mutualistic relationship with another species (of mold?). The individuals might maintain a baseline of the symbiont, and then "activate" it when under stress from disease (only activate when needed to avoid creating antibiotic resistant strains). A symbiont augmented immune system might plausibly provide "super" capabilities.
[Answer]
Most bacteria or virus-related diseases are flushed from the body in a manner of weeks, once the host's immune system has had time to mobilize and respond to that particular threat. The disease then only survives by constantly migrating from host to host (and perhaps mutating fast enough that after some hundred or so transmissions, previously infected hosts can be re-infected.)
Its *conceivable* that if everyone was just alone for long enough, all of these kinds of diseases would be absolutely wiped out, since they were unable to find new hosts before being defeated in their current hosts. (I want to link to the relevant XKCD What If, but I think this was only in the book.) A lifestyle where these individuals spent most of their time on their own would thereby likely lead to absence of communicable diseases.
Less drastic measures to do the same thing might simply involve making disease transmission less likely for these creatures- perhaps their upper respiratory tract is designed in such a way that they can't cough or wipe their nose on their hands. Remember that for a disease to continue to exist, the average infected host must infect at least one other person; otherwise, it soon dies out.
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Infectious diseases don't particularly want to kill their hosts, they just want to spread more and don't mind harming the host in the process. The most damaging diseases are recent introductions to the host from another species (e.g. HIV or Ebola in humans).
If you can arrange a long-term stable evolutionary environment with little inter-species interaction, then maybe diseases have just adapted so well to their hosts that they don't make them that sick but still spread.
That still leaves non-infections things like cancer or auto-immune conditions, but maybe this species is just resistant to those too - like some on Earth are e.g. naked mole rats never get cancer.
[Answer]
At some point in the (evolutionary) recent past, all animals related to this species were wiped out. (Think no other mammals aside from humans still existing.) It is difficult (though not impossible) for viruses to go cross-species, and the genetic distance won't help. Any viruses that would affect them died out shortly thereafter when they ran out of non-immune hosts, because there is little cross-group movement.
This still leaves bacteria and a few odds-n-ends, but could be a useful component.
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[Question]
[
First type - Fluorosilicones in Fluorosilicones, 400° to 500° C
Second type - Fluorocarbons in Molten Sulfur, 113° to 445° C
Third type - Proteins in Water, 0° to 100° C
Fourth type - Proteins in Liquid Ammonia, -77.7° C to -33.4° C
Fifth type - Lipids in Liquid Methane, -183.6° C to -161.6° C
Sixth type - Lipids in Liquid Hydrogen, -253° C to -240° C
The host star of this hypothetical planetary system is 0.80 (M☉), and 0.29 L☉
Now I need help creating the planets to support each biochemistry, I need to know the right mass for each planet, and the distance from the host star each planet needs to be to achieve the right temperature.
[Answer]
**First and second type:** ~0.2 AU
A Mercury-like planet. Mercury's surface temperature ranges from 100 K to 700 K, and a distance to the host star compensated for the different luminosity (just divide by 1.86) is very likely to be [Tidally locked](https://en.wikipedia.org/wiki/Tidal_locking). That means that the same side is always facing the Sun, causing different regions to permanently have the Sun in the same position in the sky. The hottest part of the Sun-facing hemisphere should easily reach the temperature required for fluorosilicone life, and closer to the terminator, fluorocarbon life may thrive (alternatively, use a Venus clone for this one). The dark side does actually then have low enough temperatures for 3 and 4 too, but unfortunately no sunlight.
**Third type:** ~0.5 AU
We know this one works :) The safest option is an Earth clone with scaled distance.
**Fourth type:** ~0.8 AU
"wet Mars" or "Mars with volatiles". The current surface temperature of Mars fits perfectly for the liquid ammonia case, but the planet should have a little more mass and a stronger magnetic field in order to prevent an atmosphere from escaping.
**Fifth type:** ~5.1 AU
The obvious comparison here is [Titan](https://en.wikipedia.org/wiki/Titan_%28moon%29), but it does not necessary have to orbit a gas giant. At this distance, you are very free to choose the size you want, as there are very easy to hold an atmosphere.
**Sixth type:**
A tricky one. Liquid hydrogen is **really** cold. Even Triton, the largest moon of Neptune, is too hot. I can only say that it then must have a orbital distance of >10 AU.
One interesting thing to note is that a tidally locked world could in theory support most of the listed biochemistries (perhaps except for liquid hydrogen, that stuff is ridiculously cold.):
[](https://i.stack.imgur.com/REqSDm.png)
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I've heard a lot of people say that having two tidally locked planets close together would have adverse affects on both planets. I have two tidally locked planets at a distance of 16,550 miles apart. Or, about 26635 kilometers apart. Both planets are about earth's size, with a similar composition, but one has about 85% and the other 60% of the surface covered in water. (Including polar ice caps.)
How would this affect the conditions on each planet? I believe I've heard that there would be more tectonic activity, and there wouldn't really be tides, and that the water would be pulled towards the opposite planet. How much truth is there to these statements, and what other effects can I expect?
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There won't be any tides. The tidal bulge or bulges will be fixed features. Sea level will be higher in some parts of the world's and lower in others compared to how it would be without the companion planet. This will be of no interest to any inhabitants other than a few physics students.
Tectonic activity might start to decline once the planet's get locked ... Over a timescale of hundreds of millions of years. Tidal drag is not the only motive force. Heat from radioactive decay and (possibly) phase changes in the planet's core also provide energy. You can make these drive tectonics if you want to.
The big thing is that it's hard to see how you could get a locked pair of planets with anything like 24-hour-short days. More likely month-long days. That has major implications for weather, climate, evolution. How to survive two weeks or longer of continuous night over an entire hemisphere?
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OK your planets are 26,350 km apart (reduced the number fractionally to make the numbers easier), but they have diameters of 12,700km. So the closest point of one planet is only 20,000km from the centre of the other one, while the furthest point is 32,700km away.
We know that the planets generate 1g at a distance of 6,350km from their centres, because they're the same as Earth. So at 20,000km they generate 0.101g, while at 26,350km it's 0.058g and at 32,700km it's 0.038g. Therefore, you're about 4% lighter at the point directly under the other planet, and about 2% lighter at the point directly opposite it, probably not enough to notice but easily measurable even with primitive technology.
The whole of each planet will be stretched by the differential gravity, and they will bulge towards and away from each other. But their hydrospheres and atmospheres are less rigid and will bulge more, resulting in deep oceans and thick atmosphere at the points under and opposite the other planet, and probably no water and thin atmosphere on the circle in between those two points.
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You are very close to the Roche Limit, if not inside it.
A planet has no structural strength on a large scale. Gravity is the only force holding it together. Consider two rocks, one on the surface closest to the other planet, one on the furthest. Now these rocks are in different orbits. The inner one, if the planet wasn't there, would be in a faster orbit that the outer one. It's not going fast enough, so Mg is bigger than v^2/R.
<https://en.wikipedia.org/wiki/Roche_limit>
<http://abyss.uoregon.edu/~js/glossary/roche_limit.html>
Robert Forward did a pair of books, Roche World and Return to Roche World that takes place on such a binary planet. As I recall he did a good job with the science. (He was a physicist)
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The year is 2120, and the world is (depressingly/refreshingly) similar. Sure, technology has advanced and there are flying cars, trains run through voided tunnels at 1000 mph and scramjets take the rich from Canberra to New York in 2 hours, and our virtual personal assistants ("Jeeves") often appear smarter than their owners. The unemployment rate hovers at a steady 70%, but with all the automation and the universal guaranteed personal income, that's not as terrible a thing as one might think. True Artificial Intelligence has proven elusive, and after (what even later history books would call) the War of the Lesser Abominations, AI research is at this point forbidden across most of the civilized regions of the planet, and a well-funded AGI Taskforce roams the slumlands hunting out rogue AI developers.
The one notable feature of this world that I'm interested in for the purpose of this question is that most people can expect to live to 200 years, with life expectancy growing at just under 1 year per year for much of the past century. Dementia, cancer, heart disease are quaint things of the past century, with suicide, accidents, and engineered viruses now the largest killers by far.
**What would the implications of a 200 year lifespan be?** I'm thinking specifically:
a) **Career** - would getting multiple PhDs become the norm for a well-educated member of the body economic (a.k.a. any employed person)? Would career progression be stifled by dinosaurs that won't retire or would innovation be instead boosted by the extra willingness to devote a decade or two to a risky project?
b) **Family life** - would dating one's grandchildren's friends be regarded as normal, and would marriages become limited-duration contracts?
c) Is there anything major that I'm overlooking? Yes, I'm aware of the concept of undying tyrants, and will not be pursuing it directly here.
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## Career
**Stagnation is the name of the game.** If you've ever tried to change processes when your manager has been doing things the same way for 30 years and it's always been fine in the past, imagine what it would be like when it's been done the same way for 130 years. Asking for 5 years industry experience? No, now you can ask for 30 years experience. New tech? No way, if it ain't broken... Young people are going to remain unemployed until their children have grown up. Your kids will be at Uni by the time you've got the steady career that you've only just got into in your late 20s/early 30s, which may even become your late 50s early 60s. What's the rush anyway? You'll be doing it for another 100 years.
## Family
This largely depends on the importance of family in the culture you come from. Marriage might as well be a limited term contract as it is. Some people will partner for life but the majority will done by 20 years or so. Relationships will apply to specific periods in your life, rarely carrying over to the next stage. Early ones for fun, then a steady one for reproduction, moving into a career growth relationship, before a steady one again when you settle into a specific role, finally a retirement relationship for travelling and some old age fun.
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Family? This partially depends on ability to procreate. Currently women have a limited time frame and in this scenario it would be the first 1/4 of their lifetime. This of course can be 'overridden' even with today's tech but there might be other issues for even a healthy 120 year old woman having children.
Men have other issues, though medication helps with some, the problem is that the older either or both biological parents are the more likely of genetic issues, such as Down's Syndrome. Maybe by then most pregnancies would be shifted through to ensure 'normal, healthy' children, kind of like [Gattaca](https://en.wikipedia.org/wiki/Gattaca).
Though with such a long life, one thing I think could happen, is that the 'young' people 20's-50's might produce children for the older generation. Have a child, and let older people raise the child, and you continue living your life unencumbered, visiting your kids like they might be siblings. Completely rewriting family dynamics.
Career? I suspect those who need to be busy will work until they die. Those that like to learn will have several doctorates. And the many of the rest will be allowed to follow our interests to where ever they lead. Many people today would try and do many other things than what they get paid for, if they didn't need to earn money to live. I'm a woodworker, and becoming a blacksmith, I also review books, but I make my living as a software engineer, which lets me do those other things, so I have to fit them in around my work schedule.
200 years to perfect something also could improve many different technologies. But it also allows for incorrect thoughts to live much longer. Many scientific paradigm shifts don't usually appear. They become more accepted as the old school retires and dies out. If they stay an extra 40-50 years in a field it could severely hamper that field of study.
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150 years ago the expected lifespan was around 40 years almost half than what it is now.
People 150 years ago were getting married in their teens, now they are getting married in their mid to late 20s and not it's not uncommon to wait until 30 and over, with 200 year lifespan, people might wait until their 50s or 60s (given that they can still have kids at that age).
Average education has also increased significantly, not only due to longer lifespan, but also due to more complex industry that requires that higher education. I don't see any reason for that to stop. People might decide to travel more, explore, have a "fun" career (bartender on a tropical beach anyone?) for a few years before they go back for PhD and research.
I don't think dating wise anything will change that much. There would be a much larger dating pool but I doubt a 150 year old dating a 20 year old will be that common, people change as they age a 50 year old will not be interested in doing the same things he was doing when he was 20.
Politics will be much more stagnant. Many politicians are in office for life even now, imagine how bad would it get if they lived 200 years on average...
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**Life in Academia Would Be Hell**
As someone who knows academia, I can tell you that an extended lifespan would make academia a heck of a lot worse. Academia right now works on a "dead man's shoes" principle. Career positions are so rare in many fields that getting a professorship position is often heavily dependent on the people ahead of you dying and opening up a position. If everyone lives to perfect health in their 200s now career opportunities no longer open up because older researchers just. won't. die.
This would also make getting a liberal arts degree or something similar an even worse career proposition than it is now. Normally, if you get a liberal arts degree or something else that has very little pragmatic value, there is always the potential of getting a job teaching in your field of choice. With people living to 200s, there is much less of a chance of that.
Tenure might also disappear as a concept. Tenure was mostly a mechanism such that older employees (who were assumed to be more knowledgeable about the workings of a university) could be more vocal with their criticisms or propose more controversial ideas and the universities couldn't just outright fire them just because they didn't like what they had to say. The assumption being that these professors wouldn't be around long anyway because they only had ten or twenty more years to live. But if people lived into their 200s, tenure suddenly becomes a lot more expensive (who wants to pay the salary of that one absentee professor for a century?) and colleges now have a lot of reason to abandon the practice.
This, in turn, would lead to an increase in stagnation in the sciences and humanities. Older academics that just. won't. die. will stymy scientific and social progress by impeding research that potentially threatens their pet hypotheses. Academics do this all the time today, by trashing grant proposals they don't like or giving nasty reviews to papers that disagree with them. That is if they don't just outright abuse their power by preventing people from conducting research that disagrees with them (I've seen this numerous times).
On top of that, radical scientific advances like evolution, catastrophic dinosaurian meteor extinction, the dino-bird connection, or plate tectonics only become widely accepted because all of their major opponents *die*. The initial opponents of the hypothesis become too emotionally invested in opposing the hypothesis and are unable to revise their worldview. Changing their opinion would be a loss of face, and they've invested too much to back out. Opponents of major hypotheses like Larry Martin and the dino-bird hypothesis or G. G. Simpson and plate tectonics never change their minds on the subject, they just died and opened the field to younger researchers who didn't have the emotional baggage associated with the debate and were able to look at things more objectively. If people lived to be 200 you would see tons of disproven hypotheses sticking around because some scientist is wedded to their pet theory, and you would get bunkum like orthogenesis sticking around to the present.
**An Extreme Societal Shift Towards Conservativism**
Older people tend to be more reactionary and prefer how things were "in the good old days". In general, across the world older people tend to vote for the more conservative/traditionalist political parties over more liberal/progressive ones. This kind of mindset seems to be increasingly adopted starting in what is now middle age when people have been around long enough for what their culture considered "hip" when they were young to be considered old and cliché by the younger generation (the "dang whippersnappers" effect). In modern society, this is offset by the fact that the old people tend to *die*, meaning politically younger voters and older voters are relatively balanced.
You've just set up a scenario where the old fogies outnumber the Young Turks by potentially as much as four to one. On top of that, they have an even louder voice because their numbers aren't thinned by dementia and other geriatric disease. As a result, in a democracy, the old timers are always going to win in political elections. Politicians also have much less reason to appeal to younger voters by including reformatory or progressive ideas in their political platform because the majority of their base are old people.
One might say that with an increase in lifespan the cutoff age for "old fogie" might just increase to seventy or eighty. But in reality all this might do is create age "strata" where certain age groups hold certain values, instead of an "old/young" divide. And the older age strata would still be more likely to be conservative, the shift seems to be relative to how many years lived and the passage of time more than anything else.
**Immortal tyrants shouldn't really be a problem**
Most modern democracies have laws in place that allow people to only rule for a few terms. Those that don't already have problems with leaders staying in power for long periods of time even without a 200 year lifespan.
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Mycolaria is my working name for an alien planet featuring a much more visible role for fungi of all kinds, large and small. There are also animals and plants on this world. This is the second in a series of fungi-related worldbuilding questions.
This particular mushroom related question is about radiotrophic fungi, which are able to make use of radiation via Melanin to power their own growth. These have been observed on earth, e.g. at Chernobyl.
I am looking for input on whether/how an animal species could enjoy a symbiotic relationship with radiotrophic fungi so that they can survive in a planetary environment which is afflicted by levels of surface radiation anywhere between 3 and 100 times that experienced on earth.
While an affirmative answer may well not be forthcoming, I am interested in biological issues surrounding this question.
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3 to 100 times Earth background is not a lot. The [world average is about 3mSv](https://en.wikipedia.org/wiki/Background_radiation) per year. [People in places like Ramsar, Iran have a yearly dose of up to 260 mSv](http://www.ncbi.nlm.nih.gov/pubmed/11769138) with no reported ill effects. You will need to bump that up even more so you end up at around at least 1 Gy/year. But that is just petty details... you can pick an arbitrary number.
To your question: the beneficial effect would be...
1. the symbiotic partner can make use of the fungi's DNA repair mechanisms. Some species have exceptional [DNA repair](https://en.wikipedia.org/wiki/DNA_repair) and can survive massive doses thanks to that. The bacterium [Deinococcus Radiodurans](https://en.wikipedia.org/wiki/Deinococcus_radiodurans) ("Terrible berry that endures radiation") can survive doses of radiation that are 5000 times higher than what causes acute radiation sickness in a person.
In your universe, you can have a fungi that allows the symbiotic partner to make use of this repair mechanism for themselves.
2. the fungi can have a shielding effect by hosting substances that have a high [nuclear cross section](https://en.wikipedia.org/wiki/Nuclear_cross_section). This would be useful if you had natural neutron radiation.
EDIT: As requested, let us go deeper into this.
Actually what you wrote in your original post is hitting close to the truth already. There has been some interesting research results from the Chernobyl area that suggests that animals can actually adapt to a higher-than-normal radiation environment. And it is assumed that *anti-oxidants* is the key.
Bank Voles - who have now bred for over 50 generations in the area - show no ill effects of living there. They even show slightly higher then normal resilience when subjected to even more radiation. It is thought that *anti-oxidants* play a key part in this. The radiation is causing *oxidative stress* and the vole's body responds with producing more anti-oxidants (or as the article suggests: producing less of red/pink pheomelanin that otherwise use up anti-oxidants). You can read more about it [here](http://www.nature.com/articles/srep07141).
In your world, the fungus may have its own version of photosynthesis - or in this case perhaps we should call it radiation-synthesis - that make use of the highly energetic radiation photons to produce a surplus of particular anti-oxidants that can be absorbed by the symbiotic partner and put into use to defuse the free radicals caused by radiation before they can damage DNA.
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A lot of radiation induced damage to DNA doesn't come from "direct hits" of the DNA. When ionizing radiation hits water it forms peroxides which are fairly stable in the body, but which can then form hydroxyl radicals. These super-reactive molecules can then cause damage to the DNA if they come into contact with it. All of this information can be found here: <https://en.wikipedia.org/wiki/Free_radical_damage_to_DNA>. While this isn't directly related to melanin, high levels of radiation will cause the formation of lots of these peroxides and its possible an organism could utilize them as energy. This [paper](http://rsif.royalsocietypublishing.org/content/12/109/20150366) suggests hydrogen peroxide was an energy source for early self-replicators. A symbiotic fungus that efficiently scavenged the harmful hydrogen peroxide molecules from an animal could reduce the mutation rates in that animal substantially while also deriving energy from the molecules.
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The trouble with radiation is that it gets everywhere. Sure, you may have a 'fungus' that can fuel its metabolism with radioactives, but whatever it is in a symbiotic relationship with would have to be similarly radiation-resistant. Radiation isn't going to always pass through the fungus first.
I.e. don't expect a human - or his dog - to be able to get infected with this stuff and be any less vulnerable to radiation poisoning while their immune systems try to fight off the alien invader in their bodies. A terran plant - since their immune systems are so basic - is a possibility for an alien symbiosis. Pretty much any organism that this 'fungus' is - or could be - a symbiote with would most likely have evolved alongside it.
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In a future age of technology and machinery, humans no longer need to perform physical grunt work.
The most menial of jobs are performed by very simplistic machines. These are not learning or intelligent AI, they are simply robots.
The jobs which require problem-solving or other characteristics which cannot be done by simple robots have been abstracted into various games. We had once depended on incredibly intelligent problem-solving AI, but they turned against us and we no longer trust computers to make those level of decisions anymore.
On any given day, a person can fire up their favorite game - or even a new one. They can participate in practice sessions, which don't count towards their score. In fact, in all games it is required to reach a certain level of proficiency before being allowed to play in a way which influences your score. If you were to play a regular session and fantastically failed for whatever reason, the cost of the failure is taken out from your score.
Your score is very important. It is essentially your money - and it is what you trade for goods or services.
Obviously, some games will be more popular than others. The importance of the game being played is always weighed against the number of people able and willing to play it. - In this way possible score values can be manipulated to encourage players to play games which need more players.
Are there obvious drawbacks that I need to account for in this setting?
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**This is essentially an attitude shift away from how things are now.**
But with some significant drawbacks.
If people considered their current jobs as games, the concept would be the same. There are finite jobs/games available, because there are limited positions/robots capable of working at the same time. You have to be qualified to work/play at a certain job/game. You earn money/points for working/playing which you trade for goods and services.
The main difference is that work is done remotely, through a [robotic surrogate](http://spectrum.ieee.org/robotics/humanoids/the-reality-of-robot-surrogates). There is some work on this, the [telepresence](https://en.wikipedia.org/wiki/Telepresence) aspect, in regards to elderly care and tourism. Even [Apple sells a telepresence robot](http://www.apple.com/shop/product/HE494LL/A/double-telepresence-robot). Moving from straight telepresence to gamification is simply an abstraction on the reality of the situation.
The drawbacks would be things like:
* Child labor law violations. People could teach their children the
simpler games and have them working rather than going to school.
* Hacking of other people's accounts to cause damage and get that
person banned from that game (fired). Personal responsibility in
general may be called into question.
* Connection latency could come into play for timing sensitive jobs like communicating with other humans or navigating traffic.
* It also removes humans from what is really happening. It makes things
*unreal* to people. Certain jobs would be dangerous for bystanders
if the person keeping them safe, driving them home, or operating
heavy machines was disconnected from the danger in what they are
doing.
In summary, for *all* jobs to become [gamified](https://en.wikipedia.org/wiki/Gamification) would be a disaster. But to limit it to certain simple jobs no one wants to do already is *brilliant*. It could be similar to a service like Uber. Regular people could log in to a time-multiplexed robot and perform simple tasks through a game like interface. It may even be advantageous to use multiple people on a single session to make sure a single person doesn't have full control. Like a pilot and copilot system. These people would be rated on their work and a higher rating would allow for higher priority on jobs while a low rating could result in a banning from the system.
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You need to account for **Supply vs Demand**.
Certain games will be more popular than others. The popularity of games will almost certainly not line up exactly with the amount of work that needs to be done. Some games you'll have way too much work done, some you won't have nearly enough.
You could balance this with a smart system that gives point multipliers to high-demand jobs (this smart system could, itself, be another game). In general, you should also try to ensure that more people play the games than are needed, since if you drop below the required amount in certain jobs - like say, for a nuclear safety technician - things might get ugly.
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One obvious drawback is people cheating or even hacking the games. This would manipulate their score, serve no benefit towards the workload and undermine the whole system. You can guaruntee people would try to do this. I guess you'd need extreme surveillence to prevent them.
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Hmmm, I would consider what kind of games and outcomes people would play for such a society to evolve. Are they 'win lose' games? No, how could all of society work with inner competition, who would lose in society so others can win? So for society to evolve games as work - they are likely to be 'win win' games which require large scale participation, thus requiring a large work force to even exist.
Think 'Bucky Fuller's World Game'. Every player has access to billionaire wealth via resources, but only when they play the 'win win' game.
Fun question!
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One thing that might happen is change in the perception of work -- as well as games. When a "game" determines how you are able to live by being the source of your income or can lead to IRL penalties (i.e. fines and so on), then I think it will stop being a game, but simply become a different sort of work.
In such a future, "secretary", "construction worker", and "Lv 79 Dark Elf Wizard" are all equally valid and recognized job titles / positions. If your next paycheck was decided by whether your avatar could dig up some digital ore or not, then the difference between digital mining and actually going into a real mine with pickaxe in hand is reduced.
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For a civilization like this, firstly, I would like to know what dangers there are, e.g: radiation, cave-ins, temperature. I also want to know about the sustainability of this colony, power I'd imagine isn't a issue (geothermal), but how would there be a sustainable source of food? What about mental affects, I'd imagine that the whole *lack of sunlight* could cause chaos for the brain, but maybe there are other side-effects on being underground, that would cause problems in the brain.
Finally, factoring in all the dangers and requirements of a colony, could this colony even exist (don't worry about how they got down there), and how far underground could this colony even be? The technology is roughly current day, maybe a little bit further into the future, and the colony size is whatever the situation you come up with can support.
Bonus Question: For the chosen depth, what would the geology be? Would it primarily be rock or quartz? What ores would there be, and in what quantities (roughly)?
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Let's review a little thermodynamics - all heat engines require a heat sink in which to discard entropy. If they do not discard entropy, the system runs for a bit and subsequently fails to function. This means a couple of things - for your geothermal power solution to work, you need to reject heat somewhere, probably the atmosphere far above the colony, or maybe the ocean. Assuming you got that to work, you could then overcome the next thing that's going to kill you, and that's temperature.
Even with the wildest shielding, that shielding will eventually come up to the temperature of its surroundings, and your colony will get uninhabitable very quickly. The entire colony is going to have to be carefully air conditioned to prevent lethal temperatures, and the shielding should probably be liquid cooled. All of the heat absorbed by the shielding and the A/C system will have to be rejected back to your heat sink.
Handling the wild pressures at depth is the next thing we need to fix. If we are deep down and still have an open air connection to the atmosphere, it will kill everyone; periodically, we'll need to have air locks between levels so that pressures can be independently controlled. This is another problem though - if we don't have a connection outside, we don't have a way to ventilate. We'll need to generate oxygen and scrub toxins and CO2 from the air. There is no better way to generate oxygen than hydrolysis of water, but we'll need to get rid of the hydrogen produced - if we try to use it in any way, we just lose the oxygen we made, which we needed. So we use compressors to pump excess, unwanted hydrogen to the surface. Scrubbing the atmosphere takes, well, a scrubber - this machine uses a heater and a catalyst bed to absorb toxic substances.
For this to work for any length of time, the colony must be able to sustain itself - food, water and scrubber catalyst will be needed for continued operation. Water reprocessing is a must - your air conditioners will also be feeding into collection facilities. Crops will have to be grown under UV lamps in imported dirt. And to make your own scrubber catalysts means you'll need to be able to manufacture advanced materials underground.
On the whole, this is not actually possible with modern day tech. Our deepest mines right now extend some [4 kilometers below the surface](http://en.wikipedia.org/wiki/Mponeng), but have extensive surface support. The entire colony would have to be built in some kind of "goldilocks" zone where it conveniently didn't take on massive amounts of toxic subsurface gases by the hour, and had a freely available, easy to access heat sink, without having to worry about said heat sink breaking through the roof over your head and drowning everyone.
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# Linked
[What would the flora on a methane world be like?](https://worldbuilding.stackexchange.com/questions/14384/what-would-the-flora-on-a-methane-world-be-like)
[What would animal life on a methane world look like and how would it evolve?](https://worldbuilding.stackexchange.com/questions/14316/what-would-animal-life-on-a-methane-world-look-like-and-how-would-it-evolve)
[What would the conditions on a methane world be like?](https://worldbuilding.stackexchange.com/questions/14312/what-would-the-conditions-on-a-methane-world-be-like)
[How would an intelligent race on a methane world achieve a fire equivalent?](https://worldbuilding.stackexchange.com/questions/14383/how-would-an-intelligent-race-on-a-methane-world-achieve-a-fire-equivalent)
# Question:
**How could an intelligent race on Titan (a planet like it, anyway) achieve space travel?** It might be helpful to look at some of the linked questions for ideas.
**Edit:**
In response to the comments I am looking for chemical reactions and the force needed to escape the higher pressure and g's on Titan.
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# Important Factors, Assumptions
This answer is going to *totally ignore* all the groundwork needed before a species can even dream of space travel. We're going to assume some intelligent form of life evolves on Titan, and that they want to get off of their moon and explore all the things in their sky. (Which they wouldn't know about, because Titan's Atmosphere is [opaque at many wavelengths](http://en.wikipedia.org/wiki/Atmosphere_of_Titan).)
[Titan](http://en.wikipedia.org/wiki/Titan_(moon)) has:
* An escape velocity of 2.638 km/s (compared to 11.186 km/s for earth)
* A mostly nitrogen with some methane (1.4%) atmosphere
* A smattering of other chemicals (such as hydrogen, hydrocarbons, etc.)
* Higher surface pressure of ~1.45 atm.
* A Surface Temperature of ~94 K; that's *cold*. Cold enough to store liquid gasses.
# Rocket Engines
Here are some [demonstrated to work rocket engines](http://en.wikipedia.org/wiki/Liquid_rocket_propellant#Bipropellants) they could use:
* Methane
* Oxygen + Hydrogen
* Steam Rockets (a type of [monopropellant](http://en.wikipedia.org/wiki/Liquid_rocket_propellant#Monopropellants)).
It should be noted that these are just a few rockets which are possible. There are many [types of rocket](http://en.wikipedia.org/wiki/Rocket_engine#Types_of_rocket_engines) these aliens could go for. The significantly lower escape velocity means that they have more options practically open to them.
Getting the liquid oxygen oxidizers, which many chemical rockets require, would be hard, but not prohibitively hard. They could decompose the water they have to make the hydrogen-oxygen rockets. Furthermore, they can store them on the surface without needing coolant. They could grab a bunch of air to power their steam rocket. This also ignores the other nifty rockets out there, such as light beam powered rocket or nuclear gas core rockets. There are other ideas, too, such as [scramjets](http://en.wikipedia.org/wiki/Scramjet#Advantages_and_disadvantages_for_orbital_vehicles), which they may take advantage of to get to orbit.
Really, it seems the aliens in question would need to answer: what rockets do they feel comfortable with? They have options, and can easily choose between many of them. Sure, Titan itself presents problems, but they can be overcome.
# What about that Atmosphere?
According to [Robert Zubrin](http://en.wikipedia.org/wiki/Atmosphere_of_Titan#cite_note-Zubrin-7), if you found yourself on the surface of Titan, you could fly by attaching wings to your arms and flapping. Flying is not as energetically difficult as on Earth. You could easily have a craft get into the upper atmosphere and *then* use the engines to get into orbit or achieve escape velocity. So yes, you would not want to rocket your way from the surface to orbit, but you could easily fly up to a point where it would make sense to rocket out. You can hear about the Cassini-Huygens mission and some of the challenges presented by the atmosphere in this [presentation by Elizabeth P. Turtle](https://www.youtube.com/watch?v=cfCTmv-9GkE).
I suspect the thicker atmosphere mostly means that launch vehicles will simply fly up through most of the atmosphere, and then launch a payload into orbit.
# Rocketry on Titan is Easy
The thicker atmosphere makes getting higher up easier, and the lower gravity makes escaping that atmosphere easier. You can synthesize oxidizers from the ice, or use one of many other rocket options to get out. The cold surface temperature even means that fuel containment tanks need not be cooled, and that's further energy savings!
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What about a railgun? They need refined metal and a source of electricity. <https://en.wikipedia.org/wiki/Railgun>. I would assume that you could build a longer track and adjust amperage to keep G forces survivable. The track might be more durable than on Earth. Earth has an oxygen rich atmosphere that is oxidative. A nitrogen/methane/ethane atmosphere would be reductive and therefore no rusting. However, the cold will make things more brittle. On the other hand a "room temperature" superconductor will be easier. There are superconductors at -135C, and Titan is already at -179C.
The railgun could work for satellites that do not necessarily need to move. Fine-scale placement could be provided by small solid or liquid thrusters.
The chemistry that works on Earth will work on Titan. So hydrogen + oxygen will produce water. However, the cold will slow reactions and make all metals more brittle. With little oxygen in the atmosphere things will not burn. Depending on how much methane is present one might be able to carry oxygen rather than hydrocarbons to make engines. So rocket could work, or something like a high altitude aircraft that carries a final payload that gets boosted into space.
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Titan's surface is primarily made of ice, which is just oxygen and hydrogen. They could extract liquid oxygen from the ice. Titan is a typical methane world, so ice should not be hard to come by. And the boiling point of oxygen is only 10 degrees lower than the ambient temperature on Titan, so it could be stored in a basic home freezer. There are plenty of fuels on a methane world, you could even just use the atmosphere or liberated Hydrogen.
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I'm working on a space-fantasy setting and one of the cosmological quirks is that the cosmos, instead of being a vacuum, is actually filled with a gaseous substance. As a result, the entire cosmos is essentially an infinitely large nebula. The ether, which is silvery in hue, in addition to being aesthetically pleasing, helps justify certain space opera tropes, such as relatively close range combat at relatively slow speeds; perhaps even fighter craft. The ether is quite abrasive; anything moving through it is subject to a considerable amount of friction. It also diffuses coherent beams far more than a planetary atmosphere. The ether becomes darker and more condensed the cooler it becomes. Imagine that people could look out from their ships into the dark and eerie "deep ether".
How dose the existence of an all pervading ether effect the lives of the people living in this cosmos? What dose the sky look like?
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I'm going to ignore all the huge issues with physics with that much matter flowing around. (including the friction on the planets slowing them down to fall into the sun, it would also tend to displace large amounts of the planets atmosphere, that's still ignoring most known physics anyway.)
So what to see?
I'll start with the convection currents around the sun. There would be large amount of matter pushing away as it is heated up and somehow it would have to be flowing in to replace it. So there would be some kind of pattern in the sun probably visible by the naked eye. Warmer ether flowing away, cooler ether sinking in to replace. You would likely be able to see the convection taking place, it would also diffuse the light a lot more making the sun appear huge in the sky.
light would be dimmer, but more warmth would likely arrive by direct matter transference, like the heat vents in a home.
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*Relatively* close range combat at *relatively* slow speeds are already taken care of by the vastness of space and inertia. It will already take a very long time to get anywhere with a speed limit of *C*, there is no need to decrease it further.
Additionally, if you *add friction to space* then you can no longer have orbiting planets. Try swinging a ball around on a string in the air and see if it goes on long enough to evolve life. Evolving life is especially problematic if you've blocked, redirected, diffused and otherwise reduced the energy of all the light getting to a planet.
It seems unlikely that a race would ever try to get to space at all. By [all accounts](http://hitchhikers.wikia.com/wiki/Krikkit) if a race can't see the stars, then they won't try to reach them. What would they do if they got there? The interplanetary void would essentially be an endless bank of *space fog*, a race could travel for generations and would never see another planet (not that they have any reason to think others exist).
So, if life could develop anywhere at all, and if they ever had a desire to travel into a seemingly endless void of *space fog*, they would never meet another race to do combat with.
**I have an alternative**. Contain your 'ether'/space-fog to a solar system. The planetary paths should be kept clear in order to allow orbit without space-friction. The silvery hue belies the properties of the space-fog that allow it to keep from falling into the star. It's harvested for solar sails and hull plating. It is, in fact, so valuable that space-faring civilizations come from all of the local systems to harvest it for use in their recreational solar-sailboats and sun diving combat fighters.
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Took a bunch of comments to flush out this answer. You are in 'handwavy' physics here and if your audience wanted to, they'd probably pick these thing apart. If the audience is in for the fun of it...Star wars exists doesn't it? Will try to keep in that frame of mind for the answer.
Here is my solution:
Have the viscosity of ether related to gravity. A higher gravitational effect (lets say mercury sized or larger) produces enough of a gravitational effect to negate the viscosity of the ether (yes, the solution is hand wavy, but so are the properties of dark matter, why can't gravity effect how 'solid' the ether is). The end result here is planets and planetoids can keep an orbit, and you will still have your ether. Better yet, you'll have area's of extreme viscus ether between planets and in microgravity space. A little hand wavy, but it works...a gravity field applied to ether lowers viscosity to near 0. It's also possible to have the viscosity of ether related to the speed of whats travelling through it.
Detecting changes in the viscosity of ether over distances would functionally work as a gravity scanner...pick out large gravity objects by detecting a change in the ether...maybe?
This would also mean the gravity of earth would keep the viscosity of ether down so the moon is a viewable object and people can reach for the moon (maybe not the stars)? Satellites also remain feasible...and it would also mean that a plane couldn't just fly to the moon as the gravity of the moon and earth eliminate the thicker ether there.
And to continue along these lines..the suns gravity could then be explained on how to keep the sunlight reaching earth. You might have to bring earth significantly closer to the sun, but if the ether was thin around the sun you would simply have the planetary golidlocks zone close to the sun.
Remember that from earth only the sun, moon, and maybe venus at the right time of year is all that will be perceivable. Everything else will be blackness. Star light, star bright, I'll never see a star at night?
Comets and asteroids will be an odd phenom...they would slow down as they traveled (especially through deep space) and eventually slow to the point that they'd drift into other planets gravitational fields and eventual collision (maybe a moon?). Asteroid fields might not be feasible...same issue where they come to a halt in the ether and slowly collapse (our asteroid belt would go into the sun). Would there be a big change in Earths development if it was never struck by meteors? Your call
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I define "Venusian world" to be high pressure, thick atmosphere, and high temperatures. Assume the atmosphere is similar to Venus, but whatever gets the same effect and supports life is fine.
I'm envisioning a six-limbed sentient species that's nearly blind and uses sonar to "see", and a primarily fungal-like plant life, with possibly some air-based floating life on the top surface, though small and non-sentient.
Would it be possible to have (water) oceans in this sort of planet and would it be possible to have water/carbon-based life forms?
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Here's some information about [Venus](https://en.wikipedia.org/wiki/Venus):
* **Surface gravity:** $8.87 \text{ m/s}^2$
* **Surface temperature:** $737 \text{ K}$
* **Surface pressure:** $\approx$ $92 \text{ atm}$
So no liquid water on the surface.
Wikipedia also mentions later on that you have to get 50,000 meters in the air before conditions become something like Earth (i.e. temperature and pressure are somewhat survivable). That gives us a nice little loophole. A little searching on [Wikipedia](https://en.wikipedia.org/wiki/Colonization_of_Venus) showed that someone else had had the same idea I had: floating colonies:
(*[Artist's rendering of a floating habitat](https://upload.wikimedia.org/wikipedia/commons/6/62/Venusballoonoutpost.png)*)
Now we're getting somewhere.
Once more, I go back to my [pufferpolyp](https://worldbuilding.stackexchange.com/questions/2856/life-on-a-planet-with-multiple-gas-layers/2868#2868), a floating creature that has an air sac carrying lifting gases. It floats along on its merry way, essentially staying at the same altitude for all its life (although when it dies, there's a chance its air sac will deflate and it will fall 50,000 meters to the surface, where it will be crushed and roasted).
Anyway, my life of choice is this pufferpolyp. Unfortunately, the amount of oxygen in the Venusian atmosphere is next to nil. Instead, there's plenty of $\text{CO}\_2$. That gives us a little loophole. 50,000 feet should bring you above the clouds of sulfur dioxide, meaning that you might get some sunlight. So this pufferpolyp can use photosynthesis!
After a long time, if enough pufferpolyps are around, the upper atmosphere will turn to a less hellish mixture and could become an atmosphere of oxygen and nitrogen. Will the pufferpolyps die? Maybe; maybe not. $\text{CO}\_2$-breathing life on Earth survived the [Great Oxygenation Event](https://en.wikipedia.org/wiki/Great_Oxygenation_Event) 2.3 billion years ago. I think they'll survive. Bacteria might be able to take in oxygen and put out $\text{CO}\_2$.
And if the pufferpolyps have been "deployed" by another race intent on aerial colonization . . . there's going to be a lot of changes happening soon.
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There's no way that something as weird as a pufferpolyp could develop in such a hellish place. Most living things aren't born floating 50,000 meters in the air, and this is no exception. The things couldn't have floated up from the surface because they'd be squished in about 10 minutes down there. So my cop-out is that they've been put there by a race (humans?) intent on terraforming the planet, starting with the upper atmosphere.
That's not to say that it's impossible for things to live and evolve in the sky. [Bacteria have been found living in *our* atmosphere](http://www.npr.org/templates/story/story.php?storyId=87761584); it's somewhat plausible that a similar thing happened on this planet, but the bacteria began evolving into multicellular organisms, eventually leading to the pufferpolyps.
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*Related:*
* *[How would a completely urbanized city-planet support its population?](https://worldbuilding.stackexchange.com/questions/810/how-would-a-completely-urbanized-city-planet-support-its-population)*
* *[How a completely urbanized city-planet be maintained?](https://worldbuilding.stackexchange.com/questions/813/how-would-a-completely-urbanized-city-planet-be-maintained)*
* *[Why would a completely urbanized city-planet exist?](https://worldbuilding.stackexchange.com/questions/812/why-would-a-complete-urbanized-city-planet-exist)*
The properties of the planet's surface would naturally be greatly affected, both by the changed absorption/reflectivity and by the probable draining of any surface-exposed bodies of water. How would the weather be affected? Would this even be a concern, or would the city become enclosed and essentially become a planetary-wide artificial biosphere? If so, again, how would it be maintained both against natural degradation and malicious threats? How would waste be removed/sterilized/reprocessed?
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**Problem with cooling**
It is only one of many factors, but there is a problem with cooling of such planet. This was discussed several times [on the Internet](http://mqallen.com/2013/05/16/coruscant-heat-dissipation-and-basic-worldbuilding/). The waste heat is a problem, since probably the only way how one can get rid of it is radiating it away from the planet surface. It is not easily possible to direct it away by some machinery, as this process would necessary consume lot of energy thus producing even more waste heat. If the surface temperature is supposed to be 30 C, according to the Stefan-Boltzmann law, it radiates 480 watts from every square meter. (And we do not count the incoming solar radiation! Such planet would be best situated somewhere far from its star in a cold region.) Today, average person in USA consumes about 10 kW of energy, which is entirely changed into a waste heat. This gives us that at population density 48,000/km2 - almost twice of Manhattan, the planet will start having problems with cooling itself. Of course, the bigger the energy consumption, the smaller population density is possible.
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Take a look at some google images for vertical gardens. Anytime I have seen a fully urbanized planet, I assume their tech level is higher than ours. But dont forget about plants, they are serious biomechanical machines! They produce food, fuel, fodder and medicine.
The only way to urbanize a planet would be to green the city, green roofs and terrances, vertical farms and appropriate sun alignment of cities to get all the energy from the sun (ie facing south in the northern hemisphere)
This is possible, but if it is to happen the planet would need to be much greener than Corusant or other Hollywood examples.
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Cities here on earth already have a wide range of problems with weather, the city-planet would have to deal with them, too.
# Water
Cities have drainage problems. There's not enough soil for all the rain to sink down in, and the city will either often be flooded, or it'll have to have some serious drainage channals. If your planet doesn't have oceans, it'll have to dot cloud factories around the planet to get it to rain. And you'll want rain, because the rain will clean the air just a bit. This all has to be included in the urban planning of the city. If the contractors didn't include heavy-duty drainage back when some section was built the streets will turn into a swamp.
# Wind
Again, if you don't have oceans, you can expect your wind to be a bit like on venus; from wikipeda:
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> Thermal inertia and the transfer of heat by winds in the lower atmosphere mean that the temperature of the Venusian surface does not vary significantly between the night and day sides, despite the planet's extremely slow rotation. Winds at the surface are slow, moving at a few kilometres per hour, [...]
> The wind would be slow and warm, heated by the sun and the city itself. It would not often change directions or do anything interesting like spin into tornadoes, this is because the high and low pressure areas are basically only determined by what the sun heats. Forget about wind turbines to generate power. And all that is at highrise level, on the streets, there will be virtually no wind.
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Your cloud factories are of course uniformly distributed because no section of the planet wants to live without rain, and as such, these will do nothing to cause the pressure differentials needed to whip up the winds.
If you have problems with smog on your planet, they'll be worsened by these slow winds, your smog will just hang over your factories and highways without dispersing, and only the rain will eliviate this a bit.
One advantage of these slower winds is that you can build higher, since there's less lateral stress on your buildings.
With oceans things are better: You could expect more earth-like winds, at least high over the streets. The stale air down below the highrise would not be helped much.
# Sun
If you still have problems with smog, then the answer here will be clear, it'll just be hot and filthy during the day, and it'll be warm and filthy during the night. In case you managed to keep your skies somewhat clear, things get interesting.
Anywhere with highrise, the streets will be cold, only heated by the activity going on there, but at least there's no wind. The rays of light that make it through at noon or that bounce off of the glass faces of the towers are far too short-lived to heat the place up.
The higher you get, the more light you will catch and the more pleasant it will become (hey it's a bit like being a tree in a forest), there's sunlight and at least some wind too. Yes, the most prized real-estate is definitely high above the city streets, so that's where you'll want to build, higher and higher.
You could maybe line all your buildings with mirroring glass to get the sunlight down, it would be expensive and confusing and cold inside the buildings but at least you might have a chance of heating the streets.
# Waste
There's energy in waste, and if you won't take it, nature will. Waste disposal is problematic in cities here on earth too, endless piles of garbage in the bad parts of town, problems with rats or badgers. Your planet will have these too, in its own form. If your city-planet has been a city for a couple thousand years, you might get very specialised flora and fauna that'll help clean up the forsaken streets. The people will hate the sight of them, but they make things better, really. Try to live with them instead of fighting them, maybe employ them, scatter their seeds and set them loose on filthy streets. Then when the waste has degraded, scoop up the leftovers and hose it down so people can live there again.
Some form of standardised and automated garbage disposal ought to be built into every building for the more respectable parts of the city. When your population gets dense enough there is just too much waste being produced for man to keep up with, so your options are to either automate it (I can't imagine that the entire planet was built from the ground up to support this, and with it being an afterthought, many districts are without), or nature will take over (not great if you want a planet-wide city). Garbage, an ever-growing problem on your planet, will be your biggest issue and I think a very large part of your population will be concerned with this, including politicians, engineers and even merchants as your garbage may make an interplanetary export product.
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I have a species that have evolved from their world's equivalent of deep (~3 kilometres deep) sea snails, specifically from they resemble the [Scaly-Foot Gastrobpod](https://en.wikipedia.org/wiki/Scaly-foot_gastropod). The Xeno-ocean is salty/has a significant concentration of conductors/electrolytes dissolved in the water (similar to our ocean).
I want their present day form to be
1. land dwelling
2. communicate biologically via radio signal
3. with a body size roughly that of a dog (small or large)
They presently (i.e. on land) have another form of communication, a sort of radula clicking speech. But I'd like to understand how their deep sea ancestors communicated via radio wave, to form an idea how they communicate now.
I've read [How to evolve biological radios?](https://worldbuilding.stackexchange.com/questions/27108/how-to-evolve-biological-radios), which is helpful, but that obviously does not include the the fact that radio waves do not [propagate well under water](https://en.wikipedia.org/wiki/Radio_propagation) especially salty water.
That Wikipedia page (and [others](https://en.wikipedia.org/wiki/Radio-controlled_submarine)) doesn't go into enough detail for me to know if the sort of radio waves a species could evolve would attenuate after 10 mm or 10 meters. The lower part of that range is not useful for submarines, and the upper only for radio-controlled ones (which is seems to be the focus of articles on Wikipedia), but would be the difference between the species being able to use radio waves underwater or nor.
The reason I'm asking here, and not on Physics, is because even if there *is* a range of frequencies, if the antenna/transmitter required to communicate at various distances required unrealistic power levels or antenna bigger than is reasonable for a dog sized creature ( I mention that because some submarines use a *very long* trailing wire as an antenna, which violates the dog-sized requirement above ).
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Submarines that support VLF communication (VeryLow Frequency) in the sub-30 kHz range can penetrate to 20m
Submarines that support ELF communication (Extremely Low Frequency) in the sub-300 Hz range can penetrate to 100s of meters.
If you species could generate (perhaps by touching the water with a special fin/organ) this type of frequency then communication would be possible to many interesting depths.
For more background on sub communications, this Wikipedia article is not a bad place to start: <https://en.wikipedia.org/wiki/Communication_with_submarines>
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This was going to be my idea. And here it is, but deleted! I will addend in hopes of undelete by author.
The animals are dog sized. Their antennae are much larger.
<https://www.livescience.com/3843-giant-balls-snot-explain-ocean-mystery.html>
[](https://i.stack.imgur.com/mxL8i.jpg)
Gastropods are mucus artisans. These creatures release enormous mucus antennae when they need to use VLF globespanning radio communications. Mucus would make a fine antenna - it can be imbued with electrolytes to facilitate transmission and it is recyclable, to be eaten and used again.
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According to [this paper](https://www.researchgate.net/publication/258496191_Electromagnetic_Wave_Propagation_into_Fresh_Water)
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> it has been shown in [4] that conventional RF propagation works poorly in seawater due to the losses caused by the high conductivity of seawater (typically, 4 S/m). However, fresh water has a typical conductivity of only 0.01 S/m, which is 400 times less than the typical conductivity of seawater. Therefore, EM wave propagation can be more efficient in fresh water than in seawater.
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> For such air-to-water communications, an optimum frequency range (3 - 100 MHz) was identified when the plane wave propagates to depths less than 5 m. In this optimum frequency range, the wave experiences significantly smaller losses than the losses at the lowest and highest frequencies of our analysis. Specifically, this frequency range includes the bands of short-wave radio (3 - 30 MHz), VHF TV (54 - 72 MHz, 76 - 88 MHz), parts of FM (88 - 108 MHz) and US military VHF-FM (30 - 88 MHz). Therefore, various communications systems can benefit from using the optimum operation frequencies that we identified here. Also, wireless power harvesting by wireless sensors can be significantly enhanced if it is performed inside the 3 - 100 MHz range.
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Apparently within 5 m the communication at certain frequencies can happen. As a 0th order estimate, the 400 fold attenuation means this signal only travels 1.25 cm.
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Pigeon post has a long tradition in human history. The first mentioned uses of pigeons as message carriers go back to ancient Egypt and proofs of their usage are found all over Europe, northern Africa and asia from ancient history till now.
Pigeons are used because of their strong natural homing abilities and have been breeded for centuries to optimize these abilities. If they depend on the magnetic field of earth (as is the most common theory), smell (like especially some newer Italian studies suggest), true navigation (using landmarks), possibly even celestial navigation (by the stars) or a mixture of all these is still not finaly solved. Nevertheless I am interested in some alternative birds which I could use as message carriers instead of pidgeons for my fantasy world but I couldn’t find trustworthy informations about which birds have strong natural homing abilities. So my question is:
Are there any other birds instead of pigeons which could be suitable as message carriers and could have been bred like pigeons in our timeline?
[Answer]
* *Encyclopaedia Britannica*, *s.v.* [Homing (animal behaviour)](https://www.britannica.com/science/homing):
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> Most of the best-known examples of strong homing ability are among birds, particularly racing, or homing, pigeons. Many other birds, especially seabirds and also [swallows](https://en.wikipedia.org/wiki/Swallow), are known to have equal or better homing abilities. A Manx shearwater ([*Puffinus puffinus*](https://en.wikipedia.org/wiki/Manx_shearwater)), transported in a closed container to a point about 5,500 km (3,400 miles) from its nest, returned to the nest in 12 1/2 days.
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> Non-avian animals that have homing abilities include some species of reptiles and fishes. When female loggerhead sea turtles ([*Caretta caretta*](https://en.wikipedia.org/wiki/Loggerhead_sea_turtle)) emerge from their shells, they imprint on the unique magnetic field signature of the beach on which they hatched and can navigate back to it as adults to lay eggs of their own. In addition, experimental studies have shown that several species of salmon can navigate back to their spawning streams by using their olfactory senses to find the unique chemical signature of the waterway, and juvenile sockeye salmon ([*Oncorhynchus nerka*](https://en.wikipedia.org/wiki/Sockeye_salmon%5B)), like loggerhead sea turtles, also appear to navigate using magnetic fields, from the ocean back to their spawning streams.
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* "Homing Ability in Birds", in *Nature* **170**, 237 (1952), <https://doi.org/10.1038/170237a0>:
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> A recent issue of *Ibis* contains two important articles on the direction-finding abilities of birds (**94**, No. 2). In the first article G. V. T. Matthews describes an extensive series of homing experiments carried out with 249 [lesser black-backed gulls](https://en.wikipedia.org/wiki/Lesser_black-backed_gull) (migratory species) and 91 [herring gulls](https://en.wikipedia.org/wiki/Herring_gull) (a restricted nomad), together with twenty other sea birds. On release the lesser black-backed gulls showed a significant homeward orientation which was absent when the sun was obscured by clouds [...]. The herring gulls showed a much lesser ability to 'home', and this could be explained by there being a much smaller proportion of able navigators among them. Matthews also carried out experiments in which the earth's magnetic field was masked by airborne magnets; this in no way affected homing ability.
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> In the second article Gustav Kramer describes experiments carried out with [starlings](https://en.wikipedia.org/wiki/Starling) and homing pigeons. The starling's ability to reproduce constant compass directions was demonstrated in two ways: first, by using migratory activity as an indicator, the bird tending to take up a constant direction; second, by training the birds to choose one of several (up to twelve) feeders symmetrically distributed around the cage. If the incidence of light were changed by use of a mirror arrangement the direction chosen by the bird changed correspondingly. The sun was shown to be a governing factor, the orientation faculty (in experimental conditions) vanishing if the sun were hidden. The correct direction was reproduced regardless of the time of day.
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[Answer]
[**Storks**](https://en.wikipedia.org/wiki/Stork) -- they are migratory and thus have good navigation, they are large enough to carry decent sized messages, they have some interesting colors ...and - as everyone knows - they already deliver babies.
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I think falcons might work, they are already trained by people, so we would not have to learn how to train them.
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Writing a werewolf story, and decided for a bit of flair, so I wanted two moons in orbit. Did a bit of digging, and I found out that to do that, I'd need to either have them in separate orbit (no thanks, I like calendar math, but that's the irritating kind, not the fun kind) or to have them in an L4/L5 position. Didn't like that either. So I dug a bit more.
Then I found binary star systems. [*Yes, I'm aware that this exact question has been asked.*](https://worldbuilding.stackexchange.com/questions/132559/could-a-gas-giant-have-two-earth-sized-moons-in-binary-orbit-around-it) Except, it kind of wasn't. See, the answers seem to going towards where the moons were orbiting at each other's L3 point. That's not how a [binary star system](https://en.wikipedia.org/wiki/Binary_star) works. (Watch the video, it's cool.)
Instead, the stars share one of their foci, and kind of orbit around each other, given that. So, would it be possible to replicate this on a planet, having moons that share a foci on the Earth, and opposite orbit patterns. So, while it would appear from the planet that there are two moons in the same orbit, perfectly opposite each other, in actuality it'd be different. Something like this:
[](https://i.stack.imgur.com/cYWMi.png)
(You'll probably need a guide to the picture, given that my talent is more scientific than artistic. The big yellow one is the sun, the green one is the planet, grey is moon, white is approximate orbit. And because I need the obligatory joke, 'Dammit Jim, I'm a scientist, not an artist'.)
The question is, would this work?
A note: For calculations, assume the planet is the size of Earth, or of a habitable nature, so 6x1024 kg. The moons must be visible, so assume around 1022 kg. The solar system is a single star, and the other planets are a single gas giant deep into the system and an asteroid belt beyond that.
[Answer]
Your initial configuration, with the two moons orbiting perfectly out of phase, is not a stable one.
Over time their orbits will change very slightly as the result of various random effects, such as asteroid strikes, which will not affect both moons identically. The moons will tug on each other in surprising ways. Just read up on the [three body problem](https://en.wikipedia.org/wiki/Three-body_problem) and you'll see what you're up against.
This means that one moon will start orbiting ever so slightly faster than the other, at which point they will no longer orbit in perfect antiphase. As time progresses, the angle between the two moons decreases, which will only serve to amplify any instabilities in the system. Eventually they'll reach some minimum separation, which will be when the magic happens.
***Edit: a CVn pointed out, with depressing plausibility, that what will probably happen is that one of the moons will simply get ejected from the Earth-Moon system and end up in a solar orbit.***
Turns out you don't have to guess too hard at this sort of thing, but can instead just go look at someone else's simulator. I haven't actually researched how plausible the one I found was, but hey: it has actual greek letters and stuff in its configuration, so it seems pretty serious to me.
Behold, my [two moon simulation](http://orbitsimulator.com/gravitySimulatorCloud/simulations/1559765525537_twomoon.html), using "[gravity simulator](http://www.orbitsimulator.com/gravity/articles/what.html)". One identical copy of the moon is placed next to earth, with an argument of periapsis in opposition to the regular moon. As anticipated, the moons slowly end up with their separating angle reducing, at which point one of them simply gets booted out into solar orbit. No earth shattering kaboom. Physics is *so* disappointing, but I console myself that it is just a simulation and in real life it might have been so much more dramatic.
You should fiddle with the simulator yourself, if you have sufficient patience; it is somewhat user-unfriendly, but workable. If you reduce the masses of the moons by at least a factor of 10 then you end up with something that merely looks a bit chaotic (and will probably fly apart given external gravitational influences, like your gas giant). Maybe if the moons were a hundred times lighter you'd succeed in getting them to work, but at the cost of your lovely big moons providing a scenic backdrop to your planet. Maybe your complex calendar system doesn't sound so bad anymore?
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***Here were my previous ideas, prior to running a simulation. The observation about the size differences between the moons and their parent is probably the important bit.***
In our solar system, we have the moons [Janus](https://en.wikipedia.org/wiki/Janus_(moon)) and [Epimetheus](https://en.wikipedia.org/wiki/Epimetheus_(moon)) which are [co-orbital](https://en.wikipedia.org/wiki/Epimetheus_(moon)#Orbit). They close within about 10000km of each other and then effectively *swap orbits* and slowly separate again, only to meet and swap again four years later. This is the best case scenario for your moons. It does mean that you do end up with moons in different orbits, and yes, that means you're going to have funny calendars. But conjunctions are cool, especially ones you can see so closely.
On the other hand, the parent planet of Janus and Epimetheus, Saturn, is about a billion times heavier than they are, which I suspect imposes a certain amount of stability on the whole system (or at least, stabilises it over a much longer timescale). In your example, the parent planet is only a hundred times heavier or so, and that does not fill me with warm fuzzy feelings.
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***These final ideas are clearly wrong. but I'll leave them here for future reference, if only to discourage later readers from making the same mistakes!***
I'm not a skilled enough orbital mechanic to tell you exactly what happens next, but I *suspect* that it will be one of two things: your moons crash into each other, resulting in a *Really Exciting* period of meterorite bombardment on your planet... the sort best observed from a different planet. You'll get a funky ring system for a bit, which will be nice.
The final option looks a bit like this.
[](https://i.stack.imgur.com/w5ohL.jpg)
Except, y'know, twice as much.
] |
[Question]
[
Follow up to [How can orientation-discriminating people keep their views when it turns out they live on a non-orientable surface?](https://worldbuilding.stackexchange.com/questions/101804/how-can-orientation-discriminating-people-keep-their-views-when-it-turns-out-the)
To quickly summarize the world, their are rightie and leftie people which are mirror opposites of each other. In the past they have generally hated each other. However, it turned out they lived on a [projective plane](https://en.wikipedia.org/wiki/Real_projective_plane), which has no global notion of mirror opposites (orientation), only a local notion. They did not know this at first, but overtime figured it out for the most part. In particular, as society become global instead of local, the non-orietability of the world started having dramatic and easily observable affects, such as lefties becoming righties and vice versa. More details in the post.
Anyways, there's an issue. Translators have adapted to non-orientability to ensure that it is clear what orientation they are talking about, no matter where you are in the world. (When translating or writing translation dictionaries, they specify very clearly how righty and leftie are translated. If their translations are reversed, the translator using it knows that all other oriented concepts will also be reversed. Sometimes it is not clear whether or not they are reversed (if for example the languages are usually not used in close areas), but it leads to consistent translations.) However, one of the languages is quickly becoming very popular world wide (similar to English in our world). We will call the language Z (not to be confused with Z notation). We will only talk about its vocal variant, since mirror reversed written Z is obviously distinct from regularly written Z.
Linguists developed adaptions to Z to deal with orientation, but most people did not care, considering the issue to be solely a theoretical one. Orientists and orientist sympathizers in particular where very vocal advocates. Things changed, however, after the burger poisoning, where 100 people (43 righties and 57 lefties) died of food poisoning because the orientation of the burgers were confused. Non-orientation played a large factor, which was not caught by translators since all the communications involved took place in language Z, thanks to its global nature. Some negligence on the part of the restaurant and others was also involved, so to deflect blame they made a very big deal about non-orientability, and began a campaign to get the adaptions to Z adapted.
My question is, what were these linguistic adaptions? How could the linguists have adapted Z to prevent orientation misunderstandings?
Also, for context, here are some other reasons for adoption.
* Social Justice, Sociology, and Politics: Lefties and righties have historically been separate social groups, and have frequently oppressed each other. Therefore, even if someone is not an orientist, they need to understand orientation to understand the relationships between individuals and society. A first step for this is being able to talk about orientation. They do not want language errors to hinder this.
* Business: Businesses need to understand non-orientability in order to best serve their orientist customers. For example, airlines need to make sure they do not mirror reverse orientist customers, or make them feel mirror reversed. Although they would not use the adapted language with these customers, they would need to use it internally to ensure optimal customer service.
* Biology: Although being nearly identical, lefties and righties do have some (symmetrical) biological differences. Simple examples include tools; some leftie tools do not fit in a rightie's dominant hand properly. Perfumes and other scents might also smell different. Orientation is also inherited, which is important for genealogical research. Diseases also spread and affect them differently. Most importantly, some rightie delicacies are poisons for lefties. The mirror opposites of such foods have the opposite affects. They usually smell and taste different, but hamburgers are the ultimate counterexample. Rightie hamburgers taste and smell exactly the same to righties and lefties (since the scented and flavored ingredients are achrial), but do not cause health problems for righties in moderation. However, one of the ingredients is extremely lethal poison for lefties. Leftie hamburgers work the opposite way.
Notes:
1. Here is the criteria for solving the problem: Say someone takes an object, and passes it around the world in such a way that it gets mirror reversed. The person them self stays in one place. Each time it is passed, the person passing the object tells the person receiving the object the name of the object. Once it gets back to the original person, the name of the object they are told must reflect the fact that the object has been mirror reversed. Moreover, this must never happen in a similar scenario in which the object is not mirror reversed. Note that this implies that the name of the object must change at least once along the mirror reverse path, but multiple name changes are permitted.
2. Z started out in a small, orientable, region. Thanks to colonization and globalization, it is now commonly used in large, non-orientable region of the world.
3. Sound is symmetric, so you can not mirror reverse the sound waves as part of your solution. (Well, you can, but it won't do anything.)
4. Z is not a particularly good language.
1. Every noun has a grammatical-orientation, even when this orientation has no physical meaning, even locally. For example, gold is considered a "rightie" noun, and dirt is considered a "leftie" noun, even though mirror reversing them causes no physical change.
2. Many nouns have "duals", which roughly means that they are mirror reverses, and have opposite orientations. For example, clockwise is dual to counterclockwise, a rightie person is dual to a leftie person, right is dual to left, etc... However, this rule is implied *very* inconsistently. For example, right is *also* dual to wrong. Gold is dual to dirt. Even more worryingly, rightie hamburgers *are not* dual to leftie hamburgers. Rather, the words for them are completely unrelated, grammatically. This is similar to how "brother" and "sister" have no grammatical connection in English. The same goes for many foods unfortunately. This means the linguistic adaption can not rely wholly on grammatical orientation. For example, the word for gold should not become the word for dirt when passed around the world. However, the linguistic adaption should "make sense" as much as possible using the rules of grammatical orientation. Ideally if grammatically dual nouns are in fact mirror reversed, the language adaption will switch them when they get mirror reversed by going around the world, instead of inventing new words for all of the physically mirror reversed objects.
3. Z also has many other grammatical irregularities, sometimes making it difficult to determine grammatical orientation of a word. This is similar to how "goose"'s plural is "geese", even though you usually make a world plural by adding a "s" to the end. Homophones also cause the usual problems from time to time. It is acceptable if your solution has trouble with homophones, however, since people are used to coping with them.
5. Any orientable subset of the world will leave out at least one densely populated area. That is, every orientation reversing curve crosses a major population.
6. The adaption should be reliable, meaning it is hard to mess up accidentally (intentional errors are fine sense you can't stop people from lying). In particular, if one person uses the adaption, and the other does not, they should not misunderstand each other. Rather, it should be clear that they are using different language conventions, and will have to express themselves differently. It should also be reasonably easy to learn and use, to promote adoption.
[Answer]
If I understand thing correctly, if a righty person carries a box of righty food around the world and back to the same place in a certain way, he will end up a lefty person with a box of lefty food - without the feeling of having changed himself, so the other righties around him will look like lefties to him. I'm not fully with you on the math, so I hope that's right.
In that case, since there is no absolute sense of chirality, what we have to track are changes. What matters is not if an object is lefty or righty, but rather the relation between two objects. Two righties originating in the same place are "even" to each other. A lefty and a righty in the same place are "odd". Travelling a chirality-changing route relative to another object switches your odd/even-relationship to objects not moving, and keeps your relation to objects you take with you.
In each population center, designate one reference object. This object should be something that a person can easily compare themselves to to determine if they are odd or even to the object. I could be something that makes a scent that smells different to people of different orientations, or maybe a medical scanner that determines what side of your heart is bigger. Every person in this place should know their orientation relative to the local reference.
Also build up a reference table that keeps track of the relations between the reference objects. Anytime you need to determine chirality, you can use the refence objects as a go-between. For every two references, have a person travel between them and test themselves at both to see if the path switches you.
Example: Person A has traveled here and wants to eat food F. Can they? Well, A is even to the reference of their home town. The path between here and there is odd. Food F is odd to the local reference object. Two odds cancel each other out, making F even to A. The food is edible!
The benefit is that the odd/even words should not have to interact with the old left/right words at all, minimizing confusion. For translation purposes, you can also pair each reference object with a guide saying that if you're even with the object, you're a righty in the local language. With time, this should preferably be less and less needed though.
] |
[Question]
[
I've been thinking of reviving an old Fantasy idea of mine, and I recently came across a description of a group of mythological beings that piqued my interest, and which would actually fill a niche I had been looking to fill in the World I'm working on: [the "Astomi", a tribe or race of Mouthless Humanoids described in the works of Pliny the Elder.](https://www.theoi.com/Phylos/Astomoi.html)
I had already considered having a group of people with no visible mouth, and the description of the Astomi "living on scent" and being "covered with thick hairs" gave me an idea of a mechanism by which they might be able to feed themselves, which also derives some inspiration from mythological figures such as the [Futakuchi-Onna](https://en.wikipedia.org/wiki/Futakuchi-onna) and [Harionago](https://en.wikipedia.org/wiki/Harionago) from Japan, both of whom can control their Hair as an alternative means of Feeding or Attack/Defense, and from real-life filter-feeding [Polychaete Worms](https://en.wikipedia.org/wiki/Polychaete), many of which use hair-like filaments/cilia to catch and feed off of particulate from the surrounding water (or occasionally Larger Prey Items). These usually have small tentacles or other "hair-like" structures that pull food towards specialized Mouths that are often invisible to the naked eye.
My question is... Would this work for a larger terrestrial animal? I'm not sure how much organic particulate could be strained from the air as opposed to the water, or if it would be enough to sustain something human-sized, but I do like the idea of their means of feeding being more or less Invisible, and connected to their "hairy" appearance... How much hand-waving do you think I'd have to do for this to work?
[Answer]
**Possibly, but not by living on nice smells**
Let us assume that the Astomi have energy requirements comparable to humans. Looking at the [Food energy](https://en.wikipedia.org/wiki/Food_energy) article in Wikipedia:
>
> According to the Food and Agriculture Organization of the United
> Nations, the average minimum energy requirement per person per day is
> about 7,500 kJ
>
>
>
Looking at the energy-dense foods in my pantry, Nutella's nutrition information label says that it has 2228kJ per 100g. So, if sufficient atomised Nutella is being sprayed into the atmosphere where the Astomi live, they are viable if they can absorb about 330g each day. Unfortunately, naturally occurring sprays of atomised Nutella are not a feature of even the most friendly fantasy world, so an alternative food source will be required, but this gives an idea of the minimum mass required.
Note that a large proportion of human energy is expended on running the brain and/or regulating the body's temperature - by making the Astomi cold-blooded and or small-brained they will require significantly less energy. On the other hand, if you want them to have greater-than-human capabilities then they will require a larger energy budget.
**Can they live on smells?**
At this point a quick thought experiment is in order. Imagine that there is a 4m x 4m enclosed room divided up into a grid of 1m x 1m squares, with one Astomi sitting in each square, for a total of 16 Astomi. (Assume a ceiling height of 2-3m.) Now imagine that 1g of strong perfume is sprayed into the air in this room every 15 minutes for 24 hours - this is a *lot* of perfume, resulting in a room that would be absolutely reeking by the end of the experiment. However, this is still only 96g of perfume between 16 Astomi - even if the Astomi absorb every single molecule of the perfume they have only received 6g of nutrition each. The perfume would need to have an energy density more than 50 times that of Nutella in order to provide adequate nutrition. So odours (pleasant or otherwise) are not going to cut it, the Astomi definitely need something more substantial.
**Possible sources of nutrition**
Given the requirement for feeding to be invisible to the naked eye, a few options, possibly used in combination, are:
* pollen: The Astomi brush past flowering plants and catch the pollen on their hairs, subsequently absorbing it. They will need to brush past a lot of flowers in order to survive this way given the low pollen mass per flower, which will mean they have a higher energy budget and will need to be nomadic in order to give the flowers in an area time to recover before they feed again.
* insects: Possibly Pliny the Elder had it backwards and the Astomi actually emit smells that attract insects. The hairs then trap the insects and draw them into tiny pockets hidden beneath their hair akin to the pitfall traps of [pitcher plants](https://en.wikipedia.org/wiki/Pitcher_plant), where they are digested and the nutrients absorbed. A variant of this would make the Astomi anteaters - they sit or kneel down on an ant nest and appear to a surface observer to be sniffing the air, while below the surface the specialised long hairs on their buttocks or knees are diving into the ant nest to seize ants and larvae then drawing them into their digestive pockets.
* Honey: The nutrition label on the tub of honey I am looking at says it has 1401kJ per 100g. So if the Astomi have hairs that can slip into a beehive and escape unscathed they can definitely do pretty well from a hive. However, this encounters the same issue as collecting the pollen themselves - they need to have a large range before the resource will regenerate.
In short, the Astomi are plausible insectivores, but not odourvores.
] |
[Question]
[
"[Nightfall](http://escapepod.org/2007/04/05/ep100-nightfall/)" by Isaac Asimov (you can hear the story here on [escapepod](http://escapepod.org/2007/04/05/ep100-nightfall/), if you need it) postulates a planet in a multi-sun system. The orbital mechanics of the 6 suns result in all of the sides of the planet being illuminated all of the time but for one short period of a single 'day', at the 5 big suns just happen to align on one side of the planet with the dimmest one blackened out by the single moon opposite to them, leaving it to rotate a full time with a considerable (half) of the planet not illuminated. This event happens all ca. 2050 years, resulting in massive fear of the dark and crumbling society.
**Now... How would this Hexa-star system have to be set up, assuming there is no other planet or moon?**
[Answer]
Designing a star system that has a planet with perpetual sunlight for thousands of years at a time is an almost impossible problem. Therefore I would say:
This looks like a job for Sean Raymond of the PlanetPlanet website:
And in fact he has discussed the many, many problems with designing a Kalgash system that will work as in the story, in some posts this year.
[<https://planetplanet.net/2018/02/02/real-life-sci-fi-world-11-kalgash-a-planet-in-permanent-daytime-from-asimovs-nightfall/>[1](https://planetplanet.net/2018/02/02/real-life-sci-fi-world-11-kalgash-a-planet-in-permanent-daytime-from-asimovs-nightfall/)
<https://planetplanet.net/2018/03/21/asimov-kalgash-take2/>[2](https://planetplanet.net/2018/03/21/asimov-kalgash-take2/)
Sean decided that the Kalgash system as described in the novel wouldn't provide the necessary length of time between darkness.
so he designed a different type of solar system than in the story and novel, in order to get one where a planet could have eternal light.
And I suppose that his answers are the best you can expect to get.
] |
[Question]
[
I sometimes think about the arrogant dwarf starsmiths in the question.
[How to blow up a star by accident?](https://worldbuilding.stackexchange.com/questions/86245/how-to-blow-up-a-star-by-accident/86255#86255)
I pose the question in the voice of the dwarf, probably because I am hungry for down votes.
---
A dead world, eons frozen, circling the dark of its dead sun. Long ago this world bloomed with life. But its sun was old. Even as the star withered in dying and its fires dimmed, its child moved away, as if fearful of the dying. Then the child died too. At the equator, last refuge in a freezing world, this world’s creatures lay yet, curled waiting for a summer that would never come. The strange snows cover their forms – first water, then nitrogen, then last the oxygen, falling from the cold sky. Thus the world has lain, for a thousand million years.
Could this world live again? Its own goddess is gone, but the Goddess of our home world is free with her favors. Just as a cave opened to the light will spring to the green, so too the Goddess could take this world and make it her own – if we could give her a light and heat to do it.
We do not have the craft to build a star but we have mastery of fission. We can build a moonlet of the heavy elements that sustain the fission. The fires of fission cannot be allowed to burn too hot - to stoke the fire, we will lard it with carbon and quench the force that would otherwise overwhelm it. Controlled, a great stone *(50,000 m 3 )* of the ninety-second element (*uranium*) can burn with the power of a star for a million years. [source](https://www.ocean.washington.edu/courses/envir215/energynumbers.pdf)
The power is there. Now how to make this a light suitable for a Goddess? The glow of a fusion star is its heat but this moon cannot be as hot as a star or it will burn too fast. Each element has its color. Can we add these elements such that when heated they glow with the reds and greens of a star, but without the heat that would consume it before the world is warmed?
---
In sum: A life-giving star emits much energy in the visible frequencies.
[](https://i.stack.imgur.com/SJZnz.jpg)
<https://www.windows2universe.org/sun/spectrum/multispectral_sun_overview.html>
A fission reaction hot enough to glow like a star will runaway and explode. **Can one add various elements to the surface of a fissioning satellite of uranium such that the glow of the respective elements can duplicate the frequencies (and energy output) of a star?**
[Answer]
# Edited to object to the question
I guess I don't speak dwarf, so I didn't pick up the fact that you said that you can't have the sun that hot or fission will go too fast. In fact that is...backwards!
Lets say you have a solid mass of Uranium. This Uranium has two components, U-235 and U-238. U-235 is fissile, U-238 is not. So unless you have something like ~5% U-235 (which is called enriched Uranium), you will never start a fission chain reaction. Well...there are exceptions, but we will get to them.
In any case, lets say that you have an enriched uranium ball that is well above critical mass, being moon sized and all. So it is super-critical, and it starts producing energy. What stops it? First off, lets be clear that the particles ejected from a fission reaction have *more* than enough kinetic energy to escape the solar system. So if you do have a near-compelete chain reaction, your moon sized Uranium block will be turned into an expanding ball of plasma within hours. So your reaction has to be controlled in some way to not proceed as a chain reaction.
Second off, U-235 does not undergo fission from 'fast' neutrons. The neutrons spit out from a fission reaction will have some MeV of energy; if the hit a U-235 at that energy, they will simply bounce off, there will be no fission. They have to be going slow enough to react with the U-235 nucleus; they need to 'thermalize' down few orders of magnitude of energy. This is what would eventually stop the chain reaction; as the material gets blown apart, there is nothing to thermalize the escaping neutrons and the chain reaction will stop.
To lose this energy, neutrons have to bounce around like a pinball off of other uranium atoms (since there isn't anything else to react with in a moon sized block of uranium). Now, U-238 has a resonance absorption region, where at certain specific energies, a neutron that hit is will be captured. Going from MeV to keV will take many 'bounces' from a neutron, so it has a chance to get absorbed by U-238 on each bounce, if its energy is just right.
There is an effect called doppler broadening at high temperatures, where the breadth of the emission and absorption spectrum of an atom will increase when the atom has a high kinetic energy. So, as U-238 increases in temperature, it will increase in its ability to absorb neutrons. What his means in practice is that if your reaction is slow enough in the first place to not be a bomb, it will soon be shut down as the temperature increases.
So you put your problem exactly backwards; if your temperature gets high enough, you won't even have a star any more, just a warm rock.
### Conclusion to objection
Your described mechanism for making the 'fission star' does not work as is; and your statement that increased temperature will make it burn too fast doesn't work either. Therefore, I am answering the question from the assumption that it works, somehow. If it works, somehow, then this is the best way to get a sun-like absorption.
Last note, I think there is a way to make a self-moderating block of Uranium, but that way is turning it into a U-238 fast-fission breeder reactor, where temperature regulation comes from setting the rate at which U-238 is bred into fissile Pu-239. But that is a subject for another question.
Back to generating spectra...
# Yes
No need to fuss with special elements, the emission spectrum of a hot object is mostly based on its temperature. Here is the emission band from the sun.
[](https://i.stack.imgur.com/65o3H.png)
The black line is the 5250 C [blackbody radiation](https://en.wikipedia.org/wiki/Black-body_radiation) curve. This is the spectrum that anything of that temperature will emit.
You may be concerned about the spectral emission/abosorbtion lines for various elements, and how that would affect the light. Well, hydrogen has absorption lines at 410, 434, 486, and 656 nm. Those dips are barely visible on the graph. Sure there is a slight reduction at those specific frequencies, but not enough to make much of difference.
Uranium has absorption lines all over the place, but since Hydrogen's absorption didn't matter much, Uranium's won't either.
[](https://i.stack.imgur.com/TeU0Q.jpg)
# Conclusion
All you have to do is regulate temperature at the appropriate level, and you will have a sun-like light source. Now, how you will get your fusion star to stay at the correct temperature is non-trivial, but that sounds like a great follow-up question.
[Answer]
# Option 1: Continuous spectrum
Your first choice would be to recreate the [black body](https://en.wikipedia.org/wiki/Black-body_radiation#Spectrum) spectrum of the star. For a black body at a temperature $T$, the intensity $J(\nu)$ is
$$J(\nu)=\frac{2h\nu^3}{c^2}\frac{1}{e^{h\nu/kT}-1}$$
where $h$, $c$ and $k$ are constants. For low-energy photons, $J(\nu)\approx\frac{2kT}{c^2}\nu^2$. For high-energy photons, $J(\nu)\approx\nu^3e^{-h\nu/kT}$. In all regimes, if you want to have a certain intensity at a certain frequency, you need a specific temperature. There's no way around it.
This means that if you want to duplicate a black body spectrum, you need to recreate the object's temperature. To mimic the Sun's spectrum, you object would have to have a surface temperature of about 5800 K. You've already stated, though, that you can't have that. Therefore, this option is off the table.
# Option 2: Discrete spectrum with line broadening
Your second choice - the one you proposed - would be to take a bunch of atoms in different excited states and produce [emission lines](https://en.wikipedia.org/wiki/Spectral_line). Now, thanks to miscellaneous interactions and collisions, [normally a spectrum becomes essentially continuous](https://physics.stackexchange.com/a/46081/56299). The result is a spectrum that appears continuous.
Another way that a discrete spectrum can become more continuous is through [line broadening](https://en.wikipedia.org/wiki/Spectral_line#Line_broadening_and_shift). This can happen through a number of mechanisms.
1. **Natural broadening.** The Heisenberg uncertainty principle means that there is uncertainty in the "lifetime" of an energy state - the amount of time an electron will spend in that state. The energy-time version of the uncertainty principle is
$$\Delta t\Delta E>\hbar/2$$
meaning that a smaller uncertainty in time implies a larger uncertainty in energy. This leads to a wider range of emission frequencies - an effect called natural broadening.
Unfortunately, natural broadening isn't effective. For instance, the natural broadening of the [Lyman $\alpha$](https://en.wikipedia.org/wiki/Lyman-alpha_line) hydrogen line is
$$\frac{\Delta\lambda}{\lambda}\sim2\times10^{-8}$$
In other words, it's smeared out by only a tenth of a billionth of its original wavelength.
2. **Doppler broadening.** Electrons and atoms move around because they have non-zero temperatures, and thus non-zero kinetic energy. Therefore, the photons they emit are subject to the [Doppler shift](https://en.wikipedia.org/wiki/Doppler_effect). It turns out that Doppler broadening is much more effective than natural broadening; we get
$$\frac{\Delta\lambda}{\lambda}\approx3\times10^{-7}\left(\frac{T}{1\text{ K}}\right)$$
for a hydrogen atom of temperature $T$. At 1000 K, for instance, we see a broadening of $\sim10^{-5}$. This is, of course, also disappointingly small. At visible wavelengths, you'd see broadening of perhaps one-thousandth of a nanometer or so.
Other types of broadening - pressure broadening through collisions, or Zeeman broadening through magnetic fields - give you similarly paltry results. Therefore, I don't think that you could easily get a continuous spectrum from adding some discrete components.
# Conclusion
Neither of these options is particularly appealing. In short, it doesn't seem feasible to recreate a star's spectrum without raising the temperature high enough to reach temperatures akin to the surface of the Sun.
] |
[Question]
[
What would be the effect on climate on an Earth-like moon of a gas giant, which experienced regular ("monthly") total solar eclipses (by its gas giant parent) lasting approx. 40 hours.
I'm trying to recreate a realistic climate for this world. All things being equal, the moon is slightly warmer than Earth (its big enough, with sufficient magnetosphere to hang on to its atmosphere), it is not tidally locked, and rotates on its axis as well as orbiting its parent. So it has a fairly "normal" day and night cycle (notwithstanding light reflected by its parent during "night"). But I cannot find guidance anywhere on the web what kind of affect a monthly 40-hours of total darkness for the whole moon would have on its climate, and the development and behavior of its plants (maybe it has no appreciable affect, I don't know, but I'm assuming some cooling beyond what is usual for normal night, towards the end of that 40-hour period).
Any thoughts would be greatly appreciated.
The setting is the same as [Captured Earth-Like Moons around Gas Giants](https://worldbuilding.stackexchange.com/questions/82415/captured-earth-like-moons-around-gas-giants)
I used the formula provided by Michael Kjörling in this thread [Earth-like Moon around the Gas Giant. Eclipse length?](https://worldbuilding.stackexchange.com/questions/71033/earth-like-moon-around-the-gas-giant-eclipse-length) to calculate the eclipse length.
Same setting as: [Captured Earth-Like Moons around Gas Giants](https://worldbuilding.stackexchange.com/questions/82415/captured-earth-like-moons-around-gas-giants)
[Answer]
Using moon that is eclipsed for 40 hours every month would receive roughly 1/18th (5.5%) less sunlight than a similar moon without such an eclipse. Since you have defined your planet to be earthlike we can assume that it's receiving more solar energy to compensate for this. There will be a monthly cycle to the average temperature, coldest at the end of the eclipse and slowly warming up again over the course of the month.
Life would have to evolve to cope with regular drops in temperature. This is something that life in higher latitudes, and altitudes has to deal with already.
[Answer]
The effect on climate would not be very strong. If your moon has Earth-like atmosphere, it would easily survive the effect of 40-hour eclipse. Temperature will plunge lower than during normal nights, but I don't think we'll see the difference ever exceeding 10 degrees C. Animals and vegetation should be able to easily adapt to such events.
P.S. I did not look at Michael Kjörling's formula, but the results do not seem right. Actual eclipse on Jupiter's Ganymede, for example, lasts for hours, not tens of hours.
P.P.S. Looked more into Michael Kjörling's answer. In comments, other people pointed to the error, using exactly the same Ganymede example. But there is no corrected formula still.
[Answer]
It wasn't clear to me if you wanted the 40 hours a month or if you calculated it and are now suffering with it. If it's the latter case, you might look at this wikipedia entry on Penumbra. You quote masses of planets necessary, but unless I'm mistaken the mass of a gas giant can be increased with a higher density, like a large solid core or something, without increasing it's size, which is what affects the eclipse length. You could probably find orbits, masses and sizes that work for any eclipse length. Heck, you could even have the moon orbit at a right angle to the sun and never really be in shadow. If you've considered this then. . . ummm, my apologies. Disregard. Click on this little number one.
wiki on umbras[1](https://en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra)
[Answer]
Short answer:
On most or all habitable moons of gas giant planets the typical nights should last several times as long as the eclipses caused by the shadows of the planets the habitable moons orbit. Thus you should ask what the effects of those long nights are likely to be, instead of the effects of the much shorter eclipses.
Long answer:
40 hours per month of the moon? And how long is the month of the Earth like moon?
An Earth like astronomical body, habitable for beings like humans, should be at least 3,000,000,000 years old, and possible billions of years older.
>
> However, considering an Earth-mass exomoon around a Jupiter-like host planet, within a few million years at most the satellite should be tidally locked to the planet—rather than to the star
>
>
>
<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>[1](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets)
Thus the habitable moon's day should equal its monthly orbit around it's planet, while its year should its primary planet's orbit around their sun.
>
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<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>[1](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets)
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<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>[1](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets)
The planet's year as it orbits around the sun of their system should be at least nine times as long as the habitable moon's month and day as it orbits around the planet, and possibly several times nine times as long as a month/day.
If the habitable moon's month/day might be 1.7 to 16.7 Earth days, as suggested above, and the length of the year must be at least 9 times as long, the length of the year of the habitable moon should be at least about 15.3 to 150.3 Earth days.
Detected exoplanets considered to probably be within the habitable zones of their stars have days ranging in length from 6.1 Earth days to 384.8 days.
<https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets>[1](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets)
We might arbitrarily assume that 2,000 Earth days is the longest possible year for a habitable world - Ceres, near the outer edge of the most optimistic habitable zone calculated for our sun has a year 1,683 Earth days or 4.60 Earth years long.
<https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)>[2](https://en.wikipedia.org/wiki/Ceres_(dwarf_planet))
<https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#/media/File:Estimated_extent_of_the_Solar_Systems_habitable_zone.png>[3](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#/media/File:Estimated_extent_of_the_Solar_Systems_habitable_zone.png)
And we might arbitrarily assume that 5.0 days is the minimum possible year for a habitable planet.
And thus the month/day of a habitable moon should be less than 0.5555 to 222.2222 Earth days in order to be less than one ninth the length of the planetary year.
An eclipse period of 40 Earth hours or 1.666 Earth days would require a month/day of considerable length.
The closer a moon orbits to its planet the more tidal heating will heat it. The closer a moon orbits to its planet the more sunlight reflected from its planet will heat it. Thus a moon orbiting too close to its planet will become too hot and suffer from runaway greenhouse heating and loss of its water into space.
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> Moons at distances between about 5 and 20 planetary radii from a giant planet can be habitable from an illumination and tidal heating point of view, but still the planetary magnetosphere would critically influence their habitability.
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<http://adsabs.harvard.edu/abs/2013arXiv1309.0811H>[4](http://adsabs.harvard.edu/abs/2013arXiv1309.0811H)
The shadow cast by a planet upon its moon's orbit will have a diameter of 2 planetary radii. If the moon's roughly circular orbit has a radius of 5 to 20 planetary radii it will have a circumference of 31.4159 to 125.6636 planetary radii or 15.70795 to 62.8318 times the diameter of the shadow cast by the planet.
Thus the month/day of the habitable moon will be about 15.70795 to 62.8318 times as long as the period in eclipse - if the moon orbits the planet in the same plane, or close to it, as the planet orbits their sun. If the moon's orbital plane is more than slightly different from that of the planet, the moon will be eclipsed by the planet on rare occasions or will never be eclipsed by the planet.
If the habitable moon and its planet orbit in the same plane, the habitable moon's month/day should be about 15.70795 to 62.8318 times as long as the period in eclipse once per month/day.
If the of the planet orbited by the habitable moon should be at least nine times the length of the month/day of the habitable moon, there should be at least 9 eclipses during a year of the planet, and the year of the planet should be at least 141.37155 to 565.4862 times as long as an eclipse period.
If the eclipse period is about 40 Earth hours or 1.6666 Earth days as said in the original question, the habitable moon's month/day will be about 628.318 to 2,513.272 Earth hours, or 26.179916 to 104.7196 Earth Days. Thus the length of the planet's years should be about at least 235.61924 to 942.47694 Earth days or at least 0.6450 to 2.5803612 Earth years.
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<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>[1](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets)
Thus the month/day of the habitable moon should always be several times as long as the length of the period that habitable moon spends in the eclipse by its planet.
And if the calculation that a habitable moon's orbital distance should be five to twenty planetary radii is correct, the habitable moon's month/day should be about 15.70795 to 62.8318 times as long as the period in eclipse.
If the original question is hoping for an eclipse lasting longer than one day of the moon, the answer must be no, because a moon cannot have a day of arbitrary length. The length of a moon's day must equal the length of its month, since almost all moons will be tidally locked to keep one side always facing their planet and the other side always facing away from the planet.
There is some hope for a habitable moon to rotate faster than its orbital period around it planet.
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> Since the satellite's rotation period also depends on its orbital eccentricity around the planet and since the gravitational drag of further moons or a close host star could pump the satellite's eccentricity (Cassidy et al., 2009; Porter and Grundy, 2011), exomoons might rotate even faster than their orbital period.
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The sources are:
Cassidy T.A. Mendez R. Arras P. Johnson R.E. Skrutskie M.F. Massive satellites of close-in gas giant exoplanets. Astrophys J. 2009;704:1341–1348.
<http://iopscience.iop.org/article/10.1088/0004-637X/704/2/1341/meta>[5](http://iopscience.iop.org/article/10.1088/0004-637X/704/2/1341/meta)
Porter S.B. Grundy W.M. Post-capture evolution of potentially habitable exomoons. Astrophys J. 2011;736:L14.
<http://iopscience.iop.org/article/10.1088/2041-8205/736/1/L14/meta>[6](http://iopscience.iop.org/article/10.1088/2041-8205/736/1/L14/meta)
But I have my doubts that the rotation period of a moon could ever be shorter that the time it spends in the shadow of its planet during an eclipse.
Thus on most or all habitable moons of gas giant planets the typical nights should last several times as long as the eclipses caused by the shadows of the planets the habitable moons orbit. Thus you should ask what the effects of those long nights are likely to be, instead of the effects of the much shorter eclipses.
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As has already been said, the macro-effects of such eclipses would be relatively insignificant, yes, globally slightly colder with a warming period, but not much else, etc.
But the most interesting effect, to me, is on a more micro-scale, and that is changes in wind. On Earth, even in a relatively insignificant (compared to a full planet eclipse behind a gas giant) partial lunar eclipse, there are noticeable changes to winds, I've felt these changes personally, and it's weird and creepy feeling. What form these changes take would depend on the region of the moon, prevailing winds, Coriolis effects, and much more. What I felt during the lunar eclipse was first a cooling of the wind (not just the ambient temperature, but of the wind itself), followed by an unusual change in wind direction (far removed from normal prevailing winds in the area), then the wind became steady (as opposed to gusty), and then started slowing down steadily.
For an eclipse on a planetary scale, I would expect similar trends, overall. Though the restart of the wind could be quite drastic when the "sun" comes out again afterward. I imagine low elevation land areas would feel the wind almost die out completely, very quickly, and go cold. Higher elevations, and oceans could feel a more gradual change, because of factors like jetstreams and lack of obstructions, respectively. Areas with normally strong prevailing winds might feel the gusts align with jet streams or Coriolis-driven winds, and settle in to slow, cold, steady breezes.
When heat returns, it will start on just one edge of the moon, causing a massive updraft there, and major horizontal winds will move toward it to fill the space recently vacated by the rising air. This might even be drastic enough to cause a complementary downdraft on the night side of the moon, but at the very least it would cause a ring of downdrafts around the twighlight areas of the planet, all of which might eventually settle (days? a week?) in to whatever is the equivalents of 'normal' jetstreams and coriolis winds for this moon. Or the cycle of calm and chaos might be as 'normal' as it gets.
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I've been working on an alien species, and I wanted it to have a blood colour other than red. I was going to go with Coboglobin until I found the sites I was looking at providing diametrically opposite info.
The first one I looked at claimed that Coboglobin was best in warm, oxygen-rich environments, and was amber-coloured in the arteries and clear in the veins, and the second site I looked at claimed that it was best in cold, oxygen-poor environments and was clear in the arteries and amber in the veins. Obviously someone got it completely backwards, but I'm not sure which!
For reference, the species is roughly human-sized and has an upright build and is a very distant descendant of a type of animal that had characteristics of both insects and other arthropods - namely the circulatory system and closed respiratory system of land crabs - but has diverted massively since, to the point that it no longer fits that classification (mostly so I can get away with it being human-sized without having to deal with factors that limit insect and arthropod size, like the weight of pure exoskeletons and the poor oxygen-carrying capacity of Haemocyanin).
I've gotten some very helpful feedback, and now all I'd like to clear up once and for all is whether Coboglobin is more suited to warm, oxygen-rich environments as [this source states](https://www.reddit.com/r/worldbuilding/comments/2ksetb/faerfoxxs_guide_to_blood_chemistry/) or cold, oxygen-poor environments as [this source states](https://worldbuilding.stackexchange.com/questions/33386/the-benefits-of-alternate-blood-bases/33416#33416).
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Coboglobin is colourless when deoxygenated and amber yellow when oxygenated.
Veins typically carry our deoxygenated blood, so it would be clear in the veins and amber yellow in the arteries.
Coboglobin also has a low tolerance for cold and low oxygen, so it's best used in consistently warm (~15 degrees Celsius sounds about right) temperatures, and highly oxygenated environments. Unfortunately, the high oxygenated environments suitable for this blood base makes this a poor contender for an environment humans could live in.
If you're purely looking for a different color than red, I would suggest Vanabins. Vanabins has a range of colors, starting from deep blue-purple when deoxygenated, and as the oxygen level increases, the blood changes color from green to blue to yellow.
For an environment that suits humans and your species, I would suggest using Hemerythrin as a blood base - Hemerythrin preforms equally as well regardless of environmental conditions, and can be used well in cold or warm and low or abundant oxygen environments. Unfortunately, it only works at 1/4th of the efficiency as other transport cell types. It promotes cell growth and regeneration, allowing faster healing, as well as giving immunity to carbon monoxide poisoning and resistance to nitrogen stress on the blood stream. It's Colorless when deoxygenated and violet when oxygenated.
Combine that with Erythrocruorin for the plasma, and you might be able to fix the inefficiency issues. Erythrocruorin is based around a massive complex of iron molecules, allowing it to transport many dozens or possibly even hundreds of times the amount of oxygen as hemoglobin. It's red, like hemoglobin, but much more intense. With a balance of the Hemerythrin and Erythrocruorin, you could possibly produce an interesting magenta.
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From Wikipedia: 'Blood of this type would be amber yellow in colour when in the veins while uncoloured and clear in the arteries.' I am pretty sure this is right.
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I think of a world of islands floating in the sky. The planet basically is (was) our Earth. For some reason all that is left is a small ball covered nearly completely with water. Pieces of the shattered continents are floating in the sky, maybe at a level of 4,000 m height. The rest of the Earth system still works as usual, e.g. the radius of the core shrunk only insignificantly, the rotation is the same, the moon is still there etc. Assume that the ocean is mostly the same depth everywhere, insignificantly small islands like current hotspot volcano islands exist.
The "islands" don't have the size of the old continents, they are a lot smaller but diverse in size.
How would the wind system of the world change in this scenario?
[](https://i.stack.imgur.com/mzqTy.jpg)
(Source: [Wikimedia commons](https://commons.wikimedia.org/wiki/File:Earth_Global_Circulation.jpg)
Would there be special stack effects? Or would I get just a "boring" system of circular winds without much of seasonal and geographical changes?
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I disagree with Kingledion's answer. Yes, the general atmosphere would work like he wrote, however I believe the floating islands will interfere with the development of high and low pressure systems which form the backbone of the hadley/ferrel cell circulation.
The floating islands, while not continent sized, will create shadows on the surface of the planet. This will create areas of cooling. The surface of the floating islands will warm up due to reflection of sunlight and the heat transpired by any plants and animals. This will affectively bring extra warmth to the middle - upper regions of the atmosphere (depending on how high they are floating).
On the surface this will create areas of low pressure in the island shadows, and areas of higher pressure in areas with direct sunlight warming the surface. On the floating island surface, there is also isolated areas of higher pressure and areas of cooler pressure in the open air.
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So now you have three dimensions to take into account; (1) the 'horizontal' surface to surface dimension, (2) the 'vertical' atmosphere to surface dimension and (3) the 'horizontal' atmosphere to atmosphere dimension.
The surface generally warms more at the equator than at the poles. So localised shadow affects will change the way that the wind and atmosphere moves. If there are more islands concentrated in a certain latitude band at specific times (as suggested by Kingledion), this will result in more shadows on the ground, resulting in a cooler than expected ground temperature.
(1) This will result in surface low pressure systems in areas that would normally be experiencing high pressure systems. eg if a low pressure system forms around the equator because of the islands, air will end up flowing from the midlatitudes *towards* the equator, instead of *away* from the equator as it does now on Earth. So wherever you have a concentration of floating islands, the surface winds will change in accordance - wind blowing from the sunlight warm areas to the cooler shadow areas.
(2a) This will create a strong pressure differential between the cooler surface than the warmer floating island tops. Wind moves from areas of high pressure to low. So you will have stronger downward winds wherever there are large concentrations of islands. (note, even though 'heat rises', air temperature does cool with altitude. About 1 degree celsius for every 100m. I doubt you will get equator surface temperatures on your equator floating islands, but the temperature will be warmer than expected at that altitude in comparison to Earth).
(2b) Winds pulling cold mid to upper atmosphere air down to the surface is what normally happens at the poles. It is *one* of the reasons why it is so cold there. But if you have floating islands at the poles, they may break the airflow, as well as bring slightly warmer air (from transpiration and albedo reflection etc) to the mid to upper reaches of the polar region. This could result in slightly warmer sinking polar winds (only slightly, as the poles are still terribly cold due to lack of sunlight for 6 months of the year). This might actually result in more snow fall, as for snow to fall temperatures need to drop to below freezing and then rise again. So you can expect more winter snow storms in your polar regions. But also a slightly warmer summer, so you still have to worry about global warming as a whole.
(3a) Winds will also blow from the islands warmer center towards the outer ridges of the islands into empty space. So winds will be blowing off the islands and then be pulled down (might want to erect some fences along the edges for any toddlers).
(3b) Warm air doesn't mix well with cold air. It generally creates very big storms. Think hurricanes. A steady source of warm air in the typically cooler mid to upper atmosphere will feed upper atmosphere storm systems. Resulting in more rain falling to the surface or at least around the edges of the floating islands.
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So you can see, if you have large 'concentrations' of floating islands, this can mess with the local atmospheric pressures. If this happens, I believe you will still have the Hadley/ferrel circulation cell system, but it will be weaker. Less warmth rising from the equator surface and slightly less cold sinking at the poles. This will impact the strength of the overall resultant atmospheric winds systems, the general atmospheric winds like the jet streams etc will be weaker, and prone to disruptions from the ever changing nature of the floating islands below them.
But never fear, if a large concentration of islands does develop, a once in a 100 or once in a 1000 year storm will come along and break them apart scattering them in all directions. And you can start all over again.
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If your floating islands have some sort of magically assisted buoyancy, then they will pushed by prevailing winds into certain locations on earth. This depends on how high they are; in the upper or lower region of the Hadley cell.
The rising air masses from the equator will blow any high floating islands that started within ~3° of the equator outwards and concentrate them at 30° N or S. Low floating islands, on the other hand, will be concentrated at the equator. Outside the tropics, high floating islands will end up at ±30° and the poles, while low floating islands will end up at ±60°.
The oceanic surface being so large in comparison to the size of the islands will give the entire planet an oceanic climate. Seasonal and daily temperature variations will be low everywhere. Without any continents to disrupt weather patterns, a perfect ideal Hadley and Polar cell will develop. There will not be significant variations as seen on earth, like the Gulf air masses that make the Eastern US relatively wet, the cold currents that turn Baja California into a desert, or the monsoon rains of India.
The location that your islands end up will affect their weather. The islands will move as the seasonal progression pushes the high/low pressure zones north and south. Equatorial low islands would wander from the equator around 10 degrees north and south, into the hemisphere that is having summer. In any case, the islands will stay in the equatorial zone, giving them the perfect rainforest climate.
At ±30° the islands will be in a perfect warm desert, as the islands will drift away from the advancing sun in the summer, and towards the retreating sun in the winter. They would never get too hot or too cold, but would always be dry, like summer in California or Sicily.
A ±60°, the island would be stuck in permanent winter. 60 degrees off of the sun is New York in January or February…so not great for habitation. Again, these islands will drift north (or south) away from the advancing seasonal sun, so they won't really have a summer. I don't see much life here.
The Polar islands would basically be Antarctica.
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It depends just how much of the sky those islands cover, that's going to effect how much heat the ocean gets and thus whether the traditional wind model will apply. Also important is where the islands *are*, well mainly how much of the equator they cover since that's where most [insolation](https://en.wikipedia.org/wiki/Solar_irradiance) occurs. Ultimately thermal input is the real driver behind the world's oceanic and atmospheric circulation.
There are going to be two other effects that you need to consider when looking at life on that world, one is that with no relief (in the topographic sense) to break the rush wind is going to travel uninterrupted around the world, Easter Island will give some clues to just how strong those winds are going to get. The second thing is that the world ocean is going to be pretty well dead due to lack of oxygen, there's nothing to drive currents on a basically flat ball of rock.
Life up on those islands is not going to be fun, half the sea level air pressure we're used to having is going to make it really hard to survive, human start to get altitude sickness from 1500m onwards and with the continents gone it'll be even worse.
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Ever since grade school, we have been taught to visualize time in the form of a time-line. This model works particularly well considering the fact that, according to widely accepted scientific theory, *time exhibits the same dimensions as a line*, with movement across this dimension being constrained to a linear progression.
**So, what would the universe look like if time had more than one dimension?**
For the sake of this particular question, I'd like to focus on 2-dimensional time, and how our universe might express this second temporal-dimension in contrast to linear time.
**My Interpretation:**
While I'm not by any means certain as to what 2D-time would look like, I imagine that it would look something like what would happen if the entire quantum-miltiverse merged into one universe. I.E: every possible iteration of the time-line would exist simultaneously, occupying the same space.
**Questions:**
1. Is the conclusion which I have drawn correct, or am I barking up the wrong tree?
2. Are there any (other) scientifically valid interpretations of my question that might make for a more unique and/or interesting setting?
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People commonly interpret this as being multiple timelines, or the meta-time in which history may be changed.
But more seriously, you would have physics defined in 5 or more dimensions with 2 or more being "time like". (Oh look, [It's in Wikipedia!](https://en.m.wikipedia.org/wiki/Multiple_time_dimensions))
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> Special relativity describes spacetime as a manifold whose metric tensor has a negative eigenvalue. This corresponds to the existence of a "time-like" direction. A metric with multiple negative eigenvalues would correspondingly imply several timelike directions, i.e. multiple time dimensions, but there is no consensus regarding the relationship of these extra "times" to time as conventionally understood.
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You would have *events* plotted in 5 dimensions with rules explaining the allowed relationships between them. These rules may be *different* along the different kinds of time. But, like space dimensions are all the same, I like the symmetry of two time dimensions being the same too.
How this would seem to someone inside it, I'm not prepared to say※. The common wisdom is that [it would not be "interesting" like our universe](https://en.wikipedia.org/wiki/Anthropic_principle#Spacetime).
(I'd copy the illustration but it doesn't like SVG it seems. See the link in the paragraph above, please.)
But another idea would be, not a *branching* universe, but a 2D plane on which the world line of an object can choose a line. Just as forces change the direction of motion in 3 spacial dimensions to pick out one possible line, the time direction might be one chosen line out of infinite possibilities. A different kind of force would alter the trajectory. That would leave the world behind, as everything else continues on the old time direction. This describes what's normally considered *parallel universe*, and logically that's indeed what a parallel universe is. Perhaps you can combine *separate* history and *branching history* by having specific things cause splitting rather than *everything* causing splitting.
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※ **update:** Greg Egan is writing a novel set in a universe with two space dimensions and two time dimensions. See [his page](http://www.gregegan.net/DICHRONAUTS/00/DPDM.html) for material including the mathematics of spacetime in his universe! This material was made available in December 2016. The novel will be out in mid 2017.
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You would have to have another form of input in order to look sideways across time.
Our eyes see what is around us in this space and time. You'd have to have a time2D vision organ to allow you to see across the time space to the other timelines.
Or maybe a different structure inside the eye, like rods, cones, and Penrose triangles.
To normal eyes you'd see the time and place you are now, but to the other eye I think you're right that you'd see all the possible timelines stretching out beside you.
I imagine them being flatish and layered, blurring as they overlap each other.
The timelines closest to you would be the most similar with only minor differences. The differences might not even be anything near you. Maybe on the other side of the planet (a bird almost got grabbed by a hawk/became a hawks supper), and that caused a new timeline to branch.
If you were able to step sideways across them your normal eyes would see the world flicker as you passed by.
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IF you are thinking about how to draw or visualize this, perhaps you should envision a loaf of sliced bread.
[](https://i.stack.imgur.com/yskKG.jpg)
If you imagine the time moving from the (infinitely distant) back of the loaf to the (infinitely distant) end, and crossing the loaf with "slices" provides a way to envision the different events across the multiple time lines.
Another way might be to envision a grid with multiple light cones all pointing in the same direction. As your world line moves, you are moving in parallel with multiple other world lines (in a true multiverse, an infinite number). Your light cones might intersect in the distant past or future (or even the near past or future if the world lines are close enough), allowing you to "see" events in otherwhen. It is not clear to me if you will be able to influence events in other when, although since you can see them and gain information, it will certainly "bend" casualty.
[](https://i.stack.imgur.com/4YNhy.png)
The standard interpretation of the multiverse is that each universe is independent and isolated from the other universes (which explains why you can't see into them).
This is pretty mind boggling as is, so I will leave you with an image of a sliced bread timeline or an infinite grid of light cones, while I make a sandwich and break out the Go set.....
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Currently there are 4 dimensions **w**,**x**,**y**,**z** if **w'** is your speed through the **w** dimension then the current rules of space time are
**w'^2>x'^2+y'^2+z'^2** and **w'^2+x'^2+y'^2+z'^2=1** this means that the speed you move through through time is greater than the speed you move through space. With 2 time dimensions to maneuver in it would be possible to loop around and go back in either time direction **w'^2+x'^2>y'^2+z'^2**
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What problems would perpetual fog cause to a country roughly the size and environment of Ireland?
The country has all modern infrastructure such as power plants, roads, factories, hospitals, etc.
For just over half the year the fog is very thick and only allows for around 200 m of visibility. The rest of the year the fog is mild, but the weather is often cold and rainy with odd days of sunshine.
The lengths of time the fog is bad is sporadic, sometimes lasting a few days others lasting a few months.
If any more information is required please let me know in the comments.
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First, visibility of 200 meters is really...really dense fog, reducing things to 50 meters is almost unheard of. This is especially true over the size of landmass you are talking about. I find that the idea stretches plausibility to the breaking point if confined to 'natural causes'.
That said a few things come to mind.
**The transportation network.**
* Aircraft. Weather you are talking about planes or helicopters both will be impacted, though helos likely more so as they function at lower, fog impacted altitudes. Landing larger jets would also be tough and it would pretty drastically impact an airport's ability to handle aircraft in any significant volume.
* Vehicles. Speed limits would be a whole lot slower, at least for half the year. This would impact everything from personal transportation to commercial goods transportation. Personal transportation could be outright banned during the foggy times of year for safety reasons, and transporting goods would get more expensive due to the increased amount of time it would take.
**People**
* Depression...well it would be like winter blues, but for six months at a time. I can see drastic differences in spending and such between the foggy and not foggy portions of the year.
* Tourism would be non-existent during the foggy time of year...
In short there would be major impacts on productivity half the year. Things would be slower and people less...awake so to speak. Though the six months fog free would probably be very vibrant and productive...so there you go.
Oh...and solar and wind power are not things that are going to function on this landmass.
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I see rail being an attractive transportation option, since visibility is less important when you don't have to steer.
Plants and Crops would also be effected, and imported warm weather food stuffs would be a big trading opportunity.
If you have to deal with low light half the year, then the plants will be the type that grow well in the [Taiga biome](https://en.wikipedia.org/wiki/Taiga), which has a growing season of around 150 days. There would be some differences because the temperatures are warmer than the tagia.
During the nice months crops would include a lot of cereals like wheat, barley, rye and oats, and fruits that have a short growth season. There might be isolated areas where geographic formations would cut down on the fog and allow for longer growing periods.
It would be a bit like Alaska, except half the year it would be foggy instead of deathly cold.
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To add to the answers a [autonomous vehicles](https://www.google.com/selfdrivingcar/) ill have a big boom. Even autonomous walkers can become an option.
But most effects on economy ill be drastic.
## Health
Humam body needs a bit of sun to produce vitamins, sun lamps can be a common place on house and even publis solariumns can start to popup. [Sun deprived depression](https://en.wikipedia.org/wiki/Seasonal_affective_disorder) become a major puplic healt problem.
## Aircraft
Airports and aircrafts demands expensive systems to operate at no visiblity conditions. Small planes and airports become impratical. The big airliners are not impacted.
## Emigration
People don't like to live that way and can depart to more sunny lands. Tourism to tropical contries become a wealthy business.
## Economy
There are a major impact in a lot of major crop cultures. Cattle is also affected even indoor flocs are affected by the lack of cheap ration.
## Culture
Indoor entertainment are the only option. Big indoor stadiums and event places arises around. The few sunny days become instant hollidays tahnks for flash mobs
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Imagine a large island, roughly the size of Australia. The sea around is is effectively endless: no-one from the island has found an edge to it, or any other land masses. This is a fantasy land, and the technology is roughly equivalent to dark ages Europe. So news travels relatively slowly.
There are a wide variety of different races and cultures on the island. All of them share a common motif, however, because it happens to be true: the island is still being shaped by the gods.
Let's take a practical example. A fisherman takes his usual route around the local coastline. After a few miles of everyday sailing, he comes across a surprise. What was once sea was is now several square miles of land.
If there are intelligent creatures on this land they will either believe they have always been there or that they and the local landmass have been uprooted from somewhere else and placed on the coast of the island. They will have memories of their lives and cultural traditions going back into the mists of time. These beliefs and memories are a lie. The reality is they were shaped by the gods and placed down in a moment.
These creation events happen perhaps once every couple of years. Each time, a few square miles is added to the island. It is normally on the coast, but not always: sometimes large caverns appear underground, or a previously impassable mountain range acquires a new, accessible valley. They always occur at uninhabited sites when no-one is around. The people in these new areas may belong to a race or culture already extant or they may be entirely new on both counts.
My question is: how are the various peoples of this island going to come to terms with the fact that none of them can be certain of their heritage? The fisherman is going to find a land which he is certain is entirely new (which it is), but the people of the land will firmly believe they've been there forever. So our fisherman will realize he can't be certain that his life history is real or whether he was created from nothing a year or two ago.
People who live in the ancient city on the center of the island don't know if it really is an ancient city, and that the history books in their library were written by their ancestors or made up by an imaginative god. The only thing that everyone knows for certain is that the gods began the act of creation and that they're still creating.
How will this affect people's cultural beliefs and practices? How will the existing inhabitants of the island relate to the sudden appearances of new cultures?
[Answer]
The reason this seems like it's a problem is that you're coming from a world where you can be certain about your heritage, and so that forms a foundation for your future experiences. The people here can't and will all very quickly realise that they can't, and so it will stop mattering after a short period of acclimatisation. To anyone already on the island it won't matter if their past is 'real' or 'imaginary'. They have their customs, they know they've popped into existence with heads full of history and cultural background, why should it matter if everyone else thinks they just appeared?
If it's a natural (well, godly..) and known phenomenon that new cultures occasionally appear then everyone already there will come to terms with it and move on with their lives, secure in the knowledge that unless a god is being particularly cruel their experiences are still going to be relevant to the place where they live. **Edit:** It's worth pointing out here that any new culture that thinks they've always been there will already have been exposed to this kind of thinking, and any new culture that thinks they've been transplanted won't be able to prove they were made up in the first place.
Religion will be as varied as the cultures, but with an unquestioning faith that the gods are still mucking about with the island as a unifying tenet of belief, it's possible that the Church of Impermanence (use the name freely) will rise to dominance. The Church of Impermanence would have to employ cartographers, diplomats and couriers, and could quickly establish themselves as the de-facto rulers of the island under the guise of keeping track of the changes made by the gods.
The issue will arise for the new cultures, when they arrive, not for the old ones. The two scenarios you gave are:
**The new people know they've always been there.** This will be the most confusing but least violent of the scenarios, as the New people will already have experiences in dealing with their neighbours. When those neighbours (the Old people) turn up and start acting as if they've never seen the New People before there will be quite a lot of confusion on the part of the New people. Cue the Church of Impermanence, who turn up with their heavy covered wagons and informative printed pamphlets to explain the simple truth that the world is being rewritten every day, that the old experiences are mostly still valid, and that everyone should basically just get on with their lives but accept that anything before X date is invented. There will be a few months of unrest as the situation settles down, then happiness will ensue. Unless of course the god in question made these people with a grudge against another culture, or a memory of a long-running war. Then things get nasty, but the New culture won't care about the Old one anyway.
The second scenario: **The people think they're been plucked from somewhere.** is less confusing, but has the potential to be more violent. The New culture here won't accept that they've just been created, they'll be convinced that they've been uprooted from elsewhere (they may have been, who knows?). In this case the Church of Impermanence has to act as an intermediary to explain that the gods are always pulling people from places or making new places, and that the New culture shouldn't worry. If the New culture want to get back home, or if they're imperialistic, they won't have the pre-built relationships with the new world that a 'we were here already' culture would, and so would be more likely to go on the offensive straight off the bat. On the other hand, they'd be a lot less confused. Again, after a little while they'd come to accept that they were stuck in this situation, and would start working with the Church of Impermanence to establish diplomatic relations.
One thing it is worth noting is that in this world Cartography is going to become a major source of industry and innovation.. Hail to the mapmakers!
[Answer]
Theres a few different possibilities that might arise from this situation. The first that comes to mind is **conflict**.
From what it sounds like, these people have no idea what parts of their lives are real and what parts are made-up. Depending on the people, some may find this situation difficult to grasp. People have good memories and bad memories: even relationships are mostly built on your memories. To find out that all of it is a lie is a pretty hard blow. The new cultures that appear would likely not even believe the story they're told. Their memories are the ground in which their beliefs firmly stand, and it's their beliefs against the others. This conflict could brew for a little and might even cause fighting, however this difference in opinion doesn't really seem big enough on its own to cause any major feuding or wars.
Although this conflict isn't quite enough to completely change society, it would definitely affect certain relationships, and contribute to the general worldview of themselves. There may be this certain sense of justice that arises, for example if one person was "created" by the gods as a beggar while others live more luxuriously, he may find it unfair and claim that he "deserves" more. Or maybe, as a culture, they have adopted the decisions of the gods as a final judgement, and than anything that is decided by the gods is fair and just and inherently good. This mindset would mean people would be more satisfied in their positions and would be less motivated to change their lives. Extremists may even push so far as to try to keep people where they're at.
Another possibility could be **acceptance**. It takes a lot of work to realize your life might be a lie, and then where do you go from there? Do you rebuild your life again? Most people would not go through that trouble, they likely already have a solid life built, and would simply continue to live that life. If they can't convince the new societies that their lives are fake, they'll simply stop trying. Every time a new society pops up, you get to know them a bit, see if you'd be good trading partners, maybe let them know about the gods activities so they're not surprised, then continue about your life. The conflict may simmer under the surface for some, and may break out after fighting arises, ("yeah well we were here before you anyway!" "no way you weren't"), but for the most part they can't really change what happened so they just accept it and move on with their lives.
] |
[Question]
[
# Background:
My evil 10,000 year old Nature Mage Erilius has escaped the desert and made it back to the furthest outpost in his Rainforest kingdom. Upon entering his makeshift Magic plant tower ,his large, Insectoid acolytes inform him that they discovered a powerful spell in his collection of magical scrolls. The power it grants him is…….teleportation! He can teleport instantly into any place within fifty feet of his original location. The only downside is that he has to wait for two minutes in between “jumps.”
He has heard news that Aran, our hero, has linked up with his Uncle, the King’s army, so he goes out to join his 3rd army of Felinus (a subset of homo Sapien more vulnerable to mind control evolved to have cat like features in the forest) on the field of battle. His original invasion force equaled roughly 3 million magic wielding Felinus. Aran has something he wants….Flaming Sword of Türbrik.
This sword has the power to create fire along its length and control said fire along with any other fire within a ten foot radius. The sword is not limited by the regular limits of magic (it has unlimited amounts) and the only limitations on its power is the ability to multi-task by it user and remain in control of the fire (which is directly correlated to your patience, sobriety, and self control). Legend has it that whoever holds this sword will save his species which is why the Nature Mage Erilius wants it so bad
His benevolent, magically-adept race solved our starvation by putting permanent fertility incantations on the fields. After the Elves and Humans grew in numbers they overwhelmed and destroyed his species for reasons unknown. He was the only one to survive and he fled across the desert to an unknown forest where he has resided, growing in magical power for millennia waiting for the right time to strike back and get his revenge by driving us to extinction.
He divided his army into 3 pieces of 1 million each and sent the other two to attack and burn the countryside in the human and elven kingdoms. He has 1 million soldiers. The Felinus all have magical powers (Which I will tell about in the *Magical Rules* part of this question).
The Felinus are arranged in a scattered formation (think about how the ancient Gauls went to war) along a wide plain.
A long, thin ridge overlooks this plain on which the Humans have centered their defense. The Human king has a combined allied force of 50,000 knights, 100,000 archers and 150,000 disorganized regular infantry armed with halberds, long swords, spears and pikes from both his and the neighboring human kingdoms. He has positioned his 20,000 pikemen on the lowest slope of the ridge. The 50,000 halberdiers and 30,000 spearmen are arranged in a near perfect line directly behind them. The knights are directly behind the lines divided into five units of 10,000 each and are formed into diamond formations prepared for a charge. The 50,000 swordsmen are positioned in the hilled forest on both sides of the vast field to protect the flanks. Each flank has a separate unit of 20,000 archers to back the swordsmen up. The king has positioned the rest of his archers (did I mention that they use the long bow) along the length of the ridge to rain down holy hell on the Felinus camp.
Upon seeing the entire 1 million strong Felinus army and learning from his scouts that the powerful Mage has entered the camp to join the battle the human kings in the command tent agree that staying here will be suicidal. After all, Erilius can control the trees and the animals in the forest which is where the flank defense is located. If the flanks fall the Felinus will surround and crush the human alliance here and now. The human coalition leaders (comprised of the kings and most powerful vassals) look at a map of the region and decide to retreat to an abandoned mountain fortress 75 miles to the north to make a stand.
Then an army of 10,000 Elven Archers/Magicians (Elves are naturally good at magic and have a set of powers to be described in the magical rules section) This significantly bolsters the human army. The elves decided to aid us after the Mage kindly removed the head from one of their envoys. My coalition still wants to escape to the mountain fortress and now the elves are here to help.
---
# Magical Powers:
I need to establish a few rules. First off is that there is a spirit world. All people go there when they die and there is a Heaven and a hell half. Most people achieve heaven, but the crooks of the world go to hell (people who like to steal, rape, and kill. People who have no choice go to heaven). The hell half is crammed to the brim and is watched over by Spirit Guards. The dead often escape and try to hide in the bodies of humans via possession, although most people have enough will power to unknowingly reject the evil spirit (even newborn children have they much will power).
Using magic weakens will power temporarily and the more you use it the more vulnerable you are to permanent possession. Magical prone races like the Felinus, Elves, and the Mage (the Mage moreso) have massive resistance to possession. Humans, Dwarves, Hobbits, Mini-Dwarves, and Fae are all vulnerable, however.
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Felinus powers:
* Blend in nearly perfectly with environment
* Change colors like a Chameleon
* Run like a cheetah (literally, dropping like a cheetah on all fours and reaching speeds of 112-120 km/h or 70-75 mph)
* Limited (four feet) telekinesis
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Elven powers:
* Levitate
* Fly for about five feet
* Blend in with environment
* Shoot flaming arrows
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Nature Mage Erilius’ powers:
Control all living things (both flora and fauna) within a 100 foot radius. He can cause plants to grow at near infinite speed if the conditions required for its survival and growth are met (i.e. Enough water and nutrients are present and there is sunlight).
* He has telekinesis
* He has limited telepathy (e.g. Those trained well enough can block him from their minds)
* He can fly up to 10 feet off the ground for a max of 1 ½ minutes.
* He can temporarily (think 10 minutes) assume the form of any known animal
* He can control rock and transmute it into any type of rock or mineral(think turning coal into diamond, granite into coal, or rock into iron)(kind of like the earth benders in Avatar The Last Airbender) but cannot reuse the same piece of rock (one and done, so to speak).
---
Aran Stronheart our hero has the following powers:
* He can fly like the Mage
* He can use telekinesis within a 30 foot radius.
* Use the Flaming Sword the Mage is after to make and control fire.
* Resist mind attacks better than others.
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Other Rules:
* Medieval tech level only (obviously)
---
# Question:
**What is the most effective (least deaths, less time for Erilius and his Felinus to catch up) way to get the army out of this suicidal situation and to the mountain fortress?** Take note that Erilius has spies ready to arouse his army if the humans are obviously fleeing.
---
# Linked:
[How to Escape a Horde of Worms Using Magic with Minimal Injury](https://worldbuilding.stackexchange.com/questions/12912/how-to-escape-a-horde-of-worms-using-magic-with-minimal-injury)
[How do I Draw the Elves Into the War?](https://worldbuilding.stackexchange.com/questions/12923/how-do-i-draw-the-elves-into-the-war)
[How to Defeat a Nature Mage?](https://worldbuilding.stackexchange.com/questions/12801/how-to-defeat-a-nature-mage)
---
# Map:
[Answer]
The humans run. The elves use their camouflage ability to hide, shoot from cover, and move without being seen and slow the Felinus and mage down. Guerrilla style. They also use their flaming arrows to start burning the forest behind them, weakening the mage and giving the Felinus something else to think about.
The human archers with longbows have a maximum range of upto 1200 feet. Give them horses and they could split into 2 groups, leapfrogging each other. First group fires, second group gallops 600 feet ahead, stops and fires several volleys while first group gallops past and goes another 600 feet. Proper use of terrain could help them a lot. And they only really need to leapfrog when the Felinus start to catch up.
The Felinus are fast, but if they are like cheetahs they don't have much stamina, so they can either move fast or move stealthily. Also, they have to get up the ridge, which would slow them down a little.
I've heard it said that a human can run 100 miles faster than a horse can run 100 miles... 75 miles is a long way, but these soldiers are used to walking/marching everywhere, and if they drop some gear like tents and such they could move fast.
The mage can control nature, but only within a radius of 100 feet, so he still has to be cautious since a barrage of arrows from hidden elves or humans would have more than 100 feet range, and would give him a bad day. His teleporting would help, but it only gets him 50 feet closer, and the 2 minute cool down would stop him from escaping quickly if the elves or humans target him. It's hard to dodge 10,000 arrows, and their range is greater than his.
IIRC, the mage got the Felinus cooperation by controlling the leaders, not the individual solders, so they might use caution instead of mad rushing. Especially if there is a firestorm from elven archers ahead/around them.
**Alternate:**
They make a stand. The mage is going to have his hands full managing that many Felinus, the human and elven archers could thin the heard a lot, and the mages range is actually pretty short compared the the range of a long bow. If the mage goes after the forests he'd have to deal with a lot of arrows, and since Aran Stronheart can fly too, he'd be able to counter/distract the mage en route. Having the high ground and the ridge gives the humans/elves a little advantage.
It would be tough, but not impossible, and that mage does have to careful of getting to close to the archers.
**Second Alternate:**
Erilius is after the sword, so Stronheart flies off another direction to lure the mage away, which weakens the Felinus army a bit. Gives the human army a better chance.
[Answer]
They could trick them into thinking they retreated. The goal is to avoid the imminent attack right? It doesn't matter if they actually retreated as long it's what the other camp believes. By the way when I say humans, I mean the whole allied bunch.
**Plan A**
Not necessarily the best, but I kind of liked it. The human/elves have to be under pressure, both camps know they are going to be attacked any day.
*First Subterfuge*:Humans leave minimal(sacrifice) or no forces on the ridge but place dummies to make believe they are still there. -This will be obviously figured out. And mostly likely will lead the felinus army to believe they are retreating
*Second Subterfuge*:Humans use the forest to advance into flanking positions. Some reports (or scouts that dont come back) warn the felinus army of their movements. All of a sudden the felinus army discards the whole fleeing scenario, it also explains why they didnt leave troops on the ridge, they need em all to match the size of the army below. (poor military plan - replace by any thats better, its not the point either way)
*Third Subterfuge*: There is no attack. The felinus prepares for it but it doesnt come. Instead the allies hide, using the forest and movement that was under very little supervision (because who expects a flanking attack to flee before it even starts.....)
*Result*: The felinus army that poorly kept track (or not at all) of the humans preceeding the expected flanking attacks simply no longer knows where they are and kept guessing as to which part of the whole thing was the faint. Maybe they just fled right off the start and the reports of the flankings were of a small detachment left behind. Maybe they used a spell. Maybe they are still about to get attacked.. etc...
I'm not entirely certain if some ability would make all of above redundant, but with numbers that large (on both sides), you can't conventionally "retreat" in any way.
It could be a diplomatic retreat (if the whole famine thing isn't 100% solved you could exploit that), or any other political stunt.
[Answer]
The lack of defendable flanks would result in an almost slaughter of the entire army. So how (using mundane means) would you fight back? Well first, the enemy’s “general” or guy you wold have to take out is a very powerful NATURE mage.
Rule 1: Avoid having to make any fight or flight where there are plants.
His limitation is definitely range. 100 ft? If said army had *any* good archers, they could very easily hit him at three times that length. If we assume his is the typical messiah or god complex victim, he also won’t be wearing heavy-type armor (plus casting in armor is way to hot). A simple flight arrow could kill him and an accurate shot could be made at almost 300 yards (900 feet or 274.2 meters) easily outside of the range of the resident evil mage.
Rule 2: When outclassed at a given range, find a range where you outclass the enemy.
Now, if we were talking his ability with plants was the only thing to deal with, the whole arrow idea is a great one. You have someone like Wil or Halt from Ranger’s Apprentice in your army, then thwang, one very dead mage. However, he also has telekinesis.
Rule 3: Telekinesis sucks to fight.
Due to this, you might have to get owl-fletched arrows or else he can hear and deflect it easily.
But, of course, a sniper shot to end the villain simply is just boring. So you want to have an army escape? Roman base the sucker. The humans have a great advantage here. They have basically as much wood as they want, plus the hero can make and control *fire*. Get a bunch of sharp pointy things (like 5-ft. long stakes) and barricade the front while scorching the forest around you. If you have horse archers (which works. Look at Native Americans, they hunted buffalo on horse back) you play leap frog with two squads. This allows you to A. cover your butt but also B. Thin their ranks as the rest of the force retreats. After a day’s worth of travel, nothing the Felinus army can do will catch up, they’re built for sprinting (read: like cheetahs), not cross-country.
] |
[Question]
[
Consider a dual-star system, with the distances between S (larger star) and J (smaller star) similar to Sun–Jupiter. A planet P rotates around J on a 90-degree ecliptic and is Earth-like otherwise.
Due to a tidal lock, one hemisphere of the planet permanently faces J. J is hot enough to sustain a comfortable temperature (say, 65°F = 20°C) on the inner (J-facing) hemisphere. S is hot enough to raise the temperature of the opposite (outer) hemisphere up to 100°F = 40°C when they face each other.
Questions, assuming a realistic dual star system:
* Is it feasible at all?
* How cold would the outer hemisphere become in a cold season?
* How many seasons would the inhabitants encounter, and what they would be like?
**EDIT**
The question was confusing indeed. By a 90 degrees ecliptic I meant the planet orbit is perpendicular to the stars orbital plane. As for feasibility, a heat from the stars surely imposes some requirements on their masses and distances to the planet; could a stable orbit exist?
[Answer]
Neil's completely right that the question is a bit confusing. There are two scenarios here: The planet orbits in the same plane as the stars, or it orbits 90 degrees perpendicular to them. There's a huge difference between the two setups. I have a feeling, though, that you're curious about the other, and I really can't resist launching into an explanation of them both, so I'll cover them separately.
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**Situation 1: The same plane.**
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> Is it feasible at all?
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Is it feasible? Of course. We know that planets exist in binary star systems, and some [may be habitable](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems). At any rate, though, it is important to discuss the difference between planets that only go around one star and planets that go around two. There are two designations for [planets in binary star systems](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems), based on their orbits:
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> Planets that orbit just one star in a binary pair are said to have "S-type" orbits, whereas those that orbit around both stars have "P-type" or "circumbinary" orbits.
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In your case, the planet only orbits one star. Nice choice; [circumbinary planets](https://en.wikipedia.org/wiki/Circumbinary_planet) (planets that orbit both stars) might have drastic temperature swings, and may orbit far out from the stars. I'd rather live on a planet with an S-type orbit than on one with a P-type orbit.
There's a reason that planets generally form on the same plane as their stars. It's because the system forms from a [protoplanetary disk](https://en.wikipedia.org/wiki/Protoplanetary_disk), which flattens out because it rotates. This is characteristic of most star systems. Check out [this question](https://astronomy.stackexchange.com/questions/2224/why-is-the-solar-system-often-shown-as-a-2d-plane) for a clear explanation. [This question](https://astronomy.stackexchange.com/questions/2387/why-planets-orbit-is-not-perpendicular-or-random) is okay, too, but I don't think the answer properly addresses this issue. There are exceptions to the "same-plane" rule, but at the moment I can't find them.
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> How cold would the outer hemisphere become in a cold season?
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This is hard to figure out because there are a lot of factors that you don't have. For example, do the stars' orbits have low eccentricity or high eccentricity? What are their [properties](https://en.wikipedia.org/wiki/Stellar_classification)? I'm not sure how to figure this out, given that we only have information for one position.
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> How many seasons would the inhabitants encounter, and what they would be like?
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Currently, you could draw inspiration from [this question](https://worldbuilding.stackexchange.com/questions/176/is-it-physically-possible-for-a-world-to-have-seasons-of-different-lengths), which has a lot of interesting answers. Unfortunately, only a few address binary-star-scenarios. Common sense, though, tells me that, if the orbits of the stars have relatively small eccentricities, the planet would have odd seasons. Remember, we have seasons because of the tilt of the Earth's axis. I think the planet would have seasons primarily caused by the tilt of its axis, and that the other star really wouldn't play into it very much. You can find relevant questions on Astronomy [here](https://astronomy.stackexchange.com/questions/6635/is-earths-orbital-eccentricity-enough-to-cause-even-minor-seasons-without-axia) and [here](https://astronomy.stackexchange.com/questions/6617/would-an-exoplanet-without-axial-tilt-have-no-seasons). However, the tidal locking could impact the seasons.
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**Situation 2: A 90 degree tilt.**
[Uranus](https://en.wikipedia.org/wiki/Uranus) springs to mind when I think of this scenario. It's [tilted](https://en.wikipedia.org/wiki/Uranus#Axial_tilt) almost 100 degrees from the "horizontal" - or about 80 degrees, from another perspective. Its rings, therefore, can be a good model for this planet. Well, not really. But they can give you a good picture of its orbit.
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> Is it feasible at all?
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I'm going to go with no for this one. Why? Uranus is tilted at such a large angle possibly because of an impact with another object. For this scenario to work, you'd need to have the protoplanetary disk of the primary star tilted 90 degrees, which is implausible.
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> How cold would the outer hemisphere become in a cold season?
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This is rather easy. Assuming the stars orbit each other at low eccentricities, the planet would always be the same distance from the other star, so temperatures would be constant. This means, though, that one hemisphere would be perpetually warm, while the other would be perpetually cold. It would be tidally locked - to both stars!
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> How many seasons would the inhabitants encounter, and what they would be like?
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It follows that the planet would have seasons just like any other tidally-locked planet.
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You might find [this](https://worldbuilding.stackexchange.com/questions/456/how-would-two-planets-with-identical-but-perpendicular-orbits-affect-each-other) question interesting. And [this](http://arxiv.org/pdf/0705.3444v1.pdf) pre-print is quite a good read.
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**Edit:**
As per your comment:
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> I also don't see why the planet should be locked to S. Even so, the outer hemisphere is roughly half of the time exposed to S, and roughly half of the time shaded from it.
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Think about it like this:
One pole of Uranus is generally pointed towards the Sun. This is like the axis of revolution of the planet being pointed towards S. Now, imagine the Earth-moon system. From someone looking "down" on the system from "above" Earth's North Pole, how many sides of the Moon are visible? Only one hemisphere. S is like this observer, looking "down" on the other star and planet.
As for capture - sure, the planet could be capture by the system. There are two problems with this:
1. It would be very hard for the planet to be captured by the star and become tidally locked. Tidal locking is generally an indicator that the objects have a pretty close history.
2. Given that S is more massive, it would be more likely that S captures the planet, and not J. Sure, J has a fair chance of getting the planet, but S would probably have bigger influence.
[Answer]
If the planet is tidally locked with its primary. then the center of the planet facing gets a huge amount more solar energy than the rest of the planet. If this rise in temperature is too high, the atmosphere escapes and the planet is lifeless.
To avoid this, temperatures would need to equalize between the hot spot and the cold spot on the far side of the planet. The only way to do this would be wind. With our 23 degree tilt producing icy winters and hot summers on Earth, and major storms, this far more extreme situation would require extreme winds. They wouldn't turn into hurricanes like on earth, which are formed by the spin. But presumably some kind of huge cell system would create high winds circling the planet from front to back and back to front. These might never vary once formed!
The third star might affect the situation. In the case you cite, warming the back of the planet might cut the wind, but make everything hotter.
] |
[Question]
[
On a planet with no water or oxygen or anything to react with the sulfuric acid, what color would an ocean of it be? I know sulfuric acid is clear, but water is also clear, and oceans are blue, not clear, so what color would a sulfuric acid ocean be?
[Answer]
The information required is the visible light absorption spectrum of pure sulfuric acid, but unfortunately this seems to be a very difficult thing to find. Plenty of stuff about UV and IR absorption spectra out there, but no visible light information. Without that, you can't really work out what color the stuff will be in bulk. You might have more luck asking the chemistry stackexchange.
I'm going to write an answer anyway, because this matters less that you think it does.
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> on a planet with no water or oxygen or anything to react with the sulfuric acid...
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Problem one: sulfuric acid contains all the ingredients you need to *make* water and oxygen. Subject it to the right environment and the stuff will just start appearing for free! Consider [UV and visible light photolysis](http://www.issibern.ch/teams/venusso2/multimedia/pdf/Zhang_10b.pdf) for example, which converts sulfuric acid in Venus' atmosphere to water and sulfur oxides. You get recombination of course, but there's always gonna be some water there.
Problem two: pretty much *everything* reacts with sulfuric acid, and the universe is full of things which which just love to react with acid. The planet on which your ocean is found has a good chance of containing lots of metals of various kinds... the solar system is full of iron and aluminum, to name just two examples.
These metals react with the acid to produce brightly colored sulfates in solution, so unless your acid world is basically a frozen snowball at the outer edge of a planetary system it seems likely to have red or orange or brown tinted oceans, reflecting skies tinted brown by sulfate aerosols.
[Answer]
Many years ago I happened to be walking around a long abandoned mine site that mined pyrite (iron sulfide FeS2) during the 1950s. The site contained numerous piles of waste material that contained unrecovered pyrite.
When rain fell some of the pyrite in the piles of waste would oxidize and form sulfuric acid. Pools containing the run-off had a reddish tinge, similar to pictures one sees of [Rio Tinto](https://en.wikipedia.org/wiki/Rio_Tinto_(river)) in Spain.
[](https://i.stack.imgur.com/AmaXj.jpg)
It's easy to see why the Spanish call it Rio Tinto (The River Red)
**Pure** sulfuric acid in a **glass** container will be clear because it is not reacting with anything.
The color of the acidic waters in the environment will not solely be due to the color of sulfuric acid. They will also be tinted by minerals and metals that have been dissolved by the acid.
The reddish pools I observed were in "soil", more accurately regolith, a geological substance. Waters of Rio Tinto in Spain also contain minerals and metals from the river bed and walls of the rivers; again geological substances.
A sea of sulfuric acid, where ever it is, will be be contained by geological substances - rocks that contain minerals. The acid of the sea will react with minerals and metals of the rock containing the sea and give it a color. If that containment geology is mostly igneous (derived from lava/magma) it will contain iron and hence it will have a reddish tinge. How red, depends on the amount of metals dissolved in the acid - the more metals the more deeper the shade of red.
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I'm designing a flat world setting for a fantasy RPG, and I'm trying to figure out out how the climates and weather patterns would play out realistically (or at least semi-realistically) in such a setting. This world is built on a shallow vessel, and has one large, roughly circular continent 7,700 KM in diameter with around the same land area as Africa. Tall mountains, the height of the Himalayas, take up the continental center. This continent is surrounded by a single ocean which is slightly larger than it by area. 45% of the world is land, and 55% is ocean. The entire world is covered in a transparent hemispherical dome of opalescent crystal that spreads light via Rayleigh scattering, which keeps the atmosphere/humidity in. Everything is placed upon the back of a cosmic entity, which provides earth-like gravity.
The sun orbits this entity and moves over the domed world from East to West, and is directly overhead in the Northern Hemisphere (the equivalent of an equatorial region); it shifts position Southward to simulate seasons. (Edit: It is important to note, however, that this "sun" is a deity and not an actual star, so it has no noticeable gravity by itself. Otherwise, the temperature and luminosity are the same from the perspective of someone on the world.) This world does not rotate, and there is no Coriolis effect.
With these factors in place, I'm expecting a small number of air cells (not quite Hadley cells) and air temperatures that are more homogeneous than Earth's. The total surface area is only around that of the moon Callisto. Most winds would arise from the difference in sun strength between the Northern and Southern hemispheres, but would circulate within the dome. **What would the weather be like in such an environment?**
(Edit: Refined the question to be about weather only.)
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I'll assume a hemispherical (or nearly so) dome, as it's the easiest for me to imagine, as well as providing room for air currents to have more effect than a flatter dome would.
In general, a flatter dome would produce more stagnant weather patterns. Since hot air can't rise as much, convection drops, and with it circulation. You end up with things just getting hotter, and muggier from evaporation from oceans, as the day goes on. And then reversing with nightfall, cooler tempuratures, and moisture condensing out of the air, most likely as fog/dew/etc. rather than clouds, since there's not as much room for dewpoint variation with altitude.
But in a more hemispherical dome, there's room for hot air to rise, warm air to move in laterally to replace it, and cool air to descend to replace the warm air.
Air over land masses generally heats faster than air over water. So the most prominent daytime winds will almost certainly be blowing inland from the sea, as the air above the land is heated, causing it to rise, and the warm air from above the sea moves in to replace it. This will likely be slightly exaggerated in equatorial equivalent regions, where the sun hits most directly, and lessened in polar equivalent regions with less direct sunlight.
As the air moves in from the sea, it will bring moisture with it. As it's heated, it will rise and start to cool as it moves farther away from the land. It is also likely be deflected upwards by the mountains in the middle of the continent. As it cools, this will cause the moisture in the air to condense in to clouds, and possibly precipitate rain or snow. If there are other outlier mountains, separate from the main set in the center, those would cause clouds and rain before the moist air reaches the central mountains, but only in the areas where mountains are in the path of the moist air (see [rain shadow](https://en.wikipedia.org/wiki/Rain_shadow)).
Unless there is a (mostly) complete secondary ring of mountains outside the main range in the center, a good portion of the moist air will reach the central mountains before losing most of its moisture. This will give plenty of opportunity for rain/snow on that central range.
Here's where things will get complicated. I originally assumed that since most of your question seemed to be leading toward an Earth-like environment, that you intended these mountains to be snow covered. And to accomplish this, the inner surface of the dome would have to absorb heat from the air that reaches it, at a rate that is in an approximation of Earth's atmosphere bleeding heat in to space, making upper climes colder. However, if the *entire* inner surface of the dome accomplishes this, then oceans in contact with the dome would freeze over, and the air inside the dome would be colder the farther from the central mountains you get, even at lower altitudes, which is decidedly NOT Earthlike. The hot air that rises near the center of the continent and dome would reach the top of the dome and start to cool off, and start trying to sink. It would not be able to sink down through the hotter updraft, so it would spread out sideways in all directions, keeping it in close contact with the inner surface of the dome, accelerating the cooling process (whereas on Earth, air would generally start to heat again as it descended). This would cause it to fall even faster, etc. Until it contacted the ocean, at which point it would be pulled back toward the center of the continent, to replace the air blowing in from the sea and rising over the land. The repeated cycle would continue to accelerate as the day goes on, until hurricane force winds blow in from the sea, with the air being quite frigid, having been barely warmed by the sea before making landfall.
If, however, the dome doesn't suck heat out at the same rate along its entire surface (say, the lower area is heated by the same cosmic entity that's providing gravity), the cycle would be much gentler and more Earthlike.
At night, the entire process reverses, since land cools more quickly than sea, and early in the night the sea will be warmer than the land, and air above the sea will start rising up the inner surface of the dome, which pushes it toward the center, and then will start descending once cooled. The downdraft will be focused primarily over the central mountains, but it's unlikely that the moisture will stay in the air long enough to precipitate over the central mountains themselves. More likely there will be a ring of coastal rainfall before the air climbs higher. When the downdraft hits the central mountains, they will deflect it outwards. The air above the main land of the continent will also be drawn outwards to replace the air rising above the sea, and the wind direction will change to be primarily blowing from the mountains to the sea. Unlike the daytime, this would be more pronounced over the already cooler polar equivalent regions of land, and lessened in the equatorial equivalent areas.
[Answer]
Without any rotational forces and with solar energy being scattered by the dome so there isn't a true sub-stellar point the weather in such a setting is, ignoring magical/deific effects, going to be dominated purely by local circulation cells directly controlled by interactions between topography, aspect, and vegetation and insolation.
In many ways the weather of this world will resemble the local rain loops seen in many larger rainforests; the heat of the sun evaporates local moisture during the day and as the atmosphere becomes saturated, possibly as it cools in the evening, that moisture falls back out as rain often directly onto the vegetation it evaporated from just hours earlier. Sun-facing hillsides, dark surface, large bodies of water, etc... are going to soak up relatively large amounts of solar energy and create updrafts that draw in moisture and create cloud masses. Without larger, organised, circulation systems clouds aren't going to move in any particular direction from their area of formation so the clouds will get heavier until the updraft can no longer sustain them and then dump their water back onto, or at least near, the area where much of it originated. Winds will be local, relatively gentle, and blow towards updraft zones during the day and towards water, where the updrafts will continue, at night.
[Answer]
not an answer to the question, this is a comment that requires a visual aid to be clear.
The use of a full hemispherical dome that is opalescent, causes an unexpected problem with illumination.
Before dawn, and after dusk, while the sun itself is below the horizon, it is still shining happily on the dome on that side.
The dome reemits this light in all directions, thus lighting up the *whole* disk to a certain extent.
Depending on the distance of the sun, your disk will spend a **lot** of its time basking under bright overcast sort of light, even if direct sunlight does not reach.
[](https://i.stack.imgur.com/s6lCn.png)
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For the purpose of a story, I'm having an additional island in the North Sea. The island is where the Doggerbank used to be, but a bit larger. The highest "mountaintops" are around 1000m, but a lot of the country is between 1-50 meters above sea level. The island has two mountain ranges. The land usage is mostly agricultural areas, with some larger forrest areas, and several swamp areas. I've provided maps below (except for the land usage) for better visualization.
My question is, how would such an island influence the weather/local climate/tides?
My guesses:
* the mountianranges would probably influence the winds/rainfall considerably, so dryer climates/less rain in Denmark and Germany's north?
* With spaces between lands much narrowed down, tidal heights would drastically increase, more to what can be seen in the English Channel?
* the existing Dutch and German islands might be influenced in their existence, as they are sand islands
* On the new island itself, the lowlands would get a lot of rainfall, while the area behind the mountains would be dry
* Weather systems would probably take a different course altogether, but I have no idea what that would look like
Is this plausible, or would the changes be different?
EDIT: Added natural currents imposed over new island
EDIT 2: Based on the comment, I also add this question: What do you think is a sustainable island size that wouldn't cause total havoc? Reducing it by half, splitting it up into several islands?
[](https://i.stack.imgur.com/QPmGn.jpg)
[](https://i.stack.imgur.com/nX84f.jpg)
[Answer]
## Not that much
## Deep currents
Honestly because the north sea is so shallow and because the submerged doggerland island is still there, the deep north sea currents will barely be affected. Here are the real north sea currents.
[](https://i.stack.imgur.com/gqXvr.jpg)
All you really lose is the central north sea current which is pretty minor.
## Surface currents
Now these will really be bothered but predictably a lot of the central surface currents just wont exist. you will have the great north sea eddy but widened shifted a little west and that is about it. All this will generate less evaporation so the surrounding areas may be come a little drier.
[](https://i.stack.imgur.com/3J16Y.png)
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## Premise
The task is to explain how a planet can possess cube-shaped mountain ranges and maintain them across geological time scales. I have tossed around several ideas, such as creating a vacuum around the mountains. While none of these ideas worked out, I was able to construct a list of some of the main issues with cube-mountains:
* Atmospheric weathering
* Tectonics (plates colliding creates pointy mountain formations)
For a moment I had resigned, thinking it was too difficult to explain with natural phenomena. Then this photo reinvigorated my efforts:
[](https://i.stack.imgur.com/nh9WBm.jpg)
This site in South America is by no means the norm for planet Earth; it even remains a bit mysterious. Nonetheless, it serves a proof of concept: there can be natural processes that counteract other natural processes which would otherwise result in pointy mountains.
## Question
If we aim to have an entire world where cube-shaped mountains are the norm, then what natural processes need to be in place to maximize the likelihood of cube-shaped mountains, planet-wide?
**Further Clarifications**
* Interested in the long-term, if the mountains need to be pointy in the beginning, that's permissible
* Slightly less compromising with regards to shape, the success metric needs to be near-cube in shape -- not just non-pointy (normal weathering will flatten sharp peaks)
* Planet characteristics: [earth-like](/questions/tagged/earth-like "show questions tagged 'earth-like'") to start with, but can add elements from exoplanets if needed.
[Answer]
# [Tessellated pavement](https://en.wikipedia.org/wiki/Tessellated_pavement) on a volcanic scale:
Okay, I'll admit this a bit out there, but it's a fun problem. the geological formations that form tessellated pavement involve a flat shore and differential laying down of materials often as a result of tidal activity. Geological processes of erosion and sedimentation create differentially dense rock deposits. Regular, fairly straight lines form and crack at intervals, resulting in rectangular structures.
But what if we scaled this up? A planet with a really large volcanic event akin to the [Permian extinction event](https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event) poured a sea of lava across a large flat landscape over an extended period. If this planet had very extreme tides, then the "waves" of lava from this tidal action could be deposited unevenly with fill like pumice "washing up" in lines across the geology.
The eventual splitting of this overlying solidified lava along regular faults caused by this fill would allow the cracks to grow as the fill then dissolved out from between the waves. Miles-wide slabs of hard rock might then form a regular series of rectangular flat plateaus.
[](https://i.stack.imgur.com/dv1rV.png)
[Answer]
The easiest way to accomplish this would be some geological thrust function that produces sheer cliffs, like a convergent plate margin. However, this might not produce exactly cubic-shaped mountain, because you would have one end with a sheer cliff but that end would gradually taper back down into the earth, rather than having a random cube sticking out of the ground.
Your problem isn't geology, but physics. All materials have what is known as the [angle of repose](https://en.wikipedia.org/wiki/Angle_of_repose#:%7E:text=The%20angle%20of%20repose%2C%20or,0%C2%B0%20to%2090%C2%B0.), which is the steepest angle a loose pile of any one material will form when allowed to aggregate under gravity. Above this angle the downward force of gravitational pull is greater than the frictional force keeping the material together, and so the material will slump down and redistribute until the material is in a pile of the appropriate angle. This is why mountains are triangular or dome-shaped.
Under Earth-like conditions the angle of repose for most material is at a maximum of 45 degrees. I don't know how extraterrestrial conditions would alter this, but I doubt it would be possible to have a pile of loose debris achieve a pile of 90 degrees (which you would need for a cube-like slope) unless you were outside of a planetary gravity well and in outright microgravity.
Alternatively...
[](https://i.stack.imgur.com/r3UIh.jpg)
[Answer]
The mountains could be made of shale or a shale like material.
[](https://i.stack.imgur.com/ema8k.jpg)
As you can see shale forms layers of sheet rock which when broken can form rectangular edges. Another method would be plateaus.
[](https://i.stack.imgur.com/bt3g0.png)
This is a famous landscape in Venezuela called the Tabletop mountain or the Tepuis of Venezuela.
You could combine both of these geologic formations to make a blocky mountain.
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I am building a science fiction world 100+ in the future with various human augmetics. One of the things I would like to do is speed up human thought. My preferred mechanism for embedding this material is nanites.
From what I gather Increased myelinization increases signal speed within a neuron. The way I propose to accomplish this is to embed additional insulative material into existing myelin sheaths.
Is this possible? Is there, even speculatively, a material that would allow me to do this? Is there another mechanism that would allow nanites to modify existing neurons so that they fire faster?
[Answer]
I think there might be another way. Increased myelinization is not going to help much, since signal propagation *delays* are an integral part of the extant network and the way it works. Increasing transmission speed might just get you a migraine or a case of the *petit mal*.
But we're now, in 2020, experimenting with *neural plasticity*. What this means is - most brain cells are not born for a specific purpose; rather they are *recruited* by the various neural structures, and undergo [pruning](https://en.wikipedia.org/wiki/Synaptic_pruning). This is how someone might recover from brain damage: different structures are re-recruited and re-purposed to take the role of nonfunctional ones.
One of the several ways this could be used is in curing dementia, brain damage and Alzheimer's Disease.
But what would happen if we were to supply fresh, recruitable cells - *or cell analogs* - to a working, healthy brain? If the brain had need of that extra power, it would recruit those cells just like it did through infancy and adolescence. Except that now these cells' performances do not need to match those of a real neuron; the existing brain will just leverage and integrate whatever response patterns the new cells show, without "knowing" or "expecting" them to perform in any particular way. In time, this provides more raw "brain power", and may supply extra features.
New artificial cells - your "nanites" - can first help, then learn from, and finally duplicate and replace the old cells, one at a time. Once a sufficient volume of the brain is running on artificial hardware, closely emulating a real human neural network, nothing stops you from speeding up the clock.
There are other possibilities too: for example, the cell replacement can go on forever, providing what is in effect immortality. Also, when the whole brain is actually a large bioengineered artificial network, you can send a signal and have each neuron instantly "freeze" its state, while autonomic functions get emulated elsewhere. Each neuron can now be individually contacted and its state read, taking a "snapshot" of the whole large network. Then the brain is un-paused, but a backup has been created with the information required to reassemble an identical network and prime it with the same data.
Also, with the information supplied by the first "neuristor" cells, it would be soon possible to create artificial memories. An artificial short-term memory is working knowledge: imagine looking at someone and immediately *remembering* all useful available information on them, from the name to the last known occupation or any notes you might have made. Fast integration of knowledge on this scale would provide something very similar to genius-level intelligence, if not yet intuition.
[Answer]
You could try to synthetically copy the mechanism that builds the insulation in the development during pregnancy.
Here the enzyme FASN (fatty acid synthase) is critical to built from fatty acids of different kind and in the right amount each, the lipid rich membrane structure called myelin, that enwrappes the axons. ([source](https://pubmed.ncbi.nlm.nih.gov/31063129/) )
So your nanites need the right amount of every lipid, and the FASN as tool to built up more of the myelin. No special insulating ingredients are needed, because you built up onto an development, that showed it's effectiveness for millions of years.
If you insist on a new material, then use some new advanced lipid (fatty acid), that would be the saves way, to fit into the system and not causing side effects.
[Answer]
### Better insulation does not mean greater speed.
Your idea of improving insulation would not have any actual benefit because neuron, as they are, are well enough insulated by myelin. In reality what myelin does is separate parts of the neuron that can be excited (i.e. activated by the electrical signals) from parts that can not be excited.
>
> Imagine dominos. If you have small, 5cm dominos and place them in order it would take a
> certain time, and a certain amount of dominos to cover an area. It would also take some time between the time the first and the last domino fall.
>
>
>
>
> Now imagine the same are covered with taller, 1 meter dominos. It is harder to make then yes, but you need less of them. Also, you have less dominos hitting one another and this leads to the overall time decreasing, but not necessarily.
>
>
>
There is a limit, a sweet spot, between size and speed where both can be maximized. The same thing happens in neurons but instead of dominos, there are myelin blocks, and instead of domino "hits" there are nodes of Ranvier.
### There are other far more important bottlenecks to be concerned with.
Only now that we have a basic understand of how signals are propagated, can we see of the real bottlenecks. If you looks closer at the physiology, the really are two places where bottlenecks can be spotted: tramission in the neuron (between the nodes of Ranvier) and between neurons.
*For transmission in the neuron*, all that matters is ion channels. The problem is they take time to reset after being excited. Its the same thing as pressing a button. After you press it, you need wait for the button to go up to press it again.
*For transmission between neurons*, its all about neurotransmitters and receptors. This is a fancy way of saying how many messengers are available to deliver the signals (neurotransmitters) and how many mailboxes there are (receptors). There are several problems; the neurotransmitters can be used up quickly, there can be too few receptors or the receptors can become desensitized (don't respond as well to the signals that reach them as they should).
You have a lot of things to toy with if you focus on the two fields above. I can absolutely picture a **drug that targets the receptors** and makes them respond more lively to the signals as a solution to your problem.
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[Question]
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This is a submission for the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)
In the story I’m writing there is an island of mostly [Monotremes](https://en.wikipedia.org/wiki/Monotreme) which have diversified into a variety of ecological niches with a group of platypuses evolving into Manticores (here’s a rough mock up of what one of these [Manticores](https://i.stack.imgur.com/3TQbF.jpg) might look like with a smaller tail)! Now some characteristics of these Manticores include:
* lay eggs (of course)
* having a lion like body
* males have a cross between a lions mane and humans beard
* having bat like wings as their forelimbs
* are tetrapods instead of Hexapods like classical Manticores
* having a scorpion like tail
* being carnivores
* 25% smaller than a mountain lion
* are quadrupeds
* having a surprisingly humanoid looking face (optional)
* are capable of flight
Given these characteristics how realistic are they, and what evolutionary pressures would lead to such a beast?
[Answer]
# Size
To me, the first issue is size. You've probably heard of the cube square law? As I understand it, for flight, there is a fifth power square law. Flight is hard, especially if you are massive.
The largest fliers at this point are some of the eagles. Huge wingspan, hollow bones for weight reduction, and mostly limited to soaring. The largest mammal fliers would be bats, which are cited as being the size of a small fox.
Thus, I doubt your creature could be much larger than a house cat.
# Flight
It is probably mostly restricted to gliding and soaring.
If it can run, it can probably run faster than it can fly.
Indeed, that may be what it must do to get in the air.
# Sting
I would expect this is normally used from the air.
Thus, it would sting downward and forward, between the hind legs.
The tail might well be carried high when on the ground, and thus resemble a scorpion.
The tail might also have some flight surfaces to it, giving it an unusual appearance.
# Diet
It would need to be high energy.
Good candidates: meat, fruit/seeds, blood, milk. Probably only one, as each gets you a different jaw.
## meat
A jaw designed to tear flesh. Probably dog or cat like.
## fruit/seeds
A jaw designed for crushing.
Probably lots of teeth, though maybe none and a digestive tract that does the work instead.
(Some birds do this, probably for weight reasons.)
## blood
The ability to induce bleeding, and suck on the blood.
This could get a human-like face.
## milk
The ability to suck on the milk.
Possibly no jaw to speak of at all.
This could easily get a human like face.
# My thoughts
Personally, I like the idea of a milk drinker. If a large grazer has developed that both the females and the males lactate, and do so all the time, then the food source is good.
At this point, the sting could become a sedative or paralytic, used to obtain access to the milk without killing the beast.
This could develop into a mutually beneficial relationship, if the "manticore" acts as a high sentry for the herd, warning of approaching predators.
If such a relationship has gone far enough, the sting might also be used for protecting the herd.
[Answer]
A manticore could have evolved from a therapsid that evolved to be similar to the carnivorans. They might also have a long tail to defend themselves from other predators. They might evolve to have a bony ridge formed from the caudal ribs, which might later evolve into extended spines. It might also evolve to secrete poison from its skin, to further protect itself. They might evolve quills to protect the body. These quills might become hollow in order to deliver the secretions as venom. Some quills at the end of the tail might evolve to spray out venom. This would lead to these quills increasing in size, and the power of the spray increasing. At some point, they may evolve to produce a plug to plug the quill, which would allow pressure to be increased in the quill's base and allowing the quill to be shot out at high speed. These quills would likely take on an arrow-like shape, allowing better flight. The other quills of the body would be reduced, as they are less needed. They may be hit by a mutation that causes them to form many extra teeth. These teeth might move in the jaw to form 3 rows of teeth. Due to the increased amount of points in the mouth, they might be less able to tear up food. To avoid this, they might start to pick up prey in their mouth and swallow it whole. This would likely lead to the jaws becoming wider and the lower jaw spliting. Due to being less needed for biting, the jaws might shorten to a near-human face. They might evolve to produce loud, trumpet-like noises in order to attract a mate, and might also become bright red with a thick mane and bare face, due to sexual selection. These changes would make a manticore
[Answer]
Platypus
Definitely a platypus. They are one of the only poisonous mammals. Your scorpion tail is is a lion like tail with a big poison barb on the end. Bat wings fit well enough with a mammal - tbh I'm not convinced that we don't have a great real world explanation for bats since any intermediate species from rat to bat seems like it wouldn't make it, but bats are real so there you go. Human-like face... large eyes up front make sense for an apex predator, but for a human-like appearance you'd need a small nose/weak sense of smell. I'll be honest. I don't know why human noses suck compared to a cat/dog/bear, and a quick google search didn't turn up much. You could just hand wave that part. Finally for you to have a big flying predator like this at all you need a lot of big animals for it to pounce on from the sky and devour. High CO2 content in the atmosphere ought to help with that. Dinosaurs could afford to get so huge because food was plentiful. At 2000ppm plants grow like crazy, the herbivores can afford to grow larger, and the predators grow larger as well.
[Answer]
Okay, lets try and have some fun. We will start from a Lion Base type and address the two main features
1. Wings and Food Source
For wings to develop you need to be able to use them. This means you need to be lightweight but also means that your food supply is spread over a large distance or far away from Home. You might also notice that creatures that have wings only have 2 legs... this is due to the huge amount of energy required to invest in an additional set of limbs. From this, we can assume there there are seasonal bursts of abundant food to fulfill this energy requirement. One which is on land, requiring legs to hunt and where flying would not provide an advantage. Another which would be either very far away... or water related (think of sea birds).
Focusing on the first land based abundant food source where wings don't help. Your Manticore would need to be hunting large animals. It has powerful legs to attack and pin the prey and jaws to bit, pin and tear away at the flesh. Its wings are useless here because it needs to engage in a fight (Most birds only attack animals that are smaller than them) and can't just quickly pick off/up the animal. Otherwise, its legs would be more bird like, instead of sturdy and muscular (think of eagles lifting up sheep compared to a lion pinning down a wilder beast).
Now the second abundant supply of food. This would need to either be sea based or spread over a large area. I'm going to choose spread over a large area, something like multiple localized explosions in the rabbit population (probably caused by a seasonal weather of some sort). Your Manticore would use its wings to fly into the location, feast on the local population very easily and then move onto the next location. The stinger tail can be tied in here, as a way to dig rabbits out of their tunnels, but more on that later.
2. Scorpion tail
This is hard to determine the use of. In your image, the body is far too large for the tail to be used like a traditional scorpion stings (over the head) due to its length and size, and its hard shell would develop completely differently from a traditional insect due to the lion biology. Instead of being a shell, its likely that the shape and material would be a hard hair or bone like material. The stinger wouldn't be used to disable its prey, because otherwise, the Manticores power limbs become a bit redundant. The tail will likely be used to swing from side to side and would probably be shaped and grow that way due to mating preferences instead of having an actual utility (there is no way a tail would develop enough flexibility to act as a proper 5th/7th limb). The only purpose would be as previously mentioned, if its prey lived in holes, the Manticore could potentially use its tail to flush them out.
3. Humanoid face?
I don't think think this part can happen. A human face focuses on prey infront of it, but your Manticore would need to have a mix of bird and lion to be able to hunt prey and have some sort of useful vision when searching for its second food source. It would also need a stronger jaw structure to be carnivorous and you obvious end up with some sort of snout (looks at cats and dogs in general).
Unfortunately, I can't pin exactly where the wings would develop (as mammals wouldn't develop wings in addition to their 4 limbs, and birds won't develop arms). So it would have to be a completely separate evolutionary line from either of the two and I don't know enough to figure out where this split would have occured.
[Answer]
If manticores have hair like mammals, yet lay eggs like reptiles, they could possibly be a highly derived form of therapsids, mammal-like reptiles from the Permian era. Perhaps a species survived the Great Dying and adapted to hunting flying creatures, such as pterosaurs, by developing wings and a venomous spur at the end of their tail.
[Answer]
For a completely different answer...
Many of the functionality statistics you list you get for free with an insect such as a grasshopper or cricket. The stylistic facts such as the body shape and appearance could be covered by mimicry or intimidation. Alternately, you could start with a scorpion and get the tail for free... but not the wings. As a bonus, you could even get a hexapod design if you wanted - or if you really like tetrapods, the smallest limbs could be vestigial.
For this to work, the biggest problem is going to be size. Historically, there were some large flying insects, but I don't think anything was that big and dense.
[Answer]
A manticore (or a creature like it) could evolve by this path:
The manticore would start out as a small herb with a particular structure. This structure would be a central stem with small infloresences along each side
This herb would need defences. One novel adaptation could be for some of the leaves to harden into plates, forming armoured rings around the stem and infloresences. The infloresences' stems could also expand into long, venomous thorns, which, with a bright red warning colour, would ward off predators well. Smaller herbivores might be dealt with by a coat of porcupine prickles. A final touch, assuming the energy is there, is that the stems and leaves could bend away from touch. Another thing this herb would need is to distribute seeds. One idea would to be for the seeds to be ejected from the plant through a small explosion, like a gun
The monotreme part would come in here. A simple bug-eating, a common victim of predation, would benefit from the herb's defence. However, living near these plants will earn them quite a few seeds in their body. This can be a positive: if these animals evolve to support the plant, perhaps at its tail, then it can take the herb's defences for itself. This would also help the plant, as the monotreme can move further than the ground. This mutualism would grow stronger, with the herb losing its leaves when in the monotreme, and the monotreme putting out nerves and blood vessels into the herb's flesh. With the animal coordination, the plant can now afford to exapt the seeding mechanism to fire the thorns
Now this combined form would be a formidable foe, and could easily grow, trading bug for meat. If it became a hunter, it would be quite advantageous for the body and legs to adapt for speed, forming paws and erect hips. If the monotreme was weak in picking up scent and sound, this might force the creature to use its eyes to find prey. Its venom could also be used to hunt, like a snake. Also like a snake it could swallow its prey whole. With the ceradontes no longer useful, these structures could grow into monstrous triple-tusks for intimidation and display. Also, the lack of a need to tear meat may shrink the face, causing a fully human visage
This evolutionary history, with a few minor things like the long red hair and grey eyes, could have created a manticore
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So, once there was a war between the titans and the gods. In the end, the gods' leader, Anon, found a way to permanently remove the titans from the world, but the victory extracted a terrible price.
Titans and gods were fundamentally the same creatures, and the source of their power was also the same. Anon created a bunker that would use its inhabitants to connect to this power source and demonetize it.
As long as it was demonetized, both the gods and the titans would be weakened to the point where going into the mortal realms was not exactly possible. However, for the demonetization to keep the source in check, **every god had to stay in the bunker.**
The only way for them to interact with the mortal world is through the VR headsets that are connected to their massively weakened avatars there. Note though: **a god can only spend two days of the week there.**
Even for immortal beings, this confinement is a very long time. **Gods' psychology isn't different from humans'**, so I figured I should find an explanation why there's no chaos or societal breakdown in the bunker, even after hundreds of years.
I thought [LARPing](https://en.m.wikipedia.org/wiki/Live_action_role-playing_game) would be a good way, and in this situation, LARPing Hitler's last days on this mudball of a planet is the only reasonable choice.
They are roleplaying exaggerated and kid-friendly (except for the alcoholism, map fetish, and strong language) versions of the real people, usually with various quirks (Goebbels is constanly being compared to Skeletor, for instance).
My question is, **is this actually a viable strategy to keep people sane in a situation like this (being stuck in a small place with little to no contact with the outside world)?** If there are studies about this (like some kind of a Stanford prison experiment), I'd like to know about those as well.
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NASA (among others) have been/are active in studying isolation on human beings. We desperately need this data if we are to make a trip to Mars, as the journey alone will take as long as a normal tenure in the ISS. Then there's the problem of a small team being stuck on the planet for years, living in cramped quarters and breathing recycled air. This is very similar to what you're looking at with these deities.
[Here](https://www.nasa.gov/feature/conquering-the-challenge-of-isolation-in-space-nasa-s-human-research-program-director) [are](https://www.nasa.gov/feature/a-sirius-international-isolation-study) [several](https://en.wikipedia.org/wiki/Psychological_and_sociological_effects_of_spaceflight) [articles](https://www.apa.org/monitor/2018/06/mission-mars) on the subject of isolation with regards to space travel.
Long story short, your deities will need complementary (read: not necessarily compl**i**mentary) personalities to keep from killing each other after a few years. The studies found that long periods of isolation leads to stress, depression, messed up sleep cycles, and conflict. From the fourth link:
>
> ...the two crew members who had the highest rates of stress and exhaustion were involved in 85 percent of the perceived conflicts...
>
>
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Basically even one bad apple can spoil the bunch.
So how do you combat this? *Keep everyone busy*. By far the biggest problem is being idle with your thoughts in an isolated environment. Your deities need to be otherwise occupied.
Does LARPing Hitler's last days work? Sure, why not! It definitely gives everyone a purpose, unless they don't like their role (which is itself a potential story element). Would it turn them into actual Nazis? Maybe! Really the Stanford study is the only one of its kind to my knowledge, because it was so alarming as to shut down all further research using those methods. But it was pretty damning. You could easily argue that the characters would fall into their roles based on that.
Will they go insane doing this? Probably not. In fact I think they're more likely to go insane *without* it, or at least life would be miserable. Isolation does bad things to people, your deities are going to be damaged no matter what. But having a little VR time in the outside could definitely help keep them grounded. Part of the problem with the Stanford study was the *total immersion* the students were subjected to. Had they been able to go home on the weekends, maybe it would have been a lot different.
**Edit:** It's been pointed out in the comments that the Stanford prison experiment isn't necessarily a reliable source of information, because the people involved were being externally influenced to some extent. So take that data with a large grain of salt.
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### After reading the [help sections for asking questions](https://worldbuilding.stackexchange.com/help/on-topic), I am now confident that my question does in fact appear to be on-topic and in scope for this website.
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I currently use a page called [PlanetMaker](http://planetmaker.wthr.us/#) in order to render pictures of my planets and moons. However, this is web-based and can be somewhat difficult to use. It is also missing many things that I would like it to have.
# What is a good resource for rendering my planets and moons?
Like PlanetMaker, I want it to support the following mappings:
1. Texture maps
2. Normal maps
3. Bump maps
4. Specular maps
But it would be nice if it also supported:
5. Cloud maps
6. Ring maps
7. City light maps
8. Ambient/Emission light maps (for example, a partially lava world which glow in some sections)
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**A good answer will include links, or mention the name of a program or online resource that will enable me to visualize my planets and moons.**
I am willing to pay for a program, if need be, so all resources are welcome.
The best answer will be given to the first answer that actually answers the question properly.
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EDIT: The purpose is to simply have a realistic picture of my designs. I just want a good resource that will allow me to showcase the things I have created. Hopefully something not bulky such as Unity or Unreal Engine, since the only purpose of this is to make a reference image.
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First off I am not an expert in this field, however I do like exploring simulations of astronomy stuff as a hobby
In terms of simulating planets I would suggest , [Celestia](https://celestia.space/index.html) and [Space Engine](http://spaceengine.org/)
Now both of the above allow for some degree study of textures, however if you require a very detailed study I suggest using two or three tools separately instead of using just one (maybe one to study what type of conditions your planet might have in a simulation and then study different types of maps in separate tool to get detailed scenarios of what type of conditions you might get in such a in such a simulated planet, in smaller areas of the planet)
In terms of texture and stuff, I suggest [CrazyBump](https://www.crazybump.com/) (explore its tutorial [here](https://www.youtube.com/watch?v=bBQ9aEUKLX4) to see if this is what you want) and [ShaderMap](https://shadermap.com/home/) (tutorial [here](https://shadermap.com/docs/quick_start_introduction.html))
Since I could not figure out what exactly you want [I just got a vague idea of from your question] I have suggested the above.
I have also listed out both opens source soft wares Celestia , CrazyBump and ShaderMap [not every thing in this platform is free] and paid software Space Engine since you stated that either of the types would be OK
Hope this helps
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**Unity**
You could easily do this in Unity in under 20 minutes. Unity has a built in sphere mesh (though for a planet you'd technically want an ellipsoid), and tools for creating materials to map onto the sphere.
You will have to keep in mind though that there is *no* way to map a texture onto a sphere that doesn't result in distortion. It might make more sense to create a little tool in Unity to let you edit a sphere object directly, rather than starting from a 2D texture.
An excellent tutorial for what you want to do in Unity is [Sebastian Lague's Worldbuilding tutorial set on YouTube.](https://www.youtube.com/watch?v=wbpMiKiSKm8&list=PLFt_AvWsXl0eBW2EiBtl_sxmDtSgZBxB3) It is more geared towards procedural generation of worlds (i.e. more hands-off), and can be heavy on coding in some parts, but it will definitely provide the basics you need to map your materials onto a sphere, as well as rendering your planet.
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Without knowing how you're going to use the output, it's hard to say for certain. Unreal Engine 4 has a very robust texture mapping solution, it includes real-time ray tracing, and with the blueprint system, you could very easily get a render with the criteria you describe. It also has a python-based plugin that can reach into these features pretty well, so you could design a library very quickly that matches your needs. It also has a marketplace, which a cursory search yields things like "Planet Creator 1 V2" which may have a lot of the legwork done for you.
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Subarenaceous animals are those which can move long distances through dry sand - like sandfish lizards, or Dune's sandworms. The main problem they have to tackle is turning the sand immediately around them into a sort of fluid which they can move through.
Real subarenaceous animals do this by undulating, but I'm wondering - **would it be possible for an organism to produce (high-frequency, I'm assuming?) sound to do this?** The air vibrations would, according to this design, fluidize the sand. See <https://en.wikipedia.org/wiki/Fluidization> for more information on how this works.
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I think Explosive Liquefaction, and not Fluidization, is the effect you are looking for.
Soil Liquefaction or Explosive Liquefaction can occur when an intense pressure wave travels through the ground. It has been extensively studied by mining engineering and weapons designers. Generally, mining engineers want to avoid it, while weapons designers want to maximize it when attacking fortifications and buildings.
[](https://i.stack.imgur.com/fPxV3.png)
If your subarenaceous creature generated intense impulses by vibrating, croaking, clicking chitinous plates of its exoskeleton together and if that impulse was intimately coupled to the surrounding sand or soil, then they could swim forward or backward, displacing the momentarily liquified ground.
To fluidize the ground, they would need to inject gases into the soil all around their bodies, then they could move around until the gases diffused.
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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’m making a mostly ice planet with two moons. For the purposes of this question, let’s assume that they are both proportional size and distance to the size and distance to our moon. Both are tidally locked to the planet and the planet is in turn tidally locked to each moon, meaning that the whole system orbits the star locked in the same positions. As the title asks, what would the tides look like here?
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# Tides amplitude would be smaller than earth's
>
> Let me start by a definition. Tidal amplitude describes how big the
> difference between high and low tide is on a given day.
>
>
>
Tides are due mostly to two things: the moon and the sun.
## Let's start with the moon:
[](https://i.stack.imgur.com/jvAIV.png)
When the moon is at one point, gravitation laws makes that everything is slightly pulled towards it. As the water is a fluid, it moves a bit towards it, this is straightforward to understand. On the opposite side of the earth, the water also rises, this is not so trivial to understand and is well explained in [this question.](https://astronomy.stackexchange.com/questions/11882/what-causes-the-antipodal-bulge/11883) Basically, as the moon is very far away from the water on the other side of the earth, it's attracting it less, so the water rises.
In my picture, the high tide would be roughly in the middle of the Pacific and in the western coast of Africa.
## Now let's rotate the moon (or, rather, the earth)
[](https://i.stack.imgur.com/r3dCY.png)
Well, this is easy to follow, the high water follows the moon. If you stay at one point close to water, you will see it rise and recess (twice a day) as the upper water us followed by lower water, and then by higher water again, and so on.
Now, in the illustration, high tide would be roughly in India and in Mexico.
In this sunless system, the amplitude would always be the same between high and low tide.
## Let's add the sun
[](https://i.stack.imgur.com/5aJfb.png)
The sun is much bigger, but further away than the moon. The equation for the gravity is this:
$F=G\frac{m1m2}{d^2}$
With m1 and m2 the mass of each planet/star/moon and d the distance between their gravity centre. If you do the math, you will find that the the sun force is bigger on earth than the moon's.
**But**, because it's further away, the difference of it's effect between the side of the earth facing it and the other side is much smaller. Detailed explanation [here](http://hyperphysics.phy-astr.gsu.edu/hbase/tide.html). If you do the math (which are getting complicated), you will now find that the sun is having 46% of the influence of the moon on tides. About half of it.
So, in my picture above, you can see that the sun has an effect, but not as important as the moon's. This picture represents when the tides have the lowest amplitude, because forces of both celestial bodies are trying to neutralize each other.
### Sun and moon opposite
[](https://i.stack.imgur.com/rLiRY.png)
If you put the sun and the moon on the same axis (either opposite as in the image, or on the same side of the earth), their forces adds up and the tide has the biggest amplitude.
## Now, your case
You have two moons, opposite to each other:
[](https://i.stack.imgur.com/fkbDP.png)
The water is pulled twice as much as on earth towards space below the moons.
**But** your moons and your planet are tidally locked, so the water is always high at the same place, and always low at the same place. In other words, at a given beach, the water is always at the same height. Hence there is no tide due to the moons.
## Enter the local star
I understand that your planet is not tidally locked to its star. So:
[](https://i.stack.imgur.com/pGmUx.png)
The sun will create a tide, just like on earth. Assuming the same star size and distance as on earth, the amplitude would be much smaller (roughly about a quarter of what's on earth). This is because the sun is the only object inducing a tide, and it's influence is reduced in comparison to earth, because the sum of the moons' masses is heavier.
### Side notes
There are some other factors influencing the tides, as noted in comments to your questions, such as
* The geography of the coasts and ocean bottoms
* The winds
* Currents
But, this is not really relevant for the question, as you are only asking us about the moons, and give no info about these points. My answer assume that their are similar to what's on earth.
Also, all of the above is a **very simplified** version of reality. Tides also behave according to, for instance, [Laplace dynamic theory](https://physics.stackexchange.com/a/121858).
# Ice
If your planet is an icy one, there are two possibilities. Either it is iced to the bottom (not much water left). Then probably no visible tide at all. (Pro-tip: choose this option and just forget about all the above, not tide, that's it, easy).
Or it is just a cap of ice above water, in which case it will [rise and fall with the water](https://www.nasa.gov/feature/goddard/2016/nasa-tracking-the-influence-of-tides-on-ice-shelves-in-antarctica), or break into icebergs. And all of the above applies.
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For your consideration, a star system inside a [dark nebula](https://en.wikipedia.org/wiki/Dark_nebula) with a potentially habitable planet. Being a dark nebula, we Earthers can't see light shining behind the nebula. Further and therefore:
* The nebula is large enough that the potential inhabitants won't see any stars in any direction. [This previous question](https://worldbuilding.stackexchange.com/questions/4875/what-would-skies-look-like-on-worlds-inside-nebulae/4879#4879) appears to discuss "normal" nebula and I'm not enough of an astronomer to know whether this is an absolute for dark nebula. But I'm assuming if we can't see through it, it's potentially large enough that no one at the center could, either.
* The gravity of the sun would, I believe, draw the surrounding nebulous cloud into itself... which would suggest that it would draw the material inside the orbital planes of the planets.
* It is therefore my assumption that as the planets orbit, surrounding material is constantly pulled into the atmospheres where I believe it would incinerate. The leading point of atmosphere would be aglow with burning debris that may even pass around the atmosphere and leave a bit of a thermoluminescent trail behind the planet. Dust consisting of mostly Carbon would be constantly falling.
**But...**
**Could such a planet have a thick enough atmosphere and a strong enough magnetosphere to block enough of the nebular material from falling and allow for an inhabitable 70% water planet?**
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Definitely. First, the nebular material must get into the solar system. (It certainly couldn't be there to begin with - when a star forms, it eats a hole in the nebula. So, this system had to have moved into a nebula later.) A system like our own, outside a nebula, has something called the heliosphere, which is where the star's solar wind dominates.
The effect of the solar wind and radiation pressure means that this dust will not be able to simply fall down into the planet's atmosphere. And it's usually the charged, high-energy particles from the solar wind that are the problem with regards to holding in atmosphere.
The dust itself will have some effect on the planet, not sure what, because of the way dust interacts with the weather (in complex ways I'm not going to even pretend to understand.) (and this leads further into effects on life.)
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Newly formed stars tend to expel the nebula around them, if the nebula is dense enough for there to be an accretion disk in spite of the solar wind the planets in the system will have decaying orbits due to "friction" with the accretion disk (the dense planets are orbiting much faster than the disperse gas/dust so ploughing through this medium will slow the planet down) and their increasing mass (more mass + same inertia = less velocity).
I don't think they'll remain in orbit long enough for life to evolve however they may be habitable for a cosmologically short period of time, although my timeframe estimates are pure speculation since I don't have the means to computationally model any of this.
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Prompted by a question about the impact of dietary iron in elves ([How would Fair Folk-type elves deal with dietary iron?](https://worldbuilding.stackexchange.com/questions/91328/how-would-fair-folk-type-elves-deal-with-dietary-iron)), I wondered whether haemocyanin could be an alternative to haemoglobin in creatures (for example elves, who have a weakness to iron - although probably not haemoglobin).
Although - as far as I know - only some arachnids, arthropods, and molluscs have haemocyanin, I'm making the initial assumption that it is in fact *possible* for human-sized beings to have copper-based blood. With that in mind, **what sort of impacts (positive or negative) would this blood chemistry have** on humanoids?
*My thoughts so far:*
1. Haemocyanin is second only to haemoglobin in frequency as an oxygen transport molecule. Is it any more/less **effective**? If it is *less* effective, would that result in these creatures living at lower altitudes with greater atmospheric oxygen?
2. The obvious colour difference: deoxygenated blood is clear, and oxygenated blood is blue.
3. Diseases like anaemia would probably have parallels - could this be treated easily with supplementary dietary copper (in mild cases)?
4. Cross-breeding with humans would become difficult, I expect - half-elves wouldn't exist, and heterozygosity could be compromised.
**EDIT**
I'm not too bothered about *why* they might have copper-based blood, but more about the implications if they *do* have it. Thank you for pointing out that haemoglobin wouldn't actually be toxic/harmful to an elf - it's not exactly iron filings floating around in the bloodstream. ;)
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It would probably effect the daily level or iron and copper needs for health.
according to <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3690345/>
Recommended daily allowance (?) of Iron is 18 mg while that of copper is 0.9 mg.
Just a guess but creatures with copper based blood would probably need to eat more copper "rich" foods and less iron "rich" ones.
adding a bit.
The cycle of iron as a nutrient in the environment is well studied (<https://www.nature.com/scitable/knowledge/library/earth-s-ferrous-wheel-15180940>) as well as the storage and use of iron in the body of mammals (<http://www.chemistry.wustl.edu/~edudev/LabTutorials/Ferritin/Ferritin.html>). Iron cycling out of the body is even what gives poop it's brown color. Copper as a nutrient is less well understood (just above <http://ajcn.nutrition.org/content/88/3/826S.full#sec-4>).
If there is a species that needs a lot of copper in their diet there is probably a whole ecosystem of plant and maybe animals the provide a good source of copper. So this species would need to hunt or cultivate these. For Iron based species to eat these plant in the same quantities would probably be toxic. So now your have potentially two species that cannot really share food. There could be extra complexities in trying to have sets of agriculture in the same place and this could drive them to different regions.
If there were not a whole ecosystem based on getting enough copper then the species may have to work extra hard to cultivate or hunt food that gave them enough copper. Again perhaps restricting population centres geographically and perhaps limiting the size of those population centres.
Hopefully a better answer
Bonus note:
Hemocyanin ref:
<https://en.wikipedia.org/wiki/Hemocyanin>
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The human body does need some copper, but we are talking very small amounts. Chronic ingestion of large amounts of copper can cause a range a organ damage/death. The first to be impacted would be the liver as normally when you ingest extra copper it filters and then releases it into pile in the gull bladder where you eventually poop it out (so the gall bladder would also be one of the first organs to be effected).
Copper also has strong anti-microbial effects, and I would speculate this would cause all kinds of havoc with your natural microbes in your digestion system which would cause severe diarrhoea. There is a genetic disorder known as Wilson's disease, those who suffer from it are unable to process and expel copper. Symptoms can include itching, muscle cramps, psychosis, organ failure... though it does come with kind of a cool symptom called Kayser-Fleischer rings, copper rings that form around either the iris or pupil.
There are some benefits to using hemocyanin over haemoglobin, but not many. Hemolymph, which is what hemocyanin is usually found in, has some natural antimicrobial properties because of the copper, though to what degree and how effective this can be is not fully understood. Another is that metabolic cost for hemolymph and hemocyanin is much lower, as hemocyanin isn't a cell but just a protein, unlike red blood cells which make the protein haemoglobin.
The life span of red blood cells is 3-4 months which means your body is constantly making new red blood cells to replace the dying ones, every 4 months you have a new set of cells. This is not the case for hemocyanin as it's protein structure can remain stable for years. Generally, haemoglobin is about 4 times as efficient as hemocyanin for transporting oxygen, except in very cold environments with low oxygen pressure such as low depths in the arctic ocean.
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Due to high viscosity and the fact that all creatures with haemocyanin have it loose in the blood not in blood cells the concentration must be kept low. Maybe elves have haemocyanin blood cells to solve the problem. I've read that haemocyanin from horseshoe crabs is more efficient and nears the efficiency of haemoglobin. Something about cooperative binding versus non-cooperative binding of oxygen. The advantages of haemocyanin are an ability to function at lower temperatures and lower oxygen concentrations. You will note that Star Trek's blue skinned Andorians come from an icy world. For elves it would aid survival in deep, cold, and oxygen poor caverns. On another note haemocyanin would be an ideal for a race of deep water mermaids for the same reasons.
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### Situation:
* a large terrestrial planet (a 'super earth', around 9 earth masses with a surface gravity roughly double earth's) with a mostly hydrogen atmosphere and ammonia oceans (pressure is high enough that ammonia is liquid up to around 50°C)
* life uses ammonia as a solvent
* plants convert methane to biomass and release hydrogen (and animals obviously inhale hydrogen and exhale methane)
**Question: Is it plausible for (the carbon based) life to use biogenic silica (= hydrated silica, SiO$\_2$.$n$H$\_2$O) as a structural material?**
Ignore strength issues please ([According to this research paper](http://www.pnas.org/content/113/8/2017.full.pdf), silica is significantly stronger and less dense than bone, so that should not be an issue) - I'm interested in the **chemistry** of the situation.
As a terrestrial planet, water and CO$\_2$ will be released by volcanic outgassing, and they have to go somewhere. **Is it plausible that SiO$\_2$ dissolves in the ammonia rivers/seas to be taken up by plants and animals, which then form hydrated silica?**
I'm unsure about how oxides would behave/exist in a reducing atmosphere.
**EDIT**: (More details to make the question more specific)
On earth, silica forms (as quartz) from magma in volcanic rocks. That should be similar on this planet too. On earth it dissolves in water by hydration to form silicic acid, which is absorbed by the diatoms and other creatures which use silica as a structural material. On this planet, the seas are ammonia, not water.
That seems to leave two questions:
* Can silica dissolve in ammonia?
[The abstract of this paper](http://www.sciencedirect.com/science/article/pii/S0009261401011927) says that it forms a SiO$\_2$-NH$\_3$ complex when exposed to gaseous ammonia and then dissociates to the molecule H$\_2$NSiOOH under the influence of (UV to visible) light.
Would this (or something else) work on the planet in question as a source of silica in the ammonia seas?
Edit: (thanks to Kingledion) the full paper says that both reactions are exothermic, and that the formation of the initial complex has negligible activation energy. (*Edit edit: I intended that edit to be a "**yes**, it would work" answer to the question*)
* Can the organisms hydrate the silica internally?
We produce ammonia and (a massive number) of other things as biochemical reaction intermediates and products - is it implausible that organisms on this planet can do the the same with water to produce biogenic hydrated silica?
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My own answer to the question:
Water from volcanic outgassing and biological waste will dissolve in the ammonia seas - much as CO$\_2$ dissolves in the seas on earth. [This paper](https://www.researchgate.net/profile/Mingfei_Zhou/publication/244133376_Reactions_of_silicon_dioxide_with_ammonia_molecules_Formation_and_characterization_of_the_SiO2-NH3_complex_and_the_H2NSiOOH_molecule/links/5741b77508ae9ace84186d29.pdf) says that silica dissolves easily in ammonia, so we can assume that silica will also be available in the rivers and oceans, as it is on earth.
In analogy to earth's [carbon cycle](https://en.wikipedia.org/wiki/Carbon_cycle), I suggest a water cycle - plankton-like microorganisms absorb dissolved water and silica to form hydrated silica which they use to form their shells/skeletons (similar to earth's [diatoms](https://en.wikipedia.org/wiki/Diatom)). This de-acidifies the oceans (in ammonia, water behaves as an acid). These are eaten - passing silica into the food chain - or sink to the bottom of the sea, returning silica and water to the crust as sedimentary rocks.
The use of silica as a structural material in these ancestral early organisms provides the basis for its use in higher organisms. [Being stronger and less dense](http://www.pnas.org/content/113/8/2017.full.pdf) than bone and comparing favorably to other structural materials, evolution did not find an alternative (silica was 'good enough').
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"The paper says that both reactions are exothermic, and that the formation of the initial complex has negligible activation energy." This answers your first question with a resounding yes.
On to the second: We produce ammonia and (a massive number) of other things as biochemical reaction intermediates and products - is it implausible that organisms on this planet can do the the same with water to produce biogenic hydrated silica?
Given water and the necessary components, no it isn't implausible, as life on earth has developed the mechanisms to produce a stunning array of compounds, and the necessary reactions don't take much catalysis to get going. The difficulties will be getting rid of waste products, but humans produce many waste products and have systems to deal with them without much fuss, so this shouldn't be a limiting factor.
My main concern is that you said we are dealing with a planet "with a mostly hydrogen atmosphere and ammonia oceans", where "life uses ammonia as a solvent". You did mention that water is released by volcanic outgassing, but is that in sufficient quantities to satisfy the requirements for hydrating silica for use in organic structures? If not, it's not worth it for life to develop that mechanism. If so, how does this water collect, and once collected, how is it gathered by the lifeforms being considered? If these questions are answerable, then it's plausible that organisms on your planet can and would produce biogenic hydrated silica.
I hope this helps!
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In water and CO2 the oxygen is already bound to other atomic species. Unless you have some mechanism to massively release the oxygen from those oxides (atmospheric electric discharge may dissociate water, but not sure how long the free oxygen would last before recombining with the hydrogen or other species), you are not going to have that much SiO2.
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I am designing a mammal living in a warm environment (like a warm desert) which has developed a switchable metabolism, so that during the day it is cold blooded and during the night (when it is colder) it goes on warm blood mode.
This switching roughly halves its energy demand (half of a day it doesn't need to warm itself up, heat is provided by the environment) and gives it an advantage in an environment with scarce resources.
Would this be possible, or do I need to make some other assumptions?
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Why not? Some lizards have ways of warming themselves from within *when necessary*. This can evolve into something more like what warm-blooded animals use rather than cruder mechanisms, but still keep the overall cold-blooded details so it doesn’t *require* the furnace to be on all the time.
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It should be possible. Leather-back turtles are capable of being endothermic at will, as a function of activity and quantities of brown adipose tissue (very common in mammals, not so common in other animals).
Us mammals and birds OTH, we are endothermic but retain a high metabolic rate *at rest*. So in essence, those cute and big bad leathery boys of cold seas can flip a switch and go endothermic.
Bluefin tuna is also capable of being endothermic according to its needs. It has specialized "red" muscles at its core that allows it to regulate its temperature even when experiencing temperature swings that would stop a human heart.
I could see a mammalian-like being able to switch to a cold-blooded/ectotherm modus operandi when there's excess ambient heat.
Many mammals in Madagascar have developed the ability to go into torpor during the hottest days of summer. So it wouldn't be impossible to think a mammalian-like being being able to do that on command as well.
I don't think we see mammals having this ability to go ectotherm because the Earth has never given mammals regular drastic temperature challenges on a daily basis.
Imagine an Earth-like world with, say, a 72 hour day/night cycle causing many regions to go experience a 90F (32C) temperature swing from midnight to midday.
If the night extreme is in the freezing, but midday temperatures are what we consider "normal", probably mammal-like beings (and other beings for that matter) would develop the ability to hibernate on demand or have "anti-freeze" agents in its fluids. Some crickets in New Zealand allow themselves to be frozen at night.
OTH, if it is the midday temperatures that are extreme (extreme from our POV), then animals would/could develop on-demand ectotherm behavior (or go into a state of torpor.)
I think your hypothetical being to be quite possible.
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What you're describing seems a lot like **torpor**, which is a sort of middle ground between sleep and hibernation. There are plenty of animals which do that including mice, bats, and birds. <https://en.wikipedia.org/wiki/Torpor>
This article also explains the difference between sleep, torpor and hibernation:
<https://www.sciencenewsforstudents.org/article/explainer-how-brief-can-hibernation-be>
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> "True hibernators might drop their metabolism by 94 percent or more.
> In contrast, Geiser notes, animals that experience daily torpor drop
> theirs by only some 65 percent."
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You could have a creature that is solar powered. During the day, it uses sunlight to create and store chemical energy, which it then uses at night.
During the day, you could have it just continue to use the same chemical process, or somehow directly use the sunlight for energy.
This is incredibly similar to something you may have had for breakfast today. Basically, it's photosynthesis.
Granted, it's not a switchable thermal cycle, but it serves the purpose, in my opinion.
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For a story I am writing, I need a planet covered in a shallow ocean. What I mean is that I want the majority of the planet's surface (=> 60%) to be in the photic zone of the ocean.
This planet must sustain life, with the most intelligent being some smalamanders. Ideally this planet can remain habitable until my smalamanders evolve into smalamen, but I am not opposed to benevolent aliens changing the conditions to be more suited to life. (And if necessary, the topography of the planet.)
What kind of environmental or planetary factors could achieve this?
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Were the Earth purely sperical with no mountains and valleys, a 2.7 km deep ocean would cover it all.
However, Earth is not a smooth sphere. While admittedly nowhere near 60%, I would say that a reasonably large part of Earth's ocean lies in the photic zone, except in those unusual times when Earth has ice sheets at the poles.
Normally (with a very imprecise meaning of "normally") Earth [does not have permanent ice](https://en.wikipedia.org/wiki/Ice_age#Major_ice_ages); periods with permanent ice at the poles are somewhat rare and somwhat short (on the geological scale, that is). When there is no ice at the poles the seas are much higher than in our [present ice age](https://en.wikipedia.org/wiki/Quaternary_glaciation) and cover a lot of low-lying land.
North America and Central Europe were covered with shallow seas for quite a long time:
* The [Western Interior Seaway](https://en.wikipedia.org/wiki/Western_Interior_Seaway) which, from the Cretacic to the Paleogene, used to separate North America into Laramidia to the west and Appalachia to the east. *"The Western Interior Seaway was a shallow sea, filled with abundant marine life."* (Wikipedia)
* The [Paratethys Sea](https://en.wikipedia.org/wiki/Paratethys) *"was a large shallow sea that stretched from the region north of the Alps over Central Europe to the Aral Sea in Central Asia"* from the [Jurassic](https://en.wikipedia.org/wiki/Jurassic) to the [Pliocene](https://en.wikipedia.org/wiki/Pliocene). *"Today's Black Sea, Caspian Sea, Aral Sea, Lake Urmia and others are remnants of the Paratethys Sea."* (Wikipedia)
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> At various times during the Mesozoic, shallow seas invaded continental interiors and then drained away. During Middle [Triassic](https://en.wikipedia.org/wiki/Triassic) time, a marine incursion -- the Muschelkalk Sea -- covered the continental interior of Europe. Seas again transgressed upon the continents between the Early and Late [Jurassic](https://en.wikipedia.org/wiki/Jurassic) and in the early Cretaceous, leaving extensive beds of sandstone, ironstone, clays, and limestone. A last major transgression of marine waters flooded large sediments later in the [Cretaceous](https://en.wikipedia.org/wiki/Cretaceous). Those sharp rises in sea level and resultant worldwide flooding are thought to have had two causes. The first was warm global temperatures, which prevented large volumes of water from being sequestered on land in the form of ice sheets. The second was related to accelerated seafloor spreading; the attendant enlargement of ocean ridges displaced enormous amounts of ocean water onto the landmasses. Marine transgression was so extensive that in North America, for example, a seaway spread all the way from the Arctic to the Gulf of Mexico in the Cretaceous Period.
>
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> John P. Rafferty, *[The Mesozoic Era: Age of Dinosaurs](https://books.google.ro/books?id=AxXJ3TqLNZUC&pg=PA25)*, The Rosen Publishing Group, 2010 (link goes to Google Books)
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Remeber that the Cretaceous is so named after *"the extensive beds of chalk (calcium carbonate deposited by the shells of marine invertebrates, principally coccoliths), found in the upper Cretaceous of western Europe"* ([Wikipedia](https://en.wikipedia.org/wiki/Cretaceous#Research_history)).
Even during more recent times large parts of western Siberia were covered with shallow seas:
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> The seaway extended from North Pakistan and India to North Siberia through a system of inland seas and straits. [...] During the [Bartonian](https://en.wikipedia.org/wiki/Bartonian) and Priabonian the West Siberian inland sea was isolated completely from the Arctic Basin during the last phase of marine sedimentation. It was connected to the Turan sea through the Turgai strait.
>
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> Mikhail A. Akhmetiev, Nina I. Zaporozhets et al., "[The paleogene history of the Western Siberian Seaway](http://www.univie.ac.at/ajes/archive/volume_105_1/akhmetiev_et_al_ajes_v105_1.pdf)", Austrian Journal of Earth Sciences, vol. 105/1, 2012.
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Conclusion: Just imagine that the sea is [60 meters above present levels](http://geology.com/sea-level-rise/): a significantly large part of low-lying continental land will be covered with water, including a large-ish inland sea in Australia and a greatly expanded Caspian linked to the ocean through the Manych strait and the Black Sea.
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The principle challenge here is that we get our oceans from our volcanic activity which is also responsible for the plate tectonics that give us our high mountains and low oceans. In theory, the earlier in an Earth like world's development you are, the flatter it will be and the shallower it's oceans. But, this makes being around long enough for intelligent life to evolve difficult, another option might be a smaller planet like mars. It will lose it's volcanic activity earlier in its life cycle making it remain flatter while also putting out an ocean much more slowly, but then there is the significant risk of what happens to the atmosphere when the core cools down, because then you might end up with... well, Mars. I'm not really sure what solution would work better, but in either case, you are looking at a race against time.
If your story allows for it, it might make the most since if your intelligent species actually came from another world in their forgotten past. That would make the evolutionary timeline less restrictive.
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If you literally mean that 60% of the surface is in the photic zone, then you already have an example of earth. The photic zone is the first 80m of water, so any water that has any depth will immediately be in the photic zone.
If you mean that 60% of the planetary surface is 0-80 meters below sea level (i.e., 60% of the surface is only in the photic zone), then you might have to watch out for the temperature and CO2 Levels. The deep ocean is currently the biggest repository of CO2 in the world, stored at the very bottom where it's trapped by pressure and being really cold. You could make the rest of your ocean deeper to compensate, or you could have more efficient photosynthesis in your plants, or any number of factors. The oceans also act as a heat sink, but any body of water large enough, regardless of depth, should do the trick.
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The traditional description of the mermaid is half-girl and half-fish. That, both biologically and dramatically, is just ridiculous. If the mermaid were half-fish, then why does she move her tail up and down and not side-to-side as fish should? No, my first proposal is to make the mer (the whole race, not just the females), half human and half dolphin (or porpoise).
Now the first issue to address is hair. In classic literature, the girl half of the mermaid has long, flowing hair. Not only is this too clear-cut, which is biologically impossible, but it would create way too much drag. So my proposal is this--either make the mer short-haired (think "pixie cuts") or all-out bald. Either choice would reduce drag substantially.
As for the face itself, my original proposal is to reduce the nose into flat nostril slits, since smell is of no use to an air-breathing mammal that spends its entire life underwater. But my proposal to keep the human face is way more interesting, and here's how--[How to Breathe Both on Land and Under the SEA](https://worldbuilding.stackexchange.com/questions/44137/how-to-breathe-both-on-land-and-under-the-sea)
Of course, the proposal for tetrachromacy (having four color receptors) is valid here, too. Also, if one wants to tackle the Amazonian legend of the Boto, we'd might as well give the mers the tapetum lucidum, a layer of tissue behind the retina that reflects light, increasing the availability to photoreceptors, though at the risk of losing detail. (However, tetrachromacy might be a way around this problem.)
How would a mer vocalize to attract a mate--be it mer or human? Would it echolocate using the melon, as cetaceans do? Or maybe something less front-heavy--an enlarged vocal sac, just like frogs or gibbons?
The final issue to address is coloring. Unlike the centaur, the mer's transition between two species is smooth and natural, but they are still colored separately. My proposal is to give both halves one color scheme, based on the following cetaceans:
* Orca
* Atlantic Spotted Dolphin
* Pacific White-Side Dolphin
* Bottlenose Dolphin
* False Killer Whale
Are any of my proposals listed above sound, or have I created some unintentional side effects to the mer body?
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## And your question is...
I'm not quite sure what the exact thrust of your intended question is. It seems to be about how to go about making the concept of a merfolk more realistic? And also if your existing suggestions are realistic?
Assuming that is the case:
## Point one: Tail movement
It will be noticed that, most, if not all ocean mammals move their tails up and down, not side to side, while non-mammalian fishes again most, if not all, move their tails side to side. As such, it only makes biological sense for a mer to move their tail up and down, as they are (being half "human") presumably mammalian.
It is indeed odd that mer tend to be called out specifically as "half-fish". Perhaps this notation stems from taxonomically ignorant origins, people who in their time and era called anything and everything that swam in the ocean a "fish" and were not aware of the differences between mammalian and non-mammalian ocean creatures. (Not to mention that mythology does not always make sense, even if there was awareness of the differences back then.) As such, there should be no issues with, and indeed should likely be more genetically possible to have mer be half-human and half-mammalian ocean creature instead.
## Point two: Hair
Hair is ascetically pleasing to a human, but seems rather unnecessary in an amphibian or purely water-breathing species. As pointed out, it would produce drag, and seemingly serves no other purpose than the ascetic.
Here, the origin would become critical. If the mer are augmented or altered creatures using humans as a base, and if the initial tweaking did not remove the hair, then the mer would still have hair from their human heritage, useless as it may be.
It would seem quite the disadvantage to have hair underwater, unless it was replaced with some sort of sensory boosting appendages that superficially resemble hair and are less drag-producing that traditional hair. Of course, if they are amphibious, and not purely water breathers, then perhaps the hair would be left in place for their above-water times. The above-suggested short-length hair would seems a more viable option in such cases. Another option is to replace the hair with an analogue, fins or some other mechanism for display or ascetics.
Given the mythical stories and origins of the mer: namely, that they were a species that hunted men specifically, luring them to death and/or doom, it actually makes sense for them to have hair for those purposes, noting again that hair is considered attractive to humans.
For a realistic and viable race of mer, with both male and female, and assuming that they don't need to hunt human males for some reason (such as an all female race or something) then it would make more sense for them to not have hair - barring the above mentioned [possibility of sensory appendages. Another slightly more far fetched justification for hair would be harvesting and using hair as a tool - weaving it into water resistant fabrics and ropes. Given that forging is going to be problematic underwater, tool development and usage will be somewhat more challenging.
## Point Three: Nose
This will again depend upon amphibious versus pure water-breathing. In either case (and I was going to suggest chest-gills myself, but I see that it was covered in the question referenced) the nose would likely be streamlined and on the small end of the spectrum for the amphibious mer, if not flattened or removed entirely for a pure water-breathing mer.
Given the comments about oxygenation, it would seem the amphibious version would have more potential realism.
## Point Four: Senses - Visual and Auditory
Visual adaptations for low light would seem critical given that so much of the ocean is little to no light whatsoever. Also, a nictitating membrane would seem critical for eye protection (given the amount of debris floating around).
However, more of the ocean is dark than lit. Fortunately, human echolocation is a real thing, with the more extremely talented examples being able to walk or bike around town, skateboard, even playing video games(!) solely using echolocation. (Ben Underwood and Daniel Kish are a couple of the more famous examples.) For an ocean-going (amphibious or not) creature, it would seem that honing and developing this ability would become critical for navigation and creature recognition, and perhaps some more robust vocal cords might be in order.
I imagine that singing, above or below water, could become the mate attraction of choice. Recall also the possible hair analogue suggested previously for display purposes.
## Point Five: Coloration and Skin
Depending on the target dwelling and intended travel regions and areas, the skin becomes quite important. A shallows dwelling creature will have different composition to the skin than a more widely-ranging ocean-going type, notably, the fatty tissues directly underneath the skin.
An ocean-going type mer would need to be able to withstand the cold and potentially the crushing depths of the oceans, needing a much thicker layer of blubber, and some other internal structural differences for long / deep cruising. Especially the deep dives.
Having a coloration and body shape that can blend in with or mimic other creatures would be a potential advantage in cohabiting and/or cooperating with native ocean creatures, as well as times when hiding amongst the crowd has benefit. On the other hand, it could also get them mistaken for valid prey by certain creatures.
A chromatophoric integument would have certain advantages as well. Not only could mer pull off the above mentioned tactics, they could also hide against objects and the sea bottom. In areas with light, it could also serve as a non-auditory form of communication. Combine with the optional ability to fluoresce, and you have signalling capabilities even in the depths. (And a possible method to lure prey (or mates) to themselves!)
Finally, in a natural or survivability-designed mer race, streamlined skin would be the ideal and most advantageous, as such while the chest cavity would likely be rather large (see oxygenation comment above), female mer would tend towards (*ahem*) smaller mammalian organs. Anything else would produce considerable drag during water maneuvers. I will decline to comment on mer designed for purposes other than survival.
## In Conclusion...
Most of the comments and suggestions made in the original question seem to on the whole support the survival and prosperity of an amphibious race of mer. I hope my additions are helpful.
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Hair:
* pixie cuts for females if you like [these](https://www.google.com/search?q=pixie%20cut), buzz cut for women if you liked Segourney Weaver in [Aliens](https://images.eurogamer.net/2014/usgamer/aliens-spot8.jpg) or Demi Moore in [G.I. Jane](http://psimovie.com/images/gi.-jane/scr-7.jpg)
* for men it could short or buzzed or bald or even long if they don't want a dagum hair cut and don't care about the drag, suppose the same could be true for females as well
* dolphins are actually born with whiskers, I didn't know that before I just looked it up, apparently [*all mammals have hair*](http://www.dolphinconnection.com/dolphin_fact_sheet)
Eyes:
Not to step too far forward, but if I were to have a romance with a mermaid, language would certainly help. However, if she could see in the dark, could notice my vulnerability and helplessness in a very low light setting, that would make me depend on her more in those situations and, particularly, it would reveal a part of me to her. This could serve to strengthen the relationship and it could also serve to create tension upon first meeting her. And I wouldn't mind the glowing eyes. That would actually lend a more wild aspect to her, making her seem more exotic to me than she already is.
Not sure if it matters whether she can see colors, but as you say, if it helps her to see higher resolution, and therefor greater distance out of water, then it is perhaps for the better from a purely evolutionary standpoint, i.e. spoting trouble from a distance, remaining undetected etc. However, and I'm getting gushy here, but I want my mermaid to be bad-ass, top-notch and well equipt in all aspects of survival and ready to fight and not just run away at the first sign of danger. Seeing well is also a predatory advantage, spotting seals on the rocks for example before they can see what is approaching.
Vocalization:
Well, as I mentioned above, language helps with human interaction and a human like voice is obviously preferable to that end, but it isn't strictly necessary - nor are vocal chords. For example in Jean Auel's Clan of the Cave Bear, the Neadertals are described as having vocal chords, but they are less well formed for speaking and the faces have less expressive features and as a result the communications with voice and lips are mostly grunts, whoops and simple sounds, but the language of the Neandertal in the book is a very rich and nuanced sign language which involves the whole body, not jus the hands. This sign language comes in a colloquial dialect as well as a formal/inter-regional dialect. If you go without smooth tones for the voice then perhaps a rolling burble or intricate sort of purring like muscular contraction like the sound that frogs make but less projected for close or quiet conversations, otherwise belting, screeching groans when a high volume is required - for example like the [mating sound of the Southern toad](https://youtu.be/kwECjnPBOtw?t=212) or this [cicada call](https://www.youtube.com/watch?v=mah26og11ms), but overall perhaps with a more variable/deeper tone. I don't know that squawking, clicking and chirping is as personable as something more like burbling would be, something in between the [lion rumbling](https://www.youtube.com/watch?v=gWR5RysR_bE) and the [aligator growling](https://youtu.be/xneiSfKk0Lo?t=16) - but I suppose that as well is a matter of taste.
Coloring:
Anything from gray to white to cream-colored to brown or black I would think is fine. I'm assuming you're not after the blues and greens of peacock feathers. They could be different colors like animals and people - what a concept! I personally wouldn't make them too distinctly marked other than overall tone because I want to get to know them personally to understand their individual differences, but there is nothing preventing any choice you make in that regard. Natrually speaking they would probably be predators/hunters so they would need camouflage to hide and ambush or they would need eyesight and speed to rush. But they could in theory also graze on kelp forests. Maybe they have no natrual predators and are smart enough to capture or kill any kind of prey they wish so would have less need for camouflage. If they are smart they could make their own camouflage if need be.
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On Earth, the vast majority of the biosphere is ultimately dependent on a large number of autotrophic organisms that produce usable energy in the form of glucose by using photosynthesis. However, on worlds with thick, dense atmospheres or covered in massive sheets of ice, sunlight may not be available to life forms living on either the surface or in ice-covered oceans.
Life, of course, does not need a base of photosynthetic organisms to exist. Chemotrophic life evolved before phototrophs did, and is perfectly capable of living in the most barren and inhospitable environments we've found, like the [insides of rocks deep beneath the surface of the Earth.](https://en.wikipedia.org/wiki/Lithotroph) Non-chemotrophic autotrophs do, however, enable a biosphere to expand beyond what can survive on what may be a limited amount of available oxidizable nutrients.
Are there any alternate means by which autotrophic life could harvest energy? In an otherwise habitable world without sunlight, is there an alternate way in which non-chemotrophic autotrophs could evolve?
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To answer this question I think it is most useful to look at how life as we know it utilizes energy and go from there. This is of course isn’t going to cover all conceivable forms of energy capture but we’ll try to get pretty creative anyways.
To begin with, organisms are composed of chemical energy. By chemical energy we mean the energy stored in the form of atomic arrangements, chemical bonds that contain energy essentially. From the DNA, the RNA, the proteins, the membranes, all of it was formed by chemical energy and runs on chemical energy. It’s pretty hard to imagine life as we know it that doesn’t involve chemical energy of some sort since that is basically just our definition of life, something animated and composed of chemicals. Chemical energy makes for great lifeforms because it’s a way of storing energy stably over long periods of time, and of course it’s easy for chemical energy to be utilized to catalyze chemical reactions.
So, for an autotroph to exist it needs to be able to convert energy into chemical energy. And that’s really our only requirement. Any energy source that an organism can use to generate chemical energy can potentially be used to create and sustain life. Of course, we know that theoretically all sources of energy are interchangeable and could in some way be converted to chemical energy. That conversion may not be particularly efficient or simple, but life really doesn’t need much to get by.
While I think the answer “all possible forms of energy can be used to feed autotrophs” is technically correct we can expand on our answer with more specifics by looking at how chemical energy is generated by life as we know it.
In photosynthesis, light is converted into chemical energy. Fortunately for us it’s something of a roundabout process. Specifically I’m referring to the generation of an electrochemical gradient and its use by a protein complex called ATP synthase. The light energy captured by chlorophyll isn’t all transferred directly into chemical energy, some of it is used to create a proton gradient across a membrane which ATP synthase, a protein that spans that membrane utilizes to create a very useful molecule called ATP. ATP is one of the primary ways in which chemical energy is stored and expended in a cell. What this means for us is that we know that organisms don’t need to convert energy directly into chemical energy, but could instead create an electrical or chemical gradient to then convert into chemical energy. What is particularly interesting about the function of ATP synthase though is that it also converts the energy from the electrochemical gradient into an intermediate form before it becomes chemical energy. That intermediate form is kinetic energy! ATP synthase actually uses the electrochemical gradient to spin a piece of itself sort of like a turbine and it is this movement that actually translates into the “charging” of ATP. What this tells us is that theoretically any form of kinetic energy can also be converted into chemical energy and thus utilized by autotrophs to sustain life. If you want a very thorough explanation of the ATP synthase complex you can look [here](http://earth.callutheran.edu/Academic_Programs/Departments/BioDev/omm/jsmol/atp_synthase/atp_synthase.html).
So, from that analysis we know that any source of energy that we can convert directly into chemical energy, into an electrical or chemical gradient, or into kinetic energy could potentially be used by a lifeform. Let’s take a look at potential energy sources.
**Kinetic:** Our planet has tons of kinetic energy lying around and I imagine it won’t be unique in this. Atmospheres have wind, hydrospheres have evaporation, rain, rivers, waves, and tides. Even the ground can have earthquakes, landslides, and tides. All of these are potentially usable forms of energy. We know it’s possible to convert kinetic energy into chemical energy with proteins, it’s just a matter of an organism finding a sufficiently efficient way to do it.
**Gravitational:** While this overlaps somewhat with kinetic (like rivers flowing downhill) I wanted to make a special mention of tides and elliptical orbits. When a gravitational field changes substantially like on a moon orbiting closely to a large planet and therefore having strong tides it could provide an opportunity for a lifeform to steal some energy. Imagine an organism that can pump a fluid up and down very efficiently. Pumping the fluid up it expends energy. Allowing the fluid to flow back down it is able to extract energy. If the organism pumps fluid up while the tides are in and gravity is relatively weak, and lets it flow back down while the tides are out and gravity is strong there is the potential for a net profit in energy. The system would need to be incredibly efficient and the changes in the gravitational field significant, but in theory it could work.
**Heat:** Presumably any heat differential could be harnessed to produce energy. This heat differential could come directly from the sun, or from the ground as geothermal energy. Heat differentials like those between sun and shade or between thermal layers in a body of water or an atmosphere could be used to create electrochemical gradients or kinetic movement.
**Pressure:** Buried liquids in the form of artesian aquifers, geysers, or petroleum could provide a source of energy. By releasing the pressure the organism would be generating kinetic energy that could be converted to chemical.
**Radiation:** Radiation in the form of alpha and beta and gamma particles all generate high energy chemicals. In water-based organisms these are peroxides, but the principle should be similar with other chemistries. Radiation thus directly generates chemical energy, it’s just up to the organism to efficiently harvest it.
**Electrical:** Natural processes can generate electrical potentials, such as lightning. An electrical gradient can easily be used to generate chemical energy as seen by the electrochemical gradient used to make ATP.
**Chemical gradients:** Chemical gradients can be formed by natural processes. Fresh water flowing into salt water for example. Evaporation can concentrate solutes and rainfall can dilute them. Organisms could potentially derive energy from any such gradient.
Hopefully this is what you were looking for, let me know if you'd like more concrete examples of how certain things might work and I can elaborate, but I wanted to avoid rambling about hypotheticals for pages and pages.
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Based on the groups I see that we have defined there are two categories of autotrophs:
1. Chemoautotroph
2. Photoautotroph
This is simply because the most common forms of energy readily available to organisms are solar energy and chemical energy.
Theoretically, if an organism just needs energy to survive, you could engineer an organism that uses any form of energy a planet has. For example Geothermal Energy. If there are no other types of energy around, an organism could probably transfer dissipating heat into the energy required for life. If we are able to harness [heat energy for powering fans](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=thermal%20powered%20fan), perhaps an organism could similarly use that energy to survive.
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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.
In [this question](https://worldbuilding.stackexchange.com/questions/30957/what-if-we-lived-near-a-boundary-of-the-universe) I asked about the possibilities of what a boundary might be like, with emphasis on the storytelling.
Now I'd like to investigate what a hard boundary would mean in quantum mechanics, in a more “hard SF” manner.
Imagine a bubble of walled-off spacetime that occurred in the lab so it could be examined up close an personal. Whether the inside is in stasis, destroyed, censored, or whatever is not important here. The interesting thing is that a boundary exists and quantum-mechanical wave functions are prohibited from entering the region contained by the boundary.
Imagine, perhaps, that it's an energy well of arbitrary height. Or, I'm intrigued by @Beta’s remark, *“The mirror is 100% legal; all fields and space-time curvature are symmetrical at the boundary, or equivalently the boundary condition allows no normal components of anything.”* Or, it just somehow prevents a wavefunction collapse from ever choosing that position.
The phenomena resulting from this should be benign. It needs to interact with normal matter! The bubble won’t just fall through the Earth like a neutrino, or [fly off at the speed of light](https://en.wikipedia.org/wiki/The_Billiard_Ball).
Rather, it needs to be massive so it can stay put in the room, follow the standard path through spacetime like a massive object, and be held and pushed by normal matter. E.g. **it could be placed in a stand and stay put in the lab, even as the Earth turns under it**.
I'm thinking that something like Pauli Exclusion could be made to work: the electrons of matter would feel the excluded bubble nearby and distort the shape of the wave function, requiring higher energy. Making it a hard solid object is the main issue!
Second, what might be happening very close to the edge? If it's pushed and must move like a billiard ball, but it is not a point-mass, the force must somehow be communicated around the entire space. If it's [infinity rigid](https://en.wikipedia.org/wiki/Born_rigidity) there would be problems with motion due to relativistic effects.
Anybody up to communing with the Hamiltonian?
[Answer]
I'm a physicist, but an experimental one. This means I don't deal with hypothetical stuff like this very often, and when I do, I feel the need to figure out a real-world example or test for it. Also, this post contains a fair amount of math and is a little lengthy, so this is your warning. The bullet points at the bottom show my summary and conclusions from this.
I'm afraid I have no idea how to develop such a thing; an object or region of space that is an infinitely high energy wall to particles. I know normal matter and fields can be energy barriers, but I don't think any of them can be infinite in height. (They can be, however, *practically infinite*, which is something else entirely!) That second question, though, is something *I can* tell you about.
I'm going to assume some nice symmetry (like a sphere) so that the math is easy, but we also get to really focus on what it means to have an infinite plateau. I'm also going to assume, since this is a macroscopic object, that I don't have to worry about electron tunneling (that changes the problem setup and answer).
As I understand it, your potential energy is a discontinuous, piece-wise function which looks like:
>
> $U(x) = 0$ outside the object ($x\geq0$)
>
>
> $U(x) = \infty$ inside and on the border of the object ($x<0$)
>
>
>
Therefore I'm going to use the [one dimensional time independent Schrödinger Wave equation](https://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation#Time-independent_equation).
$$\hat{H}\Psi = E\Psi$$
$$-\frac{\hbar^2}{2m}\frac{\partial^2\Psi(x) }{{\partial x}^2}+U(x)\Psi(x) = E\Psi(x)$$
Inside the object (on on the border) $\Psi(x) = 0$ is the only solution. That's boring, and we don't really care about that, until we start applying boundary conditions for the other part. Now, just outside the object is where things could get interesting:
$$-\frac{\hbar^2}{2m}\frac{\partial^2\Psi(x) }{{\partial x}^2}+ 0\Psi(x) = E\Psi(x)$$
$$-\frac{\hbar^2}{2m}\frac{\partial^2\Psi(x) }{{\partial x}^2} = E\Psi(x)$$
Since the wavefunction must be 0 at the boundary (x=0), I'm going to say:
$$\Psi(x) = A\sin{(\alpha x)}$$
If we solve for $\alpha$, we get an equation like:
$$\alpha = \sqrt{{\frac{2mE}{\hbar^2}}}$$
and after [normalizing it](http://www.wolframalpha.com/input/?i=solve%20%28int%28%28A*sin%28a*x%29%29%5E2%2Cx%29%20%3D%201%2C%20A%29), your wave function looks like:
$$\Psi(x) = \Bigg(\frac{2\sqrt[4]{{\frac{2mE}{\hbar^2}}}}{\sqrt{2\sqrt{{\frac{2mE}{\hbar^2}}} x - 2\sin(2\sqrt{{\frac{2mE}{\hbar^2}}} x)}}\Bigg) \sin{\Big(\sqrt{{\frac{2mE}{\hbar^2}}} x\Big)}$$
Which is pretty ugly. However, there are some takeaways from this:
* $\Psi^2$, which shows the odds of finding a particle interacting with the plateau at any particular point in space, is a decaying sine wave. (See [here](http://www.wolframalpha.com/input/?i=Plot%20%282%20Sqrt%5B1%5D%29%2FSqrt%5B2%20x%20-%20Sin%5B2%20x%5D%5D%20sin%20%28x%29%29%5E2) for a generalized, not-entirely-accurate plot where $\alpha = 1$.) This means that what happens near the edge also happens in set distances away from the edge.
* VERY close to the edge and at some particular distances, the wavefunction goes to zero. This means near the very edge of this object and at some particular distances, there is a "true vacuum." (This also makes me think of [band structures](https://en.wikipedia.org/wiki/Electronic_band_structure), but it's not the same!)
* It doesn't really matter what the energy of the particle is; the energy just acts as a scaling factor in this equation. All particles approaching this object behave in the same way.
* A particle near this behaves like it's in an infinite well, but also a little bit like a free particle. It can have any energy level, but still goes to zero at some points in space.
* This also assumes there is only one particle interacting with the object. Multiple particles, especially ones that interact with each other, can change this wavefunction. This isn't entirely useless, though! It can act as a guide for our intuition for \*real world\*$^{TM}$ situations.
] |
[Question]
[
In the vein of this question [here](https://worldbuilding.stackexchange.com/questions/25899/anatomically-correct-gods), I was wondering about the practicality of the mythical Grecian concept of the [Hecatonchires](https://en.wikipedia.org/wiki/Hekatonkheires). Forget, for a moment, that these monsters are supposed to be invincible. Now, wonder how one such monster (with 50 heads and 100 arms) could be defensible.
I imagine a head array (all of them in a line, ear by ear) to be most inefficient, especially if the opposing side has snipers:
```
_ _ _ _ _ _ _ _ _ _
/ / / / / / / / / . .\ *Can somebody say headshot times 50?
\_\_\_\_\_\_\_\_\_ U_/
```
Then, consider also that we need to fit 100 hand/arm mechanisms on this thing. If all of these limbs were located on the side of its torso, at the very least its midsection would be a huge, bullet-soaking pillar--even before we give each arm enough room to swing up and down without interfering with its neighbors.
So, assuming that this creature must be a bipedal humanoid-ish monster--i.e., no Mr. Fantastic's elastic limbs; there are bones in this thing's arms, although the length, number of elbows, etc. are debatable--how should this creature's parts be arranged?
In other words, **what is the most practical way of constructing this ludicrous monster such that its extra heads and arms are useful** (e.g., having the skulls arranged like parapet stones), **and so that it could properly be deemed a formidable foe even in modern combat?**
(Note: I use modern warfare to exemplify the weakness of a "copy a human 50 times horizontally" design, though the Hecatonchires need not be foisted into our space-time continuum. Even in the mythic past, however, a monster with a spaghetti of flailing limbs, and for whom armor construction is nigh impossible (Hephaestus notwithstanding) still seems hardly defensible. Also note that *what* these things would be wielding in their 100 arms is another question altogether).
[Answer]
I think the best way to use these guys in a modern setting is as ship captains. Instead of having an entire bridge crew, this one guy could be issuing orders, reading and analyzing data, manning wheels and control stations, and generally doing the work of up to fifty people. Not only that, but since it's just one guy, there won't be any confusion trying to communicate: he's going to know everything.
In other words, I don't think they would be used in primarily combat roles. Just trying to fit one hundred human arms through a door doesn't sound easy, so unless these creatures are about the size of a centipede I don't want them leading any charges. Instead, logistics and machine operation are where they're going to excel.
For such jobs (or just in general), I'd say the best configuration is as a sort of sphere, with heads and arms at regular intervals. You could probably throw legs out entirely, as there are few cases where these creatures won't have at least a couple arms handy (pun). I'd bet there would be custom workstations built for them, with panels and screens in places where they can each reach a different head/arm.
If you still want to have these guys on a battlefield, perhaps they can drive specialized tanks. These tanks could be covered in cameras and viewports and feature a wide array of weapons, to the point where it would appear not to have a weak side. It could also serve as a mobile command post, as the hecatons will probably have some heads and arms available for coordinating troop movements and even piloting drones.
As a suggestion for a more medieval setting, I suggest the shield ball (pun?). Much like a shield wall, the hecaton will be covered by a series of fifty interlocking shields. The non-shielded arms will each carry a spear. To move, the hecatons will push off with the back spears and roll. Not only would this be absolutely terrifying, but the hecatons could continuously shift their orientation, moving fresh arms to the front and tired arms to the top or sides.
The shield ball could even be useful in modern riot control, but modern warfare really is more about hiding than anything else, and the hecaton's going to stick out like a sore thumb.
For an idea of the general shape of such a creature, consider the [Deltoidal hexecontahedron](https://www.wikipedia.org/wiki/Deltoidal_hexecontahedron). Each face of this shape would contain a head and two arms, albeit with ten empty spaces (I couldn't find a satisfactory 50-sided version). With this structure in mind, I'd estimate the hecatons would be from 6 to 8 feet tall (around 2m), and just as wide. I'd recommend making the heads a bit small to give the arms room for solid muscle structure. Due to the large number of awkward angles, such a creature would most likely smell terrible (they may quite possibly have invented aerosol deodorant before the wheel). Caloric intake will need to be higher than that of a normal human, but definitely not fifty times higher; different heads may have to take turns eating meals. Each head should be built to handle being pressed into the ground quite often, so I'm thinking flat noses and sunken eyes.
[Answer]
I know this question was asked a while ago, but I have a different idea I'd like to put forth: four-dimensional hecaton humanoids. Essentially, it would use a four-dimensional hyper-humanoid shape, which would essentially be a layering of humanoid forms in the fourth-dimensional direction, which gives it more bodies to put arms and heads on. In three-dimensional space, only a portion of it would be visible at any given time, based on the direction it was viewed from and how it's moving, and much of it would appear to be self-intersecting. The effect would be similar to viewing a hypercube (there are VR games that have been made to simulate this), but much more complex, with moving arms and heads and torsos and such. Ideally, they would all be anchored together at the waist/legs, so that portion of their body would exist normally in 3D space.
Is it a formidable foe? Yes. Essentially it's a normal durable humanoid giant-titan thing that has a ton of redundancy and the ability to use 100 hands and 50 heads without self-interference, and it's nearly incomprehensible to any observers or opponents. Fighting it would be a trippy but assuredly deadly experience. Even if you take out the legs, it could probably still use its hands to move, and it might actually be more dangerous to take out the legs, since that would separate the bodies, leaving you to fight 50 separate 4D giant torsos, all working together. Short of nuking it, there's not much you could do to it that would kill it before it killed you, unless you get very creative.
tl;dr, a multidimensional eldritch abomination
] |
[Question]
[
Ignoring, for the sake of this question, *how* exactly the gravitational fields required for this to work are generated:
## The question
Our stalwart adventurers have a spaceship, perhaps a [gateship](http://stargate.wikia.com/wiki/Puddle_Jumper), fitted with inertial dampeners (for preventing their organs from being liquefied) and artificial gravity.
The artificial gravity exerts a constant downward acceleration of 10 m/s2, and the inertial dampeners provide a variable multi-directional acceleration exactly counter to the acceleration of the ship itself.
Assuming that the artificial gravity generator is perfectly efficient (i.e. only the energy required for the gravity itself has to be accounted for) and that the artificial gravity only affects the things within the ship, not the ship itself: How much power is required to run the toys?
## Examples that need to be accounted for
For each example, the ship contains 1 000 kg of stuff that needs to be affected by the gravity fields created, referred to as the *payload*, and itself weighs 49 000 kg; for a total mass of 50 000 kg. For the purposes of cross sectional area, the ship can be modelled as a cylinder with a diameter of 3 meters and a height of 10 meters, where the front and back of the ship are the flat ends.
### Coasting
The ship is in a stable orbit around a planet. The ship experiences an apparent acceleration of 0 m/s2, and the payload experiences a uniform downward acceleration of 10 m/s2.
### Manoeuvring
The ship is transferring between two orbits, burning prograde with a uniform acceleration of 5 m/s2. The crew is experiencing no lateral acceleration and a uniform downward acceleration of 10 m/s2.
### Under attack!
The ship is in orbit, experiencing an apparent acceleration of 0 m/s2 when a [photon torpedo](http://en.memory-alpha.org/wiki/Photon_torpedo) explodes 10 meters off the port side of the ship, releasing one gigajoule of energy. The ship holds, and experiences some lateral acceleration as a result, but the crew experiences no lateral acceleration, and a uniform downward acceleration of 10 m/s2.
For each of the above examples, accounting for all forces, how much power is required by the artificial gravity generator?
[Answer]
**Note** *I don't know how the artificial gravity is produced, but I am assuming you can selectively shape a potential gravity well so it affects only the things in the ship; the payload. There are problems with this kind of artificial gravity, and to make this answerable I am going to ignore them. Additionally, the individual forces exerted on the payload will be in various directions for various situations, and I assume the craft is capable of this.*
# Coasting
It could just create a [gravity well](http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html), with the Energy around that of Earth. The equation to figure this out would look like:
$$U=\frac{-Gm\_E}{r\_E}\sum{m\_n}$$
where $G$ is the universal gravitational constant, $m\_E$ is the mass of the earth, and $r\_E$ is the radius of the earth, $m\_n$ is the mass of an object you want to feel this force, and U is the energy of the gravity well. In your specific example $\sum{m\_n} = 1000$. (The ship itself does not need to be under the effect of this gravity well, so it doesn't get added to $\sum{m\_n}$ at all.) So your gravity well looks like it needs to be $6.249\*10^{10}$(-ish) joules deep.
The craft itself contributes to the gravity well, but only a little. The more mass of the craft is centered on one side, the more it can can offset the gravity needed to keep people down. I have ignored the craft's gravity because it's negligible influence. If the ship were a ball that people stood on, with their center of masses 1m away, it would only contribute about $.003 J$. Not enough to substantially affect the gravity well.
Trying to determine the power requirements for bending space enough or producing this gravity well is tricky, because no one has every produced a gravity well like this before, nor have we seen gravity (of an appreciable amount) apply to bodies and then not. This is where sci-fi magic/handwaving comes in. To simply provide an answer, I am going to say that you need $6.249\*10^{10} W$: you need to maintain that gravity well by giving it the required energy for the total depth every second.
Obviously, this value can change depending on your views of how artificial gravity production works, but it's the answer I'm running with. If you think that, once a gravity well is made, you needn't give it more energy to maintain it, your power requirements go to 0 after it's made. If you think gravity wells must apply their energy over [plank time](http://en.wikipedia.org/wiki/Planck_time), then you'll get a very large power requirement (Around $32\*10^{54}$ Watts!)
# Maneuvering
For the people inside the ship to notice no acceleration, the ship's inertial dampener must compensate for the movement of the ship. The well will have to get deeper or shallower by the amount of work needed to keep the people on the floor. This depends greatly on which way the ship accelerates. The equation for this work, though presents a problem:
$$W=\int\_{x\_1}^{x\_2}{Fdx}$$
No, the problem is not the calculus, it is the fact the work required depends on how long the acceleration is experienced. If you attempt to solve this for our specific situation, you get $$W=\int\_{x\_1}^{x\_2}{5dx}=5\*(x\_2-x\_1)=5\*\Delta x$$
That's not hard. Your well changes by 5 times the distance (in meters) traveled. That being said, you don't need to produce this energy all at once; your power requirements may not change all that much. The total fuel you need and the total energy you need to produce will!
The power demand with fluctuate depending on how much you travel per second. It would look like: $$P = \frac{5\*\Delta dx}{dt} = -5\*v$$
That $v$ is velocity. This changes, of course, with how fast you're going. Since you're not jumping from one speed to the next every second, the above equation gives you the instantaneous power you need. I suggest you look at your top speed, as that is the maximum amount of power you need to reach that top speed.
# Under Attack
1 Gigajoule $(10^9 J)$ just got added to the mix! I need to assume that this energy is radiated in a sphere, not just directly impacting the ship. This makes the impact profile of the ship really important. The surface area of a sphere of radius $10m$ is about $1256.4 m^2$ Our serendipitously cylindrical space ship has a side surface area of $10m\*\pi\*3m=94.24...m^2$. This means the ship gets a dose of ($94.24/1256.4=.075...$) about 8% of the gigajoule, or $8\*10^{7} J$. Once again, the gravity well needs to increase by this amount to prevent our payload from getting harmed.
The power needed for this? Well, it depends on how long the explosion lasts. If the explosion lasts a small fraction of a second, you multiply that $8\*10^{7}$ by the reciprocal of that fraction. An explosion which transfers its energy over 1/100 of a second, for example, will require $8\*10^{9}$ Watts to totally negate.
[Answer]
In order to counteract the acceleration of the craft, you need to bend spacetime to produce gravity. The simple presence of mass/energy *does* that. It means you can't switch it on and off because your battery or fuel source, being a store of energy, will produce this gravity!
Note that any other answer will violate Einstein's formula for general relativity, so postulating a way to do that means you can make up whatever answer you like (and make a perpetual motion machine in the process).
The best way to store energy in such a compact form is with mass.
So, imagine a superdense plate—[far denser than normal atom-based matter](http://www.hardsf.org/HSFRIndi.htm)—that can be moved forward and back. Actually, move the people's beds forward and back. As the ship accelerates beyond the gs that a human can withstand, move them closer to the dense plate in front of them, so its gravity counters the acceleration.
---
If you could somehow apply an acceleration to all the particles of the person's body individually rather than just pushing on one surface and letting the compression transmit the force throughout the body, he would feel no accelleration. As suggested by Abulafia's answer, the energy would be the usual amount to accelerate that mass,
But, you would have no need to *counter* the ship's acceleration using that technique. That would *be* how you accelerate the ship (or portions of it) in the direction you want to go, and the occupents will feel nothing. So, it's not energy in addition to the thrust, but simply the manner of applying the energy you need according to Newton's second law, anyway.
You might still need extra energy though: if the device is carried on the ship, it might be recoiling from accelerating the people etc. which is the opposite of where you want it to go. So you need another thrust to push the device (and everything it's carrying), if you can't divert the effect directly. So, for the sake of plot, a very understandable approach is that the energy needed to thrust doubles to stay put and then applies a third time to really move as intended. Thrust with inertial dampening **triples** the normal energy of acceleration (less the 1g residual you want, plus inefficiency in the mechanism).
] |
[Question]
[
You may have heard of [pyrophites](https://en.wikipedia.org/wiki/Pyrophyte) : They are plants which have a strong relationship to fire, whether they are extremely resilient to it, blossoming with it or simply as a way for their seeds to sprout.
I am devising such a plant that has an aggressive way of expanding, burning their surroundings to ensure they will get light, and maybe even retrieve specific resources from the cinders. Kindikinda like [Slash-and-burn](https://en.wikipedia.org/wiki/Slash-and-burn) agriculture, without the slash part. This plant would emit slow-falling spores or seeds, very hot to the touch, and which may be even in flames as it lands on the ground.
**For that purpose, I would like to know if such seeds could exist?** The seed can be any shape and material you can imagine, as well as the type of plant producing it (tree, bush, grass, mushroom...). However, I'd very like it to respect physics, and to be based on concepts close (though not necesarily the same) to real world biology and chemical equivalents. Still, I won't be sad if you don't bring up scientific documents and calculations to support your solution (unless it's extraordinary, of course).
To help you, below are specific goals I wish to reach.
* The seed, at its landing, should make at least dry grass burn. Ideally, this should be doable on wet grass or other plants. Therefore, they should be also quite hot.
* Keep a hot temperature at the touch if you catch it during its flight. At the very least warm, but I'd rather have something uncomfortable to keep in your bare hands or even dangerous to hold.
* [*Secondary*] Produces itself (or through the plant) the heat that makes it feel hot.
* Be able to fly/glide on its own to reach new places to grow and to avoid annoying its parent. So pretty far away, and high enough. There can be winds, and even a strong upwind coming from fire around the plant to give them a head start.
* Be strongly resilient to a continuous, high-temperature during its lifetime. The seed must sprout one time or another :).
* Small-sized OR very slow falling basketball-sized fruit ones : Being small gives the seeds many more uses, and it would be so nice to have raining fire seedflakes ^^. But, I also had the idea of making them bigger sized, burning jellyfish or floating chinese lamp-like fruits. Nothing really between the two, however.
* *[Secondary]* The seed can start a flame on its own through a sun-independent mechanism. Some pyrophites are naturally prone in making fire through sunlight and inflammable oil production, but maybe this can be automated without the sun's help?
* *[Secondary]* Be able to keep a flame during the travel. That is, find ways to have a flame persist, like a candle last longer than a match. The longer it can keep it, the better.
Note that I tagged some objectives with "*[Secondary]*" : If you can't reach that goal from a scientific approach, then simply waive it away telling that you haven't managed to make it (that's okay! I can understand ;)). Then continue on, supposing this goal is reached through magical or other unknown means or is simply isn't part of the solution. Still, the more goals you can complete and include at once, the better it is!
[Answer]
Bear with me here.
So your seed has an outer gel coating that is extremely flammable and will burn hot for a decent amount of time. Then an inner protective layer which separates the seed part of the seed from the flammable part.
These seeds are contained in a large-ish gas sac filled with flammable gas. And on the outside of those gas sacs, there are little bulges that contain two separate chemicals that, when pressure is applied, the separating barrier breaks causing them to mix, which results in a mini-explosion that ignites the gas sac, causing the whole thing to explode.
When it explodes, it launches those seeds into the air and ignites them so that their outer coating is on fire.
When the seeds land, the coating sticks whatever it lands on causing it to set on fire. The seed of course is non-flammable so it survives and when the fire burns out, it has all this wonderful ash fertilizer to grow in.
Now, how do these sacs get the pressure they need to activate the chemical reaction? Simple, there are multiple sacs, and the gas inside them is lighter than air so that they kinda float like a balloon. They are of course attached to the trunk of the plant so that they don't float away, but when an animal, insect, or just a light breeze comes along and either bumps against or causes the sacs to bump against each other, it activates the combustion mechanism and boom you have exploding gas sacs, sending flaming seeds all over the place.
Now as to the flameproofing of the plant itself, that's simple, the plant secretes a flameproof gel onto the outside of the plant making it fireproof.
[Answer]
Many of these requirements should be achievable, although it may require some hand waving. Quite a few chemicals spontaneously combust when brought into contact with other chemicals. Many of the alkali metals combust on contact with water or oxygen, although both of those will likely be present everywhere in your plant, so this is not a good idea. Sulfuric acid produces flammable hydrogen when encountering metals and will produce heat when mixed with water. This could be used to start combustion when needed. All of these chemicals are able to be produced in living organisms and this is therefore probably an okay option. These could be stored separately in an outer casing around the central seed and could be mixed when needed. Sulfuric acid may degrade over time or entirely destroy the seed, so if anyone has any other suggestions then please tell me.
The inner seed would need to be fireproof and the outer shell would need to contain some flammable oils. The seed could also utilize a "hot air balloon" type of floating by using its heat to produce hot air, which is lighter than cold air. This would be more effective with a larger balloon size due to the square-cube law, although smaller seeds could augment their flight with wing-like structures.
[Answer]
**There are many such as you describe.**
[](https://i.stack.imgur.com/iSxxy.jpg)
<https://www.landscapesinmotion.ca/updates-1/2017/11/10/a-wildfire-story-severity>
"Serotinous" seeds which require a fire trigger to open are common in parts of the world where fire is common. I am familiar with the lodgepole pine from the northern US.
<https://www.nps.gov/articles/wildland-fire-lodgepole-pine.htm>
>
> The bark of lodgepoles is thin, which does not protect the trunks from
> scorching by fire. They die easily when a fire passes through.
> However, the serotinous cones give lodgepole pine a special advantage
> for spreading seeds for the next generation. These cones are closed
> tight with resin that melts during a fire and releases seeds that have
> been stored for years. These seeds germinate in conditions that favor
> the tree’s seedlings, where the forest floor is clear and plenty of
> sunlight shines through an open canopy.
>
>
>
The cones can open by catching fire, or just by getting hot. The one depicted here burned a little but will be fine and is getting ready to make a tree. I will testify that it is possible to burn these cones completely in a campfire, but if you get one lit by itself it will generally go out. There are other pine species that do this as well as unrelated species.
<https://en.wikipedia.org/wiki/Serotiny>
Your only difficult ask is the slow fall. To be triggered by fire but not have the seed itself burn, these fruiting bodies and seed cases need to be reasonable robust, or wet, or both which means they will probably fall pretty fast and not drift around like dandelion fluff.
[Answer]
**Hay fires**
I can't find the English name, but the principal behind hay fires could be a solution.
Hay fires start because bacteria will start some awesome biological processes during their hay consumption. This requires a highly moist environment within the hay. The consumption process releases heat, which in turn quickens the bacteria. At around 55°C (131f) flamable gasses start forming, heating the hay further. This has several stages, but the most important thing is that when it heats up enough and gets oxygen, it'll combust.
This likely won't be directly applicable to seeds. However, it does show that with the right proteins and such you *can* make something hot and combust. The plant can do something similar with overpowered mitochondria or heat generating proteins together with a gas. It'll be hot to the touch and if you give the seed several phases you can potentially create the scenario you want.
Example how it could work:
Seed grows on the plant. When the seed reaches maturity, the plant starts the process to release the seed.
The seed will start internal processes at a certain point, heating up.
The plant can react to a certain amount of heat, flinging the seed or severing it. Thermic reactions take a lot of energy, so you want the heating to only be done when at the best moment. Making the plant let go of the seed when it reaches a certain temperature makes this happen.
The seed will fall down, possibly moving on the wind if enough flight assistance is grown.
Seed will likely settle on time for when the heat is high enough for the next heat trigger, releasing the gas to the oxygen and will catch fire.
**Problems**
The seed likely needs to be rather large to have enough energy to heat up significantly, produce enough gas for the initial burning and fireproofing of the seed. This will impede easily floating on the wind, unless you decouple the firestarter and the seed (launching fire first, seeds after). Regardless, heating up just requires a ton of energy and will always be a problem for the size. Basketball sized seeds would help, allowing also multiple seeds to be held.
If you accept the plant to be (partially) burned, you can also just set fire to the surrounding area and let the seeds fly on the updrafts of the hot air.
] |
[Question]
[
My creature is a [B.O.W](https://monster.fandom.com/wiki/B.O.W.), designed to be especially good at ambushing and to use its Jaws as it's main weapon. It's basic hunting strategy is similar to the [spectral bat](https://en.m.wikipedia.org/wiki/Spectral_bat)'s, immobilizing prey and delivering a bite to the skull to kill it. Additionally, it also possesses a ranged blasting attack from its mouth (supplied by mechanical enhancements inside its chest, no need to enter in the dragon breath matter), but that's secondary. [](https://i.stack.imgur.com/5jm8p.jpg)
*this image is merely illustrative of how I'd like the jaw to be able to move. Source is hyperendocrin giganotosaur from the game "the isle"*
However, observing cases like crocodiles and the T-rex, it appears that their bite force seem to be linked to a lack of mobility in the skull,usually meaning lateral jaw articulation is minimal. The jaw being split also means each half of the lower jaw would need to have all the muscles necessary for the range of movement without being Able to rely on one another's.
Based on this, could the B.O.W keep the necessary bite force, while having a splitting lower jaw, by earth standards? Would it need something like the Dunkleosteus' plates near its head to accommodate such musculature?
Note: the creature is roughly 2m tall, weights around 200 kg and is a good climber, usually surprising prey by dropping on it. It's main target consists of humans (which is why it needs powerful bite). Going for the neck is a secondary strategy, should the head prove to be too heavily protected, but not its main strategy. The creature has an ideal bite force of around 5000 newtons (I planed to use bony plates as dentition, since they'd help minimize the contact surface and concentrate the force in a piercing/shearing activity), more that what's required to bite through a human skull through the temples. Ideally it needs to be able to keep its mouth properly shut when not in use. It's skeletal system is an endoskeleton.
[Answer]
This is certainly possible (snakes do something similar, having the mandibles articulated at multiple points including at the chin), however a design such as this would have a particular problem that would need to be overcome.
Consider the task of using a pair of chopsticks. As you apply pressure via the chopsticks, there is a tendency for the item being held to rotate sideways and for the chopsticks to 'cross over', slipping laterally across one-another.
In animals with a traditional arch-shaped jaw, their anatomy often makes such lateral motion of the jaws more difficult and limited, and the muscles that prevent (or facilitate) such motion operate with a large lever advantage across the width of the jaw.
However, a creature such as this is *designed* to allow the halves of the mandible to have great lateral freedom of motion.
Now, the jaw hinge joints may be designed to allow lateral motion when the jaws are open, but restrict lateral motion when closed, but the problem will still arise when biting down upon an object which is not of a known size, that may keep the jaw from being passively pushed into the correct alignment.
The solution to this is to have independent muscles that control the lateral alignment of each half mandible. As the creature bites down, any unwanted lateral motion could be felt and countered by muscular effort until the skull and joint structures engage to enforce correct alignment.
Given that this creature would have very large muscles contributing to a large bite force, the lateral alignment muscles would also need to be large, perhaps up to 20% of the size of the main biting muscles.
It seems to me that the split mandible wirh such a large bite force has little utility beyond that of providing a threat display in that the creature can display a visually disproportionately large mouth, and it would come at a relatively high cost in terms of the musculature required. A creature with traditional jaws that can open its mouth to a particularly large degree is the hippopotamus, which can open it's mouth to an angle of nearly 180°. It too uses its mouth as a threat display, as well as a weapon against its enemies.
Creatures with particularly large bite forces are typically quite capable of biting their food into chunks that can easily be swallowed without the need for snake-like jaw articulation designed to allow swallowing whole prey larger than their heads.
One creature that had both the ability to bite off chunks of flesh and swallow particularly large chunks with the aid of articulated jaws was the (IIRC) jurassic-era dinosaur *Allosaurus*. As it is thought to have been a pack hunter, it may have needed to be able to bite off and swallow large chunks of meat quickly in order to get it's fair share of a large kill.
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It might be possible with the right tendon setup to get some of what you are looking for.
If the tendons wrap around from the inside groove of the split jaw and you have massive muscles on the outside of the split to open the jaw. The muscles would stretch the tendons resulting in a snapping force. I would include some sort of catch in the jaw hinge so that the jaws can be sort of locked open. That would avoid having to spend energy holding the jaw open. This would operate the jaws like a bear trap.
This would result in a lot of force in the initial snap but very little force holding the jaw shut. It probably would not have room for much muscle on the inner edge with all that tendon. It would probably have just enough muscle to keep the jaw from swinging open as it walks or runs.
I would recommend backward facing piercing teeth on the split lower jaw because the tendons will be the only thing holding the jaws shut. So, they won't be able to hold onto the prey without some help.
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In a split jaw, the jaws, jaw muscles, and jaw joint would need to all be anchored into the same plane, which would prevent an opening lower jaw. However, if the upper jaw is also split, then the lower jaw and muscles could be attached to the upper jaw, allowing the entire jaw system to move apart freely, resulting in a jaw similar to the chelicerae of a camel spider
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I don't think the jaw can be split and have a powerful bite force but here a few possible ideas:
1. A mechanical split jaw. It already has a mechanical enhancement for it blast attack so it could have an extremely powerful mechanical jaw.
2. Don't have the jaw split, have it open really wide so its own blast attack doesn't burn its own mouth. The Hippo has the 2nd most powerful bite at 8100 newtons and their mouth can open ridiculously wide.
3. The split is like an insects mandibles but their attached to a lower jaw, they wont be capable of a strong bite force but used for better latching on to their prey, when the flaps/ mandibles fold down they reveal some serious tusks that will be perfect for cracking skulls.
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I've been reading some of the excellent answers on [this question](https://worldbuilding.stackexchange.com/questions/23513/how-could-a-galactic-empire-work) about galactic empires and it led me to imagine a reasonably realistic multi-system 'empire' might keep most or all of its population within a single system and have a presence around other stars only for the purpose of harvesting their energy.
The most naive conception of such a scenario would be to have a dyson swarm of some description around each exploited star (built by self-replicating robots) and use lasers or microwaves to beam the energy back to the Sol system. This energy could conceivably also be used by a sufficiently advanced society to produce matter in a kind of long-distance stellar lifting - my back of the envelope maths puts the energy output of a Sol-like star as sufficient for ~4.3 billion kg per second before (likely considerable) efficiency losses.
My crude calculations (based on [this data](https://www.world-mining-data.info/?World_Mining_Data___Data_Section)) suggest that even with only 1% overall efficiency a single star could supply raw material equal to almost eighty times the total mining output of humanity in 2017, though I have no idea how optimistic (or otherwise) that 1% figure is or what proportion of human resource consumption is represented by mining.
The biggest question for this proposal is whether or not it's actually feasible to send energy on this scale across interstellar distances reasonably safely and without it dispersing so much as to be infeasible to collect at the other end. If it is, what's the best way to do so and what would that look like?
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1. **Capture radiant energy in a form easier to transport.** A good way to harvest and transport energy is to convert it into a form that is easier to transport and from which is it easy to reclaim energy on demand. Capturing the suns energy as biomass, harvesting the stable biomass, and later burning the biomass. Slightly edgier is capturing hydroelectric energy by refining aluminum oxide to the stable metal, then later oxidizing the metal and reclaiming the energy.
Your energy operation will not send energy as electromagnetic radiation, but convert the output of that star to a different form that is more efficient to transport.
2. **Your energy capture operation is intrinsically dangerous, and so is kept out of the neighborhood.** An example would be creation of antimatter. The antimatter is kept out of the home system because it is so dangerous. Perhaps this outside system is not the first one used for this endeavor, as prior implementations have damaged the systems they were in beyond use.
Antimatter is the regular thing people think of - maximal energy density, goes boom, someone tried to blow up the Vatican with it, OK. But I think to keep it edgy you need to take it up a notch. Have them capturing energy and storing it with [Casimir forces](https://en.wikipedia.org/wiki/Casimir_effect) or [Z point energy](https://en.wikipedia.org/wiki/Zero-point_energy), or maybe something to do with string theory. When that system goes kablooey you mess with space/time and dimensional boundaries and things get spooky in a hurry. Definitely something to be done in someone else's backyard. The fact that things have gone kablooey in the past will foreshadow a visit to one of those kablooey systems by your characters, so they can learn what flavor of spooky that kind of disaster brings.
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TL;DR: why? a mere kardashev level of 2 not good enough for you? Not enough mass in the sun for you to harvest? Shipping stuff across interstellar distances is very hard, and there doesn't seem to be a good reason for it.
---
The obvious answer, for energy at least, is a [Nicoll-Dyson beam](https://www.orionsarm.com/eg-article/48fe49fe47202) (also [youtube](https://www.youtube.com/watch?v=RjtFnWh53z0)) which is where you build a dyson swarm and turn it into one giant phased-array laser. You could certainly hit a planet-sized target a few tens of lightyears away (too lazy to work out practical focussing distances right now, though).
The biggest problem you'll have is *receiving* the power. You'll need a pretty big dyson swarm of solar receivers, and you're going to start hitting the limits of available mass in the solar system. Then you'll have problems of efficiency... you're already going to be sucking up as much power from the sun as possible, and inefficiencies are going to make your swarm pretty hot. Suddenly, you're not only doubling the amount of power you're absorbing (and hence doubling the amount of waste heat you'll be producing) but you're *also* pointing gigantic lasers at the bits of your dyson swarm most suited for radiating heat away.
Harvesting mass from stars via some starlifting mechanism is possible, but getting it back to your home system in the absense of FTL, wormholes or some sort of very fast sublight mechanism probably involving reactionless drives is going to be very, very, *very* time consuming. Making giant solar sails and propelling them with your dyson lasers would work. Not sure how best to slow down at the other end... you've probably stopped any chance at using magnetic breaking (your dyson swarm is going to interfere with the solar wind, and you won't want to waste all that energy anyway) so you'll need to beam right back at them... but that means you can't have more mass in flight that you could boost with a single dyson beam at a time (because otherwise you'll be bombarding your home dyson swarm with hypervelocity giant solar sails continuously, and that sounds bad to me).
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[
For practical purposes I think about something in line of Cessna 172. As it was the most produced aircraft, then it must have hit some sweet spot or be near it.
* atmosphere with barely noticeably higher oxygen content, and much higher nitrogen
* tech level similar to contemporary
* rugged, simple, inexpensive aircraft that can serve well on sparsely populated planet
OK, so how to adjust it for such planet?
Assuming that I get physics correctly, in order to keep the same performance, it would need roughly the same engine, frame, but wings would need just 1/3 of surface area from Earth. So my first guess would be a Cessna clone, but with trimmed wings... ok with much smaller wings.
Honestly, does it make sense? Or maybe under such lift friendly condition this wing size reduction offers minimal gain and when having such leeway there would some clearly more tempting things to improve instead for an utilitarian bush aircraft? (Dunno minimum take off distance, load, whatever?)
Question: **Is such wing surface reduction correct way of making rule of thumb aircraft adjustment for thicker atmosphere? Assuming "Yes", does it make much sense for its intended function?**
EDIT: Extra food for thought: Does such aircraft actually need normal wings at all? Seriously. Under normal conditions small part of the lift comes from aircraft body. When the need for lifting surface is reduced, then the share of the lift provided anyway by the body would increase, but I'm not sure whether that would be significant enough to matter much in design.
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TLDR: Your hunch is correct. Shorter wings.
You ask, "does such aircraft actually need normal wings at all?" The answer is an emphatic no. In fact, aircraft on Earth don't even need traditional wings. Check out the [X-24](https://en.wikipedia.org/wiki/Martin_Marietta_X-24).
[](https://i.stack.imgur.com/wqtc7.jpg)
You still need control surfaces, but in a high pressure environment you don't necessarily need wings. It would be helpful to find a vehicle that flies in a setting that has higher pressure than the surface of the Earth. Fortunately, we have just such a vehicle in the form of submarines. After all, you're talking about the pressure 100 feet/30 meters under water on Earth. On submarines, [diving planes](https://en.wikipedia.org/wiki/Diving_plane) serve a somewhat similar function to airplane wings. Notice the two stubby sets of diving planes at the stern of the boat in the picture.
[](https://i.stack.imgur.com/GdDov.jpg)
This [WWII crew manual](https://maritime.org/doc/fleetsub/chap18.htm#18C) describes the effect of planes on submarine maneuvering:
>
> The bow planes are placed on ten degrees dive and rigged in
> automatically unless the conning officer gives other instructions. A
> report, "Bow planes rigged in," is made to the conning officer. Speed
> is increased to about 6 knots to give maximum lift. Due to the
> up-angle on the ship, the increased speed makes the inclined surface
> of the hull effective and the resultant lift raises the ship.
>
>
>
Beyond wings, other parts of airframes would need to be redesigned. For starters, there would be a stiffer penalty for drag, so I imagine aircraft would be more streamlined. I've flown a 172 and they're amazing, but they don't have the sleekest profile. You'd also have to change the engine to accommodate the different pressure and O2 concentration, and you'd have to use a different design/pitch on the prop.
With greater lift and drag, I imagine flying a small plane might look a lot like a [STOL competition](https://www.youtube.com/watch?v=Bo7-BuNiP6Y).
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Firstly, lift and drag are both linearly proportional to atmospheric density, so at 3 atm, to provide the same lift as a plane on earth you need 1/3 the wing surface area.
This can be a mixed blessing: while you wings are smaller and thus less draggy, to achieve a reasonable velocity during cruise the airfoils need to be thinner to reduce pressure drag. This means you have less space in the wing for reinforcement. The optimum point of how long and thin the wing should be before it's in danger of snapping is complicated and an exercise I leave to the reader.
Now, because of the greater density, you control surfaces can be smaller, which will help with drag. Your body will also be as streamlined as possible, looking more like a racing airplane. The surface is also as smooth as possible. Internal deploy-able landing gear is a must.
Now, fun fact: higher density air means better engine cooling, so you might be able to forsake those pesky radiators altogether and use a simpler air-cooled engine which will be lighter.
Here's an example: [](https://i.stack.imgur.com/uTMuW.png)
Short, thin wings for cutting through the thick air at speed, rudder flush with the tail, and staggered tandem wings for both lift generation and pitch control (allows you to eliminate the tail-plane and its attendant drag).
Airscoop under the propeller nose for cooling the engine and feeding it air.
This is a fighter, so it's got a big bubble canopy, a bush plane will sacrifice visibility for a cockpit that's more flush with the hull to generate less drag.
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Let's say I have a terrestrial planet superficially like earth, except that it rotates much slower (about 10-15 days per rotation) and its atmosphere is ideally several times thicker. If I want this planet to have a substantial magnetic field (3/4 of Earth's as a minimum, though higher is better), what factors can I play with to plausibly provide it that field strength? What approximate values would I need to give these factors to accomplish this?
Here are some ideas I'm toying with (please vet for plausibility):
* Large metallic core
* Tidal Heating: Interactions with the planet's star can generate internal heat and keep a dynamo active. (Would that work?)
* Increase radius: The larger the radius, the faster (m/s) the spin for a given rotation period. The faster the spin the more potential for a strong magnetosphere?
* I read somewhere that Venus's small (non-core generated) magnetosphere can be attributed to some interesting physics happening within its dense atmosphere. Is there a way to take advantage of this phenomena? I presume my planet's atmosphere isn't dense enough nor the phenomena significant enough.
Giving the planet a bigger metal core (and hence making it denser) AND giving it a larger radius would seem to be a good recipe for increasing field strength. [Edit: Removed gravity considerations. Planet can be a Super Earth]
It's not clear to me what variables are the most critical. Is rotation rate more important than core size/composition, or vice-versa? Is internal heating (whether from tidal stress, radioactive decay, or leftover formation heat) as critical as the above two variables? I'm not versed enough in this domain to know.
My understanding is that the exact parameters behind terrestrial magnetic fields haven't 100% been worked out. From what I've read there are no 100% reliable models for taking in a set of variables (planet size, density, etc.) and spitting out a simple value for the strength of a magnetosphere. If this is the case, then all I need to aim for is plausibility. As long as it's credible I can use the wiggle room to our advantage.
Thanks!
[Answer]
How does the Earth's core generate a magnetic field?
<https://www.usgs.gov/faqs/how-does-earths-core-generate-a-magnetic-field?qt-news_science_products=0#qt-news_science_products>
>
> The Earth's outer core is in a state of turbulent convection as the
> result of radioactive heating and chemical differentiation. This sets
> up a process that is a bit like a naturally occurring electrical
> generator, where the convective kinetic energy is converted to
> electrical and magnetic energy. Basically, the motion of the
> electrically conducting iron in the presence of the Earth's magnetic
> field induces electric currents. Those electric currents generate
> their own magnetic field, and as the result of this internal feedback,
> the process is self-sustaining so long as there is an energy source
> sufficient to maintain convection.
>
>
>
Most of the energy from this is thought to come from radioactive decay of elements in the core: radioactive potassium, thorium and uranium. **Increase the amounts of those elements and you increase heat production.**
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Resistance increases with temperature in metals. You might consider giving your planet a nonmetallic core, where temperature increases would improve conductivity or at least not reduce it. Maybe a planet with a supercritical saltwater core? Or a core of molten salt? Those would be big, hot and not as dense as metal. And also awesome.
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Answering the comment with an ocean planet example - how about Ganymede?
<https://en.wikipedia.org/wiki/Ocean_planet>
[](https://i.stack.imgur.com/tQMr8.jpg)
Ganymede is a moon with planetary aspirations, a colossal saltwater ocean, and a nice magnetic field which I here assert is produced by electrical currents formed within its heated internal ocean.
And there is ice on top for your critters to skate on.
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I think your ideas are mostly spot-on. Off the top of my head, you can increase the rotation rate, core density, core size or planet size.
At the edge of the core, [the magnetic field has a magnitude of roughly](https://en.wikipedia.org/wiki/Dynamo_theory#Order_of_magnitude_of_the_magnetic_field_created_by_Earth's_dynamo)
$$B\_{\text{core}}\sim\sqrt{\frac{\rho\Omega}{\sigma}}$$
where $\rho$ is the density, $\Omega$ is the rotation rate and $\sigma$ is the electrical conductivity. I find it unlikely that $\sigma$ could be changed much unless the composition of the core were to drastically change, but both the density and angular speed could be increased. Core density would presumably scale with the mass of the planet, as it would be under greater pressures, and the rotation rate could very easily be increased through a collision early on with another body. (This does assume that the rotation of the core is coupled to the rotation of the planet itself - not an unrealistic assumption.)
According to dynamo theory, a dipole magnetic field scales as an inverse cube; at a distance $r$ from the center of the core, we have $B(r)\propto r^{-3}$. The surface field is then (ignoring the angular dependence)
$$B\_{\text{surf}}=B\_{\text{core}}\left(\frac{R\_p}{R\_c}\right)^{-3}$$
with $R\_p$ and $R\_c$ the radius of the planet and the core, respectively. We can turn this into a scaling relation:
$$
\begin{aligned}
B\_{\text{surf}}=&\;2.5\times10^{-5}\left(\frac{\rho}{10\text{ g cm}^{-3}}\right)^{1/2}\left(\frac{\Omega}{7.27\times10^{-5}\text{ rad s}^{-1}}\right)^{1/2}\\
&\times\left(\frac{\sigma}{10^7\text{ Ohm}^{-1}\;\text{m}^{-1}}\right)^{-1/2}\left(\frac{R\_p}{6370\text{ km}}\right)^{-3}\left(\frac{R\_c}{2890\text{ km}}\right)^{3}\;\text{Tesla}
\end{aligned}
$$
Decreasing $R\_p$ or increasing $R\_c$would decrease the surface-core distance, thereby increasing the surface field. Unlike changing $B\_{\text{core}}$, this won't change the intrinsic field strength, but for inhabitants on the surface, the two are effectively the same (while there *would* be a difference when it comes to things like the van Allen belts).
In your case, you want a (roughly) 15-day rotation period. This means that $\Omega$ will be lower than Earth's by a factor of 15. As $B\propto\Omega^{1/2}R\_c^{3}$, we can reach a magnetic field 75% the strength of Earth's by increasing the core radius by a factor of about 1.4.
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[Jupiter’s magnetosphere](https://en.m.wikipedia.org/wiki/Magnetosphere_of_Jupiter) is immensely strong. Jupiter rotates much slower than earth, and has a much thicker atmosphere, like your requirements. What are the requirements for a similar powerful magnetosphere?
According to [Dynamo Theory](https://en.m.wikipedia.org/wiki/Dynamo_theory) on Wikipedia, three things are needed.
>
> 1. An electrically conductive fluid medium
> 2. Kinetic energy provided by planetary rotation
> 3. An internal energy source to drive convective motions within the fluid
>
>
>
1. An electrically conductive fluid medium is pretty straightforward. Just fill the planet with a high concentration of molten iron or copper. (Earth’s mantle is 8% iron.)
2. The lack of kinetic energy can be compensated for, like Jupiter and like you proposed, making the planet bigger. The equation for kinetic energy is K=0.5mv^2, so increasing mass (m) compensates for low velocity (v).
3. [Earth’s magnetic field’s](https://en.m.wikipedia.org/wiki/Earth's_magnetic_field) heat source can be found on Wikipedia:
>
> The heat is generated by potential energy released by heavier materials sinking toward the core (planetary differentiation, the iron catastrophe) as well as decay of radioactive elements in the interior.
>
>
>
Mix in a little extra [U-238](https://en.m.wikipedia.org/wiki/Uranium-238) and you’ve got a powerful magnetosphere.
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I'm trying to construct a solar system, and I'm toying with the idea that the planet capable of sustaining life was initially outside of the habitable zone, but the star's advanced age has caused the luminosity to increase, thereby shifting the HZ further outwards.
**How do you calculate the increase of a star's luminosity with age? Is there a fixed correlation across all stars? Does it vary according to type?**
Additional details -
* Star is 0.88 Solar masses
* Lifespan is 1.38 Solar lifespan
* Star is still within main sequence, but significantly further along than the Sun, both in total age and in terms of its life cycle.
Any answers would be greatly appreciated.
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I would recommend looking at pre-existing numerical models, rather than computing your own. This has a couple of advantages:
1. You don't need to use any approximations.
2. Factors like metallicity, rotation and composition have already been taken into account.
3. You just need to look up the values in a table - no calculations required.
4. You can also compare values for a star of the same mass and composition at many points in its life cycle.
I usually point people towards the [Geneva grids](https://www.unige.ch/sciences/astro/evolution/en/research/geneva-grids-stellar-evolution-models/) of stellar models. They're easily accessible and simple to use. Let's say you want to look at stars of approximate solar composition ($X\approx0.76$, $Y\approx0.24$). [There's a set of models by Schaller et al. 1992](http://cdsarc.u-strasbg.fr/cgi-bin/myqcat3?J/A+AS/96/269) that should suit your purposes. You probably want [Table 43](ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BAS/96/269/table43.dat), for $M=0.9M\_{\odot}$ - close enough to your star's mass. If you look at [the column labels](http://cdsarc.u-strasbg.fr/cgi-bin/myqcat3?J/A+AS/96/269#sRM2.1), you can see that Column 2 gives the star's age, in years, and Column 4 gives the logarithm of the star's luminosity, in solar luminosities.
I took the liberty of plotting luminosity against age for this particular model:
[](https://i.stack.imgur.com/cG2Ot.png)
Notice the steep increase in luminosity at around $\sim10^{10}$ years, when the star leaves the main sequence and enters the red giant phase. Additionally, I calculated the boundaries of the habitable zone. I assumed that the inner edge corresponds to an [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature) at 273 K, and that the outer edge corresponds to an effective temperature of 373 K - the freezing and boiling points of water.
[](https://i.stack.imgur.com/NGq0E.png)
If you play around a bit and check out different grids of models, you'll indeed see that factors like mass, metallicity and composition strongly affect the evolution of a star, which is why it's important to have fine enough grids of models in the first place.
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To my understanding, part of the reason life is able to exist on Earth besides its ozone layer is due to its magnetic field, which protects the planet and its life against solar winds and keeps the atmosphere from being stripped away. Now, I’m aware that Earth’s magnetic field varies a bit in strength at places as well (from 25 to 65 microteslas or 0.25 to 0.65 gauss), but that’s only against Sol’s winds, which vary from around 400 to 750 km/s depending on where the planet receives the flare.
Since many factors have to be taken into account for such a thing, I am sure there is no one formula that guarantees accuracy, though there likely is one that provides an estimation. Star and planet size, distance from one another, possibly the axial tilt of both celestial bodies, and the frequency of flares are all factors I think are appropriate to keep in mind. Essentially, what I am asking for is a way to determine the necessary strength of a planet’s magnetic field to support life using a given formula, using an Earth-like planet about 1.65 AU away from an F8 spectral type star as part of an example.
---
NOTE: If further information is needed, please ask. I only included what I thought was relevant, so there is a high chance I missed something important.
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# The necessary strength is zero
Perhaps not the answer you are looking for, but it is obvious from our solar system that a planet can maintain an atmosphere without a geological magnetic field. Venus has such an atmosphere and no magnetic field (see considerations). Titan likewise has an atmosphere, although there is insufficient evidence to show that it has always had its atmosphere.
# Do you count an induced magnetic field?
There are planets that have magnetic fields that are not caused by the action of their molten core, as Earth's is. Venus' atmosphere is so massive that it causes its own induced magnetic field. Europa's sub-surface ocean also causes and induced magnetic field. So you could have a planet with no bare geological magnetic field, but once it acquires are large ocean or atmosphere starts to protect itself.
# Other ways to keep an atmosphere
While a magnetic field may [protect an atmosphere](https://en.wikipedia.org/wiki/Atmospheric_escape) on a geological scale, gravity can do so as well. If we made Earth more massive but less dense, then the escape velocity of would be larger but surface gravity could be the same. Taken to an extreme, Saturn has a lower surface gravity than Earth, yet an escape velocity almost four times as high. So tinkering with planet mass and composition can help you keep an atmosphere with no magnetic field.
# You can also continuously replenish your atmosphere
There is some evidence (from isotope ratios) that most of [Titan's atmosphere](https://en.wikipedia.org/wiki/Atmosphere_of_Titan#Evolution) has been lost over geological time. Therefore there must be some means of replenishing it, since it is still there. This means is not clear, but outgassing from inside the planet is one option, as is addition in the form of extra-planetary debris. While lots of comet strikes might not be good for business on your planet, dropping a planetary ring, broken up icy moon, or asteroid belt onto a planet's surface over geological time could potentially provide a stable atmosphere for hundreds of millions of years.
# Conclusion
While not answering the spirit of your question, there are several ways to keep an atmosphere long enough for life to develop without requiring a geological magnetic field. So the direct answer would be that the necessary magnetic field strength is 0 teslas.
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I have recently done a bit of research into this subject myself. I skipped the really difficult mathematical stuff by choosing a planet similar to earth that had the correct specs. Of course, I was looking mainly at the size of the sun, the number of planets in the system, the number of satellites orbiting said planet, where the position of the planet was within the sun's habitable region, and other variables I thought were necessary to support human life. That being said, of the planets in our solar system, only Juptier's moon Ganymede meets similar requirements as it too generates it's own magnetic field. Since it's sibling IO is supposed to be a hot planet I can't see how Ganymede wouldn't be any cooler, judging by it's proximity to Jupiter, although not a sun itself, it is a gas giant. I also took into account the number of days the planet took to rotate around the sun and only chose something within the range of our own planet, assuming that several hundred days give or take was one of the requirements to sustain human life. My planet actually has a slightly longer year than our own but not much more than 400 days. I also chose to have a 26 hour day and an eight day week instead of merely seven, which logically lengthens the span of a month. Hope this helps. P.s. I also took into account that the sun would have to be the same type as our own, in the range of a g-class planet only a few degrees off from Sol. <https://en.wikipedia.org/wiki/Sun>
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I trying to describe colonization of an Earth Like [planet](https://worldbuilding.stackexchange.com/questions/61075/how-to-protect-human-colonists-from-red-dwarf-flares) orbiting a red dwarf in its habitable zone.
* It is **NOT** tidally locked with the [star](https://astronomy.stackexchange.com/questions/19039/is-there-any-way-for-a-planet-orbiting-a-red-dwarf-in-the-habitable-zone-to-not)
* Similar to Earth though somewhat larger
* Magnetic field is strong enough to protect the surface from the flares
* Its year lasts 20 Earth days
* Has large tidally locked moon that orbits it on a distance of 100,000 km
* Obliquity of 90 degrees
What kind of crops should be able to grow on the planet surface to provide food for the colonists?
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# Ability to photosynthesize
Here is a graph of blackbody emission spectra:
[](https://i.stack.imgur.com/LEBDf.png)
The Sun is the 5777K line, while a red dwarf would be more like the 3000K line. The good news is that the spectrum is reasonably similar to that of earth. The chorophyll ab complex in plants has good absorption in both the 400-500nm (purple-blue) and 600-700nm (red-infrared) range. In the case of the red dwarf, that red-infrared absorption will be good. The blue absorption is useful in plants because of scattering in the blue sky makes relatively more blue light available in shade; I don't know about your sky composition, but assuming it is nitrogen-oxygen, there will be significantly less blue light to scatter, and your plants will do relatively more poorly in the shade.
There is [some research](http://www.gpnmag.com/article/red-light-and-plant-growth/) on growing plants under red lights in greenhouses. Some of the things of note are that far-red radiation is good at stimulating flowering of long-day plants otherwise kept in darkness. That means, your plants will likely recognize that it is 'daylight' with red-infrared heavy sunlight. Also of interest, plants grown under red lights tend to have elongated appearances, growing taller with long thin leaves.
Additionally, some cyanobacteria have different accessory pigments that assist chlorophyll in absorbing other ligth wavelengths. Generally, these are evolved for blue light absorption in deep-water, but there are some pychobillin pigments that have good absorption in the 650nm range.
# Ability to tolerate long daylight hours
You mention 90% obliquity, and there is some discussion in the comments about whether that is required or not. I will address the situation of 24 hour light during the growing season. There are many plants on earth already optimized for daylight lengths between 12-20 horus. Obviously, 24 hour dark is a non-starter, but day lengths down to as low as 6 hours can be easily accomodated for plants adapted for shade.
This [paper](https://www.agrireseau.net/legumesdeserre/documents/cgc-dorais2003fin2.pdf) tested four plants under 24-hr photoperiod; lettuce improved yield at 24 hours; cucumbers did well when young but needed 4 hours of darkness as the plant matured; chili's tolerated 24-hr light; and tomatoes did poorly. I found evidence in other papers for clover, chickpeas, oats, and barley all doing well with long (20+ hour) photoperiods.
Generally, I would assume plants that are grown near the arctic circle, especially northern Europe, would be better adapted for 24-hour light. In Iceland, these include potatoes, turnips, cabbage, and kale, and that is just below the arctic circle.
Additionally, plants use a [circadian rhythm](https://www.researchgate.net/profile/Reka_Toth/publication/7704239_Dodd_AN_Salathia_N_Hall_A_Kvei_E_Tth_R_Nagy_F_et_al.._Plant_circadian_clocks_increase_photosynthesis_growth_survival_and_competitive_advantage._Science_309_630-633/links/0fcfd50f7fadce640f000000.pdf) to time how to open and close their stomatae. When their timing is good, their productivity and yield goes up. So your plants will need to 'learn' when to open and close their stomatae for maximum efficiency in permanant daylight. This is just a matter of plant breeding and selecting the best specimins. Although productivity may be low at first, a few dedicated years by some agronomists should yield appropriate 24-hour strains for those crops which are suitable for permanant light.
# Conclusion
A red dwarf has a similar enough spectra that plants would survive, and the presence of far-red light will help the plants manage their flowering cycles. Plants will need to adjust to unusual photoperiods, so there will be some years of low yield while better varietals are bred on-world.
While not all plants will thrive in 24-hour light conditions, there is a good variety that will. Most earth crops will do well with 12-20 hour photoperiods, and shady crops (mostly vegetables; brassicas, leafy greens, many root vegetables) will survive in lower light levels.
There should be a wide variety of plants usable, so long as atmospheric and soil conditions permit.
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Assuming a mage individual has a specific organ or a system (like neural?) that can influence outside material world but in order to do so requires the energy directly fed to the cells in the same manner the muscle and neuron cells do. Meanning that it would only accept ATP or creatine phosphate (CP) and not unrefined glucose, glycogen or fats.
How much energy in joules would be available for such individual to perform an act of magic
1. in a burst - fraction or couple of seconds.
2. short time - tens of seconds to couple of minutes.
3. long period - one or several hours.
4. Through out the day.
2 - 4 meaning how much energy is available per given time value(second, minute, hour) for said period.
Quick google search says there's only around 5 Kcal worth of energy in ATP/CP on average in the body which equals to mere 20900 joules. Note that rapidly depleting most of it will result in death which implies that a person must have a surplus of it to use in the act of magic. The rest is gradually converted from glucose and glycogen.
There's a lot of similar threads but the answers tend to get carried away into total energy capacity via fat or total energy available through out the day being expended in a single act.
Things to consider:
1. Conversion speed between ATP/CP, glucose and glycogen.
2. Waste and other byproducts of said reactions like creatinin.
3. ATP/CP is either evenly distributed through out body or concentrated in the certain parts of it meaning that the net(gross) value may or may not be used fully for the act.
Side questions:
1. what constitution a mage should be to have more energy capacity?
2. Things about diet and possibility of mana potions - something that can quickly add energy(edible glucose) or accelerate the conversion of fat/glycogen(coffeine, creatin or l-carnitine).
3. What could be achieved with the resulting amount of energy assuming a given amount of efficiency(%) - ie it's unlikely that a mage can simply add up energy freely to someone's brain in order to fry it. There has to be a mechanism of transferring said energy which inevitably introduces waste.
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We could play theorycraft all day long about how energy is transported among the body, chemistry, mythocondria etc. with a scientific approach to the question.
I suggest an engineering approach instead. Pick something in the body which is easy to evaluate and work from there.
Let's start with legs. Why? Because you can easily find [energy expenditure tables and calculators for walking](http://www.brianmac.co.uk/mobile/energyexp.htm), and they are the parts that tire out in this exercise. In running you use more body parts, so I am skipping that.
A quick googling for how much percentage of the body weight a single leg represents gives us figures ranging from 10% to 16%. Assuming 10% then, if your magical organ or tissue takes 10% of your mage's body mass, you could have it produce about 60 to 160 calories per hour (the figures in the link I provided, for walking, approximately divided by two since the figures are the expenditure of two legs) in a comfortable manner for a range of time from minutes to hours before the mage tires out. That's approximately 0.07 to 0.19 kwh.
If you want to sacrifice your magical organ (an probably your life) for a lot of energy in a single instant, you could use [XKCD's Zippo Phone article](https://what-if.xkcd.com/128/) for a basis:
>
> An adult man's hand weighs about a pound. The hand isn't the fattiest part of the body, but if burned completely, it would probably give off about 500 watt-hours of energy, give or take. That's 50 times the energy content of the phone battery, and almost 10 times that of the Zippo. It's also about as much as a car battery.
>
>
> And, for that matter, about as much as a sandwich.
>
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That's for the weight of a hand. If it weighted as much as a leg, supposing the same fat content of a hand, it could give almost 16 times that, about eight thousand kwh in a flash.
You can then work on your magical organ expenditure and fatigue sensation from those figures.
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Well, considering the magic comes form a certain organ and uses the same energy source as other organs it is then provided with the same powerbank. Basically it the energy you require per day.
Wikipedia has the [article](https://en.wikipedia.org/wiki/Food_energy) about the average daily consumption. There are numerous calorie calculators, like [this one](http://nutritiondata.self.com/tools/calories-burned).
It is said that if you do nothing, you need about 2000 calories, if you're engaging in serious physical activity you can consume about 4000.
So it is probably reasonable to assume that instead of heavy lifting you could divert same 4000-2000=2000 calories to performing astral manipulations.
2000 calories is, well, by definition, enough energy to warm up 2000 kg of water by 1 degree Celsius, or take- 20 kilograms of water to boiling point. The microwave oven efficiency is about 60%, if mage is as sophisticated he'd be able to boil maybe a dozen kilogramm of brains before passing out from exhausting.
That being said, the impact of the human on the world is not directly linked to the energy stored inside his body. You know, buldoser driver moves mountains without breaking a sweat, a dam builder changes the direction of movement of billions of tons of water.
Thus how much your mage can do is still defined by specifics of your universe: whether mage can manipulate magic in such a way to store some energy somewhere in the astral, or whether one can create magical constructs that functioon in magic like machines in physical world. And of course it heavily depends on how that magic affects physical world, if all that your glan is capable of emitting is limited to four fundamental physical fields it is one case, if it allows for a fine manipulation of fundamental particles, it is completelly different.
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I am working on a novel of a fantasy world on another planet. I am not *too* concerned with scientific accuracy, as again, it's fantasy, but I am not interested in supernatural things for my world. That is, there is no magic in my world, and all the phenomena is natural or organic.
That said, my idea was to have my planet orbiting not a star, but some kind of "star engine" construct, composed of some kind of fantasy mineral/element that only exists in my world that births stars in the manner of a flowering plant. The solar energy would then be absorbed by another sort of material orbiting the planet, some kind of fantasy rock/asteroid chain that safely filters the radiation.
The idea would be that a sort of microstar is generated, absorbed, dispersed on the earth in various ways (some kind of storm/explosion) and then somehow reborn in a cycle, perhaps from a kind of 'pollination' process that is both organic and contributed from the (fairly ancient/medieval/non futuristic) technology of the inhabitants.
So therefore, there's no 'sun' or main star, and no daylight/seasons like there would be on a conventional planet orbiting a sun like star. There would still be seasons, but they would be based around the 'starbirth' of this hypothetical star engine that my planet rotates around.
I would assume the magnetic field of the planet would not be conventionally dipolar but would be more chaotic, but again this fictional mineral rocky chain would help to keep radiation from destroying life (most of the time - there'd be storms of course).
I would like all of this to follow some internal logic and not chalk it up to magic or gods, as there are none. I am not averse to inventing materials/minerals/systems etc., like I said above to explain them. My question is, is this feasible and how far would I go to invent constructs that ensure the planet can harbor life in this fashion?
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Say it's a factory that takes hydrogen and creates fusion.
If the machine had a nebula with lots of hydrogen or a gas giant near by, then automated machines could collect it and bring it back to the factory.
The micro stars could be machines too, since anything that small would not be able to generate fusion on its own.
You need something a lot bigger than Jupiter to even get a red dwarf.
They would be fueled and charged by the factory, and then travel to the planet to start the fusion process to create light and heat.
Depending on how well the harvested machines did collecting hydrogen, you could either end up with a lot of sun machines in orbit making it hot, or a few sun machines in orbit making it cold. Mostly it would be somewhere in between.
**Could life exist there?**
Sure, but it might be seeded, since the sun factory is artificial, everything else could be to.
**What would it look like?**
Swarms of miniture Sun's traveling across the sky. If they weren't organized then day and night would be chaotic.
**Alternative:** just for fun
Ok, so going *way* the other direction, it could be an actual Plant.
Say it's a rogue planet, and at one point the planet was mostly ice. Somehow (panspermia?) a seed lands and begins to grow. It's basically a [beanstalk space elevator](https://en.wikipedia.org/wiki/Space_elevator), growing way out.
*It also puts roots deep down to hold it in place and to harness the planets geothermal energy.* (thanks Tim)
As it grows it begins to thaw the ice and break it down, liberating the oxygen, and burning hydrogen to create heat.
It might not even be fusion, just burning enough hydrogen could warm things up, especially as atmosphere develops to hold the heat.
At some point it grows tall enough to effectively be in orbit, and then proceeds to wrap around the planet as a living ring, still rooted on the planet, and still freeing oxygen, burning hydrogen, and creating heat, warming the planet up until it has a viable atmosphere. Also removing a lot of the water from the surface. Some of the burning hydrogen would reform as water and fall back to the planet as rain, giving a weird water cycle.
Life could develop the normal way, or the seed could be a terraforming engine, releasing life forms as conditions allow.
First single celled things would be released to prepare soil, then lichens.
The plants would be released next, followed by low level life like insects. Eventually higher level life would be released, and then intelligent life when the planet was all ready for them.
It would be similar to the way things develop naturally, but a lot faster. Thousands of years instead of millions.
The intelligent beings may or may not know how the world became the way it was, though the Plant could have a library that they would be able to find if they thought to look, which could be interesting...
It's a fun idea anyway.
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If you aren't averse to getting a little extemporaneous with the science, and you don't mind playing to a common trope:
White holes.
The common trope here is that white holes 'spit matter out' where black holes draw it in. In your case: This white hole spits out clumps of superheated plasma that are too small to undergo fusion on their own, but already have the left-over energy from the star they were before being absorbed into another black hole. Handwave a little about why the plasma comes out in discrete lumps rather than a constant stream (curved magnetic fields at the event horizon, time being fubar near singularities, it doesn't really matter) and you have an entity that periodically spits out a scorchingly hot object that radiates like a star for a while before cooling.
If you add in a kinetic component to the expelled matter (preferably perpendicular to the orbital plane to avoid the possibility of collisions) and your white hole's axis is similarly perpendicular, you avoid the majority of nasty radiation effects, and you can have a (fairly complex, but still bipolar) magnetic field for your planet.
Depending upon the regularity of the 'stellar' births, how long they stay hot for, how fast they're moving when expelled, and whether the stars are expelled symmetrically or just from one pole of the white hole, you can set up an awful lot of different scenarios for your world. Long, unpredictable winters, constant periodic summers, day on one side of the planet but constant night on the other. All of these are options.
Sadly this doesn't lead to the micro-stars dispersing in the planet's atmosphere (unless you like constant firestorms). They just drift off into space. Also white holes (even theoretically) don't operate like I just described. That's the handwavy bit. But you are handwaving into a popular sci-fi trope, and people will understand what you're getting at without you having to resort to gods.
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Real "star factories" are something to watch with wonder from a great distance away.
In the spiral arms of our galaxy, nebula of gasses and dust can be collapsed by the impulse of a nearby supernova. The high energy photons ionize the gasses and the shock wave and plasma containing the heavy elements formed when the supernova's core imploded provide both the impulse needed to collapse the formerly stable body of gas and dust, and seed it with heavy elements useful for making things like planets.
The nebula will collapse into multiple pockets of higher density, which then become even more compressed as gravitational attraction between the particles rises, leading eventually to enough compression that nuclear fusion reactions take place. Voila! A star is born! The energy of the new star clears gasses from the newly created solar system, and also serves to push more gas and dust together in other parts of the nebula, creating more stars, until the nebula is consumed or the density of the gasses and dust becomes too low for further star formation.
Closer to the galactic core, an even more impressive star creation engine exists: the central black hole known to be at the cores of most galaxies.
When there is a great deal of matter in the vicinity, it forms a massive accretion disk around the central black hole, and the rapidly spiralling gas becomes heated to such an extent that it is radiating in x ray frequencies near the event horizon. The rest of the disk is glowing more brilliantly than any star, and is the central engine of quasars.
[](https://i.stack.imgur.com/WJFrE.jpg)
However, the quasar soon consumes most of the available matter, and the central black hole becomes quiet. Over a few billion years, matter flows back into the void and the quasar engine starts up again, only the shock waves and high energy emanating from the accretion disc slam into the gathering clouds of gas and dust and replicate the formation of stars, only on a vast scale. This is often known as a "Starburst Galaxy"
While this is far different from what you are talking about, being near a "real" star factory would be a glorious sight in the night sky as it rises over the horizon. Under some circumstances, it might be visible in the daytime, and would be very impressive at night. Too close and the radiation from the multitude of stars or the accretion disc would become an issue, but you could certainly be within a few to a few hundred light years away.
[](https://i.stack.imgur.com/IbM27.jpg)
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## Context
**God games** are organised, in which a hundred immortals participate. Every "God" is given an alternate dimension. These dimensions are all identical and contain an Earth where Humans didn't yet evolve.
At the start of the games, each god receives a certain amount of god-credits they can spend in a celestial Mall. Three main categories of goods are sold : "Humans and human knowledge", "Colonist tools" and "Satellites and robots".
The humans sold in the celestial Mall are generated based on the humans living on the *original Earth* where they evolved naturally, without the interference of any immortal.
Some one-of-their-kind **legendary items** are also put in auction. Examples of such items include a [magical sperm bank](https://worldbuilding.stackexchange.com/questions/22415/planetary-colonization-by-a-female-crew), a [duplication machine](https://worldbuilding.stackexchange.com/questions/25072/duplicating-people-to-expand-a-civilization) and different sets of magical rules.
During the first stage of the contest (which last a few thousands years), a jury evaluates the gods advancements every hundred years.
At the beginning of the second stage, portals to a human-free Earth are installed on every world. This allows the people from all the alternate Earths to meet each other and interact on a neutral planet.
The criteria used by the judges are numerous and often contradictory. The best strategy for a contestant is to choose a few of them to focus on and carefully craft their [plans](https://worldbuilding.stackexchange.com/questions/25774/colonizing-a-fresh-earth-where-to-place-the-first-settlements) based on their objectives.
But that's not what our protagonist did.
## The Lazy God
One of the contestant is a slacker, and doesn't want to bother with all the complicated rules and strategies. At the start of the competition, he went to the legendary auctions and bought a bottle full of **evolution-influencing spirits** and a **one-way time travel ticket** to send it a few dozens millenniums in the past.
His goal is to let the spirits do all the work and spend the rest of the contest eating pizza and taking naps, leaving his planet on its own.
The spirits are to find the closest thing to humans on the planet and to hasten their evolution. Since they are not omnipotent, they focus on only three aspects of the human evolution :
* Adoption of the upright posture
* Development of the areas of the brain responsible for abstract thinking, logic and language
* Adaptation to an omnivorous diet
## The result
At the end, humans evolved on this version of Earth twice as fast as they should have, but there are still a few differences between them and "normal humans".
The lazy god barely passed to the next stage because his people were on the verge of causing mass extinction and wiping themselves out of existence.
We don't know it yet, but *we are the result of this experiment*.
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## My Question
Knowing that we are the accelerated ones, what differentiates us and normal humans ?
I have already found a few things, but I don't think my list is complete.
**Possible differences :**
* Normal humans are less prone to various **venous problems** like hemorrhoids or varicose veins (their blood system had more time to adapt to standing upright).
* They suffer from less **genetic diseases**, because they had more time to select against them.
* Genes for blue eyes and freckles are relatively recent, so the humanity who had a longer existence could present a **larger variety of skin and eye colors**.
* Because they've been "civilized" longer than us, their instincts/personalities are **less aggressive**.
* They have a less **simian** appearance (I haven't decided to what extend yet).
(Edit : I built the following point on dubious bases and will probably delete it from the list)
* Following some long-term tendencies, their **pinkies** are in a vestigial state and they don't have **male nipples** or **appendix** any more.
What do you think about this list? What should I add to (or subtract from) it to make it complete?
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**Note :** In this setting (civilizations controlled or influenced by immortals), having a long history doesn't mean being technologically advanced. *Normal* humans could live in medieval-level societies for tens of thousands of years.
[Answer]
**Not a whole lot would be different between us and the *slow* humans since a few dozen millenniums isn't really all that long for evolution**. [Modern humans](https://en.wikipedia.org/wiki/Human_evolution#H._sapiens) appeared about 250,000 years ago and the only contemporary *Homo* at the time were the Neanderthals.
The evolution-spirits have a pretty easy time of it since two of their three objectives have already been achieved and they have modern humans as a baseline.
* Adoption of the upright posture - Already present in modern humans.
* Adaptation to an omnivorous diet - Already present in modern humans.
* Development of the areas of the brain responsible for abstract thinking, logic and language - [Debatable when language started and how](https://en.wikipedia.org/wiki/Origin_of_language). Since language allows symbol manipulation, formalized logic and abstract thinking can't start before language.
**What differentiates us from "slow" humans**
They would be behind is several key areas:
* Even if they are only 10K years behind us, they are just starting to develop agriculture and a static civilization.
* Their tool use will be very primitive, just stone tools.
* No written languages yet.
* Specific adaptations to diet or climate (such as fish diets by the Inuit or light skin and hair for the Scandinavians)
Any scientist who studies any aspect of humans would love to get their hands on these "slower" humans. So many theories could be proved or disproved by being able to examine a living example of a human being from 10 or 20K years ago.
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Having explored some of the reasons this is such a hard and open ended question, but likely not given you as useful detail for your aims as you would like, let me now try to give you an easy out. I noticed you implied one of your premises was that we humans are a 'screw up' because were less social, more competitive, and basically fight with ourselves too much, which I already stressed is unlikely to be different if you just hypothesis a slower evolution. However, I can suggest an approach that will give you a pretty good idea for what slow-humans will look like with minimal effort and makes them less aggressive and more good willed. It does have an accidental effect you may not like (or may like, I don't judge) of making them rather..frisky apes though.
My solution is to model slow-humans after [bonobo](https://en.wikipedia.org/wiki/Bonobo) instead of humans. To give some context Bonobo are one of our closest genetic relatives, and quite fascinating. While your probably more familiar with chimpanzees the bonobo are at least as close to us and share a few traits unique to us such as having forward facing hips that encourage upright walking, also makes them the only other mammal to have face-to-face sex. having the closest to human speech, a spontaneous sharing and altruism shared with humans and a general greater focus on collaboration to achieve goals ....and having sex for non reproductive reasons (more on that one below).
Bonobo are also quit peaceful, far more then chimps or even humans. They are female run society, the females having banded together to compete with male aggression through numbers. However, females do not *rule* over males, they have one of the smallest disparities between sexes of all primates, physically and socially. While it's sometimes overplayed to an unrealistic degree they generally have a far greater tendency to work together, spontaneously help each other, and avoid violence (or more accurately make up after violence quickly) then any other primates, potentially including humans.
Final interesting fact, they are closer to chimps then humans. The three lines were all with a common ancestor (called CHLCA or chimp human last common ancestor) when humans split off and went their own way. The chimp/bonobo ancestor continued to evolve as a species before those two split into separate species much later. This is interesting because chimps do not share many of the unique traits that humans and bonobo do, which brings up an interesting question. Did our common ancestor (CHLCA) look more like chimp and all other primates, and humans and bonobo separately developed unique traits like forward facing hips, or did CHLCA already process them and the chimps lost these traits after splitting off from bonobos to look more like 'other' primates?
Okay, putting all this together. I'm assuming you want an easy narrative for why were different and screwing up. Perhaps originally the human line never existed. The CHLCA never split off into humans, instead it continued on it's merry way, eventually split into chimps and bonobos, and later bonobos continued to evolve into the *real* humans.
Your lazy god went back to the time of CHLCA and his spirits saw that the CHLCA was the cloest to modern 'humans', so it started to encourage evolution from that point, creating the human line(s).
This works because bonobo share out upright posture, one of the first things that would be focused on the spirits, maybe the CHLCA wasn't quite as upright as bonobos eventually became and that was the main thing that split us.
However, the bonobo are *very* unique in being a peaceful ape, one of the most cooperative out there. They also have evolutionary pressures (societal ones) that would really help to drive evolution of intellect. They would make sense as the most common species, even above chimps, to evolve intellect if humans didn't come around, and they would do it potentially more peacefully and with a much larger focus on community building, thus the reason slow-humans were seen as less aggressive then humans. It's not that humans evolved wrong to be aggressive, that's a standard evolutionary route, it's that bonobos are unique in finding a niche where non-aggression is encouraged. *they* are the odd ones, but in a good and peaceful manner.
This also helps because you can model your slow-humans by looking at humans and bonobos and combining the two. It's much easier to have a model to build off of then trying to plug in all the unknowns I mentioned in my first answer. Just extrapolate a human from a bonobo. Take bonobos, make them smarter, make them a little taller and mostly hairless (this are inevitable evolutionary side effects of freeing the hands up on the savanah), and go from there.
Now the potential downside. Bonobo are refereed to as the hippy apes, because they like to make love not war...lots of love. Bonobo's have made sex a social communication. They use it to develop friendships and bonds, like how chimps groom each other, and to show alliances. They use it to make up after fights, or to calm upset third parties or are upset. They use it when disputes over resources would come to first calm tensions and help decide who gets what resources (the girls seem to end up with the resources this way lol). It's a reward or exchange for services rendered. It's part of how their society functions.
They also have sex in any way you can imagine. With any sex, or age, and most sexual positions. The males engage in "penis fencing" and girls usually settle for simple "GG rubbing" (genital to genital) along with most other sexual positions humans do.
From an evolutionary standpoint this works by removing the males ability to know who the father is and encouraging males to play nice because those that play nice get more sex; and ultimately it evolved because their forward hip walking position makes rape much easier and thus the girls had to form a society to repress male aggression and encourage a different avenue to the whole rape one.
You may not like this focus on sex since it could sidetrack from the story you want to tell. There is an easy fix to that though. This level of sexual contact simply can't keep up if bonobos reached human levels of society due to STDs. Once they were living in large enough communities (ie once they had discovered farming to support larger communities) the risk of STD plagues would be huge. You can say the bonobo-humans had to give up the extensive sexual contact due to STD concerns as their numbers swelled; but this happened late in their evolution, after they had discovered the benefits of peaceful resolutions for larger community building. They evolved to replace sex with some other calming gestures, things like hugs and kisses, but which would feel more relaxing and peaceful to them then us even if done with strangers. That way you can keep all the benefits to using bonobo without having to get too sidetracked by their unique practices.
[Answer]
First, Garen is right and I stand by all he said...
Of course I assume you weren't committed to that exact length of time and would be open to traveling further back in time?
Now then..the rest of this is going to be flow of thought trying to tackle what at first seemed an impossible question so ...not sure what your going to get.
This is still a very difficult question to answer because well...evolution isn't magic, it's a result of creatures living and dying based off of their fitness and random mutations. Real life and science drives this, what a magic "evolution-guiding spirits" would do is hard to fathom to me, and I can't give a scientific answer that starts with a magic premise.
So first, lets try to better define the evolution guiding spirits. I can see two things that these spirits could do:
1. Encourage specific mutations to occur which help move towards the ultimate goal
2. Do not encourage specific mutations, but instead add to existing evolutionary pressures. It doesn't make mutations happen, but it ensures those that walk or speak are *even more* likely to survive then those that aren't
These could both work. option 1. would be a *much* faster evolutionary route. However it has two big problems. First, you said the spirits can't be omnipotent, but being able to figure out what adaptations will lead to the desired goal is pretty omnipotent, it almost obligates a long term path of per-planned evolution, since there are so many tiny adaptations that need to build off of each other to get anything like what we want. Second, if you allow this kind of control I can't tell you what humans will be like or how they would differ, because we now have walked away from evolution into genetic manipulation and you can do whatever you want with that.
Thus lets focus on option 2. All the spirits do is help make sure that those that meet the desired goals manage to spread their genetics better. This could work in many ways, protecting those things that stand up or speak from predators, helping make the men more potent (in a fertility sense) and the women's pregnancy and delivery easier/safer, or simply hinder or kill those that fail to meet it's standards.
Option two could still accelerate evolution, but in an odd way. For a long time you wouldn't have any mutation that support your stated goal, then one day something would come along and only then would the spirits start working to encourage it. When you have mutations they would 'win' faster. This is an advantage, many useful mutations likely die out because even though that ape was born with an extra 12 IQ points because he got a smart gene he was still eaten by a leopard while still a newborn when his mother looked the other way, or he managed to fall out of a tree when he had the bad luck of grabbing a weak branch, or he happened to be ugly and the girl apps just weren't interested. The point is even if a mutation is an advantage it still shows up in a single individual who can still easily die before he passes the mutation, the majority of beneficial mutations were lost to random luck of death of the original mutant or the rest of it's genetic line before the mutation managed to pass on to the larger population. Protecting 'good' mutations so they can be passed on would be useful.
So what we get now is a few times of more rapid evolution followed by large spans of the same-old same-old evolution when there is no mutation to 'encourage'.
The result of this would...most likely be humans evolving slower actually.... The problem is that mutations need to build off of other useful mutations. For example, much of our intellect was only useful once we had hands to manipulate tools. Without the ability to finely manipulate tools much of our brain power is less useful, and calorically expensive. Those big brains could be a hindrance to survival without hands. Now if we had some spirits which came around and went out of their way to encourage the abstract thought skills required for tool use while we still had hooves we would all be more prone to starving to death (because brains are expensive) without getting too much use out of it; which would just handicap us.
So lets presume your spirits are a little smarter. They have a general idea of what came before what and only encourage certain steps at a time. Upright posture comes before speech which comes before certain more advanced thought processes etc.
So what would be some difference?
I can see one right off potentially, it's always bothered me a little that we survived so well when we first started to leave treas and travel upright along open plans. We didn't have much in way of tools to defend ourselves, we could not run very fast, and we likely were not that strong. The right predators would have found us a very easy food source before we had more sophisticated weapons. Now we really didn't travel in full plans until we were pretty evolved, the savannas were not exactly what our early evolutionary homes looked like, but still. Perhaps that's because we had some magic spirits protecting us from predators until we could evolve enough to defend against them. Perhaps slow-rate humans had to evolve better defense strategies against predators when away from trees before they finally figured out the whole stone tool thing. Maybe they are physically stronger or more intimidating because of this?
Also, childbirth is harder due to our upright posture, we are one of the species that has the hardest child-birth (though no where as bad as the hyenas thankfully, giving birth out of something refereed to as a pseudo-penis can't sound fun to anyone). Potentially the slow-humans have easier childbirth because they weren't rushed to an upright posture. This in turn could affect other things, like allowing females to conceive younger, decreasing overall death rates, which in turn my minutely drop the fertility rate of the humans (since they still want about the same population density). Honestly this affect alone could play allot of small but interesting roles in mating, sexual conflict, and eventual gender roles; but there all individual small so I won't get to side tracked on them.
Slow-humans (slow-mans? sloans?) would have had to develop language over a longer time which would only happy through social interaction. This would suggest a few things to me. First, they may have developed some other not-quite-language communication methods before full language and syntax existed as an intermediary, meaning they may have more universal body language, jesters, and even sounds that have meaning without abstract syntax modifying it; things we used to communicate before true language that still carried over.
This would also mean that humans would have had to live in packs for a longer length of time to develop language. More reason to stick in a large pack without language would be needed, easiest way to go here would be that they stuck in a pack to defend against predation.
Contrary to the implication of your question though living together for longer does not make us more civilized. Social language evolved because there was an evolutionary pressure to have it, a pressure that comes from social conflict. In other words we must have had social conflict to learn to speak, and if we assume slow-humans had a header time developing language then we would have to assume that they needed stronger social pressures to make it happen. In other words they likely had allot more social conflicts, battles over mating rights, social hierarchies, allegiances, trading of favors etc etc. They would need more bickering to finally cause language to evolve, and thus even after language may very well be more prone to bickering. Since that seems to go counter to the point of view you want I'm going to suggest you go the 'bonobo route' which I'll discuss later if you don't like this idea.
The focus on evolving tool-making intellect may potentially have driven out other instinctual skills as well. Perhaps slow-humans are better at institutionally telling things about the world that would have helped them before tools, like anticipating weather, sense of direction and navigation etc.
Beyond the obvious things above the truth is that evolution has allot of random luck in it, which could be twisted around in all kinds of ways. For instance eye and hair color is (mostly) random with little effect on evolution, more so for Caucasians (African people have darker everything due to an actual need to resist higher UV exposure). In fact much of the hair on our body could have been different, it's quite possible slow-humans would have no hair at all to avoid parasites. Left handers could easily be more common then right. Much of the smaller aspects of our physical features could be shifted or adjusted one way or another, such that slow-humans may have an uncanny-valley effect of looking close enough to humans to seem very wrong to us because their features evolved differently.
It's easy to have certain sexually linked traits in slow-humans that didn't exist in ours as well, many of them are little more then random fluke followed by a feedback chain encouraging them. Maybe slow-humans found bright hair color in mails to be sexy and it evolved like a peacock tail as a way for a male to prove physical fitness; these "handicap principle" adaptations really are random, anything could be used as a handicap and thus slow-humans could theoretically have evolved any number of unique traits if they went this route.
To address some of your specific examples though:
Genetic 'disease' would be just as common. Most of these supposed 'diseases' were advantageous *very* recently in our history. sickle cell anemia protected against malaria. Cystic Fibrosis protects against many diseases that cause Direha, like cholera, and also defends against tuberculosis. I could go on, but many of them *were* useful traits or they wouldn't have become so common (usually to combat diseases, the biggest bane of humans once we got past stone tools). More to the point, due to the fact that they are recessive it's nearly impossible to 'get rid' of these traits once they exist, short of excessive inbreeding which I don't recommend, because there will always be carriers of them that are not sick themselves.
The appendix will still be around, it is not vestigial like we once thought. It helps aid in the immune response. For that matter male nipples will always be around, don't believe me? male dogs have nipples, male cats too. most males of mammal species have nipples. That's because we use 99% of the blueprints females have, and it's much easier to evolve a "only make this grow bigger if you see this hormone" gene then a "don't make this grow at all" hormone. Most of the traits of female and males use the same body parts, the clitoris, for example, is effectively an unperformed penis. It's nearly impossible for them to evolve away because they are useful for one sex, and hardly do harm to the other, so there is little advantage to messing with them. The pinky would be unlikely to become vestigial either, adaptations to make it more useful are more likely to show up then ones to remove it, and in general *more* flexibility in the hands is always preferable to less.
All the above is unlikely to happen partially because evolution isn't that thought out. If something doesn't hurt us it sticks around, for better or worse we keep things forever once they evolve.
They won't magically be less aggressive just because they evolved longer, nothing says evolution leads to less aggression at all. Aggression to a point is required to survive as individual or species, and the length of time a society advanced enough to punish aggression has existed in either scenario is too tiny from evolutionary standpoint to matter (that level of complexity can only exist only after your 'spirits' had almost finished their work, it wasn't accelerated through even with spirits). If you want less aggression go with the bonobo solution.
less simian appearance is potentially possible, but that goes in to my comment that general physical appearance could be adjusted in many minor ways since a good bit of it has a degree of chance and luck to it.
I'm going to post a second post with Bonobo option, having stumbled around the general concept and explored it here, since I don't think any of these answers are too exact, but it's hard to be exact. I will simply end this by saying that the truth is the two humans would likely be fairly different if only the traits you listed were selected for; but there is so much room for unknowns as to how their different, I can't say what slow humans would be like, only what areas may be different; evolution could have gone in so many paths. Their very psychology and view of the world could be quite different as well.
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I think the Lazy God may have done better then the normal humans without immortal help. In fact I think the normal humans might be struggling to be on top of the food chain. Human imperfections have kept as alive or on top since we were living in caves.
1. Without craving fat foods our brains will not have developed nearly as well as they did with the extra energy that the fat foods provide.
2. Alcoholism is a problem for millions of people but it was one of the main reasons people started to live in villages - to have enough wheat to make beer.
3. Even bad hygiene habits caused us to rid our fur and therefore we know less prone to diseases that attack monkeys and gorillas.
4. And finally gossip helped because more people could hunt and live together compared to other species.
Unfortunately laziness probably didn't help US get anywhere but it may have let the Lazy God win.
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This is not a *direct* answer to your question, but this **will** let you decide what you are talking about and how fast (or slow) you want human evolution to be and what would be the resultant forms.
# [Sahelanthropus](https://en.wikipedia.org/wiki/Sahelanthropus)
First known hominid. Braincase only 320 cubic cm. No forehead. Jaws protruding forward a lot. Posture is not understood completely but it was most certainly not erect.
[](https://i.stack.imgur.com/xXPgT.jpg)
# [Orrorin](https://en.wikipedia.org/wiki/Orrorin)
Able to walk bipedally for some distances. Height probably ~3.5 ft. Still liked living in tree branches and had prehensile feet. Looked very much like Sahelanthropus, but shows signs of a forehead.
[](https://i.stack.imgur.com/MGL7T.gif)
# [Ardipithecus](http://en.wikipedia.org/wiki/Ardipithecus)
Beginning to settle on the ground and quitting the trees. Posture was bipedal but not erect yet. Height ~4 ft. Were getting to be social creatures. Size of canines suggests males were not as aggressive as those of Sahelanthropus or Orrorin. Brain size ~500 cubic cm. Height ~4.5 ft.
[](https://i.stack.imgur.com/hQDtw.jpg)
# [Australopithecus](https://en.wikipedia.org/wiki/Australopithecus)
Gradual increase in brain size to 950 (primitive humans) cubic cm. Evolution of complete erect stance and fingerprinted fingertips. Height increment from 4.5 to 5 ft.
[](https://i.stack.imgur.com/i01GL.jpg)
The last stage is us, homo sapiens.
Sahelanthropus fossils date back to ~7 million years ago while modern humans appears 198000 years ago. If evolution was slower, you should choose traits from the primitive genera stated here and maybe mix/match them for added effects.
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I'm working on a far-future SF story taking place on a terraformed Mars and would like a fact check. Current estimates (see [here](http://www.users.globalnet.co.uk/~mfogg/zubrin.htm) and [here](https://en.wikipedia.org/wiki/Terraforming_of_Mars)) are that the CO2 on Mars could be released in gas form to warm the planet and raise the atmospheric pressure to about 30% of earth, which is not breathable but is sufficient pressure to not be lethal (about Mt. Everest level).
Assuming the oxygen content can be increased (through some technological means separating CO2 into carbon and oxygen), would a higher proportion of oxygen at low pressure allow a human to breath it? It would certainly be thin, but athletes who climb mountains find their bodies increasing red blood cell count to more effectively capture oxygen. Is Everest-level pressure just too thin even if the percentage of oxygen were higher than Earths (about 21% of air)?
I'm assuming that things like the solar wind stripping away atmosphere due to lack of a magnetic field have been taken care of. The limiting factors are Martian gravity and air pressure and content. I'm also assuming no extra mass (gas or otherwise) has been imported from elsewhere and we are working solely with what Mars has to offer.
I'm aware of [this question](https://worldbuilding.stackexchange.com/questions/4147/what-can-we-do-to-mars-to-give-it-a-survivable-atmosphere) about giving Mars a survivable atmosphere, but the accepted answer claims that atmospheric pressure would be limited by gravity without explaining why Titan, which has gravity 14% of Earth, is able to sustain a mostly nitrogen atmosphere at higher pressure than Earth.
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Yes. You'll need to have a much higher percentage of oxygen in the atmosphere. The key is the O2 pressure being within the acceptable range. Early space craft used environments with lower overall pressure but near pure oxygen.
But, just putting the O2 in there does not make it breathable You still need have acceptable levels of CO2, for example, as too much is deadly. Also, very high levels of oxygen may introduce other problems.
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**If this is far-future and the atmospheric stripping has been solved, then you can do whatever you want.** Solving the atmospheric stripping will require inducing a stronger magnetic core in Mars involving gigatons of metal or some kind of shield has been placed between Mars and the sun to prevent the solar wind from doing it's thing. Either solution involves engineering skill and power sources far far beyond what we have now.
With this kind of advanced tech, separating CO2 into carbon and oxygen should be easy. Nuclear reactors could be tasked with this kind of processing. If a "lower tech" solution is required, plants able to operate at the atmospheric pressures and CO2 densities cited in those two articles could easily begin the process of converting CO2 to O2.
== Edit ==
The pressure itself is going to be a problem. From this [atmospheric pressure calculator](http://www.mide.com/products/slamstick/air-pressure-altitude-calculator.php) at 0.3 of surface pressure, the altitude is just under 30,000 ft. While it's possible that a human could survive at that altitude, they're not going to be comfortable there and extended exposure is going to cause all kinds of oxygen deprivation induced damage. At those altitudes/pressures, there just isn't enough oxygen around for the body to use. Certainly, the FAA recommends using [supplemental oxygen](http://www.aopa.org/Pilot-Resources/PIC-archive/Pilot-and-Passenger-Physiology/Oxygen-Use-in-Aviation) for all passengers above 14,000 feet.
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> There may be the same [ratio] of [nitrogen]/oxygen molecules at 20,000 feet as there are at sea level, but because of reduced partial pressure, those molecules are spaced farther apart. Consequently, the partial pressure of oxygen in the bloodstream is significantly reduced; so there's not enough pressure to allow the oxygen to force its way into the blood, and you can't breathe deeply or fast enough to compensate.
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The best method to convert CO2 into oxygen is ... by photosynthesis. It costs nothing, is maintenance-free and goes on automatically. But for this to occur, you would need to add ***lots*** of carbon in Mars' crust.
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You would basically have a pure oxygen atmosphere as you have low total pressure and need most of that pressure for the oxygen partial pressure. That would be very dangerous as pure oxygen (even at lower pressures) makes things highly flammable - see the Apollo 1 disaster. You need a buffer gas like nitrogen, and there isn't a lot of nitrogen on Mars.
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We are creating a world of floating islands, these vary in size from small outposts that are little more than a Dock and Watchtower, through independent farmsteads, to full Nations in which the majority of the population are unaware they are on a floating island.
A particular Nation has access to "magic" but it is treated as science as it is technically unlawful, so if it is quantifiable or repeatable it becomes allowed, but summoning a Demon to ask for directions would not be acceptable. They have developed Airship technology, and Ornithopters, and would be typically "human". The power is held by Universities and Guilds rather than a Feudal state.
In the rest of the world pretty much anything goes, so there are Pegasi, Goblin Hanggliders, Sky Whales etc...
The atmosphere is Earthlike, so high is cold and hard to breathe and low is hot and hard to breathe. There are winds that could be predictable. Birds are around. Clouds form and block visibility so you may not have 100% visibility. There is a celestial globe of stars and other objects that can be observed and measured.
Considerations from our Earth:
* Islands in the Pacific Ocean can be identified by how they disrupt
the wave patterns
* You can follow Trade Winds to find entire
continents and return to your own continent, can you do the same to
an island
* Altimeters use Air Pressure but are periodically zeroed
at known heights/location
* You can measure speed via a log
* A compass can be used to give the direction to a known/assumed point
* Devices can be used to measure angles for celestial bodies
* Maps can be a list of distances and directions
* Maps can be a representation of the area in pictographic form
* Data can be pre-calculated and recorded in books of look-up tables; calculations, tides etc...
How would this nation that is self-limiting to technological methods map and navigate through 3D space? Would there be a way to do it if there was no compass?
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The best way would probably be to use a sextant. As long as you can see celestial bodies/the sun, you can navigate yourself to within [half a mile](http://www.cs.yorku.ca/~amana/personal/navigation/). This is great for a 2D world, but adding in the 3rd dimension, you'd likely use an altimeter/barometer to determine your height as well. Coordinates would be 3 dimensional (latitude, longitude, and elevation).
You'd probably want a compass, but you wouldn't need it. As long as someone had a sextant, they can just note where they are now, and where they are in a few minutes, and get a direction of travel.
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Celestial navigation is *quite* useful -- 1 NM accuracy 95% of the time (RNAV 1 in modern parlance) will get you close enough to your destination to find it and land there basically every time. However, it's not the *only* thing your aviators need.
## Up? What's Up? Where's Up? WHERE IS UP!?!??!?!
Land creatures typically are given stabilizing systems that are designed for two-dimensional motion on a surface -- our inner ears are quite good at it. However, they aren't so good at ascertaining balance in a three-dimensional environment, especially when visual cues go away. Hence, some form of gyroscopic instrument would be needed in addition to the obligatory altimeter, compass, and airspeed indicator. At minimum, a simple one-axis gyro can be used in a system akin to "needle, ball, and airspeed" flying; however, two-axis gyros aka attitude indicators make the lives of your blind-flyers much easier.
## Finding Your Way Through the Clouds and Fog
A prime drawback to celestial navigation is that you can't use it when you're in the middle of a big, fat cloud or fogbank. Some sort of system based on beacons (similar to today's radiobeacons such as VORs and NDBs) would be needed in order to let people at least find the nearest island and wait out the weather, if not navigate beacon-to-beacon in a fashion similar to modern air navigation.
## Getting down to land
It could easily happen that one of your floating islands would become enshrouded in a cloud. Landing in that case would require something more sophisticated than a mere beacon to guide your aviators to the right spot at the right altitude -- the concepts behind an Instrument Landing System (using focused, crossed beams to provide azimuth and elevation guidance to the landing site) could be used to allow for safe landings in all weather.
## Lights, Action!
Of course, lights can also be used to provide visual aids in night and even to some degree bad weather, similar to lighthouses in the naval world.
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They can place lighthouses on islands. On the Earth surface limits the range of lighthouse to be seen:
[](https://i.stack.imgur.com/HSZRg.jpg)
In the sky, the range can be much more bigger, and is only limited by air transparency.
They can use some sort of bells and buzzers for audible navigation in foggy weather, and every airship has a special crew member - Listener, who determines the direction and range to near buzzers.
The air attenuates sound of high frequencies more, than sound of low frequency (Sorry, i don't remember this physics law name ;-( ).
So, distant buzzers sound with more bass. If all buzzers use standard frequency, Listener can determine distance by change of tone of sound.
The Listeners use gadgets like this:
[](https://i.stack.imgur.com/m0Bbg.jpg)
Also every island has Listeners, that find approaching airships to notify watchmen:
[](https://i.stack.imgur.com/jExfN.gif)
(In real life this gadgets was used in World War 2 to find approaching aircraft's and guide anti-air cannons.)
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Actually I think it would be easier to navigate if you constantly have landmarks visible from long distances. Who needs a compass when the Hohenberg's island to the north is visible for miles, even through the forests? That is how much of navigation was done. The stars became useful on open expanses such as the oceans where there are few to no landmarks over much of it.
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Picture this: there is a high fantasy world with a majority of humans, but in recent times there have been other, monster based species gaining traction (i.e werewolves, naga, harpies). In this current environment, we have our villain, a Dracula-esque, supernatural corrupt noble who has magical power at their fingertips and essentially wants to build a base of power.
Now if your first thought from my question was Castlevania, you'd be correct. I always wondered how exactly so many variety of creatures came under Dracula's castle, and why they were willing to work together, at least long enough to impede the hero, rather than getting at each other's throats due to cultural differences. However, my goal isn't to ape Castlevania entirely, as the focal figure wouldn't be Dracula, nor share his same motivations or even species.
As far as magical limitations go in this world I have, mana is best produced through living beings, though any solid object can contain it. The more magic cast by volume, the more mana it depletes, so large scale magic either requires a lot of people, an artifact of densely packed magic or someone of massive size. Draining magic through the same target over a longer period of time grants more magic than draining them to death, unless there needs to be a lot of magic in a very short time (e.g holding open a dimensional rift).
Assume that this figure is a relatively powerful humanoid but not human. They are long lived enough to know a variety of spells, have a hardier body than the average mage, relatively attractive and have plenty of charisma, and does not need to worry about aging. If not killed correctly they will revive in a short time or will even reincarnate. A combination of pragmatism and xenophilia prevents them from being downright heartless, but they are willing to stir any level of mayhem to get what they want, whether it is new minions or to assess the character of anyone they deem interesting or a threat.
As for the castle, assume that it is essentially a 'living being' that absorbs magic from its residents in turn for offering protection in order to maintain itself.
What would the villain need to both create this castle and provide for their minions in order to follow them and work to further expand said villain's influence?
EDIT: to narrow the focus so I have an objective question, I can add the following details:
* The castle itself should initially be large enough to house about 200 humanoids, with room to expand. The villain will naturally prefer a high but not too high spot, like a low mountain, cliffside, or large enough hill with good moonlight.
* The castle walls should be able to withstand most high level spells, so in case an angry calvary notices and attempts to attack, they would not have any luck.
* The castle should look appropriately spooky and strange, especially at night. Aside from the gothic tones from Castlevania, I'm willing to experiment with other styles, like how [Great Zimbabwe](https://en.wikipedia.org/wiki/Great_Zimbabwe) was built, or even a blending of said styles.
* The castle should be able to house a variety of environments for humanoids. Rooms can be lined with magic to mimic environments that aren't possible in the local area (like deserts or areas of extreme cold).
* Not refined yet on my end, but there are metals that store elemental energy (fire, water, earth, wind, light and darkness; first four more common than the last two) better than known metals here. They can be blended, with certain exceptions that oppose each other (light and darkness, fire and water).
* A minor side note: non-magic technology is closer to early 1900s America, and indoor plumbing would be a possibility for this castle, cities, and rural nobility.
* Just like Castlevania, this castle is a 'creature of chaos'--i.e, living being that can change itself. Unlike Castlevania, it did/does not start off at castle size, buildings and/or materials are needed to be added before it can maintain its size and change it however it wants. For this exercise lets say it starts off the size of a two story house, with a shrine that holds the creature's 'heart'.
I recognize that some of these aren't realistically possible, but the hero of this story studies magic and how artifacts are put together, so I would like something that could be consistent and more than 'the castle was magicked into existence'. What materials should the villain get, and who would they need cooperation from?
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A villain of this capacity (a long, near immortal, life) has a unique flaw that will help define the how and why of his castle and minions; intense boredom. The ultimate solution to this is, of course, humans. This castle is only one part of this creatures mechanism of entertainment with the town in it's shadow central to the control of the minions and the relief of his boredom.
Having already lived a long life full of seducing the rich and powerful, killing them and pilfering their most treasured and potent magical items, your villain, tired of always having to flee, looks for a place to settle down. They locate a small fiefdom with a pretty castle on a mountain with a nice little town below.
Posing as a travelling curio merchant selling 'cures' for various illness will provide a simple way to get into the lords favor (poison member of family a few days before they 'arrive' and offer cure. Gifts of cursed jewelry should provide an invisible way to turn and control the lord and his family members as the castle is slowly twisted into a bastion of fear.
Meanwhile his work in the town below is not done. Anyone with any influence and intelligence is quickly isolated and removed from the town but at the same time the every day folk of the town find fortune on their side; crops are bountiful, livestock healthy, their families healthy and large, all influenced by the various magical trinkets provided by our curio merchant.
The town booms and the castle darkens.Using the lord and his family as proxy he lures various lower level necromancers and other dark magic users to the castle, bribing them with items from his collection, allowing them to twist the castle further to their needs.They will of course bring and create their own minions. Their motivation is the thriving town below full of resources, the protection of the warped castle and the shear number of magic and evil entities that call it home.
The castle is now a twisting evil hulk constantly torn from within from the experimental magic of it's insane occupants. It's halls and dungeons inhabited with escaped magical creatures and tormented experiments. Some of which will of course find their way out of the castle into the surrounding area and even into the outskirts of the town.
Having built his influence in the now terrified but highly successful town the villain now finishes his master plan. He declares the town independent of the lord (who now openly terrifies the town) and announces that he personally will fund a protective wall (or magical device) for the town and fund a regiment of guards for protection (corrupt of course but not necessarily evil) and builds himself a manor and shop front right in the middle of town.
Now as one of the most respected merchants in town (one of the first any adventuring types will visit should they wish to assault the castle) he can feed information to the lord on any incoming threats (as long as the castle and the lord stand he is completely invisible) and is free to mess with the lives of the towns inhabitants with blame conveniently landing on the castle and it's horrors (as a fair number of the disappearing people would be taken by the lord and his corrupted knights/house guests).
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Alright I'll take a brief crack at this multi-faceted question.
You're right in saying any villain needs to provide a reason for his minions to stick around. The villains are probably motivated by the same things his master is, they just may or may not want to be in charge of it. So Dracul-esque's biggest appeal is the power he could achieve through cooperation.
Given these criteria, I would have to say your villain needs to be able to make promises to a lot of people. In a gang, or even the United States congress for that matter, people need to be able to trade favors. So your villain needs to make promises, but ALSO be intimidating enough to make others believe he can and will keep those promises whenever he ends up winning his conflict with the hero.
Maybe he will provide land for the werewolves to roam, or thralls to other vampires, or sacrificial victims to the Aztec warriors if that's the case. If they want these things they will cooperate and your villain can always threaten to kick them out of the club if they don't cooperate with each other.
As for building a magical castle...
That can be easy or hard.
Easy: You have a gang of villains and supposedly a bunch of land they feel comfortable building HQ on. So what's keeping them from using slave labor to build the castle and use the slave life energy to infuse the castle with magic? You could mark it as the bloodiest construction zone in the history of the world.
Hard: If the gang builds the castle themselves, who is designing the castle? Who is doing the labor? Who sets the schedule? And why would they want to put in the physical labor themselves? It would seem a lot harder to convince a bunch of magical thugs to build something like a castle than to simply participate in the overall plot. But maybe this turns into a team-building exercise? Or all the werewolves get pegged for labor duty and become disgruntled employees.
Hope this helps!
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One possibility is to make it that magical creatures of all types need to feed off of mana to exist. Any place that is saturated with mana will therefore tend to attract magical creatures naturally.
Mana can be powered by society's belief in magic. The archmage could have began as an ordinary (politically powerful) human, who acquired enough notoriety that people began attributing magical powers to them. This caused them to accumulate mana and gain increasingly stronger magical powers, which also enabled their castle to attain magical qualities as people began attributing magical qualities to it as well. Of course, since magic is now happening around them that would further reinforce the belief of the people, gaining the archmage even more power over time.
With all this magic accumulating in one place, monsters and spirits would be drawn to the castle from miles around, eager to maintain their own existence by feeding off of it. Since it is ultimately powered by the archmage (or rather, by the people's belief in and fear of the archmage), he can ask whatever he wants from the monsters and they have no choice but to obey. Without the archmage's power bringing it together, it would simply degenerate into an ordinary haunted house.
This would also explain why the castle needs to have a spooky aesthetic, and why it has to be in sight of ordinary humans. It is the fear humans have of the castle that ultimately gives it its power. The archmage has to maintain a delicate balance of striking fear into the hearts of the villagers so they continue to believe in him, but also give them enough leeway that they don't start sending whip-wielding vampire hunters after him.
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I once had an idea similar to that in IndigoFenix's response: magic that went off something's nature and/or the meaning ascribed to it. For example, this magic if it went into a figurine would turn that figurine into a magical glass/stone/plastic version of what it's *meant to represent.* In other words, this magic derives its power from *symbolism,* that additional meaning an object or concept represents and makes it real, if not literal.
Rumors of an immortal dungeon keeper are untrue; he was simply one among a line of lookalike dungeon keepers, but thanks to his arcane knowledge, he used this Clarkian/symbolic magic to *become* immortal (ie. applied the status ascribed to him). Then he pictured the idea of "coming to the light," the symbolism of that, and used his magic to set off a chain reaction.
As a result, his dungeon became a spooky castle on a nearby small mountain, which overlooks the town. First, he creates a field of symbolism magic around his castle and the town's boundaries and has servants spread propaganda about how the town is *the* place to be, full of opportunities and prosperity. Because of that magic, the town becomes a bustling metropolis, a paradisiacal place.
As the town grows more and more enchanting, the castle grows darker and uglier by contrast, which of course fuels spells on the castle, making his dungeon bigger and more fearsome. Since creating any work of art means figuratively "putting a piece of yourself into it," the symbolic magic can turn replicas of mythical creatures into real mythical creatures at the cost of some of his life force (which, since he's immortal, is constantly regenerating).
Because these creatures are "born" of the dungeon keeper, they will feel obligated to obey him, and since the concept behind them is what they become, the dungeon keeper can easily make them eternally loyal to him. Better yet, he can *always* make more. If the keeper tells the monsters they'll grow more powerful as they gain experience, evolving into a more powerful monster at a certain experience level, the *magic will make it happen.*
Through this symbolism magic, powerful if applied with enough creativity, a dungeon keeper can easily solve his boredom problems and cause otherwise impossible supernatural effects: an ever-shifting labyrinth that's almost impossible *not* to get lost in, adventurers dying and being reborn as monsters (zombies, manticores, and what have you)....the possibilities are pretty much limitless.
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I am trying to create a planet that rains acid, and that has acidic oceans of water, but a breathable nitrogen-oxygen atmosphere.
This planet has native lifeforms that have evolved to withstand these acid rains and that have perfectly adapted to the acidic oceans.
Maybe the acid rain could be produced by volcanism, or the life on this planet somehow creates the acids in the form of waste or by expelling them. What type of acid could we be seeing here?
The air doesn't have to be fully breathable, maybe we could use filter masks to protect from harmful acid gas.
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**Short answer: Volcanic eruptions or nitric acid breathing by animals/funghi might be the best way to go.**
I'm assuming you mean a pH of 0-2, this is would be really acidic. For this, a strong acid gas is needed. It must be a gas to cause acid rain and it must be created in the atmosphere/on land, not in the oceans because there it would react immediately with the water, leading to acidic oceans but not to acid rain. In the atmosphere the acidic gas would react with water and cause acidic rain. There are 3 common (and a lot less common) acid gasses.
**Sulphuric acid (H2SO4)** is quite common in volcanic eruptions leading to acid rain here on earth from time to time. Sulfur doesn't really play a major role in land biology (quantitatively), so there is no good reason why it would be mass-produced by land organisms.
**Nitric acid (HNO3)** contains nitrogen. Nitrogen is way too valuable for any primary producer (plants, some bacteria) to be emitted into the atmosphere, but heterotrophic organisms (animals,funghi) need to get rid of nitrogen. Animals usually do this by excreting it in a solution (e.g. urine), but I guess it would not be completely implausible to get rid of it by breathing out HNO3 just like they get rid of carbon with breathing out CO2.
**Hydrochloric acid (HCl)** contains chlorine. This is generally abundant in the ocean, but it requires a lot of enery to create HCl from it. I could imagine some plants at the coast (some sort of mangroves) that use some sort of biogenic electrolysis to get minerals from the seawater and create HCl in the process as waste-product. Although this would hardly be enough to create enough of it to alter the atmosphere significantly.
All of this gases are high-energy compounds, so organisms need a good reason to use energy on it, e.g. because they need to get rid of a waste-product, just like oxygen. The most plausible is probably the sulfuric acid by volcanic eruptions. The least implausible biogenic explanation is probably the breathing of nitric acids by heterotrophs. While the volcanic eruptions are a relatively solid explanation, the nitric acid breathing is speculative.
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Sulfuric acid in rain has been severe enough to damage marble building facades and artworks exposed to the weather, when coal burning was widespread and sulfur reduction wasn't yet available in the 19th and 20th centuries.
All that would be needed for this to be a "natural" problem is for lightning to ignite exposed coal seams (as is believed to be the case with the burning coal seam in North Dakota, which was already alight when the first settlers reached the region and was still burning as recently as a few years ago) over a significant area; soft coal, especially, tends to be high in sulfur and the combustion products will react with moisture in the air to produce sulfuric acid.
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Earth has three convection cells per hemisphere, resulting in each hemisphere having a band of desert at the end of the Hadley cells.
Given a planet with the following characteristics:
* Twice the radius of Earth.
* Rotates every 24 hours. (So the linear velocity of rotation is doubled, but the angular velocity is unchanged.)
* Gravity is 1g (achieved by some means out of the scope of this question).
* All other characteristics like atmospheric composition are the same as Earth.
Would it still have three cells per hemisphere, or more? Everyone seems to agree faster rotation with constant radius would increase the number of cells, but is it the linear or angular speed that matters?
The best answer I have been able to find on that is <https://earthscience.stackexchange.com/questions/992/what-factors-determine-the-number-of-hadley-cells-for-a-planet> and while it's not clear what the symbols in the answer mean, it does seem to say that increased radius holding all else constant, does increase the number of cells. Some sources also seem to argue that one of the causes for air sinking at the edge of the Hadley cells is Coriolis force imparting sideways momentum; I'm not clear why that would cause it to sink, but if it does, that would also support the conclusion of proportionality to planet radius. If it's a matter of having time to radiate energy away to space so as to get cold enough to sink, this would also support the conclusion.
There does seem to be a consensus that the number of cells per hemisphere must be odd. So if it's not 3, the next candidate is 5.
Does that mean that on the planet with the above parameters, each hemisphere will have two bands of desert (at the latitude where air descends and warms up)? So, a band of hot desert, a band of cold desert, with a band of wet climate in between?
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### About winds and cells
A rotating planet with an atmosphere has 3 types of cells per hemisphere:
* Hadley cells around the equator: sun warms hot air that raises and - in the north hemisphere - moves north while cooling. As it moves north, it also moves east due to kinetic energy. Indeed, consider that stable air at the equator moves with the planet, so it has a given linear velocity. As it moves north, the linear velocity to stay in place (zero speed relative to ground) is *reduced* because circumference of the planet is reduced. As a consequence, airmasses moves east to dissipate their kinetic energy.
* Polar cells, where air cools down at the pole and - still in north hemisphere - goes south (no choice, you are at the pole) with no kinetic energy, so it lags behind the rotating planet, making it moves to the west.
* Ferrel cells, a secondary or indirect type of cell appearing between the primary ones that are the Hadley and polar cells.
Let's call *Bambam* the proposed planet with twice the radius of Earth as main difference, other elements remaining the same, including energy received from the sun (this one impact the quantity of air raising at the equator). On Bambam, the winds at the equator will have double linear speed so quadruple amount of energy ($E\_{c}=\frac{1}{2}mV^2$). Assuming air cools down at the same speed, it will need the same linear distance, so half the radial distance or latitude. The Hadley cells will not be the double side than Earth's, but probably only slightly so due to the energy levels and friction (got lost in calculation here, but will happily welcome contributions).
In practice, Bambam will have, per hemisphere, the room for two distinct secondary Ferrel cells at the border of the primary Hadley and Polar Cells. Betwee the Ferrel cells is enough space for a third-level turbulence that could be a cell on its own, or maybe multiple smaller ones. As mention, a stable system implies an even number of them to not end up with opposite winds in the same place.
### Deserts
Bambam will likely have cold deserts bordering the polar cells due to the dry cold air. At the border of the Hadley cells, desert presence will heavily depend on ocean distribution, as this changed the amount of water in the hot air. Topography is also a key factor and can on its own create deserts.
For the secondary Ferrel cells, expect even more instability and less features defined only by the cells.
To conclude, Bambam will have multiple secondary-order cells, but those are unlikely to create neat deserts latitudes on their own, topography and ocean playing a key factor here.
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# Prelude
I didn't know what a Hadley cell was until now. For what the Hadley cell is, you might go to Wikipedia.
## Definition
Hadley cells are atmospheric circulation patterns observed between the tropics.
The air rises at the equator, moves towards the poles and then descends in the subtropics.
## How Hadley Cells work
First the air rises at the solar equator, then moves towards the poles, and as at the equator, air is stationary relative to the ground below, it carries the linear speed at the equator to the subtropics, thus sliding pole+eastwards relative to the slower ground.
At the subtropics it reaches a point where it's no longer so hot and it descends.
After descending, it will move along the ground either towards the poles (and forming part of the Ferrel cell) or back towards the equator. As it moves towards the equator, the ground's linear speed will increase (because at the poles you have angular speed but no linear speed, you only rotate around yourself and move 0 km every day; while at the equator you have the maximum linear speed, you move 2*pi*Earth's\_Radius (km) every day) and thus, the wind moves equator+westwards relative to the ground.
### Climatic consequences of the Hadley Cell
As the air at the equator usually is full of humidity, because the Sun warms the seas, lakes and rivers, the vegetation also help keeping the air humid at night. When this humid air ascends at the equator towards higher places, it cools down very fast and also it generates a zone of low atmospheric pressure (at ground level).
When humid air cools down, the water in the air condenses a bit becoming visible as clouds. When clouds are cooled down even more you get rain. If it cools down further you get snow sometimes.
Now, when humid air cools down very fast you have your typical equatorial rains (at the equatorial climate zones).
When the hot, cooled air exits the equatorial zone, it has lost all of it's humidity, and now it will travel all the way to the subtropics, where it descends creating a zone of high atmospheric pressure (at ground level). Also, this air has lost its humidity at the equatorial rainfalls.
In school we learned (I did, at least) that when there was a high pressure zone, it meant a sunny day, and that when there was a low pressure zone it meant a rainy day.
When the air descends in the Hadley cells, you get a desertic climate, because they get constatly sunny days, with no rainy days.
The dry wind goes equatorwards again, dragging with it all the humidity it encounters towards the humid, hot and rainy equator.
#### Seasons and axial tilt consequences
Finally, as Earth's rotation axis is tilted 23.5 degrees, the solar equator (the parallel at which the Sun shines perpendicular to the ground) changes every day, oscilating from north to south on a yearly period. The northenmost parallel where this happens is called the Tropic of Cancer. The southernmost one is called the Tropic of Capricorn.
The axial tilt means that the solar equator is always moving, and thus the updraft air of the Hadley cell will move acordingly, bringing precious rain to places that would otherwise receive none. That is why the main subtropical climates have a dry season (when the Hadley cell's updraft isn't near their latitude) and a wet season (when the Hadley cell's updraft is just over them).
The equatorial climate are a special case because they **always** have the updraft of the Hadley cell over them.
The deserts are areas where there's never an updraft or there's never humidity in the updraft.
## Desert Listing and comprobation
I've made a list of the main (hot) deserts/desert zones in the world and the latitudes between which they are:
* Sahara -> 12ºN - 36ºN
* African Rift -> 4ºS - 3ºN
* Arabian + Iranian + Thar -> 12ºN - 36ºN
* Turkestan -> 36ºN - 53ºN
* Takla-Makan + Gobi + Tibet -> 27ºN - 51ºN
* Australian -> 15ºS - 35ºS
* Atacama -> 4ºS or 8ºS - 32ºS
* North American -> 21ºN - 39ºN
From this list, we can enumerate the reasons why they are deserts:
* Most of them are placed between the paralells 12 to 36. These are the places more **affected by the Hadley cells**: **Sahara, Namib, Kalahari, Arabian, Iranian, Thar, Australian, North American and part of the Atacama desert.**
* Then we have the deserts originated because **they are at the center of their continent**, and if there was ever any humidity in the winds, it has already rained down somewhere else before reaching there. These are: the **Turkestan Desert, the Gobi, the Takla-Makan and the Tibet deserts**.
* Lastly we have the strangest kinds of desert, because they suposedly have no reason to be there, they are just next to the sea. The humidity should be there. Actually there isn't any humidity because the sea has a **cold sea current** that keeps the water cold, and it doesn't let it evaporate. These deserts are: the **Namib and the Atacama deserts**.
# About cells
### Why do they need to go in odd numbers per hemisphere?
The reason they go in odd numbers is because at the solar equator you will always have an updraft, and if your planet's axis is tilted less than 30 degrees, you will always have a downdraft at the poles. to maintain these two conditions you must have 1, 3 or 5 cells.
[](https://i.stack.imgur.com/7qdfq.png)
### About the possibility of more than 3 cells (speculation)
I think that you could get more cells if you tilted your planet's axis to 36 degrees.
With this configuration, you will have the tropics at 36ºN and 36ºS and the polar circles (nearest parallel towards the equator where the sunlight can shine parallel to the ground) will come down to 54ºN and 54ºS.
There will be enough space for a Hadley cell between parallels 0º to 18º, an equatorial Ferrel cell between parallels 18º and 36º, an exchange Amaram cell between parallels 36º to 56º, a polar Ferrel cell between parallels 54º and 72º and a Polar cell between latitudes 72º and 90º.
On the middle of summer and winter, the polar cell may merge with the polar Ferrel cell to originate a turbulent flow similar to the one we can see on Jupiter's poles, and in the middle of autumn and spring there may be a clear differentiation between the Polar cell and the polar Ferrel cell as the hexagon shaped cloud on the pole of Saturn.
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There are a few flying questions lately and this got me thinking. Someone suggested that a centaur might power a plane via a bicycle. I don't think this would work out, since the centaur would be very heavy compared to its power... but what about a small, light creature, with a lot of strength compared to its weight? What about a goblin?
If goblins used man-powered planes... how far could they go?
## Characteristics of Goblins
In this case, I am presuming the following relevant characteristics:
### Size
1. They're small, of course. Let's say about 3.5 to 4 feet tall. This allows you to shrink various aspects of the plane, and should have an exponential improvement on its flight distance
### Weight
2. They're skinny and light, as is popular in most modern depictions. They probably weigh about 20 to 30 pounds, say 25 for simplicity. This reduction in weight should allow you to cut down on the weight of the craft, as well, which could have a significant impact on fuel-efficiency (in this case, goblin-power), and thus total flight distance.
### Strength
3. Compared to their weight, they are immensely strong. I'm not sure what figure to give, to best represent a strength to weight ratio... but as a general estimate, let's say that while they are about a 5th the mass of a 6-foot healthy man, they actually have 40% of the strength. In other words, they're about twice as strong per weight.
### Endurance
4. We'll also say that goblins have more endurance than a human. For simplicity, let's say they can endure twice as long, while putting out twice the power per weight, so theoretically 4x the total energy output per weight per day.
## Craft
I expect the [MIT Daedalus](https://en.wikipedia.org/wiki/MIT_Daedalus) would be the best example to go off of. It has the current record of 115 km in a man-powered flight.
### Multiple Goblins
You don't need to have just one goblin peddler. If the goblins are capable of producing more lift than their weight, then packing 3, 4, or even some ridiculous number like 12 could be considered?
It's possible the question of multiple goblins is too complex, as it gets into the complication of adding in new pilot seats, increasing structural strength, or even lengthening the plane in extreme cases. So, feel free to focus on the question of a single goblin. Extra credit to anyone who works out how multiple goblins can change the distance, of course. Or better yet, the optimal number of goblin-peddlers.
### Assisted Takeoff
Assisted takeoffs, via taking off from a high point, or using a catapult, or whatever else, is allowed. This wasn't the case for the record flight of the Daedalus, where the takeoff had to be manpowered. I'm not sure how much of a difference this will make to distance, but I could imagine it adding on several km.
# Question:
So, using humanoids with these sorts of characteristics... how far could a goblin powered plane go?
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Sailplanes are much, much more influenced by the form of their outer shell than be 20kg more or less payload. A 4 feet goblin would weight as much as many female pilots today... ok maybe even a little less.
The thing is that the plane itself, if it is lightweight and uses wings from today, will be able to carry a goblin or three or a man, it wouldn't make a difference. A sailplane is not powered by an engine, it is powered by thermics. Once it is in the air, and it can stay there for very very long.
The engines help arrive at the destination faster, though.
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Assuming mechanical perfection staying power is probably going to be more important than power-to-weight ratio; humans have incredible stamina, our ancestors used to run prey to death over many miles, sometimes continuing to hound horses and antelope over a period of days until they dropped dead from exhaustion. Goblins are usually depicted as having a high metabolism which requires constant feeding making feats of endurance unlikely.
A lighter, faster vehicle will offset some of the range disadvantages Goblins would have due to lower calorific endurance but quantifying that is awkward to say the least, and when you add the possibility of multi-crewing a vehicle that would only carry one human a final answer becomes impossible. This is especially true because we don't know how far a human flight could have gone in a mechanically perfect vehicle such as Daedalus since the flight was halted by material failure.
Goblin powered aircraft would certainly be more effective on short range runs than their human powered equivalents due to their improved power-to-weight characteristics.
Good question just too many variables left hanging unfortunately.
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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.
Stun-wizards specialize in blinding and deafening opponents at a distance. To do so, they can exert their magical power to manifest a spherical region of vacuum by essentially "telekinetically" pushing air out of the region. When the wizard releases their spell, air rushes back into the space, presumably with a loud "bang".
**How do you calculate the acoustic loudness (in sound pressure, dB) of a sphere of vacuum, with arbitrary radius r, collapsing at a regular atmospheric pressure?**
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The collapse of bubbles on various scales has actually been an area of research for quite some time. Analyses are typically numerical, and rely on something known as the [Rayleigh-Plesset equation](https://en.wikipedia.org/wiki/Rayleigh%E2%80%93Plesset_equation), which tells you how the bubble's radius varies as it oscillates or collapses. If you know the pressure inside the bubble and the pressure far from the bubble, you can adequately predict its collapse by numerically solving the differential equation - you're not going to get an analytic solution in the general case.
Sound waves emitted by oscillating and collapsing bubbles - due to external perturbations - are discussed in Section 7 of [Lauterborn & Kurz (2010)](https://iopscience.iop.org/article/10.1088/0034-4885/73/10/106501/pdf). One of the earliest papers on solving the requisite equations is [Hickling & Plesset (1964)](https://aip.scitation.org/doi/10.1063/1.1711058), which discusses the case of a bubble collapsing (and rebounding) in water. You may find that to be a good starting point. Regrettably, you'll have to carry out the numerical simulations on your own.
Some notes:
* The study of bubbles typically involves bubbles on the centimeter to nanometer scale; beware of assumptions that may become invalid at macroscopic scales.
* Solving the equations should give you the pressure of the shock waves; from there, you'll have to convert to decibels given the pressure of the external medium.
* This is a problem for which there is, unfortunately, no simple (i.e. analytic) solution.
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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.
Considering:
a) A small void-bubble would be relatively harmless
b) A medium sized bubble (enough to surround a person) would be by itself extremely useful in combat, taking away air to breath. The sound effects of it (if any) are secondary.
c) Sound is produced as air molecules move and collide against other molecules, or objects. To produce any sound that is louder than, say, a strong wind, you need a sonic boom, of air molecules moving at sound speed, on 1 atmo of pressure. We are talking of a really, really big bubble, city sized. If a mage can take away the air of an entire city, sound is irrelevant.
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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.
Much easier to stun someone by removing the air from around them for a few seconds.
Pops from collapsing vacuum bubbles are likely to be just that - pops rather than bangs, as they are only driven by 1 atmosphere of pressure. More pressure = louder bang.
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Humans are [diurnal](https://en.wikipedia.org/wiki/Chronotype). We have chemical signals the control our waking and sleeping cycles, we are evolved with good day and color vision, poor night vision and smell, and an excellent ability to shed heat in the mid-day sun.
That being said, there exists a group of humans in a [rainforest environment](https://worldbuilding.stackexchange.com/questions/69100/how-to-build-a-floating-farm) where the best time to be awake is twilight. For these people, the primary food source varies by wet and dry season, but either way it is fish. The old fisherman's adage is that the fish are most active at dawn and dusk. In the dry season, these people use twilight to fish in oxbow ponds and shallows on the edges of the great rivers of the forest. In the wet season, the rivers flood their banks and become long lakes. The people fish just before daybreak and after sunset, attracting small schooling fish by lantern-light.
[](https://i.stack.imgur.com/Gsu6G.jpg)
There are other agricultural activities, which primarily revolve around gathering fruits and nuts from semi-wild orchards planted in the forest, and growing vegetables in floating farms (detailed in the linked question).
Overall, **would it be beneficial for these people to adopt a fully crepuscular lifestyle?** A [crepuscular](https://en.wikipedia.org/wiki/Crepuscular) chronotype would be one where there are two periods of sleep per day, one during mid-day and the other mid-night. There would be two ~six hour periods of activity around dawn and dusk, with two ~six hour periods of rest in between.
Are there chemical or biological reasons why this would not work? Does the advantage of being awake when your primary food source is available overcome the poor nighttime senses for an agricultural society?
### Considerations
* As this is a tropical rainforest, day length does not vary over the year, so no need to worry about long days or nights.
* Technology level is Bronze Age. The crepuscular lifestyle would have developed after these people became primary fishermen, perhaps a few thousand years before.
* The humans are biologically identical to us. The environment is comparable to what one might find in the Amazon or Congo basin.
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A six-hour sleep in the middle of the day is quite unusual, but 2-3 hours? The Spanish call it a [siesta](https://en.wikipedia.org/wiki/Siesta).
The advent of air-conditioning has made them less common, but the principle was that from about 11:00 to 14:00 it was just too hot to do anything. So, the working day started earlier, in the cool twilight of dawn, and ended later, in the cool twilight of dusk.
So, a crepuscular lifestyle has been proven over thousands of years to be perfectly viable - the only real question is about making it 6 hours of sleep. Although, looking at Mediterranean countries, I suspect a 4:8:4:8 pattern of sleep/awake is more likely than 6:6:6:6
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I am from India and I can say that already there is some change in chronotype of our IT professionals in the past decade or so. They have to work when their clients are active say in US and other western nations. So the Multi National Companies here in India (like TCS, Wipro, Infosys,..) have a workforce available during our night time. I think economic reasons will be the basis on which human chronotype would change.
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**To avoid the heat**
Since tropical rain forest are extremely [hot and humid,](http://www.blueplanetbiomes.org/rainforest.htm) people would have a [harder time cooling themselves](https://engineering.mit.edu/engage/ask-an-engineer/why-do-we-sweat-more-in-high-humidity/). In order to avoid overheating, they would have to avoid the daytime, where the temperature is highest. That way, the humans would adopt a crepuscular lifestyle in order to avoid the heat of the day, but also the darkness of the night where they can't see.
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Historically this has already occurred in multiple recorded instances... our circadian rhythm is malleable.
Removing any time devices from a person, no clocks, no day/night cycle, and their clocks will change. Longer I believe, something like 30 hours... there have been studies, I'll see about finding citations.
In the pre-industrial era, middle ages possibly, in northern regions we operated with two waking cycles per day... one during daylight, one at night.
Optometry is telling us all now to stay off electronics at night because the blue light disrupts or circadian rhythm and prevents us from falling naturally to sleep...
I've spent years on swing shifts where I got to a point where predawn light triggers a sleep response (though I avoided actual dawn light desperately because the wakefullness brought on by a flood of natural light is really hard to overcome)
...also consider the Arctic, at certain times of the year "day" and "night" are fundamentally arbitrary. I was up there in the summer one year and was surprised how comfortable doing whatever, whenever became.
This is a very strongly supported logic in both biology and sociology... being diurnal is an easy fit for civilized man, so we think of it as "natural"... but I wouldn't say it is intrinsic to the human condition by any stretch.
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Assume there are three earth-like worlds in our solar system. These three worlds would also have a single natural satellite roughly at the same mass-distance ratio of Earth to the Moon (about 1.2 percent of each of their masses and about 384,400 km distant give or take).
I'd put the innermost of the three is in the current orbit of Earth and the outermost is where Mars is. Where could the third planet and moon exist between the two that they'd be stable over significant time (billions of years)?
I am assuming all three would be habitable.
Can we fit those other two earth-like planets in our solar system? How?
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Some speculation that the Earth doesn't have Venus's atmosphere due to the presence of the moon. So given a moon to Venus may be sufficient to thin out the atmosphere over sufficient time. Put Ceres in a 90 minute orbit might do the trick and spin Venus up at the same time. (Wait. Roche limit. Hmm. Another ringed planet. Would a band of rings have a net cooling effect?)
A more massive Mars could hold at atmosphere for more time. A molten core may provide a magnetic field to keep the solar wind from splitting water.
Change the orbital distances with some caution, and a lot of simulation time. Orbital dynamics is tricky. Resonances where the period of one is a small integer ratio with the period of another are particularly tricky.
If you accept a solar system formed with massive terraforming by a previous civilization, or working on a very long time scale, bombarding Mars with enough comets would establish at least a transient (few tens of millions of years) atmosphere. Use something like Ceres, and try for a gentle collision and you would get a mass boost, plus a molten core again. Drag one of the ice moons in and siphon off enough water to fill martian seas.
Venus could be uninhabitable if you can get rid of most of the atmosphere (matter transport to mars...) and paint most of it titanium dioxide white. You want a material that is black in the infrared, and white in the visible to minimize solar absorption, and maximize radiation. Even with this I think you would have a wide equatorial band that was too hot. While your at it hit with enough rocks to give it a decent spin.
Remember also that you have 6 other potential spots in the trojan positions 60 degrees ahead and behind these 3 planets. Could be good parking places for ice moons to thaw, or to have industrial worlds. The energy to move from one trojan point to the other in the same orbit is a matter of how long you are willing to wait.
There are other Lagrange points:
\* L3 "Counter earth" on the opposite side of the sun:
\* L1 "Sub solar" where it between earth and sun, with the excess gravitational attraction of the sun balanced by the gravitation of the earth.
\* L2 "Supra solar" where it is just beyond the earth along the earth sun line.
None of these are long term stable. The counter earth I think is close to neutral stability. L2 and L1 are unstable, and perturbations grow rapidly. If you have the resources to move planets around, however station keeping should not be a big issue.
If you need more real estate, play with orbital dynamics and sharp angles to the ecliptic. These have less coupling, and so you should be able to orbit a planet at right angles to Earth's orbit between Earth and Mars. Note that the energy to reach these orbits is horrendous.
Another solution that is elegant, but difficult is a klemperer rosette. N bodies in an ellipse co-rotating about their mutual center of gravity. This has been used in two stories that I know of: The Fleet of Worlds of the Puppeteers of Niven's known space universe, and in Arthur C. Clarke's novel either Against the Fall of Night or The City and the Stars, where reference is made "It is lovely to watch the coloured shadows on the planets of eternal light."
AFter this, it's time to look at building ringworlds.
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The Habitable Zone for our star actually reaches from about Venus to about Mars: <https://en.wikipedia.org/wiki/Circumstellar_habitable_zone> so if you wanted to, you could stretch the distance out.
That being said, your question was basically "could there be another earth-size planet in-between where Mars and Earth is, effectively", which the answer is likely "No" - when the planets were forming, they each were clearing a path for themselves out of the stellar nebula. An earth-like object would of course, be gravitationally dominant out to a certain distance, since it "scoops up" all the material in that range of orbit from the sun. During the merger phase, two objects of similar size would eventually mess up each other's orbits enough that only one would become dominant (or they'd crash into each other, like what happened with the earth and a mars-sized object). See <https://en.wikipedia.org/wiki/Nebular_hypothesis#Formation_of_planets> for a general explanation of how planets form around stars.
So short answer, you'd likely have to have the three planets at the locations Venus - Earth - Mars are now, rather than putting another planet in-between Earth and Mars; it simply wouldn't survive the planet formation stage.
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You could do it this way:
* Change the radius of the Earth to 9000 km, and drop its density to 3300 kg/m$^3$ (same as the moon). This will double its mass and provide .85g of surface gravity
* Increase the radius of the moon to 2400 km (same as Ganymede) and increase its density to 6300 kg/m$^3$ (same as Earth). This will increase its mass by a factor of 5 and increase its surface gravity to 0.43g. Adjust the Earth-Moon distance for stability.
* Increase Mars's density to that of Mercury (5400 kg/m$^3$). This increases its mass by about 30% and surface gravity of 0.52g
* Increase the strength of the sun by 20%.
Now you have three 'planets', with roughly similar surface gravity, all within the habitable zone of a star. Alternately, you can use Venus as the third planet and make the sun weaker, if you want two colder planets and one hotter.
This is a configuration that would be stable for a long time. Now, I don't know if the planets could naturally evolve this way, but that's another question.
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*Alternate question title: From Fungi to a Fun Guy*
So, I asked a [previous question](https://worldbuilding.stackexchange.com/questions/34034/could-plants-develop-sentience) about which non-animal would be the likeliest to evolve sentience. The answer turned out to be fungus, since mycelial networks closely resemble neurons.
My question is dual pronged, because I think it would be difficult to separate. How would a fungus evolve into a sentient creature, capable of animal-like levels of movement and perceiving their surroundings, and of human level intelligence? What kind of environment would foster these developments?
[Answer]
Before we start, it's worth noting that fungi really *aren't* more likely to develop intelligence than plants. Sure, there may be "intelligent" fungi, but there are [plants that do the same things](https://en.wikipedia.org/wiki/Pando_(tree)) that are significantly safer than fungi, and that can inhabit a wider range of habitats. Making decisions about routing nutrients is not uncommon - and it's in no way closer to intelligent thought than, for instance, the reflexes of a carnivorous plant.
I still advise choosing plants instead, but that doesn't mean fungi cannot make it work.
## Option #1: Start with a yeast
[Yeasts](https://en.wikipedia.org/wiki/Yeast) are usually single-celled fungi. Some have been observed to produce longer chains - an excellent start to build some larger tissues. Similarly to how life is thought to have evolved from single-celled organisms long ago, you could provide the evolutionary pressures to develop yeasts extensively into larger animals.
A good starting pressure could be the need to compete for food (sugars in this case) due to scarcity in an environment. This would produce complex **locomotion** and **sensory** methods generations later, and perhaps small, multi-celled animals would evolve given enough time. They would no longer rely on parasitism or decomposition to procure sugars; an herbivorous lifestyle could develop. From there, the same basic evolutionary steps that produced humans can be followed.
## Option #2: Require active response for survival
Your previous question has answers that can be adapted for this one.
@ChefCyanide said the following when describing how a plant would evolve intelligence:
>
> As for evolution, this complex would require a rather unique environment, in which traditional methods of mating (pollination) and/or obtaining resources (photosynthesis) are possible and yet not ideal for survival and continuation of the species. An example of this could be an area frequently shrouded by large, dense, slow-moving clouds, or where there is virtually no wind or pollinating insects present.
>
>
>
While we are not dealing with plants, the same ideas apply: your organism must actively respond to stimuli relatively quickly. If you want to adapt a **mycelial network** (like that described in the top answer to the previous question) to become conscious, for example, you must make resources hard to get - and have it actively work for them.
Maybe food is scarce, or the soil is barren, so the fungus has to actively grow onto a nearby tree to sustain itself. Or perhaps it must divert energy into making a sweet-smelling chemical to attract insects, or change colors depending on the predator nearby. All of these processes could develop through mutation, specialization, and natural selection.
Eventually, it is possible for consciousness to develop in such an organism in order to respond more efficiently to the world around it. It may be a drastically different consciousness to our own, and it may not have the potential to develop communication or locomotion, but it will be able to think.
## Option #3: Endosymbiosis
The [cordyceps](https://en.wikipedia.org/wiki/Cordyceps) fungus has been observed infecting hundreds of species of insects. In some cases, it "hijacks" the brains of its hosts, compelling them to do specific actions - such as climbing trees, so that it can release its spores into the wind.
In a process called [endosymbiosis](http://www.biology-pages.info/E/Endosymbiosis.html), it may be possible for a similar fungus to coexist with its hosts. Perhaps it evolves the ability to release multiple rounds of spores. To spread them over a larger area, the host must be kept alive long enough to move around significantly. The fungus coexists with the hosts, and spreads to their offspring, until they're united as one "species". This favors the hosts, which are more likely to survive than other infected parts of the population - and may become immune to other invasive fungi if the space is already taken. It also favors the fungi, which now require less work to reproduce; they have the guarantee of the entire infected population.
The fungi may continue to produce chemicals that impact the hosts' brains. They may become more complex, and beneficial, over generations - allowing the fungus to "think" indirectly.
[Answer]
From the 80's and 90's video game Star Control, consider [Mycon](http://wiki.uqm.stack.nl/Mycon). Mycon was a genetically engineered artificial species, designed to perform labor in terra-forming. They absorb ambient energy and can intentionally select which genes to pass on to the next generation.
Borrowing from this, as many fungi reproduce asexually, one develops the ability to select which genetic characteristics to pass on to the next generation. First, they will improve the ability to select genes. A by-product of this is enhancing intelligence to improve decision making. Over time, they gain sentience.
Then, massive death starts in their community. They first select genes to allow sensing of their surroundings, and then a means to share information. They learn that they are being consumed by humans, using machines.
The fungi first try poison - and learn that the humans can destroy them very rapidly. They then develop a means to escape by wind, then eventually develop muscles. They find that muscles require a ton of energy, so they find a way absorb electricity directly. They then spread via the electrical infrastructure, and learn to control computers and machines, then how to consume humans.
From hear, of course they learn how to leave the planet to spread through the universe.
[Answer]
First, it would have to be conducive to [mushroom life](http://homeguides.sfgate.com/environment-mushroom-growth-28551.html), nearly planet-wide, then there would have to be environmental pressures making life difficult and pushing adaptation.
For plant life not to be dominant there needs to be little or no sunlight in the environment, or places where sunlight is blocked by plantlife.
There would have to be a reason to develop a brain and everything else (like hands). I can see it being a colony with one or two "caretakers" shaping the environment. Since those colonies with caretakers would thrive, more would be made.
That's my take on it anyway!
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[Question]
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We see plenty of seasonal variation on Earth, due to the large axial tilt, but the Earth follows an almost perfectly circular orbit, so we don't get much variation as a result of that.
What if we had a planet with similar axial tilt, similar conditions, etc., but in an eccentric orbit? What will that do to the climate, especially in terms of temperature variance? How much hotter/colder are the extremes going to be, and how much worse will things get when the two effects (eccentricity and axial tilt) combine forces to create even nastier extremes? For bonus points, what will temperature bands look like, given that an eccentric orbit will cause a specific latitude (somewhere between the tropic lines) to be very hot at perihelion, since the sun will be directly overhead on that line at the point of closest approach?
I'm hoping for answers with formulas that explain how one could calculate this, so that other people can build on the information and tweak it to suit their worlds. For the same reason, I'll offer a few sample orbits for people to use in providing examples.
Case A: eccentricity of 0.1, perihelion at the northern summer solstice.
Case B: eccentricity of 0.1, perihelion at the vernal (northern spring) equinox.
Case C: eccentricity of 0.2, perihelion at the northern summer solstice.
For the purposes of this question, assume that Earth is the planet following an eccentric orbit; it'll make things easier to understand. Answers that express temperature variance in proportion to what Earth faces are fine: if, for instance, case A is going to have a northern winter 20% colder than Earth would, that's pretty straightforward.
[Answer]
That's a difficult question to answer. Every formula, I don't explain is from Wikipedia. I'll try to answer your first question: How would an more eccentric orbit than earth influence the temperature on a planet which orbits around a star. However, since I still deem this to be a difficult question, let me make a few simplifications: (I will later discuss what happens if you don't make this)
1. The Planet consists completely of only one solid material x. Where $x$ has a density of $\rho\_x$, a specific heat capacity of $c\_x$ and a specific thermal conductivity of $\lambda\_x$. No fluids, no gases, no athmosphere.
2. The temperature on every point of the surface planet is the same, at any time.
3. The planet has no internal heat source
4. Only the surface changes temperature, deep inside it will always stay at the same temperature.
## Calculation
What I will effectively do is calculating the temperature y meters below the surface. In other words, I'll calculate a function $f(t,d)$ of the temperature, where $t$ is the time and $d$ the depth, how many meters below the surface we calculate the temperature. Further let $D(t)$ be the distance the planet has at time $t$ from the star.
How much power does reach the planet on every square meter? You have to calculate how much light reaches the planet.
In formulas: $\frac{Lr^2(1-A)}{4 D^2}$ Where $L$ is the luminosity of the star (for our Sun about $3.845\*10^{26} W$), $r$ the radius of the planet, $A$ the albedo (for our earth about $0.3$) and $D$ the distance to the star. To calculate the power per square meter you divide by the surface of the planet, which gives us $P\_{in} = \frac{L(1-A)}{16 \pi D^2}$ (in $\frac{W}{m^2}$).
How much energy gets lost due to infrared radiation per square meter? $P\_{out} = \epsilon \sigma T^4$, where $\epsilon$ is the emissivity of the planet (for earth approx $0.612$) and $\sigma \approx 5.67 \* 10^{-8} \frac{W}{m^2K}$ the Stephen-Bolzman-constant.
Due to thermal conduction, the interior of the planet heats the surface and in the process cools itself down. The equation for the heat flow density is $q(\frac{\Delta T}{l}) = \lambda \, \frac{ \Delta T }{ l }$, where $\lambda$ is the specific thermal conductivity, $\Delta T$ the temperature difference, $l$ the length of the object (in our example the depth) and $q(\frac{\Delta T}{l})$ is the thermal conductivity as a function of the length and the temperature difference. Here I'm using 5., since the planet is smaller at a depth of $d$ than at the surface. For small $d$ this is negligible. The temperature at a depth $d$ only depends upon the temperature directly above and below. Therefore the energy flow at $d$ meters below surface can be calculated as $\frac{\mathrm{d}}{\mathrm{d}d}q(f(t,d))$. On the surface it is only half as much since noting is above the surface. Therefore, we get a power per square meter on the surface of $P\_{flow} = \frac{1}{2}\frac{\mathrm{d}}{\mathrm{d}d}q(f(t,d))$.
Now we have $P\_{in} - P\_{out} + P\_{flow} = 0$, since only these three factors influence the surface temperature. Therefore we have:
$$
\frac{L(1-A)}{16 \pi D^2} - \epsilon \sigma f(t,0)^4 + \left[\frac{1}{2}\frac{\mathrm{d}}{\mathrm{d}d}q(f(t,d))\right]\_{d=0} = 0
$$
Inserting $q$ gives us:
$$
\frac{L(1-A)}{16 \pi D^2} - \epsilon \sigma f(t,0)^4 + \left[\frac{1}{2}\frac{\mathrm{d}}{\mathrm{d}d}\lambda \, f(t,d)\right]\_{d=0} = 0
$$
I don't even try to solve this differential equation exactly. However, it is possible to calculate the temperature $f(t,d)$ at the surface approximatively given all other data.
To heat $1m^3$ of $x$ up by one degree, we need an energy of $\rho\_x \* c\_x$. $q$ is the heat flow. To calculate how the thermal energy changes, we have to differentiate $q$. Therefore the temperature change at a depth $d$ is
$$
\frac{\mathrm{d}}{\mathrm{d}t}f(t,d) = \frac{\frac{\mathrm{d}}{\mathrm{d}d}q(d, f(t,d))}{\rho\_x \* c\_x} = \frac{\lambda\frac{\mathrm{d}}{\mathrm{d}d}f(t,d)}{\rho\_x \* c\_x}
$$
This allows us to calculate how the temperature changes given that we know how it is at the moment. With computer aid you can approximatively calculate the temperature of the planet.
## Example
Let us choose $x$ to be $SiO\_2$. The mantle consists to a large part of $SiO\_2$. We have $\rho\_{SiO\_2} \approx 2500\frac{kg}{m^3}$, $\lambda\_{SiO\_2} \approx 1.3 \frac{W}{m \* K}$ and $c\_{SiO\_2} \approx 1050 \frac{J}{kg K}$. Let us assume at first our planet circles the sun at a distance of $1AE = 1.496 \* 10^{11} m$, just like the earth, but on a perfect circle. (Remember: $L = 3.845 \* 10^{26} W$, $A = 0.3$ and $\epsilon = 0.612$)
After some time the temperature will become the same everywhere. This means, we have $P\_{flow} = 0$ and $P\_{in} = P\_{out}$. This gives us a constant temperature of $288.15K \approx 15 °C$. (That is about what is true for the earth)
Now let us assume, by magic the planet is suddenly on an circular orbit $2AE$ from the sun. That means that it gets only $\frac{1}{4}$ of the light. The planet will eventually cool down to about $203K$. However, that will take some time. How is it after say $180$ days? My calculation says, that up to 7 meters, everything is completely frozen, while below 8 meters the temperature is still about $288 K$. (Compare to permafrost where the ice never melts starting from a few meters below the surface)
This example tells us, that an eccentric orbit will only influence the surface temperature.
## Generalizations
In the beginning I made a few assumptions.
1. Point gives me a little trouble: You can easily use the same model for several different materials. (Simply assume, that $x$ is a mix of them or calculate it independent for different places on the surface) However, the athmosphere can play havoc on the calculations. The same goes for liquids like oceans. However, I think, the atmosphere would rather benefit the living creatures, since it slows the temperature changes. Oceans will likely stay the same temperature a few hundred meters below the surface, like now (even when the eccentricity is as extreme, as my example above.
2. is easy to work a round: One can make the same calculation for different points of the surface. However, one has to consider, that different places get a different amount of sun light: On midday at the equator, you get 4 times the light than an average place.
3. The internal doesn't has a relevant effect on the surface temperature. However, it does help to keep everything below the surface warm, a little bit.
4. We saw in the example that this assumption holds.
[Answer]
So this problem basically has two parts. The answers so far have tried to answer the problems with evening heat out over the surface of the planet. I am working on a circulation model to do just that, but that is complicated and not ready. However, the other part of the problem is the question of insolation. How much solar energy is your planet really receiving? That I can answer with the approach I used [here](https://worldbuilding.stackexchange.com/questions/62948/season-cycle-that-would-occur-on-a-habitable-planet-that-orbits-two-suns/62992#62992).
# Defining planet's orbit
This is just application of [Kepler's laws](https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion). The semi-latus rectum can be defined by $$ ap = b^2,\quad b = a\sqrt{1-e^2}$$ where $p$ is the semi-latus rectum, $a$ is semi-major axis, $b$ is semi-minor axis, and $e$ is eccentricity. Assuming semi-major axis is 1 AU, those two equations combined give $$p = 1-e^2.$$
The semi-latus rectum is used to find orbital distance as a function of time by $$r = \frac{p}{1+e\cos(\theta)}.$$
Since theta goes from $0$ to $2\pi$ and we want that orbit to take 365 days, we can use python (3.5.2) code to return distance as a function of eccentricity and time (in days) as:
```
def f(e, t):
p = 1 - e**2
theta = 2 * pi * t / 365
return p / (1 + e * cos(theta)), theta
```
Zero time for this function is defined at perihelion.
# Plot solar energy as a function of time
The first component of solar energy is the relative solar energy due to distance. This is simple, since solar energy flux follows an inverse square law, energy = 1/r\*\*2.
The second component is the seasons. Copying my work from that other problem I linked, I use insolation at 45 degrees north. Insolation as a percentage of maximum (maximum insolation of 1 unit being when the sun is directly overhead) is the cos(latitude - axial\_tilt \* sin(time)). Axial tilt is 23.5 degrees, same as earth.
Since this seasonal component is a percentage of maximum, we simply multiply it by the distance component to get total energy.
Here is the code that gives us some graphs:
```
def plot_energy():
x = [i/10 for i in range(3650)]
orbit_a = [r for r, theta in [f(0.1, t/10) for t in range(3650)]]
orbit_c = [r for r, theta in [f(0.2, t/10) for t in range(3650)]]
seasons_a = [cos(radians(45-23.5*sin(i/10/365*2*pi+pi/2))) for i in range(3650)]
seasons_b = [cos(radians(45-23.5*sin(i/10/365*2*pi))) for i in range(3650)]
energy_a = [1/r**2 * n for r, n in zip(orbit_a, seasons_a)]
energy_b = [1/r**2 * n for r, n in zip(orbit_a, seasons_b)]
energy_c = [1/r**2 * n for r, n in zip(orbit_c, seasons_a)]
plt.plot(x,energy_a, 'b', x, seasons_a, 'g')
plt.axis([0, 365, 0, 1.5])
plt.show()
plt.plot(x,energy_b, 'b', x, seasons_b, 'g')
plt.axis([0, 365, 0, 1.5])
plt.show()
plt.plot(x,energy_c, 'b', x, seasons_a, 'g')
plt.axis([0, 365, 0, 1.5])
plt.show()
```
And here are the graphs. Blue represents your planet's insolation, and Green represents the Earth, with the seasons aligned.
Case A
[](https://i.stack.imgur.com/KfTVb.png)
Case B
[](https://i.stack.imgur.com/1n1YH.png)
Case C
[](https://i.stack.imgur.com/3VhXf.png)
I added the python code so you can replicate or modify if you want. If you do use it, make sure you are in python3 and import from math and matplotlib:
```
from math import sin, cos, pi, radians
from matplotlib import pyplot as plt
```
# Discussion
While the seasons play a bigger role in insolation changes than the orbit does, the combination of summer at perihelion is significant: a 45% increase in solar energy. It is worthwhile pointing out that with Northern Hemisphere summer aligned with perihelion, the Northern Hemisphere on your planet gets significantly higher solar energy than the southern hemisphere. If the equinox is aligned to perihelion, then the seasons are equal in North and South.
If 1.00 is the amount of sunlight energy received in a year with the sun directly overhead at 1 AU, than on Earth 45 N gets 0.68 and the Equator gets 0.96 over the course of the year.
For your cases, the Northern hemisphere, equator, and southern Hemisphere get the following values:
* Case A: N = 0.72, E 0.98, S = 0.67
* Case B: N = 0.69, E 0.98, S = 0.69
* Case C: N = 0.81, E 1.06, S = 0.69
You will also notice that you get more energy the more eccentric your orbit is. This is due to the sun's delivered energy increasing more for moving 10% inwards than for moving 10% outwards (inverse square law, and all).
[Answer]
As it's been a week without any answers offered, I think I'll share the results of my own further research here and see if people think it's close to the mark.
To get a basic temperature estimate for the planet, using the calculations for [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature) seems like a good idea. The Wikipedia calculations, however, calculate it over the course of a year; to cover an eccentric orbit, I'm going to run the calculations based on perihelion and aphelion distances, compare those to the result at the mean distance, and see how big the gap is.
Formula: $$T = (\frac{1}{4} \* \frac{L(1 - a)}{4\pi\delta\epsilon D^2})^\frac{1}{4}$$
The first ratio of 1/4 indicates how incoming solar energy is spread across the surface; a quickly rotating sphere ends up with about 1/4 (the area of a disc of equal radius), but a tidally locked planet would have about 1/2. L is stellar luminosity, about $3.84 \* 10^{26}$ in the case of Earth's Sun. $\delta$ is the Stefan-Boltzmann constant, around $5.67 \* 10^{-8}$. D is the distance between planet and star (for Earth, this averages about 149.5 million kilometres over the course of a year). $\epsilon$ is the emissivity, approximated as 0.96 to 1; this is how much of the incoming radiation is reradiated out to space again. a is the albedo, or how much energy is reflected; this is around 0.3 for the Earth.
For anybody doing this themselves, units: L is in watts per square metre, D in metres. T is in degrees Kelvin (this is basically the Celsius scale, but 0 C is 273.15 K).
The basic formula doesn't account for the greenhouse effect, internal heating, etc.; it effectively assumes that the planet has no atmosphere, and produces a figure of about 255 K for temperature (-18 C), which is obviously far too low. For a simplistic approximation that lumps all of those extra factors into the greenhouse effect, emissivity can be altered: for the Earth, this results in an emissivity of about 0.612, mostly due to cloud cover. T then becomes around 288 K (15 C), a much more reasonable figure.
Now, to actually calculating some examples, where PT = T at perihelion, AT = T at aphelion:
Case 1: D ~ 134.5km at perihelion, and ~ 164.5km at aphelion.
$$PT = (\frac{1}{4} \* \frac{3.84\*10^{26}(1 - 0.3)}{4\pi\*5.67\*10^{-8}\*0.612\* 134,550,000,000^2})^\frac{1}{4} = ~303.7 K (~30.59 C)$$
$$AT = (\frac{1}{4} \* \frac{3.84\*10^{26}(1 - 0.3)}{4\pi\*5.67\*10^{-8}\*0.612\* 164,450,000,000^2})^\frac{1}{4} = ~274.75 K (~1.60 C)$$
Yikes! Those figures don't look too promising for life; those are averages over the planet, which means that perihelion probably annihilates the ice caps and turns the equator line into a 40 C or higher deathtrap. Still, I could be wrong; maybe these predictions are only equilibrium temperatures in these cases, which means that the Earth is trying to reach them but not fully doing so (courtesy of the day going by, putting various parts under shade to avoid baking them like bread).
If anybody can offer an answer covering how the extremes might be softened, that would be appreciated. Answers or comments covering how seasons might look different (what spring might turn into if perihelion is during spring instead of summer, for instance) are also welcome.
[Answer]
There's about an 20 W/m^2 difference in solar input when averaged over the curved surface and night/day but the effect of this goes largely unnoticed because perihelion aligns almost exactly with the N hemisphere winter solstice and its effect is conflated with the seasonal solar difference which when averaged over each hemisphere is about 280 W/m^2 in the N and 300 W/m^2 in the S. Notice the difference in seasonal variability in the S? In about 11K years, this will be reversed.
The planet behaves quite differently when perihelion is aligned with the N hemisphere summer because of the significant asymmetry between how the 2 hemispheres respond. This is evident in the ice core data which has local minimum and maximum temperature swings of about 2 degrees C that corresponds exactly to the periodicity of the precession of perihelion.
To put this in perspective, the solar energy increase that's equivalent to doubling atmospheric CO2 since pre-industrial times is only about 3.7 W/m^2.
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[Question]
[
I am an immortal, megalomaniacal supervillain with unlimited resources and patience. I want to slowly eliminate the Earth's axial tilt so that its equatorial plane is coplanar with its orbital plane. How can I achieve this without causing huge numbers of deaths? Assume that I have subjugated the entire planet, and no one will attempt to thwart me. I'm willing to do it slowly over thousands of years so that Earth's life forms have some time to adapt to the lack of seasons.
My first thought is to create some kind of vast, world-spanning magnetically-sensitive rail that will make use of the Earth's magnetic field (or the sun's, or maybe the solar wind?) to create a small asymmetrical rotational force on the planet.
My second idea is to create a space elevator-type structure, with its base on the equator. The tip of the elevator would be a large "sail," comprised of many small panels that could be opened or closed. When closed, the solar wind would push on them, applying a force to them which is transmitted down the elevator stalk to the Earth; when opened, the solar wind would pass through without pushing on them. Thus, the panels would open and close depending on the position of the sail, so that the solar wind would affect it more when it's at a position that decreases Earth's axial tilt, and affect it less when it's at a position that increases Earth's axial tilt.
[Answer]
**Earth is already wobbling around in a process known as [axial precession](https://en.wikipedia.org/wiki/Axial_precession#Effects) on a period of about 26,000 years.** The Wikipedia article says that the precession is a gravity induced effect from the [Sun and Moon](http://www.astro.cornell.edu/academics/courses/astro201/earth_precess.htm). With unlimited resources (and assuming unlimited energy) the right gravitational pushes could be given to Earth to push the axis of rotation to be perpendicular to Earth's orbital plane. I haven't a clue how much mass it would take or where that mass would sit in relation to the Earth, Sun, and Moon. Orbital mechanics are tricky to get right for small satellites, doing it for a planetoid size mass would be very tricky. Thank goodness for handwaving.
Alternatively, **the tilt of the earth could be altered by passing an object with a very large magnetic field through earth's magnetosphere**. Again, the math about how to make such an object, position it so that it doesn't affect the orbits of the Moon or Earth and keep the thing in position is far far far beyond me.
Given the timescales involved, throwing big rocks at the right place on earth to alter the spin isn't an option. The biosphere thanks you, Oh Great Leader!
[Answer]
Find a large moon and put it in an orbit that consistently pulls on the equatorial bulge in a way to decrease its tilt. Adjust the moon if it loses sync.
Additional benefit: You can write your name on this second moon as a permanent reminder to the peons!
] |
[Question]
[
Somewhere, far away in the universe, there is a galaxy that has not been made by nature. Whatever kind of hyperadvanced civilization could have created such a titanic project, and for whatever purpose is not relevant in this question. At the center of this artificially constructed galaxy is a black hole 300 trillion times as massive as our sun. Surrounding that hole is an accretion disk one quintillion times as bright as our sun. Surrounding that is a habitable zone three times as wide as the entire Milky Way galaxy. Within this zone is a K5 main-sequence star, 74% as wide, 69% as massive and only 16% as bright as our sun. Such stars burn their hydrogen so slowly that they can last not for ten billion years like our sun, but 34. And they are so hot that they can have a habitable zone that isn’t close enough to tidally lock their planets. Another, equally important, factor about orange dwarves is that they emit very low quantities of ultraviolet radiation.
The planet that orbits that star is its own alien space bat, a planet that blatantly and violently disregards our understanding of astrophysics. At 18,500 miles wide, it is 230% as wide as Earth, resulting in an overall area of 1,075,210,086 square miles. But instead of having a crushing gravity as a super-Earth should, it carries instead 100% of Earth’s gravity. A single day lasts 26 hours, and it rotates 417 times to make up its year. We have measured its magnetic field at no greater than 7.8 gauss, 12 times greater than on Earth. Its atmosphere is just as thick as Earth's. The star rises from the west and sets on the east, yet the planet still orbits it from a prograde, or counterclockwise, direction. Its axial tilt varies from 19.7 to 26.9 degrees. However, it’s not all that this planet has to define its seasons. Regardless of the point in the year, the accretion disk outlining the black hole will always be present in the sky, measuring in at an angular diameter of half a degree. The star, in turn, measures in at 1.88 degrees wide, almost four times as wide as our sun. Both sources of light are present during the day in the “summer” months. Its single moon is so far away and yet so large that it fills in at an angular diameter of 2.61 degrees.
Here is the planet's current map:
[](https://i.stack.imgur.com/tKVxN.jpg)
And then, here is the planet's current map with mountains labeled and directed for tectonic movement:
[](https://i.stack.imgur.com/67gUk.jpg)
The land between the two mountain ranges used to be a basaltic plateau before the collisions squeezed it up into being as high as Tibet.
Currently, carbon dioxide in the atmosphere is 500 parts per million, and oxygen makes up 35% of the atmosphere.
Using all of the information listed above, what would the Köppen classification climate map of this world look like?
[Answer]
The greater the planet's axial tilt angle, the more extreme the seasons are, as each hemisphere receives more solar radiation during its summer, when the hemisphere is tilted toward the K5 main-sequence star, and less during winter, when it is tilted away.
Increasing the planetary radius (in your case 9,250 miles) also leads to a lower planetary albedo and warmer climate, pushing the inner edge of the habitable zone to lower stellar irradiation.
>
> The most immediate effect of *changing Earth's axial tilt to 21.5 degrees* would be a fast expansion of the north pole ice cap and the freezing to the ocean surrounding Antarctica. In the northern hemisphere there is about a 1000 mile zone starting at just below the polar circle and extending about 1000 miles southward where most of the earth's conifer forests exist. [Socratic](https://socratic.org/questions/what-would-happen-if-the-earth-s-axial-tilt-were-to-decrease-from-23-5-degrees-t)
>
>
>
Given that earth's axial tilt range is between 22.1 and 24.5 degrees in a cycle of 40,000 years, your planet's axial tilt range of 19.7 to 26.9 degrees is quite massive. The greater the axial tilt, the more extreme the seasons, and less extreme seasons for the lower the axial tilt. So your planet is likely to experience very mild and very extreme weathers, which includes long winters (extremely cold ones) and probably not so long summers.
I would classify the entire top "part" of your map as ET (tundra) or EF (ice cap). Most of the center of the large "island" poking out would have a few BWh (desert) regions, quite a lot of BSk (semi-desert) regions. Your entire continent should consist of mainly DWc or DWd (subarctic) regions due to winters.
But mainly, the temperature should be decently close to Earth's, but with variations in the increase and decrease over seasons.
*This is a very vague impression and likely wrong*
[Answer]
# This is tough to say with the data provided.
You've said the star is somewhere within a habitable zone, whose distance is not specified, defined by a very bright light source (the accretion disk). The planet has a 452 (Earth) day year around a star of 0.69 solar masses: take T = 2 pi a^1.5 u^-0.5 and we have that the planet is just slightly further from the star than Earth, receiving just 16% of the light, so the accretion disk *dominates* the energy contribution. Assuming it provides 0.84 fraction of Solar light, starting from 1E+18, taking the square root, we get 9.1E+9 AU distance from the accretion disk. That gives me 14500 light years ... hardly "three times the Milky Way", but there are a few ways to take that.
Bigger problem is that the star rises in the west, and the planet's orbit is *not* retrograde. Normally a star rises in the west because someone uses an unfortunate definition of "north" that goes by the whole star system (and hopes nothing lands closer to edge-on than Uranus). There *is* a way a star could rise in the west even exluding that ... the planet might orbit *faster* than it rotates, so that the star creeps up the zodiac faster than it can turn out of the sky. But for that, your planet has to have many sidereal days before the Sun catches up once for the year ... or something. I don't really know how to make it work.
Anyway, given the data, assuming the orbit worked out above, the planet depends entirely on a *fixed astronomical feature* for light, i.e. the accretion disk. That's different from a planet revolving around a star. The disk could be above one pole of the planet, or the other, in which case it is much like a tidally locked planet, only rotating... However, I'll take your statement that *"Regardless of the point in the year, the accretion disk outlining the black hole will always be present in the sky"* to mean that it is *precisely* equatorial ... in which case it does act exactly like a normal star would, except there's one more "day" by that standard (sidereal day, not synodic), and the accretion disk might be eclipsed for part of the year by the dim red sun, if it happens to align with the accretion disk at an equinox. Note that there are no seasons, despite the axial tilt, from the accretion disk, assuming it is at the equator, so only the star provides very weak seasons as it moves north and south in the sky.
Now all that said, I've only *assumed* the planet is like Earth in temperature overall; the distance isn't given and the atmosphere is different. But if it's like Earth, you have a continent at the top which is like Antarctica, a high plateau at the equator which is like Kilimanjaro, and other terrain that is between but not truly "temperate" due to the weakness of the seasons. I'm reluctant to start talking about which way the winds blow because of the "sun rising in the west" thing!
[Answer]
**It will be too hot there for liquid water.**
Let us science this up. How can we determine how close this planet is to its star? We know the size of the star and we know how big it appears from the perspective of the planet. We can use those values to calculate the distance. This will be a big help in determining likely climate.
<https://lco.global/spacebook/sky/using-angles-describe-positions-and-apparent-sizes-objects/>
d = 206,265 D / θ
D = linear size of an object
θ = angular size of the object, in arcsec
d = distance to the object
Star is 74% the width of our sun. Our sun is 1392000km, \*0.74 = 1030080 km width of star.
From OP angular size is 1.88 degrees
Convert degrees into arc seconds = 1.88 \* 3600 = 6768
1030080 \* 206265 = 212469451200
212469451200/ 6768 = the planet is 31393240 km away from its star; round to 31 million km = 0.2 AU
Our sun by comparison is 150000000 km away; 150 million km
Our sun is 70 million km from Mercury.
To use the habitable zone calculator
one needs luminosity and temperature. OP provides luminosity of 16% of our sun. I took temperature from here
<https://en.wikipedia.org/wiki/K-type_main-sequence_star>
; an average K5 star has 0.17 luminosity so that matches, and wikipedia gives an average of 4440K temperature
Here is a snip from the calculator at <http://depts.washington.edu/naivpl/sites/default/files/hz_0.shtml#overlay-context=content/hz-calculator>
[](https://i.stack.imgur.com/wfvKd.png)
At 0.2 AU the planet is not inside the habitable zone of its star. It is too close to the star. It is hot there. The answer to the OP as regards the climate: toasty, as in stuff there is toast. Melba toast.
A side question should someone be interested in playing with these calculators is that of the accretion disc. I did not factor that in but it too will illuminate this planet. One quintillion times as bright as the sun is pretty bright. 1800 arc seconds in the sky is not trivial. How far away is the radiation source represented by the disc and what is the calculated habitable zone, treating this object as a star for purposes of calculation. Dailey I am trying to salvage your world and I suspect that maybe it could be a rogue planet, warmed just by the disc.
Anyone interested in crunching those numbers is welcome to addend an edit to this question. I think the temperature of the disc might be hard to estimate.
[Answer]
Ocean currents play a huge role in climate. Air and ocean current are the planets way of trying to equalize the temperature of the whole planet. This is as we all know impossible but nevertheless it is an ongoing process.
Most significant thing that pops out to me in your map, is the southern pole being ice and obstruction free. this will produce and constant and quite large current around the pole region. This in turn will have a, perhaps not dominating effect but certainly over the long term very significant effect on the overall climate. The second is the large ocean, also unobstructed, there should be 2 large currents here separated by and equatorial counter current driven by surface winds west to east.
Let's call these two currents the north and south gyre, to give them anilogs to Earths.
The south polar current should be swift and constant, I would expect the southern most portion of the continent to be quite cold, and wind blown. Storms would be fequint from warm winds defected from the mountains, also along the southern cost. Little ice buildup would be preset because of the strong current. In Fact I would expect there to be quite a good amount of deformation in the coastal topography of the land in the direction of the current west to east. As the cost recedes north you may see ice build up in the sheltered areas. strong ocean eddies thrown off and rough seas commonly rough seas.
The Southern Gyre here Rotates counterclockwise pulling warm water from the equator (Down the east side of the continent, west side of the ocean) and pushing cool water up (Up the west side of the continent)
This is incomplete, not to mention probably inaccurate *guestimation*, but without any typographical data anything with higher resolution cant be expected.
**EDIT: Just reread this part:**
>
> The star rises from the west and sets on the east, yet the planet
> still orbits it from a prograde, or counterclockwise, direction.
> Blockquote
>
>
>
*Im not so sure what to make of this, not sure I understand how this works as the OP has explained. This has less to do with orbit than planetary rotation. But as another post mentions this will reverse the usual prevailing currents.*
[](https://i.stack.imgur.com/B7DBL.jpg)
[Answer]
This may help others
With the counter-ordinary daily rotation, the prevailing winds will reverse. However, I'd expect there to be a cell reversal around $\pm 30^0$ latitude.
The Himalayan-like mountainous zone will completel alter the equatorial southern winds. However, it will enhance the winds at the -30 degree cell.
[](https://i.stack.imgur.com/Pv7uZs.png)
At the 19.7 degree tilt, here is a description of the artic circle for your world. In these regions, the sun will never set during summer; and it will never rise during winter.
[](https://i.stack.imgur.com/4InNJs.png)
And at the 26.9 degree tilt.
[](https://i.stack.imgur.com/MH4vps.png)
With this information in hand, and using the Earth as a guide :
[Scale and Attribution](https://en.wikipedia.org/wiki/File:K%C3%B6ppen-Geiger_Climate_Classification_Map.png)
[](https://i.stack.imgur.com/DlA3Ss.png)
Since, by fiat, this planet breaks a little known physics to somehow be Earthlike, I've transposed the temperate bands from Earth, applied the only topographic feature provided in the question (the mountain range), and applied the winds relative to that feature.
I thought about applying great deserts, like the Sahara and Australia, but chose against it.
[](https://i.stack.imgur.com/wnKyn.png)
] |
[Question]
[
**Background**
I am investigating the practical utility and limitations of a procedural-generation-based naming scheme for stars and other notable or significant interstellar structures (e.g. nebulae, globular clusters) in a Milky Way-like galaxy, for use by an expansive interstellar civilization. Hundreds of billions of names, in other words. More specifically, however, a naming system based on – and communicating – key information about the objects it describes.
**Preliminary assumptions and findings**
***Phonemic inventory***
25 consonants and 15 vowels. Comparable to [English](https://en.wikipedia.org/wiki/English_phonology), more or less.
*Note: These are phones, not letters.*
***Syllable structure***
(C)V; C for consonant (optional onset), V for vowel (mandatory nucleus).
***Limitations***
I am hesitant to put hard limits on how long a name can be before it becomes impractical, particularly when short forms would inevitably be adopted for the most frequently used names.
Taking a cue from the world of taxonomy, [the longest taxonomic name](https://www.researchgate.net/post/What_is_the_maximal_length_of_the_taxonomic_name) appears to be in the realm of 18 syllables (not including "subspecies" or similar designations). The average word in English is just over six letters long, factoring frequency of use, so that's a fair amount of wiggle room.
***Permutations***
On first pass it appears to be achievable, with nearly seven and a half *trillion* unique names from just five syllables:
| Syllables | Count | Cx × Vy | Combinations |
| --- | --- | --- | --- |
| CV | 1 | 251 × 151 | 375 |
| VCV | 2 | 251 × 152 | 5,625 |
| CVCV | 2 | 252 × 152 | 140,625 |
| VCVCV | 3 | 252 × 153 | 2,109,375 |
| CVCVCV | 3 | 253 × 153 | 52,734,375 |
| VCVCVCV | 4 | 253 × 154 | 791,015,625 |
| CVCVCVCV | 4 | 254 × 154 | 19,775,390,625 |
| VCVCVCVCV | 5 | 254 × 155 | 296,630,859,375 |
| CVCVCVCVCV | 5 | 255 × 155 | 7,415,771,484,375 |
This would seem to be enough, but I'm not sure it would allow for encoding information without producing ambiguous or duplicate names, or if such encoding would eliminate too many possible combinations. Six or more syllables and multi-word names are, of course, permitted.
***Information density***
As above, ideally such a system will communicate useful information about the body or object, perhaps including but not limited to:
* Category of object – e.g. star, distinct from nebula, distinct from [globular cluster](https://en.wikipedia.org/wiki/Globular_cluster), etc.
* Class or type within category – e.g. Class K star, distinct from Class F; supernova remnant, distinct from planetary nebula; etc. Level of precision here will depend on the category of object.
* Location – I'm unsure how granular this needs to be to be *useful*, but I suspect the general location is probably more useful in some cases, and easier to encode than precise coordinates. Duplication of names could be permitted with a convention for distinguishing locations, depending on referent (e.g. quadrant, arm, distance from core or home world, etc.).
**Problems and considerations**
* Frequency: by some estimates three quarters of all stars in the galaxy are [red dwarfs](https://en.wikipedia.org/wiki/Red_dwarf), meaning a high degree of information granularity and/or sophisticated encoding methods are needed to avoid most stars having very similar names, but this granularity or sophistication would be unnecessary for much rarer stars. In a galaxy of 400 billion stars five syllables (VCVCVCVCV) would be consumed – nearly 300 billion names, each of them differing from its neighbours on the list by just a single letter – *just* by red dwarfs, and those names would not include any other information about the individual stars. At the other end of the spectrum, the rarer an object is the shorter its name could be, potentially consuming all the shorter name spaces with rare objects rarely talked about or referenced.
* Proximity: dozens or hundreds of red dwarfs in close proximity would all have nearly the same name without higher granularity of location encoding. Similarly, if higher location granularity constitutes a significant portion of the name, objects of different categories or types may all have similar names due to their location.
* Higher granularity of any sort may translate into impractically long names, and long names with minor differences that could escape notice or cause confusion.
* Potentially any possible combination of phonotactical rules could be considered so far as they do not contradict and are somewhat easily decrypted. Encoding methods need not be consistent from category to category or within categories.
* As per our existing naming scheme, multiple gravity-bound objects might be distinguished by a second (or higher) order designation; e.g. Alpha Centauri vs. Beta Centauri (two different trinary systems [distinguished by brightness](https://en.wikipedia.org/wiki/Bayer_designation)), and Alpha Centauri A, B and C (three stars within the Alpha Centauri system). How this intersects with the above encoding needs to be resolved.
* Convention may allow for exceptions, including but not limited to:
+ Relationship to other objects. Drawing from the point above, the most massive star in a multi-star system may lend its name to all stars within that system, overwriting the encoding in their names and demoting them to an affix, e.g. (DominantStarName) (∅; class encoded in name), (DominantStarName) (ClassK), (DominantStarName) (ClassM). This is only a partial solution as two or more stars in a system may be the same class.
+ Significance itself. Objects deemed to be of little to no importance may be relegated to a separate naming scheme that ignores or encodes information differently. E.g. the nearly invisible wisps of a disintegrating supernova remnant on the far side of the galaxy might be named in such a way to indicate it is a nebula-category object, then given an index number instead of further level of detail. Whatever the convention used, the naming scheme would have to allow for *any* object to be promoted from or demoted to this status, **so a numeric scheme is not in itself a solution**.
* The (C)V syllable structure could be reconsidered, allowing (C)V(C), (C(CL))V, (C(CL))V(C), or even (C(CL))V((CL)C). (L for Liquid, which I will consider "r", "l", "y", and "w".) Compare the combinations per single syllable:
| Syllables | Count | Cx × CLy × Vz | Combinations |
| --- | --- | --- | --- |
| CV | 1 | 251 × 40 × 151 | 375 |
| CCLV | 1 | 251 × 41 × 151 | 1,500 |
| CVC | 1 | 252 × 40 × 151 | 9,375 |
| CCLVC | 1 | 252 × 41 × 151 | 37,500 |
| CCLVCLC | 1 | 252 × 42 × 151 | 150,000 |
*Note: This does not exclude onsets like "rr", "yl", "wl", "ww", etc.*
* As noted in the comments, vowel clusters (not to be confused with diphthongs or triphthongs; each vowel phone is pronounced) would also be valid in (C)V, so in addition to the ~300 billion of VCVCVCVCV we'd have another ~12 billion:
| Syllables | Count | Cx × Vy | Combinations |
| --- | --- | --- | --- |
| VCVCVCVV | 5 | 253 × 155 | 11,865,234,375 |
| VCVCVVV | 5 | 252 × 155 | 474,609,375 |
| VCVVVV | 5 | 251 × 155 | 18,984,375 |
| VVVVV | 5 | 250 × 155 | 759,375 |
That is orders of magnitude more name space, potentially, though it would require more finessing to ensure pronounceability.
* Taking some of the above to an extreme, perhaps the solution is to externalize nearly everything about an object in the form of category, and retain a minimal core necessary to "name" it:
+ [Category of Object] [Subcategory within Category] [Type within Subcategory] [Idiosyncratic Core Name] [Location Information]... Some of these could be quite short, even single syllables.
+ This might sidestep *some* issues but 300 billion red dwarfs may still require hundreds of millions of names being duplicated hundreds of times.
**Question**
Can this idea be made to work (and if so, how), or are the numbers simply against it?
[Answer]
**Name by coordinates?**
Break space up into cubes such that no cube contains more than one star. If there are 4 billion stars assume 4 quadrillion cubes. Many are empty.
Consider xyz coordinates such that each cube has an individual xyz. The cube root of 4 quadrillion is 158470. Each coordinate line would run from 1 to 158470. So each cube would have 3 6-digit coordinates. Some of these would be the name of a star.
But we have more digits to use! If the coordinate lines go from 1 to 999999 there would be slightly less than a million trillion cubes. More than enough for a measley 4 billion stars.
You want language names. Fortunately you have 10 vowels and 25 consonants. Each digit corresponds to a vowel. Each digit corresponds to 2 consonants.
[](https://i.stack.imgur.com/fXvTW.png)
A star is at coordinates 916392 916392 916392. Consider the 6 digit string 916392.
[](https://i.stack.imgur.com/evm9N.png)
All of these 6 letter names are 916392. I am partial to Xaydle because it sounds like a name from a Piers Anthony book. 3 of these 6 letter names can name any of the million trillion cubes. 916392 916392 916392 could be Xaydle Laydxp **U**ahd**U**c. Or Xaydle Xaydle Xaydle if you dig that more. It is the same block.
Given that each 6 digit coordinate has 729 possible names there are 729^3 = 387420489 possible different names for the same cube. Then you can choose which names you use according to other properties. For example you could have blue giants have first names with all vowels - so if 916392 916392 916392 were a blue giant its first name would be **U**ayi**U**e.
[Answer]
You might want to take a look at [what3words.com](https://what3words.com).
They built a mechanism to describe any properly aligned three meter square on Earth by a set of three (English or others) words.
This further has the property that adjacent squares are not named anything similar.
The mapping is fully reversible.
(I don't know if the mapping algorithm is published.)
This idea, combined with your phonemes and syllables, could allow for unique naming of everything.
This would also let one use only one of the words as a short "convenient" name for a nearby star,
though one would need a local star-chart to find it from the short name.
# Proposed Method
1. Build a method to represent the location of a star (or other thing) in the galaxy. A coordinate system.
2. Combine the coordinate with a type indicator (star, nebula, etc...) and any other required information.
3. Represent this as a small bit vector. Ideal sizes are probably 256 or 512 bits, but the smaller the better.
4. Encrypt this value with a symmetric encryption, using a known fixed key. (Actually, for military use, one might have alternate key(s) so they get different names.)
5. Take the resultant encrypted value, split it into a number of approximately equal size values. Each one will become a "word". This could be 8 values in the 0 to 4294967295 range, or 7 in the 0 to 102116749982 range, or anything else that works for you.
6. Take these n values and look them up in a dictionary (or n separate dictionaries if you wish) to get a word for each part. This is your name.
For one dictionary, one probably takes your table of permutations and numbers the entries sequentially. For multiple dictionaries, they would presumably go one to the first, one to the second, etc. Either way, one can translate the number to the word and vice versa algorithmically. (What3Words apparently uses tables, as they want real words.)
One advantage to separate dictionaries for each word: if somebody gets the order wrong, it still decodes properly. (What3Words uses one dictionary, word order matters.)
It is important to note that every step listed is fully reversible. This means given the name, you can get the coordinate.
[Answer]
## Stellar Classification
**Mass**
You can simplify stellar classification by just referring to objects by mass. Classifications: "brown dwarf", "red dwarf", planet can be inferred.
For a galactic scale, you'd want Sagittarius A\* on the high end $10^{36}$kg, the sun in mid-scale $10^{30}$ kg, planets $10^{24}$, dwarf planets $10^{22}$. I'd recommend using logarithms to shrink these scales. You don't care, I think, about precision here.
You could do log-base-10 and exclude everything below dwarf planet for a cost of 14 slots -- well within your vowel (15) or consonant (25) budget.
**Temperature**
If mass is insufficient alone to glean type, you can also include surface temperature. Here, precision is important. Sirius at the high end is 10,000 K; the Sun is 6,000 K; and a red-dwarf is around 3,000 K.
You could do surface temperature in units of 1000s-deg-K for a cost of about 10 spaces in your budget.
Examples: 'Ba' might be a cold dwarf planet. 'Zu' could be Sagittarius A\* (the black hole at the center of the galaxy).
**Chemical Makeup**
Not in the original question, but for a few syllables you could add the top 3 chemicals (by percent) making up the body. 99.95% of the universe is composed of only ten elements (H, He, O, C, Ne, Fe, N, Si, Mg, S). At the cost of one more phoneme, you can include mass-fraction. With 15 vowels to choose from, your resolution can be 6%.
Examples: 'Zaby' is an extremely big, cold, dust-cloud that is 100% made up of hydrogen. 'Bahy' is an iron rock.
Chemical composition can help differentiate similar bodies:
* Uranus is 'Fabuca' ($10^{25}$ kg cold 83% H / 10% He),
* Neptune is 'Gabuce' ($10^{26}$ kg cold 80% H / 20% He)
## Location (absolute, last sighted)
Everything about location of celestial bodies is encoded in three parameters : distance (from some established point), latitude (relative to some meridian), and longitude (relative to some meridian).
You only need 180 degrees of latitude ($\pm$ 90) + 360 degrees of longitude. You can fit 360 degrees of longitude in your 26-consonant range by compressing them into 13$^o$ per consonant. 13$^o$ each works for your vowels as well.
Example: 'Bakyna' may be a a silicon rock on the galactic plane (0 latitude) at 150 degrees longitude.
Maybe an accent or a pause breaks up what-it-is from where-it-is : Baky'na, for example.
**Distance**
The galaxy is almost $10^{18}$ kilometers in diameter. As with mass, you can encode distance logarithmically and fit the whole range in the space for a consonant.
Example: 'Bakynac' is near the galactic core, on the galactic plane, at 150 degrees longitude. 'Bakynaw' is at the same latitude and longitude, but at the galactic edge.
**Precision (alternative encoding for lat/lon/distance)**
At the cost of one more consonant-vowel pair, you can have two degrees of precision. Both are expressed as [Knuth's up arrows](https://en.wikipedia.org/wiki/Knuth%27s_up-arrow_notation), which allow you to compactly get around the number line.
Examples:
Zyzyzy = $(20 \uparrow 6) \times (20 \uparrow 6) + (20 \uparrow 6) $ roughly edge of the galaxy at a resolution of ~1 light-years. For comparison, 'W' on the logarithmic scale only cost a single consonant, and had a resolution of ~50,000 light-years.
**When Last Sighted**
Everything in the galaxy moves. So, it's very important to know when 'Bakynac' was named. But this might be additional detail beyond the naming scheme.
**Velocity**
Everything in the galaxy moves.
Velocity, like position, is a vector that can be cast in latitude, longitude, and radial components. Velocity (the sum of the squares of latitude, longitude, and radius) ranges from -c to +c.
You can use logarithms to get the components to fit in your symbols.
Example: 'Dakynazyba' is a rogue planet made of glass on the edge of the galaxy, 0 latitude / 150 longitude, and is heading straight for the galactic core 'zba' at the speed of light.
The long name 'Dakynazyba-1980' might let you know that this planet was last measured in galactic year 1980 (whatever that means).
## Changing Names
Provided a higher precision database to get the details lost in naming, you can follow along as the position of a planet evolves over time. The celestial mechanics seldom changes. But in the event something greatly changes the predicted course, like passing close by a previously unknown body, the name can be changed.
] |
[Question]
[
[Alastair Reynolds](https://en.wikipedia.org/wiki/Alastair_Reynolds) is a contemporary sci-fi writer whose works often demonstrate a strong grip on science as it presently stands. Recently, I picked up his book *On The Steel Breeze* for a quick re-read of the first few chapters and stumbled across something interesting:
>
> Chiku barely glimpsed the fishermen busy on the deck as the flier sped past, fussing with nets and winches. They never looked up. The aircraft was tidying up after itself, *dissipating its own Mach cone so that there was no sonic boom*.
>
>
>
(excerpt from Alastair Reynolds' novel *On The Steel Breeze*, the italicized text my own emphasis.)
Now, for his unique style, Reynolds rarely features concepts such as this unless they've some conceptual basis in actual reality and known science. (Actually, this is not uncommon in sci-fi at all—in most cases, adapting magic-like technologies on theoretical, scientific bases is what *literally makes* the genre.) So, it had me wondering, **Conceptually, what would be required to "dissipate" a supersonic aircraft's Mach cone? Is it at all possible? And if not, why is it so?**
I've done some digging and apparently research into quieting sonic booms is quite old, starting way before Concorde property damages. In retrospect, quiet supersonic jets have military applications, so of course, it would've been R&Ded. NASA has [had a good go](https://en.wikipedia.org/wiki/Quiet_Spike) at it, developing this spike apparatus that reduces the decibel value of sonic booms produced by an F-15 by an appreciable percentage.
There are many examples of apparatuses and designs that reduce sonic booms, but not so many that "dissipate" booms, or make them inaudible. That is our purpose: to fly our supersonic flier over the heads of people on the pier without their noticing.
**Notes:**
What is a sonic boom anyway? Simply put (*simply*, because I'm no expert), a sonic boom is the abrupt increase in pressure of a passing [shock wave](https://en.wikipedia.org/wiki/Shock_wave). Shock waves are created when an object moves through a material faster than the speed of sound in that material. How do you dissipate a shock wave? Well, I don't know. It appears (at least to me) that in order to "dissipate" a shockwave, one would need to decompress the air of the surrounding Mach cone, returning it to normal pressure and temperature—presumably in a fashion that doesn't produce *another* shockwave and Mach cone to tidy up.
However, [it](https://en.wikipedia.org/wiki/Components_of_jet_engines#Subsonic_inlets) [is](https://en.wikipedia.org/wiki/Mach_reflection#Introduction) [known](https://en.wikipedia.org/wiki/Grumman_F-14_Tomcat#Engines_and_structure) that one can *reduce* a shockwave by decreasing its abrupt pressure change using an [oblique shock](https://en.wikipedia.org/wiki/Oblique_shock), which is basically just throwing a wedge into the incident fluid stream, compressing it. NASA has also shown that shockwaves can be reduced by employing [longer fuselages](https://www.nasa.gov/topics/aeronautics/features/sonic_boom_thump.html).
---
I have given the question the reality-check tag, so any answer to the question will either propose a method and back it up with scientific intuition or research, or explain why such a thing is impossible with science as we presently understand it, similarly with scientific intuition or research to back it.
Because the word I've been using—"dissipate"—is somewhat vague, let's use the term qualitatively.
[Answer]
There's no known way to dissipate the shock cone after it's left the vehicle. That's due to the locality of physics... effects happen proximal to the things causing those effects.
However, there is some prior art. [Busemann's Biplane](https://en.wikipedia.org/wiki/Busemann%27s_Biplane) is a great example. Basically the design captures the shock wave internally.
>
> Busemann's Biplane is a conceptual airframe design invented by Adolf Busemann which avoids the formation of N-type shock waves and thus does not create a sonic boom.
>
>
>
[](https://i.stack.imgur.com/uF5Ozm.png)
'Course it doesn't generate any lift, but it does show how the idea could work. There's apparently been *some* looking into using the shape for ammunition (I don't have a link to the paper, sadly). It's interesting not just for its sound dissipation, but also because it has the minimum wave-drag possible, so it can fly farther.
] |
[Question]
[
**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 was curious about an odd effect I first saw in video here:
[YouTube : Copper's Surprising Reaction to Strong Magnets](https://www.youtube.com/watch?v=sENgdSF8ppA)
In the video, a big heavy magnet is brought to an abrupt halt by a simple piece of copper. The effect is called Lenz's Law : an increase in the magnetic flux is created by the approaching magnet. The metal naturally resists the increasing magnetic flux by producing an almost equal and opposite magnetic field. The net effect is that the incoming magnet/projectile is halted before it can do harm.
Can Lenz's Law be applied to deflect or shield from beams of charged particles? From a world building perspective, could a primitive people fend off high-tech invaders armed with charged particle weapons by using metal to deflect the beam?
[Answer]
**Yes, but you would need to generate a really strong magnetic/electric field.**
Plasma *can* produce its own magnetic field if it is observed during a time-frame in which there are electrical currents present. Another mechanism that could be used by plasma to generate a magnetic field would be the concept of "plasma instability." Plasma instability is when some form of free energy (any form of [first law](https://en.wikipedia.org/wiki/First_law_of_thermodynamics) energy that can perform thermodynamic work, i.e thermal energy) is introduced into the system causing instability. The system will sometimes respond by converting that free energy into electromagnetic energy by releasing an electromagnetic wave.
Now normally the generated field would flow in all directions and cancel itself out, but assuming the plasma is being fired like a projectile in one direction, we can assume that all of the fields would follow the same direction and not cancel each other out. And lets assume that it's headed towards you.
**What can I do about it?**
By primitive, I assume you mean at least with modern human technological capabilities. Well if you wanted to deflect plasma, you would have to introduce a lot of energy into the plasma cloud flying at you. The best way to do this would be to point and fire a [high-powered laser](https://en.wikipedia.org/wiki/Tactical_High_Energy_Laser) at the cloud, and wait for it to generate an electromagnetic field. Then you would have to be wearing some form of protective armor that creates a powerful magnetic field that moves in a direction to repel the magnetic field created by the plasma. Why powerful? You don't want any plasma touching you as it would probably be at least 1000 degrees C. So it would be best to repel it all as fast and as far away as possible. You'd probably then want neodymium or samarium-cobalt which are the two types of rare-earth magnets. However, they are [extremely heavy](https://www.aqua-calc.com/calculate/volume-to-weight/substance/neodymium) with neodymium being the lighter of the two. With current human technology, it would be unfeasible to make a relatively cheap form of ultra-magnetic armor for a person to wear into battle against a plasma gun equipped alien race.
**Lenz's Law**
Rare-earth magnets aside, what about electromagnetism as described in Lenz's Law? Well all electromagnets operate on the principle that the more electromotive force(emf) A.K.A voltage is introduced, the stronger the magnetic field would be in the opposite direction of the original magnetic flux. What does this mean? It means that the more power, the stronger the repulsion/attraction. To achieve a similar repulsion to a 1 foot in diameter
and 1 inch thick circular neodymium plate, of the lowest magnetic quality of neodymium, you would need to apply 409.278 Amps of current to an electromagnet coil made of copper with 500 turns. Why copper? Because it's the second most conductive metal behind the expensive silver. It is heavier than neodymium, but the advantage an electromagnet is that we don't have to use as much metal. We only need to wrap the armor with copper coils able to safely carry 450 Amps of current, which while still being heavy is about half as heavy as the 400 pounds of neodymium. But 410 Amps is a lot. And it's not cheap either, powering this armor for 12 hours a day in the U.S for every day for a year will run you $90,570.31 for just *one* set of armor. And that's not to mention the cost of production. But if money is no object, then it is not only possible, but feasible in terms of combat.
**Is there any way I can stretch this?**
Fallout power armor is an example of how extremely heavy armor could be used for battle, but it's definitely not primitive as far as technology goes. If it is a more futuristic setting, then the possibility does arise for neodymium/heavy armor to be an option. However, while it might not be 100% suitable economically for single soldier use with modern technology, it could be used on a larger scale for buildings and even planets against alien invaders for a civilization with the same technological knowledge as humans. The inhabitants of the building/planet see the plasma flying towards them, so they use an even more [powerful laser](https://en.wikipedia.org/wiki/MIRACL) to bring the plasma bolt/cloud into instability, then using either an electromagnet or the planet's own magnetic field to deflect the plasma.
**No Magnets**
Without magnets it would be hard to deflect plasma as there isn't really any better options. Lenz's Law is directly tied to and helps describe the relationship between electricity and magnetism as originally proposed by Michael Faraday's law of induction. In a way, the plasma can charge the copper by introducing a current and making it an electromagnet for an extremely short period of time as the current would transfer, but by then it would be too late to save anything that someone was trying to protect. As again, plasma is hot, and would vaporize things once they got that close. Hypothetically, even if the copper wasn't vaporized by contact, the induced emf to the copper wouldn't produce enough magnetic force to push the plasma away, as if we follow the formula F = (n x i)2 x magnetic constant x a / (2 x g2) using the same dimensions of the electromagnet design I previously described, we would get a much lower repulsion on the plasma as unless the instability on the plasma was massive. However, given enough turns on the copper electromagnet, you could definitely use the charge on an unstable moving system of plasma to create an electromagnet powerful enough to repel it, but for a split second it is definitely still an electromagnet. This is of course assuming the coil itself isn't vaporized by the plasma as it touches.
**Plates?**
Plates are extremely impractical in terms of electromagnetism as plates are rather limited in the amount of length that they can add to the electromagnet. Coils make electromagnets more powerful.
**So is it possible at all?**
Yes, but you can't rely on the plasma providing enough current to the copper without vaporizing it. In order for it to work, you **MUST** have some way to prevent the copper coil from being vaporized. The only way to make sure that the coil isn't vaporized is by running enough electricity through it to create a magnetic field to repel the plasma before it gets too close.
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[Question]
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*(This question is not about getting scrap metal out of orbit and recycling it: please see the second and third sections of the question text.)*
Consider an object which was not designed for, or has lost its capacity to perform, atmospheric reentry (for instance: a space station or part of it, a spacecraft with failed propulsion), in orbit around a planet. Suppose now that the residents of the planet’s surface decide that it is desirable to have the object be brought, (mostly) intact, to the surface.
What would seem like a reasonable way to achieve this?
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The relevant setting is near-future-ish, but post-cataclysm: the predecessors of the surface dwellers had the capability to deploy extensive infrastructure in space, and performed interplanetary travel. The technology presently available to the recovering civilisation on the surface is recognisable as modern day, maybe plus a couple of pieces of handwavium gadgetry. The surface dwellers are not capable of reproducing the Magical Space Drive™ that enabled commonplace spaceflight for the predecessors, but they would know enough, for instance, to repurpose a spacecraft engine retrieved from orbit to be used as a power source.
The constraint on technology level is important, since it would not make sense if the surface dwellers could, at a lower cost, instead manufacture things on the surface that serve the same purpose as the salvage. This rules out sending a re-entry-capable cargo ship up, loading the stuff in, then flying it back down. However, it is also required that they be able to send things to a sufficient altitude at least momentarily, for them to be able to carry out the salvage operation in the first place.
The closest thing I could come up with was for someone to launch themselves into orbit, bringing with them thruster modules (perhaps plain chemical rockets) that would then be attached to the target, and be used to decelerate it and commit it to deorbit. However, I know of no robust way of modifying arbitrary satellites to enable them to survive re-entry.
Additional information that might be relevant:
* The operation is routine, but does not need to be indefinitely sustainable. If necessary, the surface dwellers might make use of technological relics found on the surface: for example, they expend one Magical Space Drive to send a crew up, expecting them being able to bring back at least two Magical Space Drives. Alternatively, they might make use of any infrastructure put in place by the predecessors that has survived the cataclysm and the subsequent lack of maintenance and remains sufficiently operable.
* It is preferred for the planet itself to be as similar to Earth as possible, but if the bottleneck to this question turns out to be planetary mass, atmospheric composition, or something along those lines, those parameters may be changed.
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I’m aware of several questions dealing with related subjects, but have been unable to piece from this information a complete solution to the present question. Links are left here for reference, and for the purpose of highlighting the differences of this question from similar ones.
* [How to efficiently deorbit space junk](https://worldbuilding.stackexchange.com/questions/83543/how-to-efficiently-deorbit-space-junk) has some creative solutions for de-orbiting without requiring much futuristic technology; however, the question deals only with the matter of removing space junk from orbit, allowing it to burn in the descent. The present question requires that the de-orbited object to be returned to the surface mostly intact.
* [Would ablation be an effective way to redirect objects in space?](https://worldbuilding.stackexchange.com/questions/40325/would-ablation-be-an-effective-way-to-redirect-objects-in-space)
examines an alternative way to impart delta-V, but similarly does not treat the issue of re-entry.
* [How can I catch an asteroid](https://worldbuilding.stackexchange.com/questions/45614/how-can-i-catch-an-asteroid) asks the same question, except aiming to capture asteroids instead of artificial satellites. Several solutions involve destroying the asteroid beforehand for ease of transport, which is undesirable here where the objects of interest might be delicate technological artifacts. Other answers suggest use of a [space elevator](https://en.wikipedia.org/wiki/Space_elevator), which would be unavailable to the technology level required by this question. The option of using an elevator built by the predecessors leaves the questions of maintenance and operation of a space elevator without the capability of building one.
* [How to Effectively Collect and Recycle Space Junk](https://worldbuilding.stackexchange.com/questions/96930/how-to-effectively-collect-and-recycle-space-junk) deals with the collection and recycling of objects in orbit, but is performed near a body without an atmosphere and explicitly forbids de-orbiting. The level of technology considered is also far beyond the constraints of this question.
There is also [an xkcd post](https://what-if.xkcd.com/58/) that I’m sure is bound to be brought up at some point.
[Answer]
Astronautical engineer here, I'll try to take a shot at this.
As you should probably know from the related questions you linked, capturing and de-orbiting uncontrollable derelict satellites is extremely difficult and costly, and has been a subject of research and speculation since the late 1960s. To get them down to the surface in one piece, you have to contend with the following factors:
* Acquisition of the target to be salvaged, which requires the ability to match and change orbits and grapple with the target
* The intense heat of reentry, which is due to the fact that orbital speed is roughly 17,500 mph, whereas subsonic flight in atmosphere is between 680 and 750 mph, depending on altitude
* The dynamic forces of reentry, including aerodynamic buffeting and deceleration loads
* Vehicle control during reentry, which is essential to both hitting your target landing zone and preventing the vehicle from tumbling out of control and breaking apart under the dynamic forces mentioned above
* Landing site selection; landing in the ocean is easier but requires extensive support equipment and may damage your vehicle and salvage, landing on land requires much finer control and a much slower final speed
Capture of orbital debris is a [hideously complex science](http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/How_to_catch_a_satellite), and whole PhD papers have been written on the subject. But in simple terms, you need a way to catch the thing you want to salvage, stabilize it in some way so you can grab it, and then secure it for reentry. So your vehicle needs a supply of fuel and a full set of maneuvering thrusters to be able to change its orbit to that of the target and, once the target is captured, move back to the return orbit (which may or may not be the same as the launch orbit). Grappling is a real problem, as derelict satellites might be spinning out of control at relatively high rates. Your capture vehicle will probably need some kind of sensors to determine the axis of rotation, and then will need to maneuver along that axis to match the spin and grab it with a net or robotic manipulator. But then you have to slow the thing down, without hitting it or losing control yourself, which is no simple matter. Your maneuvering thrusters and/or reaction wheels will need very fine control, and your guidance system will need to be fairly clever. This isn't something that a human could do intuitively with a reasonable degree of safety.
During reentry, the vehicle is traveling so fast that the friction between its skin and the air dissociates the air molecules, forming a hot plasma. This both disrupts radio communications with the vehicle and imparts tremendous heat. However, handling the heat of reentry is actually not as big a deal as it first seems. The [most common method](https://en.wikipedia.org/wiki/Atmospheric_entry) is to use an ablative heat shield, typically ceramic or some Inconel alloy, to protect your vehicle. These are usually blunt by necessity for stability purposes, and can be very large (e.g. the Space Shuttle's entire belly was one giant heat shield). However, these things are difficult to make and, as you might imagine, there is no margin for quality errors. You can potentially reduce the amount of heat generated on reentry by using a hypersonic parachute or [retropropulsion](https://space.stackexchange.com/questions/17573/how-is-retropropulsion-by-the-falcon-9-first-stage-being-used-to-design-retropro) to kill most of your speed before you hit thick atmosphere, but these technologies don't completely eliminate the problem.
The act of using air resistance or retropropulsion to slow yourself down means you're in for a bumpy ride. You need to bleed off roughly 17,000 mph of speed in as short a time as possible (to avoid burning up), so you need to decelerate at between 1 and 5 times the acceleration of gravity, depending on your trajectory. Reentry also imparts a lot of buffet to the vehicle, which means very high-intensity vibrations. Most spacecraft are only able to handle high accelerations and vibrations in particular directions and in particular configurations -for example, with the solar arrays and antennas stowed in the folded position. You'll either have to return the vehicle to its launch configuration, or provide a means of cushioning it against vibration and acceleration.
Your descent vehicle will need a particular set of aerodynamic characteristics to remain stable during reentry. This could take the form of aerodynamic control surfaces like the grid fins on the Falcon 9, be derived purely from the shape of your vehicle, as with the Apollo capsules, or involve compressed gas thrusters. You also need a guidance system that can operate in isolation from ground control or any visual input; typically an inertial system using gyroscopes and/or accelerometers.
Once you're subsonic, parachutes are the simplest method for slowing down to the point of impact. If you're aiming for a water landing, you need some floatation devices to keep from sinking, but otherwise, you're done. If you want to land on solid ground, however, you'll need to deploy some kind of landing legs or gear (and may have to jettison your heat shield to do so) and you may need larger parachutes or some low-thrust retropropulsion to give a softer landing.
Given the above considerations, and the fact that this reentry vehicle has to be reusable, and the point is to recover random satellites for recycling, here are some suggestions that would make the job much easier for your salvagers:
* Consider making the salvage ship stay in orbit, with only the cargo vehicle and crew having to endure launch and reentry forces. This will make launches cheaper and reduce the wear and tear on your salvage ship (and the complexity of landing all that extra mass).
* Make sure the salvage ship has powerful thrusters and reaction wheels, plenty of fuel for big orbit changes, and a smart guidance system.
* Chop the satellite being recovered into small, manageable pieces that can be efficiently packed together. This way you won't have to worry about odd shapes, deployed features like antennas or solar panels, and irregular centers of mass.
* Enclose the salvaged satellite bits in a capsule or cargo hold of your reentry vehicle. This will allow you to control the reentry vehicle shape and center of mass, rather than having to accommodate oddly-shaped salvage, and it'll protect the salvage from the hot plasma during reentry.
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[Question]
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There was an orbital station; a huge torus, as known from sci-fi. It was a luxurious place for people from dusty planets to relax at, and spend hard-earned money in environments resembling Earth from the legends. Forests, meadows, hills, rivers and lakes. Everything powered by solar energy, protected from radiation by artificial magnetic field, and maintained by a horde of autonomous robots that would repair anything broken, repair each other if any of them breaks, and go into nearby space to hunt comets and asteroids to provide raw material for all the repairs (and fuel for more such voyages) in case they'd be running low.
*Something* happened, and the human population abandoned the station, leaving *almost* all the autonomous systems running. Someone, maybe in a fit of wry humor, switched "ecosystem regulation" off (while leaving maintenance; water, humidity, temperature etc), so it would no longer be artificially maintained at status quo, but could evolve, and also disabled the spin motors of the station.
The station took a couple thousand years to de-spin due to tidal forces, the artificial gravity gradually dropping to zero. Meanwhile, the ecosystem thrived in the changing conditions, allowed to "run wild"; robots faithfully maintaining the infrastructure, bringing resupplies of air in place of leaks, fixing breaches from meteorites, etc. And the ecosystem (oh, pick anything you like that is reasonably varied, say, moderate climate forests, or African savanna, just please, not "bottom of Pacific"), kept evolving, adapting to the new conditions.
The station is "rediscovered", say... 100,000 years later. How will the different classes of species (predators like wolf or leopard, larger herbivores like deer or antelope, small herbivores (rodents etc), birds and insects look like? Or will one or more class of these go extinct?)
[Answer]
My own exploration into this (which is how I came across this question) shows a bias into climbing and swimming adaptations. Animals that have grasping paws are able to grip onto areas of the station, allowing them more control over their location. Swimming adaptations allow the animal to move and control their location in a low-gravity environment without relying on pushing off of the walls.
Flying adaptations are also useful, but their surface area will likely decrease due to the lack of gravity (as the density of the air remains pretty much the same). Swimming adaptations (such as fins) may increase in surface area to compensate for lower density, but as there is also much less drag that is uncertain,
Longer limbs and necks will likely be selected for higher ease when capturing food and water (as both will float in this environment)... If the fans are off, there might also be adaptations around the head area to prevent Carbon Dioxide or other gasses from building up & suffocating the creatures.
Less energy/muscle mass is needed to function in this environment, which may prompt larger animals. Said animals will also likely be fairly flexible to allow for turning in mid-air.
Other then this I'm unsure as to which adaptations will be needed. I focused on the physical/visible changes rather than the changes in behaviour (to which there'll be many) but this should hopefully give a general idea.
[Answer]
See: [link](http://www.scientificamerican.com/article/how-does-spending-prolong/)
I think the outcome looks bleak. Assuming all base life support holds ...
**The biggest hurdles to overcome are**
* Loss of bone structure, resulting in osteoporosis.
* Loss of muscular structure, including potential heart problems.
* Fluid distribution is difficult, which leads to issues long term.
* ...
**So, who lives**
I would think invertebrates have an advantage, so maybe squid- and jellyfish like creatures? Snails, that sort of thing.
Insects with a hard exo-skeleton would also be ok, I guess. So beetles and the like.
Maybe soaring birds who don't need a lot of muscle action to keep going? That's assuming there's enough atmosphere left to have lift.
**UPDATE**: Apparently birds are [in trouble](http://www.mirror.co.uk/news/uk-news/astounding-animal-facts-bird-cant-3187087), because they depend on gravity to swallow their food.
**So, who dies**
Pretty much everyone. Minimal or close to zero gravity has effects that make sustainable live practically impossible.
*PS: I'm not a (bio)scientist, so take this as the (non-educated) opinion that it is.*
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[Question]
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To narrow this down, I'm looking only for climactic specifications. Not cultural responses, etc.
During [Ernest Shackleton](https://en.wikipedia.org/wiki/Ernest_Shackleton)'s expedition to the Antarctic continent, he found a huge canyon/crevasse that spanned a very large area of tectonic activity. In fact, with hot springs, volcanic activity and geysers, it remained a humid subtropical and temperate tropical version of Yellowstone or [Gobustan](https://en.wikipedia.org/wiki/Gobustan_National_Park).
This area was protected from climate changes over millions of years and still boasts the remnants of the Cretaceous Period. Due to heat from the planet, it maintains a humid and humid-subtropical climate to have allowed ancient plants and animals to thrive.
In a magnitude of order (no hard science needed), **how big should my sheltered canyon or basin be, in order that Mr. Shackleton has stumbled upon dinosaurs and ancient plants, that were able to survive in a 'biome' for 66+ million years?**
*Post Script: I know this to be impossible; I'm asking only for the physical size, in a magnitude of order, needed to support such a large ecosystem over 66+ million years in an Alternate History story.* Are we talking, "The Whole Continent," or can we have a good "Thousand Acres," et. al.
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I don't care if the dinosaurs have evolved a bit. I want Shackleton to have stumbled upon a Cretaceous remnant that includes 'dinosaurs'
[Answer]
There is no chance a reptile will be able to survive the cold of antartica - even in a sheltered valley - without some kind of heat source.
Let us assume that the valley is heated by a series of hot springs which come up and form a river which runs end to end. The heat of these hot springs can be above boiling temperature - which would provide a humid environment that can fill the open-topped valley. To prevent contamination from external organisms, the river runs out to sea via a crevasse and is dug deep into the rock with steep, sheer sides.
Looking at the dinosaur population from the point of view of a food web, your ecosystem will need some manner of food source to maintain it. It's possible that there is some sort of algae or seaweed that has evolved to live off the steam and low-light conditions of the hot springs - and perhaps some plants that were introduced in the dung of migrating dinosaurs.
For large sauropod dinosaurs, I've looked up the home range (where it browses/forages for food) of the giraffe which would have a similar diet and walking speed - and it can reach roughly 160kms (99 miles) or 25600 square km (9801 square miles).
With the assumptions:
* the valley must be narrow enough to contain the steam
* wide enough for any plants that need to photosynthesise to gather light
* wide/complicated enough for herbivores to avoid predators
Your valley could be 3 miles wide and 3267 miles long. (3.737 times the length of the United Kingdom)
Picture for comparison with Australia in there for good measure:
[](https://i.stack.imgur.com/1c2iH.jpg)
Remember, your valley could be wider and narrower in places, riddled with caves and be a tangled, winding shape as is natural for gullys cut by rivers. If this were the case, it could easily fit within the silhouette of the UK.
In actuality, this would not be such a stretch of the imagination and could, potentially, exist were Antarctica a little closer to the edge of its tectonic plate.
[Answer]
I would proceed like this:
* Figure out what the **biggest dinosaur** is which you want to be found in this biome.
* Figure out what its [Minimum viable population](https://en.wikipedia.org/wiki/Minimum_viable_population) is. (If you don't find values for this by googling it, I'd just take the largest related currently living carnivore/herbivore you can find.)
* Calculate how much area you would need per individual of said race of big dinosaurs. (Again if Google doesn't yield anything I'd look up values for elephants/giraffes/tigers/... and scale them up.)
* MVP times area-per-individual will give you the minimal size of your biome to support a stable long term population of your biggest dinosaur.
You can generally assume that the smaller species will need less area and can thus easily have stable populations within the same area.
[Answer]
I say the size of large city like New York or London . But that just a guess. The are numerous islands small then that and they are self sustaining. Your area would be bigger because of the need to accommodate the dinosaur.
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[Question]
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In mammals - and that includes us humans - the lungs make up 7% of the total body volume. This allows us to inhale oxygen and exhale carbon dioxide, thanks to the pulmonary alveoli.
But bird lungs are unrivaled. They make up 15% of the total body volume. Gas does not mix between in- and ex- halation.
If we humans have a unidirectional respiratory system like a bird's, how would it affect the following?
* Athletics
* Vocalization
[Answer]
**Athletic performance would obviously be improved though we might sound a bit different**. Birds are able to fly for such extended periods of time because their aerobic capacity is so much higher than mammals.
Humans with continuous breath so pausing for a breath on an extended soprano high note will be a thing of the past. There won't be a distinction anymore between whistling while breathing in or breathing out since the vocal cords will be serviced by the outgoing trachea.
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[Question]
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In a new self-sufficient human colony, what are the minimum requirements of the local environment (i.e. what resources would it need) for long-term survival?
Let's suppose that the colony land on something similar to a desert (sand desert or cold desert, whatever) with a limited amount of natural resources. I assume they have at least access to unlimited breathable air and clean water source. They also start with the current human knowledge and enough supply for the first generation of humans (but no seeds and no animals).
In order to survive (i. e. avoid extinction in the next decades/centuries), what is needed in the fauna and flora of this desert? Can they survive without any birds, fish or mammals (reptiles or insects only for example)? How many differents kind of vegetables and fruits do they need?
They don't have to live a healthy life, just enough to reproduce, raise new children (even with a high infant mortality) and perpetuate the human race.
[Answer]
I feel like this is almost impossible to answer. It's just too broad really.
**Let's suppose that the colony land on something similar to a desert (sand desert or cold desert, whatever)**
Ok. Well if it's a "sand desert", presumably comparable to the "sand deserts" on Earth, it's really, really hot and really, really dry. So they would need much more water than I would expect other colonies would need, and they would require something to keep them from overheating. That could be anything from housing with central A/C to cool clothing.
And if it's a "cold desert", presumably comparable to the "cold deserts" on Earth, it's really, really cold. So the opposite would apply -- they would need something to keep them warm, from central heating to layers of clothing.
I'm assuming they get clothes, but I'll get to that later.
**with a limited amount of natural resources. I assume they have at least access to unlimited breathable air and clean water source.**
In a "sand desert", they very well may not have access to an unlimited clean water source. Either way, "natural resources" can vary too widely to really predict what they would need. For example, assuming that they have sand and water, they could theoretically build sand-castle shelters, or more likely something adobe-esque. They probably even have access to real stone. But if it's a "cold desert" like Antarctica, they have to build something more like igloos instead. Same concept, but completely different resources. Lots of things can be made from earth or earthen materials that can't be made of ice, as ice tends to have a relatively low hardness on Moh's scale. It also tends to melt when you hold it, so most tools wouldn't be able to have ice handles, at least not for very long.
**They also start with the current human knowledge and enough supply for the first generation of humans (but no seeds and no animals).**
Enough supply of what? Food? Does "enough supply" also cover things like clothing, medicine, tools of any sort? Having seeds (and perhaps animals too) seems irrelevant, since most plants (and perhaps animals) probably wouldn't be able to survive in either a sand or a cold desert, given the lack of arable soil (and food/water for the animals).
**In order to survive (i. e. avoid extinction in the next decades/centuries), what is needed in the fauna and flora of this desert?**
The plants and animals of this desert would have to be things that could be easily domesticated, meaning that the humans would have to be able to understand them relatively quickly and control them well enough to control their population. Oh, and they have to be edible -- can't have things that kill us when we eat them.
Beyond that, the plants and animals of the desert would have to provide the group with any other materials that they can't get directly from the earth -- fibers and leathers for clothing as well as things like sacks, something sturdier (like wood, though that's unlikely in this setting, so probably bone) for use as tools, and kindling for a fire (if not for warmth, then for cooking).
**Can they survive without any birds, fish or mammals (reptiles or insects only for example)?**
In a desert, where I'm assuming trees are scarce, *maybe*. Without wood or bones (or stone in an Antarctica setting), you'd have virtually no tools. This also removes leather as an option for clothing (edit: unless you kill a *lot* of snakes), which leaves you relying solely on fibers of plants, which you would have no easy way of weaving together.
**How many differents kind of vegetables and fruits do they need?**
I can't really address this one, mostly because I don't even begin to understand the way ecosystems can work. As far as the human diet goes, I would assume they would only need one edible plant of which they could control the reproduction.
**They don't have to live a healthy life, just enough to reproduce, raise new children (even with a high infant mortality) and perpetuate the human race.**
While this has nothing to do with the minimum requirements of the local environment, I feel like *the number of people in your initial colony* would be immensely important.
If you started with just two people, for example, the chances of birth defects in future generations would be pretty high considering the tiny size of the gene pool. A colony like this may not be able to survive just because of that alone.
However, if you have many people, say 10, then you end up having to account for social aspects of the colony. Mostly there's the issue of who's *worth keeping around* and who isn't. Who is expendable, not only because they waste resources, but also because they *can provide* resources -- humans are animals too, after all, and animals can provide many things like bone, food, and leather. I would actually be willing to bet that you wouldn't need much of a local environment if your colony were willing to divide into two -- the humans and the animals.
[Answer]
Most recent attempt to do something similar was [Biosphere 2](http://en.wikipedia.org/wiki/Biosphere_2) in 1993 and ... there were problems. So it is safe to assume that we don't know yet how to do it using current technology in a 100% closed system. Interactions between parts of biosphere are complicated.
Another bunch of good studies are about Mars colonies like [Mars One feasibility study](http://web.mit.edu/sydneydo/Public/Mars%20One%20Feasibility%20Analysis%20IAC14.pdf). I read exact mix of plants they used but cannot find the link now. As it turns out, hydroponics works + sun is simple in theory but not as simple in practice. Here is what I found:
* [10 candidate crops](http://www.space.com/12919-nasa-mars-astronaut-space-food.html) that seem to fit the bill for astronaut food: lettuce, spinach, carrots, tomatoes, green onions, radishes, bell peppers, strawberries, fresh herbs and cabbages.
* [more info](http://www.space.com/9449-5-star-space-food-astronaut-cuisine-hits-lofty-heights.html) about mars cuisine
* [14 plants](http://www.popsci.com/article/technology/crops-grow-fake-moon-and-mars-soil) to grow on fake soil from Mars (volcanic soil of Hawaii) and fake Lunar soil (and how it failed). Even has a link where you can buy sample of that fake soils.
* [popular description of the soils ecosystem](http://www.slate.com/articles/technology/future_tense/2013/06/mars_colonization_may_require_earth_soil.html) - containing bacteria, protozoa, nematodes, insects, and much more, and how they interact.
[Space Exploration Exchange](https://space.stackexchange.com/questions/tagged/mars) might be better place to ask exact details. I found [many](https://space.stackexchange.com/questions/7711/will-human-colonisation-be-introduced-commenced-in-the-somewhat-near-future) [very](https://space.stackexchange.com/questions/6000/what-is-the-largest-hurdle-of-the-mission-to-mars) interesting reads.
**Getting the balance right is the tricky part** (and we don't know how to do it yet).
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In a world where priests can cast actual miracles, how would that affect the world's development? In particular, how would it alter the interactions between different religions? And how would these effects differ depending on the frequency of these miracles (i.e. certain high level priests can evoke them every so often, vs any priest can call on them virtually at will?)
Are there any areas besides religion that would be heavily influenced by such miracles? If so, how?
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**Religion**
Being able to call down miracles regularly and often is a trump card for religious factions in strife. A good example comes from the (Christian) Bible. See the story of [Elijah and the Priests of Baal](http://en.wikipedia.org/wiki/Elijah#Challenge_to_Baal) in the Bible.
If these miracles are too common, people will get used to them, and may not take them as miracles anymore. This is especially true if other religions can perform those miracles, too, as seen in the biblical account of Moses calling down the [Plagues of Egypt](http://en.wikipedia.org/wiki/Plagues_of_Egypt).
**Science**
Scientists would take the miracles as fact. Some could say "those are not miracles, [it's science.](http://en.wikipedia.org/wiki/Clarke's_three_laws)" Others could investigate these miracles and take a scientific approach to them, figuring out their laws and mechanics.
It would certainly give science a goal; to figure out why those priests can call down those miracles! This is, of course, assuming there is a division between science and religion in that culture.
**Philosophy**
If priests can call down miracles regularly or on-demand, and those miracles are taken as divine recognition of those priests, then that religion must be correct. No errant ideas or philosophies which counter that religion should exist, unless those philosophies can produce those miracles as well (via priests who subscribe to them). It would be a litmus test to see if those philosophies were correct or not.
**Economics**
Miracles on-demand would be demanded. Whatever these miracles can affect *would* be very different. This could lead to a market for purchasing miracles. The price would be determined by the availability of these miracles. People would come to rely on miracles the same way we have come to rely on modern technology. In some cases, the demand may result in people forcing priests to perform that miracle or face consequences.
If the miracle is common enough, why develop the technology to do it? Sure, you'd not be dependent upon a priest, but if those priests are everywhere, it may not be worth the resources to create that technology. That's the [opportunity cost](http://en.wikipedia.org/wiki/Opportunity_cost) of regularly occurring miracles.
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Hey I've been trying to map out some ocean currents for a planet I'm creating, called Kalmoren. I've been following an artifexian tutorial however he seems to split gyres based on the circulation cells (at 30 degrees then again at 60 degrees). When looking at maps of earths ocean currents they don't seem to follow this pattern instead having larger gyres that extend past 30 degrees.
My question is why are earth's currents different to Artifexian's and if the currents I've come up with are realistic.
Below is my map with currents mapped and the wind patterns in the background
[](https://i.stack.imgur.com/PQQZA.jpg)
And here is the world ocean currents compared with Artifexian's
[](https://i.stack.imgur.com/8y3Gr.png)
[](https://i.stack.imgur.com/eGF3V.jpg)
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There are two major drivers of oceanic circulation: the wind-based surface currents, and the temperature-based [thermohaline circulation](https://en.wikipedia.org/wiki/Thermohaline_circulation).
Artifexian's map shows pure surface currents -- something you might get from a freshwater ocean with no thermohaline circulation. Salt-driven density variations will shift, merge, and mangle these currents, producing the larger circulation cells seen on Earth.
[](https://i.stack.imgur.com/LuVTx.jpg)
For the most part, your circulations look realistic. I've highlighted a few things that seem problematic:
* Cyan: This basin isn't really large enough to generate flow distinct from the overall flow of the ocean. Depending on local circumstances, it may be a relatively stagnant pocket (eliminate the two southern arrows), or it may be a redirection of the larger circulation (eliminate the northern arrow).
* Green, magenta: This far from the equator, the Coriolis effect has a strong influence on the direction of flow. In order to get a counterclockwise flow in the northern hemisphere, you need a strong driver, and I don't think your polar current is enough to do it. More likely, the flow will be clockwise, and the polar circulation will be west-to-east.
* Magenta: There's no obvious reason for this circulation to exist. If you look at Earth, currents don't just spontaneously detach from the coast. You might get a situation like the Oyashio Current meeting the Kuroshio Current off the coast of Japan to form the North Pacific Drift, but in that case, I'd expect the point of detachment to be much further north, near the easternmost point of the continent.
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I'm working on a fusion rocket concept for a hard science fiction setting. I'm envisioning laser catalyzed Proton-Boron reactors (low waste heat, aneutronic, 100% of their output being He4 Alpha particles) based on [HB11](https://www.hb11.energy/) or [TAE](https://tae.com/)'s designs, but with two major drawbacks:
1) They must convert almost all of their particle output into electricity in order to break even, leaving only a small amount that can be used for thrust
2) The lasers themselves need to be replaced or refurbished after a few hours of use.
So when all's said and done, the engine performs more like a nuclear thermal rocket than a torch ship or an Epstein drive. Stylistically and tech wise, 'fusion but it's not that good' would fit my setting like a glove.
Plausible concept or dumb idea?
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This sounds plausible indeed.
Any engine can be abstracted as producing two things: thrust and waste heat. As an intermediate step, it can produce internal power, but said power will either be used for helping thrust, directly or indirectly, or will end up as waste heat due to other inefficiencies. (I am ignoring big third-party energy drains like, say, giant laser weapons.)
Here, most of the output is used for feeding the laser/particle beam/plasma that is keeping the reaction going. But this power isn't going anywhere: it is either used to move particles faster, or to heat things up (due to unavoidable inefficiencies, as waste heat). So you can simply describe your engine as being, say, 50% or 90% efficient. Which means that the remaining 50% or 10% remaining power needs to be dealt with. With a spacecraft that cannot use atmosphere, water or ground to evacuate heat (like an airplane, ship or ground powerplant would), this means [giant red-glowing radiators](https://childrenofadeadearth.wordpress.com/2016/04/25/why-does-it-look-like-that-part-3/). Which is a good thing! Radiators look badass, they convey the feeling of power well, they are a good visual cue for what is happening (cold radiators mean the powerplant is stopped, for example), they are a great source of plot and complication, and hard-SF fans will talk about how realistic your work is. In fact, the biggest mistake of *The Expanse* (both book and show) is probably to not have used them.
Now, propulsion is done by throwing particles as fast as possible in the other direction. The faster you can throw the particles, the longer the same mass of fuel will last you. Fusion drives are great for that: with their enormous power, they can emit particles at an enormous speed, and thus are very efficient. Unfortunately, they also have very low thrust, because a fusion drive will comparatively emit a low mass of particles per second - think better ion drives. Contrast with chemical engines that have a terrible efficiency (you need a whole Saturn V to send a tiny capsule to the moon and back), but have enormous thrust.
Note that, with the lack of radiators (implying an efficiency of 99.99% at least) this is why the Epstein drive is implausible (even if not physically impossible).
You can actually increase thrust with the same power by using more propellant, but as such each particle will be emitted at a lower speed (same power divided between more particles). So you have more thrust but less efficiency. You can even use your engine in maximum powerplant mode, and use the energy [to heat inert propellant](http://www.projectrho.com/public_html/rocket/enginelist.php#arcjet) (, thus having the thrust of a chemical engine for a slightly better efficiency. In fact, if you are in atmosphere, you can even use air and turn it into a jet engine. Do remember that even proton-boron fusion is somewhat radioactive and not quite aneutronic due to secondary reactions.
So for interplanetary travel, you want maximum efficiency, with longer, gentler burns. For manoeuvre down gravity wells, you want better thrust because short, harder burns are more important. Do play at [Children of a Dead Earth](https://store.steampowered.com/app/476530/Children_of_a_Dead_Earth/) if you want to experiment with this.
Your reactor can even be designed with this inefficiency directly: if it is too complicated to have a 100% fusion rate, maybe it uses much more hydrogen and/or boron than is ultimately fused, and the remainder is heated by the reaction and used for thrust along with the fusion results. So while [theoretical max specific impulse is very high](http://www.projectrho.com/public_html/rocket/enginelist2.php#hbfusion), maybe your engine has actually a lower one.
As for changing laser heads every few hours, this wouldn't have too much effect on the efficiency of the engine as such, being equivalent to a slightly less efficient one (the mass of the spare laser heads). However, it is a good way to make it feel like a high-tech, high-maintenance device, and opens things up for plot points and complications - again, a good thing. After all, we don't know the exact design compromises that go to a spacecraft fusion laser, so there is no reason for it not to feel believable.
And of course, [Atomic Rocket](http://www.projectrho.com/public_html/rocket/) is *the* website to go for when working on hard-SF.
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Lets call it - whack a mole fusion.
You give up on the idea of control on the process. And just whack at spikes of plasma coming near the edge of containment.
How this is done?
You use a set of lightning-rod lasers (<https://ec.europa.eu/digital-single-market/en/news/fet-open-laser-lightning-rod>) to 3d print a coil shape on the plasma of the emerging spike.
Once that spiral of fog is printed onto the inferno, you send current through, creating a counter turmoil, that compresses the plasma back into the containment region.
It needs great sensors, fast reaction times and its definatly wastefull and slow, with output constantly fluctuating.
In addition you can not control this whole thing and it could run hot in regions with constant magnetic fluctuation.
In addition its error prone- meaning a split second to late and the coil printed might already be distorted and shove the plasma into a unexpected direction.
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In a world I'm currently developing, I'm working on a merpeople equivalent (more or less physically identical to your bogstandard mermaids, for the purposes of this question), and I want them to wear clothing. I know there are plenty of arguments against the practicality of this, but regardless, it's an element I'd like to have.
For context: these particular merfolk breathe air, and can stay out of water for significant periods of time. They live in rivers, lakes, and oceanic bays alongside a ground-based civilization, and so there's some communal culture going on (or at least communal standards of fashion). They're a part of the economy and society of said civilization, which is at least at a technological level complex enough to manufacture dentures (I know that's oddly specific, but I think it sets the tone). In other words, the have access to a lot of materials and production they otherwise wouldn't.
I've thought about the issue a bit, exploring various options (they say seaweed lasts for ages without deteriorating, if you don't cut it, etc.), and I hit upon the idea of them using natural rubber (latex I think is the word?) for their most basic and functional garments. They say the Myans would dip their feet in it to make shoes, and I wondered what the practicality would be of a mermaid bathing in latex up to the neck, letting it dry, and then cutting / peeling it off and devising some means of fastening it. Would this be a good way to make a waterproof suit? Even just an undergarment or something along those lines?
Thoughts?
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Yes, I think this is total feasible. From a materials perspective natural rubber (which is *derived* from latex) is easily up to the aquatic environment (it is often used to make wetsuits). Here are my thoughts on how this would work for various types of clothing.
First, you need to harvest the latex. Many types of plants produce latex, it's actually moderately common. If your world is set on an alternate earth, feel free to read about latex-producing plants and pick the one you think would best suit your needs. Otherwise you can just make up a plant to produce your latex: it's common enough that I don't think anybody would question you.
Now, there are a couple ways you could go to actually make the clothing. One is to make form-fitting clothing, as you mentioned. There are some issues with this, but I think it's workable:
1. You don't want the latex to adhere to the body once it has formed into a rubber. This is easily solved with some kind of body lubrication.
2. You need to allow the latex to dry without rubbing it off. This would is a little tricky. For a human, I would say they could stand there until the layer is cured, and then re-dip their feet to fix the part that was messed up by standing. Something similar might be possible with mermaids if they can stand on their tails well, otherwise you need another solution. Perhaps solving this suggest a different application method (perhaps it is painted on in sections, instead of dipping the whole body at once).
3. As mentioned by Kaiannae, the suit will be hard to get back on once the wearer is cut out of it for the first time. This could be ameliorated by cutting the clothing into sections and then binding them back together less tightly, but this eliminates the main advantage of this type of form-fitting clothing (namely, the ability to hold a water layer near the body, providing insulation from cold waters). It may also be solvable using the same body lubrication as from (1).
4. This is less of a technical problem, but one of the main purposes of clothes at least in human societies is to outwardly display something about the wearer, be that their individuality, a group identity (i.e. uniforms), or some personal trait. Clothing made in this way would have less potential for fashion or decoration than a more "traditional" type of clothing. This may not be a problem, depending on the society of your mermaids (maybe they're very collectivist, and the uniformity helps them form a strong group identity), but it's worth thinking about.
Now, there is another possibility. Latex could be cast in flat, thin layers and then bound together into garments. These garments would do little for keeping warm, but they have some other advantages over form-fitting clothing:
1. They are much easier to make. All you need to do is make a flat surface - maybe a stone that's been ground flat - and pour the latex onto it, maybe with a layer of lubricant to prevent adhesion, and maybe with a tool to smooth the layer to be thin. Then you let it cure, and cut the sheets into strips or other shapes to form the elements of clothing. Bindings could be made from thin strips of this same material, if a different material doesn't suit better.
2. You could make many different styles of clothing: skirts made from strips or sheets, shirts with many layers to act as armor, fashion accessories like armbands or tassels, and so on.
3. You can modify the latex itself easily during casting. For example, mixing in plant fibers would yield a tougher, less stretchy piece of rubber. Mixing in sand or some other powdered ceramic may strengthen the material for armor, or could be used to add colors. If they have advanced enough technology, they could vulcanize the rubber to make particularly strong and rigid pieces. Some of these things could be done with a body-dip or paint-on method, but not all, and it may be easier in flat castings.
Overall, I think there's no reason to restrict yourself to one way or the other. Maybe certain things are made to be personalized and form-fitting (gloves, wet suits for keeping warm, tail guards, etc) and others (skirts, armor, decorative clothing) are made the other way. Having multiple methods adds some believability to your world: it's rare for there to only be one way that something is done.
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While I don't understand why they would need or want clothing at all, I see no reason why Merfolk couldn't make or use clothing made from rubber. With the caveat that they probably won't be able to harvest or process the raw stuff on account of the trees being on land and them living primarily in the water.
But you say they live near and participate in a human (?) social network: they could certainly trade for rubber, rubberised cloth, and any other things they'd need to make themselves feel fashionable in this society!
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If dipping into latex to make clothes underwater then the latex liquid would need to be heavier or repel from water, being in water. There are examples of this in the natural world where different types of water meet, just google for images.
For producing the latex, the plant live could be engineered over selection of species over hundreds of years to get the right results. Bleeding the latex into pools or maybe the flowers dropping with the stuff under soft currents of the sea. Also with selective breeding of these water flowers, instead of changing just the colour of the flowers. Maybe also changing the colour of the latex it produces.
Plus also think what other foods or materials these plants would produce too.
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Mars is the dusty, airless void of death and general unpleasantness it is today because it lost its magnetosphere millions of years ago. This was because Mars's dynamo in its core shut down. Because it lost its magnetosphere, the solar wind was able to strip away Mars's atmosphere, oceans, and any unfortunate aliens.
I'm working on a setting where Mars never became uninhabitable and is still nice and earth-like. I want to make sure it's scientifically accurate, though. I was thinking about giving Mars a moon (or more). My hope is that maybe the tidal forces the moon enacts on Mars could re-start the dynamo in Mars's core. I have no idea if this would work, though, and many more things might have to change that I don't know about in order to ensure Mars stays habitable. Would this work?
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# Some random protoplanetoid object hits Mars
There were probably a lot of protoplanetoid objects zooming around the Solar System. Most of them probably ended up in the Sun or in Jupiter. [One of them](https://en.wikipedia.org/wiki/Theia_(planet)) probably hit Earth.
What you need is for another one (or more) of these objects to hit Mars and coalesce into a bigger planet. Then Mars' once active plate tectonics might not have stopped, is core might still circulate, and its atmosphere would remain.
To work, you'd want the planet to be nearly as large as Earth. After all, Venus is nearly as large as Earth and doesn't appear to have either a self-generated magnetic field or active plate tectonics. So there is more to it than just size. But size doesn't hurt. Mars is only 1/10 the mass of Earth, so whatever hit it should be several times larger than Mars, at least.
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In a Rocheworld scenario where two planets are tidally locked and share an atmosphere, *but* where both the planets are so small that their gravity is very little (as low as one of the dwarf planets in our solar system, such as Ceres, for example), is it possible for creatures that can fly to go back and forth between the planets via the shared atmosphere? Handwave the existence of a breathable, dense Earth like atmosphere of course.
Could a humanoid character fly from one of the planets to the other through that area of shared atmosphere if he/she had wings (again, handwave), or one of those flying squirrel suits with something like a Buck Rogers rocket jet pack?
The way I understand it is that: They’d need enough lift to get off the ground (this place has low gravity and they’d have their wings or jet pack), and they’d have to be able to push further than the Lagrange points because if not they'd be stuck in orbit (but again, wings/jetpack, right?).
So is it possible, or am I missing something else?
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In a low gravity situation, with enough handwavium as it would take to put two planets, with atmospheres, that close together, without them colliding, there would be enough residual handwavium for flight-capable humanoids to traverse the gap. In fact, I believe that there would be a strong case for a species with leg-strength capable of jumping the gap, as the gravity at the point where the atmospheres are tangent, would be even lower due to the overlapping gravitational fields.
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There's a famous saying in science fiction: "Relativity, causality, FTL: pick two".
I choose causality and FTL. In a Newtonian universe, where there's a privileged reference frame, the speed of light isn't an absolute limit, and Einstein was wrong, what parts of physics would I need to re-work?
In particular,
1. Do I need to re-formulate Maxwell's equations?
2. Do nuclear reactions still work?
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Maxwell's equations, yes. Magnetism is closely tied to relativity. That's how the numbers work out anyway.
Two particles of equal charge will repel each other. But, if they move in parallel lines, there is an attractive magnetic force between them. Fun aside, when lightning strikes hollow objects, it [shrivels them up](http://io9.gizmodo.com/how-electricity-crushed-this-pipe-1305875574) because a very very strong current flows down the sides, causing an attractive force inwards.
The faster the two particles move in parallel, the stronger the magnetic force, while the electric force will remain constant. So, when do these two forces cancel? How fast do the particles have to travel in order to equal out the electric and magnetic forces? The answer, according to math, is *C*.
For a more clear picture, check out the two forces for electricity and magnetism:
$$F\_{electric}=\frac{1}{4\pi\epsilon\_0}\frac{q\_1q\_2}{r^2}, F\_{magnetic}=\frac{\mu\_0}{4\pi}\frac{qv}{r^2}$$
Nothing in any of those formulas is important except the constants. It turns out that
$$C=\frac{1}{\sqrt{\mu\_0\epsilon\_0}}$$
which is cool.
I don't know enough physics to explain exactly *how* they are related except for the above arguments, or how this affects things like permanent magnets. You'll no doubt have fun googling "why is the magnetic force is what it is" and turn up some cool stuff.
Anyways, from what I can tell, you might have to lose magnetism in your universe. That probably does it for nuclear reactions, too, considering it's called electromagnetic radiation.
Edit: As a disclaimer, I hope I haven't insulted your intelligence with this. You clearly knew they were related already or you wouldn't have mentioned those two specific points of interest. I hope this at least provides a decent starting point for showing how the magnetic force probably wouldn't exist in a universe without relativity, and, consequentially, light.
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In my world there is a strip of ocean which is uncross-able due to extreme currents and storms.
The solution has been to simply go underneath this particular strip (which is very narrow; only a few miles across) and then resurface on the other side.
To this end, ships which can go underwater have been built. However, the technology level of this world is similar to our medieval to early renaissance periods (with some differences in the resources available to its inhabitants).
How would a submarine operate given this constraint?
Consider:
* Method of **propulsion** (including an energy source)
* Method of **life-preservation** (Oxygen)
* Method of **navigation**
* Method of **diving** and **surfacing\***
* **Carrying capacity** (Crew and weight)
* **Materials** (For resisting water pressure)
A true submarine would be best (something which can remain underwater for long periods of time), but in theory a submersible which can go below for a short amount of time is good enough (since the strip of ocean is so narrow).
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Your first problem is the currents you mention. Currents are rarely just on top. If they are strong enough to severely affect ships you are going to have to dive reasonably deep otherwise it will just carry you away. And there is no guarantee that you can dive below them.
So first issue, I would guess that it would have to be human powered, like [this](http://www.gizmag.com/go/3715/). Apparently in 1620 a Dutchman build three different working submarines. They used oars to move the vessel, but I think it would make more sense to use 'bicycle' like apparatus to turn a screw in the back. I think there was an early civil war sub that did this.
Going to deep, I would say much more than 50ft. in rough water, would make it pretty hard to see for navigation.
The 1620 subs had a tube attached to a flotation device that allowed for air to circulate, you could even have two of them, with a 'fan' or bellows sucking air down up and forcing air up the other. the float would have to be well done so that water doesn't fill up the sub.
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So in our world in the early renaissance period there was in fact one of the last great alchemist, for he wasn't yet a scientist, did in fact build submarines that did in fact travel underwater for some time.
Cornelius Drebbel for King James I of England in 1620's built submarines and Robert Boyle, one of the first scientists very highly regarded hims and investigated the subject:
>
> Now that for which I mention this story is, that having had the curiosity and opportunity to make particular enquiries among the relations of Drebbel and especially of an ingenius Physician (Dr Kuffler) that marry’d his daughter concerning the grounds upon which he conceived it feasible to make men unaccustomed to continue so long under water without suffocation, or (as the lastly mentioned person that went in the vessel affirms) without inconvenience, I was answered that Drebbel conceived, that ‘tis not the whole body of the Air, but a certain Quintessence (as Chymists speak) or spirituous part of it, that makes it fit for respiration, which being spent, the remaining grosser body or Carcase (if I may so call it) of the Air, is unable to cherish the vital flame residing in the heart; so that (for ought I oould gather) besides the mechanical contrivance of his vessel, he had a chemycal liquor which he accounted the chief secret of his submarine navigation. For when from time to time he perceived that the finer and purer part of the Air was consumed or over-clogged by the respirations and steams of those that went in his ship, he would by unstopping a vessel full of this liquor, speedily restore to the troubled Air such a proportion of vital parts as would make it again for a good while fit for respiration, whether by dissipating or precipitating the grosser exhalations or by some other intelligible way I must not now stay to examine."
>
>
>
See further discussion here:
<http://todayinsci.com/D/Drebbel_Cornelis/Drebbel-OriginOfSubmarine.htm>
Given that one of the theories as to how he did this was via containing Oxygen that he had cooked out of Saltpeter and that the Chinese knew about Saltpeter long before that time period than it seems entirely reasonable to have there be submarines previous to that point in time back in the middle ages a little ways. The ability to have the man power and ship building to construct the vessels may be more of a limiting factor, as the Spanish Armada was sunk in 1588 by what was largely the English *fishing and merchant* fleet to the point that there were laws dictating the eating of fish.
I actually think that if you are wanting a fixed point to point navigation in a current then you may wish to consider having them use some sort of pully system; this would greatly increase the ease of navigating and put the power as being perhaps teams of oxen on either side so that the amount the vessel could hold would be increased. I am thinking that a chain system would actually be more reliable and cheaper for the day than anything involving rope as the links can be inspected and fixed by a blacksmith rather than having to have a rope walk and you are dealing with being subjected to water nearly constantly.
Drebbel's submarine held 16 people, I assume that having breathable air may have been the limiting factor. That gives something like 3000 pounds as the carrying capacity; you could probably assume that it is able to hold quite a bit more in terms of cargo carrying capacity than that if it were designed to carry cargo as cargo wouldn't necessarily need "a certain Quintessence (as Chymists speak) or spirituous part of" Air.
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Most of the world's lightest known materials are aerogels. In recent years, their mechanical strength has greatly improved, due to the creation of composites, crosslinked forms, and especially graphene aerogels.
The mechanical properties of [commercially available](http://www.buyaerogel.com/product/airloy-x103/) aerogels seem pretty impressive given their low bulk densities; I presume even more impressive figures are being produced by researchers.
Very well, what's the point of a material if you can't imagine a planet made out of it? (That's a rhetorical question, let's not VTC!)
My question: How big could an aerogel planet get?
I assume it's limited by either gravity near the core causing the material to pancake, or by temperature,or a combination of the two, but unlike aerogel, I'm dense; I have no idea how to calculate it.
Any class of aerogel, or other light material with a contiguous or mostly contiguous solid phase, with the solid and other phases distributed on a sub millimetre scale, with less than 0.6 g/cm3 is fair game. Composites are OK.
It should currently exist and have had its bulk mechanical properties measured, not inferred from theory or microanalysis only. The planet must be able to exist for at least 10000 years.
Obviously, it's extremely improbable that it will form naturally. We need not justify its formation.
Disclaimer: I am in no way linked to or benefit from the linked aerogel website.
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* <https://cseligman.com/text/planets/internalpressure.htm>
Pressure for a planet at r distance from its center
P = g2 (3 / (8 π G)) (1 - (r/R)2)
The thing holds until pressure is less than 0.6MPa for L gel (there is compressible properties at play as well, but eh, for your own excercise), so the r we are interested in equals 0
P = 3 g^2 / (8 π G)
g is gravity at surface g(R) = G M / R^2
So then:
P = 3 G M^2 / R^4 / (8 π)
ro = 3 M / (4 π R^3) (average density in L case it is 20 kg / m3)
M = ro 4 π R^3 / 3
P = (ro 4 π R^3 / 3)^2 3 G / (R^4 8 π) = ro^2 2/3 π R^2 G
R = sqrt( 3 P /(2 π ro^2 G))
So, we have for L gel
P = 0.6 MPa
ro = 20 kg / m3
G = 6.6743 × 10^-11 m3 / kg s2
Sooo, if I'm not mistaken, **which I easily may in the case**, very much may may, we have
R = ( 3 \* 600'000 / (2 3.14 400 6.7 10^-11)^0.5 ~ 3'200'000 m or 3200km
So, if mistakes didn't ruined it then surprisingly not a big number of radius to be 3200 km or diameter 6400 km. (Or in contrary - surprisingly a big number)
For a gas bubble the number would be more impressive due density decreasing closer to "surface", which may improve situation here as well, as on surface the gel does not need to be that strong.
As for it holding for a 1000 year, you would need decrease radius and make sure the material itself wont degrade that much undercosmic rays(which probably not an issue here, as it decent amount of mass to shield most strained part of the thing its core) and stuff.
Considering gravity of the thing will be minuscule, on its surface, so yeah people probably can be on that fluffy planet, and do not break it with all the typical infrastructure.
Surface gravity will be about 0.018 m/s2
But it also need to consider that the thing is on the brink of collapse, so any disturbance and it may start to self implode(use XXL one at the core area), and will it stop when it starts or not - to answer that it needs a further investigation, leave that "trivial" stuff for homework - *muhaha muhaha*
As for natural occurrence of such things, it may, if there is enough of natural occurrence of building blocks for it, that gel stuf, considering that we may say that it typical for asteroids to be a lose agglomeration of gravel sruff, those recent asteroid missions, but yes it probably not likely situation, it just that it can exist, may be.
## PS
* *From your final equation, the ratio P / ro is all important, which makes sense; those gels all have a ratio of around 20. If these gels can reach r = 3200 km, then some of the new graphene ones will probably be able to form entire planets!* – @Sean OConnor
It is size of a planet, if the calculus are not wrong, it is the size of mars already.
And what is somewhat interesting is that a shell of 100m thickness of gel is equivalent for one meter of ground soil, so reduce the planet by 1km radius and place 10m of soil on top of it and viola it looks like your typical planet.
Density is more valuable reduction than strength of material, 2 times less dense 2 times bigger radius, and 4 times stronger 2 times the radius increase. And making it less dense is easy(as first order of estimation) just cut holes in material and lay it in the way for it to have holes(idk how to describe it, but like your typical pyramide or buildings or cheese have voids/rooms) it does not require change in material technologies, and upper layers has less demands for strength than the core area. So this way if you like to have it the size of this planet, like earth, then few tricks here and there and you may have it.
And 100m your typical regolith mater displaces 10-20km of that gel shell, which compared to the whole radius is subtle change of things, but which creates a peal of soil for any goal and purpose.
That reduction of density for most of the structure, to increase size, can be done by actually create some useful voids in there from typical materials(that sure more artificial creation of the thing direction)
If we take O'Neill cylinder sizes as model to the voids(not for the living, but maybe for some technological purposes), which is 8km diameter x 32 km length, and its 8t per square meter of surface which brings us to average density of 4kg per cubic meter, which is 5 times better than airogels in considerations, it easily can replace half of the volume without compromising average sterngth, and probbaly be even stronger the stuff it replaces. Considering the aspect we can inflate such voids to a pressure it requires at its location, like 6 bar at the core and less and less pressure outwards.
* inflating is not required, but just in case if strength of that cylinder is not good enough, for some reason, there is a way to bring it up to required spec
* inflating also adds mass 6 bar of air is 9kg/m3, but still it better than gel density
* voids in pure airogel also can be inflated, but gass will permiate the thing, and it hard to tell the whole dynamics, but km's of airogel will have gas barrier properties, which also may have interesting effects like gas mixture separation, like refining columns. Despite it appearant permiability it will take quite a time for highpressure pockets to dissolve and average the whole planet thing, as it takes km's 10's km to do so, go trough a membrane of a sort.
So that initial size is very rudementary consideration of such a structure and plenty of thing still can be done to inflate the size by designing it in a better way, if we play with density by design how and in which way we place the matter, which other structures we can combine it with etc.
It actually quite interesting space structure to think about.
So carving out an asteroid, nah, old day stuff
Airogel asteroids - yez, yez!
] |
[Question]
[
My idea is to build a universe with various alien species. There are dozens of different species and every species evolved differently on a different planet. The problem arises when they want to meet each other on space stations. It is very uncomfortable to wear an environmental space suit, which regulates your own atmosphere, at a bar or club during your visit. So it was decided to set the atmospheric conditions of the space stations to 'fit' most of the species. The big question is: Does this work (on a long visit/for the staff)?
Let me give you some further constraints:
* The temperature does not matter. There are cooler and hotter places, but the differences of those temperature is fairly low, like walking into an AC-cooled building. The aliens can deal with it.
* The aliens have a human-like respiratory sytem. They all breathe in oxygen and exhale carbon dioxide, but are used to different oxygen levels in the air at different atmospherical pressures.
* The rest of the atmosphere is non-toxic (and not very reactive). It consists mainly of nitrogen and some trace gases, like our air.
* The atmospheric pressure is fixed, so there is no decompression needed between visiting different section of a space station. There might be decompression required when visiting or leaving the space station.
The problem is that oxygen is toxic if the atmospheric pressure exceeds certain limits, like shown here:[](https://i.stack.imgur.com/vQxUB.png)
The easiest solution is that every alien is required to wear a mask covering mouth and nose (like Bane in Batman, but more stylish), which regulates the amount of breathable oxygen to stay in the safe zone. If an alien species requires more oxygen at the given atmospheric pressure, ventilators in the mask accumulate more air volume per breath, extract the additional oxygen, expel the rest and thus enriche the oxygen level. For lower levels of oxygen the mask just recycles exhaled air.
The thing is how to deal with the pressure. Too low pressure causes blood to boil or cells to swell (like the accident of Joe Kittinger). Too high pressure can cause nitrogen narcosis, but might be prefered due to lower overall oxygen requirements. It would seem that mild symptoms of nitrogen narcosis start to appear above 2 bar, so a safe pressure would be around 1.5 - 2 bar, assumed that the internal structure of the space station can support that pressure against vacuum.
But what about long term effects (like weeks/months on humans) of high (around 1.5 - 2 bars) or low pressures? And what about the effects of increased oxygen levels on the human skin? It is the biggest organ and houses a very complex microbiome, which is (intentionally) not protected from higher oxygen levels.
Can aliens (or humans) live on such a space station or under such atmospheric conditions just wearing a mask instead of a full environmental space suite?
[Answer]
We can get a greater variety by adding another factor--this is a truly massive station with spin "gravity". The farther out on the station you go the higher the gravity--but also the higher the atmospheric pressure. You can have a common atmosphere even though the inner aliens and the outer aliens can't breathe each other's atmospheres.
If you want even more variety, consider oxygen concentrators. They're misnamed, they're really nitrogen concentrators (they concentrate the nitrogen out of the atmosphere, the "waste" can be 90% oxygen.) Your life support systems contain something of the sort on a large scale--extract nitrogen from the air feeding the habitat of the humans that like an 80/20 atmosphere and send it to the air feeding the habitat of the aliens that like a 90/10 mix. You have no air seals between the areas, it's just you keep separating it out. A human can walk into the 90/10 area (assuming the total pressure is Earth-like) with some difficulty.
[Answer]
**Low pressure. Supplemental O2 if you need it. And done.**
[](https://i.stack.imgur.com/9nF8R.jpg)
<https://www.boldmethod.com/learn-to-fly/aircraft-systems/oxygen-systems/?fb_comment_id=807177082667975_2232740406778295>
On earth, people operate in unpressurized environments by using supplemental oxygen. The amount depends on how low the pressure is - lower pressure / higher altitude = need more O2 to meet metabolic needs.
Of course there needs to be enough O2 to prevent your blood from boiling. But low pressure and supplemental oxygen should be a solution for most of your aliens, and it sidesteps issues with high O2 toxicity for some individuals as well as things like N2 toxicity / CO2 toxicity etc.
It is not a big deal to walk around with a device that supplies supplemental O2. Many people do. There are portable battery powered concentrators that take it from the air and supply it.
[Answer]
**Synthetic implants**
This is one option than simply an external mask that fits over the entry of the respiratory systems. This could be temporary or long-term which would no doubt offer different types and for different purposes.
There could be external implants such as this:
[](https://i.stack.imgur.com/rXZuu.jpg)
```
Copyright: CBS All Access, CBS Interactive, Star Trek Discovery, 2017
```
This alien female has visible implants to help her breath because her homeworld has a much more toxic environment. The implants provide her with componants in the immediate area of her nose and mouth with each breath. Theses are permanent and graphed into her skin in at least two places. When forcibly removed it leave her unable to breathe and would damage her skin in the process.
Or
Internal Implants that could be installed into the chest (or anywhere) that helps deal with the pressure differences and would help attribute to adding or removing oxygen.
This would be both permanent which in considering you are also know how to maintain theses devices or short term which means they'd have to be in places that could be easily removable and not damaging to external or internal systems.
If everyone knows the risks in sharing a common atmosphere and the options of implants for keeping long-term in an unfamiliar atmosphere, then no one would be too worried until the technology is removed from the factor or environmental settled are out of control.
] |
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