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A character in my setting has the ability to, at any time, turn incorporeal and back. When she becomes a ghost, it's instantaneous, and when she turns back to flesh and blood, it takes about a tenth of a second. I want to get a sense of what that power would sound like. And since the magic itself makes no sound, I'm looking to specifically work out:
1: The sound of her body being replaced by a her-shaped vacuum that is then filled by air when she ghosts
2: The sound of a her-shaped pocket of air being shoved out of the way to make room for her body in one tenth of a second.
She is a 21-year-old woman, roughly 5 foot 2 and 115-ish pounds.
**What sort of noise, if any, would the activation and de-activation of this power make?**
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1 is easy. It's similar to a sonic boom. The air collapsing into the space would create a shock wave that damages nearby fragile objects, deafen those in the room, and bust eardrums for anyone within about three feet. The magnitude of the shockwave would be proportional to the mass, and the pitch would be variable, but in the wavelength of the cross-section of the person's body. I did the rough calculations for this when I was trying to figure out how real The Flash-like movement would affect the world.
2 is harder. The force of the air getting pushed away would be like getting every part of her body slapped at once. The speed of sound is 13503.9 inches per second, and her expansion would only be in the order of 100 inches per second, so you wouldn't get a sonic boom. You'd still be rattling windows, but it wouldn't be deafening. Something on the order of a blank firing out of a gun, but much lower pitched.
Addendum: I disagree with the suggestion that it would be like a thunderclap. Anyone who has worked with a tesla coil knows the difference between an electrical snap and a whip crack. Electricity actually super-heats the air as it passes through, creating an explosion in the space instead of mere displacement.
Addendum 2: [Randall Munroe seems to agree with me.](https://what-if.xkcd.com/6/) He describes a half-glass of water collapsing like a loud bang. I think that a whole person disappearing would be louder and bangier. Munroe's kung fu is better than mine.
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Air movement causes no noise until it interacts with other objects. Sound is the vibration of air. Most of the sounds we associate with a sudden change of pressure are the result of the container, not the air movement. The "pop" from a balloon is caused by the balloon rubber moving quickly through the air as it contracts. Mixing vinegar and baking soda will cause a slight "fizzy" sound as the bubbles pop. Even though the baking soda and vinegar are creating gas which is displacing nearby air, there is no real sound from that movement. You can test this with many objects. Removing the powder from a firework and igniting it will not cause the "bang" associated with their typical sound. It is the rupturing container which causes it. The exact same energy is released, but one is much quieter than the other.
The air would fill the void based on two factors. The first is gravity, with an acceleration of 9.8 m/s/s. The second is atmospheric pressure of 14.7 pounds per square inch at sea level. Nearly 15 lbs of pressure is hardly enough to cause massive destruction, and the distance it would have to travel (only several inches at most from the outer layer of skin to the core of the body) would not allow for much acceleration. The mass of air is also not very large, as your example human body compressed into a uniform space would likely fit an area of 2 square feet. The air would rush in and collide with air from the other side, the pressure would equalize and that would be it. Air is not solid enough to make much in the way of sound as it hits itself at such a low speed.
That being said, there would be a slight sound if you were standing directly next to the person. Wave your hand quickly past your ear, or stand in front of a small fan. That slight "whoosh" is what you would likely hear as the nearby air moved to fill or vacate the area. Have a person stand several feet away and wave your hand in the air towards them. Ask them what they heard. The answer will likely be "nothing", unless it is a sound from the movement of your clothing or a creaking joint. There is very little air movement further away from the localized point. The mass volume equivalent of a human is insufficient to cause a loud noise simply by moving air a few inches. To further demonstrate, you can have a person walk forward. When they do so, they are pushing aside their surface equivalent worth of air. This air flows around them like a fluid and creates eddies behind them. Actually, if you walk through water in the shallow end of a pool you can see this visually. A slight bow wave is created in front of the person with a point of lower pressure behind them which pulls in more water to equalize the pressure. Even though they are moving their surface area equivalent worth of air mass, there is no real sound associated with the movement. If you were to wave your hand next to desk covered in papers, the rustle of the papers can provide you with your sounds, but waving your hand from across the room wouldn't do anything to the papers. It is also important to remember that the higher in elevation the person is, the less air is displaced as the air is thinner. At sea level the sound would be the loudest. High up in the mountains, the sound would be quieter.
Instead of sound, you could always use the sensation of a slight wind or breeze to indicate when your character teleports. Nearby objects would move slightly as the air moved past them. Dust, paper, trash, and other debris can easily stand in for sound. If it absolutely must have sound, then you could add an ionizing effect or something similar. Transitioning from a physical to a ghost form could create a localized energy field which is compressed by the vacuum and detonates in a snap of electrical discharge (mini lightning bolt). Ghosts are "known" to be detectable as energy so it would make sense for there to be an electrical effect. Reverting back to physical form could discharge it as more of a static type halo effect as the body would be pushing away charged air.
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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 was originally was thinking of using the Jets emitted by black holes to create antimatter, however those might not fit the setting I want, due to the fact they are don't seem to occur commonly in every black hole. So I have devised a different means.
First, electrons are shot at the black hole in a way that they have a highly elliptical orbit. The Perihelion of this orbit is where the electrons are at relativistic speeds. Then, particles of an element with a large atomic number like gold would be shot at the Perihelion of the electrons for the gold and electrons collide and produce positrons. These positrons are then collected. Is this a feasible way to produce antimatter. And if so, would it still work on small black holes (i.e smaller than stellar black holes?)
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You can actually sorta. Refer Penrose Process
<https://en.m.wikipedia.org/wiki/Penrose_process>
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A black hole may very well give you the acceleration that you need, but there's a lot more to it than just that.
*Aiming* is going to be an issue for you. Consider the total distance that your electron will travel. You're talking about orbiting a celestial object, so the electron would be traveling for hundreds of millions of kilometers. Firing two infinitesimally small particles at each other from $10^{11}$ meters away and trying to get them to collide will be a stupendously difficult task (like hitting a pop can with a BB gun, except the can is on Mars). A particle accelerator keeps the particles in a controlled environment, using magnetic containment to keep them on track. Yours will be floating free in space, subject to whatever gravitational forces they happen upon. The black hole will be the dominant force but given the sizes and distances that you're working with, something as simple as an asteroid wandering too close can nudge your particle far enough off course to miss the target by kilometers.
Also, a particle accelerator protects the interacting particles with walls that provide physical shielding, plus a vacuum in the interior. We like to say that space is a vacuum but in reality there's a lot of matter floating around out there, not to mention photons, cosmic rays, etc. A flight path of that length will give you plenty of opportunities to collide with a random particle of something else before you reach the destination.
It's a lot of space to have to control in order for the experiment to work. Particle accelerators avoid that problem by making a large number of loops through short, circular tracks (same total flight distance, but less space to control). You're sending your electrons on a long trip through a wild, uncontrolled frontier. It could conceivably work, but I'd wager that the percentage of particles that actually make it to their destination will be low enough that this won't be a feasible system.
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Given sufficient tech, and since you are roaming around the event horizon of a black hole here I assume this is available. You could just harvent the natural antimatter escaping the black holes accretion disk and the jets with a adequacy powerful magnetic field.[Antimatter Acquisition: Harvesting in Space](https://www.centauri-dreams.org/2016/08/03/antimatter-production-harvesting-in-space/)
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> But there is another way to find antimatter, for it occurs naturally in the outer Solar System and even closer to home. James Bickford (Draper Laboratory, Cambridge MA) has looked at how we might trap antimatter that occurs in the Earth’s radiation belts. In a report for NIAC back in 2006 (available here), Bickford laid out a strategy for using high temperature superconductors to form two pairs of RF coils with a radius of 100 meters, to be powered by nuclear or solar power. The idea is that the magnetic field created through the RF coils will concentrate and trap the incoming antiproton stream. Blockquote
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> Compared to harvesting antimatter on Earth, space harvesting is five orders of magnitude more cost effective, and Bickford’s report suggests we could be collecting 25 nanograms of antimatter per day near our planet. And here’s a spectacular mission concept that can grow out of this, also drawn from the Bickford report: Blockquote
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With several stationary electromagnetic "Traps" around the black hole, depending on tech and efficiency quite allot of the stuff could be harvested.
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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 envisioning a planet around a sunlike star, with gravity and temperature similar to Mars, but covered with a thin shell of water ice (with CO2 ice at the poles). The atmosphere's pressure and composition are similar to Mars, albeit with more water vapor as would be expected due to water's prevalence on the planet.
Given the low pressure/gravity and abundance of water ice, I'd expect the atmosphere to saturate with ice crystals, similar to how the martian atmosphere is full of dust. On Mars, Mie scattering due to this dust turns the sky yellow-brown. What I want to know is, **what do these ice crystals do to my planet's sky?** What color is it, and how foggy does it look (if it has moons/rings, could you see them)?
My understanding is that in the low-pressure limit, ice crystals form hollow hexagonal columns of order 10 microns in length. Since they're highly non-spherical, Mie theory isn't easily applicable (not to mention that ice has very different optical properties from dust). I'm tempted to say that the ice simply turns the sky white, like the color of ice crystals in clouds on Earth, but I have no basis to assume this is still true at much lower densities and in vastly different atmospheric conditions.
**For bonus points:** What does the planet's sky look like near the sun? I would guess there's a [halo effect](https://en.wikipedia.org/wiki/Halo_(optical_phenomenon)), but how visible is it, given the low atmospheric density? Again, I'm not positive that this effect isn't unique to Earth-like atmospheres.
[Answer]
**Mother of pearl.**
[Curiosity rover spies colorful iridescent clouds on Mars](https://www.cnn.com/2021/06/01/world/mars-colorful-clouds-curiosity-rover-scn/index.html)
[](https://i.stack.imgur.com/BfK6k.png)
"If you see a cloud with a shimmery pastel set of colors in it, that's because the cloud particles are all nearly identical in size," said Mark Lemmon, an atmospheric scientist with the Space Science Institute in Boulder, Colorado, in a statement. "That's usually happening just after the clouds have formed and have all grown at the same rate.
"I always marvel at the colors that show up: reds and greens and blues and purples," Lemmon said. "It's really cool to see something shining with lots of color on Mars.
I wish the picture was more what Dr Lemmon is describing - a rainbow colored cloud. I here assert that is how your clouds will look because that will be awesome.
Then when people need to settle down they can be plain white for a while.
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Okay, i'm working on an OC for a fanfiction/RP i'm doing with a friend. She's a centaur like creature (body shape is closest to a cat, around 5'4 in Hight (if measuring her from her front paws to head) My goal with her features was to make her all terrain IE she is able to fly, swim and run quite well.
Now she's mostly based around sea birds like albatrosses and seagulls for her wing shape but because she's a centaur i gave her 4 wings, one set on her human back and one on her lower body both connect from the shoulder blades.
The problem here is i have NO IDEA how she would fly, I've been basing her flight off of Albatross flight but with 4 wings i'm not sure if she could properly soar the way I'm thinking.
*Few points ill mention, her feathers are completely water proof, she can start flying from the water by dolphin hopping, she is best suited for flying over the ocean but she can fly over land as she's closest to a seagull in wing shape.*
[the way she's turned in the air would be closest to this.](https://i.stack.imgur.com/XJ3SN.png)
(yes she can also run like this. she's very long when like this but it makes her wings sit on the same plain. her upper wings are in-between her shoulders and her lower set are at her lower shoulders, she has a longer torso then imaged and her lower set are around 3ft total longer then her upper set. I think this answer's your question?)
[Here's her full character page if you want to look thru it. it should help a lot, just scroll down to the purple line and read from there.](https://docs.google.com/document/d/1B7FQCf83OR1CKhJA3pIoR_C2DH_0rP_tBwToW1jD4D8/edit?usp=sharing)
[Answer]
**Cicada style**
[](https://i.stack.imgur.com/Bpob4.png)
[source](https://www.etsy.com/listing/763331933/one-beautiful-and-large-ghost-cicada?gpla=1&gao=1&&utm_source=google&utm_medium=cpc&utm_campaign=shopping_us_c-home_and_living-home_decor-taxidermy_and_curiosities-insects&utm_custom1=_k_CjwKCAjwx46TBhBhEiwArA_DjEunT8ndmklI-_nns1akO8l84mq3rk7uyU5rB6obrlJ-Rk8Eq4pUnxoCI30QAvD_BwE_k_&utm_content=go_12561588948_119850658695_506949566158_pla-306107311369_c__763331933_102461766&utm_custom2=12561588948&gclid=CjwKCAjwx46TBhBhEiwArA_DjEunT8ndmklI-_nns1akO8l84mq3rk7uyU5rB6obrlJ-Rk8Eq4pUnxoCI30QAvD_BwE)
Your cat centaur thing is hopefully more flexible than the usual horse human mixes. SHe leans forward so her human torso is lined up with the cat torso and her 4 wings work like the wings of a cicada.
She is also cicada like in that she has 6 legs like a cicada. I hope she also has eyes like a cicada but maybe that is asking too much. Maybe her name could be "Cada"?
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# Realistically this would probably not work too well.
Since you're partially asking for some level of realism, here's the necessary addendum: Dragon-style bodies synergize very poorly with a large body size, especially if you're adding even more limbs to that mix. Your idea is good from an arthropod-like perspective where you have several limbs and can afford to specialize different limbs for different purposes, being a decent Jack of all trades, but flying is a big issue, because your wings need to be strong and your body must ideally be as light as possible. With that in mind, things like extra limbs make this troublesome because instead of having 2 wings with x muscle, you'll have 2 pairs which will most likely have more than x amount, but with added amount of weight from the second pair's skeletal structure. The large amount of limbs you have also means you're less streamlined, which here is twice as problematic since you want them to be both good fliers and good swimmers, and not being streamlined means your swimming speed should take a toll.
In an ideal world where we're still ignoring the square cube law' s annoying rules, but not completely, your centauroid character would probably benefit from a lack of upper body wings and a more wyvern-like lower body, with the wing limbs being the most powerful pair, sharing many traits with some azhdarchid pterosaurs. This would already mean they'd be lighter and more streamlined than if they had the dragon-style 6 limbed lower body with a 4 limbed upper body. The natural weight of the front part, lacking wings, would help balance out the lower body during flight, and they could still benefit from their wings, as the large size likely means they could achieve wings big enough for soaring. Something more or less
[](https://i.stack.imgur.com/JXkeB.jpg)
(funny enough this is pretty similar to the body shape I gave my own creature, a creature that was much more arthropod-like, but that also needed to be good at burrowing and wasn't a centaur. Taking a look at the fuzzy mole crickets might help you fleshing out your design much like it helped me in mine):
**that out of the way, something between a dragonfly and a puffin**
[](https://i.stack.imgur.com/1oOhJ.jpg)
Puffins are a very cool type of bird for an important reason: they're good swimmers with a swimming style much like that of penguins, but they're also very good and speedy fliers! Their strategy is their wings, which are adapted for this hybrid locomotion lifestyle, and their habit of beating their wings up to 400 times per minute, or 20 times every 3 seconds (and also, their beaks are used by them as shovels to dig their burrows, making them decent diggers for a bird). Given what we want is something that needs to fly and swim well, this seems like one of the best ways other than modifying the tail and lower limbs for swimming.
*At this point I'll say it again however: your character will likely have a major part of its weight located on the lower body, so the pair of wings on the upper body would probably give it a lift it doesn't need, risking imbalancing their flight.*
As for however they'd flap their wings, ignoring weight issues, they'd probably be better off doing like dragonflies, which are agile aerial predators who use their 4 wings to their max potential, actually varying in the way they flap their 2 pairs of wings depending on whether they're traveling a long distance, hunting or hovering. Taking a look at their various flapping patters can help you to make the most of your character's 4 winged anatomy for maximum agility.
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Given that pegasus flight is already kinda dubious, throwing in an extra set of wings on the other side of a very flexible joint sounds pretty awkward. Your weird 4-winged beastie probably would need to have abs you could bounce *boulders* off.
Here's the thing though... big flyers are generally soarers because flapping big wings hard and fast is really awkward and energy intensive. Just getting off the ground is a serious challenge. Consider that the forewings might just be used to generate a bit of extra *oomph* to simply clear the ground and give enough space for the main wings to operate properly. Once up a few meters they could just be tucked back (possibly with the arms tucked underneath them) to reduce the amount of aerodynamic drag they produce.
They could also be used to help perform sharp aerial turns (maybe to fight or evade, maybe to show off) or shed speed quickly (maybe to land on a small space). As such they could be rather smaller and neater than the main wings without necessarily being a useless burden or risking getting in the way.
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My perception based on reading popular-science articles is this:
1. Nothing can exceed speed of light in vacuum
2. Speed of light is the same for all observers, irrelevant of their own relative speed
But my understanding, perchance completely misguided, is that these things matter mostly when we deal with huge velocities, approaching light speed - so not something organisms on earth deal with in their slow lives. I understand also that motion of planets in our solar systems can largely/roughly be described by Newtonian mechanics. I do acknowledge that relativistic effects need to be taken into account in various pieces of actual technology used by humans but they seem to be just minor error-reducing corrections.
So, taking all this into account - can Earth-like or our-solar-system-like thing exist in a world where electromagnetic waves have no speed limit and their speed is not the same for all observers?
**UPDATE**
@AlexP said:
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> The speed of light is directly linked to the electromagnetic
> properties of the vacuum, $c=1/\sqrt{ε\_0μ\_0}$. If there is no speed
> limit, this means that the speed of light is different for different
> observers; and since the speed of light is directly linked to the
> strength of electromagnetic forces, this means that chemistry is
> different for different observers. Non-uniform chemistry makes the
> existence of life . . . difficult. (And about those error-reducing
> corrections: satellite-based navigation systems such as GPS do not
> work without applying relativistic corrections.)
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This then answers my question as a straight "no" with a nice explanation. Thank you. If you post it as the answer I'll be able to accept it.
[Answer]
The weight and balance of chemistry would change radically.
Electrons, protons and neutrons get a tiny bit of intrinsic mass from their charge (neutrons from the charges of the quarks their made of) and the Higgs field, but most of the mass comes from the magnification of that tiny amount of initial charge due to the incredible speed they are moving at. Just increasing the speed limit will re-order the orbitals where the various pushes and pulls around the atom have local minimums. No speed limit at all would, I think eliminate orbitals entirely. And chemistry as we know it. So also biology (chemistry). Might be some new combinations of balancing forces would arise, but it would be very different.
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Remember $E = mc^2$? Einstein originally wrote it another way:
$$ m = \frac{E^2}{c^2} $$
Which is the same, but makes it easier to drive the point: mass and energy are just two different measures of the very same thing. The conversion between kilograms and joules is mediated by the constant $c^2$.
If $c$ were to trend towards the infinite, you would need an infinite amount of joules to form any amount of mass at all. This means that the universe would have never evolved past the [Planck Epoch](https://en.wikipedia.org/wiki/Timeline_of_the_early_universe#Planck_epoch). In layman terms, matter would be present, but it would have no mass and no particles would exist. All you would have is quantum fluctuations in space.
[Answer]
**It depends on what else you are willing to give up.**
As you have noticed, the speed limit for the universe is not an arbitrary law enforced by a law enforcement office. It is a consequence of the equations we use to model reality (and assuming we've done a good job of those equations, a consequence of reality). To get rid of the limit, you must select equations to change, and then reflect those changes all the way through physics in a self-consistent way (or at least as consistent as gravity and quantum physics are today).
If you do a hackjob of this, simply removing equations that look unseemly, its like curing cancer with a hacksaw. It is unlikely your patient will survive. Other changes need to be made. James Mcllean mentions in his answer that the masses of the particles we use in subatomic physics are tied to relativity. Those would need to change. And you could do that. Are you willing to let angels move the particles along their pre-ordained trajectories? If so, you could do particularly brutal things to modern scientific theory, as long as you are willing to replace it with the divine force needed to make it happen. But, practically speaking, it shouldn't have to come to that. "Smaller" tweaks, if desired, can do the job. A little mass here, a little energy there. Some replacement for the connection between electricity and magnetism... you get the idea.
The Newtonian physics you want for planetary motion are not difficult. They are rather simple 2nd order equations that only need hold true at slow speeds.
There are many systems which can meet those needs. Indeed, I would argue relativity is one of the kookier ways you can have that physics. If you want more of modern scientific theory to survive, however, it could get trickier.
If you want a "big bang" which is identical in behavior to the one we theorize today, it could be difficult. In those early phases, the energy densities were extremely high, and that makes relativistic effects even more important. You would have to fudge more things. You might need more of an "epoch" where the rules shift to make things a reality (kind of like our "inflationary period," although we claim this is not a "rules change" as much as just a different regime in the same rules).
Want the Standard Model? That could be harder. The Standard Model is steeped upon the assumptions tied into assumptions of how observable values propagates. It would be difficult to remove these without substantially changing then nature of the model.
What about life itself? Could life exist? This is a thorny question, that we don't yet have an answer for. Life is frustratingly brittle. Every time we change little things like this we find reasons life as we know it cannot exist. And yet, life is inscrutably robust. To dare quote a function movie as though it were truth, "Nature finds a way." Indeed it starts to feel hubris to think that this is the only possible way something like life occurs.
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Humans colonized all the stars in the Milky Way in the first million years. In the next 200 million years they conquered all the planets in the Local Group. In the next few billion they conquered all the Virgo Supercluster.
At this point the accelerating expansion of the universe pushes further galaxies out of reach. This prevents humanity expanding further.
After billions of years, evolution has produced as many human species as there are planets conquered, some of them completely unrecognizable from the humans of today, while others had retained more or less the same appearance, like living fossils.
However, everything great will come to an end. In this fictional universe, roughly 91.8 billion years into the future, the increasing expansion of space will cause individual galaxies to be ripped apart.
175 million years before the end, ordinary galaxies are starting to have stars fly off into the void. The universe is expanding so quickly that it becomes impossible to ever get more than 200 million light-years from your starting point, without exceeding light speed.
Over the next few million years, astronomers everywhere will observe stars at the fringes of their own galaxy receding away at over a hundred km/s in every direction, and they'll also see most other galaxies starting to lose shape and get torn apart.
175 million years is a long time, and most future humans living in this time will probably go on their daily lives as the doomsday won't happen until they were long gone and their culture forgotten or evolved into something else. From their home planets, an average naked eye observer wouldn't notice anything wrong with the night sky other than their own galaxy completely disintegrating over the next 100 million years, but that's several orders of magnitude longer than an average human lifetime and therefore too slow to be noticeable. The first sign something is horribly wrong would be visible to the naked eye maybe a million years before the end: there are way fewer stars in the night sky than before, and many of them look way redder than expected. This is due to redshift, and this effect will be amplified the faster the object is receding away. 20,000 years before doomsday, most stars would've been redshifted out of the visible spectrum, leaving only a handful of neighboring stars twinkling creepy blood-red in the night sky, receding away faster than ever before.
Star after star in the night sky will redshift out of view and soon after get gobbled up by the Cosmic Event Horizon inching closer and closer. Less than a thousand years before the universe rips itself apart, the next closest star meets the same fate, leaving the night sky on any planet pitch black, except for other planets in the same solar system.
Even this won't last long. Starting a few decades before doomsday, planets will begin spiraling outwards from their respective orbits. At first, it starts slowly, barely noticeable, but as the Hubble parameter speeds up even more, the planets start gaining noticeable distance from their stars, and the climate on those planets starts cooling down, before reaching escape velocity around 9 months before the Rip, completely detaching itself from its star forever. Over the next month, what was once the host star will get dimmer and redder until it too fades from view. For the next 7 - 8 months, there will be nothing but complete darkness, except for maybe artificial lights on inhabited planets. Everything freezes over and gets snowed down, no one goes outside anymore as it's constant darkness and temperatures rapidly plunging down to below -100 degrees globally.
We've finally arrived on the day it happens. It's just like any other day for the past 8 months, except, if there are space stations in low orbit, they will start spiraling outwards today, and there's nothing one can do about it. A few hours later, they would've been yeeted into the void never to be seen again. Soon afterwards, the planet's atmosphere will start thinning, faster and faster. The planet might begin heating up slowly as the rapidly accelerating expansion are exerting forces on the planet's structure. People will also slowly start feeling lighter, then rapidly lighter, then eventually, about 30 minutes before the Big Rip, everything not directly attached to the planet will be lifted up from the ground and gradually start accelerating upwards like some dramatic Wingardium Leviosa spell straight out of a Harry Potter movie. This will be where human history ends as no one can possibly survive being yeeted into outer space in this manner. Over the next 10 minutes, the planet will start heating up to thousands of degrees and molten rock will be dripping off away from it, gradually tearing the planet apart, but as the Hubble parameter accelerates faster and faster, it'll start tearing larger and larger chunks from the planet before it eventually explodes into billions of tiny fragments.
Existence is futile at this point. Everyday objects held together by electromagnetic forces will get torn apart a few seconds before the universe ends, even subatomic particles will get torn apart too, only mere fractions of a second before the fabric of spacetime pops.
The big question is, are there any way for humanity to escape or hide from this event? Humanity has become extremely advanced and has had over 91 billion years to figure out a solution to survive this moment of doom. What could that solution be? Hiding inside black holes? Will black holes get torn apart too? What could they do afterwards if they somehow finds a solution to survive? If black holes are one of the solutions, then I would imagine an entire galaxy's population mass migrate to the central supermassive black hole of their galaxy a few million years before doomsday so they could ensure they won't get causally disconnected from it when they need it. I would imagine that for the last million years, a whole galaxy's worth of people will be concentrated within a light-year from the black hole, spawning racial conflicts between different human species of absolutely epic proportions.
On the contrary, what if there's no solution? I would imagine they need to shut everything down a generation before doomsday. Maybe they would enact policies that prohibits all people from reproducing so the last person dies a few years before the event happens.
[Answer]
They could live at the bottom level of a Birch planet within the event horizon for the final years of the universe before even the black holes are gone.
Another causal structure of space within their universe to hide within could be a cosmic string loop but this like black holes may not survive the Big Rip.
The only other option is to have a multiverse or cyclic universe. For a Multiverse simply finding a way to escape to another universe would be the solution via a wormhole or another FTL/ space-time manipulation method.
For a Cyclic universe, for any of the universe ending scenarios (Big Rip, Big Crunch or Big Freeze) the civilization will not be able to survive without extreme space-time manipulation techniques but they can leave a message in space-time for a Civilization in the next universe to decipher and learn how to revive their species.
This idea is part of Sir Roger Penrose CCC theory, the old universe will need to collapse down to a non singularity small scale for the birth of the new universe and its inflation. Messages will be imprinted in space-time by merging supermassive blackholes so that the gravitational wave background contains a complicated message which survives into the new universe.
Its not really a solution for that will please individuals that wish to live, as escaping the universe will be far more appealing but it is a way for the preservation of the species and their knowledge into the new universes although it does depend on a cyclic universe system and no singularities.
[Answer]
Black holes, as currently understood, won't help much, simply because your maximum survival time after crossing the event horizon is only a few hours per billion solar masses. Also, it's unclear why the quintessence wouldn't be in there too.
#### Seven maids with seven mops
While we haven't detected quintessence except by its gravitational effects, it could certainly have other observable properties. It's more likely that it does if it evolves over time, which it must do to cause a big rip. (In contrast, non-big-rip quintessence could just be a cosmological constant term in the GR field equation, with no other properties.)
So maybe there's some way to control it. The main problem with this is that the stuff is *everywhere*; even if you found a way to do something about it locally, would it scale? I suppose it could be unstable in some way and you could find a way to trigger a transition to a less dangerous state that would expand outward on its own (and without destroying everything in its path in the process).
#### The nuclear option
The ultimate escape from the laws of physics is vacuum decay. There's a novel by Greg Egan named Schild's Ladder in which far-future (30,000 years) descendants of humans trigger vacuum decay and eventually manage to design bodies that can survive in the interior of the new-vacuum bubble (which follows completely different physical laws). It's implied that some of them end up living in the interior permanently. They triggered the decay accidentally, but perhaps it could be done deliberately.
The bubble in that story expands at $c/2$, giving them plenty of time to study it. Realistically it would expand at $c$, but then there would be no story, so that seems like an acceptable break from reality. Also, in that story, they've long since computerized their brains; there would be no way to transfer their minds to the interior otherwise. Of course it follows that they're effectively immortal. Your human descendants apparently never developed that technology, judging by the last sentence of the question.
[Answer]
# Quantum hair.
This is a Tough One. It hinges on a hypothetical Big Rip, based on the action of a "dark energy" nobody understands. But against this immovable object you have the irresistible force of 91 billion years of research. Stand in an open area free of obstructions, because we're going to be waving hands a lot.
First, we have to ask [what happens if an object falls into a black hole](https://www.physicsforums.com/threads/how-long-does-light-shine-on-and-reflect-from-an-object-falling-into-a-black-hole.1012103/). According to the Schwarzschild t coordinate, it falls forever - however, it falls so rapidly that light from another few microseconds later cannot ever catch up to it. The object's is frozen in time in those coordinates, experiencing nothing. In its "proper time" - if it does experience time - it simply falls into a singularity in a few microseconds.
So if the Big Rip affects objects according to the t coordinate, nothing falling into a black hole can escape it. If it doesn't, the object falls in and is torn apart. You might try to argue for a middle ground - the current Hubble constant falls in at light speed with the object, so that space continually expands in front of it and it never reaches an event horizon and comes out of the hole unscathed someday. This is 90% wishful thinking and 10% handwaving, with a dash of crank speculation on my part, but it would give you someplace to "hole" up for a trillion years while waiting for the Big Rip regime to turn into something else. That something else is likely to be *much* colder and *much* slower than anything we know, though, and you still have to figure out some way to mind upload into the slow "chemistry" of neutrino nuggets or something more tenuous.
The other way to go - with comparable wishful thinking and handwaving - is to say you have a special black hole that goes *somewhere else*. All the usual options for wormholes and Alcubierre drives apply. Can you move on to a better universe, or FTL to some part of space so far over our present cosmic horizon that the physical constants are different?
Oh, wups, I forgot the title. The *most* wishful thinking uses [recent news](https://www.bbc.com/news/science-environment-60708711) that black holes might shed information from ingested objects as variations in gravitational field (the [paper](https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.128.111301) specifically addresses it in terms of gravitons). Now, slight variations in gravitational field are a rather tenuous way to try to continue your existence, but who knows? Are there any sort of interesting interactions in these gravitational radiation quanta? Is this a gravity radio for communicating with aliens? Can you use them to build a "propellantless" space drive that is more efficient than a photon drive? (I doubt it, but so long as I haven't made sense of the paper and don't understand the physics, I can be optimistic!)
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[Question]
[
I'm working on a project involving an interstellar society, and I'm looking to incorporate as much actual science and economics into the project itself since I'm a stickler for numbers and logistics. However, because I'm a stickler for numbers and logistics, I've found myself in a bit of a quandary as I've inevitably encountered the subject of space elevators as an efficient means of moving goods and people into and out of orbit. The problem I've encountered specifically is what payload levels could be moved into orbit along a space elevator, and the amount of power that would be required to sustain such an activity.
My question is this:
* How do I determine how much payload a space elevator can lift where fusion power is readily available?
* How do I determine what the most reasonable ascent speed is for the space elevator?
As I've mentioned, as much as I love science and technology, it's not a passion that I've pursued outside of creative hobbies such as worldbuilding. If you could break down the details in a somewhat comprehensible manner, I'd be ever so grateful. Thank you!
[Answer]
The maximum load of the elevator doesn't depend on your power technology, but your material technology.
* the maximum load of a lifter on your space elevator is determined by the thickness of the lower end of the cable.
* the thickness of the lower end of the cable will be kept as low as possible to reduce the weight of the entire elevator, and hence the difficulty in building the thing in the first place.
* the thicker the bottom end of the cable, the fatter the middle of the cable, and the heavier and more complex to make the whole elevator is
Really, anything from 20 tonnes or a thousands tonnes or more is fine... handwave in whatever you want to suit your story needs. Lighter loads for lower tech levels, partially constructed elevators with only a thin cable that's still being expanded, higher gravity worlds, etc.
The speed of your elevator is is limited partially by how it is attached to the cable, and partially by how it gets power. Elevators are more efficient than rockets, but there's still a lot of energy required to lift a load up to the geosynchronous point.
[Specific orbital energy](https://en.wikipedia.org/wiki/Specific_orbital_energy) is the number to care about here. The important parameters are $R$ the radius of the planet you are lifting from, $a$ the [radius of a geostationary orbit](https://en.wikipedia.org/wiki/Geosynchronous_orbit), $M$ the mass of the planet and $G$ the [gravitational constant](https://en.wikipedia.org/wiki/Gravitational_constant). $\mu$ is the [standard gravitational parameter](https://en.wikipedia.org/wiki/Standard_gravitational_parameter), $GM$. The amount of energy you have to expend to raise the lifter is defined as $$\epsilon\_a = -{\mu \over 2a} + {\mu \over R }$$
For Earth, you'll have an $\epsilon\_a$ of ~57.77MJ/kg. A hundred tonne lifter would need ~5.777TJ. If your lifter managed an average speed of 600km/h, you'd make the trip from the surface to orbit in a little under 60 hours, and need a steady power supply of about 27 megawatts sustained for the whole journey.
If fusion power is effective, compact and safe, you could fit a mini reactor to the lifter. Given the weight requirements, this seems unlikely unless you have a really substantial cable and a very large lifter of a few thousand tonnes or more. If fusion reactors are big and heavy and awkward (which is likely), you might keep them on the ground (or in orbit) and use laser or microwave beamed power to drive the lifters motors.
If you wanted a faster trip, you might be able to handwave one in given suitable power supplies, though cable friction is going to be a problem. Some kind of fancy superconducting magnetically levitated linear motor might work, but all that extra weight on the cable has to be held up by something...
Please also remember that you get *one* lifter per cable. if you want multiple lifters, you'll have difficulty fitting them past each other, even if the cable was very large indeed. Here's a reasonable artist's impression of a lifter. See how it encompasses the cable, and is quite broad in order to accomodate beamed power collection arrays:
[](https://i.stack.imgur.com/fb1OV.jpg)
(image credit [Liftport](https://en.wikipedia.org/wiki/File:SpaceElevatorInClouds.jpg))
---
I'll spare you the gory details of elevator cable width, but if anyone *really* wants me to walk you through it and doesn't fancy reading eg. [The physics of the space elevator](https://users.wpi.edu/%7Eparavind/Publications/PKASpace%20Elevators.pdf) to work it out themselves, do ask.
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[Question]
[
Acrylonitrile has been suggested as an alternative membrane-forming material for conditions like those on the surface of Titan, which might allow living cells to develop in liquid methane or ethane solvents. As a fairly small partially-polar molecule, it has a distinct advantage over the long-tailed phospholipids that our biology uses in that it remains liquid at liquid methane temperatures! And supposedly, the liquid nature of cellular membranes is very important for allowing cells to grow and divide, by simply manufacturing more membrane molecules which can slip into the membrane and self-organize.
Unfortunately, acrylonitrile in particular seems (according to [this article](https://www.science.org/doi/10.1126/sciadv.aax0272)) to not actually self-assemble into micelles or azotosomes (vesicles formed from nitrogen-containing components) in Titan-like conditions! Based on [this earlier article](https://www.science.org/doi/10.1126/sciadv.1400067), it seems that acrylonitrile, while getting the most popular press, is not the only potential option for forming low-temperature azotosomes, so all is not necessarily lost... but I have also been thinking that, for example, *plants* have rigid cell walls in addition to their fluid membranes--and somehow their cells still manage to grow and divide!
So, are fluid membranes really necessary at all? Could very low-temperature life perhaps rely on compartmentalization based on rigid, solid structures formed from larger molecules?
EDIT: Note that, while plant cell walls were an inspiration for this question, they are not actually an *answer*--plants, fungi, bacteria, and archaea all have cell walls, so clearly it's a useful structure, but they all have *different*, convergently-evolved, cell walls, and they all have very complex cell walls with a lot of cellular machinery to manage their maintenance and growth. A good answer to this question would provide a plausible explanation for how a simple rigid compartment, analogous to a cell membrane, could arise during abiogenesis--or explain why such a thing is *not* plausible after all.
[Answer]
>
> the liquid nature of cellular membranes is very important for allowing cells to grow and divide, by simply manufacturing more membrane molecules which can slip into the membrane and self-organize.
>
>
>
First, a minor clarification of definitions: cell membranes are not liquid. In a liquid, molecules freely move around each other, but in the case of cell membranes, molecules are ionically bound together in a fixed, but very flexible structure that allows it to flow sort of like a liquid at macroscopic scales. But at a molecular level, they very much behave like a solid. The term you are probably looking for is [fluid](https://en.wikipedia.org/wiki/Fluid).
Semantics aside, the actual detail of this question you need to focus on is if it allows more molecules to "slip into the membrane and self-organize". A functional membrane, regardless of how ridged it is, must allow new molecules to slip in and become more of the membrane allowing an organism to grow. Also, in order for life to evolve, the first version of a cellular membrane must be able to "self assemble" into some sort of sheet. So, your articles are not criticizing how fluid Acrylonitrile is, but how well it can self form into the repeating patterns necessary to make a contiguous membrane at all under the conditions seen on Titan. We have examples of life on earth that have very ridged cellular walls such as plant cells or gram positive bacteria, but these structures do not naturally form into thin sheets. They are created by life, not something life can be created from.
The thing is: it is very hard to create a cellular membrane without a flexible structure to build on. The limiting factor is not that it must be flexible, but that it must self organizes into sheets. However, compounds that can self-form into sheets more than 2 molecules thick can generally form into infinitely thick crystalline structures. It is weird to think about like this, but the lipid based cell membranes we use on Earth are crystals. They are very ridged for how thick they are, but at only 2 molecules thick, they are thin enough to be flexible. [Even diamond becomes flexible when organized into thin enough of sheets.](https://en.wikipedia.org/wiki/Graphene) For a crystal to be ridged, it needs to naturally form in 3 dimensions instead of 2.
Since self organizing into 2-d vs 3-d lattices seems to be mutually exclusive, it may be impossible for any *single* compound to be able to form a ridged membrane. So in order for life to exist, you need the availability of at least one compound that self organizes into 2-d sheets, then on top of that, 3-d reinforcement becomes optional using other materials. However, you can probably not risk using a self organizing molecule for your wall or else it would simply grow in all directions. If crystals were to self grow on the outside of a cell, they would likely expand to block off your proteins and kill the cell. Instead, life that uses ridged cell walls build thier walls in a controlled, non-automatic way making sure that the ridged part is the exact shape needed to not block off anything important.
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[Question]
[
What could an underwater civilization use to produce makeup and cosmetics? Considering that:
* The merfolk's tech level is the same as ours (they have fire and metallurgy thanks to magic)
* Makeup effects should be similar to those more conventionally used by humans (eyeshadow, blush, eyeliner, lipstick, concealer, etc.)
* They do not trade with the surface so the raw materials have to come exclusively from the sea or coastal regions
* Makeup needs to be done in a more compact way, so that it doesn't spread in the water
* Makeup needs to be waterproof (duh)
I apologize for any mistakes, English is not my mother language.
[Answer]
Waterproof makeup is a thing, as one can see in synchronized swimming competition or from any influencer's reel while frequenting seaside or swimming pool.
[](https://i.stack.imgur.com/iyxFC.jpg)
It can be based on substances not soluble in water, like fats which can be extracted by sea creatures. Think of the blubbers of many sea mammals, or the fat from fishes like tuna.
To this base one can then add pigments of various nature: in the past for example the pigment for making purple was extracted from a shell, which is of course a water creature. And minerals are available also underwater, if one can mine them.
[Answer]
**Makeup tattoos.**
[](https://i.stack.imgur.com/u5kSZ.jpg)
<https://upload.wikimedia.org/wikipedia/commons/6/6f/Composite_permanent_makeup.jpg>
Your merfolk use tattoos to color and accentuate their features. If you are looking to replicate cosmetic products, you can do that now with tattoos.
Maybe mermaids want to keep things fresh and not be stuck with one look? Or the artists want repeat business? Have the pigments be organic and fade with time. They must be periodically redone which is an occasion to update your look.
The woman depicted above has a pretty conservative look, I think. Persons wanting cosmetic tattoos can of course be as dramatic as they want - both in the real world and yours.
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[Question]
[
* **Context:**
For several reasons regarding the planet, such as its atmosphere density, landscape and its interference on electronic equipment, in this specific planet, people preferred to use land-ships to travel in its surface.
More specifically, the atmosphere is very dense, highly corrosive and interfere a lot with the electromagnetic stuff, the winds reach almost the speed of sound with sand-like crystal colliding and destroying everything that isn't a bunker-like structure, so you can't just take flight and send radio waves through the planet. Seismic vibrations are the most viable (if not the only) way to detect other land vessels.
For some other specific reasons, they decided to also use land-ships to attack and/or defend other civilian land-ships. And thus, the best way of detecting other land-ships is through a seismic radar (or "seidar"?) that detects the vibration these massive machines produces while moving.
Don't worry about physics and other stuff, it is just about the information displacement.
* **The problem:**
I couldn't find any kind of seismic radar that could allow for other land-ships detection, like a Sonar or a conventional Radar.
For reference, here is the Sonar screen of an unspecified ship, as you can see, the vision is in a 360 degrees around the vessel, allowing for a better localisation of stuff around it.
[](https://i.stack.imgur.com/MyE15.png)
In the other hand, the Seismic Radars that exists in real life focus only in the **depth** and **structure** of the soil, not on the **direction** and **characteristics** of these vibrations (a land-ship of a certain size and structure would produce a specific wave of vibrations). After all, it is a **cientific tool for research**, not for **war**.
[](https://i.stack.imgur.com/aNIC6.jpg)
Anyway, the thing is that, what would be the best way of **showing** the vibrations on the soil? Exactly like a Sonar screen, or something totally different that already exists?
The other type of seismic radar that I could find was the "**Insar**" that is remotely made with satellites and aircraft. But it won't do, since these seismic vibrations of other land-ships need to be detected in site by the land-ship itself.
[Answer]
**Like this, but with your choice of colors** (most submarine monitors use monochromatic green, but I have no idea why)
[](https://i.stack.imgur.com/uojRJ.jpg)
It's not likely to be circular, as those circular read-outs are generally used for radar and **active** sonar, but this sonar read-out is for **passive** sonar.
Here's the simplest way I know to describe the difference:
A) Active sonar is basically "echo-location", the animal (whales, dolphins, bats, etc.) or ship (submarine, destroyer, land-ship, etc.) generates a sound (dolphin clicks, bat chirps, Hollywood submarine PING sound effect) which goes out, bounces off of something, comes back, and the bounce back is detected by the same thing that sent it out.
B) Passive sonar is just "listening". In a best case scenario, the listener (be it animal or ship) makes no noise itself, but simply listens for anything around itself.
In your scenario, active sonar won't work. If your land-ship sent out a PING through the air, not only would it be heavily distorted or possibly outright blown away by the wind, the return echo would be far worse. If your land-ship sent out a PING through the ground (it would likely be more like a THUMP), the wave would pass under any other landships without bouncing off of them, so there would be no return signal to detect, but any landship listening would *definitely* hear their PING/THUMP, so they would only succeed in giving away their position. Submarines using active sonar will even get a return sound off of the surface of the water, and this return sound can even vary based on the waves of the surface. In other words, the 'shape' of the surface can affect the return sound. For a land-ship trying to detect another stationary and (relatively) silent landship through active sonar, the best case scenario would be that the sound wave traveling through ground would travel up through the land-ship just like it would through a boulder sitting on the ground, or just like sonar would travel up through a wave on the surface of water. It would cause a change in the return, but with no way to distinguish it from a boulder or hill in the landscape. And that's the "best case". More likely it will pass underneath it completely, registering nothing at all.
That leaves passive sonar as the only option. The display above is a passive sonar display, tracking 9 or 10 different "contacts", the distinct solid green lines (with some few fainter contacts as well, the fainter and intermittent green lines). The horizontal position of the lines indicates the direction of the contact, the vertical center of the screen is direct front. Half way between center and left edge is directly left of the submarine (land-ship). Half way between center and right edge is directly right of the submarine (land-ship). And the extreme edges are directly behind the submarine (land-ship). Top to bottom on the display indicates time. The top is where things are "now", and the farther down you go is where they were farther in the past. So you can see in the image, above, that toward the top are 3 strong green nearly vertical lines indicating 3 contacts nearly directly in front of the submarine, but farther toward the top, those same 3 lines veer to right, all the way to the edge, indicating that either the submarine turned to the left, or the contacts themselves turned to the right, and the submarine passed them on their left (the submarine's right). The best explanation I know of for how to read these types of displays (much better than my attempt here) is in
[this video](https://www.youtube.com/watch?v=AqqaYs7LjlM&list=PLjHf9jaFs8XWoGULb2HQRvhzBclS1yimW&index=6)
specifically the part starting at about the 11 minute mark, through to about the 14 minute and 15 second mark.
Now your Land-Ships will not be able to use their ground sonar (seidar) while moving, because the vibrations caused by their own ship will interfere with detection. So the complication of reading those displays will be lessened for your land-ships, when compared to a maneuvering submarine.
It's also important to note that passive sonar (seidar) would be almost useless at determining distance which is another reason why a circular read-out wouldn't be likely, as their distance function isn't relevant for passive detection. Exceptions to that would require in depth knowledge (in advance) of the subsurface ground composition in the direction of the contact, as well as familiarity with the sound signature of the target (meaning you already know, or have a good idea, of what it is you're hearing, and what it normally sounds like), and then take in to consideration how all the changes in soil and stone composition would distort that sound signature (overall, probably a nearly impossible task over any but the shortest of distances).
[Answer]
**Existing seismographs detect all kinds of things.**
<https://earthquakescanada.nrcan.gc.ca/info-gen/smeters-smetres/interpret-en.php>
>
> Other Signal Sources Seismographs are so sensitive that they can
> detect very small vibrations in the earth. For example, the CNSN
> station at Watts Point (WPB), north of Squamish, BC, detects trains as
> they pass by.
>
>
> The signal from a train is noticeably different from that of an
> earthquake because it gradually builds up strength as the trains gets
> closer, reaches its maximum as the train reaches its "closest point of
> approach", or CPA, and then gradually diminishes as the train moves
> farther away. You may also see train signals on station BLBC, near
> Blue River, BC, that is near the rail lines that connect Vancouver
> with Edmonton.
>
>
> [](https://i.stack.imgur.com/oCBQp.jpg)
>
>
> Train Signal Similarly, a large cruise ship generates a lot of
> vibration in the earth. Our station at Bella Bella (BBB), along the
> Pacific Coast, receives signals from ships on their way to and from
> Alaska. The signal has a character that is similar to a train in that
> it builds gradually to the CPA, then diminishes as it leaves the area.
> The signal is less steady though so it may have several peaks and
> valleys throughout. Here is a sample of a ship passing by BBB:
>
>
> [](https://i.stack.imgur.com/hgGfR.jpg) Ship Signal
>
>
>
Your land ships must be pretty robust to withstand that planet and they probably have serious ground traction to avoid being blown away. If a seisomgraph can detect a train it can detect your land ships. You would factor out other source of vibrations like the wind, earthquakes, dance parties, explosions, sandworms, goblin cities etc. Correlate readings with known movements of earth ships.
You will need multiple detectors spread over a region. You will compare signal strength and timing between them and triangulate the origin of the detected signal. That is how seismographs determine the epicenter of a quake.
And wolla: your earth ship detector!
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[Question]
[
For a while I've been making a realistic planet that is quite similar to Earth. I've finished the tectonic plates, ocean currents, wind patterns, and a rough height map. Next up is the biome map, which I've made following the [Köppen climate classification system](https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification), and [Artifexian's](https://www.youtube.com/watch?v=5lCbxMZJ4zA) [guidelines,](https://www.youtube.com/watch?v=fag48Nh8PXE) as well as all of his previous videos leading up to that point. I want to know if this map is accurate or if there are any criticisms I should take into account.
This is a rough height map with included tectonic plate overlay. From lightest to darkest, heights range from 0-99 meters, 100-299 meters, 300-499 meters, 500-799 meters, and 800+ meters.
[](https://i.stack.imgur.com/luqmt.png)
These are the wind patterns, which are very similar to Earth's.
[](https://i.stack.imgur.com/PcXQk.png)
This is the biomes map that I want to know is accurate or not. It includes a map of the finished ocean currents, as well.
[](https://i.stack.imgur.com/2KLQn.png)
[Answer]
You've included current effected coastal deserts which most people forget are a thing so well done. You appear however to have neglected the effects of [orographic rainfall](https://en.wikipedia.org/wiki/Orography#Orographic_precipitation) and [rain shadow](https://en.wikipedia.org/wiki/Rain_shadow) around you mountains; this will some quite serious and expansive effects, especially on the larger western continent with it's high convergent mountains. Otherwise it looks quite good with the possibly exception that the smaller landmasses may have more of a [maritime climate](https://en.wikipedia.org/wiki/Oceanic_climate) than you have given some of them credit for.
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[Question]
[
I have a scene where a little girl has a pet. It could be a dog, cat, bird, monkey, whatever works for the scene, it just has to be something that humans keep as pets. She is feeding the pet with a food that has been treated with a substance that explodes if ingested by a human, but not by the pet.
The explosion does not need to be super big and messy, just enough to blow a noticeable hole through the person's neck or stomach would be fine.
It is okay if the substance is somewhat toxic to the pet as long as it does not explode. If it is toxic, it should not cause any obvious symptoms until at least 5 minutes after the person has exploded, presuming they both ate the food at the same time. Best answer would be one that would not add any obviously unsafe taste or texture in the food, but this is not a hard requirement.
Is there an actual substance that would meet this description?
[Answer]
Your poison is **[Aluminum Phosphide](https://en.m.wikipedia.org/wiki/Aluminium_phosphide_poisoning)**.
Your pet is (Surprise!) a **camel.**
Let's get into it.
Aluminum Phosphide is a highly toxic powder. When it reacts with water or stomach acid, it produces **[Phosphine gas](https://en.m.wikipedia.org/wiki/Phosphine)**, which is highly toxic to cells. Phosphine gas is especially deadly when inhaled. Poisoning normally starts to show symptoms within a few minutes, in humans. Phosphine gas is also [pyrophoric](https://en.m.wikipedia.org/wiki/Pyrophoricity), exploding spontaneously around 38°C (100°F). Aluminum Phosphide consumption, and subsequent Phosphine production, was suspected in the [tragic death (Warning - graphic news article)](https://www.thesun.co.uk/news/9092565/india-patient-head-exploded-stomach-pumped-ignited-gas/) of a patient in India who exploded on the operating table while being treated for poison. Note, this is an extremely rare case, perhaps because humans' resting temperature is a bit below 38°C (although the stomach temperature is [close](https://www.reference.com/science/temperature-inside-human-stomach-339fbf563751fa54)). Give your victim a mild fever and worse luck, if you must.
But why a camel, of all creatures? First, their gut acidity is much milder than that of humans, [around a PH of 6.4 vs 1.5](https://www.researchgate.net/figure/Stomach-pH-data-included-in-empirical-analysis-Taxonomic-class-order-species-common_fig1_280586773). Thus, Aluminum Phosphide will turn to Phosphine gas somewhat more slowly than it would in humans (how much, I don't know). Second, their resting temperature, in the right conditions, can be notably lower than that of humans, dipping to [34°C](https://journals.physiology.org/doi/abs/10.1152/ajplegacy.1956.188.1.103). **This effectively prevents the automatic explosion of Phosphine in a suitable camel.** Third, they seem to be [obligate nasal breathers](https://en.m.wikipedia.org/wiki/Obligate_nasal_breathing), or at least breathe nasally as a primary means is respiration (I couldn't find a great source for that yet; suggestions welcome). This would prevent the camel from being as affected by the respiratory effects of the Phosphine gas, although the direct cellular damage would still take place in the gut. Finally, and importantly, camels are big, tough animals. Toxic effects are likely to be slower for them than for humans, for most poisons.
So when the villain laces some dry food with Aluminum Phosphide, being sure to keep it out of moisture, the camel will last for a few minutes, but the human, if particularly unlucky and feverish, has a chance of a very unusual and unpleasant demise.
[Answer]
**A [dragée](https://en.wikipedia.org/wiki/Drag%C3%A9e) filled with a very strong [base](https://en.wikipedia.org/wiki/Base_(chemistry))**
[](https://i.stack.imgur.com/KuYcz.png)
A dragée is a small piece of candy with an outer shell, that slowly dissolves in your mouth. A human child knows these candies and will suckle on them for a while; right until the shell is breached, the base is released, and depending on its strength it will injure the mouth tissue or even violently react with the saliva itself. Whatever it does, it won't be pretty.
The pet can be any pet. The difference is that an animal is not used to candies and will simply swallow the dragée whole. Then it breaks open in the stomach, where the base reacts with the stomach acid rendering both inert. The pet may have digestion problems for a while but it should be fine.
[Answer]
If you could get candy coated sodium (think something like M&Ms) and convince both the human and pet to swallow them whole, it would just require getting the human to eat enough (I think a "Fun Size" mini pack would do) and a candy shell designed to resist desolving inside the pet's digestive system a little longer than in a human digestive system.
If you want a longer delay in the human, add an enteric coating layer beneath the candy shell. That won't dissolve until it enters the small intestine.
Either way, pure sodium coming into contact with a wet environment, like the inside of a human, will undergo some interesting and violent chemical reactions.
[Answer]
"treated with" so there are only small amounts of the substance. there are some bacterial infections that can make you feel like you will explode, but that is not the same thing.
] |
[Question]
[
The story [Strega Nona](https://en.wikipedia.org/wiki/Strega_Nona) presents the artifact of an [infinite spaghetti pot](https://scp-wiki.wikidot.com/scp-4503). This pot, once activated, produces enough spaghetti to cover an entire town over the course of a day or two. But this all occurs while the pot is upright.
Let's assume that the mechanism of this pot is that any open space within the pot is magically filled with a new whole spaghetti noodle. The chance of a spaghetti noodle appearing in any area in any given instant is proportionate to the amount of empty space in that area of the pot. Since spaghetti is round, it's impossible to achieve 100% packing, and it will be [even harder given the new pasta will be arranged randomly](https://mathoverflow.net/a/254226/61697). Thus, even when the pot is upright, new spaghetti will be created periodically and displace existing spaghetti, causing it to overflow.
Let's also assume that the pot while upright can cover an Italian village in a single layer of spaghetti in 24 hours. Taking [Italian Village, OH](https://en.wikipedia.org/wiki/Italian_Village) as the canonical Italian Village, that's about 1 square kilometer. Let's also assume that the spaghetti is created at precisely 2mm in diameter and 25cm in length.
Now, let's say we want to generate as much spaghetti as possible. Naturally, the way to do this is to activate the pot and then invert it over a hopper with a conveyor belt or train of containers ready to receive it.
Once this system reaches equilibrium, how much volume of spaghetti does it generate per second (i.e the terminal flux of the system)? What else do I need to specify for this question to even be answerable?
**Added details:**
* The pot is 40 liters in volume and semi-spherical (as shown on the cover of the book), with an opening 50cm in diameter.
* The pot will be inverted in a carefully controlled industrial setting; temperature and humidity can be any values desired, but default to 20C and 50% humidity.
* The pot produces pure spaghetti (no olive oil).
**Partial Solution:**
A spaghetti noodle takes up 0.785 ml of volume. Thus, a full pot with perfect packing would hold around 51,000 spaghetti noodles. Assuming a packing ratio of around 60%, we can say the pot holds 30,000 noodles.
To cover Italian village takes 4 billion spaghetti noodles. Given this can be done in 24 hours, the upright pot generates about 46,000 noodles per second (which already seems impractically fast, but that's what the numbers say). This is clearly a lower bound for the inverted pot.
This is where I get stuck. An easy solution would be to say that the inverted pot, by merit of being empty at rest as opposed to 60% full at rest, generates noodles 150% faster, and thus generates 115,000 noodles per second.
But the pot isn't ever empty. If noodles appeared continuously throughout the pot, and noodles are created at rest relative to the pot it would take the average noodle a tenth of a second to fall out of the pot. I'm not sure how to convert this to an average density of noodles in the pot.
On the other hand, it feels intuitively like the upright pot should be slower at generating noodles for reasons other than the at-rest density of noodles in the pot. Noodles need to actually get pushed out of the upright pot by newly created noodles. Here's where we get into magic mechanics rather than physics. It feels like the less pressure there is on a noodle, the easier it would be to appear. To maximize spaghetti production, we should probably run this system in a vacuum. But I have no idea what factor that adds to spaghetti production (the inverse of pressure yields an infinite factor when the system is run in a vacuum, which definitely seems wrong).
[Answer]
**About 1.8 million noodles per second**
According to this reference (<http://chemicalengineeringnow.com/OrificesPrinciples.htm>) the equation your looking for is -
>
> $\dot{m} = C A \sqrt{2 \rho (P\_1 - P\_2)}$
>
>
>
Where:
* $C$ is the orifice flow coefficient
* $A$ is the area of the pot opening
* $p$ is the fluid density
* $P\_1$ is the upstream pressure on the pot opening
* $P\_2$ is the downstream pressure on the other side of the pot opening (presumably 0)
We then have:
* $(P\_1 - P\_2) = \rho g h$ (where $h$ is the height of the pot)
* Spaghetti ($\rho$) is mostly water (1000 ${{kg} \over {m^3}}$)
* The radius ($h$) of a 40L half-sphere is $\sqrt[3]{(40 \times 2) \times 3 \div 4 \div \pi}$
* $C$ is 1 (assuming the pot is designed for this)
* $g$ is approximately 9.8 m/s/s
* $A$ is $\pi (0.5 \div 2)^2 = 0.196$ m-squared
Therefore, $(P\_1 - P\_2) \approx 26,150$ Pa
and $\dot{m} = 1 \times 0.196 \sqrt{2 \times 1000 \times 26150} = $ 1,417 kg per second. Or -
* about 1.4 cubic meters per second
* about 1,417 liters per second
Or, for noodle per second. Using the provided conversion of 51,000 noodles per 40 Liter pot, I get 1,275 noodles per liter... or, for a flow rate of 1,417 liters per second, about 1.8 million noodles per second.
[Answer]
Just getting some information out of the way for explanation purposes. The pot can hold 30,000 noodles. The average noodle takes 1/10th of a second to fall from the bottom of the pot to the outer rim. And that's all of the information we need. The pot will fill in 1/10th of a second, and then continually produce the same amount. So the pot will produce 30,000 noodles every 1/10th of a second, or 300,000 noodles every second.
] |
[Question]
[
**Note:** This question is *not* about the feasibility of giant caterpillars. That is covered by the addition of magic. However, evolution and natural selection still apply to magical beings (and I love that part of my world), so giant caterpillars will evolve to fit certain roles, such as:
**Group 1: Runners**
**Chasers:**
Chasers are aggressive caterpillars that evolved longer legs, more aerodynamic profiles, and so forth in order to escape predators and chase down prey. The first type evolved from toxic, brightly colored caterpillars that found themselves being preyed upon by Urban Anklebiters (which readily ingest toxic materials and incorporate them into their bodies).
The second type evolved from armored caterpillars, which were forced to develop greater speed to avoid predators like Chompers or Plop, creatures that could eat them despite their armor. These Chasers retain their armor, as it remains useful against most predators, but are also fast enough to outrun a fleeing human and strong enough to overpower them. In comparison, Toxic Chasers are relatively fragile, albeit a real problem to clean up after they die, as their drops are all toxic.
**Stalkers:**
Stalkers are like Chasers, but slower (more or less) and stealthier. They use their camouflage, agility, and enhanced senses to find and select a creature to target, then they stalk that target until a moment of vulnerability, at which point they put on an explosive burst of speed and use a long, sharp forelimb or some such to assassinate the unfortunate creature. Basically, they're ninjas.
These caterpillars developed because many of Alendyias' denizens are fooled by camouflage but are too tough or fast for surprise attacks to be effective. Stalkers thus exhibit an intelligence and persistence beyond that of normal monsters, using hit-and-run attacks to wear down tougher prey and using their senses and agility to follow faster prey until they see an opportunity to negate the prey's speed, like a spot where they can corner the prey or a spot where they can get the drop on it.
**Group 2: Ambushers**
**Smashers:** Exemplified by Maceworms. These caterpillars are more or less sedentary, staying in one place for long periods of time. Thanks to their camouflage, unaware prey approach them and are swiftly walloped, then they are grabbed and devoured. The key here is their stationary nature and their explosive speed and power.
**Grabbers:**
Smashers grip their prey, sure, to aid in feeding, but they rely on blunt force trauma (and, perhaps, blood loss induced by bodily spikes) to subdue prey. Grabbers, however, exhibit well-developed forelimbs with barbs or "teeth" that dig into flesh and therefore deter escape, using their explosive power and muscle power to grapple and subdue prey.
**Spitters**
Spitters are giant caterpillars with the capacity to exude strands of silk, which have since evolved to fire it with greater force to aid in predation. There are two kinds, Netters and Reelers.
**Group 3: Netters** fire nets from their mouths onto prey or into their path, either immobilizing the prey or blocking their path. Netters often resemble Chasers, as nets often work only temporarily, merely slowing down the prey. Because of this, many Netters use nets to slow down their prey so they can catch up and finish them off, while others simply fire strong, sticky nets and fling stuff onto the net-covered prey to further immobilize the prey.
Reelers fire strands of silk from their mouths, which they use to "grab" prey, and then they reel the prey into their mouth. These Reelers resemble Grapplers, as they too have come to rely on their forelimbs to subdue prey (and, of course, to pull the prey in for grappling). Reelers are more successful, however, as they can grapple *and* tie prey, meaning they don't have to rely on muscle mass alone.
Altogether, my question is **How Feasible Are These Giant Caterpillar Archetypes?** As in, could they feasibly evolve? I'd also appreciate input on these archetypes' traits, which would help to improve and refine these monsters as a whole, as well as input on which ones are most likely to prey on [Leafmaw.](https://worldbuilding.stackexchange.com/questions/203909/explaining-leafmaw)
[Answer]
# only if you account for the magic and for a lack of competition. At least when it comes to the runners.
Let me start by saying something sad: while we have cases in which caterpillars did evolve into predators, they're not exactly the most suitable for the job. It is true that Hawaiian caterpillars have evolved into fearsome and successful predators, but something that must be addressed is how they're exclusive to Hawaii, a place where other ambush predators such as the praying mantis were completely absent and the niche completely vacant. We have info that they can become successful predators, but there are some things we need to address on caterpillars specifically that stack against them in some of your creatures:
* they're larvae. At the end of the day, every caterpillar has 2 simple goals: survive and eat. If they don't survive they can't eat, and if they can't eat they can't accumulate enough energy to grow and eventually metamorphose into their adult stage. Essentially, larvae have an extra problem when it comes to reaching adulthood that one might call the drawback of them not needing to compete with adults for resources: they need a lot of energy because they'll necessarily need to enter a stage of absolute lack of movement and intense energy consumption. This energy cost is something we already see in many predators, which need to make sure the amount of energy they waste hunting is not higher than the amount they get from their successful hunts. This energy cost applied to a larval stage might be (although it's not exactly stated as a fact) a strong reason for why all examples of strictly carnivorous caterpillars we have are all ambush predators which hunt by standing almost completely still until prey comes along.
* they're not fast. The natural anatomy of a caterpillar, which is itself the larva of a butterfly or moth, is not built for speed at all. Their movements are mostly reliant on them ondulating their bodies, and the fastest examples come from caterpillars which have less legs, relying on a more extreme ondulating movement to go around, and still they're not nearly as fast, being 38 mm long and reaching top speeds of 5 cms/s, 5 times faster than your average caterpillar. To put it in perspective, if they were magically scaled up to be 3 meters long and kept roughly the same max speed in relation to their body length, they'd clock in at a total of... Approximately 4 meters per second. Your average human can reach sprinting speeds of 5,5 m/s, meaning those caterpillars aren't outrunning anything. This makes sense, as the majority of caterpillars don't need to be fast, and even those that actually act as predators only evolved to be able to strike fast, being otherwise stationary and not exactly nimble.
These 2 facts alone already make the path for the runner group very bumpy. Pursuing prey requires a lot of energy and requires an animal to be both speedy and strong enough to overpower whatever it managed to outrun. Cheetahs for example have their hunting success rate at a respectable 58%. Problems: their hunting method demands absurd amounts of energy and extreme adaptations for speed, both of which are pretty bad things of you're but a larval stage that has the primary objective of storing as much energy as possible and is yet to become a fertile adult.
In addition to the problems of drastic anatomical changes just so these larvae can make the cut for pursuit predators, we also have one final problem which also applies to the ambushers: competition. It's no accident that we only observe carnivorous caterpillars in an ecosystem where mantises do not exist. Truth is that when a niche is already occupied by a creature, natural selection tends to be stacked against any other competitors that aren't already adapted for said niche. Think of the following example: a class of 5 year olds decide they want to eat cookies, but to get those cookies they need to be able to reach the table where they're placed first in an all out sprint. Now this wouldn't be a problem, if they weren't competing with another class composed entirely of adult clones of Usain bolt who have no intention of sharing any cookies. If left unattended, these kids would need to either eat something else or starve to death. Your caterpillars are at a similar situation, where their body plan and overall lifecycle as is are already against them. Couple that with the presence of another predator that's more adapted for sprinting and they're completely off the game.
For these reasons I'd say the runner group is very unlikely. They'd need to suffer heavy adaptations just to fit in the niche properly and they'd most likely still be in a situation where they'd be easily outcompeted and driven to extinction by other species much more suited for such niches, like ordinary big cats and wild dogs (fun fact: the African wild dogs have a success rate of 85%). The only way I see this working would be them existing in a place with no competition and a lot of prey items with very little ability to deter a pursuit predator, and even then to become decent enough you'd basically need them to become something like a centipede, but with a lot less legs.
AS for the ambush group...yep, pretty plausible. We already know that this hunting strategy is viable for a caterpillar and doesn't require nearly as many changes to work well (out of all species of the group that includes all carnivorous caterpillars we know of, only 2 are herbivores, which is an indicator that this lifestyle is easily viable) Carnivorous caterpillars as they come already use their spiked frontal appendages to immobilize and subdue prey and eat them alive, so essentially they already work as both grabbers and smashers up to a point, the main difference being how hard they hit their prey upon striking.
Spitters also have real world counterparts up to a point. [Another group of Hawaiian caterpillars](https://www.livescience.com/325-killer-caterpillar-eats-snails-alive.html) use their silk to stick sleeping snails to leaves and prevent them from escaping. Once they wake up and try to escape, the caterpillar waits until it gives up and hides again, at which point it crawls into the shell and eats it alive. [velvet worms](https://www.britannica.com/animal/velvet-worm) meanwhile , while not caterpillars, are known to shoot a special quick hardening slime at prey, at which point it injects it with digestive juices and drinks the thing up.
Your reelers in particular sound like a tough concept to implement with a caterpillar though. [Bolas spiders](https://spiderbytes.org/2015/03/17/bolas-spiders-masters-of-deception/) rely on silk lines with a drop of sticky "glue" at the tip to hunt the moths they eat (they also make use of pheromones to trick the moths into approaching it for a seemingly sexy time, except they don't exactly experience being in a romantic diner, just being a dinner). To make it work your reeler would need a similar method, with the main difference being that it would also need muscles capable of shooting that line and proper mouthparts for pulling the prey without accidentally biting the string off. They'd also need to worry about their prey being very much aware of what's going on and potentially getting free or even harming the predator unexpectedly. I'd say it'd be safer for your caterpillars to stick to the "restrain prey as they sleep" strategy, as it allows for less risks and doesn't require the caterpillar to need things such as venom nearly as much.
So for the classic summary: are they feasible? Not all of them. The runners seem to be pretty unlikely, as they're coming from something that can't waste a lot of energy, doesn't have a bodyplan or a metabolism very suitable for moving fast and would need drastic changes to their anatomy just to become viable, at which point they'd likely still need to be isolated from other predator groups and suffer a serious risk of extinction if they ever had to deal with exotic pursuit predators.
Your ambushers on the other hand are mostly both proven to be likely viable, as we already have fairly similar real life counterparts to these creatures, as well as examples of non-caterpillar species with similar strategies to what you want (the velvet worm being very close to what you want from the netters, its only sin being that it's not a caterpillar). The least viable I'd say would be the reeler caterpillar, since its hunting strategy is both fairly hard to pull out given the constraints of a caterpillar body plan and essentially gives whatever its trying to capture a heads up that it's in danger (your prey knowing it's been caught works better for spiders and silkworms because the prey normally can't do much to set itself free).
AS for improving the archetypes, I think I already said enough: fuse the reelers with the netters so you can get a caterpillar that shoots sticky silk strings at prey, with the main difference being making the silk stronger. That makes it so the caterpillar can safely restrain its prey from a distance approach the prey and eat it alive without needing strategies like melting it from the inside.
As for the runners: sorry, I looked at caterpillar speeds, how they move and what the fastest ones were, but I just couldn't manage to make it work in a satisfying way. Since you seemed to be already on a path to make them more similar to centipedes in general, I'd suggest making use of them instead, they're already competent speedy predators, with the scolopendra genus being naturally able to grow large (several species having individuals that can grow to over 20 cm long) and being deceptively fast and competent climbers which already give animals such as snakes, bats, rodents and birds a run for their money (also [some feel very much at home swimming in the water](https://www.nationalgeographic.com/animals/article/amphibious-centipede-discovered-laos-scolopendra-cataracta-new-species)),so their high mobility and speed could allow them to fit the role of stalkers without much problem. To give a better context for speed, the giant desert centipede can reach speeds of ~4 m/s and a maximum length of 20 cm, which means that a 3-meter long giant desert centipede magically scaled up would be able to reach bursts of over 200 km/h.
Finally, which of these caterpillars could prey on the leafmaw? Honestly, I'd dare to say all of them. You did a very good job at these to the point it turns out the concepts you want are already used by many successful predators. Combine those with how hard it is to poison a caterpillar (I found out recently that many caterpillar species are remarkably capable at resisting envenomation, due to how their nervous system is structured) and I could easily see any of your ambusher variants being capable of serving as predators to the leafmaws, the main constraint being whether they're big enough.
] |
[Question]
[
Let's say that the [Yellowstone](https://en.wikipedia.org/wiki/Yellowstone_Caldera) supervolcano has a (for it, quite small; some of Yellowstone's past eruptions are ~5 times greater in volume than this) [VEI-7](https://en.wikipedia.org/wiki/Volcanic_Explosivity_Index) eruption, ejecting five hundred cubic kilometers of [tephra](https://en.wikipedia.org/wiki/Tephra) - just to provide a reference for how powerful this is.
How far away from such an eruption could you be without being immediately injured? I know that the odds are that the ash fallout and localized societal and supply chain collapses will get you eventually, but I'm not talking about that; I'm talking about "not getting carbonized by a pyroclastic flow", or "not within the range for the shockwave to cause permanent hearing loss", or "you have time to hide under a bridge before the foot-wide chunks of pumice start hitting the area".
For reference, [Mount Pinatubo](https://en.wikipedia.org/wiki/Mount_Pinatubo)'s [eruption in 1991](https://en.wikipedia.org/wiki/1991_eruption_of_Mount_Pinatubo) pumped about ten cubic kilometers of magma above the surface. This is 50 times more powerful.
[Answer]
# From 1 km to 80 km depending on what fits your story
Let's start with this alarmist article from [The Express](https://www.express.co.uk/news/science/942747/Yellowstone-volcano-eruption-death-zone-map):
>
> Zone One would extend up to 80km from the eruption, blasting the
> ground with sweltering hot gases and up to 3m of volcanic ash at
> temperatures over 400ºC. Some 70,000 people are found in this area of
> impact and unfortunately, the direct effects of the eruption are not
> survivable.
>
>
>
So you need to be at least 80 km (50 miles) away to stand any hope of survival. At least, that's a defensible distance if you're writing a story with maximum damage. The U.S. Geological Survey, the agency responsible for monitoring volcanic activity at Yellowstone, offers [a different take](https://www.usgs.gov/faqs/what-type-eruption-will-yellowstone-have-if-it-erupts-again?qt-news_science_products=0#qt-news_science_products).
>
> The most likely explosive event to occur at Yellowstone is actually a
> hydrothermal explosion—a rock-hurling geyser eruption—or a lava flow.
> Hydrothermal explosions are very small; they occur in Yellowstone
> National Park every few years and form a crater a few meters across.
> Every few thousand years, a hydrothermal explosion will form a crater
> as much as a few hundred meters across. Though the worst-case scenario
> for a giant Yellowstone eruption is indeed bad and could have global
> implications, most past eruptions at Yellowstone were not highly
> explosive. Of the past 50 or so eruptions, almost all were simple lava
> flows. If they occurred tomorrow or next year, they would have minimal
> direct effect outside Yellowstone National Park.
>
>
>
You can scale the eruption to fit your story. Your character can be safe a click upwind or dead 75 kilometers away.
] |
[Question]
[
So I had a lot of fun reading the short story "Into Darkness" written by Greg Egan (Axiomatic 2010). I want to play with a few of the concepts of that story. In particular, the general theme of a rescue crew going in to assist in the face of some event where the precise nature of what is going on is poorly understood.
In "Into Darkness" there are randomly occurring events that take place, which I am going to refer to as Anistropic events. From the outside it looks like a giant completely black hemi-sphere suddenly appears. It projects around from a point, with a radius covering up to a couple of city blocks, though the limits on the size are poorly understood. The event appears black from the outside because light does not pass through it, or reflect off it's boundary.
Inside the event, time becomes bound to the spatial dimension projecting from the center around the radius. That is time only moves forward as you move closer to the center. To an observer inside the event, they can see rays of light from outside (the past) but none projecting back from inside. They can move along an arc, or in a line towards the center. But they cannot move away from the center. In Egan's story, surviving an event like this requires one to travel to it's epi-center. After a period of unknown time the event passes, and all matter outside the epi-centre is homogenized. So "runners" volunteer to run in and guide any unlucky folk to the epi-centre.
Naturally this impacts the communications available to the rescue team. If I recall correctly, the ones entering the event don't bother with radios. They don't get much utility, seeing as they can't send signals out, and very limited ability to only send signals to members already "deeper" in than themselves. In principle though, they can receive messages from a command site that was broadcasting from outside the event horizon. Provided they were not standing on the opposite side of the epi-centre to the broadcaster.
---
In the real world of natural disasters, communications are critical to coordinating an emergency response. Responses over large areas and multiple crews usually use a combination of short-wave radio (which can be blocked by mountains and valleys) and cell networks (which require a bunch of potentially fragile infrastructure).
---
That was just to give you an idea of the sort of thing I'd like to consider. I want to work on a setting where a team are trying to respond to some situation, but are somehow limited to one-way communication only.
In terms of real world scenarios I can think of at least two.
The first is a air-to-ground operation where the ground team have no radios, and are limited to low tech signalling, (ie rock formations, large logs, smoke). In this setting the air team could be tracking the location and intended movements of the ground team, but have no good way of signalling their own intentions (although they may hover in place / circle a location of interest).
The second is more historical. I'm thinking of the sort of voyages from the age of discovery, from the 13th century, until I guess around invention of the telegram. Any long distance mission really had a general set of orders, from a monarch, or Pope, but had no way of communicating operationally relevant details in any useful time frame. If the voyage encountered pirates, or a new land mass, it was really at the discretion of the ships captain as to how to proceed; be it fight, flight, or lay claim.
---
I guess time is the biggest obstacle to two way communications. The time it takes for a message to get to the recipient, for them to process it, and for a reply to return to the sender. In my historical case, the time limit on a message is the same as the time it takes to move a person from one location to another (pigeons only work over limited distances). In "Anisotropy" messaging with radio would be instantaneous, but for a runner trying to communicate with onsite command, they are trying to send a message to the past.
Physical obstacles are also part of the problem. The ground team, in my other example, cannot practically get to the air team to listen to any message, and then safely back down. Like wise a large object, or metal barrier, can block radio waves from getting from one site to another.
---
Returning to the Anisotropic event. I would like to think seriously about how a real world team would go about responding to an event like this. In particular what communications strategies they might develop, knowing that the field-operatives won't be able to talk-back.
Part of my response would be to setup a series of 3-4 transmit stations around the event, at some distance to get a reasonable view into it. These stations would be relaying messages from a central-command, broadcasting general instructions to anyone inside the event (ie "Walk towards the darkness", "Move slowly and calmly", "Avoid climbing or descending").
As for the runners themselves, I would imagine that part of their kit would include flouro-paint-pens and glow sticks. They could leave a trail of breadcrumbs to anyone who enters after them to show the path they had taken. This is more for the benefit of other runners, though. Anyone seeing the trail has no way of knowing if it leads to saftey or a literal dead end. However, a second runner can see the marks and may decide to diverge, to increase coverage of the rescue crew.
This feels to me about the best I can come up with.
Are there other strategies, or solutions that would help in this situation?
[Answer]
I have big troubles suspending my disbelief enough to accept a thing such as the described Anisotropy, *one in which humans may still be able to live*.
So follow me in a journey to the center of this Anisotropy
---
Terminology:
* "in the future direction" - towards the center of the Anisotropy
* "in the past direction" - opposite to the "future direction", away from the center of the Anisotropy
---
Start with the idea of a person that needs to be rescued. Most trivial case, the person is trapped in a concavity that doesn't allow her to advance towards the center. A rescuer can't see her until he is trapped in the same place.
Now, suppose the rescuer takes the absolutely blind risk of advancing in a concavity, just in case someone needs rescued there. So, he reaches the deadend too - what can he do?
Demolition charges? Yes, the rescuer may be able to throw one in the "towards center" direction and he will be safe from the shrapnel fragments (which cannot travel in the past). But doing so will kill whoever happens to be near or in "the near future" of the point the demolition charge explodes.
He can't even properly swing an axe - the back swing will "hit the past" - so that there's no "back half of the swing"; then the axe cannot be retracted after it hit something in "the future" direction, better hope one (half of a) blow is enough to clear the way.
---
Now that I think of it, anything with a functioning heart and lungs will be drawn towards the center.
The walls of the heart going "into the future" during the diastole can't contract back "into the past" during the systole. The only way for the heart to contract back is to drag the side in past towards the future direction. 2-3 heartbeats and the one living creature will need to... ummm, how to put it... follows one's heart into the future or else stop it from beating?
Pretty much the same with the lungs.
---
But, hang on, there's the Brownian motion too. Air molecules can't go into the direction of the past, right? Because if they do, *one could communicate outside through sound* and that's verboten.
Now, if my memory serves, the median speed of air molecules in their Brownian motion at normal temperature is between 300 m/s and 400 m/s. *And the molecules can't go in the "past" direction.*
Which means a wind of at least 200 m/s (averaging over half of the hemispheric solid angle oriented towards "the future"). *So something like a wind of at least 720km/h*, right?
But wait, that's not all. Recall now that the atoms/molecules of solid objects experience Brownian motion too. They themselves will be pushed "in the future" (or else sound communication will be possible by dragging a long steel cable inside and hitting it with a Morse hammer); granted, they'll progress towards the center at a lower speed than the air, but as inevitable as the "no time travel in the past".
---
Heh, one on top of the other, not only the Anisotropy is hostile to anything alive, but imagine what happens in the center of the Anisotropy with all that mass that is irresistible pulled towards a single point.
To my mind, a blackhole happens. Now, I don't know what to hope for
1. Should I wish the Anisotropy is never lifted until the blackhole mass gets past the "very energetic Hawking radiation" stage? May take a significant mass, something like the entire Everest range, *and then it's only a few centuries until the BH goes boom*
2. Should I wish the Anisotropy is never lifted? Well, that's a "Good-bye Earth", all one can hope the rate of Anisotropy substance accumulation is lower than the accretion speed of the BH at its center (and thanks God the BH is "in the future" and cannot affect the-past me directly)
3. should I wish for the Anisotropy is lifted ASAP and everything around be done and dusted under and explosion of Hawking radiation?
[Answer]
The larger limiting factor that you seem to have mentioned then ignored is that apart from pre-event records there is no data about what lies beyond the event horizon. The best course of action available to a would-be rescue force in this scenario is to signal those within the event in every way possible to move inward then deploy S&R teams to comb inward along carefully planned routes based on the pre-event layout of the area within the event horizon to cover all possible routes to salvation. They've no way to know how successful those teams are, or their ultimate fate so they're going to have to send several waves along different full coverage routes to maximise their chances of success.
***BUT***
Realistically unless those outside ***know*** there is a way to survive past the barrier, and they have no data to indicate that there is, they're likely to assume everyone within is dead and *unlikely* to "throw good money after bad". Abandonment of those within by anyone not directly emotionally invested in their safety seems likely. Those who go in will have loved ones behind the barrier and going in after them will be seen as an elaborate form of suicide.
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[Question]
[
I'm researching a way a dragon could expel a substance that freezes things it comes in contact with. I've seen two posts here on the WBSE with this theme, but both said about the animal **evolving** to have this feature and I think this might limit a little bit on how this could happen. Also, I've seen responses suggesting using liquid nitrogen, but liquid nitrogen doesn't freeze a person, if it does, it takes a long time, you can't use it as a weapon in battle.
Now the question: **could an animal expel a substance that freezes the things it touches and is effective in battle?**
* My dragon he is created, did not arise from evolution;
* It's a carnivore, I don't know if that matters, but it's there in case you need to know;
* The substance will be expelled together with the water, so if the water freezes it may incapacitate the target, even a little, or create ice blocks("hail") that have fallen on those below;
* The substance cannot be toxic, as the animal will be mounted and it will not be good if the rider ends up intoxicating nearby allies;
* The substance has to be easy to make and store, not something that would depend on super machinery to manufacture and store.
[Answer]
A reasonable solution seems to be large quantities of liquid propane dumped onto the target.
* Propane can be maintained liquid [at about 10atm](https://www.engineeringtoolbox.com/propane-d_1423.html) at 20-30C.
* Has a high vapor pressure - 8 atm at 20C, so any liquid propane will vaporize as fast as it can.
* Each kg of liquid propane will need 428kJ to evaporate (latent heat of evaporation) and will freeze about 0.2kg of water (latent heat of fusion for water: 2,260kJ/kg).
To completely freeze an 80kg human with 70% water, one will need to douse the human with about 250kg of liquid propane (and better keep it thermally isolated from the environment, so that the heat is extracted from the human. I suggest putting it into a barrel, isolated by some blankets).
At about 580 kg/m^3, it means a wee bit under half a cubic meter of liquid propane.
Do I need to mention one should avoid naked flame or sparks during the freezing process?
---
Of course, you can try other liquids with a high vapor pressure, like liquid carbon dioxide, nitrogen or helium, but the storage is gonna be a harder problem. Avoid liquid ammonia, though, its dissolution in water is exothermic.
---
Are you sure you want a tanker filled with cryo liquids as an animal?
[Answer]
You might not need a chemical to produce the ice, you could have a chamber full of [superchilled water](https://en.wikipedia.org/wiki/Supercooling). This is water cooled below it freezing point but it doesn't have a nucleation site to freeze from so it stays as a liquid, but as soon as it hits something that is can crystallise around (most thing work, it is far harder to stop it freezing) it starts to freeze.
[](https://i.stack.imgur.com/4miBI.gif)
To Stop it freezing in you dragon the chamber it is stored in would have to be **very** smooth, possible a grown protein structure. To cool the water you might be able to use a system described in [this answer](https://worldbuilding.stackexchange.com/a/215592/79015)
hopefully that helps
[Answer]
I know Bombardier beetles expel 2 chemicals to create a hot explosion. A quick google search produced [this](https://pubs.acs.org/doi/abs/10.1021/acs.macromol.8b00239)
>
> We show that liquid polyoxacyclobutane −[CH2–CH2–CH2–O]n– when mixed
> with water at room temperature precipitates solid cocrystals of the
> polymer and water. Cocrystals can also be formed by simply exposing
> the liquid polymer to saturated humidity. This appears to be the only
> known example of nonreacting liquids combining to form a solid
> cocrystal, also known as a clatherate, at room temperature. At high
> temperatures, the same polymer–water mixtures phase separate into two
> coexisting liquid phases. This combination of cocrystal formation and
> LCST-type liquid–liquid equilibrium gives rise to an unusual, possibly
> unique, type of phase diagram.
>
>
>
] |
[Question]
[
**Closed**. This question needs [details or clarity](/help/closed-questions). It is not currently accepting answers.
---
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My setting uses reactors that work on a fictional gas-like inert substance that can safely store an impossibly high amount of energy in itself (breaking the e=mc^2 equation and causing Einstein to curse at me). It is hinted at as being artificially created by an ancient Precursor species (now not present in the Galaxy) capable of reshaping the laws of physics.
The setting also has a device called a "reclamator", which can act as a heat-sink to absorb the massive amount of heat the reactor should output, using the heat to "recharge" that substance with energy (other than this device, the energy can only be extracted from the substance via a reactor), basically putting almost all the "wasted" energy back in the system to be reused.
This device is a replicable black box, an artifact of the mentioned Precursor species, meaning that it can be copied, but it can't be understood and works only when built "as is", and nobody has the necessary knowledge to comprehend why. It seems to be specifically designed to work with reactors using the fictional substance, utilizing the quirks of necessary constructive elements they must possess regardless of the overall design (So you can't install it on a thermonuclear reactor, or have it soak up ambient heat alone by itself).
The device is rather bulky, so only large reactors, fit for capital ships, can be equipped with it, and it requires a minimum amount of heat energy input to operate. It also processes the heat at a finite capacity, so having too much of it will overheat the device and break it. Thus, the largest ships of the setting still need to divert some part of the heat they generate into radiators. It also still consumes power while doing its thing.
**Considering all the above, are there any unintentional side effects and uses of having such a device in the setting that aren't covered by the limitations described?**
This device was born out of me wanting to justify the general lack of radiators on my spaceship and space station designs, despite the high amount of heat they *must* be producing. I want to know if there are any hindsight-obvious unintentional ways to use the concept (like "superefficient space engines equals any ship now has the capability to become a planet-wiping RKKV" one), so that I could acknowledge them in the worldbuilding, or patch it up with adding more use limitations to the device.
[Answer]
**You don't need it to violate the laws of physics!**
Unless lawbreaking is an important part of your story. Your substance can be [some unusual state of matter](https://en.wikipedia.org/wiki/Exotic_matter). You will use it as fusion fuel.
E=mc2. Your matter is well suited to be converted to energy. It is fuel for a fusion reactor.
The ancient tech captures heat energy kicked out by the reactor and regenerates the exotic matter. Maybe you can add energy to the exotic matter you have and that matter captures the energy as matter. You will not get back quite as much as you had because presumably you used some of the energy to power your blender and keg cooler. Entropy takes its tax.
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[Question]
[
In this recently posted [question](https://worldbuilding.stackexchange.com/questions/87459/how-could-you-make-a-cats-tail-prehensile-enough-to-use-weapons), and any other question involving strong but prehensile tails capable of holding large or heavy objects or creatures, it seems the knee-jerk response is "that's not possible, flexibility and strength simply don't go together in tails."
So, on risk of starting a tangent, WHY? I get that it's not very realistic, but come on, this is worldbuilding.stackexchange here! Making crazy stuff plausible is kind of the point! So, **why not?** Surely, considering the brilliant minds here and the incredible potential of biology (albeit with some gene editing), there is a way to get **a strong yet prehensile tail**, and not just **an awkwardly placed arm**.
So, that small tangent aside, my question is **How Can A Strong Yet Prehensile Tail Be Realistically Achieved?**
**Specifications:**
**1. As indicated in the question, I am asking on the feasibility of a specific organ, specifically a strong and flexible tail.** Additionally, all answers should be science-based and be able to back up their reasoning. I am not a biologist, so this will be science-based instead of hard-science until further notice. However, I am a logician, and while I appreciate and respect answers, I will point out anything that seems off in an answer's reasoning. **TL;DR: The best answer will have sound logic and the evidence to back it up.**
2. By *strong yet prehensile,* I mean the tail is flexible enough to serve as another appendage (ie. can move in front of the user, as well as over their head, like a stegosaurus/scorpion hybrid, *and* grab objects), **yet strong enough** to lift more than just, say, a soda can-monkeys can do that, and that does not count as strong. Come on, do we say someone is strong if they can do that? No. What if they open a chip bag? Still no. **This tail should be at least as strong as a human arm, AKA strong enough to lift and wield a weapon, and flexible enough to hold a weapon and wield it effectively, AKA acting as another appendage.**
[Answer]
# Reject monkey-tailed cats, embrace displacer beast tentacles
[](https://i.stack.imgur.com/l6g7A.jpg)
The critter above is a displacer beast, a creature from a classic ttrpg game called dungeons and dragons, and I'm not only using it due to a recent addiction to the game, but because if nature is anything to go by, the best anatomical option for something that is very flexible yet very strong is not a tail, but a tentacle.
The first part, flexibility, is very obvious: no matter how flexible a tail is, it's inevitably hindered by its own bones, which at the end of the day can only really bend in the regions between the tail vertebrae. A tentacle on the other hand is a [muscular hydrostat](https://en.m.wikipedia.org/wiki/Muscular_hydrostat#:%7E:text=A%20muscular%20hydrostat%20is%20a,as%20in%20a%20hydrostatic%20skeleton.), which in this case pretty much means a boneless limb that's mostly made of various muscular arrangements that anchor to one another for the most part. No mater how you look at it, a boneless tentacle will almost always beat any tail in terms of flexibility.
Second thing is strength: you know how tails are an association of bone, muscle and other things? Well a tentacle is mostly made of muscle and has no bones to take useful space inside (because in a tentacle, muscles are basically supported by more muscles). Want some examples? Well [an elephant can lift about 700.000 pounds (about 317 kg) using its trunk](https://www.treehugger.com/extraordinary-facts-about-elephant-trunks-4858665) and we have recorded cases of octopuses lifting 4 times their body weight with their tentacles (also, we've had cases of octopuses snapping shark spines, and the giant pacific octopus can hold over 30 pounds on a single sucker). In addition, both octopuses and African elephants are known to be extremely dexterous with their limbs. Elephants can easily hold brushes, pluck single blades of grass and hold onto potato chips without breaking them using their muscular trunk, while octopuses are known to engage in tool use and operate cameras.
So basically, if you can choose between giving them a prehensile tail or a tentacle, give them a tentacle. Give them 2 while you're at it. Depending on thickness each tentacle might be stronger than their very arms, and elephant trunks have shown us that tentacle-like appendages ending in pincer-like muscular structures are more than possible, they could choose between just grabbing a sword or wrapping the limb around it, and God help anyone trying to predict how a tentacle attacking with a sword will move next. It's true that a tentacle is functionally more fragile, as it has no bones whatsoever to stop a blade and relies almost purely on muscles for structural support, but honestly I'd say it's safer to use a more fragile tentacle with less important nerves inside than it is to use an extension of your spinal cord to fight, because that's what a tail is at the end of the day.
But well oh well, onto tails. The first difference is that in the majority of time, prehensile tails seem to be more focused on movement in a 3d environment before tool manipulation (true, octopuses also use their tentacles to move around, but the same cannot be said about elephants, giraffes and certainly not about male tapirs and their own prehensile "limb"), and in this case the square cube law and the strength of tree branches comes back to haunt us.
In spider monkeys, the creatures I'll be focusing on due to how adapted their tail are, have basically turned their tails into a fifth appendages down to having actual tail prints much like they have fingerprints. They use their tail for more stability when accessing food in more unstable parts of the canopy, as well as to swing around with Dexterity. The tail is also easily capable of sustaining their own weight. The problem? That normally equates to no less than 10 kg. Truth is, muscles work best at smaller sizes. The smaller a creature, the more weight it can usually carry in comparison to its own bodyweight, which is also most likely a reason larger heavier monkeys like chimpanzees lack such tails, as their weight means they can't go swinging around less they risk grabbing hold of a branch too weak to sustain their own weight.
Looking at felines on the other hand, the tail seems to have evolved towards a different purpose, more specifically for balance. Many feline species use their tails as a counterweights rather than as another limb. Cheetahs use them to quickly switch directions, while cats that are more adept to climbing, particularly leopards, use them to counter their momentum and stabilize their climbing motion.
So basically, not only is the cat tail not something that is normally used for grasping, but for balance, we also run into all of the problems that come from using a tail for attack like you wish them to:
1- it needs to be long. The scorpion tail is actually its segmented abdomen, and remember:
[](https://i.stack.imgur.com/qe4gF.jpg)
The yellow part is also the scorpion's abdomen
So basically, a scorpion like motion means a very long tail, which also means a very long spine,which brings us to problem 2:
2-another reminder: by weaponizing your tail you're putting the spine at risk. Spinal cord damage is a possibility, especially if someone manages to twist the tail in ways it shouldn't, and in here the flexibility becomes another problem. Most animals that actually used their tails for defense , particularly ankylosaurus, used them as more rigid, mace-like weapons with a flexible base. Apart from the base, the thing was basically a bony rod with a club at the end (stegosaurus seems to be an exception to this, with their tails seemingly having unusually flexible joints, which makes sense since it's defense strategy was stabbing the attacker rather than breaking some of their bones, although I'm no paleontologist). Notice that between the ankylosaurus, the dirpotodon and other mace tail animals, one core similarity was a notable lack of the flexibility necessary for a scorpion like motion or to the dexterous mobility of a prehensile tail.
The only creatures I'm aware of that actually use tail-like structures to attack like scorpions are, well, scorpions. Also: a funny thing about scorpions and their anatomy is the usually correlation between venom potency and pincer size that's: as a rule of thumb, the smaller and weaker the pincers the scorpion has, the more potent the venom tends to be, because scorpions with stronger pincers usually have less trouble dealing with prey with pincers alone, and therefore they don't need venom that's as powerful or fast acting. Scorpions with smaller and weaker pincers however need their prey to stop struggling as quickly as possible, and so comes in the the need to have more powerful venom. Notice however how in all of these cases the scorpion is mostly using the tails for the time needed to stab the prey and deliver the paralyzing venom.
So basically, is it possible to have a strong prehensile tail that's both flexible and strong? Well, a tail has muscles anchored on bones. The stronger you want the prehensile tail to be, the more surface area you need the bones to have, and the higher the size of the bones, the less flexible the tail will be,and the more muscle you'll need, because the mass of the bones also increases faster than the surface area. In addition to all of these problems, we have going against this idea the evolutionary history of feline tail as more balance oriented appendages (a smaller problem, evolution is known for repurposing structures all the time) and the fact that by using the tail as a limb in the way you want, you're basically making a limb that's longer than the other 4,but placed in the opposite direction to where you'd normally need it (the very reason it needs to be long) and that by being more flexible also risks damage, because breaking an arm bone doesn't risk your spinal cord, but breaking a tail vertebrae might.
The one way I'd see it working would be to have a tentacle-like muscular structure over the tail, but at this point you're adding things that normally wouldn't be there, and if you want to add in a tentacle to a tail, you might be better off removing the tail and adding 2 tentacles that just extend from the back and act like a cat tail while they're not being used (Think white spikes from the tomorrow war). It ensures the spinal cord will be safer not being swung around in combat, it can be placed closer to the creature's front, making better use of its length and still allows for that scorpion-esque movement with double the power when compared to a single tail, especially since the base of the tentacle will be closer to the target of the push than a tail base would be.
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[Question]
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One of the most important aspects getting giant arthropod creatures in earthlike conditions is the requirement of a more efficient respiratory system; the current system is not able to support massive animals because it is an open respiratory system. Oxygen is diffused directly to the tissues and absorbs it from the atmosphere passively, in the case of insects, and some actively via book lungs in the case of arachnids and crustaceans.
The biggest arthropods ever had their boom in a period in which atmospheric oxygen was approximately 10% more than today. And the nearest group to arthropods which evolved a closed respiratory system were cephalopods, indicating that the common ancestor of these groups had an open respiratory system. It is still hard to determine and think how this would be possible.
So, from the current structures that different arthropods have, how could they evolve to meet the requirements of a larger creature (take air from the atmosphere to bring oxygen to the internal tissues)?
Basically this question is searching for the series of mechanisms and process that must evolve and appear and how they would work to make it possible.
I also think that this question can be divided into another, which would be about the cardiovascular system.
[Answer]
**Most insects have spiracles but dragonfly nymphs have the closest thing to an internal lung.**
The Odonata, which includes dragonflies and damselflies are insects that go through a complete metamorphosis. Dragonfly nymphs respire through an internal gills in their rectum called the anal pyramid (this orifice also allows them to propel themselves underwater). These nymphs like many other species are known to breathe air during their final instar, when they leave the water to metamorphose into dragonfly adults. The late-final instar nymphs developed functional mesothoracic spiracles, allowing them to breathe air by positioning their head and thorax above the water’s surface. While breathing air in this position, the nymphs could also ventilate their submerged rectal gill.
This is the most likely candidate to develop into an "insect lung", and would mean giant arthropods that breathe through their butts, while the spiracles become what pores are to us.
[Answer]
**Gills.**
The closest thing to arthropods that have colonized land is not cephalopods or molluscs. They are crustaceans.
[](https://i.stack.imgur.com/iwPL9.gif)
<https://evolution.berkeley.edu/evolibrary/article/_0_0/arthropods_02>
And an awesomely land adapted crustacean is the pillbug, which is an isopod.
<https://www.pbs.org/newshour/science/pill-bugs-emerged-sea-conquer-earth>
[](https://i.stack.imgur.com/8s5qN.jpg)
A Different Way to Breathe
>
> “Like their ocean ancestors, pill bugs have gills,” said Wright. Gills
> work great in the water. They’re basically exposed mucous membranes
> that absorb oxygen out of the water and into the blood that feeds the
> rest of the body. But on land, gills are a liability.
>
>
> If the pill bug dries out, its gills won’t function properly and the
> pill bug can suffocate. That’s why you usually only find them in damp
> areas, like under a dead log. If they start to overheat and dry out,
> pill bugs will even roll into a ball to protect the remaining moisture
> on their gills.
>
>
>
Here is where being big helps. Pillbugs need to keep gills moist, so they stay where it is moist. We need to keep our lungs moist too but we truck around great reservoirs of moisture in the form of blood, with addtional water produced on demand by the oxidation of fat (CHx + O2 -> CO2 + H2O).
Your giants use gills to maximize surface area. Because they are giants with large volumes they are full of water - or better, fat or oil because it is lighter. They can keep their gills wet because of these onboard supplies. Their exoskeletons are thin or vestigial and I here assert that the reasons isopods have not displaced insects on land is because the carapace is difficult for them to evolve around and it gets too heavy and bulky as it gets larger. I was interested to read that one of the largest truly terrestrial (not littoral) isopods ([Porcellio magnificus](https://isopodapet.com/product/680/)) prefers low humidity - which it can get away with because of its size and onboard water supply.
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from comment: /Interesting, but how could this evolve in other groups of arthropods?/
You could start with insects that had already evolved gills. Behold the hellgrammite!
[](https://i.stack.imgur.com/V2LXF.jpg)
[source](https://www.youtube.com/watch?v=BfFpDUqIumQ)
The hellgrammite is the large predatory larva of the dobsonfly. They have external gills to facilitate water breathing.
[](https://i.stack.imgur.com/s2Iq1.jpg)
<http://nathistoc.bio.uci.edu/neuropt/Corydalis.htm>
Just as the ancestors of whales left the water, got adapted to the air, then brought those adaptations back to rule the waters you could have an insect adapted to air, move to the water, then back to the air with its respiratory adaptations. I like the idea of giant hellgrammite as a crocodile-like ambush predator.
The molluscs have done things like this - terrestrial snails that go back to freshwater and evolve secondary gills.
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[Question]
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In my world, one ancient culture uses a basic sort of armour made of thin, soaked leather strips which were woven together, either like thatch or like a mere weaving. Below are some pictures to illustrate how I imagine this.
[](https://i.stack.imgur.com/17Xw3.jpg)
([Stock Photo - Patterns of weave bamboo in Asia](https://www.123rf.com/photo_14366616_patterns-of-weave-bamboo-in-asia.html). Copyright : APICHAT NAWEEWONG)
[](https://i.stack.imgur.com/af1k8.jpg)
(Basket weaving close-up. This is a stock photo, one can find it right [here](https://www.pinterest.com/pin/386394843002836556/))
More examples of woven leather can be found [here](https://www.shutterstock.com/search/woven+leather+background).
I am curious as to how effective an armour made in this way can be.
Woven leather armour is meant to be of lower quality than metal armour. But I want to make sure that my armour is still viable, even if less effective than the metal counterparts.
I was thinking that it would allow for more flexibility, kinda like non-metallic chainmail, but not sure if this flexibility would come at a price of armour being *too* weak.
**I mainly want to know whether lower thickness would decrease armour effectiveness. If yes, could this gap be bypassed with the woven patterns?**
Additional information:
* The technological level is around 700~500 BC.
* They would mostly be dealing with swords and arrows. Blunt weapons were not of much use. And larger scale artillery weapons and firearms were not yet developed.
* Magic does exist but is not relevant since it is rarely used and almost never in public. Magic is an esoteric secret only known and practised in closed-off secret societies.
[Answer]
For your two questions:
>
> I mainly want to know whether lower thickness would decrease armour effectiveness. If yes, could this gap be bypassed with the woven patterns?
>
>
>
Yes and yes.
Explanation for question 1: The simplest way to think about it is with a piece of paper. One piece of paper is easily poked through with a pencil. Now take three, four, five ... ten pieces of paper, and now you have difficult getting through even a couple of them. This applies for other materials, especially soft ones like leather (at least soft relative to when they are tanned). So certainly, having a thinner armour will be less safe (though more comfortable !) for the wearer.
Explanation for question 2: Again, using paper helps with the explanation. Have you seen those thick yellow page books or a massive dictionary? If you were to put a heavy concentrated weight on either of them, the object would tear through them and you would be left with a stack of pages with a hole through them. Now, take two fresh dictionaries and interlace their pages. By this I mean: take the bottom page of dictionary 1 then put the bottom page of dictionary 2 above it, then the second to last page of dictionary 1 and so on.... You end up with a rigid stack that can even [support the weight of two cars](https://www.youtube.com/watch?v=AX_lCOjLCTo)! Another note for this is a sword or spear or arrow can get caught in the grooves of a laced or patterned armour, saving the wearer (or at most subjecting them to a bruise) while a regular leather vest would be torn through (and the wearer would have wished they had chosen a patterned armour before marching onto the battlefield).
Good questions, armour is a beautiful art piece I rarely see discussed
[Answer]
Caveat: Leather armor is a debated topic amongst both professional and amateur historians. Its effectiveness, cost to construct, how common it was, everything about leather armor is in doubt. This answer is based on my own interpretation of sources, and I have included several links at the bottom from differing perspectives and as primers to start you off on your own rabbit hole of discovery.
>
> I mainly want to know whether lower thickness would decrease armour
> effectiveness.
>
>
>
Yes. Thicker armor always makes for better protection. All armor isn't thick because of added weight, cost, and flexibility.
>
> If yes, could this gap be bypassed with the woven patterns?
>
>
>
Partially. Weaving leather will *usually* make it more resistant to piercing, for example from a sword thrust or arrow. It *might* change its protection value against blunt force damage. Leather armor is already quite resistant to slicing, and weaving will have negligible impact on this. Weaving can improve flexibility, but only to a point; more on that later.
**Tl;dr Simplified solution:** use woven leather for the chest piece ([cuirass](https://en.wikipedia.org/wiki/Cuirass)). Solid leather pieces for the lower arms ([vambraces](https://en.wikipedia.org/wiki/Vambrace)), thighs ([cuisse](https://en.wikipedia.org/wiki/Cuisses)), shins ([greaves](https://en.wikipedia.org/wiki/Greave)), and helmet. Cloth fabric for the stomach, groin, and shoulders (either [gambeson](https://en.wikipedia.org/wiki/Gambeson) or another form of cloth armor, like [linothorax](https://en.wikipedia.org/wiki/Linothorax)). Pair it all with a wooden shield. This gives you decent protection that is cheaper and lighter than metal, while also easier to repair. It is also a low-tech solution, enabling your society to use it long before innovations from the high middle ages.
**Explanations: What is leather armor?**
Leather armor is not supple, soft, or comfortable. Leather had to be hardened to offer protection. This was usually done by [boiling](https://en.wikipedia.org/wiki/Boiled_leather), but can be accomplished in [several ways](https://mazeleather.com/4-ways-to-harden-leather/). [This link](http://www.daviddfriedman.com/Medieval/Articles/Perfect_Armor_Improved.htm) is a great one to start with for understanding the boiling process, if you're interested.
Hardened leather is still more flexible than metal plate. Leather can be hardened to become plate- or wood-like, but becomes brittle. This especially hard leather can be used in some ways, such as [lamellar](https://en.wikipedia.org/wiki/Lamellar_armour), with the expectation that it will need replacement pieces after most battles. For other uses, hardened leather is not made to be that stiff, so it will have some flexibility and give, but it will be like the flexibility of a leather shoe sole, not the sides of a leather boot and definitely not like a pair of driving gloves.
Leather armor does not breathe well; wearing it is a sweaty business. It is lighter than metal, especially if the metal is iron or bronze and not a lighter alloy like steel.
**How effective is leather armor?**
This depends entirely on the type of armor. Lamellar, brigandine, simple boiled leather cuirass, each type has different properties.
As depicted in many games and fiction, leather armor looks something like [this](https://steel-mastery.com/leather-armor-costume-in-style-of-b%C3%ABor-the-old.html). This is a cuirass. Assuming proper construction (and not a costume), it will not allow the wearer to bend completely in all directions, but it will be fairly light-weight. It will offer some protection against blunt force, though repeated hits will cause stress and eventually break the armor, and padding under the leather will greatly reduce the injuries the wearer takes from such attacks. Piercing attacks made by a [sword like this](https://www.darksword-armory.com/medieval-weapon/medieval-swords/the-crusader-sword-1303/) will have a difficult time penetrating, and slashing attacks will likewise not penetrate often.
Extremely sharp swords will *easily* pierce or slice leather armor. Most battlefield weapons are not "extremely" sharp; keeping that edge is nearly impossible. As soon as you sheath the blade or actually hit anything, the edge will dull. In a pre-steel society, and especially pre-iron, nothing in battle will have such a sharp edge.
Weapons designed for armor penetration, like a [medieval rapier](https://www.ashokaarts.com/shop/unusual-afghan-rapier-sword), will pierce. Spears will be your most dangerous foe- they allow the wielder to put enough force behind a thrust to penetrate your leather armor, particularly if the spear tip is [long and thin](https://www.medievalcollectibles.com/product/hengist-spear-head/?matchtype=&keyword=&gclid=CjwKCAjwjdOIBhA_EiwAHz8xm6rt2myHqoiTluEgYxh0pcqvvQInylgwg9xhnJVyd-cefIsQJUIo1RoCQAsQAvD_BwE). Arrows and javelins will also pierce, provided the hit is not glancing and has sufficient force behind it (hunting bows, with for example a 20lb draw, won't get the job done, though a war bow with a 70lb draw will). Crossbows are unlikely at 600BC tech levels, but if used, they would penetrate.
**What about studded leather armor?**
There are arguments over whether studded leather armor ever existed historically, or what "studded armor" even is. In games, it is often used to signify leather armor "upgraded" to better protect you. This just isn't the case; metal studs are not going to stop penetration or help against blunt force, and any impact on a slashing attack will be negligible.
Studded leather armor *could* be a description of pieces of leather held together with metal studs, hence the metal holds the armor together instead of reinforcing it. This would be somewhat similar to lamellar armor, though less flexible. Most historical examples of studded leather were likely [brigandine](https://en.wikipedia.org/wiki/Brigandine); the amount of metal used means it can't be considered leather armor for our discussion here.
**But I asked about woven leather**
Weaving leather prior to the hardening process is certainly possible. This should make it easier to obtain material, as strips of leather left over from other projects could be used (to a degree). The complexity is increased, but not so much as to be impossible to make.
What does the weave actually accomplish? It allows the leather to be slightly more flexible, as the pieces can move and shift. The hardening process means it won't be a night-and-day improvement, but it will be noticeable. Unfortunately, this extra flexibility introduces friction, which will wear the leather out as it rubs against itself, reducing the lifetime of the armor. A tighter weave reduces flexibility and friction both.
More importantly, it will improve your protection from piercing strikes. This does not mean the woven leather will be immune to piercing strikes, merely a little better. That said, the weave introduces seams that can be exploited by dedicated piercing weapons, such as the previously mentioned rapier. A tighter weave will be more resistant to this.
There *might* be a beneficial increase to protection against blunt damage. Speculatively speaking, it could allow enough flex to reduce the stress such blows cause, thus helping the armor last longer under repeated strikes. It would need to be tested before hanging your hat on it, but is likely reasonable enough to pass mustard for fictional works.
**Are there other alternatives to woven leather that fulfill your needs?**
Flax gambesons could be an alternative. The cost of making these compared to leather armor is debated, but cloth armor in some form was used by nearly every society in history. Layers of cloth quilted or glued together are much better protection than one might imagine: modern kevlar armor is essentially a type of cloth armor, with layers of synthetic fibers put together.
As previously described in the tl;dr above, a combination of leather, woven leather, and cloth armor would probably be the best possible approach your ancient culture could use. The different pieces could be replaced independently, allowing for easier manufacture and field repairs, while providing the benefits of the differing types. It would probably look pretty awesome, too, [something like this](https://www.etsy.com/listing/688511229/ursine-witcher-leather-armor-inspired-by?ref=SellerDashboard) but with a woven leather chest piece.
Additional links and references: [1](https://www.reddit.com/r/badhistory/comments/8v1gai/the_real_truth_about_leather_armour/), [2](https://www.google.com/search?q=ragur%20leather%20armor&source=lmns&bih=880&biw=1794&rlz=1C1GCEA_enUS955US955&hl=en&sa=X&ved=2ahUKEwjzzqODtafyAhWPSawKHXZ5BZAQ_AUoAHoECAEQAA), [3](https://www.google.com/search?q=shadiversity%20leather%20armor&rlz=1C1GCEA_enUS955US955&ei=_fESYe-jDZG-tQarkZKgCw&oq=leather%20armor%20shadiver&gs_lcp=Cgdnd3Mtd2l6EAMYADIGCAAQFhAeOgQIABBDOggIABCABBCxAzoFCAAQkQI6BQgAEIAEOgYIABAHEB46CAgAEIAEEMkDSgQIQRgAUI6uEliUwxJgycsSaABwAngAgAGvAYgB-AuSAQM0LjmYAQCgAQHAAQE&sclient=gws-wiz), [4](https://www.reddit.com/r/badhistory/comments/8v1gai/the_real_truth_about_leather_armour/), [5](https://www.quora.com/What-does-leather-armor-protect-against), [6](https://www.libertyleathergoods.com/leather-armor/), [7](http://myarmoury.com/talk/viewtopic.php?t=1510).
[Answer]
**Yes and Yes, though there are better ways of using leather strips for armor**
The problem of thinking of woven leather as an equivalent to chain mail is leather armor *has to be hardened* to provide any meaningful level of protection against blades. Now, there isn't anything stopping your from boiling and lacquering woven leather strips in any sort of armor. The issue is that they are no longer flexible, since you need a tight weave to avoid having weak points and gaps. This lack of flexibility means they protect you well vs impacts but you won't get the loose flexibility of chain mail, which has no rigidity at all to absorb blows and is only good for blocking slashes.
The use of long woven strips also makes repairing the woven leather armor pieces more effort than it's worth. Being leather, the armor will inevitably take cut and gouge damage even if sharp attacks are deflected unlike higher quality metal armors. Leather armor is pretty good at absorbing blunt damage without losing integrity, which is more damaging vs metal but blunt damage as you have said is not prevalent. If a single strip of the weave is split, the leather woven armor will eventually unravel or loosen the weave on top of the split being a weakspot. Replacement of a strip means re-weaving the armor, which will be a right pain in the arse considering that the armor has been hardened in shape and all of the other strips are wavy and intertwined. Threading in a new supple strip of leather and then boiling the armor again isn't particularly good for the rest of the existing leather strips, and will ruin any lacquering or sealant protecting them requiring the whole armor to be re-treated.
A better solution is to use the leather strips in lamellar or scale fashion as was common in your relative time period. Lamellar is closer to what you have envisioned
[](https://i.stack.imgur.com/4pxn7.jpg) While this piece from the MET isn't in the best condition and isn't from the exact time period, it is one of the better pictures that isn't some recreation and is similar enough to most lamellar armors. Lamellar armor uses the hardened leather in individual pieces that overlap and are woven together with cords. It was very popular and provided decent protection while not being entirely rigid no matter what material was used for the lamellae rectangles be it leather, metal, or even wood and bone. The mobility of the armor is directly tied to how tight the cords weaving the lamellae rectangles together are, allowing it to be adjusted for preference. Lamellar armor is much easier to repair and maintain which matters if you are fielding an army of a few hundred or thousand troopers. Each little leather rectangle can be hardened individually and produced on a large scale without the entire armor needing to be present. It is also a lot cheaper and more efficient, as a woven armor requires long, perfect unbroken strips of leather, meaning a lot of a hide isn't suitable for making armor components. The modest size of lamellae rectangles allows more of a hide to be used due to the smaller pattern size being more forgiving in avoiding defects. While the attaching cord weave usually get damaged in battle, they are much smaller and easier to replace compared to armor grade strips of leather.
Another choice is the use scale armor. [](https://i.stack.imgur.com/5klTv.jpg) Similar to lamellar armor in using little individual pieces, scale armor differs from woven armors by instead attaching all of the pieces to another layer of cloth, leather, or mail backing. Just like lamellar, scales can be made of any available material leather or otherwise cheaply as spare parts or for new armor sets. Scale armor is pretty easy to repair as well. As long as the backing is intact, scales can be reattached or even upgraded at will. The backing depending on the material is usually patch-able in most fashions since it isn't the critical outer facing armor face and only needs to hold the scales in place. The stiffness of the backing is also the only deciding factor in the mobility of the armor, as the hardened scales are not attached to each other at all. If your backing material is cloth, the armor will nominally be as bendable as cloth.
[Answer]
First of all: Leather armor was, throughout history, never really used anywhere because of the simple fact that it sucked. Don't get baited by hollywood movies and the likes. Yes, leather was used in clothing and thus in military equipement too, but as far as armor goes, the gambison was far superior and protected you more from the incoming damage (depending on the actual time you where living in ofc.) Leather / gambison was mainly worn under chainmail and plate because you would not really want to have metal on your bare skin and also it gave a second layer of protection. Leather was used under chainmail or on places where plate armor had spots that could not be closed. And not thin, string-like leather, but heavy, sturded leather, cooked in oil and hardened with wax / resin
Ultimatively, it all did not matter: Most armies used pikemen (aka vasalls), blunt weapons vs heavy armor, and a mix of arrows/bolts and cavalry, all which could effectively "one-shot" you. This is the reason that later no armor was worn anymore. Leather does not protect well vs. piercing, which is BY FAR the most common damage type since nobody had money for swords.
For your specific question: No. Leather stripes aren't any better than hard, studded leather in which you could insert metal rings to at least try to stop slashing weapons. In eastern military you find even more evidence: The chinese warriors had armor made of paper although they knew about leather long since then. Leather is just not really good in protecting anything other than your hands and feet
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Well, the usefulness would depend mainly on the thickness. If the armor was, thin, the enemy's weapons could easily find chinks in the armor. But if the woven leather armor was thick, that would be a whole other situation.
Yes, the armor would most likely have nearly no chinks, although it could, if the weaver was incompetent, but then you would have to calculate the weight. The armor would have to be light enough for the soldier to stand and fight in, and I would suggest you not have the armor's weight go to the fullest extent. Why? Because the soldier would most likely have to fight for a long time, and if the armor was the heaviest that the soldier could carry, then that soldier could fight for a while, but would then collapse from the weight and the upcoming exhaustion, and the enemy would be free to either capture him or kill the soldier.
Even if the soldier didn't collapse, the soldier would most likely not fight its best, perhaps even sluggishly and slowly, getting worse as time wears on. The upcoming enemy soldiers, if their armor perfectly bonded with the body and contributed not that much weight, would basically kill and/or capture basically everybody.
However, some soldiers might be fit, and very strong, thus not collapsing or fighting badly, but most soldiers won't be like that. If you DO make it in your book that it is just the opposite (the majority of soldiers are very strong, instead of the majority of the soldiers are the average), I would suggest that you make at least 5% of that army the average, just to make it more interesting to your reader.
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## Context
In an half-time semi-arid, half-time watery forest region, lives the Crown chalice plant. It generally stands from the middle to the top of tall and wide trees, a mix between [Deane's gum eucalyptus](https://en.wikipedia.org/wiki/Eucalyptus_deanei) and [Corylus colurna hazelnut trees](https://en.wikipedia.org/wiki/Corylus_colurna). In other words trees ranging from around 25 to 40m in height, with some good amount of branches.
What's interesting about this plant is that in order to sustain itself, it not only takes the sunlight and water that fall on it, it also lives in symbiosis with its tree and the animals resting or drinking in it. Yes, because the Crown chalice acts as a natural anti-bacteria water container, nurishing its host and fellow companions with healthy, fungus free water. In exchange, it gets a nice complement to its diet with some minerals from the tree and bits of lost animal parts.
## Question
**My question's relatively simple in concept : How much water at most could the crown chalice plant be able to hold, before it crumbles on itself and the tree?** In other terms, what would be the highest expected Chalice scale I could go with, on average?
My goal here is to know how far we can stretch things out roughly before it becomes too much unbelievable and unrealistic. Indeed, while my world is not 100% accurate on digits, I still use some concepts to draw the tips of the universe, and I don't want to be too scientifically incoherent There are many factors to take into account, so I'll try to sort the most I could think off to win some time.
## Crown chalice characteristics
We will presume the tree is already big and old enough and reached an "adult" or old age, and that there is no issue keeping the chalice full (it is not the question). Also, we can consider the chalice global resistance, hardness, mass and density to be up to the host tree branches and leaves themselves. Since I'm not fully aware of tree physics and don't have an answer to the capacity liming factors, I let you choose whether getting inspiration from old big branches or younger and smaller ones.
Since the plant does not pop up instantly like some mine 'n crafty games, I'll talk about how it grows and its final rough shape and location. It's particularly important because I have some doubts on whichever grants the best capacity. When "attaching" to its host, there are actually two possibles situations :
* The seed sits on one branch only, which we'll call the "single-branch" setup : A single vine wraps around the branch, then another spurts and start hanging, creating an evergrowing hanging basket below the branch.
* More rarely the seed gets at the junction between two branches, which, you guessed it, will be called "dual-branch" setup : Starting from the junction, the plants grow wines around the two branches, and as it goes a "hammock" to contain the water is made in-between.
The Crown chalice gets a hang on the tree during the arid season, so it's unlikely to break apart while it is empty, since, well, it doesn't bear such an high mass of water. Also, while there is some tolerance, chalices don't grow effectively on branches which bend too much, indeed, dual-branch setups spill the water out of the holding bowl (it's hardly horizontal), and single branch configurations get dropped off the tree as the wines tend to lose a good grip around the base.
## Prior researches and hypothesis
Most probably, the single-branch setup will hold less liquid as its two-branch counterpart, as there are one less point to hold water in place and it might be more constrained horizontally.. Though... We'd also need to consider the fact that two-branch setups causes some sort of horizontal force to the tree, since the ropes are not directly above the container. Alas, I don't know how much that'll influence the results, and I don't have a tree I can tear its branches off to check (that'll make my neighbour angry, and the tree very sad).
All in all, while I think I have some basic understanding of the constraints such structure would have, I'm stucky-stuck because I lack key data regarding wood resistance and equations to make any kind of wild guess. For instance, I know that 10kg condors can stand relatively easily on tree tops, but it doesn't tell me how far this weight can be pushed up, nor if standing on top is similar or totally different to hanging at the bottom or sideways.
**So how far can I reasonably ramp up the water holding capacity of the Crown Chalice plant?**
[Answer]
**You have invented the tank bromeliad.**
[](https://i.stack.imgur.com/nWRjx.jpg)
<https://hort.extension.wisc.edu/articles/bromeliads/>
>
> Tank bromeliads have leaves that form a reservoir to hold water at
> their bases, with the largest bromeliads holding up to two gallons of
> water.
>
>
>
So two gallons is the upper limit for extant epiphytic plants that have a water tank. These tanks are super cool and things do live in them an use them. My favorite is the arboreal frog which has a single tank living tadpole, fed by its mother on eggs laid for the purpose.
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[
At the end of the desert's westward Great River (think the Nile in Egypt) there is a volcanic island called *Harek-Set*. Its black mountain is a hotspot volcano which produces obsidian and makes the soil of the island highly fertile. The island is the jewel of the the native *Sinis* people who erected their capital city there as they conquered the Riverlands. On the northern bank of the River, overlooking Harek-Set, is the rival city of *Gloriena*, formerly known as *Harek-Ra*. To summarize the long and complicated political history, *Moram*, the new supposedly immortal pharaoh of the Sinis blew out the north side of the volcano with supposedly divine powers in order to destroy her enemies in Gloriena.
**What I want to know is how plausible it is to have a volcanic eruption that does each of the following:**
1. This all happens in a mountain island that fits in between the branches of a river that forks because of the island before emptying into the ocean
2. The initial eruption instantly buries Gloriena with stone and ash
3. Does not necessarily destroy the city-state of Harek-Set, either in the initial blast or the aftermath - they were told to wear earplugs and stuff
4. The smoke released taints the sky, changing the climate to the
point of severely impacting, but not necessarily exterminating all
peoples - collapse of most but not all civilizations preferred
5. The Dark Age would last on a scale of centuries, bringing humanity (et al) to its lowest point a few centuries or even a thousand years later, then petering out after that as things slowly get better.
**The last two points are the most important.** A quick web search names Tambora as the worst eruption in history, having caused "The Year without a Summer" but that's not extreme enough. **I don't want a year without a summer, I want centuries. But still with people and some megafauna around to see. I'm okay with lots of things going extinct, but not all human(oid)s.**
Here's some things I think might happen as a result, but I'm not sure:
* The ocean to the west and its people would be affected the worst, as the desert winds go out to sea, taking the initial dust cloud as well as the toxic fumes that slowly seep afterwards from the Broken Mountain there first
* The northern branch of the river's mouth would become a bog, as it would be dammed by the stone (and now-constant lava flow?)
* Agrarian cultures everywhere would fail due to weakened sunlight (and possibly acidic rain?) so people and animals would generally try to migrate to warmer regions with lots of groundwater
* Rain may tend to be acidic, severely impacting the Ocean People in the west and the Forest People in the east, but possibly not affecting the Great River since much of its water comes through the mountains which may sufficiently filter out the contaminants - I don't know if a volcano that produces good soil would make for poison rain if too much of it got in the air
* Meltwater would dry up as the years get colder, threatening the near-polar and snowcap mountain cultures
* Forests would turn to rancid swamps as the dying trees rot, creating more food for fungus and grubs which then overproduce themselves, maybe completely restarting the ecology
After doing some cursory research on volcanic eruptions, I'm realizing that a big blast that destroys a city across the river without destroying the city right behind it is kinda lowballing if I want the aftereffects to be obvious for the entire world for centuries to come. And if I make the blast too big then it would destroy Harek-Set. And if it's just a slow burn then then it would only be a threat to Gloriena, not its swift and unstoppable destruction.
I'm thinking now this situation would make sense if Moram set off the volcano, but couldn't stop it, so it just keeps on billowing smoke for years after the Black Day, like Laki which erupted for 8 months, making things worse and worse as the years continue to get colder.
For further context, the world is roughly Earthlike with the main focus, the Riverlands, being approximately where the Mediterranean is on Earth. The Ocean to the west may be the only ocean, and is presumed to be landlocked, although it or another ocean must exist in the east to create the moist landbreeze that waters the origins of the Great River as well as the forest beyond the mountains. I've sketched a couple maps on paper but can't figure out how to get the image onto my computer; will most likely update later
[Answer]
If you want something that messes up with the climate for centuries, you are looking for something akin to the [Deccan traps](https://en.wikipedia.org/wiki/Deccan_Traps)
>
> The Deccan Traps is a large igneous province of west-central India (17–24°N, 73–74°E). They are one of the largest volcanic features on Earth. They consist of multiple layers of solidified flood basalt that together are more than 2,000 m (6,600 ft) thick, cover an area of c. 500,000 $km^2$ (200,000 sq mi), and have a volume of c. 1,000,000 $km^3$ (200,000 cu mi).
>
>
> The Deccan Traps began forming 66.25 million years ago, at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats some 66 million years ago. This series of eruptions may have lasted fewer than 30,000 years.
>
>
> The original area covered by the lava flows is estimated to have been as large as 1.5 million $km^2$ (0.58 million sq mi), approximately half the size of modern India.
>
>
> The release of volcanic gases, particularly sulfur dioxide, during the formation of the traps may have contributed to climate change. Data points to an average drop in temperature of about 2 °C (3.6 °F) in this period.
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>
About the formation of such feature
>
> It is postulated that the Deccan Traps eruption was associated with a deep mantle plume. The area of long-term eruption (the hotspot), known as the Réunion hotspot, is suspected of both causing the Deccan Traps eruption and opening the rift that once separated the Seychelles plateau from India. Seafloor spreading at the boundary between the Indian and African Plates subsequently pushed India north over the plume, which now lies under Réunion island in the Indian Ocean, southwest of India. The mantle plume model has, however, been challenged.
>
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[Answer]
You might want to look into 536 ad. A volcanic eruption caused crop failures, plagues, and societal collapses from Mexico to Mongolia.
Some people attribute the onset of the dark age to this.
<https://www.history.com/news/536-volcanic-eruption-fog-eclipse-worst-year>
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**Closed**. This question needs [details or clarity](/help/closed-questions). It is not currently accepting answers.
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I want to write a Story about a medieval village
This Village is plagued by a lot of misfortunes and as people are they blame it on witches but i am having a hard Time finding good occurences.
The Thing is:
They need to be explainable by a medieval science guy
and the explanations does not have to be correct but belivable by "sience" and some wishfull thinking that magic does not exist.
[Answer]
Just about anything could be blamed on witches, including a stillborn calf, a bad year for crops, an accidental fire, or a plague. During the witch hunts, Witches were blamed for just about anything that went wrong. Most of these things are just bad things that happen sometimes, but people really like having someone to blame for their misfortune. and the trouble with this is that even if you can find a definite cause, the folks might still blame the witch.
Say a cow knocks a lantern over and burns down half of Chicago (which actually happened once, by the way.) The people might blame a witch for the fire. If someone discovers what really happened, the people might still blame the witch for jinxing the lantern to fall over.
In most cases, though, there won't be a clear, underlying cause; the event will have been caused by multiple things far outside of anyone's control. A bad harvest might be caused by a drought, which might have been caused by unusually weak winds that year. The townsfolk likely won't be super happy with that answer; they want a specific person to blame.
[Answer]
You might be better off concentrating -- as those who opposed witch-hunting often did -- on the difficulties of proving that a person is a witch responsible for a given harm.
For instance, take a storm that ruined crops or sank a ship. We would be hard put nowadays to **prove** that a storm was not caused by witchcraft. But rigorous judges would demand answers to question such as these:
* How do you know that storm was not a natural occurrence?
* If you have evidence that it was not natural, how do you know it was caused by witchcraft rather than divine intervention, or a devil's work?
* If you have evidence that it was witchcraft, do you have evidence that this person was the witch responsible?
Those who claimed that a witch could not do things would do so on theological grounds, not scientific. For instance, the Church taught that it was impossible for a witch to affect the weather.
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Say we have an artifact (in a medieval-technology world). The artifact is shaped as a solid of revolution: perhaps a donut. It weighs a few kg and is <1 meter across. It is absolutely smooth and frictionless. It is spinning about its axis at a substantial fraction of light speed, say 0.5c, and is made of some material sufficient to withstand the forces involved.
The object would have the following Newtonian properties:
* You can pick it up in your hand and move it around like anything that weighs a few kg. It's perfectly smooth so you won't even feel it spinning. It doesn't generate frictional heat.
* You cannot turn it no matter how hard you push. Its axis of revolution is immovable due to the artifact's incredibly high rotational energy.
* You can set it down on the ground and it won't roll.
* As the planet rotates under the object, the object's axis of revolution remains absolutely fixed relative to an inertial frame. This means the axis of revolution (and the object itself) will seem to slowly rotate relative to the planet over a 24 hour period, similar in concept to Foucault's pendulum.
Now my question is about the relativistic properties. Specifically, would the object carry noticeable gravity from its dragging of space? How fast would it have to be spinning to do so, and what direction of gravitational force would someone feel if they put their hand near it?
[Answer]
**The problem isn't speed, it is mass**
While spinning black holes and any spinning massive objects do drag space around it using the frame dragging effect, this is only noticible on very massive objects. A few kilograms won't produce a noticable effect. The Earth is much more massive even taking into account the difference in speed and the effect of that on the Earth is difficult to measure, since it is so small. You must either observe very large objects or build very sensitive instruments.
So you probably would notice no gravity effects.
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I've read different accounts of the largest bear ever shot, the size of polar bears before climate change, and the extinct variations of cave bear and the short face bear. They all top out near 3m in height and around a metric ton.
What environmental factors would need to stay consistent and what morphological changes would take place for a bear species to grow large enough to prey on mega-fauna like the woolly mammoth? Or are they already at the size limit for carnivorous mammals?
For example, when polar bears split from grizzly bears to live in the Arctic, their fur, skin, paws, limb ratio, head shape and diet changed to adapt to live on and around ice flows and glaciers. Increased size also helped with thermoregulation on land and in the water, as well as when competing for a mate.
[Answer]
**Simbakubwa kutokaafrika** had a carnivore-like build but was 1000 pounds larger than a polar bear.
<https://www.youtube.com/watch?v=5BH4hYITdn8>
[](https://i.stack.imgur.com/Ovk6W.jpg)
<https://markanderschannel.com/big-cats/lion-hyaenodon-bones-found-in-kenya-simbakubwa-kutokaafrika-video/>
>
> African lions weigh up to 550 pounds or 250 kilograms. The largest
> land carnivore living today on average is the polar bear. The average
> weight of a mature polar bear male is between 900 and 1,500 pounds.
> The heaviest recorded polar bear was 2,200 pounds. Simbakubwa
> kutokaafrika was the same length as a polar bear, 8 feet from snout to
> rump but outweighed the largest polar bear ever by weighing 3,300
> pounds, over a thousand pounds bigger than the biggest polar bear ever
> recorded.
>
>
>
That also puts it larger than the short faced bears. This creature was a hyaenodon from the Miocene; technically a time before order Carnivora existed. But it had what seems to me a basic carnivoran body plan. So here you go - a carnivore 1000 pounds heavier than the big bears.
Why so big? Not thermoregulation polar bear style - these things would really have struggled to stay cool at this size in a warm climate. My guess is that large size means large physiologic reserves and the ability to capitalize on briefly and intermittently available windfalls of meat - dead megafauna. It does not have to bring down prey. It just needs to scare off competition. When Simbakubwa shows up, lesser predators and scavengers vacate the premises. When a really big animal dies or is killed, the giant hyaenadon can eat the whole thing themselves. My guess also is that hyaenadons were not social in the manner of modern carnivores who do the same thing, but spread the body mass over multiple related individuals.
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A funny thing about this image - I thought it was a real statue at the Nairobi national museum. I was surprised they would have depicted the animal's human companion so lovingly. Anders on his channel states it is a 3d render. No artist is credited so maybe Anders himself? A very Frazetta feel about these two.
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I know this question is kinda weird, but there is a real problem with prosthesis and implants inside or outside of you, normally they need a source of energy.
If you extract the energy from your own body the same way a organ would do (like an artificial heart), you wouldn't need to concern about a battery inside you that could explode or just stop working.
Also, this maybe could led to biotechnological prosthesis that wouldn't need to rely on electronic parts to execute functions or simulate touch at some degree.
Well, the best I can think of is an [artificial muscle made by the MIT that can generate energy from being exposed to humidity](https://youtu.be/cXujS-Nr7o0). So, exposing it to your humidity (sweat or a little of blood).
[Answer]
Using micro elecrics.
[https://www.sciencedaily.com/releases/2017/09/170908205453.htm#:~:text=To%20produce%20hydropower%20on%20a%20much%20smaller%20scale%2C%20Chinese%20scientists,in%20the%20journal%20Angewandte%20Chemie.](https://www.sciencedaily.com/releases/2017/09/170908205453.htm#:%7E:text=To%20produce%20hydropower%20on%20a%20much%20smaller%20scale%2C%20Chinese%20scientists,in%20the%20journal%20Angewandte%20Chemie.)\*
This "boasts" a 20% efficiency ratio, which is kind of high for such small systems (according to the article). Besides the flow of blood it can also use the flow of fluids caused by your movements, so in some cases it can be used to create energy out od your movement (Stillsuits anyone?)
In support of DyingLight's answer, chemical power generation using sugars seems a solid option: <https://www.google.com/amp/s/www.rbth.com/science-and-tech/327650-russian-scientists-electricity-from-blood/amp>
Note that this wont be powering anything like a full prostetic leg, just something small like a pacemaker.
Then for something outlandish that requires some genetic engineering: muscle powered dynamo's.
A muscle is essentially two "plates" with a fiber in the middle. This fiber has arms which can use ATP to grab extrusions on the plates and pull itself onwards. In the middle of the muscle all arms can grab the plates while at the maximum extention/contraction states not all arms can help pull, which reduces the maximum muscle strength at those positions.
But with some genetic engineering, you can put the plates on a circle that turns either a dynamo or more directly some gears. With a circle the arms will always have full access and can generate as much power as any muscle. So if you put enough of them in a row you can turn the biochemical muscle energy into the kinetic/electric energy you need.
\*I have no idea of the accuracy of this article.
[Answer]
## [Glucose Fuel Cells](http://large.stanford.edu/courses/2014/ph240/ho2/)
The glucose in our blood can be used in fuel cells to generate electricity. The reactions involved look like this:
C6H12O6 + H2O → C6H12O7 + 2H+ + 2e- + O2 + 2H+ + 2e- → H2O
Different options for designing the system are solid-state fuel cells, solid-state fuel cells that use enzymes to achieve better efficiencies, and actually living fuel cells, which use microbes.
That second design has demonstrated power densities of up to 3.6W/cm^2. That's rather pitiful, but keep in mind that those are prototypes.
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[Question]
[
I want to create a locale (hopefully a whole planet?), where the ocean is breathable. I was looking at perfluorocarbons, so the liquid part is at least possible(?)
Is there any way to create a world where the oceans might be like a natural version of perfluorocarbon or some other naturally occurring breathable liquid for humans?
I know that breathing the liquid is hard for the lungs to circulate in and out (and hypercapnia is an issue), but for now let’s focus on the environment. Thank you.
Edit: How about with a little handwavium?
[Answer]
The main issue is that, while carbon is [pretty common](https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements) in the universe, being the 4th one for abundance in the Milky Way, fluorine is much more scarce.
Therefore making a whole ocean of perfluorocarbon seems highly unlikely, because with the known abundances it would be diluted in something much more available. And those are not equivalent to perfluorocarbons when it comes to breathing in them.
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[
I was thinking about the concept of space whales that are presented in some sci-fi universes. Usually, their origin is either unexplained or explained in some pseudo-magical way. As an example, it is good to present void whales from [Warhammer universe](https://warhammer40k.fandom.com/wiki/Void_Whale).
There were some good questions that were asked about them in the past: [one](https://worldbuilding.stackexchange.com/questions/87444/space-whales-how-to-survive), [two](https://worldbuilding.stackexchange.com/questions/87443/space-whales-how-to-move), but I think they are missing some key points to make these whales at least semi-realistic. There is even almost the same [question](https://worldbuilding.stackexchange.com/questions/131871/anatomically-correct-space-whales) as mine, but I believe there is something more to say about the idea of the void whales.
For example, there is no way to store enough energy in chemical form to travel between stars, as it will require **very** big amount of time to perform such a journey. The option to harvest energy from the stars seems promising, but the radiation energy density drops at least as the inverse square of the distance from the star, so there is no way to keep harvesting it on the way between them.
In my opinion, the only type of energy that is valuable to store and harvested in outer space is nuclear energy. At first, it may sound unrealistic even alongside space whales, but let me explain the details.
This is the reality check question, so I am asking, whoever will read all this nonsense below, to comment on how to improve my space whales and how to make them some more realistic. If realistic is the right word for a space whale. Constructive criticism is also very welcome.
[](https://i.stack.imgur.com/HjDzk.jpg)
The questions that really need an answer:
1. What form does the void whale have? (Spherical might not be the best answer)
2. How did the space whale evolve itself into existence?
Below is the description of some key aspects of the space whales as I see them.
### Power source
TL;DR
They are harvesting uranium from space dust and fueling their organic nuclear reactor.
---
There are two elements(encountered in nature) that are known to humans that may be useful as an energy source: [Uranium](https://en.wikipedia.org/wiki/Nuclear_fuel_cycle) and [Thorium](https://en.wikipedia.org/wiki/Thorium_fuel_cycle). There are two problems with the nuclear reaction inside a living creature: radiation and temperature. But the radiation may be harvested as thermal energy and the temperature is just a direct energy source that can allow the creature to convert nuclear energy to chemical energy to power its muscles(or whatever it has instead of them), brain(if it has one) and to stay alive in general. [There are](https://en.wikipedia.org/wiki/Radiotrophic_fungus) some creatures that have such mechanisms, so void whale might use some of them. The most convenient part about a nuclear reactor is that it does not have extreme temperatures inside of it, comparing with a thermonuclear reactor, for example.
Another problem is that this whale must have the ability to enrich its nuclear fuel. Luckily, the centrifuge, which is not a very realistic semi-organic device by a long shot, is not the only way to do the enrichment. [Diffusion](https://en.wikipedia.org/wiki/Enriched_uranium#Diffusion_techniques) is a slower, but more feasible way, to do it inside the void whale.
The question that is not yet answered is how this whale will obtain enough uranium and thorium in outer space. The answer is that all elements are [belived](https://en.wikipedia.org/wiki/Nucleosynthesis#Timeline) to be formed during the stars' life cycle, so there are some places in space where these elements are presented and whales can harvest them, such as supernovas or protoplanetary discs fro example.
### Movement
TL;DR
Jet force and relativistic time slowing are the keys to a successful space journey.
---
In my opinion, there are not many things to choose from. Jet force is the only known way to travel fast in space. There are a lot of things which space whale might want to get rid of. Radioactive waste is not a very smart thing to throw away as it might be used as a radiation source to harvest energy from it. Also if the whale's chemistry is complicated enough it might have a closed fuel cycle inside of it.
There is no friction in space, so the whale might want to throw away all stuff it found during his feeding process, which is useless for it. As it needs to process a big amount of matter to get fuel there will be no lack of jank to throw away. It may be enough to make it possible for it to reach high velocities that are required to surpass the gravitation of planets and stars.
One interesting thing about high velocities that the body that has them (even if they are close to light speed) does not care about them. The acceleration is the thing that matters, so in *theory* nothing fundamentally forbids the whale to move on near light speed as long as nothing will collide with it.
It opened very interesting opportunities for them. For example, if the whale can hibernate itself indefinitely long, then after it arrives so much time may pass then all radioactive material it stores had decayed a long time ago, so their half-life time would be the upper boundary of whale's travel time. But if the speed is big enough (relatively to destination object speed) the whale's time slows and this effect allows the whale to travel even between galaxies.
### Harvesting
TL;DR
The mouth is crucial because void whales use jet force thus having a preferred direction of incoming dust.
---
The obvious decision is to make a whale's surface to be able to absorb dust particles, so the harvesting process will take advantage of the whale's own gravity. But as the whale is able to move using jet force it is convenient to give it something mouth-like.
The most valuable places for the void whale to pasture is protoplanet discs around stars. They are rich in elements and denser than the remainings of the exploded stars, where all those elements were born. So the mouth should play the role of a funnel. As the possibility of hibernation already mentioned, a whale might as well have the ability to close and open its mouth.
Another possibility is to let the whale the ability to harvest on asteroid fields. Then its mouth should play the role of blender for rocks.
This breaks the spherical symmetry of the whale, so it might have a complex form. One may say that the spheric form is the best form to minimize power leaks from the thermal radiation, but I think if an organism uses nuclear power as a food source it is ok for it to lose that amount of energy. The hibernation state might be a little different as the whale will be in such a state for **really** long time.
### Navigation
TL;DR
Spectral decomposition to search for needed elements. Gravitational field detection to use the gravitational maneuver.
---
The void whale should have some way to locate the food sources. It must have a complex brain to analyze light from the stars and perform spectral decomposition to figure out where it should go after this protoplanetary disk is finished.
The most convenient way to see light from all directions is to use your own surface as a giant eye. The problem with this solution is that light must be focused to analyze weak sources of light that are far away, so maybe there will be places on the whale's surface that will act as lenses and mirrors, to magnify light from distant stars.
Also, the void whale might use some knowledge about gravitational fields around it, so it may use the gravitational maneuver to accelerate itself with little to no loss of jank mass.
### Reproduction
TL;DR
Not sexual reproduction as the population is very sparse. Spouse and parthenogenesis are good alternatives.
---
The void whale population is **very** sparse, so it might take a very long time for pair of whales to meet for them to have sexual reproduction. One way to make this problem a little bit less harsh is for them to breed in the same way as fish do. The female whale is making a capsule with all ingredients that are needed for a new whale to develop and then the capsule is waiting until the male whale will find it. The problem is that it is no way to locate such a tiny object for an organism designed for finding protoplanetary disks.
The [sporogenesis](https://en.wikipedia.org/wiki/Sporogenesis) looks very promising as the spore might contain fuel and other elements to sustain itself while traveling among stars and develop into a new void whale if it finds itself in an element-rich place. Another plus is that they are starting in a hibernation state so they will have a chance to live long enough to encounter a nice place even if it is very far away.
Also, the [parthenogenesis](https://en.wikipedia.org/wiki/Parthenogenesis) is a good way to reproduce as it developing from species that use sexual reproduction, which is better from the evolutionary point of view.
So the most *realistic* way for the void whale to reproduce is to harvest a lot of useful materials, form spores, and then eject them with great speed for them to travel as far as possible. This way to reproduce also might form a defending mechanism to dive another whale away from the food/fuel source. Then these spores wait for the good times and during this waiting, they may be fertilized.
### Evolution
This is the most tricky part of the void whale design. How this enormous, complex creature evolve itself into existence?
In my opinion, is that the most complex part is the biological nuclear reactor inside of them. It is known only about [one](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) natural nuclear reactor on Earth. But maybe if our uranium was reacher and there was more of it, such nuclear reactors might be very common.
The chemistry inside such the void whale might be very complex and maybe it uses some other organisms to sustain itself. As was mentioned above there is a fungus that transforms radiation(some of it) into chemical energy, so the void whale may use it the same way humans use bacteria in intestines.
The water might be used as a moderator to start the nuclear reaction if the fuel is rich enough. So on the planet where uranium is common, rich with the right isotope, and life is used to radiation there might be species that just eating uranium and then the flora inside of them are converting heat and radiation to whatever is needed for this creature to move, jump and search for more. As uranium is heavy then the creature should be big and strong and might live in the water.
Then it needs to take one more step and go to space. It is not possible without some planet-wide cataclysm. It should not be too bad for life to stay alive, but impactful enough to open a way for organisms to slowly adapt to vacuum.
And in the end, there is another step where these whales will finally go to space and spread among countless stars and consume the neverending number of unborn planets.
---
P.S. Thanks for reading all this mess. English is not my first language, so let me apologize in advance for any mistake I have made in my question.
[Answer]
**Colonial heat eater based on a comet.**
I laid out some ideas for a void creature here: [What would the biochemistry of a vacuum dwelling creature look like?](https://worldbuilding.stackexchange.com/questions/122111/what-would-the-biochemistry-of-a-vacuum-dwelling-creature-look-like/122211#122211)
1. **Colonial creature.** This would start with autotrophic archaebacteria colonizing a comet. The comet provides substrate to build bodies out of and shielding from hard radiation. I can imagine different populations of archons would serve different functions in the mass, which would be something like a Kombucha mushroom, in space.
This answers the question of evolution too. Some archons of planetary origina wind up on a comet (big impact? spores blown off the planet?) and get to evolve unharassed for millions of years.
2. **Heat eater.** It is hard for me to imagine biologically catalyzed / contained fission or fusion. [True for others here as well](https://worldbuilding.stackexchange.com/questions/165567/is-it-possible-for-a-creature-to-exist-as-a-biological-nuclear-reactor). Capturing that sort of energy chemically is super tricky. But isotopic decay generates heat, and heat powered biology seems a doable deal to me. I thought this scheme for phase change powering ATP pump was pretty slick even though it did not get a lot of love.
[Biochemistry of Plants harnessing heat-energy when blue-shifted light is scarce](https://worldbuilding.stackexchange.com/questions/103111/biochemistry-of-plants-harnessing-heat-energy-when-blue-shifted-light-is-scarce/103119#103119)
Your whale uses uranium when it can get it. In interstellar space it captures cosmigenic radioactive isotopes swept from the void. When it is near a star those isotopes might be generated in its own mass (the forward area which acts as a radiation shield). Or it harvests heat energy directly from the star if it is close enough.
3. **Shape**
I envision it as a round front made of the comet which is its core, with a tail behind. Most of the biology is in the tail which is oriented to keep the comet in front as a radiation shield / sponge. The tail can be used to steer by outgassing volatiles.
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[Question]
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
---
This question does not appear to be about **worldbuilding**, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help).
Closed 3 years ago.
[Improve this question](/posts/191906/edit)
Let's say we start the simulation on Earth in 1900. And we use classical physics unless the participants start looking at tiny objects. This allows us to reduce the amount of memory needed to run the simulation. So physics is a compression algorithm.
All good so far.
But how much **human** history do we need to create for a consistent world. Perhaps 150 years of high fidelity history dwindling away in fidelity to 10,000 years.
In this simulation the archaeology is also like a quantum observation and the missing bits of history only become certain as they are unearthed.
In this world if you look for bad histories you will more likely find bad histories and if you look for good ones you will more likely find good ones. And a story might be written where competing interests search for histories that favour their current presents and futures.
There may be dark forces trying to unearth sinister historical conspiracies that they can manipulate to reinforce their power, and good forces trying to find golden ages and righteous societies and groups that shine a light on the present and future.
A simple example of this would be finding a treasure chest on an Island then opening it to find gold or keepsakes. This would effect the present.
Are there mechanisms that would allow the newly discovered past to effect the past more generally than just the specific past unearthed, or just on the current understanding and influence of recorded history?
eg. someone discovers ancient texts referring Yetis, and so increases the probability that yeti's will be discovered in a very remote part of the Himalayas.
[Answer]
>
> /There may be dark forces trying to unearth sinister historical
> conspiracies that they can manipulate to reinforce their power, and
> good forces trying to find golden ages and righteous societies and
> groups that shine a light on the present and future.
>
>
> Has this trope any literary precedent?/
>
>
>
**Yes.** It happens plenty in the real world. As regards literary precedent, George Orwell's 1984 is a fine example.
<https://www.cliffsnotes.com/literature/n/1984/critical-essays/the-mutability-of-history>
>
> One of the issues raised in 1984 is the idea that history is mutable
> or changeable, that truth is what the Party deems it to be, and that
> the truths found in history are the bases of the principles of the
> future. Some Fascist German leaders of the time boasted that if you
> tell a lie loud enough and often enough, people will accept it as
> truth. The Stalinists perfected this modus operandi by re-writing
> people and events in and out of history or distorting historical facts
> to suit the Party's purposes. "Who controls the past controls the
> future: who controls the present controls the past," runs the Party
> slogan in 1984
>
>
>
What timely words! In any case you do not need to be in a simulation to have persons attempt to manipulate history for their own ends, nefarious or enlightened.
.
[Answer]
## Akashic Record Vs. 'There is no Real Time'
So I once heard a theoretical physicist say that time might be a fluctuating wave function, and that we're all time travelers. Going forward or backwards in time appears identical, as it is only change. There IS no past, and it is only our perception of change we experience. So in this model, you have no problem. There is nothing to find. Every physical piece of evidence is a material item from the starting conditions that either is or isn't there. There IS no before.
I don't think that's what you want. The Akashic record is a proposed structure by spiritualists, a giant file containing the previous states of everything in the entire universe. It is literally a store of the past. Only in your model, the books there are largely blank until you look at them.
The problem is that I think you want the physical evidence of ancient things to materialize out of no where as people find them. This implies that much of the CURRENT reality is a low resolution approximated reality, waiting to fill in. People are everywhere, and have traveled everywhere, so they would have already observed almost everything. To get what you want, people would need to dig deep and travel to abandoned and inhospitable parts of the world where human observation has never gone.
It also means that what people want is what they find. Archaeology is usually about surprises. People don't know what they'll find, but often try to make the evidence match their preconceptions. Funny how new discoveries seem to invalidate the old ones.
You may have people who can actually CHANGE history, not merely create it. Any property of a piece of matter can be questioned. Look up [Piltdown Man](https://en.wikipedia.org/wiki/Piltdown_Man#:%7E:text=The%20Piltdown%20Man%20was%20a,a%20previously%20unknown%20early%20human.). Archaeologists believed they had proof of one path of ancient history. It was unquestionable - until it wasn't. Perhaps the constant search for new reality is even able to alter the existing record. Carbon dating proved the fossil was 100 million years old? Oh, wait, it was exposed to a fire, that's wrong. This bone is clearly one species - oh, wait, now it was all a misinterpretation. So even 'Fixed' history is malleable.
But I doubt you'll get much actual malevolent benefit. Even Nazis seeking proof of an ancient Aryan master world of Thule would need to convince people it was relevant. Popular opinion might invalidate the reality of what they found. An ancient Aryan bell space ship might become the visiting ship of a great black African empire with the right spin and a change in science.
Or maybe the past IS real for these folks, a place you could travel to. If so, like opening a portal to an area in a game that hasn't been created, there would be buffering problems until reality shifted in. But most of reality requires too many individual details for the observer to make them on their own. A master creator/computer would need to intervene to handle the details. Malevolence could enter in if there is more than ONE master computer, and their opportunity to alter fixed reality is only there at the moment of observation. So you could have devils or angels (so to speak) trying to make their plug and using mankind as their proxies.
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[Question]
[
This idea is mainly based around the self-healing concrete idea that has appeared in the past and scientific posts have been made about the self healing concrete using bacteria to self heal cracks. What my question asks is whether or not this could apply to a vertical structure such as a castle wall and whether it would be practical.
Recognizing that the bacteria in order to produce the limestone used to fill the cracks, water is needed in order to activate, I thought perhaps a rain or mist would work. Granted this would mean that a castle with this sort of function would only self heal with applied water or would be dependent upon the weather but still my thought process.
Another requirement for the bacteria is the sugar or food component which the website I provide uses calcium lactate so I suppose part of my question is whether or not this would work as well for castle walls.
Also to clarify, the healing component I'm trying to apply for this question is the outer defensive castle walls of this hypothetical castle that is able to self heal using mainly impressive science, or at least as scientifically based as possible before I resort to magic into this idea specifically.
<https://www.cnn.com/2015/05/14/tech/bioconcrete-delft-jonkers/index.html>
Thank any and everyone again for providing any sort of answer/input.
(Edit)
The castle I have in mind would be made of concrete at least partially and I do believe this is an example of a castle that is made of concrete and some parts reinforced concrete. Concrete itself wouldn't require steel as I've come to understand it.
<https://buckslib.org/the-mercer-museum-castles-made-of-concrete/>
Would it still be possible for a concrete castle above ground and not in the water to employ this sort of idea hypothetically?
[Answer]
Castle walls are not made of concrete. At least not the castles built during the castle golden age: they are made by stones held together by some cement, where the cement act as a binder.
Your bacteria seems at most capable of repairing the cement (if made out of the right material), not the stones.
Also please note that concrete contains a steel element which is untouched by this bacteria and which is a key component for ensuring the overall behavior under load.
[Answer]
it feel similar like Roman Concrete just want to share, dont know the component you bring can work for your purpose or not, but at least this may can be an alternative.
from: <https://www.nature.com/news/seawater-is-the-secret-to-long-lasting-roman-concrete-1.22231>
>
> **Seawater is the secret to long-lasting Roman concrete**
>
>
>
>
> Ancient Romans built concrete sea walls that have withstood pounding
> ocean waves for more than 2,000 years. Now, an international team has
> discovered a clue to the concrete’s longevity: a rare mineral forms
> during chemical reactions between the concrete and seawater that
> strengthen the material.
>
>
> Structural engineers might be able to use these insights to make
> stronger, more-sustainable concrete, says team leader Marie Jackson, a
> geologist at the University of Utah in Salt Lake City. She and her
> colleagues report their findings on 3 July in American Mineralogist1.
>
>
> Modern concrete uses a paste of water and Portland cement, a fine
> powder made mostly of limestone and clay, to hold together small
> rocks. But it degrades within decades, especially in harsh marine
> environments. Instead of Portland cement, the Roman concrete used a
> mix of volcanic ash and lime to bind rock fragments. The Roman scholar
> Pliny the Elder described underwater concrete structures that become
> “a single stone mass, impregnable to the waves and every day
> stronger.” This piqued Jackson’s interest. “For me the question was,
> how does this material become a rock?” she says.
>
>
> In earlier work, Jackson and colleagues reported some of the unusual
> chemistry of Roman concrete, such as the presence of a rare mineral
> known as aluminium tobermorite2. For the new study, the scientists
> took samples of Roman harbour concrete to the Advanced Light Source,
> an X-ray synchrotron at Lawrence Berkeley National Laboratory in
> Berkeley, California, and mapped out the location of minerals in the
> samples.
>
>
> The researchers found a silicate mineral called phillipsite, which is
> common in volcanic rocks, with crystals of aluminium tobermorite
> growing from it. Tobermorite seems to have grown from the phillipsite
> when seawater washed through the concrete, turning it more alkaline.
> “It's a very rare occurrence in the Earth,” Jackson says. Such
> crystallization has only been seen in places such as the Surtsey
> volcano in Iceland. As tobermorite grows, it may strengthen the
> concrete because its long, plate-like crystals allow the material to
> flex rather than shatter when stressed.
>
>
> Marie Jackson
>
>
> A scanning electron microscope image of minerals within Roman
> concrete. Applying ancient knowledge
>
>
> Modern concrete-makers could learn from the ancient Romans’ knowledge,
> says Nele De Belie, a materials engineer at Ghent University in
> Belgium. She and her colleagues have used materials such as fly ash,
> produced during the burning of coal, to give concrete ‘self-healing’
> properties, whereby the material closes up cracks after they form3.
> Fly ash is similar to the volcanic ash that Romans used in their mix.
>
>
> Jackson has been working to recreate the Romans’ concrete recipe in
> the lab. She is also a consultant for a cement company in Nevada that
> is using volcanic ash from the western United States to formulate such
> concrete.
>
>
> “I’m not saying this would be the concrete that would be used in
> everyday infrastucture,” she says. “But for materials like sea walls,
> we could formulate mixtures with lime and volcanic ash materials in
> the way that the Romans did.” The Romans may have got their ideas from
> studying how ash from volcanic eruptions crystallized into durable
> rock, Jackson says.
>
>
>
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So I was watching Issac Arthur videos recently, about colonizing the other planets of our solar system. And it was pointed out that Neptune and Venus have atmospheres and gravity such that an airship could be built that would float in the atmosphere, and allow people inside to live in earth-like gravity.
Which got me to thinking- those airship cities would be so much cooler if people could go outside, stand on the deck, and breath the atmosphere.
But I'm not much good with science. So is it possible, scientifically speaking, for a gas giant / ice giant to have an atmosphere people could breath, at a gravity people could be comfortable in? Is there a possible gas giant / ice giant configuration that would allow that at some point?
[Answer]
Oxygen is one of the most common elements in the universe and in planets. The Earth is nearly 30% oxygen in mass - and I mean the whole planet, not just the atmosphere.
However, there are a few problems when it comes to having available oxygen in a gas giant:
1. Oxygen is one of the most reactive elements in the table. Not being a picker, it will bind to almost anything. And it will stay bound. Most of the oxygen in Jupiter for example is in water molecules.
2. Oxygen may be one of the most common elements in the universe as I said above, but it is still far behind hydrogen. Gas giants are mostly hydrogen, so practically all the oxygen will bind to that to form water.
3. Then there are ice giants, like Neptune and Uranus. [According to Wikipedia](https://en.wikipedia.org/wiki/Ice_giant), an ice giant is *"a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur."* But then the article for Uranus states that its atmosphere is still mostly hydrogen and helium, with some methane in it. Oxygen is about as heavy as methane, but since it binds to other atoms it becomes heavy and precipitates, so you would only find oxygen at depths were you'd die from other causes. Even then it would not be O2.
The reason we have so much breathable oxygen in our own atmosphere is basically a fluke. If you have that much oxygen in a lifeless planet it is unlikely to develop life because oxygen is toxic, speciallly to microbes. We had life kickstarted in oceans, where oxygen concentrations are low, and that life [oxygenated the world](https://en.wikipedia.org/wiki/Great_Oxidation_Event). Thay also led to many lifeforms disappearing due to the toxicity involved but hey, you can't have an omelet without causing a major extinction event.
[Answer]
Welcome to Worldbuilding SE, my friend! Although I am a bit of a newbie to the site myself, I think you will fit in here fine!
This is a very basic answer but here goes nothing lol...
**TL;DR**
No, we don’t have enough oxygen.
**Long version:**
The only reason we have oxygen here on earth is because life brought it, as pointed out by @cowlinator.
Thus, we would have to artificially introduce enough oxygen to support life. The problem is we don’t really have enough oxygen to spare.
Neptune is ~17 times larger than Earth, so we would need possibly 20-30x the amount of oxygen, which we don’t have...
There are many ways to make oxygen, but all of the, require pre-existing oxygen:
* Photosynthesis requires carbon di**oxide**.
* That cool manganese/hydrogen peroxide trick, once again, requires hydrogen per**oxide**.
* etc. etc.
So the only conceivable way to do this would be through subatomic rearrangements, where you rearrange the electrons, protons and neutrons in an atom to create a new one. Since this is completely impossible by today’s technology, I’m going to have to say...
# No, it not possible...
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**This question already has answers here**:
[orbital ring in slow decay, what's the fallout?](/questions/181054/orbital-ring-in-slow-decay-whats-the-fallout)
(3 answers)
Closed 3 years ago.
I'm working on a story where an orbital ring situated in LEO above the equator of an earth-like planet is destroyed which is a calamity for the species that used it. The ring is essential for them and most of their settlements are along the equator where they have easy access to it.
The ring is composed on an inner part that spins at the speed necessary to keep it in orbit and a geostationary part levitated over the spinning part that is connected to the surface with tethers/ space elevators. It is as heavy as needed to wreck appropriate havoc.
Edit: Quick sketch (not to scale)
[](https://i.stack.imgur.com/2cmBm.png)
I had envisioned that it gets destroyed or damaged in a manner that de-orbits the ring, resulting in most of the material falling down and destroying the settlements below it. I also imagined that some of the material remained in orbit and continuously rained down as meteors, making the equator region inhabitable and hazardous to cross. Is that at all realistic?
Edit 2: Not sure if this is allowed since it's technically a different question, but on a order of magnitude how quickly would this thing come down? If you know someone who works up on the ring station and they phone you when they notice it's breaking, do you have time to pack up your car and leave? Do you have time to jump in your car and leave?
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**Probably not much damage**
After watching the linked video, there are two main points to consider (which are both noted in the video):
1. The "geostationary bits" are not actually "geo" stationary, they are just plain stationary, being supported by "upwards" force from the inner ring. If something goes wrong and these parts are separated from the orbital ring then they will fall straight down to the point directly beneath them on the planet. There may be some deviation due to atmospheric effects (so the population centre on the surface would sensibly be built about 50-100 km north or south of the connection point) but the damage will be from an object falling at terminal velocity in the atmosphere. Note that terminal velocity in an atmosphere is very different to orbital velocity - the damage these things will do if no safety measures operate (see below) will be equivalent to an object of the same size being dropped from an aircraft. Time from failure until impact will be effectively instantaneous for the section closest to the ground and a few minutes for the section that was up in space *if the safety equipment fails*. If the safety equipment (big parachutes) work then the larger sections will descend at human-survivable speeds over maybe 30-60 minutes, longer with proportionally larger parachutes. Exact timing will depend on lots of variables - density of atmosphere, depth of atmosphere, density and aerodynamic profile of each component.
2. In order to support the stationary parts, the inner ring is a thin wire moving at *more* than orbital speed. An intelligently designed ring from a safety viewpoint will be made of a wire with a thickness and composition such that if it re-enters the atmosphere it will burn up rather than survive re-entry and impact the ground. However, it will not be re-entering in a hurry as it is being spun at greater speed than is required for its orbital height in order to support the stationary elements. Assuming that the ring fragments, most sections of cable will move into a higher, albeit unstable, orbit. Expect them to re-enter individually over the next few years unless they are collected up for re-use by then.
The only way to create the level of catastrophe you have in mind is to have a civilisation completely fail to consider failure modes at all. I seriously question how anyone could survive the initial construction process if they did not consider this - something always goes wrong at some point during a major construction such as this - but if the plot demands it then...
* Put the major population centres directly under the terminus of the cable - basically like building a really compact city and then building a major airport on a roof on top of all the buildings in terms of common sense.
* Do not include any parachutes on stationary elements. (If the destruction is due to sabotage then this one can be made believable by having the terrorists sabotage the parachutes.)
* Make the inner ring really thick and heat resistant so it can survive re-entry to do the maximum damage - heat tiles surrounding a tungsten / depleted uranium core a few metres in diameter should do the trick.
You may be interested in reading The Sundering - Book Two of [Dread Empire's Fall](https://en.wikipedia.org/wiki/Dread_Empire%27s_Fall) by Walter Jon Williams. The construction and emergency measures of the Zanshaa ring are described in detail and are a significant plot element.
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## Yes that's fairly realistic.
The level of damage and devastation would depend on the mass of the fragments dropping from orbit. I don't have the calculations on hand but i'm sure they've been done. However the general theory is sound - a *shredded* or *exploded* ring would lead to fragments in decaying orbits, and interaction between fragments would potentially lead to further decaying orbits as time went on. This kind of 'orbital debris cloud' is something that is generally considered to be Incredibly Bad and is actually a major worry for space exploration as we clutter our own LEO with random stuff.
One note is that if most of the debris falls down initially, you might not have enough left in orbit to produce the 'constant meteor danger'. You need a fair amount of stuff in orbit to produce the decaying orbits (unless there's other factors involved like Weird Gravity or Malicious Intervention) required for constant meteor danger, and if most of the material fell initially and you still had enough left in orbit to do that, the initial fall would be an extinction event (unless the initial fall was reduced to quite fine chunks).
You can solve this fairly simply - just have only 'some' of the debris fall initially, leaving enough in orbit for meteors and still enough dropping on people to make the initial fall (the Fall?) notable and cataclysmic.
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My apologies for the extra long title, so let's get to the point. There is an Earth-like planet with a very dry personality. Six to ten percent of the surface is water, averaging in at 30-100 meters deep. In turn, 79% of the dry land is salt, suggesting that this was once a waterworld but, due to migration, got right to the inner boundary of the habitable zone and as a result lost most of its water.
With such a near-absolute exposure to air, would the plate tectonics act any differently from those on Earth, a planet in which water makes up the majority of the surface.
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### The plates will move slower.
Some observations from [*Plate Tectonics Driving Mechanisms: Some Simple Rules that Explain Why the Plates Move the Way They Do*](https://www.researchgate.net/publication/264825668_Plate_Tectonics_Driving_Mechanisms_Some_Simple_Rules_that_Explain_Why_the_Plates_Move_the_Way_They_Do) by Christopher Robert Scotese, Northwestern University:
* Oceanic plates move faster than continental plates.
+ Oceanic plates tend to have ridges (pushing) and attached subducting slabs (pulling).
+ At the base of oceanic plates in the LVZ (low velocity zone), a region of partial
melting that provides "lubrication" at the base of the plates.
* Plates with a large area of continent move slowly (e.g., Eurasia) because they have a deep
continental keel connected to the mantle.
+ For this reason continental plates are more likely to be affected by mantle flow.
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## The plates will move slower
Assuming by less water you mean less oceanic crust, tectonics will be slower, continetal plates generally move slower. Oceanic plate is thinner and lighter than continental plates and thus can move a lot faster, it is just basic physics the same force can move a lighter object faster. In addition continent to continent boundaries suffer from a lot more resistance and end up moving slower since continental plates cannot subduct under one another. This also means such a planet **should be a lot more mountainous**. It is not coincidence the largest mountains on earth on one continental/continetal boundaries. but at the same time it will have less volcanoes since volcanoes arise primarily from subduction. Expect high turnover on seafloor, which means the volcanoes you do have will be larger. So **fewer but larger/taller volcanoes/volcanic ranges**.
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How old does a galaxy need to be to harbor life for prolonged periods of time? Our galaxy was 8 or 9 billion years old by the time life emerged on Earth, so the lower boundary must be younger than that. However, young galaxies are not good places for life, as they contain many massive O and B type stars that explode violently in supernovae and can destroy a planet's atmosphere. Very old galaxies aren't good places for life to develop either, as they would have a higher percentage of red and brown dwarfs with masses less than 0.2 solar masses, and within orbit around those stars tidal heating would occour within the habitable zone of the star and squeeze any volatiles like water off the planet. But how old does a galaxy have to actually be to sustain life?
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I would challenge the premise that a young galaxy is a dangerous place for a habitable planet. Bear in mind that while higher star formation rates mean a greater quantity of hot O and B stars, and therefore supernovae, these objects are still quite rare. For instance, in the Milky Way, [only $10^{-5}$% of all stars are O stars](https://en.wikipedia.org/wiki/O-type_main-sequence_star). Even in an epoch of high star formation - which is generally believed to have [peaked in the universe at a redshift $z\sim2$](https://astrobites.org/2016/11/11/the-changing-star-formation-rate-of-the-universe/), or [just under 3 billion years after the Big Bang](http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html) - it's unlikely that many would be nearby.
To plug in some numbers: [the local mean stellar number density is $n\sim0.1\;\text{pc}^{3}$](https://physics.stackexchange.com/a/393902/56299), implying a mean inter-star distance of about 7 light-years, or just under twice the distance to Proxima Centauri. If we increase the stellar number density by two orders of magnitude, we decrease the mean distance by a factor of 5. But even this means that there should only be one O star within about 100 parsecs of the any given star - likely too far to cause problems. If I remember correctly, 8 parsecs is the distance at which a supernova becomes dangerous, and it's highly unlikely that that O star will be that close.
The other consideration is whether the elements for life would exist at a given time. [It seems like we only need a few billion years for the heavier elements](https://www.forbes.com/sites/startswithabang/2018/11/28/what-was-it-like-when-the-first-habitable-planets-formed/#6cc630ba61eb) to form in large enough quantities to become abundant in the nebulae that form Population II stars and their planets.
Putting this altogether: I think it's quite reasonable for habitable planets to begin to form around 3-4 billion years after the Big Bang, a little bit after the star formation peak. Certainly, the longer you wait, the better the odds; planets will become more and more enriched with carbon and oxygen, and star formation rates will decrease.
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**Depends on the largest question of context or how you set your world.**
If you see intelligent life which we can interact with and understand as the result of evolution and as things that evolved in their own unique environment then it won't matter.
**Because it's basically life only happens as something something life starts happening and natural selection takes care of the rest.**
Have a planet with no water or atmosphere or with acid rain on ammonia based air or even the sun.
Just time and the existence of a platform, planet or asteroid or something like that, will mean that life forms will emerge and with time will be intelligent.
The part about intelligent life here means basically human like or human comparable creatures.
Like 99% of all human writing is. This is kind of a must because anything produced by a human is human produced so people who think this story is alien either wrong or just being metaphorical.
Thing point is important as we can only interact with stuff that have bodies and with a brain and thoughts and motives like us...etc.
Think of a pet. You can life with them. But can you keep a rock, tree, or a jar of air as a pet? At least it would be a "pet"
Now think of creatures made of thin air and operate on 1165 dimensions and my limited human brain can't handle that. I just can't continue.
Anyway this theory will claim that there are **No** requirements for life and it just happens with enough time.
**On the other hand you can introduce a god or creator or old aliens or something which can mean a lot.**
First maybe they did create the universe the way it is or set it up so that particular life forms can exist. Why? Who the heck knows. Earlier point about the minds of absolute alien things.
Here Lovecraft is not a bad influence. I mean on how alien they are and how utterly we are nothing compared to those old things.
Anyway creator can make it so that the universe was created in such a way as to accommodate the little ones, us and the other species, but here is a question:
Why this way and not that? Why does the sun in our world appears yellow?
I think there is a degree of absolute arbitrariness in their.
It just is.
Even with religions but lets not make it about that.
Anyway your point about older stars seems kind of not that much as like we said either creator creates species which can live under those stars, old or new, or that life evolved to live under those starts. Same end result really.
Like how the Turians got their biology or how the Quarians got their immune system messed up.
Just growing from the soil of the planet, metaphorically, and those who could survive did.
1 factor we have to consider is energy. I really don't think a universe without any energy, suns obviously but could be anything, can be comprehensible to us.
I am no astrophysicist though. So maybe you can have a cold dead universe. But I would love to hear on what you think life will be like in that place.
And lastly we only got like 1 planet with life on it. I mean it seems absurd to judge the entire biological world to a mere planet but also we can judge the entire universe to some of our knowledge. Otherwise there is no thinking.
**So the take away from this is how much can we say for certain that A is right?**
Big does not mean no laws and also does not mean our laws. So yes I would say in the realm of biology it is possible to develop and grow and have life of all forms in almost all places. But the actual hard data is messing because you know.
Does this help? Not sure man. I am just saying no body went beyond the universe and got a list of hard requirement of life or knows about the exact start age to have what life forms under it.
So if I can advise you then just introduce some side effects of older stars in your world and have the story go as usual.
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My previous question asked if a stegosaur could become bipedal. I guess I should have asked if and how it could become humanoid-like. Asking if this is possible made me think about all the other vague humanoid shapes that have evolved over the course of Earth's evolution. Penguins, ground sloths, therizinosaurs, and of course humans. What were the driving forces behind all of these forms? What kind of world changes could pressure life forms to be this way?
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If you use natural selection as your primary thesis for change, then you have to articulate how bipedal movement gives the species a clear survival advantage over alternatives, which includes describing how four legs is a clear disadvantage.
A species won't just rear up on its hind legs because it's convenient for them. Ostensibly, there would have to be millions of specific dominant genetic mutations over time that ultimately result in shifting the center of gravity, spinal adjustments, changes in size and mass, reconfiguring the pelvis to accommodate the extra burden and a wider range of lateral movement, adjustments in the feet to provide more balance and stability, and if you don't want the forelimbs to be vestigial, adjustments to the shoulder, elbow, and wrist are also necessary.
All of these things are required to take something like a stegosaurus and turn it into a biped, and all of them have to happen independently of each other, only because the odds of simultaneous non-destructive mutations that both create a clear survival advantage and function in synergy with each other are ludicrously remote.
I'm not trying to argue against the idea as much as dissuade you from trying to come up with explanations for everything because nitpickers are ALWAYS going to find holes in something as complex as this. If you want to write about bipedal stegosaurs, just do it and only provide hints at the process that got them there.
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**The humanoid shape is merely a function of specialization of the bipedal shape.**
Once you already have the bipedal shape, the function of evolution is to specialize components that are already there to become better, rather than create new function, as least from a general standpoint. That is, if a quadruped requires the ability to manipulate objects, it's not going to develop new limbs to do so, rather, it'll adapt a set of limbs it currently has and the advantage lies in developing sets of limbs for specific tasks. One pair of limbs, the one close to the head, become specialized for manipulation (whatever is the case - claws to attack, for instance, or wings to first glide and then fly) and the other set becomes specialized for running. The ultimate end (or, at least, the current ultimate end) to this dichotomy of specialization can be said to be found in the upright human form - one pair of limbs exclusively on the ground for motion and the other pair exclusively for object manipulation.
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Well, one reason bipedalism is useful, is it requires less energy per step. [Studies on energy efficiency in bipedalism](https://www.sciencedaily.com/releases/2007/07/070716191140.htm#:%7E:text=A%20new%20study%20provides%20support,walked%20on%20four%20legs%20did.) A stage in between being on four legs and being on two, would be being able to run on two legs for short sprints, like bearded dragons can. [Bearded Dragon Running](https://www.youtube.com/watch?v=cvSQEBlaoCg) This adaptation could be needed for getting away from predators quickly, or to surprise and catch prey for the larger animals. A video I think would be very helpful [Ancient crocs](https://www.youtube.com/watch?v=QmdcewIjXi0) An ancient crocodilian species that evolved the ability to run on two legs in what could be a precursor to your bipedal reptilians. It evolved this ability due to competition from other predators in the area, so that could be a main reason for your creatures evolution.
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In my story a consortium of megacorporations spot a new comet 26km wide entering the inner solar system. Earth is in dire need of water because of an already worsening climate change disaster (think now + a hundred years of out of control capitalist greed). Especially the climate change disaster's effect on temperature, capitalist greed against inland aquifers and increasing salinity in coastal aquafers because of sea rise.
In countless places near Earth they are mining for water: the Moon and several near Earth asteroids. But this thing is huge, and timely, and in their greed, these megacorps think they can score a big win.
They try to bring the comet into orbit around the Moon with gravity tractors. In several years time they manage this, but the tractors didn't just bring a ball of ice, but a dirty ball of rock and ice - a rubble pile with thirty or so core rocks ranging from a few hundred meters across to a kilometer across. The gravity of the Earth and Moon finish pulling the thing apart and fourteen of the largest chunks of rock hit the Earth.
Given Earth is kind of a water world, most hit in the oceans, and throw hundreds of gigatons of water vapor into the air. The ones that hit land do the nastiest damage and a couple hit aquifers throwing not just ash and earth into the air, but also gigatons more water.
The mass of the atmosphere is around 5.3x10^15 gigatons, or 530 million gigatons, according to various [sources](https://hypertextbook.com/facts/1999/LouiseLiu.shtml).
The average amount of water in the atmosphere is 0.001% of all the water on Earth, or 1,386,000 cubic km, from the facts listed on the USGS's page on [the water cycle](https://www.usgs.gov/special-topic/water-science-school/science/atmosphere-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects). [Wiki](https://en.wikipedia.org/wiki/Cubic_metre) has a cubic meter of water as about a metric ton. So a cubic kilometer of water would be a gigaton. Given the previous facts, Earth's atmosphere should have about a 1.386 million gigatons of water in it.
I know greenhouse gas-wise, water vapor in the air is [complicated](https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/its-water-vapor-not-the-co2.html). But because of all the dirt and ash in the air, first they'd have to go thru a prolonged [nuclear/volcanic winter](https://en.wikipedia.org/wiki/Impact_winter). After that, during that and for a long time after I expect it will rain like crazy. So the question is how long will it take for all those gigatons of ash and water vapor to come out of the atmosphere? The amount thrown up would only be few millionths of the total water in the atmosphere, but I would have to guess the suddenness of it would have some kind of a short term and long term effect.
Another complicating factor, and one I couldn't find any reference for is if a 1km size impactor would hit hard enough to cause any [mantel plume](https://en.wikipedia.org/wiki/Mantle_plume). Various references say various things about how wide and deep a land crater will be for something that size.
Yet a third complicating factor - much of the rubble pile would still be big enough to cause significant air bursts and ground impacts, throwing up even more water and ash.
**So given all that context - how long will the ash take to settle out? And how much longer will all that water vapor take to rain back down?**
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I appreciate that you are building a world with such problems in mind, both the physics/logistic one and the humanitarian one. However, I think bringing more water from space is not the solution. Allow me to do a frame challenge.
Your comet will have 9.2 × 1018 kg. That's about [1% of the mass of the ice on the South Pole](https://en.wikipedia.org/wiki/Antarctic_ice_sheet). You would elevate the oceans by the same amount we would if we just melted 1% of the Antarctic at once.
Consider that [the total mass of the oceans is around The Earth's oceans have about 1.4 × 1021 kg](https://en.wikipedia.org/wiki/Ocean), which is three orders of magnitude more than the comet. Your comet will flood coastal aquifers even more while causing no perceptible decrease in salinity. You'll just be putting mangroves underwater, where they will rot and release greenhouse gases.
Proper management of the water we already have here is the path to saving ecosystems. Merely shoving more water into it just makes things worse.
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Kinetic Energy = (1/2)MV²
Where:
M is the mass of the asteroid just before it strikes the earth
V is the velocity of the asteroid just before it strikes the earth
For example, consider an asteroid that is one kilometre in diameter and weighs 1.4 billion tonnes (M = 1.4×10^12 kilograms), and is traveling at 20 kilometres per second (V = 20,000 m/s). The kinetic energy would be equal to (1/2)×1.4×10^12×(20,000)² = 2.8×10^20 Joules.
14 hit earth (1 in land 13 in sea)
so it 13 x 2.8×10^20 = 3.64 x 10^21 Joules
or 3.64 x 10^19 KiloJoules
ΔQ=cmΔt
specific heat capacity of water(which equals 4.187*10^3 J/(kg*℃))
Average sea temperature is 30°C
It is given by the equation
Q=mL
Q= energy input
m=mass of the matter to vaporize
L=the specific latent heat
According to Wikipedia the value of the latent heat of vaporization of water is:
L=2264.705 kj/kg
3.64 x 10^19 = (2264.705 x M) + (M x 4187 x (100-30))
3.64 x 10^19 = (2,264.705 x M) + (M x 4,187 x (100-30))
3.64 x 10^19 = 295,354.705 M
M = 123,241,646,006,621 Kilogram of water
M = 123 Gigatons of water will be convert up into the atmosphere
1 mile² thunderstorm cloud = 72,000 tons
15 mile² thunderstorm cloud = 1,080,000 tons
15 mile² thunderstorm cloud last 30 mins
so our 123 Gigatons will continue to form into 123 millions of 15 mile² thunderstorm cloud
above initial impact point and spreading around
which take 30 mins to empty their bucket back down to earth
(123,000,000 x 30 )/( 60 x 24 x 365 ) =7020 years
but that is single one at a time which is not how reality work
,the thunderstorm would formed and spread faster
earth surface area is 510,100,000 km² or 196,950,711 mile²
13 million of 15 mile² thunderstorm cloud can fit in that
so.. if the asteroid hit and spread evenly (13 of 1 km diameter asteroid hit around the earth)
it will be downpour for (123 x 10^6 / 13 x 10^6) x 30 mins
**5 hours..**
but if compact into certain area say
your capitalism corp pull it down to sea nearby USA (easy for them to go catch those rain
by predicted that the wind will bring those thunderstorm cloud into land)and the said 13
asteroids spreading impact zone about the same size as USA outside the shore (with 1 miscalculated landing on New york instead)
9.834 million km² or 3.8 million mile²
200,000 of 15 mile² thunderstorm cloud can fit in that
it will be 123,000,000 / 200,000 x 30 mins
**so vaguely about 13-20 days**
so if you want a good period of time for your story conflict like "capitalism corp covering up their mess" need about 3-4 month or so then just triple asteroid mass
(or the impact zone must be more compact / or throw in more meteor or increased it mass)
but if you want something like a year of raining oh well you'll need quite bigger asteroids to do the job
(btw the dust from only 1 asteroid hitting land would dispersed faster giving it'll be raining a lot so those dust probably last around 30% of the time period)
**Source**
15 mile² thunderstorm cloud > <https://wxguys.ssec.wisc.edu/2011/09/12/how-much-condensed-liquid-water-is-in-a-cubic-mile-of-fog/>
asteroid energy > <https://www.real-world-physics-problems.com/asteroid-impact.html>
Sea temperature > <https://www.seatemperature.org/>
calculate water to stream > [https://socratic.org/questions/calculate-the-amount-of-heat-required-to-convert-45-0-g-of-water-at-43-0-c-to-st#:~:text=Explanation%3A,the%20water%20to%20100%20degrees.&text=c%3D4187%20Joules%20per%20kilogram,specific%20heat%20capacity%20of%20water](https://socratic.org/questions/calculate-the-amount-of-heat-required-to-convert-45-0-g-of-water-at-43-0-c-to-st#:%7E:text=Explanation%3A,the%20water%20to%20100%20degrees.&text=c%3D4187%20Joules%20per%20kilogram,specific%20heat%20capacity%20of%20water).
how long thunder storm last >https://www.google.com/search?newwindow=1&rlz=1C1OKWM\_enTH866TH867&hl=en&biw=899&bih=923&sxsrf=ALeKk00Q2Jx2nBOHGsRrabrk60l9YppPQA%3A1594779746751&ei=YmgOX8C0LYfn9QOrq5KgAQ&q=how+long+thunderstorm+last&oq=how+long+thunderstr&gs\_lcp=CgZwc3ktYWIQAxgAMgYIABAWEB4yBggAEBYQHjIICAAQFhAKEB4yBggAEBYQHjIGCAAQFhAeMggIABAWEAoQHjIICAAQFhAKEB4yBggAEBYQHjoECCMQJzoFCAAQkQI6BAgAEEM6CAgAELEDEIMBOgsILhCxAxDHARCjAjoCCC46BQguEJECOgUILhCxAzoCCABQi-0CWNmWA2CZnQNoAnAAeACAAXCIAdIMkgEEMjAuMZgBAKABAaoBB2d3cy13aXo&sclient=psy-ab
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The Jovian moon Io is geologically active like Earth, yet it experiences heat pipe tectonics instead of plate tectonics.
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> Heat-pipe tectonics is a cooling mode of terrestrial planets in which the main heat transport mechanism on the planet is volcanism through the outer hard shell, also called the lithosphere. Heat-pipe tectonics initiates when volcanism becomes the dominant surface heat transfer process. Melted rocks and other more volatile planetary materials are transferred from the mantle to the surface via localized vents. Melts cool down and solidify forming layers of cool volcanic materials. Newly erupted materials deposit on top of and bury older layers. The accumulation of volcanic layers on the shell and the corresponding evacuation of materials at depth causes the downward transfer of superficial materials such that the shell materials continuously descend toward the planet's interior. - [From Wikipedia](https://en.wikipedia.org/wiki/Heat-pipe_tectonics)
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[](https://i.stack.imgur.com/kqZav.png)](https://i.stack.imgur.com/kqZav.png)
Imagine an earthlike planet with a mass of about 1.5 earth-masses, that experiences similar heating and tectonics to Io. **What would the crust be made of? Basalt, Andesite or a mixture?**
Going by Io as an example, one would expect basalt. Basalt is what Earth's oceanic crust is made of and flood vulcanism, which will most likely create a lot of the surface of this world, creates basalt as well.
On the other hand andesites are created if volatile-rich material sinks into the mantle and returns through vulcanism. On earth andesite is created near subduction zones and accumulates there over the eons. However on this world, subduction would happen everywhere and so andesite might form everywhere.
Some might wonder why this is relevant to my worldbuilding, however this will determine how the world will look at large.
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> Low-silica magmas are typically formed by partial melting of mantle rocks beneath mid-ccean ridges or at “hot spots” like Hawaii. These magmas erupt as basalts or intrude as gabbro, and are far less viscous. Eruptions are generally effusive. - [From the Geological Society](https://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3655.html)
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So basaltic magma would mean that the world would have a shallow profile and would look a lot like Io and andesitic would mean that the world's profile would be sharper, as the more viscous lava can build larger mountains. If a mixture of say, regular andesitic vulcanism and periodic basaltic flood vulcanism is the most plausabile answer, that would be interesting as well.
**So how will the geology of this world look like? Andesite or basalt? Or can I do whatever I deem plausable since noone can prove me wrong?**
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I'm basing this answer on the paper [*Heat-pipe planets*](https://www.sciencedirect.com/science/article/abs/pii/S0012821X17303242) by Moore, Simon, and Webb (2017, paywalled). The arguments of the paper are speculative, but I think the ideas they base their arguments on answer your question. I recommend reading through this paper if you have or can get access. It seems that the most likely answer to your main question is:
# Basalt
Moore et. al. argue that heat-pipe volcanism may be a phase which is common to terrestrial (rocky) planets during their early formation. They make this argument based on the presence of certain observed common features of solar terrestrial planets. One of these is the presence of a crust composed largely of mafic or ultra-mafic rock (that is, basalts and similar rocks). To quote the paper:
>
> Heat-pipe operation leads to: 1) Thick, cold, and strong lithospheres even though heat flow is high, 2) Dominance of compressive stresses as buried layers are forced to smaller radii, 3) Continuous replacement of lithospheric material, 4) **High melt-fraction (mafic to ultra-mafic), low-viscosity eruptions and efficient degassing of the interior**, and 5) A rapid transition to stagnant-lid or plate tectonic behavior.
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(Emphasis mine)
So, due to the efficient degassing of the interior, volatile-assisted remelting is unlikely, and Al and Si enriched rocks are less likely to form. Based on my reading of this paper I would expect a planet with a fairly smooth surface composed of mainly basaltic rocks. The main geographic features you might see would likely be compressive (e.g. faults and folds).
Note, though, that basalt may not be guaranteed. The authors propose a geological history for the Moon which includes a heat-pipe phase, during which the presence of volatiles in the interior of the Moon allows for buoyant plagioclase rock to rise toward the surface before being mixed into the lithosphere. Their proposed mechanism goes a bit over my head, but to me it seems that if you want that Si and Al rich crust, heat-pipe convection needs to *stop* relatively soon, or the plagioclase rock would be replaced with mafic rock over time. This might be what happened to form the lunar mare (which are basaltic).
Finally, one other thing which might be interesting to you: the authors mention in the conclusion that external heating (as in the case of Io) is not the only way to get a planet which stays in the heat-pipe volcanism phase in the long term. Here's the relevant bit:
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> Since the equillibrium heat flux of a planet scales as mass/area (for most plausible heat sources), terrestrial planets more massive than the Earth should experience longer heat-pipe episodes prior to the initiation of plate tectonics ... For the large "super-Earths" over five Earth masses, the lifetime of the heat-pipe phase may exceed the lifetime of Sun-like parent stars and thus any subsequent plate-tectonic phase may bever be observed. Such planets might better be called "super-Ios" ...
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[Answer]
**Andesite, because in a planet with life subduction will not happen everywhere.**
You have a system like Io. But you want life, so you need refuges that are not covered with lava every few years. You can confine your vulcanism to long term permanent pipes and lava pools, like Loki Patera.
>
> As Io orbits Jupiter, gravitational tides yank at its interior,
> depositing massive amounts of energy that must then rise to the
> surface. But the moon has no tectonic plates that allow magma to
> easily slip through. Instead, the magma rises through pipes, not
> unlike the volcanism that built Hawaii. Across Io’s surface, periodic
> eruptions flare up and then die down. But elsewhere – most notably at
> Loki – the channel seems to stay open continuously...
>
>
>
<https://www.newscientist.com/article/2113305-window-to-hell-ios-strongest-volcano-changes-face-as-we-watch/>
There is a constant turnover of magma rising up, cooling and sinking back down at the giant lava pool that is Loki Patera. And it makes sense - if there is constant heat and constant pressure and an open channel to relieve it, that channel will stay open.
In your life-hospitable world, these active vents might be the relics of globe-spanning cracks, themselves the relics of a time when the surface was cooling from uniformly molten. As on Earth during that molten time lighter minerals floated to the top and as on Earth those areas became crust. Heavier basalts are confined to the regions around the active vents, and they will probably fall in soon.
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In my setting, I'm trying to develop interesting movement/combat mechanics. I asked a related question about ways of slowing free-fall descents in an effort to develop exoskeleton-enhanced parkour. There were numerous problems with that, and even the methods that made sense meant losing the "spirit" of the movement dynamics I was looking for. Among the *many* interesting and thought ideas posted -- and *still* being posted -- there, one that stuck with me was that of "super pogo-sticks."
This got me thinking about some other crazy stuff leaning more towards science-fantasy than straight science fiction. That said, I do want to understand some of the possible physics involved here to make my idea work. Yes, there's *serious* amounts of handwavium being applied here. That aid, I do want to focus on the **mechanics involved of creating a pushing device like the one below.**
Below I have the idea, followed by some supporting images, and then the problem I'm facing. It's some scrolling.
**The Idea**
Handheld "Booster-Blades" (I haven't come up with a better name yet) capable of creating a handwavium empowered "energy field" that can that serve three functions:
1. Creating a wide, rounded shield that blocks particles and waves. So no bullets, no lasers. It's just a really tough shield.
2. The shield's seconndary function is that it can be "pushed" with great force, allowing the wielder to spring off of hard surfaces.
3. The Booster-Blade also allows a sharp, pointed "Power-Lance" or perhaps "Power-Hook" designed to stab bad guys, by getting around *their* shield. Or perhaps also "hook" onto things.
[](https://i.stack.imgur.com/UXugT.jpg)
[](https://i.stack.imgur.com/wXifi.jpg)
[](https://i.stack.imgur.com/uB8GT.jpg)
[](https://i.stack.imgur.com/D6rl5.jpg)
In this setting, the shields have negated much of the utility provided by ranged ballistic and directed energy weapons. Thus, people have opted towards *becoming* the projectiles themselves. Just bear with me. I'm not trying to figure out how much sense *that* makes (just yet). Thus, using shield-pushing and the lance, people basically use "sword and shield" fights but as human pinballs, where much of the skill comes from your talent for creating interesting and unexpected angles.
**The Problem**
I like the video-game esque movement and combat mechanics at play, but I'm worried about how they decelerate their falls. I'll handwave HOW the shield is tangible, but not how basic physics works. If you catch my drift.
When I first came up with it, I thought the grips on the booster-blades might be pressure sensitive, allowing them to "slowly extend" the shield as they gripped harder or bring it back as they loosened up -- allowing them to cushion their falls to a stop or sort of "pogo" back up.
In my head, it would be like clap pushups -- you don't land rigid, or you snap your shoulder; you slowly decelerate before popping back up.
If the shield's extension and contraction is controlled by how hard you grip the handle, or perhaps by turning an exoskeleton-attached throttle like that of a motorcycle, would it be possible to use such a pushing-device to cushion your falls?
I like the idea of shield-pushing. I know there's lots of handwavium being applied to the shield itself, but, if you grant me that, how could it be used to decelerate and permit the sort of vector-based combat I'm looking for? Does the throttle/grip solution make sense?
If the force behind the shield was like that of a "spring" it might make sense, right? If it could contract, storing up potential energy for subsequent release, would that interfere with other functions like being able to "bash" with the shield or use to stop projectiles?
What are my options?
Thank you all.
[Answer]
In school physics classes, a spring is just a spring, and you learn by hanging weights and measuring deflection how to find the *constant* spring modulus $k$, up to the point where you exceed the elastic limit and your spring deforms into a messy wire. The real world, as with most things, is nowhere near that simple, and engineers can create a bewildering variety of springs with *varying* behaviours over their elastic range (ie $k$ varies over the range $x-x\_0$, over time, or both). The conical springs in old mattresses are a good example of this: they are intended to have a steadily increasing $k$ value with increasing force/deflection, meaning that light people sink into the mattress a bit, and heavier people sink in more, but not *proportionally* more, so the mattress can accommodate a wider range of body weights while still providing 'some squashiness' to everybody. Equally car suspension springs try to have the awkward property (through varying the coil pitch and sometimes the radius) of always offering a good range of 'quick response' deflection (ie allowing rapid deflection in response to the sudden force of hitting a pothole) while still accommodating as wide a range of *overall* forces (ie how heavily you've loaded your car) with as little deflection as possible.
What this means is that if you set your phlebotinum generator up to produce a shield which is 'elastically' connected to the handle, you only need to handwave in the power to *dynamically adjust* the modulus of elasticity $k$ as well as the zero-load-extension $x\_0$, to permit a bewildering variety of behaviours for it. If you make $k$ very high you create an extremely rigid shield good for bashing things. If you start with $k$ quite low ('soft') and $x\_0$ quite large and absorb a fall or blow by allowing the shield to deflect away from its basepoint, then quickly ramp up $k$ to a stiffer value, the device will exert a powerful force to push the shield back to its basepoint, springing you up.
Proper management of these two controls will be difficult for a human to grasp, especially since $k$ is not very intuitive to our savanna-brain subconscious, which would justify any training regimen or beginner incompetence you want to write in. The potential energy stored in a spring is $E\_{spring}=\frac{1}{2}k(x-x\_0)^2$, so over-egging the controls could easily exceed the handwavium generator's capacity to absorb or supply the difference in energy, with whatever results you deem appropriate.
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I'm designing a creature which possesses a decently unusual trait: despite having a developed head, it's mouthparts are attached to a tentacle that retracts into the creature's belly when not in use, similar to a [flatworm](https://brianmccauley.net/bio-6a/bio-6a-lab/flatworms), but with a more elaborate structure and complex mouthparts at the end of it. Based on this, Could a creature evolve to have a mouth separated from it's head?
[](https://i.stack.imgur.com/BO7Qs.png)
[Answer]
**If you have a body plan without a head, you can put the digestive apparatus where it makes the most sense.**
[](https://i.stack.imgur.com/3Tzak.jpg)
[source](https://www.publicdomainpictures.net/en/view-image.php?image=315267&picture=starfish-feeding)
A problem is how "head" is defined for us - we think of heads like the familiar tetrapods have. A system with a feeding orifice separate from the "head" makes more sense as you get farther away from a body plan with a conventional head. We are used to having a lot of important stuff all piled into the head but there are successful body plans from different phyla that do it differently. Starfish have sensory organs on the tentacles and a more distributed means of locomotion (tiny feet), so it does not seem so unusual that their central "pharynx" (really an evertable stomach) is in another different place.
Moving digestion away from sensation, locomotion etc makes sense. But I struggle to think of a system where the digestive apparatus is decentralized - for example entirely in one (or more) appendages. Probably because digestion is so central to a creature that lives this way, and also resource intensive to maintain.
[Answer]
Yes. For similar reasons as Turtles have their necks the way they have it. The reason why they woud evolve it like that will probably be protection of the pharynx.
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I am trying to create a game, where you take role of CEO of huge company in future interstellar society. All basic needs of humans like food, accomodation, trasport, healthcare, education are satisfied by default. But there are various luxury goods that not every human can afford for example some gastronomic specialities, private cars, mansions etc. You as a CEO can produce this kind of goods and try to sell them to citizens of the planet. This spending of money will happen on 'ingame monthly' intervals as well as payments and is calculated for whole planet entirely.
For example this month all companies will pay their employees 1 billion dollars combined, so next month there will be 1 billion dollar to be spent on luxury goods. For better clarity every kind of luxury goods is evaluated as 'how much luxury' they present. For example a superburger would be worth 1 point of luxury because it is just food and car would be worth 1000 points. There would of course be many other kinds of luxury goods but to make the question simple, lets just have cars and burgers for now.
SETUP
Now let's imagine planet A with company A-burger-1 that produces 10 million superburgers per month and sells them for 9\$ each. Then company A-burger-2 which produces 10 million of them and sells them for 11\$ each. There is also a factory company that produces 50 000 cars per month, A-car-1 and sells them for 10 000\$ each and company A-car-2 that produces another 50 000 cars per month for 15 000\$ each. Lets put this into table and count the luxury points in:
A-burger-1: offering goods for total 90 000 000\$. asking for 0.9\$ per luxury point.
A-burger-2: 110 000 000\$. asking for 1.1\$ per luxury point.
A-car-1: 500 000 000\$. asking for 1\$ per luxury point.
A-car-1: 750 000 000\$. asking for 1.5\$ per luxury point.
Now lets say that citizens of planet A have 1 billion dollars to spend this month on luxury goods and of course they want to use them as efficiently as possible. This would mean, that they firstly buy out all the superburgers of company A-burger-1, then buy out all cars of A-car-1, then all burgers of A-burger-2, but company A-car-2 will sell less than a half of their goods. If next month people had 2 billion to spent, A-car2 would be able to sell all of their goods, but if people had just 500 000 000 to spend next month, not even A-burger-2 would be able to sell anything at all.
PROBLEM
Different planets have different condition and on most, certain kinds of businesses are doing better than others. For example planet A would be have good conditions of growing food and therefore A-burger-n companies would be able to sell their burgers for just 5\$ making it for all car companies impossible to compete. Similarly planet B can be rich for metals so all B-car-n companies would prevail. Now this obviously makes no sense, since as a human you would get tired of buying superburgers all the time and never a car. On the planet A where burgers are super cheap, people would be willing to pay much more for a car than people of planet B.
SOLUTION I AM LOOKING FOR
I could imagine some kind of general algorithm, that would adjust luxury point of different goods on different planets. That it would not be strictly given that car is worth 1000 luxury point in the entire galaxy, but instead differs across each planet. But how would algorithm like this work? Should it take all recently spent money vs types of goods and calculate some ratio. It is also possible to take actual number of citizens into calculations. Like everyone wants a car, but dont need other car in next few years. But some people have more cars. At this point I really dont know.
DISTANCES OF TRADE
Of course it is possible for any company from planet B to sell their goods on planet A, but interstellar travel is very expensive, so they would have to think about it twice. On the other hand, travel within a planet is free.
Thanks a lot!
[Answer]
You could see the different takes in the space sims.
Do recommend watching the video from Sseth for Starsector. A humoristic view that shows what lawless places can create.[Sset review for Starsector](https://www.youtube.com/watch?v=acqpulP1hLo)
Now on something far older and richly decorated with heaps of lore: Mechwarrior franchise, or Battletech world, its the same.
There, politics create scarcity where, by all rights, there should be abundance.
So you will continue eating burgers because its the only NOn sactioned foodstuff available. If you dare to think to eat an apple, your cargo will be taken for illegal goods (starsector).
Or everyone forgot how to grow up apples (Battletch).
Or the owners of the Apple market want to maintain the hold on it and if you meddle with them, they will liberate your entire way of life (Tachyon the Fringe).
So first try to list all the possible factors:
* politics (Mount and Blade got a system of Truce/amnesty/Non aggression/ for x days as spontaneous events)
* military power
* space pirates
* Travel Hazards (cant make the trip from A to B, there is a black hole, remnant of alien technology, base of undesirables, gotta go to C first and they ask for Taxes)
* Add that some goods are perishable.
With all of them, you can then make an excel sheet and create 2 worlds. Assign different multipliers to each resource, see how the impact of Piracy can affect both.
When Planet A (Pa) got cheap food and piracy makes it reasonably priced, its ok.
Now Planet B (Pb) got reasonably priced food that with Piracy got Expensive. That means less growth as few people can afford it.
As you can see, Piracy can have a different impact beyond the obvious.
List all the factors you want the game to have.
Diagram possible interactions and make a few examples. That would help you to see if it is too complex to be enjoyable and you want to hit the sweet spot of Realistic vs Enjoyable.
Don't make me purchase an Ingame Tax Consultant. I beg of you.
[Answer]
### Planetary vs Interstellar
What you described were planetary economics. If interstellar travel is too expensive, there will be no interstellar economics, except for some very rare goods (animals of a certain planet? Plants you can't raise elsewhere?) So the first problem are the goods to be sold on interstellar routes.
### Taxes
Second is taxes. You have 1 Billion salaries, with pension insurance, health insurance and taxes in the end you will have 500 Million free for luxury goods. This is a huge brake for everything. It encourages criminality, too. Who wants to pay taxes?
### Saturation
Third is saturation. You could possibly buy 1000 luxury burgers for 1 car, but after you ate one of them you don't want anymore until next day. So you will buy a maximum of 365 luxury burgers, if you really are a fan. Normal people with a functioning brain will rather buy between 10 and 20 per year, except if they don't mind becoming obese very quick. Assuming that normal people mind, there is a natural maximum. Same for the luxury cars. There might be people who buy one per week, normal people rather buy one in ten or 20 years. You could implement that as hard maximum, having just a tenth of a car per year. Or you can make a declining return function, giving you 1 luxury for the first ten burgers per year, 0.9 luxury for the next ten burgers per year, 0.85 luxury for the next ten burges per year... and so on. Go for a natural decline e function if you must. The advantage of a natural decline function over a hard maximum is that your players can sell more if they become cheaper in production, the disadvantage is a lot more calculation time needed on your server. A median way may be to have some ten or twenty steps, saving calculation time.
### Smugglers
Fourth is smuggling. Why is interstellar travel expensive? Is it taxes? Higher taxes can mean more criminality and cheaper prices on some goods, when they are smuggled instead imported. The key is low volume, high price. It will not be easy to find a smuggled car, a smuggled animal or plant is more realistic.
### Travel time
Risky routes can yield short travel times, safe routes can yield long travel times. What if the luxury car from B is worth a fortune on A in the billionaire class, but only if it arrives before it is out of fashion? A Billionaire might think a car is out of fashion as soon as normal people can afford it? So the Billionaire might pay for someone to take the risky route, while normal people have to wait half a year longer while the normal dealers take the long way around the black hole. You could implement it by having 2 or 3 years travel time, via the risky racing route only 1 year or instant sale but ten times the price? The first car sold on a planet may yield 10 000 000 luxury, the 10th car may yield the normal luxury, the 10 000 000 car sold may yield only half the luxury. It may force your players to develop new models.
[Answer]
The planet should have four prices at which it will buy items.
1. The bare limits. This will be a much higher price- maybe ten times the base- at which people will buy the item. The super elite and mega rich will always want a certain amount of luxury food, and even at a much higher price, they will buy this much. Say, 100 luxury cars per month at 10,000 luxury points.
2. Status symbol. The rich and middle classes aspiring for luxury will pay for a number at this price. Say, 10,000 at 3000 luxury points.
3. The base price. This is the price that people will pay if it's reasonably available for all middle class people. 50000 at 1000 luxury points.
4. The surplus price. This is the price people will buy if it's really cheap and they're working class. 200,000 at 500 luxury points. Below this point, the luxury points are better spent on raw materials.
This lets you say what people will buy at what price. If the cars are really expensive (3000 luxury points) people will buy 10k max. If they're dirt cheap, at 900, and 60k are available, people will buy 50k at 1000, and 10k at 900, because competition for the cars will drive up the price of 50k to 1000.
You can have a fixed ratio of luxury good demands for each population group (mega rich, elite, middle class, and working class) which can be increased or decreased by various factors, like happiness, war weariness. Exactly where the negotiated price ends up for any surplus produced could be tweaked by welfare and social policies.
[Answer]
## Some Basic Microeconomics
You are asking for nothing more than a marketplace simulation - and a simple one at that. There are lots of way to do this, but let me give you one of the more straightforward examples.
For each product, you create a Demand formula which expresses the Quantity Demanded as a function of the Price. The formula must have at least two parameters which we shall call Base Demand and Elasticity. Obviously, the higher the price the lower the quantity desired, so your formula should always have a negative slope. (You can use a linear formula, such as Quantity = 1000 - 5 \* Price, but this can lead to results with negative quantities. More sophisticated equations will lead to better results, but there is no "right" formula. If there was, economic models would actually be useful in the real world.)
Next, for each producer you make a similar formula, the Supply curve, this time with a positive slope. This formula must also have at least two parameters, which correspond (inexactly) to Fixed Costs and Marginal Costs. Note that you have one Demand curve for every product, but multiple Supply curves since you have multiple producers. With the Supply curve you can use a linear formula, this time without worrying about getting negative numbers.
The next step is simple: try different prices until the sum of the Supply functions equals the Demand function for each particular product - burgers, cars, etc... You will then know the price and total output of every product (and the output of each producer, as well).
But there's one problem. Your model is static and will sometimes lead to outrageous results. In real life, we call outrageous results "opportunities"! That is, if it's really expensive to build cars on this planet, inventors and entrepreneurs will find better ways to make cars. The next generation of cars will be cheaper.
To reflect this, every time-unit you will want to adjust the parameters in the Supply curves by a small amount in proportion to the slope (Elasticity) of the Demand curve at the current price, with a random factor thrown in as well. This represents the investment made to improve production. You then run the price-finding routine again to determine the results.
This much should be enough to power a simple game. As the game gets more complex you can tinker with other economic concepts such as goods substitutions (e.g. when burgers are expensive, people buy more hot dogs), interplanetary currency exchange rates, and such. Much will depend on the specific formulas you use for demand and for the "investments", and you will certainly have to experiment to get the feel that you want.
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In a story that I am writing, there is a specific race that has the ability to increase the density and strength of their muscles without the size of these muscles changing, through the consumption of monster meat. This race also has a focus on strengthening the legs over any other body part, so the legs are even heavier than the the torso and arms put together.
Without putting in much effort and eating a balanced diet with occasional monster meat included, a child could weigh the same as four average human males, 360kg, a female teenager of this race could weigh the same as an African Bush Elephant, 6,000 kg. A decade later, she could weigh the same as an M1 Abrams main battle tank, 54,000 kg. They look like any ordinary human, yet weigh dozens of times more.
This has obvious implications when it comes to the pressure this race would exert onto the ground of a planet. They would pretty much sink through any type of soft ground. No matter if it is metal or stone, the flooring in buildings would suffer. Once they start walking, the ground pressure exerted would double. As a drawback to having great strength, they cannot leave their home planet, which has conditions suited to them.
An individual from one of these races, my main character, acquires clothes with an enchantment that would mitigate effects of their incredible weight from effecting the ground. (Let's ignore the effects that super dense and strong arms would have on door handles and focus solely on the downward force, including the effect the enchantment would have on a chair.)
**My character would eventually reach the weight of 500,000 kg, 500 tons. Then 1000 tons, then 2000 tons, and so on. Not sure of the limit yet.**
Now, ignoring the fact that there are a whole multitude of other problems such as dense ear bones leading to them being hard of hearing as well as having an incredibly high body temperature as a result of more surface area for thermal transfer within the body itself, I would like to know what kind of enchantment would work in this situation and how it would work.
**How could a magical enchantment minimize the effect a super dense and super heavy object would have on a floor beneath it?**
***Here are some ideas that I personally came up with and what I think of them:***
***(The magical enchantment is placed on a piece of clothing, i.e. shoes.)***
-The magical enchantment increases the effective surface area of the feet without actually making the feet bigger, much like snowshoes do but through magical means.
*This may not be effective within a room. This may not be effective in small spaces. This enchantment may effect movement, such as the foot coming down at an angle may cause the increased surface area of the foot to hit the floor. May effect others standing close. It would not assist with furniture. This enchantment most likely begins to fail when my character approaches to 100 tons mark. **Does not seem practically viable.***
-The magical enchantment disperses the weight into the air.
*The air may perhaps feel heavier, it may make breathing difficult. Increases air pressure. The air that is compressed would be replaced by air particles that were originally outside of the sphere of influence, which would also be compressed. Seems incredibly deadly. Although, it would be pretty cool as a sort of aura/pressure ability, as if enemies could actually feel the individuals weight and power through the air becoming heavier. Although cool, still does not seem safe at all. Would also most likely fail in a vacuum situation, as well as when my character reaches even the 10 tons mark. **Does not seem physically or practically viable.***
-The force is completely cancelled out with no real explanation other than magic. Such as the force being shunt off into another dimension.
***Just seems boring.***
-The magical enchantment spreads the force exerted downwards equally into the surrounding flooring, regardless of uneven terrain. As my character reaches the 100 ton mark and beyond, it would most likely exert the force on the entire structure. beneath the characters feet. E.G. a space station.
*This may disregard furniture. When sitting down, a chair may be the only object counted, thus leading to the full force being equally spread onto the chair. This enchantment may spread the downwards force onto any screws or support structures within the flooring which are not supposed to have such a large amount of force hitting it specifically. **Seems the most practically viable, and the fact that the floor may still creek in protest as the individual walks may make for interesting situations. Furniture not being covered, as well as small vehicles, may also make for an interesting restriction within the story.***
**Any other magical enchantments with even a tiny bit of realism would be appreciated. The effects do not need to be completely cancelled out, just turned down to safe levels, e.g. not destroying the flooring as the character walks, perhaps only leaving behind a now slightly more structurally unsafe area due to the now weakened flooring.**
[Answer]
Your first idea seems ideal to me.
When something like your feet is resting on the ground that same ground resists the pressure. It takes effort to deform the ground, push it further down than it already is because beneath that ground is more ground, and beneath that is the earth mantle, and beneath that there is the partially molten core that is pressing just as hard outwards as all the layers on top are pressing inwards creating an equilibrium where neither moves. And whenever you shift your weight, the pressure becomes a tiny bit higher, everything below it becomes a little bit more compressed until that pressure is at an equilibrium again.
So what you do is simply say "my feet aren't just touching the ground where my physical feet are, they are also touching the ground in a large circle on a horizontal plane compared to the ground".
So if you step halfway up a hill, you will be supported by all the terrain that is at your height in the circumference that you can decide, allowing you to stay there without sagging into the ground as the entire surface area of the piece of hill can handle your weight. Problems would arise when climbing stairs though, although if the walls that support said stairs can support your weight than they will take it and keep you standing without collapsing the stairs.
You could also switch it around. Let's say that the magic works like piles driven into the ground to support houses, or in this case it supports your heavyweights. With every step it basically makes the ground beneath you one single block that is using the solid foundation below the ground to support your weight as well as the pressure from the sides on those piles that keep them in place.
[Answer]
Not sure if this is exactly what you want, but if it is possible for things to hover, a small circle of wood could be enchanted to hover in a similar manner to a hoverboard, and to have that piece of wood be enchanted so it is either unbreakable or extremely resistant to breaking. A different option would be to enchant the places where your character commonly goes with an enchantment that essentially strengthens it to the point of being mostly unbreakable. If this creature is widespread throughout the world, it may make sense to have that worlds authority figures somehow enchant the entire planet.
[Answer]
The enchantment actually warps gravity in his vicinity.
It warps the gravity in such a fashion that the majority of his mass has its gravity reversed alternating throughout his entire body. Not enough to rip him apart by tidal forces but enough that the real pressure he is exerting on the ground is a fraction of the total. Let's say only 300 lbs/ 500 tons. With the way the enchantment works, however is that it will need adjustment at regular intervals to account for weight gain from more monstie meats.
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I would suggest a sort of contained magically induced magnetic levitation that would allow the user to stay on the ground but not actually have many weight issues. This is done by many real life trains to lift them up from the ground and propel them forward.
The article of clothing this wizard received would most likely be made out of a sort of magical metal that would contain a sort of upwards magnetic force to push the user upwards just enough to reduce or eliminate the strain of the weight on the surrounding terrain. As far as making the terrain underneath the character able to reciprocate the magnetism, it would have to be a double enchantment that would create a magnetic field on surfaces directly underneath the article of clothing on the surface of the walking space.
Rules for which substances can be walked on with this are negotiable depending on how potent magic is. The enchantment might not be very efficient as far as magic consumption if there isn't a natural absorption feature, so look out for that. Essentially, it wouldn't be an easy change to get used to for the character to walk with padded weight and then there is the added balance that the character would have to develop. The horizontal movement would also be unaffected by the enchantment, but if the direction of the enchantment is changed even slightly, the wizard could fall.
It would give your wizard the ability to walk without giving the ability to directly fly. Then, the amount of weight that this enchantment reduces is completely up to you.
```
Hope my answer helps.
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[Question]
[
I'm not sure if this site or Astronomy would be better, but I figured I would try here instead. I am
attempting to create a [semi]plausible star system in Alpha Centauri for a series. The system was originally intended to have 1 habitable planet per star, but after my first couple of attempts I noticed that it might be possible to get at least 3 planets to be habitable. The latest attempt actually shows 5 potentially habitable planets (2 of which are a binary[That is another SE question]). Ultimately, I would like this to be the case as it allows a much more diverse universe for the series.
## Attempt:
* aCen A Planets
[](https://i.stack.imgur.com/Bqe3r.png)
* aCen B Planets
[](https://i.stack.imgur.com/oBJ3G.png)
I don't have access to, or knowledge how to use, any form of software like Universe Sandbox. I have read several reports on planet orbits and I think I did an "ok" job with this.
Here are some papers that I have looked at for this:
<http://adsabs.harvard.edu/full/1997AJ....113.1445W>
<https://arxiv.org/pdf/1801.06131>
<https://core.ac.uk/download/pdf/25201586.pdf>
My main concern is that the planets might orbit too closely. I have attempted to find a formula (that I could understand) that could aid in spacing the planets. The nearest I could manage is using the Mutual Hill Radii. There are conflicting reports where one says that 10 - 12 MHR (Delta-H) is good or a tightly packed system. Earth and Venus have around a 25 MHR value. One of the reports that I linked mentioned up to 25 MHR for aCenA, but it also shows several other numbers and after trying to comprehend everything my brain reached orbital velocity.
**Question: Is the planetary spacing stable enough to host planets on Gigayear timescales?**
They don't necessarily need to be able to have spawned life, but they should be able to support life with little to no human intervention.
Note and Bonus, aCen V is a binary planet that orbits with a Semi-Major axis of 750,589km with an eccentricity of 0.01204. *(There is an error in the image in Yellow that shows 148.623 and Eccentricity of 0.0910)*. The inclination should be 0 as both planets should be on the same plane.
Last note: The Semi-Major Axis distance is in Megameters (1 million meters).
[Answer]
I am also trying to figure out plausibility for planets in the Alpha Centauri system for a sci fi game design... I'll share some of my initial research.
One thing about the system is how binary stars interact. Centauri actually has 3 stars, but only A and B happen to come quite close to each other. This causes major disruptions to all the orbiting bodies except those closest to each star:
From <https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems>
"In non-circumbinary planets, if a planet's distance to its primary exceeds about one fifth of the closest approach of the other star, orbital stability is not guaranteed. Studies of Alpha Centauri, the nearest star system to the Sun, suggested that binaries need not be discounted in the search for habitable planets. Centauri A and B have an 11 au distance at closest approach (23 au mean), and both have stable habitable zones. A study of long-term orbital stability for simulated planets within the system shows that planets within approximately three au of either star may remain stable (i.e. the semi-major axis deviating by less than 5%). The habitable zone for Alpha Centauri A extends, conservatively estimated, from 1.37 to 1.76 au[2] and that of Alpha Centauri B from 0.77 to 1.14 au[2]—well within the stable region in both cases."
That's good news for the habitable planets, which I care most about for my game.
But you've got 8 planets for aCenA and 7 for B, and your outer planets would surely get knocked out of stable orbits about every 80 years:
From <https://en.wikipedia.org/wiki/Alpha_Centauri>
"Alpha Centauri A has 1.1 times the mass and 1.519 times the luminosity of the Sun, while Alpha Centauri B is smaller and cooler, at 0.907 times the Sun's mass and 0.445 times its luminosity.[16] The pair orbit around a common centre with an orbital period of 79.91 years.[17] Their elliptical orbit is eccentric, so that the distance between A and B varies from 35.6 AU (astronomical units), or about the distance between Pluto and the Sun, to 11.2 AU, or about the distance between Saturn and the Sun."
"Alpha Centauri C is about 13,000 AU away from Alpha Centauri AB." [wont disrupt A or B’s planets]
So your inner planets would be stable, but not the outer ones. Luckily the habitable ones should be stable! Although they may get bombarded by meteorites when the stars get close and things get mixed up a lot.
[Answer]
I don't know if what I have to say will help you or if you already know it.
I have the impression that the minimum stable spacing of planetary orbits depends on the masses of the star and the planets and the distances of the orbits..
If the mass of the star is changed, it may change the minimum stable spacing of the planets.
If the planets are less massive, they should be able to have closer stable orbits. For example, tiny asteroids can have orbits with semi major axes which are very close. Hundreds and thousands of asteroids can orbit in a region where only one planet could have a stable orbit.
You also have to consider the width of the circumstellar habitable zones around Alpha Centauri A and Alpha Centauri B.
There have been many attempts in the last 60 years to calculate inner or outer edges, or both, of the Sun's habitable zone. If we know the inner and outer edges, and width, of the Sun's habitable zone, we can multiply or divide it by another star's luminosity relative to the Sun to get the size of that star's habitable zone.
Here is a link to a table with various scientific estimates of the inner or outer edges, or both, of the Sun's habitable zone.
[https://en.wikipedia.org/wiki/Circumstellar\_habitable\_zone#Solar\_System\_estimates[1]](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates%5B1%5D)
Note how greatly some estimates and calculations vary from others.
The estimate by Dole in 1964 was for planets habitable for humans. I suspect that many other estimates in the list are for planets habitable by carbon based liquid water using life forms, and that some of the inner and outer limits in some estimates may require atmospheres that humans could not breath in to get liquid water temperatures. That is a factor which science fiction writers should research.
So obviously researching the various estimates and calculations and deciding which ones seem most plausible may be a good idea for some writers.
By now astronomers have discovered a number of stars systems with two or more detected planets in stable orbits.
According to one table, the smallest semi-major axis difference between the orbits of consecutive exoplanets is 0.0016 AU or 240,000 kilometers or 149,129 miles, between Kepler-70b and Kepler-70c.
[https://en.wikipedia.org/wiki/List\_of\_exoplanet\_extremes#Orbital\_characteristics[2]](https://en.wikipedia.org/wiki/List_of_exoplanet_extremes#Orbital_characteristics%5B2%5D)
There is so some evidence for a third planet in the Kepler-70 system, orbiting between B and c, which would make the difference between orbits even smaller, if confirmed.
But:
>
> If these planets exist, then the orbits of Kepler-70b and Kepler-70c have 7:10 orbital resonance and have the closest approach between planets of any known planetary system. However, later research[3](https://en.wikipedia.org/wiki/Alpha_Centauri#Controversial_and_hypothetical_planets) suggested that what had been detected was not in fact the reflection of light from exoplanets, but star pulsation "visible beyond the cut-off frequency of the star." Further research[8](https://planetplanet.net/2017/05/01/the-ultimate-retrograde-solar-system/) indicated that star pulsation modes were indeed the more likely explanation for the signals found in 2011, and that the two exoplanets probably did not exist.
>
>
>
[https://en.wikipedia.org/wiki/Kepler-70[4]](https://en.wikipedia.org/wiki/Kepler-70%5B4%5D)
the smallest semi-major axis difference between the orbits of consecutive exoplanets is about 11 percent between Kepler-36b and Kepler-36c. But the absolute distance between their orbits is larger than in Kepler-70.
>
> Kepler-36b and c have semi-major axes of 0.1153 AU and 0.1283 AU respectively, c is 11% further from star than b.
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[https://en.wikipedia.org/wiki/List\_of\_exoplanet\_extremes#Orbital\_characteristics[2]](https://en.wikipedia.org/wiki/List_of_exoplanet_extremes#Orbital_characteristics%5B2%5D)
The difference between the orbits of b and c is 0.013 AU or 1,944,772.3 kilometers, or 1,208,425.5 miles.
among exoplanets known to orbit in the conservative habitable zones of their stars, the smallest differences in orbits are in TRAPPIST-1 d, e, f, & g.
[https://en.wikipedia.org/wiki/List\_of\_potentially\_habitable\_exoplanets[5]](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets%5B5%5D)
>
> The orbits of the TRAPPIST-1 planetary system are very flat and compact. All seven of TRAPPIST-1's planets orbit much closer than Mercury orbits the Sun. Except for b, they orbit farther than the Galilean satellites do around Jupiter,[41] but closer than most of the other moons of Jupiter. The distance between the orbits of b and c is only 1.6 times the distance between the Earth and the Moon. The planets should appear prominently in each other's skies, in some cases appearing several times larger than the Moon appears from Earth.[40] A year on the closest planet passes in only 1.5 Earth days, while the seventh planet's year passes in only 18.8 days.[38][35]
>
>
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[https://en.wikipedia.org/wiki/TRAPPIST-1[6]](https://en.wikipedia.org/wiki/TRAPPIST-1%5B6%5D)
TRAPPIST-1d has an orbit with a semi-major axis of 0.02228038 AU, or 3,330,000 kilometers, or 2,069,166 miles.
TRAPPIST-1e has an orbit with a semi-major axis of 0.02928285 AU, or 4.380,000 kilometers, or 2,721,605 miles. Its orbit is 1,050,000 kilometers wider than that of d, or 31.5 percent wider.
TRAPPIST-1f has an orbit with a semi-major axis of 0.03853361 AU, or 5,760,000 kilometers, or 3,769,098 miles. Its orbit is 1,380,000 kilometers wider than that of e, or 31.5 percent wider.
TRAPPIST-1g has an orbit with a semi-major axis of 0.04687692 AU, or 7,010,000 kilometers, or 4,355,812 miles. Its orbit is 1,250,000 kilometers wider than that of f, or 21.7 percent wider.
[https://en.wikipedia.org/wiki/TRAPPIST-1[6]](https://en.wikipedia.org/wiki/TRAPPIST-1%5B6%5D)
Of course the star TRAPPIST-1 has a much different mass than that of Alpha Centauri A or Alpha Centauri B, and that may affect how closely it is possible to space planetary orbits.
The PlanetPlanet blog has a section, the Ultimate Solar System, about imaginary solar systems with large numbers of planets in the habitable zones.
[https://planetplanet.net/the-ultimate-solar-system/[7]](https://planetplanet.net/the-ultimate-solar-system/%5B7%5D)
In one post it is suggested that 4 planetary orbits would fit into the habitable zone of a star if all planets orbited in the same direction, while 8 planetary orbits would fit in the habitable zone if the planets alternated their orbital directions between prograde and retrograde.
[https://planetplanet.net/2017/05/01/the-ultimate-retrograde-solar-system/[8]](https://planetplanet.net/2017/05/01/the-ultimate-retrograde-solar-system/%5B8%5D)
I note that one planet has been confirmed for the Alpha Centauri star system, orbiting Alpha Centauri C or Proximal Centauri. You don't have to worry about such a distant planet messing up the orbits of planets orbiting A and B.
However, it is always possible that planets might be discovered orbiting Alpha Centauri A or B that would mess up the orbits of your planets.
[https://en.wikipedia.org/wiki/Alpha\_Centauri#Controversial\_and\_hypothetical\_planets[3]](https://en.wikipedia.org/wiki/Alpha_Centauri#Controversial_and_hypothetical_planets%5B3%5D)
I have heard of computer orbital simulators to calculate the orbits of spacecraft and of astronomical bodies. But I don't know if there are any available to the public that can calculate whether orbits will be stable for billions of years.
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[Question]
[
My creature, called the Kurbish, inhabits a wasteland-world, in my universe.
Recently, I have been wondering; "How plausible is this thing, **really**?"
A description:
Large, Elephant-like creatures that photosynthesise. They feature intelligence not unlike Humans. They grow a number of precious minerals in the crevices in their shell-like back, along the length of the spine.They can grow to be 125 feet tall, and can be up to 3 kilometers in length. They don’t have to traditionally eat, but they can eat and digest several types of rock and metal. The crystals on their backs grow as they age, and grow in various colors and types to represent the diets and emotions of the Kurbish. They have large tails, on which very precious minerals grow. The Kurbish have anywhere from 6 to 18 legs, and are able to communicate subsonically(around the same level as a black hole). They grow crystal tusks as they age, and they are able to regenerate if damaged or destroyed. They have around 28 eyes, with around 14 being on each side of the head. They are able to have multiple heads, albeit rare for it to happen.Their shells feature microbiomes, which changes according to the emotions, health, and age of the Kurbish. These microbiomes grow and change with the Kurbish.
Aside from the sizes, which is impossible for a normal, living, creature, how plausible would this creature be?
[Answer]
Slightly less probable than a unicorn that rides dragons (which, come to think of it, could possibly outsell Harry Potter as a YA series).
The way I see it, your main problem isn't that this thing communicates subsonically like a black hole (which, you might want to scale that up a little, the soundwaves from a black hole are bigger than the Earth). It could manage infrasound pretty easy.
It's not even that they grow precious minerals and gems. There are microorganisms that process gold, and some theories even say that is the reason we find gold in veins instead of smatterings (the paths of ancient microorganisms). Quartz crystals are easy to make, especially when processed from sandy soil. So if these things have a massive interaction with their microbiome, that changes based on their emotions (also not hard, since there is evidence that this is also true of humans), then the microbiome could be helping with the crystal growing.
No, your only unbeatable problem here is size. No land animal can be that big in Earth like gravity. Because mass increases as a power of three, but the size of bones and muscles increases as a power of two. Your weight simply outpaces the ability of legs to sustain it past a certain size [size limits](https://www.smithsonianmag.com/science-nature/why-king-kong-should-have-been-blue-whale-180962603/). I mean a redwood can manage it, but they can't walk.
And speaking of the walking, an elephant has to cover something like 80 miles a day looking for food. If this thing ate plants, it would have to have a thresher mouth in front of a race car to get enough. But energy absorption from sunlight is only about 3% efficient ( [Wiki](https://en.wikipedia.org/wiki/Photosynthetic_efficiency) ). So this thing really can't afford to move. Or even to really think, because intelligence takes a massive amount of calories.
But, they sound pretty awesome. So, maybe twist the facts some and make it so the crystals help gather sun? Or the minerals they eat have uranium and they are part nuclear powered? Or their shape involves very wide and squat legs that can support more weight, moving very slowly?
[Answer]
>
> They don’t have to traditionally eat, but they can eat and digest several types of rock and metal.
>
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**Not plausible**
Every living thing needs energy from somewhere in order to live. No exceptions, ever. This is not plausible. And, unfortunately, as you haven't given me an *alternate* range for your creatures size of 125ft tall, 3 klicks longs, I can't tell how plausible this could be if I assumed that it had a functional digestive system.
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[Question]
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I am writing a story that has insects the size of humans, but I am having a little trouble with the biology.
When you look up why there are no large insects on Earth, the most popular answer is that Square-Cube Law limits how large an organism their cardio-respiratory system could support. I feel like this is not that much of a problem to solve though. I just bump up the oxygen levels until things look about right and I'm done.
The problem I have is with molting. Each time an insect molts, it only grows a couple of centimeters. It would take decades just for my aliens to reach the size of a baby. Somehow, they need to grow an whole bunch every time they molt, and I cannot think of how.
In addition, for a while after an insect molts its new exoskeleton is much softer than it normally is. It is actually soft enough that if the insect is put into a confined space, its limbs will harden completely misshapen. Unless I make the gravity **really** low, the alien will not be able to support it how body weight.
Any ideas?
[Answer]
They could have their moulting process in water, this provides a safer environment and supports the weight of the creature. Like lobsters once out of their exoskeleton they could absorb water to increase their size. They could have a special bath or safe body of water designed for the moulting period.
On a side note lobsters die because the larger they grow the more energy consuming moulting becomes. Lobsters can be considered biologically immortal as they don't seem to slow down or weaken with old age, it is the moulting process that kills them, if predators don't get them first.
<http://www.veganpeace.com/animal_facts/Lobsters.htm>
<https://en.wikipedia.org/wiki/Lobster#Longevity>
[Answer]
It is possible that the insect like aliens might live in a microgravity space habitat with high oxygen content in the atmosphere (though great risk of fires). Possibly that habitat might have been constructed and their species created by a different, highly advanced alien society.
] |
[Question]
[
[](https://i.stack.imgur.com/OUkat.jpg)
I am currently writing a script for my graphic novel. My novel is in the fantasy genre and I use energy-based hard magic (that is energy-based magic that has its sort of "science" and rules). So I don't need my world to be 100% scientifically accurate in its functions, but enough for it to be believable to the reader. My world also utilizes retro-futuristic technologies.
The earth-like world in my story is unique in that the continents have been separated from the earth by god-like beings ordained with power from the world's creator to protect the world from a destructive evil trapped in the earth's core.
How would I make an Earth-like planet with aerial continents believable **and in what ways would this affect the weather, people, flora, and fauna of the continents?**
The floating landmasses are hypothetically close enough to the world below to retain normal atmospheric activity but high enough to be protected from the infected land below.
For additional information, my continents went aerial about 1000 years before my story begins. Also, my continents are powered with energy cores made up of intelligent magical magnetic energy. Also, the continents vary in size and proportions, but some are big enough to hold up to two or three well-populated cultures. More advanced civilizations in my story also harvest recourses from the earth's surface through mechanical processes.
I am not a very science-minded person, so any help would be deeply appreciated.
[Answer]
First off, this is a very cool concept! Your question is fairly broad, so I was going to answer a few different ways.
Society - just like how oceans and mountains separate societies and cultures in our world, the separate floating continents would likely give rise to different cultures. This would extend to their belief systems (do they all know/believe the gods raised the continents or do they each develop different beliefs about how/why floating lands exist? What legends have they come up with about the Earth's core?) and their technology (presumably, some societies would invent aerial vehicles to travel around while others might exploit natural resources - such as huge flying birds).
Biology - depending on how high up these continents are, your world's inhabitants would have adapted to slightly less gravity (though the difference is probably negligible) AND less oxygen. To be more precise, the concentration of oxygen is the same whether you are standing at sea level or on Mt. Everest (21%) but there is less atmospheric pressure, so it is harder to breathe. If your societies are human, their bodies would have adapted by breathing faster and producing more hemoglobin. Because of this, if the humans were to descend to the Earth's "surface", their stamina would likely increase since they are now presented with "more" oxygen for their bodies to use.
Economy - I imagine mining would be a great deal easier with so much of the underground earth exposed, so you might want to think of how a society would look with an abundance of precious metals. Would their currency be based on something entirely different from gold and silver?
Water - though it would still be replenished through rain, having rivers that flow off the continents would pretty quickly lead to a water shortage. So either water is very precious and/or they have much more advanced ways of saving water.
Land - earthquakes wouldn't exist, right? Is there a concern the continents might run into each other from time to time? Do they have technology to deal with this?
It seems to me that there is a lot you could do with this concept. Good luck!
[Answer]
## Erosion is not your friend, and stuff gets scarce
The answer to your question depends heavily on when the continents were lifted. If they were lifted after humanity evolved and spread, you'd see a very different result than if they were lifted when the dinosaurs roamed the Earth.
**Scarcity**
Your floating continents are only so thick, and if there is land below, perhaps they aren't continent-sized but instead country-sized. There are no oceans to fish, no oil fields to drill, and few if any volcanic minerals. You won't have coal or diamonds, and you'll probably have very little metal in general if the islands are as thin as those in the picture. Water will also be a precious resource gathered every time it rains, since any lake or river falling off the island essentially drains away.
**Weather**
The temperature of islands is still dependent on latitude; polar islands are cold, equatorial islands are hot. You'll lose many of the effects of living near the ocean, such as increased precipitation and moderate temperatures. Depending on the height of the islands, you may see them get very cold at very high altitudes - anticipate snow-capped mountains. Rainfall is also altitude-dependent, but I think it's safe to say your islands can get rain. My biggest concern is the effect of rain on geology.
**Geology**
Weather erodes terrain. Over millennia, rain reshapes landscapes; over eons, it levels mountains. If your continents aren't restored from underneath (read: plate tectonics + volcanism) the dirt will basically slide of the edges. This is bad news for your already resource-poor islands. This type of geology might make for some interesting features, though. Whole islands may calve and split like icebergs as they erode. I would also worry about erosion from underneath - condensation on the underside of the islands may create some gorgeous stalactites hanging down, but it will also eat away at the land.
**Evolution**
This topic is entirely dependent on how long ago your islands were lifted. On Earth, we see similar species on different continents (ex. American possums vs African possums) due to continental drift. We also see similar species because they crossed the ocean (ex. Galapagos tortoises vs those in continental South America) and sometimes even the same species on different continents (ex. humans). If each continent is totally geographically isolated, your species will likely evolve divergently faster, since their populations won't mix. Birds will be the only mechanism for spreading species (which is how some man-made ponds get fish in them!).
[Answer]
If your floating continents were originally land continents, the your oceans lost their shallow areas. So ocean fauna and flora that grew in depths less than 500’-1000’ lost 100% of their habitat.
So this could mean that there are no mussels, large crabs, lobsters, and none of the predators that feed on them. Also, I think there wouldn’t be any reefs or the creatures that live in them like moray eels.
There might be very small crustaceans like pill bugs and sand fleas. But terrestrial animals like birds that depend on tidal basins to hunt for food would be challenged to survive.
And given the height of land over the sea, sea otters and seals might be in quite the bind. Some might survive by living on subsurface extrusions of basalt rising from the oceans depth, but those are generally pretty rare compared to the lost coast line of the former continents.
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[Question]
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in the Cthulhu mythos, yog sothoth is depicted as a mass of splitting and fusing orbs, it is the past, present, and future and seemingly knows everything.
but for the sake of trying to make it realistic and more feasible, I’ll take away the god like attributes and try to see if I can make it into a creature of explainable evolution.
So, in the future, a group of scientists are sent towards a planet that is categorized to be able to support life. It indeed is capable of doing so, but the atmosphere and planetary pressures confine the scientist to ships and droids. After a week or so, they encounter a very interesting species, which they have code named them as, The yog sothoths.
**Appearance and behavior**
The species look like yellow soft orbs, seemingly capable of floating above the ground, this makes the scientist believe that the creatures are capable of keeping themselves aloft by using a specially evolved Buoyancy organ. The creatures are capable of eating both meat and plants, but will prefer dead organic matter, but upon feeding, they are extremely vulnerable because they take a long time to actually envelop and consume the food.
The species as a whole are social, and will protect the elderly and young of their group and are capable of communicating by either spraying pheromones or by making a low pitch of gurgles, growls, and thrumming noises. Reproduction seems to happen asexually, by budding off and forming a smaller version of itself, however, they will sometimes reproduce sexually by running into each other and staying connected for x amount of time, upon splitting, a smaller version of both will be a result of said splitting.
**intelligence**
Surprisingly, their seems to be a form of intelligence from these seemingly non sentient life forms. The adults of the group possess an intelligence compared to that of a 10 year old child, which results in them being vaguely more curious in things and have been seen to collect various rocks, plants, and sometimes animals, but will discard them when they have grown bored. There is evidence to suggest that their might be a brain, but sense in the future, there is a law that states that species can’t dissect or kill another intelligence being without consent.
**species variation**
If that wasn’t surprising enough, the group of scientists have found two different groups of the same species, ones with eyes, and ones with tentacles or tentacle like appendages.
The ones with eyes are seemingly more intelligent that the common yog sothoth, seen to be trying to at least observe and understand what humans are, and in one occasion, have been seen to even try to communicate with one of the scientists. There are only four eyes on an individual, and are formed one by one with age. This version of the species have been seen to form stone like tools and are capable of preserving the food within there body’s for later consumption.
Now, the ones with tentacle like appendages are presumed to be the best and most efficient hunters, seeing as how they are capable of hunting down other creatures. When said meal is caught, it will send tiny root like veins into the nostrils or eyes of the creature, seemingly trying to eat the vital organs, lowering the chance of escape for the creature. This variation of the species is a little more primitive in intellect, and seems to have one compared to a carnivorous cow, calm and not particularly dangerous when not Hungry, but voracious and efficient when hungry.
**extra facts**
Scientist have compared this creature to a highly evolve slime mold, which explains how its capable of doing the various things it’s capable of doing. The creatures are capable of forming small to large pseudopodia, but upon formation, it is seen to never retract back into the body, seemingly to not make any unnecessary appendages and to not waste precious energy. Lastly, it is theorized that if every single member of the species were to combine into a single one, it would require so much energy, that an entire land masses worth of biomass would be required to satiate such a form and its intelligence would be compared to an unspecified amount of humans, but this is only a theory and there is no evidence to support it.
Could such a species ever feasibly exist, and if not, then what **is** feasible?
[Answer]
## Fungal jellyfish balloons
These creatures are plausible. Difficult to justify evolutionarily, but plausible. Let's break it down.
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**Buoyancy:** Hydrogen bladders
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> the **atmosphere and planetary pressures** confine the scientist to ships and droids... The species look like yellow soft orbs, seemingly **capable of floating**... using a specially evolved **Buoyancy organ**.
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Many fish use [swim bladders](https://animals.howstuffworks.com/animal-facts/question629.htm), which they fill with oxygen in order to change their buoyancy. However, your creatures are submerged in air, not water. Although the atmosphere is thick, which should help with buoyancy, it's unclear how thick it is, so I suggest using hydrogen. Your best bet is to break down water molecules and [use the hydrogen to float](https://worldbuilding.stackexchange.com/questions/11208/are-flying-plants-possible?noredirect=1&lq=1) like a [living gasbag](https://tvtropes.org/pmwiki/pmwiki.php/Main/LivingGasbag).
These organs will have to be extremely fine-tuned; whereas water produces large drag forces on ascending fish, and they reach the top of the ocean relatively quickly, your gasbags may risk floating to the top of the atmosphere. They will likely ascend/descend using extremely slow, passive, incremental hydrogen adjustments. Evolutionarily, you can justify this by putting lots of predators on the ground but few in the sky.
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**Eating:** Extracellular digestion + omnivorous lifestyle
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> ... upon feeding, they are **extremely vulnerable** because they take a long time to actually **envelop and consume the food**... it will **send tiny root like veins into the nostrils or eyes of the creature**... lowering the chance of escape for the creature
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Yog sothoths move slowly because they float. Often, they may choose to passively drift to new food sources, but when they choose to actively propel themselves by releasing gas or flapping their appendages - they won't be fast enough to catch large prey. Attacking eyes or nostrils first makes little sense because such a slow-moving creature could easily be walked away from.
They will adopt an extracellular digestion mechanism [like fungi](http://website.nbm-mnb.ca/mycologywebpages/NaturalHistoryOfFungi/Physiology.html). Since fluid-filled stomachs are heavy, and putting whole creatures inside them will weigh your creatures down even more, they won't have stomachs at all. They will use small hyphae to anchor to plants, insects, or dead animals, and they will secrete digestive enzymes from their hyphae to dissolve and consume them. If you want to maintain the nostrils and eyes part, maybe those orifices provide the best direct access to nutrients.
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**Communication:** Vibration and pheromones check out
>
> The species ... are capable of communicating by either **spraying pheromones** or by making a **low pitch of gurgles, growls, and thrumming noises**.
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Fish can use their swim bladders both to produce and receive sound. If yog-sothoth are mostly empty air-sacs, they can definitely utilize their structure for communication. Pheromones may make more sense as a passive means of communication; I get the impression that these are relatively low-activity creatures due to the energy constraints of floating in search of food, so "smelling" may make more sense than "talking".
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**Reproduction:** Budding checks out
>
> Reproduction seems to happen **asexually**, by budding off and forming a smaller version of itself, however, they will sometimes reproduce sexually by running into each other and staying connected for x amount of time
>
>
>
Budding is consistent with the passive, fungal qualities of their method of digestion. They may also consider releasing spores in order to start new colonies. A species with both sexual and asexual reproduction is plausible, but the sexual reproduction part may be dependent on how easily these creatures can locomote.
---
**Intelligence, Eyes, and Tools:** Yes, maybe, no
>
> ... their [sic] seems to be a form of **intelligence** from these seemingly non sentient life forms. The adults ... have been seen to **collect various rocks**, plants, and sometimes animals... There is evidence to suggest that **their might be a brain**... scientists have found two different groups of the same species, ones with **eyes**... There are only four eyes on an individual, and are formed one by one with age. This version of the species have been seen to form **stone like tools**
>
>
>
Human brains are heavy, and they take a **lot** of energy. Floating creatures are by definition light, and they may not eat frequently enough to meet the energy needs of complex brains. If you scale up their hydrogen bladders to match heavy brains, you'll need to provide even more food.
One possible solution is to settle for insect-like brains. Consider cockroaches, which have [ganglia all over their bodies](https://www.quora.com/Do-cockroaches-have-more-than-one-brain) to control separate segments. Your yog sothoths could start by having nervous systems spread over the surfaces of their hydrogen bladders in order to receive sensory information and control hyphae growth. Then, the density of their nerves could increase, creating a woven-mat-brain system under their skin. It would be less heavy than a human brain, and probably less powerful, but at least on-par with insects or rodents.
Eyes are harder to account for than brains, because other senses have the potential to be cheaper for a passive organism. Consider that their bladders could be used like giant ears for echolocation, or their pheromone senses could also smell predators and prey. You could definitely still have eyes, but they would shift the classification of these creatures on the plant-animal gradient.
Tool use seems hardest to explain. Stone tools are heavy, and your creatures want to stay afloat. They probably don't have skeletons to anchor grasping arms onto, and tentacles attached to fragile floaters may not be very strong. What about simple tools, like twigs?
---
**Pseudopodia + Megabrain:** Not plausible
>
> The creatures are capable of forming small to large **pseudopodia**... if every single member of the species were to **combine into a single one**... its intelligence would be compared to an unspecified amount of humans
>
>
>
What use do pseudopodia have if these creatures only descend to feed? Maybe if they get so heavy after eating that they have to walk - but then I suspect they would just go dormant.
Furthermore, if every human brain was combined, they would surely have significant computing power; that doesn't mean a mechanism exists to facilitate such a connection.
---
## **Conclusion**
Yog-sothoth are plausible as floating, omnivorous gas-bags that graze on plants and dead animals using hyphae. Their airborne nature limits the weight we can give them in terms of stomachs or brains, but complex organs are still plausible.
] |
[Question]
[
Throughout the world, it is generally recognized that the Democratic movement in Beijing started as a public memorial of the former Chairman Hu YaoBang, who past away on April 15th, 1989 after being ousted by Deng XiaoPing. Slowly, people turned this as a chance to demand more freedom of expression, freedom of Press, and called for an investigation of corruption within the government. The scale and intensity of protest increased, particularly after the Editorial on April 26th. (this period is where rumors of students faked hunger strike, looting, and burning soldiers started to spread, so I will not say what happened at this time)
This lead to Gorbachev seeing protesters on TianAnMen Square, which made Deng XiaoPing looked bad. Eventually, after the Progressives in the Party lost the political struggle, the Army came in and the rest is history. What I want to know is not what actually happened, but what could be changed in China's History after the Korean War so that this Protest could turn China into a more democratic country with the protected right to freedom of expression? (I am thinking about something similar to the "Modern Way Program" in Command and Conquer General lore, so whether China remained a one-party rule or multiple parties are fine)
My guess is...Shorter Cultural Revolution caused by the earlier death of Mao would lead to more surviving intellectuals, who will then lead the protest instead of the young and radical students.
[Answer]
Your guess of a shorter Cultural Revolution is most likely change. I would go further, in fact this was my first thought, of No Cultural Revolution.
Essentially the Chinese Communist party leadership ensures Mao Zedong's enforced retirement in the aftermath of the Great Leap Forward. Mao is unable to rebuild his power base in Shanghai. This could be accelerated with the early death of Madam Mao as her political background was Shanghai and she may have been instrumental in facilitating Mao's return to effective power which, in turn, enabled his instigation of the Cultural Revolution.
Why bother with half measures? Get rid of the Cultural Revolution entirely and the probability of the Democratic Movement succeeding increases dramatically.
**FOOTNOTE:**
For those less aware of Chinese history in the 20th century one of the major terrors that inspired the Tianmen Square massacre and the subsequent political crackdown on democratic trends was the fear that the student movement and associated trends would lead to another Cultural Revolution. Many of the Chinese leadership in 1989 suffered terribly during in the Cultural Revolution. Vide Deng Xiaoping. Also, they were older and less resilient, therefore, less likely to survive a repeat performance of a Cultural Revolution.
] |
[Question]
[
Think of a thunderdrum from the How To Train Your Dragon movies for its large mouth, but it has a wingless centaur shaped body. It has a large head that can open its mouth wide. How would it create a concussive force with its mouth? I had planned for this creature to be on land, but how it might work for underwater would be useful too. I remember at Sci-port there was this drum that if you hit it it would make these stringed cds hanging from the ceiling move from the soundwaves. Maybe it uses a similar method but more powerful.
I imagine it chasing a group of animals and using the sound force to herd them at some point in it developing a civilization.
[Answer]
**Real Life Examples**
In WW2 the Nazis experimented with a sonic weapon that used pulse-jet style detonation chambers and resonance to create extremeley loud soundwaves. If two of these units were set up and focused on an overlapping point the sound compression waves generated could, if given enough exposure, kill. That is, if you managed to get anybody to hang out in a very specific area right in between two of them for about 30 minutes. Also each was about the size of a house. Pretty much totally useless as weapons.
In the late 50's a plane was built by the US government, the XF-84 Thunderscreech. It posessed a super-sonic prop, which when turning at full speed produced a rippling series of sonic booms from the tips of each propeller. The resonance in certain hangar structures or nearby aircraft caused damage to them. There are even reports of personel working in enclosed spaces with it suffering detached retinas and siezures.
**Problems with this as a biological process**
In our atmosphere sound has a top speed due to the ability of our atmosphere to conduct sound waves. In our atmosphere sound travels at about 343 meters per second, dependant upon altitude, humidity, and temperature. This means no sound on earth, at sea level, can exceed about 194 decibels. To produce this sound you must generate compression waves by rapidly oscillating between a vacume and +2 atmospheres of pressurization. No small feat. To give you an idea of just how loud that is and how difficult it is to hit the maximum decibel level, When Krakatoa erupted and was heard around that hemisphere, it was "only" 172 decibels.
Also, "sound" doesn't push things. Waves of compressed air do, the sound is just a byproduct. So your critters dont have to be loud, they need to be able to compress air and direct it at a target. We're at this point more talking about generating explosions rather than sound. I do not feasibly see a living creature under currently accepted theories of biology being capable of doing this naturally. The kinds of forces required are going to be harful or lethal to anybody/thing immiediatley nearby not to mention the creature emitting them, thus not likley biologically generated in origin. Anything generating forces like that is going to be exposed to them too.
**Answer**
I do not believe there is a realistically feasible method to achieve these kinds of forces biologically. Sound can be used in other ways, like to irritate a target and convince it to move, but not to generate the kinds of forces you are looking for without also causing an equal (but probably greater) amount of damage to the creature generating them.
**Doesn't mean its not feasible**
Instead of physically shoving them with compression waves, your creatures use the sound they generate to modify herd animal behavior. Lets say they can emit a very loud, very well focused "beam" of sound. There are riot control devices made by a company called LRAD that produce extremeley loud, very tightly focused sound beams, (up to 30° beams.) These can cause anything from nausea to irritating pain in rioters ears, and can be aimed at individuals if close enough.
Typically, it is so loud, and uncomfortable, the targeted person or persons will attempt to move away from the source of the sound produced by this device. I'd say that maybe your creatures can use this to aim the sound admitted towards one side of the animal, causing it to instinctivley move away from it in a more desired direction. In this manner they manage to herd thier animals in desired directions of travel.
[Answer]
The way the Thunderdrum was animated made it seem like it could open its mouth and the air would instantly ripple outwards just because of how loud the dragon was, but that is probably not an accurate portrayal of real-life biology considering how skinny and short in length the Thumderdrum is. However, to produce sound waves with such power, you would need to be able to compress the air enough to make it move at the speed of sound without damaging the organism's internal organs. This concept would probably be best represented by aquatic animals such as the mantis shrimp as mentioned above, and some whales such as the blue whale or sperm whale.
] |
[Question]
[
just looking for a quick accuracy check of my continent's biome/climate map. This continent is on a planet much like Earth and it is about the size of Eurasia. It is situated in the southern hemisphere. The mountain range in the temperate forest area is a very old weathered range similar to the Appalachians, hence I left out a rain shadow.
Just looking for any major inaccuracies that need to be fixed.
Thank you!
[](https://i.stack.imgur.com/bnDXB.jpg)
[Answer]
You have a huge continent which is also almost square, so its center will have very continental climate, one which tries to maintain either -30C or +30C at all times.
This is your "temperate grassland" which instead would have climate like Mongolia or Kazakhstan.
Also, the green area in the desert's upper left corner should be flipped - it will get its rains from air coming from sea and captured by mountains.
[Answer]
I scratch my head at seeing that along the tropic you have desert and tropical rainforest, and that you transition from the tropical rainforest to the temperate forest with nothing in between when you go more to the South.
That seems quite odd.
[Answer]
I have only one suggestion: with the amount of 'squeezing' of the tectonic plates you have here, you should probably create a solid volcanic trench on the other side.
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[Question]
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As the title says, Is it possible to map the firing of neurons in the human brain so as to stimulate artificial memories to the amnesiac person?
This is based on this similar question; [*Is it possible to map the firing of neurons in the human brain so as to stimulate artificial memories in someone else?*](https://worldbuilding.stackexchange.com/questions/143037/is-it-possible-to-map-the-firing-of-neurons-in-the-human-brain-so-as-to-stimulat)
Those answers basically say it is impossible to send the pattern to another person because they have different brain patterns, but what about sending it to the same person that lost his memory?
its not necessary using today's technology, but at least achievable in the future or might be theoretically possible.
[Answer]
# Depends; Probably Yes
Memory is largely still a mystery to us. Current theories vary widely, and all lack sufficient scientific backing. I will focus on the theory of memory which I, personally, think is most likely to be true - although, again, memory is mostly a mystery to us.
The theory I like the most is, basically, that thoughts are nothing more than patterns of neurons in our brains. Furthermore, a "memory" is simply that pattern of neurons firing, and "recalling" a memory would be that pattern firing again in your brain. As such memory is not a "thing" that is stored, which means it cannot be read or copied after the fact; the only way to "record" a memory would be to either (a) capture the thought as it occurs, or (b) have someone "recall" a memory, and capture that neural pathway as it happens.
In a futuristic setting, maybe we have learned more about how these neurons fire with one another, and can then create these memories on a computer, or something of the like.
Neither your question nor this answer address *how* this will occur. You reference a similar question where the answers say transmitting memories to others is "basically not possible" because of different brain structures. I have a slight disagreement with that - in a futuristic sci-fi setting, will we be able to *reconfigure* brain patterns? It's not so far-fetched as to be "impossible", and depending on how practical you want your story to be, I think this can be hand-waived some. If we can stimulate neurons to move around inside a brain, then we can place neurons in the right order so as to have - and fire - the memory pattern. Or maybe you scramble their brain to the point they can't function and fall over dead.
That said, some of the (well documented) cases of dreams or memories which occur from organ donors to their recipients tells me that how our bodies interact with the world, our organs, feelings, etc, allows for *some* memories to move if brains are *similar enough*. While brains may be 99% unique, if there is 1% in common, then *some* memories, feelings, etc, can be shared. *Theoretically*
If someone with amnesia - likely from a brain trauma - can't recall certain memories, that means their neurons have shifted around enough that the neural pathways aren't firing. Their brain is likely similar *enough* to be reminded / reordered to then recall *some memories*.
Given that people with amnesia do often regain their memory through natural means, I don't see any reason why a futuristic technology could exist to either aid in this recovery, or simply perform the recovery function through some invasive means.
In any case, the question becomes *can the neurons be ordered in such a way that this specific pathway [memory] can be triggered?* If so, then the answer is *yes*. Given that (a) this is the theory of memory that makes the most sense to me, albeit lacking scientifically, and (b) the amnesiac's brain is likely *close enough* for those patterns to be available, then I would say **probably yes**.
[Answer]
**Instead of the memory, you could reply the exact sensations the person felt at the time.**
Memories are weird. They are not sensations. They are something that long lived cells in the brain can do. Impulses in sensory and motor nerves are much less weird.
In the story Isis and Augi, Augi is an artificial intelligence worn by Isis, a woman. Augi can detect all impulses moving through Isis' nerves, and it can affect and produce those impulses. In this section, Isis learns that Augi keeps a record of all of those impulses, and can play them back.
<https://www.fictionpress.com/s/3341845/5/Isis-and-Augi>
>
> Trotting towards the gate, Isis thought about the man who had sat with
> the council. “I feel like I have seen him before,” she said out loud.
> “The new man, two back from Gradley.”
>
>
> “You have seen him,” said Augi.
>
>
> “Where?” asked Isis. She asked even though she knew it was pointless to ask. Augi was terrible with names and even worse with
> time.
>
>
> “I do not know how to tell you,” said Augi. “I could show you,”
>
>
> Isis raised an eyebrow. “Show me how?” she asked. “Not a drawing, I hope.”
>
>
> “Not a drawing,” said Augi. “I will show you now. Be ready.”
>
>
> And she was on Valusia. Everyone in town came out at night after the heat of the day. She pushed through the crowded street,
> feeling sweat in the small of her back, strange spices lingering on
> her tongue. Her clothes did not fit: sheath pants, the fashion in the
> capitol – stolen in haste, and too tight. Hair fell into her eyes and
> she pushed it back – it had been longer then. She shouldered her way
> through the crowd, looking over her shoulder. What was she looking
> for? Why did she feel so sick? She remembered – that animal they kept
> had bitten her. Augi was keeping her going but the nausea
> chemoreceptors were deep and out of Augi’s reach. Perfume from the
> flower trees lining the road was cut by the bitter smell of burnt food
> coming from a cart. A group of teenagers brushed by her, making her
> stumble. She was a passenger in her own body, feeling herself move her
> own legs, turn her head. A woman shouted ahead of her.
>
>
> And she was back in the colony. Isis looked around, dazed. “I used to have a butt,” she muttered. “Are we working out too much?”
>
>
> “Did you see him?” asked Augi
>
>
> Isis took a deep breath. “That was two years ago!” exclaimed Isis, collecting her composure. “Augi!” She paced around in agitation.
> “You can do that? Play it back? I didn’t know you kept things! Why did
> you keep that?”
>
>
> “I keep all of that,” said Augi carefully.
>
>
>
Of course this is not possible with current tech. But a nerve impulse is electrical, and so generates a magnetic field which should be perceptible and measurable at a distance. If the measuring device were accurate the functions of each individual nerve could be recorded. By applying an external magnetic field one can induce an electrical impulse. If magnetic fields could be applied with precision it would be possible to recreate in the nerves the same impulses recorded at an earlier date. That is what Augi did with Isis, so she could relive that minute and learn what she needed to learn.
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[Question]
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It's 20 years into the future, and humanity is (trying to) reaching for the stars. And congratulation, we have met a lot of quirky alien civilization, as per SF tradition. Unfortunately, this isn't Star Trek, so conflicts do happen. Luckily, this isn't 40k either, so none of the star-faring nations are going for total war here. So long as human ships can prove themselves capable of fighting in a skirmish, the media (human *and* alien alike) is going to blow it up to the point everyone thinks we can handle a space war, and ironically, no full-scale war is going to happen.
The problem, of course, is that the majority of alien crafts are protected using energy shields, which render many types of weapon inefficient, however. As far as that future scientific understanding goes, the best way to beat them is with a large dose of neutron radiation to penetrate and destroy the shield mechanism underneath, which weapons would be the best to do so?
We are assuming that with futuristic technologies, anything modern piece of technology on Earth can be mass-produced reliably, at record-level performance, in space. The neutron source is standardized, the same amount of reaction material create the same impulse of radiation, regardless of weapon. Costs, weight, and other factors will be considered, but only as secondary, after 2 main criteria:
1. Damage: The amount of radiation delivered to the target
2. Combat usability: How good that bundle of radiation is at getting to a moving (though still limited to dogfight combat speed, since the enemy also want to shoot, too, and their targeting system is not noticeably better than ours) target in space
The 2 ideas I have in mind are missiles and beam weapons. Of the 2, missiles with neutron bomb warheads seem like it should do more damage (it is a modern weapon, after all), but also seem a little bit too easy to counter (speed, point-defense weapon, etc.). Whereas it is impossible to dodge a neutron beam, but people keep them in labs, and not battlefields for a reason, right? Is there any other way to deliver radiation accurately to a distant spot in a vacuum?
[Answer]
I'd discard the idea of neutron beams, unfortunately. Whilst a working neutron beam would be an extremely effective weapon regardless of whether the target is shielded or not, making such a thing seems somewhat implausible outwidth a magical way to accelerate neutrons.
Firstly, generating such a beam is problematic. Once you've generated it, focussing it is problematic... modern spallation sources, for example, aren't particularly collimated, eg. they fire the damn things out in all sorts of directions, and fancy grazing-incidence mirrors can only really work on neutrons that are already heading in roughly the right direction so you'll lose a lot of neutrons and generate a lot of waste heat. Even once you've focussed it, you'll still have limited range due to thermal blooming (basically, neutrons in the beam bumping into each other causing the beam to spread out). No handwavium neutron accelerator, no neutron beam.
Now, lets talk about neutron bombs. An excellent way to generate an awful lot of neutrons, in a military context, is to use a fusion explosion. D-T fusion, one of the easiest reactions to spark off, generates over 15 times more neutrons for a given mass of fuel than U-235, and the neutrons it generates are much higher energy (about 15 times more again).
Problem: fusion reactions are difficult to kick off. Modern nuclear weapons do this with the aid of a fission primary, but the size of the fission primary is limited by the critical mass of fissile material which can often be many kilos. You also need a very carefully controlled detonation of an implosion-type fission device, which just increases the hassle.
How do you make a fission explosion with a tiny subcritical mass? Well, one way to do this is to use a very small amount of antimatter. Have a look at the [ICAN-II](http://www.projectrho.com/public_html/rocket/enginelist2.php#acmf) antimatter-catalysed microfission rocket design. A tiny pulse of antiprotons (less than a femtogram) is fired into a 3 gram uranium pellet, causing it to fission and release a healthy number of gigajoules of energy. This can be used as the primary in a more conventional (but miniaturised) 2-stage [Teller-Ulam](https://en.wikipedia.org/wiki/Thermonuclear_weapon) thermonuclear weapon, with a radiation case chosen to be as neutron-transparent as possible. Now you have the basis for a tiny neutron source, maybe only a kilo. You don't need access to massive amounts of exotic materials, like plutonium or antimatter... a few kilos of uranium and a nanogram of antimatter will supply thousands of micronukes. You just need to supply the tritium to get the party going.
For your next trick, you will need a high-velocity projectile weapon, such as a railgun, coilgun or powerful rocket engine (though the previous two are likely to be more economical here). The projectiles won't travel at a significant speed of light, unlike a laser or neutron beam. Make up for this by firing Quite A Lot of them. Most of these projectiles will be dumb metal slugs, but some, say, one in every hundred, are your micronukes. Throw a lot of rounds down range. Ships have a limited ability to dodge, especially when the incoming fire is a big cloud of hypervelocity crud. They have a limited ability to intercept these weapons with point-defense fire... they're small, hard to see via any spectrum and coming in fast. And they have to shoot *all* of them, because the one they let though might be the micronuke.
After a few skirmishes with your new toys, maybe you'll be able to collect the weapons that the aliens use to oppose shields, and use something sensible instead...
[Answer]
A fission or fusion nuclear reactor or some form of high powered cyclotron or synchrotron aimed at a solid (spallation) target would be capable of producing a large neutron flux of the order of 10^15 neutrons / square cm for the reactors and in the case of the spallation target method a neutron flux in excess of [10^17 n/square cm](https://en.wikipedia.org/wiki/Neutron_source#Nuclear_fusion_systems) is possible.
It is also possible although difficult to [focus a neutron beam](https://spie.org/news/5243-a-new-generation-of-neutron-focusing-optics?SSO=1). So a large synchrotron projecting into a spallation target with a specialist Wolter optics for focusing neutron should do the trick. However is would be very heavy, very large, very energy intensive to run and very expensive as well.
[Answer]
It's time for my [favourite space weapon](https://worldbuilding.stackexchange.com/a/107725/29969).
# Sandcasters!
A sandcaster missile is about as simple as it gets. Fill a regular missile with sand, put a conventional explosive in the middle so the sand disperses nicely, shoot it towards them at relativistic speeds, and blow it up outside of their point-defense range.
It doesn't even have to be sand. It can be lead ball bearings, for extra kinetic energy, or even...
*Tiny neutron bombs...*
Design a small neutron bomb that explodes on impact. Pack them into your sandcasters. follow above procedure.
You can't dodge them all. Or see it coming, since the light informing you of the missile's presence doesn't appear long before the payload. Send regular sandcasters after your neutron ones if you want to actually blow anything up.
In regards to "dogfight speeds", shoot the missiles from very far away.
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[Question]
[
I mean as in a city that is not situated at the bottom of the ocean but is not floating on the surface of it either. What would a plausible size and population size be for this kind of construct? Could humans live in such an environment for their whole life? And how deep could such a thing be able to go? I know we(humans) are researching/developing ways to grow food in outer space, so could that technology be used in this as well? And if we can grow vegetables and/or fruit would it be possible for animals to live in the city as well?
[Answer]
The closest thing we build looking like what you describe are nuclear submarines. They can spend a lot of time underwater, taveling around at various depths, and considering their crew they could be seen as small villages.
However they depend on land for their sustenance: supplies, fuel and obviously crew all come from there.
In principle it would be possible to use a nuclear power plant to supply hydroponics and start a food chain on board to supply the crew.
The problem would remain for the nuclear fuel and the spare parts. I doubt that such a thing would have more than a few years of autonomy, at best.
] |
[Question]
[
Menzoberranzan is a large, elven nation of [Drow](https://forgottenrealms.fandom.com/wiki/Drow) that worships an ancient pagan religion that revolves around quasi-Wiccan traditions. This nation worships a religion revolving around nature with a male deity at its head. In truth, this is a symbolic position, and the nation is geared toward a matriarchy.
This culture practices a form of ritual sacrifice called the Day of Death and Rebirth. In this custom, a male drop is selected to be king of the drow for the period of 1 month. This "king" is the representative of the male deity on earth and the embodiment of all its virtue. The individual lives in luxury during that time period. At the end of this month, he is ceremoniously placed into a large bipedal structure in the form of the male deity and burned to death. This structure is 30ft high in the shape of a male drow. The god only accepts sacrifices of individuals who come of their own free will. Therefore, society is seemingly male-centric on the surface, highly reverie and honoring them while giving them a sense of control.
The sacrificial king willingly gives up his life, believing that he will become one with the deity upon completion of the ritual, just as the many kings before him.
My issue is the construction of such a large object, as it appears that such a device would have been neither practical nor realistic. Although wicker objects are said to be quite strong, they would lose their structural integrity quickly when set on fire. The elf form is human-like, and as sculpture is not stable. The taller they are, the stronger the legs and supports have to be. The more propping up you have to do. It is very difficult to get them upright and the more likely it is that the strain of lifting will cause the structure to fail.
I need this large structure to be able to stand upright and burn efficiently so that the king is sure to die. How can I make this happen?
[Answer]
I think there are a couple of design elements that can help the structural integrity of your Burning Drow.
1. Plait a single internal structure, using the drow skeleton as a blueprint, as tightly as possible. Except, extend the leg bones well past the feet so they can be buried in the Earth, like stakes driven into the ground. This will let the dense skeleton burn slowly and support the rest of the structure during the fire.
2. Mix wood types in constructing the Burning Drow. Use hardwoods for structural elements. Use pitchy wood that will burn hot for the cage enclosing the sacrifice.
3. Have a large bonfire at the base of Wicker Drow so the victim is subjected to the chimney effect and dies quickly.
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[Question]
[
In the somewhat near future (50-200 years) the government wants to repopulate the city of [Pripyat](https://en.wikipedia.org/wiki/Pripyat). To limit radiation, they decide to send the remains of reactor 4 into space (which is possible due to the brand new handwavium engines they use). But due to unexplained reasons, the rocket explodes in the atmosphere.
What are the consequences to earth depending on the altitude it explodes at?
The rocket body is made of a handwavium alloy completely radiation and heat-proof but not neccesarily super strong. When one of the engines explodes, it causes a chain reaction pulverizing the whole rocket, creating a cloud of radioactive dust in the skies.
[Answer]
The result would be [drum roll] not very much.
At present the material remaining in the reactor building ruins has been decaying for 33 years. In another 50 years it will have been decaying fully 80 years.
This is trinity crater, the site of the first atom bomb. I've been there. It was exploded in 1945, so is now just over 80 years old. The radiation is round about double normal background, as measured by a guy wandering around with a Geiger counter. A guy in shorts and sandals. No special radiation protection is required. It's a tourist site with kids and old people wandering around.
[](https://i.stack.imgur.com/7TrKt.jpg)
The only real protection needed is to prevent people taking chunks of Trinitite as souvenirs. I bent down, picked up a chunk, looked around at the guy in army gear and carrying a machine gun. And he was *looking* at *me*. So I carefully put the chunk back, and he relaxed.
[](https://i.stack.imgur.com/7oN2p.jpg)
By the time of the beginning of your scenario, the material from Chernobyl will be marginally more radioactive than the Uranium that was mined to produce the fuel. By the end date of your scenario it will be round about the same. If you dumped roughly 100 tonnes of Uranium out of a rocket the result would be much more worrisome from the standpoint of heavy things falling from the sky than it would from radiation.
The real question is, why would anybody bother shooting this stuff into space? The energy costs would be huge, and the benefit is minimal.
Edit for comments.
Only a small fraction of the Uranium in a nuclear weapon fissions, typically a [few percent.](https://gizmodo.com/less-than-2-of-the-uranium-in-the-hiroshima-bomb-actua-1624444762)
The [fission products](https://en.wikipedia.org/wiki/Nuclear_fission_product) from a weapon are similar to that in a reactor. There are minor differences in the concentration of different isotopes. The Uranium that does not fission goes through very similar reactions as in a reactor.
The danger of an isotope depends on the half life and the amount, but also the kind of radiation it emits, and how well absorbed it is by living things.
If the half life is very short then the isotope is dangerous but decays quickly, so after several half lives it becomes much less dangerous.
If the half life is very long then it produces very little radioactivity per hour.
[Neptunium has](https://en.wikipedia.org/wiki/Neptunium) isotopes with half lives of 396 days or less, or over $1.54\times 10^5$ years. So at 80 years pretty much all the dangerous stuff is gone.
Plutonium is primarily an alpha emitter. Unless you eat it, it's not really a problem. Similarly, Uranium is primarily an alpha emitter.
The dangerous items are the fission products with intermediate half lives, that are gamma emitters, and that are also absorbed by living things. The big ones are usually Strontium and Cesium. [Scroll down this article](https://en.wikipedia.org/wiki/Nuclear_fission_product) to Health Concerns.
From the same article comes this graph. 10 thousand days, has already passed, and the total gamma dose is already less than 1% of what it was shortly after the accident. The decay continues, and in another 50 years will be much smaller than that, probably about .01 percent of the first day dose.
[](https://i.stack.imgur.com/VAWL0.png)
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Nothing good at any altitude. Regardless of where it explodes on the way up the act of exploding will reduce large quantities of radioactive debris to fine particles that wind will be capable of moving around. The original blast sent about 15 tons of radioactive debris, 5% of the total fuel at the plant, (about 400 times what the Hiroshima bomb put up) and a small percentage of that debris traveled around the world on the wind. This explosion would do the same, only much more so and that's if it goes off on the launch pad. Europe got it worst last time and probably will again since the prevailing winds are East-West, but everyone will be badly effected, depending how much of the material gets into the air it could kill a large cross-section of all life in the northern hemisphere.
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Flame lickers work by sucking hot air into a cylinder and then relying on the cooling of the air by the cylinder wall to create a partial vacuum to pull the piston back.
[see video](https://youtu.be/7p_1QO1iG9M)
In an alternate time line, could this engine cycle be improved by splitting the intake stroke and the exit stroke between two separate cylinders. The exit stroke would be using a smaller cylinder, and between the cylinders would be an intercooler.
This would increase the surface area which cools the gas\* and reduce the repeated heating and cooling the piston and cylinders\*\*.
Or has this engine already been invented?
\*the intercooler would have a much larger surface area than the cylinders
\*\*like the early steam engines
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Essentially you are dealing with fairly primitive hot air engines, and the splitting between two cylinders is similar to early [Brayton "Ready Engines"](https://oldmachinepress.com/2016/12/05/brayton-ready-motor-hydrocarbon-engine/). Indeed, atmospheric engines were described by Hero of Alexandria as far back as the First century AD, so this type of technology has a long history.
The limiting factor with any sort of atmospheric engine is there is a hard upper limit to how much power you can produce. Even if you could somehow arrange for a perfect vacuum, the maximum force pushing on the cylinder is 15 PSI (101.325 kPa). You would either need an improbable number of cylinders or really huge ones to generate significant force.
Adding extra stages as you suggest would improve efficiency somewhat, but there would be additional parasitic losses from the extra linkages and the airflow through the cylinders and heat exchangers. Without the actual design it is impossible to calculate how much loss you will get, but at some point it is fairly certain that the losses will outweigh the potential gains. With primitive, hand made machinery this will become a very large effect very quickly.
So while it is possible to build atmospheric engines and add additional stages to increase efficiencies, there will come a point that the extra machinery is actually drawing more power from the engine than it is contributing. Unless there is a very compelling need to gain extra power from the engine, economics suggests that the advantage will go to the most basic engine capable of doing the job, since it will be cheaper to build and operate.
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Given a rotation rate comparable to Venus & axial tilt like Uranus (about 90deg), what should I expect for atmospheric winds? I anticipate a stratospheric wind only, dropping to the surface at or near the terminator (only), but not much in the way of storms, due to low Coriolis effects. Am I wrong?
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## Super-rotation
As I wrote in [an answer to another question about winds](https://worldbuilding.stackexchange.com/a/141419/627), [studies of slow-rotating planets like Venus](https://arxiv.org/abs/1709.03676) have yielded information about what we should expect for planets like this in general:
* The troposphere may exhibit something called super-rotation, meaning the atmosphere rotates faster than the planet. This will cause fairly strong latitudinal winds at about 100 km up; for Venus, these winds may be [a couple hundred miles per hour](https://www.windows2universe.org/venus/venus_polar_atmosphere.html&edu=high).
* The Coriolis force is so low because of the planet's slow rotation speed, so instead the centrifugal force is the main influencer of the pressure gradient in the atmosphere; this contributes to wind direction differently than on a fast rotator like Earth.
I should note that super-rotation is a highly complex phenomenon that is influenced by a number of factors, among them Venus' high temperatures and thus extensive Hadley cells. However, the phenomena which I've described should be applicable to any slow rotator, to various degrees. They may be weaker on planets with lower surface temperatures, but
## Storms
Your argument about large-scale cyclonic activity being absent because of the low Coriolis force is correct. Hurricane-like storms require the Coriolis force to form, and as Venus' angular velocity is about 0.4% of Earth's, the Coriolis force should be over two orders of magnitude weaker. We can assume that they effectively do not exist.
Now, non-hurricane-like storms should still exist on Venus. [Lightning may have been observed](http://adsabs.harvard.edu/abs/2007Natur.450..661R) on a number of occasions, but there is not yet firm proof of it. The nature of the storms on your planet will depend on the composition of the atmosphere and thus the composition of the clouds. Thunderstorms are likely to exist nonetheless.
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**Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers.
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You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49).
Closed 4 years ago.
[Improve this question](/posts/146816/edit)
### The story
The protagonist (whom will be referred with a first person narrative in this question) had a friend, Eve, who was a math genius. Eve was dying of cancer. She kept her mind occupied in her last days studying cryptography. As her condition got severe, she eventually managed to write a computer program that could extract the AES key by taking the plain and encrypted texts as its input. Meaning that she broke the AES. Let's assume the key length does not matter, but the encryption mode is [ECB](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_Codebook_(ECB)) and the program can crack the key in less than three minutes.
Eve died the next day. But before going to the ICU, she gave me her code and told me to run some tests. I am a sort of normal guy (not a genius) with moderate programming skills. I don't know much about network details or cryptography, but I'm familiar with the concepts and also a fast learner. I know that Eve's discovery is a huge breakthrough and I will honor her name... hmm... well, maybe later.
So, after giving some more thoughts I reckon that this code is basically a treasure and you know, Eve owed me some money. Let's see if she can return the favor at least.
### The problem
Now that I have decided to use this potential treasure, I have no idea where to start. Although the code is a giant leap for humanity, but it has limited capability in practice. Can I hack the banking system with it? I have no idea. This is the real world and I am not a magician like the one in the movies who types a few words and breaks into any camera system. I have almost zero knowledge about hacking and stuff. Yes I am a fast learner, but I have no idea what to learn. The biggest problem is, I want to work alone and don't intend to share this knowledge with anyone.
To make things worse, I also have a political agenda. I would like very much to hack into, say, the US government systems and do some wikileaks like stuff. Without getting caught of course.
### Question(s)
With this premise, is it possible to come up with a procedure for using this code to make money and expose some dirty secrets, while minimizing the chance of getting caught or exposing the AES vulnerabilities? By procedure I mean a step by step guide for the protagonist to maybe learn this and that, and whatever.
I am not even sure that this code has any actual worth other than its scientific value. It can only extract AES key, but there are still RSA and elliptic curves and other cryptographic schemes and I know that network protocols typically use a combination of these schemes. So, is it better to maybe sell this code to the highest bidder in the first place and forget about the political agenda? That would be very disappointing for the story of course.
I thought about posting this question on cryptoSE or securitySE, but since it has a fictional premise, I decided to post it here.
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AES is a symmetric cipher, but basically all systems use an asymmetric cipher to share the secret key for AES to ensure that this kind of break doesn't occur and so they can do authentication. Also, even if you do find some services to attack, people will pretty quickly catch on that the attacked sites are all using AES. This will just mean that the people who have been saying we need to switch to something more secure than AES will finally get people to cave. Also, if you steal a credit card with a man in the middle attack and immediately steal it, then the defenders might even see it takes about 2 minutes to work, then people may still use AES to secure transmissions they know take less than 1 minute. If you are buffering video in 2-minute intervals, You can get the key, send the message, then send a new key. By the time the attacker has cracked the key, the key has changed.
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**Beware the Black Helicopters**
In all likelihood, you'll be forcefully recruited to an unnamed government agency.
To use the ability to get rich means the taxman will want to know how you got rich. Once the taxman knows or can't tell, others will start looking.
The government (any government) will want the ability to spy on others including it's own people and the key to this is nobody knows they can do it. Once it gets out, a new encryption system will be used to stop the spying.
They'd black bag you, charge you with trumped up charges of stuff like cyber terrorism and force you to work for them or just steal everything and make you disappear or have a tragic bathroom slip and fall accident.
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I am working on a world which is very dark due to an opaque gas layer in the hight atmosphere; but it is opaque mostly in the terahertz range. The creatures in this world therefore rely very little on visible light. Some creatures have evolved sensitivity to radio waves (inspired by a handful of questions here in WB).
[This answer](https://worldbuilding.stackexchange.com/a/136679/21222) to [Best place on an humanoid body to develop biological radio?](https://worldbuilding.stackexchange.com/q/136545/21222) gives an example of a low-power, active radar device for short range that consumes 20 watts of power, which is about 0.86 kcal/hour. This may be prohibitive for smaller creatures (in the 1~5 kg of body mass, I think), so I wonder if passive radar could be used by them.
Could radio emissions from the planet's parent star, and gas giants in the same star system or other radio emission sources be reflected by the environment and perceived by such creatures, akin to how we can see by starlight?
I am not worried about the resolution of this kind of sight. I am more worried about whether radio emissions from space have enough energy to excite my aliens' radio-sensitive organs as much as starlight excites our retinal rods.
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I can't speak to the biological aspects, because we really don't have a good sense of how high of fidelity a biological radar can be. Signal quality is **everything**.
However, I can point to several very important things which suggest its plausibility:
* There are creatures which navigate by sound alone. In fact, *you* are capable of it... though you don't use the ability much while your eyes are open. Everybody hears the echoes of their shoes and map the world using the echos. Sound isn't the same as radar, but shares a lot of concepts.
* We have technologically derived missiles which use passive radar sensors, such as [HARM](https://en.wikipedia.org/wiki/AGM-88_HARM). So there is at least some prior art for using passive radar sensing as your only sense.
* There is something called Synthetic Aperture Radar (SAR), which lets one image using radar, the way a human eye or a camera images. So imaging can be done in the radar realm. Of course, SAR requires an active radar, so...
* For my final point, I'd just like to provide a picture. This picture was created using Very Long Baseline Interferomoetry (VLBI). It used passive radio sensors to image an object over 50 million light years away. So there... it can be done, in glorious manner. You all should recognize [the image](https://www.eso.org/public/usa/news/eso1907/) by now:
[](https://i.stack.imgur.com/Re6y4.jpg)
If they can image that, I think your biological creature stands a chance of imaging something closer!
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For context, this takes place about 300 years in the future. The space city in question is located in a nebula, completely man-made (not build upon any preexisting foundations like an asteroid etc.), densely populated and continually expanding, and possesses a surrounding force-field in order to create a habitable environment within. It is isolated from the control of any sole government and is established as a hub for interplanetary diplomacy. Thus, it needs to be mostly or completely self sufficient, but does receive shipments of outside goods.
What I would like to know is:
* would drawing and converting power from developing stars within the nebula be a feasible way to power the city
* are there any dangers presented by this location either to the city or the ships traveling back and forth
* what steps could be taken to minimize or protect against such dangers
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The densest nebulae are not much dense. [They usually have up to 105 particles per cm3](https://physics.stackexchange.com/a/26327/31264). For comparison, air is like 1019 particles for the same volume. Mars's own atmosphere is around 1017 range, I believe (1~2% of Earth atmosphere pressure when at the same temperature, mostly CO2).
If you were naked inside a nebula, you would be as good as exposed to hard vacuum.
You would have problems for objects going interstellar, which will have more wear damage than if they were going through space. 1 light year of nebula travel would be equivalent to many thousands of years of hard vacuum travel.
For energy harvest, if you are going to build dyson spehres around stars in a nebula, that wouldn't be different from stars outside nebulas. The stars' solar wind would push much of the nebula material away anyway. You will have a drop in efficiency if you beam up energy among stars, but if you have the technology to do that, you've probably reached a point where you can also make vacuum tunnels inside the nebula, which would remove the problem with ship wear damage too.
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Well, there are three different kinds of Nebulae: classical, Diffuse, and Planetary.
Nebulae themselves are made of different types of ionized gases and such. Dense places eventually form stars and some scientists believe the rest of the universal goop is used to build planets.
Also how Nebulae form is important. They can be created from an interstellar medium, stars, and supernova explosions.
Classical types include things such as dark nebulae and supernova remnant.
Diffuse Nebulae give off some radiation and moderate visible light.
Planetary Nebulae are stars that die and create a Nebulae, leaving a white Nebulae in the center (the original core star). Scientists say that when the sun dies it will create this.
The possibility of nuclear and radiation energy could be harnessed. The problem is in high amounts those things are usually deadly to most life in vast quantities. That would be an optimum power source but the world would either have to be outfitted to withstand nuclear radiation and other radiation (people, plants, and all). SO either they have been built to survive this or avoid all exposure with the outdoors (i.e wear thick clothing, live underground, live in buildings with thick walls).
<https://en.wikipedia.org/wiki/Nebula>
<https://itsadisaster.wordpress.com/2013/04/13/how-to-protect-yourself-from-nuclear-fallout-tips-about-radiation-building-expedient-shelter-et/>
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Larry Niven's "Known Universe" (KU) features "The Outsiders" as one of its most prominent alien races.
As per KU canon, the Outsiders evolved in a frigid moon (similar to Nereida) and they sustain themselves by generating electricity via thermal differentials, placing one part of their bodies in frigid darkness and another on a light source (thus creating a thermal differential). An "Outsider" is in essence a living [thermocouple](https://en.wikipedia.org/wiki/Thermoelectric_effect).
In an infinite universe everything is possible I guess, and in a fictional world, "my rules" rule.
However, I try to consider the feasibility of such an evolutionary approach. How could one put some rigor into the development and evolution of such an species, that it could lever such a metabolic approach to evolve not just life, not even complex life, but sentient life (which I'd think is a very metabolic intensive process.)
Any ideas how I (or one) would go about that? Suggestions?
Obviously, there'll be some hand waving and suspension of disbelief, but I'd like to see/use some hard science into this.
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**Intelligence comes from competition with conspecifics.**
Thermoelectric metabolism is OK. I envision something on a hot stone with cool water washing over it. It harnesses the transfer of heat energy thru its body. I bet there exist microbes like this in the deep earth where such niches are commonplace. They would not be culturable but their existence would have to be deduced by DNA sampling - evern then we would know they were different but might not know how they earned their livings.
Re big creatures: I could imagine a colonial mat which conducted this kind of metabolism, or a giant single cell like an algae with roots on the heat and fronds (here radiators) in the cool.
But smart creatures are hard to imagine for this lifesty;e. These things are basically plants. Once they find a good spot that will be a good spot for a long time. Plants don't need to be intelligent because the adult plants are not going to move.
If your creatures are going to move then intelligence might help. You don't need intelligence to move (amoebas move) but if your perception of time is on the same scale as your predators / competitors, intelligence might help figure out where to go. Maybe these creatures need to move from place to place to capitalize on shortlived sources of heat (or shortlived sources of cold). If they can figure out where to move next that might be a reason for intelligence.
Once you are moving to someplace good, you are trying to get there before your neighbor. **I think that you should have intelligence evolve thru conspecific competition**. That is why humans are intelligent - because we are descended from humans who outsmarted other humans, got all the good stuff, and had more babies. Your creatures get energy in a lazy way but they need to scrounge up whatever their bodies are made of which is not electricity. They need nutrients. Maybe they go looking for that and for mates. Maybe intelligence is attractive in a sex partner. That search and competition is where intelligence gave the ancestral organisms an advantage.
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Not a duplicate of [What software is available for map creation?](https://worldbuilding.stackexchange.com/questions/125/what-software-is-available-for-map-creation) as the focus is on *how*, not *what* -- requesting useful projections for a polar context, and techniques to transform between projections to achieve this.
I've created a simple earthlike planet for a Dnd campaign I'm running, and I wanted to minimize inhabited areas to keep things simple, so I put my continental plates on the poles. I also liked this idea since a lot of fantasy maps seem to completely avoid putting continents in areas where they are more distorted by map projections. However, I'm beginning to realize why. It doesn't look good projected with north at the top and south at the bottom because everything's totally warped. I want to re-project a rectangular map with the equator at the top and bottom so I can get a clear look at my continents. I can't figure out how to do this— I've got gplates, g.projector, and photoshop but nothing seems to rotate a raster on a globe. UV unwrapping in photoshop might be my best bet at this point, if anyone knows anything about that.
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For a polar centric solution it has to be an azimuthal projection, they would not normally be "square", it would not make sense (unless as a joke). Take a look at the United Nations Logo for a Whole World example <https://www.quora.com/What-are-polar-projection-maps-used-for>
There are many variations but a ["Lambert zenithal equal-area projection"](https://en.wikipedia.org/wiki/Lambert_azimuthal_equal-area_projection) for each hemisphere would in my humble opinion be best.
[](https://i.stack.imgur.com/q8ZMi.png)
Thus if using a map generator such as this one
<https://azgaar.github.io/Fantasy-Map-Generator/> you would need to use a square area and cookie cut in an editor to make it round.
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## Change the Aspect of Projection
As you are projecting the surface of one shape onto another, the aspect is how those shapes are oriented relative to each other. Most maps you see are cylindrical projections with a *normal* aspect -- the axis of the cylinder is the same as the planet's axis. But it can also be *transverse* (sideways) or *oblique* (anything in between). See [this Wikipedia section](https://en.wikipedia.org/wiki/Map_projection#Design_and_construction) for more info.
[](https://i.stack.imgur.com/n1gMP.png)
To get the equator at the top and bottom, you are looking for a **Transverse Cylindrical Projection**. For example, a [Transverse Mercator](https://en.wikipedia.org/wiki/Transverse_Mercator_projection) will do, but you can get the same effect with any other cylindrical projection if you just rotate your aspect first.
Those examples have curved longitude lines, but they don't necessarily have to. If the people of your world decided to draw their lines such that their East and West converge into points instead of their North and South, then all their gridlines would be square on a transverse map! However, curved lines might be necessary for timezones or compasses to make any sense... Oh and by the way, you can't show two poles without some equator between them, so notice that half of the equator is in the middle of the map.
But if your software doesn't let you change the aspect, just...
## Build Your Map Sideways!
You don't have to explain to the software what you're doing. Simply place the art for your polar continents on the sides of the globe instead of the top and bottom, and then rotate the projected map afterward. Or don't rotate it! Who am I to tell you which way is up! But if you do want curved longitude lines that converge at the poles, you'll have to manually draw them onto the globe in the map software, or add your own sine wave vector lines afterward.
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Basic idea: Primordial black hole (2.5% of Sun's mass) directly approaches Sun at fairly rapid pace (300 km/s).
Consequently, six days after passing Earth's orbit, it will collide with the Sun; accounting for additional gravitational acceleration as it approaches, the collision will result in many orders of magnitude more kinetic energy (~1E+40 J) dissipating into heat than the Sun radiates every second (3.828E+26 J), i.e. equivalent to about one million years of solar radiation.
How long would it take for this to make itself felt?
Will there be an instantaneous, GRB-like "flash" that scours Earth's surface of life? Or will it be concentrated in a few coronal mass ejections? Is luminosity going to build up over a period of minutes, hours, days, weeks, maybe even years? I assume most of the heat will be dissipated deep within the Sun, and it is going to need time to work its way up to the surface. When is it going to reach its peak?
Could at least people in deep bunkers survive that "flash"? Or will it basically scour away the surface of the planet.
(Idea is that the black hole is detected in advance and there is a race to build an Orion Drive powered colony ship. The ship lifts off just in time. Will anybody in ground control survive that flash? If so, how long before the world warms to such an extent that they die anyway? I would like to have people on Earth survive the initial flash and for as long as possible thereafter as scientifically plausible... but they do need to die in the end).
Thanks in advance.
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Well, what you are missing is the fact of how *tiny* such a black hole is. [Wikipedia](https://en.wikipedia.org/wiki/Black_hole#Physical_properties) says, a black hole with a weight of 10 suns is only 30km in diameter.
Also, you need to add the sun's escape velocity to the equation, which is 617.7km/s. So the black hole will hit the surface of the sun with roughly 686.7km/s.
The effect is, that the black hole will basically just punch away a cylinder of sun mass with a diameter of 30km, going all the way through the sun's core, and leaving on the other side. You need to realize that this cylinder of mass is *much lighter than the black hole that travels through it*. Thus, **the black hole will not loose enough speed to be captured within the sun, and it won't be able to eat the sun from within.**
The whole process is actually quite like a bullet hitting a box of marshmallows. The marshmallow box may be much more heavy than the bullet, but still the bullet will pass through relatively unhindered. And, just like the bullet is much more dense than the marshmallows, the black hole is much more dense than the sun. So, just like the bullet simply does not encounter enough marshmallows on its path through the box to stop it, the black hole does not encounter enough sun plasma on its path through the sun to hinder its progress significantly.
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Detour: Estimation of slowdown
The sun's core has a density of $\rho\approx150\frac{g}{cm^3}$. For simplicities sake, let's assume that the entire mass of the sun ($m\_s=1.99\cdot 10^{30}kg$) is confined within a sphere of this density. This results in a sphere with a radius of $r\_s=146819km$ (much too small, the sun has a radius of $696342km$, but we want an upper bound on the effect on the black hole).
The stellar mass that is on the path of the black hole of radius $r\_{bh}=15km$ would be
$$m\_{collision}=2r\_s\cdot\pi r\_{bh}^2\cdot\rho$$
$$=207560185km^3\cdot\rho$$
$$=3.11\cdot10^{22}kg$$
$$=0.0000000157m\_s$$
Setting this into relation with the mass of your black hole ($m\_{bh}=0.025m\_s$), we can compute the speed that results from the fully inelastic collision between that mass and the black hole:
$$v\_{bh}\cdot m\_{bh}=v\_{out}\cdot (m\_{bh} + m\_{collision})$$
$$\Leftrightarrow v\_{out}=v\_{bh}\frac{m\_{bh}}{m\_{bh} + m\_{collision}}$$
$$=686.7\frac{km}{s}\cdot\frac{0.025m\_s}{0.0250000157m\_s}$$
$$\approx686.7\frac{km}{s}$$
Looks like my analogy with the bullet and the marshmallows was totally off. It's more like an anti-tank bullet going through a box of fluffy cotton wool...
And that's even with the assumption that the sun were core-only, the real mass distribution would lead to even less of an effect...
The point is, the stellar mass that the black hole interacts with is just way too small for any appreciable effect.
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Of course, you must expect some hard gamma radiation when the black hole enters the sun, and some more when it leaves on the other side. But those ray bursts will be tiny in comparison to the 150 million kilometers, so I doubt that they will be strong enough to be catastrophic. I may be mistaken on that one, though, as I can't do the math on this.
So, sorry, the apocalypse won't happen that way...
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If a black hole "collides" with your sun not much energy is dispersed. Maybe a little escapes but, beyond the event horizon, nothing gets out of the black hole, and your planet is now orbiting a black blob of sheer gravity and probably falling inward slowly, but yes people could survive this.
People don't seem to think this is helpful, so I will provide some of my knowledge that might be useful. Due to the reaction to my answer I assume you already are set on having an explosion of some sort.
It might help to know that nothing (aside from things affected by quantum occurrences) can travel faster than light, **approx** 830,000 miles per second. Not an exact, but I do know earth is 8 light minutes from the sun on average so the people on the planet would have **at least** 8 minutes to find a solution
And not to rain on this parade but I must say that something of any less mass of the sun really shouldn't be considered a black hole. But this is for abother discussion.
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Simple question that might seem odd. Not going to get too specific but I am curious, more or less, as to what it would look like for a planet that had a moon (A habital one) which was in essence tidally-locked to the star of the system. In addition, just how probable/possible is that, really?
It orbits its planet as any satellite does but isn't tidally locked to it. Instead its spin in relation to its own orbit around the planet (and its own orbit of the sun) causes it to always have the same side facing the sun. I assume this would cause for habitual, essentially daily eclipses for the side in eternal day (Almost equating to its own equivalent of a "night") but I can't find what else that might entail.
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Tidal lock happens when the tidal forces, exerting a momentum on a body, synchronize its rotation around its axis with the revolution around the main body.
Since for a moon-planet-star system the forces exerted by the planet will always be greater than those exerted by the star, there is no way for the moon to be tidally locked with the star and not with the planet.
The only case in which the tidal forces generated by the star are stronger than those generated by the planet implies that the moon is orbiting the star and not the planet.
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For this to happen, the moon would have to be tide locked to the planet while the planet itself is tide locked to the star.
Notice that surface exposed to the star will vary slightly throughout the year due to axial tilts and also a movement called libration.
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I'm trying to create my planet orbiting a red dwarf, honestly I've thought other scenarios but it's like every answer opens new questions. I'll just say what I want my planet to be and I'd like your help(please) to understand how it would work.
I'm new with worldbuilding(started yesterday), so bear with my lack of knowledge, if you don't want to use your time answering, I'd like research sources too.
I want the flora to be mainly black, so the sunlight has to be somewhat weaker, which would make the planet(or the habitable zone) fairly cold.
The planet being tidally locked seems to be the common, and I don't mind, apparently the habitable zone would be the ring around the planet between the parts that do and don't face the star, but I don't know if such a thing is entirely possible, what are the complications the inhabitants of such a planet face?
Apparently it *doesn't* have to be tidally locked, but I didn't understand how that works, apparently it would have to have some kind of moon orbiting around it?
If you want to show off your knowledge and tell me how the sky would appear...I'll be impressed.
If it needs something unlikely to happen for desired situations I don't mind either, the planet was somewhat "made" by "gods".
Yes, sorry, I don't know much, whoever gives the time to answer, know that I'm grateful.
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Welcome to Worldbuilding!
First, the planet itself **does not** need to be tidally locked. **Either scenario is plausible.** It depends on the history of the planet's formation. Even Mercury itself isn't tidally locked. So, it's up to you.
If you do decide you want your planet to be tidally locked, then:
* It can have a moon, but the orbit of said moon would be at risk of destabilizing over a very, *very* long period of time. Eventually it could fall into the planet, opposite of what is happening with our own moon right now. (Potential plot point?)
* The climate of a tidally-locked planet's habitable zone may be [wildly unstable](https://www.space.com/13950-habitable-alien-planets-tidal-lock-life.html). However, this mainly depends on a) the composition of the atmosphere and surface rock, and b) the surface conditions at the subsolar point, especially vis-a-vis liquid water. I can elaborate on this with more information on your planet's environment.
As far as size goes (regardless of whether it's tidally locked), the planet can be very small, like Mercury, or several times larger than the Earth. Again, it's up to you. Scientists have found *massive* rocky planets closer to their parent stars than the Earth is to the Sun. [Here's a recently discovered example](https://phys.org/news/2018-11-astronomers-super-earth-barnard-star.html) of one such planet.
As for the flora: [According to this source](https://news.nationalgeographic.com/news/2011/04/110419-alien-trees-black-plants-planets-ras-space-science/), you might expect the color of flora to naturally appear "red, blue, yellow, purple, or even grayish-black." Interestingly, that article mainly discusses planets orbiting binary stars, postulating their flora might appear black to us. In any case, it depends on the amount of light the plants receive and their chemical make-up. I would wager that dark-ish blue, purple, and gray colors would be more than acceptable, though I would recommend against having one single uniform color throughout the entire world. (Keep in mind the vast variety of plant life colors here on Earth, for comparison.)
Finally, the appearance of the sky depends on a lot of things, including (but not limited to) the composition of the gases in the atmosphere, dust in the air, distance from the star, etc. I'll gladly edit my answer if you provide more details in your question. Or, if you already have in mind a particular way you want the sky to look, I can attempt to give you conditions that might produce it.
[Answer]
"What are the complications the inhabitants of such a planet face?"
Well, since the planet is tidally locked (and as long as it's been so for at least thousands of years), the sunny side would likely experience tropical temperatures year-round, or even hotter. and would be mostly overtaken by an ocean with small archipelagos scattered around.
The vegetation on a brighter side might evolve to be whiter, as it doesn't require that much sun to grow and thus needs to bounce some away. The opposite could be true for the dark side, although plants would likely not even exist at all and might be completely overtaken by a massive ice sheet.
Since there are virtually no seasons or things of the like, animals wouldn't migrate, weather would be extremely predictable, and farms would be widespread and easy to grow. Life on the bright side would evolve quickly, while those on the dark side would likely die out quickly.
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"Apparently it doesn't have to be tidally locked, but I didn't understand how that works, apparently it would have to have some kind of moon orbiting around it?"
I can't really see how that'd be true. Since the planet would have to be really close to the red dwarf (since the star is small and thus has a closer habitable zone), the tidal forces acting on the planet would be much stronger than Earth's and would pretty much force it into being tidally locked.
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"If you want to show off your knowledge and tell me how the sky would appear...I'll be impressed."
The appearance of the sky essentially depends on how dense the planet's atmosphere is. Earth's is blue because of the high amounts of gases. The gas particles completely absorb most short-wavelength colors, like blue, which scatters them (basically radiating blue out in all directions from the particle). Since blue is one of the most scattered colors, the sky appears blue because blue light is constantly hitting the gas particles.
It could also depend on the range of colors emitted by the star. The Sun would appear white if you were to be suspended in space without the atmosphere to color it, and so it emits virtually all light on the color spectrum. If the star emits only reds and oranges, the atmosphere would be predisposed to being in that range.
I don't know how dense your planet's atmosphere is, but the less dense it is, the darker and fainter it would be. Since it orbits a red dwarf, the sky would likely be orange or even yellow.
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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.
Now that FTL travel is here there are all sorts of family outings we can go on.
One of these is a scale model solar system lovingly made by hobbyist Barty Slartfast.
**In full scale**
*Sedna is three times farther away from Earth than Pluto, making it the most distant observable object known in the solar system. It is 143.73 billion km from the Sun, thus giving the Solar System a diameter of 287.46 billion km. It is 143.73 billion km from the Sun, thus giving the Solar System a diameter of 287.46 billion km.* <https://www.universetoday.com/15585/diameter-of-the-solar-system/>
**The scale model**
Barty scaled it down by a billion. He made sure that all distances and diameters are in proportion to the real thing
The masses of the solar bodies are in proportion to those of the real ones. (but not necessarily scaled by the same factor as the distances)
**To be determined**
We've divided distances by a billion, how much should we scale down the masses of the mini-planets to make it all work (or doesn't it matter because we can also adjust orbital velocity)?
The planetary spins can be adjusted if this is necessary. He doesn't intend to have atmospheres, liquids or even tidal effects. Just solid bodies.
**Question**
Ignoring gravitational disturbances from tourists, can we make such a scaled down solar system that will be held together by gravity once the initial velocities and all other parameters have been set correctly?
**Bonus question**
It would be nice for tourists if the Little Earth year could be about an hour. Can this be done simply by adjusting the masses and orbital velocities?
[Answer]
Okay. My initial answer is *completely* wrong. Took a friend with a stronger grasp of Newtonian mechanics to set my head right. Holding densities the same, in a place where spacetime is nearly completely flat, proportional reduction across the board will work absolutely fine.
This does mean that the masses are scaled by the cube of the distance scaling, but that actually results in all the appropriate values being neatly cancelled. Kepler's 3rd law can be expressed as
$T = \sqrt{\frac{R^3}{M}}$, and since $R$ is being decreased by ${10^{-9}}$ and ${M}$ by $10^{-27}$, it all comes out even.
The problem with the *visibility* of the elements of the solar system, given the ratio between their diameters and the vast distances between them, remains a barrier to this being an easily-taken-in tourist attraction.
(For the bonus, in order to speed up the earth while keeping its orbital distance correct, you'd have to radically increase the mass of the *sun*, which would have a similar effect on the entire system.)
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***Preserving my original answer so others can learn from my mistakes!***
The scale of your scale model is dependent on *which* properties are being scaled. Gravity is a result of the product of the two masses and inversely proportional to the square of the distance between them. If all dimensions are being reduced by the same constant, the masses of all the components of the scale model will be reduced by the cube of the reduction.
By means of explanation:
$F=G\frac{{m\_1}{m\_2}}{{r^2}}$
is the equation for gravitation. Assuming density is held constant, $m\_1$ and $m\_2$ both have their masses reduced by the cube, because
$V\_{sphere}=4/3 {\pi} {r^3}$
So the reduction in mass, assuming, again, that density is consistent, is $1\*{10^{-9}}^{-3}$.
Meanwhile, the orbital velocity equation is
$v = \sqrt{\frac{GM}{R}}$
$G$ is the gravitational constant, $M$ is the mass of the system (in the case where one object is substantially more massive than the other, generally just the "central" object of the orbit), and $R$ is the orbital radius. $R$ has decreased by a factor of a billion, while $M$ has decreased by a factor of an *octillion*. Even though v also needs to decrease a billionfold, accounting for the root, a factor of a billion is still missing.
This means that everything in the scale model will have to be ten thousand times as dense to compensate... and given that Earth is currently 5.51g/cm^3, you're running into special material problems. The densest material on earth, Osmium, tops out at ~23g/cm^3, which is still orders of magnitude less dense than our rocky planets have to be.
Assuming you have access to some manner of degenerate matter that has the appropriate density, you still can't arbitrarily reduce the orbital period of any given component of the Mini System(tm). Orbital period is [defined by the masses of both elements of the system and the distance between them](https://en.wikipedia.org/wiki/Orbital_period), so you'll be screwing up your scale model by dramatically reducing the orbit diameter of the Earth.
On top of all this, your model earth, at one-billionth scale, would be a marble 1.2cm in diameter. Not so much fun for the kiddies when it's lost in the ~150m between it and the beach-ball-sized super-dense sun.
It's a hobby project, but even if you have access to strange materials from which to assemble your planets, it's not going to be much to look at.
*Edit: Just noticed an important detail in your bonus question - orbital velocity is a function of mass and distance, and cannot be adjusted independent of them.*
*Edit the second: It should also be noted that you'd also need a way to keep the matter in whatever state hits the correct density for your project. "Naturally occuring" degenerate matter is in dead stars where the crushing gravity keeps it in what is ordinarily a deeply unnatural state. With that in mind, if you can manage that trick, you could presumably manipulate everything in the Mini System to behave however you want. But then it wouldn't be hanging together "naturally".*
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My planet is very Earth-like with a day length of 26.87h. The moon has a radius of about 1550km, a mass of $5.2\times10^{22}$ kg and orbit 45500 km from the center of planet.
My scenario is that the formation of this moon is the same as our Moon (i.e. from a collision) but that the planet was spinning slower so they would be both totally locked to each other, thus the moon wouldn't slow down and move away, staying in a geostationary orbit.
Is this realistic? Would it have an effect on plate tectonics, and what other effect on the shape of my planet would it have?
Note: I'm not asking for climate, only the things above
[Answer]
**It is possible.**
First, you did the math correctly, a center-to-center distance of 45500 km would result in geosynchronous orbit assume mass = 1 earth.This is well beyond the Roche Limit, so you bodies are stable.
Whether this could happen is entirely dependent upon how fast the rotations were at the initial conditions. For our Earth and moon, the initial conditions result in a mutual tidal lock in about another 50 billion years -- though the expected red-giant phase of the sun may make this a moot point.
Certainly Venus is spinning much slower than Earth even though the planets are very similar in other ways. So there is clearly great variety in initial conditions and/and events history to get us to this point in time. Your system is certainly within the realm of the possible.
Since your planet is mutually locked with your moon, there is actually less tidal stress since the moon is always in the same place in the sky. Your planet would be stretched a little more in the moon direction because the planet would have time to fully adjust -- but this does not mean more strain. Earth's bulge due to this rotation is many times larger than a tidal bulge, but the important factor is not how non-spherical it is, but how strain is induced because of this regular orbital cycle.
Your planet's tidal strain would be only that of the sun, which presumably would be similar to Earth. On Earth, solar tidal force is about 46% of the lunar tidal force. So, still some tidal strain, but only about one-third as much as on Earth (tidal forces are additive).
The difference in Planetary shape due to tidal locking is negligible on Earth (only about 1 meter in the deep ocean). However, since the tidal force in your case is based on a moon 0.71 times the moons mass, but 8.4 times closer you should expect a permanent tidal bulge of about 428 meters in deep ocean but less over land (rock is heavier than water). That may sound like a lot, but you would never notice it without good instrumentation.
If you want tidal strain, it is easily accomplished. Just make the moon's orbit eccentric. Because your moon is so close, the tidal effects are magnified considerably. Our moon varies from 363,104 to 405,696 km., a bit over 10% variation. Because tides are proportional to distance cubed, a 10% variation results in a 33.1% variation in tidal force. This would result in very significant tidal stress, large ocean tides, etc. The local residents would definitely notice these tides and would be able to correlate them to apparent changes in the moon diameter.
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Chronopolis is a city built on modern time-technology ("chronology") and is split into three sectors, slowtown, midtown, and fasttown, whose residents function at 1/2, 1, and 2 times natural speed, respectively. This is enforced by a grid of street-clocks which "balance" time between people in slowtown and fasttown. (The "clocks" only affect people, not animals or inanimate objects, so for instance, things seem to fall twice as fast in slowtown and half as fast in fasttown.) The basic law is that the total subjective time of all consciousnesses is conserved. Thus the population of fasttown is kept at around half the population of slowtown, because it takes two people running at half-speed to balance out one person running at twice the speed (2\*(1/2)+1\*2=3). Everyone still has the same subjective lifespan (so other factors being equal, a fasttowner lives for half the time of a midtowner).
It costs a large amount of money to just live in fasttown. Fasttown is the center of commerce, media, and politics, while slowtown is poorer, home to criminals and undesirables, with few jobs or opportunities.
What kinds of jobs benefit from being in fasttown? Why would they benefit from running at 2+ times the speed of the rest of the world? What would the economic makeup of fasttown look like?
Concretely, I have that the government is based in fasttown, as is scientific research (in particular, research on chronology). What do the rest of the 1 million+ residents do?
The level of technology is that of the first half of the 20th century (but this is flexible).
**Notes**:
* There's an interesting question of whether things would feel heavier, be harder to move, etc. in fasttown because only people are affected by the speedups. I am ok either way (but I definitely don't want gravity to feel different in the different sectors).
[Answer]
If we ignore the inconsistencies around material interactions, include transfer of heat etc... then any manual manufacturing tasks are going to benefit from a temporally accelerated reference frame as artisans will be able to produce more goods in the same time period as seen from midtown, effectively doubling their daily output at the expense of their absolute lifespan.
Even if heat transfer is problematic for blacksmiths there are still advantages since an individual can work on more pieces simultaneously if their actions are accelerated compared to the heating of their work pieces.
The big issue is that raw materials brought in from outside, particularly wood in the form of charcoal for early smelting techniques and ongoing forging, or willow for basket making, oak for ship building etc... isn't going to replenish fast enough compared to the rate at which it is consumed by fasttown's workshops to be anything like sustainable. There were enough problems with deforestation from ship building and blast furnaces when we were moving at our usual speed.
[Answer]
Anything that involves interactions between people. A teacher, for example would educate more classes in a midtown day by moving to fasttown. Therapists, prostitutes, architects, philosophers, some scientific studies - anyone who has an intangible product that is limited by talk and thought and action being slow processes, and not by materials or infrastructure.
[Answer]
Manufacturing would benefit from life in the fast lane. The invention of the assembly line streamlined the process, but everyone being able to move twice normal speed would also help. Cars, clothes, watches. Anything that is built by people would benefit from people moving twice as fast.
Agriculture would be another prime industry for Fasttown. If plants grow twice as fast, food could be produced in climate controlled greenhouses to eliminate issues with seasons. Being able to produce food year round at an accelerated rate would allow Fasttown to potentially produce enough food for all of Chronopolis.
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My planet - let's call it Penumbra for now - exists at roughly 1.5 AU from it's sun - which was similar to Earth's - but is about a billion years older.
It is 15% more massive than Earth, but nearly identical in size.
It has around 85% of the atmospheric pressure.
It has an axial tilt of 13.5 degrees +/- 2 degrees, giving it minor seasonal changes.
Its rotation is equivalent to 40 hours, and its orbit is 450 of their days.
In the distant past the planet and solar system were home to a very advanced nonhuman race. As their planet underwent runaway greenhouse effects and their star began heating up, [they built a large space construct at the L1 point - a magnetically stabilized plasma mirror](https://worldbuilding.stackexchange.com/questions/116139/what-mechanism-could-be-used-to-create-an-eternal-night/116142#116142) with a frequency tuned to reflect all light above indigo-violet – designed to cool their planet. It was built to be fully automated and self-repairing. It’s powered by a ring of solar stations and has arrays capable of beaming light to Penumbra. Currently, they are tuned to emit infrared and ultraviolet light at levels necessary to maintain preset environmental conditions on the planet’s surface.
Due to this, the day/night cycle at the equator is roughly 18 hours of Truenight, 6 hours of Zenith, 10 hours of Falsenight, and 6 hours of Apogee. Zenith and Apogee are the periods where the Sun is not blocked entirely by the Mirror – Falsenight is when the mirror is blocking most or all sunlight and only ultraviolet/violet/indigo/infrared light is reaching the surface.
The race that set this up was also capable of modifying wholly or in part most species of plants, so plants that do most of their photosynthesizing during the 6 hour periods of light or have been modified to utilize UV/indigo.
**Question:** Given the fiction of the plasma mirror, is this planet as described realistic?
* Do not consider moons as I haven't settled on what moon(s) the planet would have.
[Answer]
The orbital period is about right, although to long by about 10%. The deviation is totally within the reasonable allowance of the question. Cudos to you, OP, for doing your homework.
>
> Actually, in the interests of full disclosure motivated by not wanting to seem too much of a nit-picker, when I first did the calculation (badly) I got a larger error. This led me into trying to write a proper answer, formatted with the Latex package. In doing so, I found my error, but the Latex was so much fun that I'm leaving this answer.
>
>
>
The proposed star is similar to Earth's sun. Let's assume that it is of the same mass.
According to Kepler's Third Law of planetary motion as found [in the online Encyclopedia Britannica](https://www.britannica.com/science/Keplers-laws-of-planetary-motion), "The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun." The stated distance is about 1.5 AU. The stated year is 450 local days, which are each of 40 Earth hours. The arithmetic says that:
$$
Year\_{Penumbra} = ((40 EH)/(24 EH/1 ED)) \* (450 PD/1 PY/(365 ED/1 EY))
$$
Where:
* ED is Earth Day
* EH is Earth Hour
* EY is Earth Year
* PD is Penumbra Day
* PY is Penumbra Year
This gives:
$$
1 Year\_{Penumbra} = (40/24)\*(450/365) = 2.05 EY
$$
By Kepler's Third Law of Planetary Motion, the ration of the Penumbra orbit to Earth's orbit should be:
$$
\sqrt(1.5^3) = 1.837 EY \\
which\ is < 2.05 EY
$$
I am curious about one other aspect that I find unrealistic because of [path dependency](https://en.wikipedia.org/wiki/Path_dependence) in technology development. It feels unnatural, and thus less believable, to have the photosynthetic system of the plants be altered to match the shorter, shielded day rather than continue to match the original day cycle. I would hope to see some reason in the story that describes the reason for and perhaps the difficulty of achieving so great a change.
Many things in the plants would need to change for an optimized organism:
1. Every pathway involved in the circadian cycles would need to be changed. We are finding that these are complex oscillators involving many genes and regulatory agents.
2. The day-night cycle runs with a different rhythm. To the plants, there is one longer and one shorter night. This would best be done by adding an epicycle to the circadian system, which could be difficult de-novo bioengineering.
3. The local stores for inputs and outputs could be smaller. Photosynthesis produces energy when the sun shines, and that energy is stored for when the sun is not shining. Less storage would be required.
4. Heliotrope is the process of tracking the sun. If the sun appears to be moving faster in the sky, the rate of movement would need to he larger with structural adaptations necessary.
I hope to read your stories from this world.
[Answer]
I would think your scenario is very realistic. The points I would question are:
1. Density: 15% more mass than earth on same size. Earth is already the planet with highest density in our solar sytem. A rocky planet with a large iron core. I found this on the internet: <https://www.universetoday.com/36935/density-of-the-planets/>
It is hard to tell how realistic it is to find a planet with an even larger iron core.
2. Beaming light to the planet: I think for realistic reduction of a runaway greenhouse effect, there would not be a light beam behind the structure, but rather just size the structure down or include holes (with UV filters?) that let some light through.
3. Mirror lifetime. I think placing it at L1 is totally realistic. Considering pressure from the light phontons, this could easily be compensated by moving a little more toward the sun. Assuming a sufficiently advanced space-travelling civilization, auto-repairing might also work.
I would be concerned about micrometeoroids. Micrometeoroids will constantly hit and do their damage over time. See Wikipedia on 'Micrometoroid'. So I would doubt that a self-repair could keep up with this for so long. Once the station-keeping fails, an object will leave L1 soon and fall into some sun orbit.
It could be that the propulsion and robot-base is in a very robust think housing, and that the mirror frame is a large and light structure, that just sustains the holes of meteoroids without falling apart. After the long time it would be riddled with holes up to the point of looking like a naked skeleton.
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I am trying to develop an alien species that could live on Titan and at first I supposed it would be easy with the species being able to use yellow, red and near-infrared wavelengths of light to see.
But then realised that the windows in Titan's atmosphere aren't as conveniently placed as those of Earth's and that blind spots could be caused by the absorption lines of certain chemicals, the most annoying absorption lines being those of the liquid on Titan's surface.
My question is if there is a window for both Titan's atmosphere and Titan's liquid? Would this result in a liquid with an appearance similar to water to our eyes or result in a liquid that would appear almost opaque?
A world where "water" is opaque sounds like an fascinating story writing opportunity due to how terrifying it is as a concept but I have no idea what liquid methane/ethane is like.
[](https://i.stack.imgur.com/nJCOD.jpg)
Also, if the liquid is opaque how does it effect a creature's ability to see at all since most eyes contain liquids. Would I have to copy the rattlesnake solution to the problem of infrared and also how would a creature's eyes (or some other vision apparatus) need to change to see near infra-red?
[Answer]
There are three ideas we need to deal with: absorbance, transmittance, and reflection. ([good starting point here](https://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/beers1.htm).) Let's think of fluids approaching a strainer.
* **Absorabance** is a measurement of how much the strainer will capture and hold (light won't pass through it, but it won't reflect off of it, either).
* **Transmittance** is a measurement of how well the strainer lets things pass (light passes through the material without stopping).
* **Reflection** is a measurement of how well stuff will bounce off the strainer (light bounces off the material).
*I'm also fond of the cherry analogy. Somebody throws a cherry at you. Did you duck, letting the cherry pass by (transmittance), catch the cherry in your mouth and swallow (absorbance), or catch it and spit out the seed (reflection)? Don't laugh, metaphors are rarely perfect.*
Simplistically, water and glass have high transittance, low absorbance, and little reflection when looked at straight on. (Change your angle of view, though... now all the physics about light transitioning between mediums kicks in).
A common green leaf has high absorbance of red wavelengths, high reflectance of blue and green wavelengths, and low to no transmittance. Which means you see green, don't see red, and the ground beneath the leaf is dark.
**Water's absorbance of IR is very good**
[Water aborbs IR](https://chemistry.stackexchange.com/questions/55625/use-of-water-in-ir-spectroscopy/55630#55630). No reflection, no IR on the bottom of the pool, it's opaque.
*Before I continue, remember to separate "how we see it" from "how it would be seen." We "see" the green reflected from a leaf, so it looks opaque (and green). We don't see the red absorbed by the leaf so it's "invisible" (meaning, it doesn't look red, if only looking in the red spectrum, it would look black).*
*It's helpful when dealing with aliens to think of what they "see" in their spectrum being symbolically identical to what we "see" in our spectrum. The short wavelength is blue, the medium wavelength is green, the long wavelength is red. They would symbolically (or perceptually) have the same kind of differentiation. What we'd call red they'd call blue and what we can't see they'd call red.*
Why is this important? If you chase that "water absorbs IR" link you'll see that the deeper you go into IR, the less absorbant and more transmittant water becomes.
Which means, to a denizen of Titan (I believe there's enough of the IR spectrum there to do this, correct me if I'm wrong), a gently undulating surface of water would look remarkably like a lake full of low viscosity tar or oil would to us — black with bright reflections at the longer wavelengths.
As for the atmosphere, depending on what's actually in it (good point DarthDonut), they might see fog were we see clearly. They'll see clouds just like we do, but what's *causing* the clouds is a very different matter.
[Answer]
JBH's answer is excellent, so this is more of an adjunct to it than a totally separate answer.
There are organisms on Earth that have very interesting vision, including in the IR spectrum. I'm thinking mainly of [Mantis shrimp](https://en.wikipedia.org/wiki/Mantis_shrimp#Eyes), who have all sorts of options for seeing things. As JBH's answer points out, vision (in the general sense of the word) depends on what light actually makes it into the eye, and so the chemical absorption is less important than the absolute amount of light that is present to "see", through any mechanism. The major issue would be sensitivity to differences in wavelength, so that differences in shade could be determined.
So the darker the environment, the less likely "eyes" are to be well formed, or even present. Compare with the deep sea or deep cave complexes on Earth, where eyeless creatures abound.
Depending on your interests and needs, you can also be looser with "vision". Echolocation can give a solid impression of the precise dimensions of physical objects in 3-dimensional space, though color becomes irrelevant in that case.
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While pondering "[Can radioactive moon affect life on a planet?](https://worldbuilding.stackexchange.com/questions/103721/can-radioactive-moon-affect-life-on-a-planet)", I got to wondering about *plants that send out a tight beam of ionizing radiation*. **What kind of evolutionary pressure might lead to such a design?**
The only thing I have been able to come up with is that somehow there is no other way to lose heat effectively, but this only raises more questions.
[Answer]
A bioluminescent ground foliage used light to attract high-altitude flying pollinators.
Slowly, taller plants began to cover the glowing flowers. This caused only the brightest to reproduce.
As the canopy got higher and thicker, some of the flowers evolved to focus their light into a beam they shined upward to have more success getting their light to penetrate the canopy.
As the canopy got higher and thicker, the flowers got brighter and more focused, until, some of the flowers just snapped and started blasting holes through the canopy.
[Answer]
I'm going to note here that this is pure speculation; more of a creative answer based on science than the creative application of science.
That said; plants generally want all the heat they can get, within reason. That's because photosynthesis is an endothermic reaction, requiring energy to convert CO2 and Water to CHO (carbohydrate) compounds and O2. Initially, plants do this for themselves but as we know, they produce more carbohydrates and oxygen gas than they need. The O2 is 'corrosive' to the plant so instead of trying to contain it, they just release it into the atmosphere. This is the very reason that animals can exist; all animal life is effectively parasitic in that it relies on plants for both O2 and food. Even Carnivores have herbivores down at the bottom of their food chains.
So; imagine that instead of releasing excess O2, plants 'decide' to release the excess energy instead. What we're talking about here is the ability to suspend photosynthesis when the O2 and CHO compound needs are met.
The problem with this scenario is that it's not sunny all the time, and temperatures change through the year, etc. Plants with non-continuous photosynthesis may develop limited capacity to store O2 (carbs are less of a problem for a plant, just take a look at fruit) so that they can metabolise energy when neeeded, but ultimately plants would *still* want as large a surface area as possible facing the sun so that during winter (for example) they can still survive. During summer, they have to dissipate the excess energy so as not to overproduce their O2 and carbohydrate holdings.
In such a case, it seems like a *possible* solution that they could radiate. Why the tight beam? Ultimately, like any living organism, they don't want their entire body to get hot, especially during summer when the ambient heat is only going to exacerbate their problem. It seems logical that emitting a tight beam of radiation would allow them to dissipate the energy they're absorbing from the environment in an efficient way that gets the heat away from them as much as possible.
Now for the caveats;
If the entire planet of plants has developed this method of controlling photosynthesis, you don't have animals. This is because you don't have O2 in the atmosphere. Sure, some traces would be released if the plant dies for instance, but those amounts could easily be bound to iron in the rocks, etc.
This is a more complex form of plant life with several more regulatory systems than Earth plants have. Plants are unlikely to go to this trouble (evolutionary speaking) unless there's a reason to do so, and off the top of my head I can't think of one. Certainly storing O2 for overnight and cold / cloudy days seems like a lot of trouble when you have a massive container around you called the atmosphere.
Forest canopies *may* look very different. If the plants on the forest or jungle floor start emitting upwards for instance, I don't know how much of an impact that may have on the tree canopies above them. Forest and Jungle ecosystems would probably look very different in such a world.
Finally, the radiation burst would only happen in specific conditions; it's not a constant stream of energy as it's only happening when there is excess energy to dissipate. You'd get all your radiation bursts during hot days, probably when you least want them. Also, given the amount of energy we're talking about, this is probably not a very dangerous burst to (say) human life.
Ultimately, this is a feature that is unlikely to evolve alongside conventional plants because of the evolutionary complexity, meaning that you're looking at a very alien world to develop such a feature. One that's not very friendly to animal life.
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My fantasy world consists of a flat plane, with the sun affixed to a point directly over the main continent. This sun powers down to create night conditions, and then powers up again in the morning. Given that it will never change its position in the sky, what are some likely ways this environment will differ from our own?
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The ecosystem on tree trunks will be remarkable. Moss (and perhaps lichens) will grow in two vertical bands (where they have some light but are not too blazed by the sun.). There may be fungi that grow in the dark on the far side of the tree, and perhaps up the trunk a bit (though that may not be true at all if the tree is healthy.) The leaves on the tree will be smaller and more curled towards the sun and broader and more flat in the shade. (Assuming an average climate.)
There will be effects on lakes. Assuming average rainfall throughout your world, those on the sunny sides of the mountains will evaporate more quickly than those on the shady side.
I hope these ideas are useful. Enjoy thinking about the small denizens of your world.
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You would have absolutely no seasons whatsoever, and thus - depending on the output of your star - either a lush evergreen jungle or a desert, or anything in between, but no changing environment that has different behavior depending on seasons.
Also, lack of moonlight being reflected means pitch dark nights, which would influence predators. Better night vision is necessary, while other species might prefer to stay in sheltered locations during the night. Fire (or another light source) will be *very* important for an intelligent species that does not have night vision.
Sun dials as clocks will not be possible, so time has to be kept track of in another way. Similarly, animals need to have some kind of "sixth sense" to tell time and to go to shelter in time. How they do that without any apparent way to tell the time? No idea, honestly.
Plantlife would probably develop differently, since trees will now completely block the light. So no plants underneath trees anymore (with a rising/setting sun, those get at least *some* sunlight, if the sun is fixed, they do not).
For an intelligent species, navigation would be difficult without a way to tell cardinal directions by watching the sun.
There will be lots of small but noticeable differences, listing them all would prove futile.
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Due to the Earth being a sphere, the equator gets direct sunlight while the arctic regions see the sunlight from an angle. On a flat world, I would suspect the amount of energy the Earth is receiving would be pretty uniform across the entire landmass. From that point of view, I don't believe you would get an arctic/antarctic forming and instead have much more uniform conditions north to south. Instead of latitude being the big difference maker, Albedo becomes the major differences in terms of temperature (IE the ocean absorbs most of the suns rays while land tends to reflect it more).
Much of weather is ultimately the uneven heating of the globe...with more uniform heating/cooling, one would expect weather patterns to be weaker and as such more erratic. To compound this, much of weather patterns is heavily effected by the rotation of the globe...without a rotation, the weather would be even more erratic day to day. I'd expect local thunderstorms (sun heats up land, evaporates huge amounts of water, and drops it in a storm) is going to be the may stay of your weather patterns.
The planet will lack a tide as well, which will have an impact on some parts of life and it's hard to speculate on what ocean currents (if any) will come from this (earths currents are heavily effected by the waters warming at the equator and cooling at the poles...would that happen on a flat world with a fixed sun?). Air currents on Earth transports clouds (ultimately rain) from over the ocean to land...would this flat world see that or will all the oceans evaporated rain simply dump back into the ocean?...if that's true you would see a lot of the inner landmass as desert as no air currents exist to bring the rain clouds over.
Oddly enough, from a climate point of view, the flat planet plus no rotation actually has a heavier impact on the environment than the fixed sun position.
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**The difference probably wouldn't be huge.** I'm assuming that things like gravity and atmosphere function the same way in your world as they do in ours. The only actual difference would be that the light in your would always comes from the same direction.
Do keep in mind that you will also have to create some sort of moon or other method of creating light during nighttime, unless you want it to be completely dark (which would greatly impact the environment).
That being said, the only changes would be some very specific things, like sunflowers or similar plants, which would always face in the same direction.
Overall there would be no major difference.
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In [this](https://worldbuilding.stackexchange.com/questions/102489/how-big-would-a-satellite-need-to-be-to-block-out-the-sun) recently asked question on a large, sun blocking object it is pointed out in the comments that there would be ~10e7 N of thrust from the sun due to solar wind.
My question is does there exist a point, similar to the sun-Earth Lagrange point, where the gravitational *and* the solar wind forces will cancel out and so the described object would remain stationary without the need for any (or at least very little) maintained thrust?
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There is no *single point* like that. Forces created by gravity and rotation are independent\* from actual mass or shape of the satellite. That's why we can talk about such points, universally.
Force created by solar wind, light pressure and so on depends on the shape of your satellite, surface, how reflective surface is, and so on. Thus, at the same point it can be quite large for one satellite\*\* and rather minuscule for another.
That said, you can replace some of centrifugal force with solar sail power, and do some maneuvering by changing sail's orientation. How far from Lagrangian points your point of balance would be depends solely on the design of your craft, and thus, indirectly, tech level available in your world. In theory, if material wouldn't be a problem, you could even have a stationary platform that does not circle around your star at all. Or even propel entire star system with [Shkadov Thruster](https://en.wikipedia.org/wiki/Stellar_engine#Class_A_(Shkadov_thruster)).
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\* With assumption that mass of the object in L point is irrelevant in comparison with Sun and Earth.
\*\* We don't have a word for pseudo-satellites on forced orbits, so I'll just use closest word we have.
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In a [previous question](https://worldbuilding.stackexchange.com/questions/100864/impact-of-lack-of-fauna-on-an-industrialized-society) I asked what the impact of lack of above-ground fauna would be on an industrialized society, such as with a tech level of 1940s-1950s. While it largely wouldn't impact such a society, it might cause significant issues for pre-industrial societies.
In order to determine just what the "Starting Tech" level for this world is, I want to explore some of the issues with a lack of fauna. The first of these issues is **Lack of work animals and how it affects city size**.
Some basic information:
* The humans on this planet arrived via space but were unable to take any significant technology with them.
* They have food covered via [food processing](https://worldbuilding.stackexchange.com/questions/74396/early-army-without-foraging-how-do-we-keep-ourselves-supplied-in-the-field), farming of some Earth crops they managed to save, and farming of genetically modified rabbits and mice that are capable of providing nutritious meat but also able to eat the local flora.
* There are also fish and large ocean-dwelling creatures as well.
The current assumptions are they have access to decent wood or wood substitutes, can build ships, and are pretty much entirely coastal or along rivers since water is the easiest form of shipping. So things can be moved with large and small vessels, but farms by their very nature aren't going to be small.
Humans are the only significant power source for moving things across land. With this in mind, **How large can a pre-Industrial city be** with a technology level of roughly 1500-1600s? You can take a bit of leeway with the technology level - The population did come from the stars and was able to recreate some historic technologies.
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Based on the fact that Tenochtitlan, the capital of the Aztec Empire, is estimated to have had about 250 000 inhabitants in 1519, ***lack of draft animals is not a deciding factor when it comes to city sizes***. The Aztec domesticated only dogs, turkeys, and ducks, all of which were used as food sources. Yet, they achieved at least 60% urbanisation. Climate and soil fertility might be more influential factors when it comes to cities.
Therefore, your city can be any size comparable to [historic cities](https://www.wikiwand.com/en/Historical_urban_community_sizes#/Early_Modern_era) of the corresponding period. It is not possible to give a better estimate without knowing more about specific conditions in specific locations.
I believe that your people can achieve higher levels of urbanisation and denser populations than historical examples. Being space colonists, they have an advantage of not inventing the wheel. Of course, it presumes that not all knowledge is lost.
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**To address some technological problems:**
The comments point out the lack of leather, ground transportation, and animal power and mention that all of these will prevent technological development. It might be true if humans start from square one, but it is not your case.
**Leather** can be obtained from genetically modified rabbits. They could've been genetically engineered by the original colonists to provide high-quality leather and fur. And further generations could've used selection to improve those rabbits.
**Ground transportation** is a bit challenging but still is far from unsolvable. Your people can use [sail wagons](https://www.wikiwand.com/en/Land_sailing), i.e. sailboats adapted for moving on land.
[](https://i.stack.imgur.com/A4Ihc.jpg)
These land yachts were built in 1600 to entertain nobles (image from [Wikipedia](https://en.wikipedia.org/wiki/File:Simon_Stevins_zeilwagen_voor_Prins_Maurits_1649.jpg)).
Apparently, land sail carriages were used in China as early as the 6th century. Your civilisation will have no problems building them considering that they have developed ship-building technologies.
The lack of **animal power** is relatively easy to address by wide utilisation of [hydro-](https://www.wikiwand.com/en/Hydropower) and [wind](https://www.wikiwand.com/en/Wind_power) power. Both were used for centuries with great success.
Ploughing might be a problem, but your people might adapt sail wagons for this. Alternatively, they may use low-level farming technologies and rely on soil's fertility and good climate ([the way Aztecs did](http://www.aztec-history.com/aztec-agriculture.html)).
Further research suggests that ploughing is not really necessary. [No-till farming](https://www.wikiwand.com/en/No-till_farming) is a [very](https://www.usda.gov/media/blog/2017/11/30/saving-money-time-and-soil-economics-no-till-farming) [viable](http://www.bbc.com/news/uk-england-38332276) [option](https://www.wur.nl/en/show/Better-soil-quality-and-yield-by-no-longer-ploughing-maize-soil.htm). It can be even more attractive on another planet since there are fewer pests. Moreover, no-till farming is much [more](https://geneticliteracyproject.org/2016/06/02/no-till-agriculture-offers-vast-sustainability-benefits-so-why-do-organic-farmers-reject-it/) [environment-friendly](https://www.washingtonpost.com/news/wonk/wp/2013/11/09/no-till-farming-is-on-the-rise-thats-actually-a-big-deal/?utm_term=.3cc109f14be0) than traditional ploughing. No-till farming has its own problem, but many of them can be eliminated by genetic engineering. And we know it is an option in your world since rabbits have been genetically modified already :).
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Your biggest issue will be lack of a plow animal, that will seriously impair farming, the Aztec farming methods were very labor intensive and unstable to boot. Without machines or animals to do the plowing for you, you will have a severe limit on the returns on large-scale farming. That, in turn, will limit your city size, keep in mind the largest Aztec city only had around 200,000 people in it and its supporting territory, that is about 1/5th the size of Bagdad or Alexandria at the same time. It was only able to support this through a lot of human labor in farming (caste system and slaves), unsustainable methods (slash and burn, imperial imports), and lucky local conditions.
Aztec cities did not handle climate variation well, they were highly reliant on natural conditions they could not alter the land to create fertility as well as the eastern, African, and later European civilizations could. This is not to say they were primitive far from it, but the needed a lot more labor to get the same number of calories as their counterparts across the globe, meaning they had less surplus to support other activities. The surplus is everything. Without it, you can't support the large numbers of specialist you need to advance technology quickly. With a better baseline crop (something with higher return and better nutrition like rice or wheat) they might have had more luck but it is difficult to say.
Really without a draft animal, your civilization will be lucky to reach the industrial age. Your best bet would be to have them start with tractors or at least repurpose as much machinery as possible into tractors.
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[Question]
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Friends,
Many years ago—in a book about building space stations—I read that humans can thrive and maintain enough bone density and muscle to successfully reacclimatize to live at 20% Earth's Gravity.
I don't remember the name of the book and since we can't simulate 20% Gravity here on Earth, I'm curious how the figure was arrived at.
At any rate, picture a multi-tiered structure with artificial gravity ranging from 60% with levels at 50%, 40%, 30% & 20%. the main character spends time doing manual labor on each of the levels regularly.
However, his house has 60% Gravity—but his bedroom is set to 10% to maximize rest. He also has a weight room at 100% Gravity where he spends 2 or 3 hours lifting three time weekly AND he has a walking track where the gravity is 130% Earth's Gravity.
Should he show any bad effects—or benefits—from spending about two-thirds if his time in a low-gravity environment?
Saxon Violence
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> Many years ago—in a book about building space stations—I read that [...]
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I am afraid that since then studies have gone further, showing that human bodies suffer in low gravity, showing muscle tone loss, bone weaking and immunodepression.
Astronauts nowaday struggle to contain the damage by constantly exercising, but still getting back to normal gravity requires some days in which and the whole process it is not even clearly understood by medical scientists.
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> Scientists aren't yet sure how gravity "signals" the body to keep bones and muscles strong. "We know that, somehow, gravity is converted from a mechanical signal to a chemical signal -- and we know a lot about these chemical signals" [[source]](https://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1)
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Long story short, we have no experience, yet. Astronauts in the Space Station are guinea pigs used to answer this question, and tell if we can really leave this blue bubble and venture into space.
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In Doctor Who's *[Silence in the Library](https://en.wikipedia.org/wiki/Silence_in_the_Library)* the Vashta Nerada, a carnivorous alien species that exists on every planet, exists in darkness and shadow, including the shadow a person casts standing in a room. Not surprisingly, the episode does not show any Vashta Nerada, but that's part of the magic.
Were my world to be inhabited by such creatures, would they be visible to non-remote scrutiny?
1. Given that the 3D space above a cast shadow is "less dark" (at least I believe it's "less dark" as I suspect more photons flow through that space than are hitting the ground within the shadow) and therefore the creatures will retreat to the point of least light. E.G., they're only within the 2D space of the shadow.
2. Given that you, the examiner cast a shadow that can somehow be filled with the Vashta Nerada (the episode suggests you need no connecting shadow to allow the critters to move from one place to another. They exist within shadow, period.)
3. Given that I'm only interested in how a living body would conduct the investigation. Please do not roll up a robot the Vashta Nerada would not care to sample as a food source.
How would you personally investigate a 2D phenomena that, because of your own shadow (expression of yourself in a 2D world), threatens you?
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I don't think this is a particularly good answer, but I am playing with the idea trying to make it into something which makes sense to me (apologies if it doesn't work for others)
Can a 2D lifeform have mass?
Normally, I would have said not, however this 2D lifeform certainly has a 3D presence, because it can consume 3D food, so that mass must go somewhere.
We are looking for a shadow that has weight. Maybe not a lot of weight, because it must have some way of dispersing the mass it consumes, but that mass must have gone somewhere, but where?
I do not think that this is a 2D lifeform. I think this is a 3D lifeform, but only 2 of those dimensions agree with our 3 dimensions - the other one is at right angles to our 3rd dimension. Possibly there is no light, as we know it, in their 3D world which is why they are expressed as shadows in ours.
This means that the Vashda Nerada will be encoutering us as 2D objects and somehow converting us into 3D objects of their native type preserving mass but not dimensional orientation.
From the point of view of safe investigation, I would try very very hard to cast no shadow - lots of lights on me.
From the point of view of investigating the Vashda Nerada, especially in a quantative way, I would be feeding shadows and weighing them and monitoring small variations.
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Step one: get a glowing jumpsuit that glows so bright you have no shadow.
Step two: get a long glowing pole, with a not glowing circle on the end of it, and a string hanging down from the middle. It sort of looks like a giant paddle ball thing with a long, glowing handle.
Step three: Tie something the Vashta nerada would eat, like a rabbit or mouse to the string.
[](https://i.stack.imgur.com/pbFi1.jpg)
The red ball is a mouse. This reminds me of looney toons or something.
Step four: Hold pole in front of you, bait will be in shadow and be eaten, and you can observe, because you have no shadow because you are glowing.
It's like fishing.
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I remember that the doctor mentioned on that episode, these creatures are the house dust hit by sun ray but only alive on the dark, I think they can't live on 2D space, they are microscopic 3D creatures that hate light.
So if an object have a shadow, lets say a sphere, this shadow is a kind of tube. Other near sphere will not have the shadow connected on the ground but on the entire 3D space, so the creatures can spread.
When the sphere is far apart, the shadow simply do not touch each other, is there a light wall blocking the spread of the vashta neranda, they will just die if cross the light wall.
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# The existence of these creatures is scientifically ill-defined, but under rather-generous assumptions which might enable their existence, the answer is an unequivocal "yes".
Like much else from the fantasy *Doctor Who* (which pretends to be, and is sometimes regarded as, "science fiction"), the "science" of things-that-live-in-shadow really *isn't*, but you tagged this [science](/questions/tagged/science "show questions tagged 'science'"), so I have to do my best. There's a continuum here with [science-based](/questions/tagged/science-based "show questions tagged 'science-based'"), and in-particular, we need to discuss the scientific properties of the Vashta Nerada before we can talk about how to scientifically observe them.
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### First, your assumption that the Vashta Nerada must be 2D is incorrect.
To respond to your first numbered item:
1. The 3D space above a cast shadow is **not** "less dark". The "[light field](https://en.wikipedia.org/wiki/Light_field)" (or light flowing through every point) varies mostly continuously, except at surfaces (since some photons reflect). Because of this reflected light, and the fact that most surfaces scatter light at least somewhat diffusely, the shadowed area is typically brighter than the so-called "shadow volume" above it.
However, the darkest parts of objects are usually their back-facing surfaces or crevices. E.g., the undersides of a table, not the floor underneath it. So, while these regions are not 2D, we expect to find the Vashta Nerada squeezed inside them.
### Second, the larger issue is that what you mean by "shadow" is poorly defined.
In reality, everything is a light source (that's how your eyes work, after all, by absorbing light from them). Your pants are a light source, lighting up the room with pants-colored light.
(If you think there is some difference between an object *reflecting* light versus an object *emitting* light (there isn't; the photons don't care), consider that [*every single atom in the whole universe* emits some light](https://en.wikipedia.org/wiki/Thermal_radiation).)
The idea of a "shadow" is really just an anthropocentric way to describe the path-length-1 occlusion of a particularly bright light source—and, because of this, *nothing* is truly "dark" in a physical sense, and few things are "dark" even in a visible-light sense. Consider that you can still make out the carpet inside your shadow, and that you are not peering into a seemingly infinite abyss blacker than space itself.
### Defining a better Vashta Nerada
The properties here are really quite fantastic. Presuming that creatures like this exist, they must be able to anticipate where shadows will be, teleport as shadows are created or destroyed, and shrink or grow to adapt to shadow changes. Therefore, they must be quantum energy be—(nope, I'm sorry, you do the handwavium).
Pre-cognitive self-teleportation is effectively a god-power, for reasons that should be obvious, so we have to nerf it. Say, make them just really, *really* fast. They can also abide some light, or else they couldn't exist at all, let alone hunt inside everyday shadows.
Since size-change is hard to do without violating Physics, having them small in the first place is obvious. Maybe rodent- or grasshopper-sized. Which of-course makes them likely less-threatening to humans. Maybe they can poison you, but they're less likely to be able to outright *eat you whole*.
Now that we've placed some limits on what the Vashta Nerada are, we can start to reason about how to observe them.
### Observing a Vashta Nerada
And the answer turns out to be really simple. Observing a Vashta Nerada is as easy as looking toward it. All shadows contain some light; for most shadows this is even visible light. Since true super-absorbers do not exist, the Vashta Nerada [must reflect some light](https://en.wikipedia.org/wiki/Black_body), which you could then see. Q.E.D.
For more creative approaches, try trapping one. Entice it into a nice, dark metal flask. Then close it up and turn on an interior light. This procedure happens so often in industry that it's astonishing we've never seen one before.
Or lure it into your car and drive it to [Bonneville Salt Flats](https://en.wikipedia.org/wiki/Bonneville_Salt_Flats) before sunrise. Or make a shadow under a cardboard box, then set the box on fire—instant fried Nerada, ready for dissection.
If I were actually imperiled by such a creature, I might head outdoors. If it's a cloudy day, I won't cast a shadow (or, more accurately, the proximate light source is the gray sky, not the Sun, so my shadow is diffuse enough that it appears nearly light). The Vashta Nerada would be forced to remain in the building, which I would subsequently [nuke from orbit](http://tvtropes.org/pmwiki/pmwiki.php/Main/ItsTheOnlyWayToBeSure).
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We live in a 4-D universe, *everything* in it possesses length, width, height and duration. So, you want to change our universe so that some hypothetical zero-thickness structures (living beings, no less!) can exist.
This would require a profound modification to our Physical Laws. I've zero idea how to do that - how to change them so that they would continue to be consistent AND allow for both 2D and 3D things to exist (as they travel through time).
If, as you claim, such beings exist only in shadow (what does that mean?) There's no object which isn't in some light source's shadow, so perhaps you mean a shadow visible to the average human eye in the given lighting conditions. Well, that's a real problem. Take an object sitting on a table under normal lighting. It casts a shadow. Now get a high intensity light, shine it from a different direction, and do not block the normal lighting with the light source. You have created a shadow but the object continues to cast a shadow from the normal light, yet it may not be visible due to the high intensity lighting shining on that surface.
So, what rules do these 2D beings follow where can they exist and where can't they? I have no idea. The problem lies with the assumption that a shadow is "dark", but I've explained why that's not necessarily true. (Unless we agree that "dark" is just a measure of relative light intensity.)
How would I investigate such beings? I'd use the appropriate tools, machines, and measuring apparatuses. What those would be can't be described since they don't exist in our world (nothing is purely 2D here).
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**A couple possibilities,** the first is that it would actually be fairly easy to see a 2D object if one were to exist. While a 2D object turned sideways so that you were facing the nonexistent dimension would seem invisible, any tilt would cause the flat surface to be visible. If the object was large enough or you used a precise enough camera, then being out of alignment with the nonexistent dimension by mere fractions of a degree would make it visible. The further out of alignment you get the larger the 2D object will appear.
[](https://i.stack.imgur.com/H2K3M.jpg)
Unless the object remained in perfect alignment with you, you would be able to see it. If the object remained in alignment with you, you could still observe it by using multiple observers from different angles.
**The second possibility, light would pass straight through it.** It lacks depth, it is possible light would simply pass straight through the infinitely thin object and move on unaltered. This basically would mean the 2D object was completely undetectable.
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"The most sophisticated of the galactic elite crave the most exotic delicacies and few come more exotic or delicious than diamond cheese. This cheese made only on a small agrarian world on the outer rim contains naturally occurring crystals and is so rare the top 1% wish they could afford it."
I want a cheese which has diamonds or some other crystals that form in it as part of the maturing process, in total it would be about 5-10 percent crystal by volume. These crystals must be like hard stones, harder than salt crystals. Hard enough to break your teeth.
The crystals can't be put in and the cheese can only be made using the kind of technology that was traditionally used to make cheese on earth. As a result putting the cheese under incredible pressure is out of the question, but using copper like for blue cheese is OK.
The cheese is made by milk from a regular cow. However as the cows are from another planet there is for them to have more of a particular chemical from food if it can act as a catalyst or something like that.
Some cheeses have crystalline structures such as Parmesan [cheese crystals](https://en.wikipedia.org/wiki/Cheese_crystals), but obviously these don't turn into actual stones.
It is possible that some sort of basic electrical generator could be used as part of the making process and this affects the structure of some sort of naturally occurring graphene molecules, but it seems unlikely these would turn into diamonds/Swarovski crystals etc.
It might be possible for cheese to be left for a very long time but then I don't know how to prevent the cheese from just rotting.
How do I get these diamonds in the cheese?
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**The short answer:**
There is no way for diamonds to form naturally in cheese.
**The longer answer:**
Diamonds, in particular, are right out because of the processes required to form them. Carbon *needs* to be under incredible pressure and temperatures (usually in conjunction with time) to become diamond - even vapor deposition methods require high temperature and pressures.
Organic crystallization - particularly that of something like honey or salt - is potentially doable, but wouldn't result in anything that looked particularly precious - and crystallization doesn't match well with the process of cheesemaking. The presence or absence of a catalyst is immaterial - the pressing and aging process doesn't generally allow enough solvent to allow for deposition.
The best mechanism I can think of for having crystal-studded cheese is to have some sort of microscopic organism native only to this planet that likes to eat cheese and excretes carbon (or your substrate of choice) in a crystalline structure. Then the aging process could be in caves where these organisms live, and they chew their way partially through the cheese and leave diamonds in their wake. I can't think of a solid biological justification for these creatures to behave in this manner, but it's a big universe.
*Edit:*
I should add that these microscopic organisms would still have to, internally, create the pressures and temperatures required to create diamond, as there is no chemical way around this necessity of the diamond formation process. This would be incredibly energy-intensive (obviously) and is therefore difficult to justify, but could be handwaved as something natural but unexplainable, a la The Force.
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Amethyst can grow at standard temp and pressure (you can buy kits online). Now, it requires some substances that are toxic (to eat), to humans. Maybe those can be neutralized/filtered out?
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We [escaped the galactic government](https://worldbuilding.stackexchange.com/questions/87034/now-how-to-escape-fun-loving-immortals) and we have created life, and sentience. We have created marvels and spectacles. We have let it loose. How can we control and monitor the growth and evolution of our creatures.
These creatures have been made and grown, we then left them in our tailored environment but how do we control and allow for intervention when needed without becoming known. We would like to be able to manage their society, is there anything we can do when placing them in their environment or anything we can do to the environment to change this?
To make it less broad without making any answers mute, we wish to be able to stop and start our society, control what they can and can't, for example we have to allow them to do something. Everything is our choice.
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The standard recommended method for creator/creation interaction is called Religion. Many distinct flavors of this management tool exist, but most involve a least three levels of communicators.
* Clergy... these are normal instances of the created life form which have received special training in the written texts which document the creator's desires and expectations. These are the lowest level communicators and they handle the large-scale distribution of beliefs and instructions to the masses.
* Prophets... these are enhanced instances of the created life form which have a mental link with the creator, allowing messages to be sent directly to them without any intervening texts. Received messages take the form of dreams, visions and auditory hallucinations in which the creator speaks either clearly or figuratively to the prophet.
* Manifestations... these are extremely enhanced instance of the created life form which can actually contain (usually only for a short time) the conscious mind of the creator. They are also usually equipped with extensive matter manipulating cybernetic implants so that they can perform miracles when proof of divinity is required. When prophets and clergy are not enough to change the created populace's course or actions, a Manifestation can usually set things back to rights.
As for not becoming known, that is never really a problem for religions. Just make sure that your creations are equipped with adequate rational capacities and many will choose to disbelieve in the creators no matter how much evidence contradicts that disbelief.
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I believe sentience is a separate issue from **intelligent**; if they are not very intelligent than you will be able to simply outsmart them, trick them and deceive them into doing as you please.
How do we we successfully keep extremely lethal animals caged and controlled in a zoo, so safely that toddlers can be within striking distance of instant death and we are not concerned in the least? By outsmarting them; the snakes, spiders, insects and predators are just not smart enough to figure out how to get out of their traps without being killed. So they wander around their very tiny worlds looking for a way out, for the rest of their lives.
We are intelligent enough to design and analyze enclosures and foresee every possible means of escape they will attempt, and ensure those fail. But we still have access to the animals, can sedate them, treat their diseases, perform surgery upon them, and painlessly kill them when necessary.
Even if the animals are as smart as their creators, this can often be done, with somewhat less surety. We call such environments maximum security prisons.
But in that case, of course, the inmates know they are prisoners; whereas in zoo environments the animals may know they are stuck, but not realize their captivity was intentionally accomplished by humans; they may see their handlers and feeders as just part of their environment.
If your creations are highly intelligent with culture and language then religion and other mind-control protocols will eventually be worn down; it may take hundreds of lifetimes, but rigorous science, mathematics and general understanding of physics and "how the universe works" will accumulate and eventually dominate the society; thus atheism arises and cannot be stopped; it is inevitable given a scientific culture that demands either proofs or independent replication of experiments.
### Here is how to secretly control a highly intelligent species.
I will put this, for the purpose of clarity and accessibility, as if we humans are the created species and the creators are aliens with highly advanced science. I presume you can translate this to your story premise without humans.
Suppose aliens are only as intellectually capable as the best of humans, but they have a billion year head start on science. Say they created us, circa 100,000 years ago, and have been watching us this whole time. Get up to about 1900 AD: It would be relatively easy for them to monitor us and know who is working on what and simply assassinate them, quietly. The general theory of relativity never sees the light: Why? Einstein went to school to learn physics; and they monitor every person that does that, for life. Einstein had to *write* his first paper, they saw that happening. And then Einstein the patent examiner is mugged and killed for the content of his thin wallet, his paper and works quietly vanish.
The aliens that created us can equally create avatars for themselves: completely biological and identical to a humans, but without any intellect: Their brain *looks* like a human brain, even under a microscope, but is laced with microscopic electronics so they can be 100% controlled by the aliens, and appear natural to real humans. The electronics are designed to dissolve if the avatar is killed or compromised, and kill the avatar in the process by what seems natural causes (heart attack, stroke, seizure). For near immortal aliens a human lifetime is a short blip; so they could even create such avatars as infants in the womb of a quietly abducted (or seduced) female, and let them be born and grow to adulthood with an interest in politics.
The alien technology and understanding let them turn any such avatar into a powerful and wealthy citizen of this planet.
So while murder is a tool they can employ as needed, they also have social tools: They can manipulate money and opportunities for research that guide the smartest of their creations into fields that do not threaten them.
So we have no Manhattan project unless they want one. We have no quantum physics without their approval. That research is just not funded, and the leading lights **we** recognize ended up working on things that did get funded: biology, mathematical puzzles, entertainment: Do not forget the aliens (in my premise) are much like humans emotionally, with very advanced tech, so they could still be very much entertained by their creations producing stories, humor and fiction, solving puzzles and in general being creative with machines and inventions. They love Shakespeare and Stephen King, they love Star Wars and Die Hard, Mozart, Rock and Roll and Hip Hop.
But they are stopped short, by avatar politicians, avatar businessmen, avatar assassins and other such interventionists, on any tech that could get the aliens discovered.
So there would be no Manhattan project, no quantum physics, no general relativity, no space exploration, unless they want it to happen. So we see this as our own stupidity getting in our way, without realizing the billionaires and dictators and corrupt politicians are all just avatars 100% controlled by the aliens to thwart any progress toward true understanding, and to force us into non-political solutions for our problems: e.g. they **don't want us** to find a political solution to global warming, for their own reasons they want to see us invent a **technical** solution. In this scenario, even Hitler and the Holocaust would have been their choice, perhaps to spur the complete rewrite of world politics that ensued after WW II.
You can control a smart species secretly; by secretly manipulating their economy, their research and their politics, through money, secret information obtained via hyper-advanced technology a million years ahead of our own, plus the use of avatars, and "explainable" assassination when necessary (i.e. it looks like an accident, disease, or plausible human-on-human violence).
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If you have made them, you know how they behave and react to certain stimuli. Basically they will be something more than dogs to you.
Since we can train dog to rescue people, guide blinded persons, search for drugs or even attack and kill other animals/persons, you can very well adapt the same training to these creatures and influence their society.
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I'm looking for answers that focus on changes in internal anatomy that allow humans to survive in a high-g environment. If dramatic visible change can be avoided, that'd be great.
**Problems**
*Circulatory*: Blood is much harder to pull away from the ground. Energy needs to be delivered to muscles at a higher rate
*Muscular*: Muscles are under more stress due to lifting heavier loads
*Skeletal*: The skeleton need to support a load with 3x the weight
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The first thing to go would be posture. This whole standing upright would have to be reconsidered. After all, putting the most oxygen hungry organs in the body up at the top is asking a lot of our earth-born heart and veins. Completely prone would become everyone's preferred pose which might cause a sharp decline in personal productivity and mobility.
We would also have to give up salt. After all, who needs high blood pressure when your blood already ways three times as much as normal. Limiting dietary iron to induce anemia would become good medical advice for putting a little spring back in your day.
At least dieting would get easier. Loosing multiple pounds per week is easy when even the lightest broth feels like thick pea soup on the tongue. Pigging out on ten pounds of ice cream would still leave the gallon container half full.
Okay, so we aren't going to get very far on this planet in our current condition. Time for the genetic scientists to step in...
The name of the game is decentralization. Instead of relying on a single centralized pump, smaller fluid flow assistance organs should be spread out around the body. No major vein or artery should be run for more than a foot before reaching the next of these smaller hearts. In blood pathways which defy gravity, the hearts should be even closer together.
In later generations of the genetic manipulation, the entire idea of hearts and veins will be abandoned. Instead the blood passage ways would themselves be pumps. Every inch would be segmented with valves and lined with muscles such that no portion of the system simply holds blood. Every part contributes to the circulation of the body's blood supply.
Along with the enhanced plumbing, it would probably be wise to rearrange some of the systems. Eyes and ears don't weigh much so they can stay up at the top, but the brain could migrate downwards. Men have been accused for centuries that we keep our brains in our pants. Now in a very literal sense, that would be true of women as well.
We would want to keep the overall humanoid shape unchanged for aesthetics as well as to assist with dealing with other humans from other worlds. But we would not want to put anything heavy up in the head section with the ears and the eyes. So maybe just a cartilage shell containing helium. We are the airheads and proud of it!
Which leaves the bones and muscles... that is the tough part. It is sort of like building a muscle car. A bigger engine produces more power but it weighs more meaning it takes more power to move. The geneticists would have to work closely with material scientists. The age of all carbon and calcium would have to end. Light weight metals and silicon cording might replace the bones and tendons, allowing our current muscle mass or maybe even a little less to carry the load. If not, then we would have to plunder the animal kingdom for a muscle upgrade. Human muscle to strength ratios are abysmal compared to many animals...
["Scrap the Caddy, Clyde"](https://www.youtube.com/watch?v=BkD7UTYrbB0)
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Obviously future tech is allowed, but I'm looking for a solution using technology as near as possible.
I would like to send a moon the size of Earth's moon crashing into a planet Earth's size. I would appreciate it if the victim planet, who has technology the same level as mine, cannot stop this event. That is, if you have a solution requiring technology hundreds of years in the future, the victim planet will also have this level of technology.
Extra points if the victim planet doesn't even notice until the moon starts crashing down.
I'm looking for a) lack of detection by victim planet and b) closeness of technology to modern day.
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Using self-replicating nanotechnology, plant *weeds* that will cover the entire surface. The trailing hemisphere becomes vantablack, absorbing all the sunlight hitting it. The leading hemisphere becomes mirrored, reflecting all light.
This will cause a thrust that slows the body along its orbit, so it will spiral in.
In general, about 1016 watts of power is available by harvesting *all* the sunlight that reaches the moon. Note that using this much power is a world’s definition of the [Kardashev Type I](https://en.wikipedia.org/wiki/Kardashev_scale)! The moon is smaller, so this is 7.4% of Earth’s K-I. This is still 700× the current energy consumption of the entire human civilization.
Even so, The moon's orbital motion has a kinetic energy of about 7×1028 J, so it would take 250 thousand years to bring it to a complete stop.
The problem is that when it reaches its [Roche distance](https://en.wikipedia.org/wiki/Roche_limit), it will break up and you end up with rings, not a crash. That is true with *any* slow gradual method.
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See also [this older question](https://worldbuilding.stackexchange.com/q/6959).
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**If sci-fi tech is allowed:** Tunnel into the Moon and build massive *Star Trek* style impulse engines to slow down the Moon. I picked the ST version because they have no reaction mass output and would be invisible to modern day scanners. If you wanted it to be invisible to advanced scanners, borrow a Romulan cloaking device for the engines.
The more you can slow its orbital velocity the faster it will fall in.
**If you want to go the ridiculous tech version:** take a page out of the [Lensman](https://en.wikipedia.org/wiki/Lensman_series) tactical guide and use massive inertialess drives to position any handy moon to the point where the moon's initial velocity intersects with the planet's motion. Then turn off the inertialess field. Better yet, with some planning, accelerate the moon to a significant fraction of c and then pop the inertialess field in place.
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[Divert a large enough asteroid](https://worldbuilding.stackexchange.com/questions/3274/how-could-a-specific-asteroid-be-diverted-to-impact-the-earth) (I'm talking really large) to pass slowly between the planet and moon, attracting them towards each other. The asteroid could then escape the system after setting things in motion.
Even if possessing similar technology and resources, the target planet's inhabitants might just fail to detect it until it's too late.
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Try smashing the planet with a moon very tiny compared to the Earth's moon but larger than the asteroid that killed the dinosaurs. I know that's not what you want but your victims will be just as dead.
Suppose that your target planet has a very small moon orbiting at a great though realistic distance. Suppose that the people of the target planet don't have many facilities on that small moon or consider it worth defending.
Possibly they have a lot of important facilities on closer moons and orbital space stations a lot closer to their planet. And they might have super force fields around their entire planet and those close orbital facilities to defend against any attack. And giant orbital ray guns to blast any space ship that comes close to the planet and its orbital facilities.
So the attacking space navy comes and blasts at the planetary defense shields at a safe range and the planetary defense ray guns keep them covered, firing whenever they get too close. And many ships duck behind the outer moon and pop out from behind to fire at the planet and then duck back into cover. And the planetary defenders think that's all they're doing.
But some of the space ships are unloading parts for a giant space drive, a giant rocket or anti gravity engine or whatever. It took them months or years to design and build an engine so much bigger than any built before. And using tractor beams they are assembling it on the back side of the moon but pointed forward so that its trust will slow down the orbital speed of the moon.
So they turn on the giant engine and it quickly slows the moon's orbit so that it soon has no speed relative to the planet and falls toward the planet under the gravity of the planet.
It will take just a few days to smash into the planet, just as Apollo space craft took about three Earth days to "fall" from Lunar orbit to low Earth orbit.
The defenders try blasting it with their giant space ray guns, but they can't vaporize away enough of the moon's mass in a few days. It will still have enough mass and velocity to cause an extinction level impact.
They can't build a giant space engine to take to the moon and change its velocity and trajectory in the time they have left.
They send ships with giant atomic bombs to try to reduce the mass and/or change the velocity of the falling moon, but those are all blasted by the attacking space armada once they pass outside the defense force fields.
They're doomed.
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The path of least resistance is to reduce the moon's speed. This will eventually upset its orbit so that it falls into the planet.
The challenge then is coming up with a way to reasonably accelerate the moon in the opposite direction of its rotation around the earth.
Conceivably, one could apply nuclear explosives or [nuclear rockets](https://en.wikipedia.org/wiki/Nuclear_thermal_rocket) to slow the moon's orbit. Alternatively, large, high-velocity asteroids or other massive bodies could be set on a collision course for the moon. Maybe the inhabitants would believe they'd avoided certain disaster thanks to the moon blocking the rogue asteroid, only to discover later that the impact has caused the moon's orbit to decay.
Explosions and asteroids seem pretty dramatic, but nuclear rockets installed on the far side of a tidally locked moon could be surreptitious enough to go unnoticed.
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In gravity simulators, you can crash moons by flying other bodies very near them / slingshotting around them. The gravitational attraction of the passing smaller body can slow the moon enough to destabilize its orbit.
Benefits:
1: Fussing around with some asteroid at a great distance will not be that noticeable. Over a long period you can incrementally add energy with your rockets to get the thing up to speed. Maybe you could use a gravitational slingshot off of something massive to get some more speed.
2: Rapid, impact-free flyby of asteroid (turn off the rockets or they will get wise!) might not be noticed; if it is noticed but target planet will be pleased it was not itself hit.
3: Target planet may not realize until later that orbit of moon was destabilized.
Risks:
1. You need really good math up front to calculate trajectories and make sure your asteroid is going to fly through the correct path to destabilize the moon, because there is no good way to steer it.
2. Maybe you should just crash that asteroid into the moon and slow it down that way.
3. Maybe you should just crash that asteroid into the target planet and call it a day.
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Well its a hard one. You need other bodies to interact/crash into the planet/moon. An other solution is to create a magnetic field (super strong) to time the moment when the north and respetivly south pole of the planet in question are the closest. So a powerful positive magnetic field would start when close to the north pole - to start an attraction, when its nearer to the south pole, the magnetic field becomes negative. Then it would start to accelerat inwards.
I also think there is a physical problem of doing all this. The energy created to move the moon inwards - will be the impact energy inwards. (However there will be alot of friction going on - but it would have been there by itself in x years, assumig the moon is not orbiting away from the planet). But it really does sound evil to do it.
About the events of the planet - you would experience more powerful tide waves, and compasses might go strange. Also I do not know the demagntication about it would lead to. Probably the planet´s poles would be weaker and weaker.
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I am building a science fiction universe, and I am currently thinking of many different unique sentient alien species that would populate the galaxy.
I have thought of a rocky planet with Earth level gravity which has a highly elliptical orbit that causes its tempetures to have massive fluctuations between hot and cold. These extremes make life inhospitable on the surface. However underneath the surface there are large pockets of space that are filled with water up to a certain point and then open air. Imagine massive deep lakes with large amounts of land surrounding them.
The only input of energy into these areas are very large numbers of hydrothermal vents similar to what we see at the bottom of the Earth's oceans. This planet has a very active core causing high amounts of energy output through these vents. My main goal is to have a sentient, humanoid creature that creates a decently complex society within the many pockets.
**Edit: I have added ventilation shafts that serve to dissipate heat out of the pockets and assumed that there is a balance between the amount of heat produced by the hydrothermal vents and the heat dissipated out of the pockets.**
The issue though is the lack of sunlight, and lack of an oxygen based atmosphere. Assuming that the pocket remains at a stable temperature and does not blow up, what kind of ecosystem would arise from this environment, and what gases would these creatures breathe to live?
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The ecosystem that evolves under these circumstances would be very different from what we have on earth.
Consider though: land animals have many unusual aspects which make sense when you consider their ancestors were not always land animals. We came from the sea.
So: start with circumstances that give you the humanoids you want (basically humans) and then move it to present circumstances you want and have your humanoids adapt. You could start with an earth like planet with an orbit that is perturbed - maybe gradually, maybe suddenly such that the end result is what you have. Your Morlock humanoids are descended from ancestors who lived in a very different situation. I like this too because if the previous state was not that long ago (50,000 years?) maybe they could retain wistful legends about the Top Time and how it used to be - sort of like the australian aborigine legends of the Dream Time.
Re getting them some oxygen: you could have vast stores of carbonate rocks, laid down during previous epochs (exactly as on earth). You invent a microbe that lives on these rocks, splitting off the oxygen as waste and retaining the reduced carbon for its own synthetic needs. The energy for this comes from whatever chemical energy is locally available: probably hydrogen coming up thru the rocks. Something like this could be the basis for the food chain. Your humanoids could tend them by plowing / roughing up the carbonate rocks to increase accessible surface area.
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You have a huge problem, there would be no incentive for animals to move on to land. Plants moved to land because they could survive there and animals followed them to eat them. But life around these vents is limited to the vicinity of the vents and everything basically feeds off bacteria that are nourished by the vented chemicals rather than sunlight. Without this bacteria, nothing survives near vents.
Your other major problem is that these are enclosed pools, eventually they will heat up because there is no other place for the heat to go and you'll end up trying to have life living in boiling water and an atmosphere of incredible pressure due to steam trying to expand. I don't think it's going to be stable enough to develop an ecosystem that would support evolving intelligent humanoids.
Another thing is these vents are adding to the volume of the pool constantly, depending on output this would add up. But since evolution as far as we know takes a lonnnng time, a fraction of a percent of added volume would soon add up, so your land area around the pool would might be flooded long before anything evolved, then whatever evolved might be confined to underwater activity if/when the pool meets the ceiling.
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A hypothetical organism is [tetraploid](http://www.dictionary.com/browse/tetraploid) and [isogametous](http://www.dictionary.com/browse/isogamous). To reproduce, four haploid gametes must meet and fuse into a tetraploid zygote. Any four individuals are sexually compatible, barring [self-incompatibility](http://www.biology-online.org/dictionary/Self_incompatibility) or [mating types](https://www.merriam-webster.com/medical/mating%20type).
What selection pressures would favor this method of reproduction over the fusion of a pair of ovum and sperm?
EDIT: near as I can tell, this would be a defense against recessive traits, frequent population bottlenecks and frequent mutations. The downside would be a slower overall rate of evolution, I think.
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Not as likely as Will's answer but:
1. If conditions are such that it takes more than two to guard or feed
the young, having more than two "parents" with an actual stake in
the outcome (by sharing DNA) could do it.
2. In a very fluid environment, having multiple choices of DNA (from
multiple parents) could increase the randomization of the offspring.
If the young are produced in litters, it would make it more likely
that some would have what it takes to survive the conditions they
find themselves in.
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Imagine a scenario where there is rampant DNA parasitism by transposons
<https://en.wikipedia.org/wiki/Transposable_element>
or similar genetic parasites. If there was a good chance that any given parental gene donated to the zygote might be inactivated or damaged by a DNA parasite, then getting more copies would increase the chance that at least one of them would work the way it is supposed to and make a functional gene product.
This is not super far fetched. Transposons are a (longstanding!) problem for DNA based life. Anything that uses DNA to reproduce has mechanisms to limit damage from transposons. This is a benefit of meiosis based reproduction generally over mitosis-type self cloning or budding based reproduction.
Superficially it seems to me that the same might be true in a situation where there is a lot of mutagenesis for other reasons - maybe from radiation?
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Some more-than-usually clever boffins have knocked up a system that allows them to form portals into a region where the laws of physics are rather...different.
An object that is fired through one portal - that is, with no physical connection back to the origin point - will emerge from the other with its speed unchanged and vector shifted to align with the exit portal's alignment - no matter what that alignment is. From the outside, this appears to have instantaneously - indeed, faster-than-light. But experiments to demonstrate its safety show something...odd.
Biological specimens travel through the portal almost entirely unchanged. Bacterial cultures don't grow, animals don't age, plants don't photosynthesize. They bear every sign of having passed immediately from one point to the next. The only difference is that they appear to emerge colder than when they entered.
Radioactive isotopes, on the other hand, appear to decay at an accelerated rate. When examined, they have decayed twice as much as they should have if they had simply made the same journey through normal space.
Technological recorders are a mixed bag. Some technology works, some does not.
After extensive study, the conclusion is this:
**Chemical reactions don't happen in the Pathway**.
A vessel sent through the pathway continues to move through time and space, but it's moving through the time of the Pathway universe, not our universe - hence the apparently instantaneous transit. But during this time, all chemical reactions simply...stop. Complex molecules remain in the state they were when they entered the portal. Heat radiates away as normal with no biological processes to generate it. As soon as the vessel leaves the Pathway, chemistry starts up again exactly where it left off.
So, after all that backstory, here's my question:
**What changes to the laws of physics could produce this effect? And what kind of technology would be able to operate in such a region?**
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## As written, this isn't possible
The problem with changing local physics (among other things) is that it's hard to take objects out of this dimension that haven't been changed by it. For example:
* If you adjust **gravity**, things will stretch or compress
* If you change the **characteristics of matter** objects will not stay together physically (reactions will occur or particles will drift)
* If you change the **speeds of electrons** in their orbits to "freeze" particles, your objects will fall apart
* If you change **thermodynamics**, you can handwave the cold, but you may not be happy with the temperature gradient produced
* If you change **the speed of light** to do instantaneous transfers, you will not in turn accelerate the transfers themselves :(
**Our current model explains what we see, so by changing it, we will see something else happen.**
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## Solutions
### 1. Instant transfer
Given
* Biological specimens lose heat energy
* Radioactive isotopes lose the energy contained in their nuclei
* Change appears instantaneous
Perhaps objects **are** transported instantly (well, as fast as light). This means chemical reactions will take too long; it also explains why living things don't decay.
However, the portals may take the thermal and nuclear energy from molecules and atoms to fuel themselves. Air passing through, which has an abundance of thermal energy relative to other substances because it is a **gas**, will fuel the portal, but it will still take thermal energy (heat) and nuclear energy (hence the decay) at an increased rate for good measure.
Meanwhile, machines reliant on chemical reactions (battery-powered, for instance) will not be able to operate in that "instant"; they cannot record the "jump". However, those that aren't reliant on such a reaction (maybe powered by radiation directly?) could record light as they "jump" in small quantities. This is speculative, of course.
### 2. Handwave a new law of physics or a new fundamental force
Changing the existing laws won't work, but you can always make a new one that **only applies in the Pathway** for whatever cosmic reason. It's just as justifiable as why particles exist, or why photons were made faster than protons - it's the way things are. All science can do is explain it and apply that knowledge.
Write this law or set of laws however you want, but keep in mind the following:
* It should preserve matter as-is; no small-scale changes, because they have a ripple effect (and will decouple molecules and atoms)
* It should allow momentum (to move things) on large scales - kind of like how gravity increases in strength as objects increase in size - but not on small scales, to prevent chemical reactions from occurring
* Weak nuclear force should override your law or force (and act stronger on small scales) to speed up radioactive decay
* Atoms should be able to emit radiation slowly but not absorb it in abundance (to cool down, but also to avoid killing organisms with ionizing radiation)
* Perhaps electromagnetic radiation is exempt from all the above laws when it's passing through a strong conductor (might allow some machines)
Given the above information, you may be able to measure radiation within the void - but you will need to be extremely creative while engineering machines to do so.
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Without a doubt, the most iconic mammals of Australia are the pouch-bearing marsupials. You can find less than 250 species in that one island-continent.
[](https://i.stack.imgur.com/D2nkZ.jpg)
Marsupials have been around for 65 million years, and they are all that's left of a much larger clade called Metatheria, the entire bag of pouch-bearing mammals.
However, Australia is also home to a smaller, more ancient order of mammals--the monotremes, the only extant mammals to retain their reptilian ancestral trait of laying eggs.
[](https://i.stack.imgur.com/jPECi.gif)
In this alternate history scenario, the metatheres either never existed or have been extinct for tens of millions of years, leaving the monotremes as the next best thing. Once there, considering that monotremes were never ecologically popular (only 16 species so far identified in the group's 210-million-year existence), will the egg-layers radiate into a vast diversity of shapes, sizes and characteristics? Or will they just be incomprehensibly alien variations on the platypus and echidna themes?
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It looks like you're wondering about the course of the monotreme's evolution. For a short answer? Yeah, if the monotremes were the dominant species in Australia, their evolution would explode with variety.
The first monotremes appeared in Australia about 123 Ma, and it was called the *Teinolophos trusleri*.
The first metatheres appeared in China some time before this, however, the first *Australidelphia*, which are the marsupials of Australia, would not appear until 55 Ma (the *Djarthia*).
In this beginning, the monotreme's evolution was formidable. In 105 Ma, the *Steropodon galmani* were around, a species of monotreme that was as big as a cat. This may not seem like much, but for the time period this was massive!
However, in 105 Ma, dinosaurs still roamed the earth. In fact, the T-Rex hadn't even appeared yet! It wouldn't be until the Cretaceous-Paleogene extinction event in 66 Ma that mammals would inherit the Earth.
If you had the great extinction wipe out the potential for the *Australidelphia* along with the dinosaurs, then you'd be set for humongous monotreme growth.
When you asked whether there would be a massive diversity of monotremes, without competitors to stunt their growth, the answer is a definitive yes. The marsupials came in and essentially stole the resources from the monotremes, stunting their evolution and causing most of them to die out. If this never happened, then monotremes have the entirety of Australia essentially to themselves.
With this in mind, the flourish of evolution that created everything from sugar-gliders to kangaroos, could have occurred to the monotremes instead. Sixty-something million years is a lot of time to create a vast array of shapes, sizes, and characteristics! (Just look at what the other types of mammals have accomplished!)
Hope this helped!
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In any ecosystem, the existing animals will evolve to occupy all the existing ecological slots. The marsupials did this in Australia, so you can see, for example, a marsupial "bat" (the Flying Fox), a marsupial "big cat" (the Tasmanian tiger), a marsupial scavenger/omnivore (the Tassie Devil), and so on.
If the marsupials didn't exist, monotremes would be able to occupy these niches.
There was also marsupial megafauna when human beings and dogs arrived in Australia about 50,000 years ago, so there would likely be monotreme megafauna unless a large predator species arrived in the ecosystem.
If you don't have a large predator species, you will also have other species occupying the "lazy" ecological niches that are not viable in the presence of animals like cats and dogs, as they did in New Zealand - lots of slow-moving, flightless birds and big lazy lizards.
Of course, you could evolve a monotreme large predator. A megafauna Tasmanian Tiger with the poisonous foot-spears that the platypus has would be fearsome indeed! Or one based on the echidna ancestor that can shoot its spines like some porcupines can ...
You could potentially also evolve fully aquatic monotremes - they would just need to evolve some arrangement for carrying their eggs with them in the water. Since they already have a pouch, all it would take is an extra skin fold to direct the newly-laid eggs into the pouch.
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yes the egg layers would radiate into a wide range of niches and forms. The big thing is no whales or dolphins since they will still have to come out on to land to lay eggs.
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I want to create a terrestrial planet with a very long lasting hurricane similar to the great red spot, I assume the planet will have to be covered by ocean. Could there still be some small islands? If it's possible what natural factors might enable the hurricane to survive over 100 years?
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I agree with TrEs-2b (what a horrific ID it is, too!) on this. Here are some of the reasons why a perpetual red-spot sized storm is impossible on a terrestrial planet.
# 1- Terrestrial planets *never* get to be as large as Jupiter
Yes, they don't. That's because terrestrial planets form closer to the parent star than gas giants, which form at longer distances. The protoplanetary disk revolves at much faster speeds closer to the protostar, making the formation of heavier terrestrial planets much, much more difficult than the formation of heavier gas giants. Think about it, when your protoplanet is moving at a speed of around 28 km/s (for a comparison, the fastest rifle bullet doesn't travel any faster than 2 km/s), there is little chance of *soft planetary mergers*.
The largest terrestrial planet discovered till the start of this year had a mass of about 5 Earths and a radius of about 1.5 Earths ([source](http://www.universetoday.com/13757/how-big-do-planets-get/)). The gigantic telescopes might have discovered something up to twice that size, but a Jupiter sized terrestrial planet? No sir, not even half of half of half of half of the mass of Jupiter (317 Earth masses) has been discovered in a terrestrial planet.
# 2- The giant red spot is truly giant!
Jupiter's giant red spot has the surface area of about 3 Earths. And Jupiter itself has a volume of more than 1000 Earths. So yes, a giant red spot sized storm is not possible on a terrestrial planet as a perpetual local storm.
# 3- A giant red spot sized storm is possible on a terrestrial planet
Read above. I stated that a giant red spot sized storm is not possible on a terrestrial planet as a *local* storm. But unlike Earth, other planets get monstrously horrific, planet-sized storms. Mars gets planet-sized storms once in a while ([source](http://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms)). So while it is rare to get a terrestrial planet with as large surface exceeding the giant red spot, it is possible for terrestrial planets to develop planet-sized storms.
# 4- But that storm would not be perpetual
Gas and ice planets get to develop perpetual storms in their atmospheres due to relatively weaker gravity so high up in the atmosphere. Their volumes are gigantic and the temperature difference between day and night sides of the planet demands heat exchange, resulting in monstrous storms.
Considering that terrestrial planets are far, far smaller than gas giants, any temperature or atmospheric pressure difference between the day and night sides of the planet is sorted out faster with storms lasting no longer than a few days at most.
# 5- The issue of oceans
Oceans are great tools for regulating temperature on a planet. Here on Earth, complex, intelligent life was made possible due to oceans. Not because life originated in the oceans, but because oceans have had **the most** important role in stabilizing temperature on our planet.
If your planet has oceans, it will be much harder to develop temperature difference sufficient to initiate a planet-wide storm.
# Conclusion - No
Here are some of the conclusions we can derive from all the information posted above:
* Terrestrial planets never get to be the size of Jupiter or even close to it.
* Planet-sized storms are possible on terrestrial planets.
* The great red spot is simply too large to be compared with (let alone form on) any terrestrial planet
* Temperature difference is the source of mega-storms on planets.
* Oceans do an amazing job of smoothing out temperature difference on a planet.
* A localized, giant red sized perpetual storm is not possible (as far as we know) on any terrestrial planet.
[Answer]
## No
The reason that Jupiters Red Spot has lasted so long is because it is a gas giant, literal just wind and gas. This allows for a ton of hurricanes to exist, but on a terrestrial planet, this is impossible. The Hurricane picks things up, which slows it down and it already is doomed to fail; this problem would be even worse on an ocean world. In perfect conditions you might get a hurricane that lasts a month, but you are not getting a 100 years and you are definitely not getting a Red Spot scale Hurricane.
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[Question]
[
Assumptions:
Technology equivalent to contemporary tech.
A city with a population of millions built from scratch.
There is a need for an inexpensive underground system that would transport cargo (at best everything from packages, food, garbage, construction materials, etc.) within the city and free the streets from cargo transport.
The system should be reliable and pay for itself in the long term. (At best it should be able to effectively handle different sizes of packages)
Questions:
1) Which technology should be realistically used? Tiny rail cars? Conveyor belts? Pneumatic post? Something else?
2) What is the biggest size of package that would be realistic?
3) Should such a cargo system in any way use the city metro system?
[Answer]
Realistically, underground is much more expensive than above ground using delivery drones. Delivery drones (multi-copters) require much less overhead to achieve much better logistics. Consider several miles per square mile of real estate for rails, tubes or conveyors vs perhaps a few dozen, or even a few hundred drones to get the same coverage and perhaps a few dozen charging stations. Even if the infrastructure is already in place, i.e. an existing underground network of tunnels, the cost of buying and installing any form of conduit far outweighs the cost of buying a handful of delivery devices which require no major infrastructure.
The next best option as far as my limited understanding and basic assumptions go (see the list below the image) is a pneumatic tube system. You would likely want something more complex and versatile than what is used in bank drive-throughs, but I am not up on the engineering aspects of such systems.
The basics are here (click the image).
[](https://en.wikipedia.org/wiki/Pneumatic_tube)
### Edit
I neglected part of the question which states that the city would be built "from scratch". In that case, implementing a system such as pneumatic tubes would simply increase the overall cost of design, materials, planning and engineering for the layout, but would not dramatically limit what could be done assuming that the expectation is that this option would involve a certain up front investment. Furthermore, California is seriously considering a [tube transit system](https://en.wikipedia.org/wiki/Hyperloop) for people, but it could be duel purpose of done cleverly or simply for transporting packages. For example, given a tube car design with separate compartments for people and packages (above and below for example), such a system could conceivably trade packages efficently at stops while people are exiting and boarding the tube car.
The California Hyperloop concept is shown above ground, but the principle is the same whether above or below ground.
[](https://i.stack.imgur.com/HmtTo.jpg)
The tube concept.
---
[](https://i.stack.imgur.com/TdWaj.png)
A tube car cut away. Note that the turbine is for the purpose of evacuating the tube ahead of the car to reduce drag, not for the purpose of propulsion.
---
Below are considerations if the city must be retrofitted for such a system.
---
### Advantages
* existing infrastructure may potentially be repurposed, i.e. old water pipes which may be leaky, could be emptied, sealed with any form of chemical sealer to make them air tight as this would no longer be a health hazard
* underground network and infrastructure already exists making upgrades and installations less costly
### Limitations
* packages would have a maximum dimension by diameter and length and all packages are shipped inside a canister designed to work with the tube system
* the simplest way to design the system is to provide a single tube diameter which best fits most size requirements
* larger sizes must be transported by another method
* smaller sizes still render the cost of a single transit as they would simply be secured inside a canister
* if using existing infrastructure, ***every building*** would have to be refitted to accept or send packages
* if using existing infrastructure the cost of refitting every building must be subsidized because as any network operates (like the internet, or social media) its value is determined by how well connected it is - i.e. if there are thousands of miles of tubes and only a handful of end points using the system, then value of the system as a whole is well below the overall cost of implementation
[Answer]
Look into Walt Disney's plans for the City of EPCOT, which is not the park by the same name we have today.
The central part of the city would route all automobile traffic to a series of roads underneath the public portion of the city, to reduce pedestrian traffic access, and allow for trucks and supplies to navigate the streets to basement cargo bays and garages for their buildings, while foot traffic would be at the ground floor\* and the only vehicles would be mass transit (People Movers as scene in Magic Kingdom in Walt Disney World for local commuting, with Monorails for rapid transit). One could modify this so that above ground roads\* are for private vehicles (personal cars) while lower roads were for bulk cars, and lay the underside roads inline with the aboveside roads for ease.
While not city management it's common knowledge that Magic Kingdom's public area is served by a series of underground hallways\* that run the length of the park and are able to remove garbage, place costumed characters and cast members dressed for specific theme lands, and restock gift shops without a single guest seeing an errant cast member.
\*Because all of these were intended to go in the Orlando area by Walt, the use of Underground is not the best term but the easiest. Florida has a high water table and structures in Florida do not have basements as they would be flooded almost instantly. EPCOT City and Magic Kingdom would have/were built with the "underground structures" being on the ground floor and then the public portion was the "second floor". THere's some discreet landscaping to hide this Around Magic Kingdom.
[Answer]
Because of the assumption of totally new city construction there may be an alternate, feasible solution.
Each property/building requires a unique address with connection to communications, electrical power, potable water supply and storm water pipes. Optionally there may be a recycled water supply for gardens, toilets, etc. Plus organic waste, recycling waste and hard waste services. All of these require trenching for underground pipes and conduit. if this trenching work is done prior to building construction or as part of foundation work then the cost of increasing the diameter of services for package delivery is trivial. A previous answer suggested laying pipes, conduits, etc. on ground level and raising the buildings by one level. A variant would be to lay the pipes, etc. on ground level and back fill over the pipes and conduits to establish a new ground level. With the use of suitable back fill material you could aim for well drained soil.
With a suitable design with recycling pumps the potable water supply can have continuous flow. Increase the diameter of the water pipes and the system could be used to delivery water proof cargo capsules. As each location has a unique address then RFID or equivalent technology could be used for package routing and delivery. It should be possible to have a hierarchy of pipe sizes for packages. For additional cost a property/building owner could specify a larger diameter pipe. To reduce pipe pressure each property would require a pump to raise water pressure. Pump input could automatically swap between local storm water tanks and the low pressure, mains water supply. Return of used carriers could be using a continuous flow storm water system. In the event of a storm event the return carriers would be flushed from the system to increase storm water capacity. Without capsules the storm water system would be able to handle the increased water flows. Only sterilized capsules could have access to the delivery system (potable water supply). Every property would be restricted to the storm water system. At the storm water system pumping stations the there would be sorting of the full from the empty, return capsules. Sterilized capsules would be inserted into the delivery system. If required, empty capsules could be then be delivered to properties for reuse. There could be different capsules for different contents. With RFID technology high priority capsules could be given processing priority. Each property would be required to extract capsules from the system. so there can not be a backlog causing a jam. If there was a jam deliveries to the affected address would be held back. Aim would be automate the system. Using fluid logic as an alternative to RFID it should be possible to use the water flow to route packages.
[Answer]
How about a network of tiny underground railways, pretty much down every downtown street in a town like Chicago. Every street crossing would also have an underground rail crossing, with connector tracks in every direction.
A single track railway would suffice, since in opeations you would simply make all the tracks "one way streets".
It wouldn't use the metro subway system at all. The reason is the typical city metro system is too busy to accommodate the extra traffic.
Every building of importance would either have a siding and an elevator, or simply set the building sub-basement level even with the tracks.
Think tubes maybe 5 feet wide and 7 feet tall, just tall enough a human could walk down the tube without hitting head on the trolley wire. Max package would be about 4' x 4' x 20' or so.
The railway could be run by either humans or automation, depending on the tech level.
[Answer]
if you can build the city from scratch, you could build a transportation system on flat land and then build a concrete ceiling on top which will be the floor of the city (or the next underground level). That underground could be used by robots like our today automated storage systems. The maximum size may be about the same that todays subways have. Of course, you could also use these robots to transport humans. They could even be used for individual traffic. You could enter your destination and have a kind of 2D-Elevator that rides you through the city.
[Answer]
## Whatever system you use will boil down to a few basic principles
1. When delivering a load of cargo going to one place, a single
larger transport vehicle is cheaper and equally fast per unit as
many small transports.
2. When delivering a load of cargo to many places, many small
transports is both faster and cheaper per unit than 1 large
transport making many sequential stops.
3. The less you need to pack and unpack between transports, the faster and
cheaper per unit your transport is.
So, the first part of answering your question is figuring out the optimal layout. If your city has a single massive port for ingoing and outgoing logistics managed by a single entity, then you can minimize the overhead of getting supplies in and out of the city to begin with. Instead of each corporation having their own distribution center, in your city you minimize waste on underloaded bulk freight by making them all share. This central hub would basically function like an Amazon warehouse just being a catch-all for all goods and services. From their you do not necessarily want to unpack all of your freight containers yet though. If you have an industrial district in one place, and residential district in another, then you can send individual freight containers closer to their final destination by just loading them right back on smaller subway trains to district hubs. From those hubs, cargo can be further divided up and sent on even smaller subway carts bringing goods directly to people's homes and buisnessess.
[](https://i.stack.imgur.com/SKmW4.png)
Your Regional Subways need to accommodate train car containers from 8x8.5x20 ft to 8x9.5x40 ft to make sure you never need to unpack one to get it to its right district and remain compatible with all international standards of shipping container sizes.
Your District Subways however are not your normal train system. They are more like tracks for self propelled mining carts that range in size from a shoe box for small parcels up to 4x6x12 ft carts designed for construction materials and large furniture. This way, instead of loading up a large truck and carrying your things to a lot of other stops before arriving at your home, you send the right sized vehicle for the job to pickup or deliver goods in just 1 stop.
Then every home or business has a basement that functions their own private receiving station. You get home from work, and your groceries are just sitting down there in a cart waiting for you to unpack it.
## Why subway carts?
**Pneumatic tubes:** They require a seal that causes more friction than wheels and more precise construction to make; so, the cost to make and operate them is more than traditional subways.
**Flying Drones:** They require less infrastructure, but are much more expensive to operate. Carts passively resist gravity by sitting on the ground, but flying drones need to expend a constant energy just not to fall. They are good for premium expedited shipping of small parcels, but if you are moving around heavy bulk things like furniture, garbage, plywood, etc. then you are wasting a lot of money on them
**Conveyor belts** They will either need to be way overpowered for most of what they transport or they will need to have complex transmission systems distributed every few feet which will break often due to constant gearing up and down. Either way, they are not as efficient.
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[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 wondering if it is possible for life to evolve in a world which lacks any transition metals. I am wondering this because, it could give a plausible explanation for a world which is very unlikely to discover or harness electricity.
The setup is:
* Ultra-advanced alien civilization comes to world and, due to need for metals/conductors, completely mines it out of all transition metals. They could use self-replicating nanobots (or could even be the results of an AI-explosion gone astray, from Earth or another planet), some chemical vaporization technique, etc.
* The entire planet, including iron core, is mined out
* The miners are mainly interested in the transition metals. Particularly iron, titanium, platinum, gold, copper, nickel, tantalum, tungsten; i.e. the metals which have the most use for manufacturing more stuff. However it is safe to assume that a lot of other trace materials are used as well.
* The original inhabitants are completely wiped out during this (very destructive) mining event.
* Whatever entities did the mining move on to other worlds never to be seen again.
As for the hard-science tag, there are two seperate questions.
As millions/billions of years go by:
* Can life evolve in such a world without transition metals (without Iron for example)?
* Is it even possible for a world to structurally exist without a transition metal core?
[Answer]
**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.
There are a host of reasons why the evolution of life on a planet like this will be very, very unlikely.
[Planetary Magnetic Fields](http://www.space.com/11187-earth-magnetic-field-solar-wind.html) are produced by [hot spinning metals](https://www.spaceanswers.com/solar-system/why-do-planets-have-magnetic-fields/), such fields then help to protect said world from cosmic rays, solar winds and other forms of extra terrestrial radiation such as that emitted by stars. Without a conducting fluid core, may that be iron or other such material, the planet will have no means of projecting a sufficient magnetic series around itself, hence leaving its surface venerable to the harsh conditions of space; this surface will be bombarded by fast moving off-world particles primarily in the form of solar winds, ceasing to have a functional atmosphere, leading to climate cooling (lack of [greenhouse effect](https://www.ucar.edu/learn/1_3_1.htm)) and the eventual loss of liquid water on the planet leading to the inability for life as we know it to even exist let alone evolve.
Metals are also dense, adding to the planets overall mass and its structural integrity, removing all said metals off world will lead to a dramatic reduction in planetary mass and therefor reduce the bodies [surface gravity](https://en.wikipedia.org/wiki/Surface_gravity)- further jeopardising any functioning atmosphere present as well as result in a decreased [core temperature](http://www.astronomynotes.com/solarsys/s8.htm) (pressure at the planets centre of mass dependant on the amount/mass of material surrounding it). Yes, the decay of nuclear materials plays a part in the constancy of heat at the core/inner mantle, but this energy release alone will not be enough to maintain a fluid planet centre. Saying this though, radioactive material decays continually - by expelling neutrons, electrons or protons - in a bid to produce a stable nucleus (the rate it does this is defined as its [half life](https://en.wikipedia.org/wiki/Half-life). If protons are radiated from an atom to gain stability, it forms a new element (such as lead from uranium). This makes it possible therefor for radioactive elements to transmute into various transition metals.
Through the decay of radioactive sources, over the course of many millions of years in the correct conditions, reserves of metals can be increased, yet this will not aid in creating a sustained atmosphere or re-establishing the planets mass, in fact, with such nuclear substances now stable, there will be a further decrease in core temperature that will eventuate, in conjunction with the other listed factors in a dead planet with no way of sustaining life as we know it.
Elements such as iron and copper are [vital for life](http://www.eurometaux.org/MetalsToday/MetalsFAQs/Metalsessentialforhumanhealth.aspx), an organisms cells using these metals to produce red blood cells that carry oxygen around the body. Without enough blood cells, the body cannot effectively carry/provide oxygen around it's systems, resulting in many terminal problems the most serious being death. As mentioned by others, calcium (*Ca*), phosphorous (*P*), magnesium (*Mg*), potassium (*K*) and all other period 1 and 2 elements are classed as also metals and equally important in maintaining basic biologic functions (the creation of teeth/enamel for instance as well as regulation of nerve/muscle function - and protein synthesis).
From these reasons, it is easy to see how amazing transition metals are in planetary stability and to organic life generally. Without sufficient access to such elements/trace particles the evolution of carbon lifeforms will therefor be almost impossible, stress on *almost*, for if star trek has taught me anything, its that the universe is a mysterious place where nearly anything can happen given the correct circumstances.
EDIT: here is an Encyclopedia Britannica entry detailing the [role of the transition metals in biology.](https://www.britannica.com/science/transition-element/Biological-functions-of-transition-metals) The most important ones are iron, copper, cobalt and molybdenum.
[Answer]
RNA world, maybe possible.
Enzymes, still possible.
Photosynthesis, possible.
The Rules: no d-block elements, same abundance of s and p block elements, and any f-block elements.
The things that is same as earth life: RNA enzymes, or ribozymes; mg-dependent and ca-dependent processes that does not rely on photosynthesis; ionization and uv catalyzed formation of organic molecules. Any proteins that does not require transition metal ligands. Basic life process does not require transition metals for self replication, nor any protocells does for growth/division.
The Things that need to be changed: iron sulfur clusters: pevoskite type lead and sulfur/halogen semiconductors; III-V semiconductors like indium arsenide/antimony sulfides; with lead atoms of 2V oxyreduction potential and thallium with 1V oxyreduction potential substituting fe-s clusters.
Photosynthesis: bacteriorhodopsin pumps protons forming effective photovoltaics, with just carbon/nitrogen/oxygen/hydrogen/sulfur, NADH and ATP comes from electrolysis of the potentialized solution by carbon electrodes. The Calvin cycle, interesting enough, does not require any transition metals. Another Aldol reaction based cycles, which produces pyruvate and formaldehyde/acetate; does not require transition metals.
Respiration: the tricarboxylic acid cycle does not require any transition metals except for cis aconitase, which is easily substituted with a selenium related protein. The citrate cycle can also be reversed, to produce acetyl coa.
the ATP generating process is the reverse of the bacteriorhodopsin electrolysis process, with NADH and O2 reacting in a fuel cell, producing a proton current.
Fatty acids and coenzymes: fatty acid synthesis does not require metals at all, and most aromatic compounds can be synthesized with rare earth elements instead of iron as a catalyst.
Oxyreductases: antimony, bismuth, tin, lead, phosphorus and arsenic will work as 2-electron oxyreductants, cerium/neodymium/samarium/europium/gadolinium/erbium will work as 1-electron oxyreductants.
Oxygen carriers: insect like tracheae will work for Most animals(bugs).
[Answer]
# NO.
I'm sorry to be so negative, but this question is [not even wrong](https://en.wikipedia.org/wiki/Not_even_wrong).
First of all,
>
> The entire planet, including iron core, is mined out
>
>
>
If they mine the entire core, then is there a void there? So the mantle collapses due to gravity, releasing huge amounts of energy and melting the entire remainder of the planet to a magma ocean? Then in that case, whether transition metals are there or not does not matter, because there is no planet any more to begin with.
---
You also have to consider the **economics of mining**. To make mining feasible, it has to be done with a profit. The price of gold, for example, is so high because it is so rare. But that doesn't mean that it doesn't exist. There's gold everywhere. In the dust in the air around you, in the bricks that are used to build your house, in the soil in your kid's playground. To extract it you need to build the machinery and equipment to extract it. And it has to be worthwhile. Presumably, your nanobots will require tantalum and platinum to operate in the harsh environments you expect from them. But if there isn't enough gold to justify what you used, and pay for the salaries of everyone, and get a profit, what's the point? You will not put 2 kg of tantalum in a machine that will eventually only mine 1 kg.
Therefore, blasting an entire planet (a very costly process) just to get some metals is incredibly stupid, and I would expect that an ultra-advanced alien civilisation would know better.
---
>
> ...some chemical vaporization technique,...
>
>
>
Then just go to a nebula instead. A nebula is essentially a vaporised planet (and entire solar system), before it condenses to a planet. The contents are not high enough though..
---
Consider how mining is done today. Mineral explorers find concentrations of certain elements that were enriched by natural processes, and target those. Tantalum is mined from [pegmatites](https://en.wikipedia.org/wiki/Pegmatite), for example. So you go and find pegmatites. You don't mine a non-pegmatite for tantalum because there isn't any (or enough) there.
---
If you're looking for iron and platinum in a space setting, you go to an iron asteroid like [Psyche](https://en.wikipedia.org/wiki/16_Psyche), and not to a planet where the mantle has the iron bonded to oxygen and you need to smelt the iron. On Psyche, the iron is already metallic. It's easier and cheaper.
---
Now that we know that mining is targeted on ore deposit (i.e. natural concentrations of elements), then this does not matter for the transition metal contents of the things that people are living on. Just the fact that there's an iron mine 10 kilometres from you in one direction, doesn't mean that the soil you're growing your food on in the other direction no longer has iron.
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[Question]
[
We all know (or know how to find) the “rocket equation” that drives the design of a conventional rocket, and we’ve gone over such things as “specific impulse” and the difference between fuel and reaction mass for more advanced rockets. There are books and blogs about it.
But what about photon sails?
How big does a sail need to be? I mean, what factors drive figuring out the particulars of a design? How tight can an interstellar laser be kept, and how much power can you give it? Does it make a difference what wavelength is used? How light-weight can a sail be?
**What are the absolute basics, and what resources are available?**
[Answer]
A solar sail works by using the pressure of focused light to propel a spacecraft forward. Note that this light would either have to be provided by a nearby planet or star - you can't put a fan on a sailboat in irons and expect it to move.
The ideal solar sail is made of a lightweight material that can span a large area (more surface area means more photon collisions), but it must also withstand impacts from cosmic particles as the ship travels. A material like carbon fiber comes to mind.
How does a solar sail work?
Einstein's equations say that the momentum of a photon, $p$ is: $p = \frac{E}{c}$ - where $E$ is energy and $c$ is the speed of light in a vacuum. By some simple rearrangement of the equation for photon energy, $p = \frac{h}{\lambda}$, where $h$ is Plank's constant. Therefore, **smaller wavelengths** of light will have **more energy** and thus **more momentum**.
As [Wikipedia](https://en.wikipedia.org/wiki/Solar_sail#Solar_radiation_pressure) puts it, "An ideal sail is flat and has 100% specular reflection. An actual sail will have an overall efficiency of about 90%, about $8.17 \frac{μN}{m^2}$, due to curvature (billow), wrinkles, absorbance, re-radiation from front and back, non-specular effects, and other factors."
So now you might be saying, how big does my solar sail have to be? Well first, you're in space, so you don't really have to worry about friction. The solar wind will give you a decreasing acceleration as you go away from the sun or whatever light source you are using. Sailors on Earth use a method called "tacking" to move in a direction against the wind. However, tacking relies on the fact that the friction and hydrodynamics of the water and ship allow it to move in the forward-backward directions much more easily than side-to-side. In space, there is no real friction against your ship, so this maneuver would be much more difficult, [if not impossible](https://space.stackexchange.com/questions/370/can-you-tack-against-the-sun-using-a-solar-sail).
Anyway, back to size. Because you're in space, as long as you have some initial acceleration, you will theoretically keep moving forever, until you are pulled into the orbit of some large space object. I don't know how much your spacecraft weighs, but I'll do some math with the ISS for this example, which has a mass of 419,600 kg.
At an initial acceleration of $8.17 \frac{μN}{m^2}$, we want to find out the optimal sail size for (I'm guessing interstellar) travel. A good benchmark is say, $0.90c$, or 90% the speed of light. The speed of light is $299,792,458 \frac{m}{s}$, so 90% of that is $269,813,212.2 \frac{m}{s}$ (we'll round to 2.7E8 m/s). We want to reach this speed in a reasonable amount of time, say a day. That's $86,400$ seconds (if we are on Earth days). So now we can pull up a kinematic equation and figure out our sail area. Newtons are just $\frac{kg}{m/{s^2}}$, so:
$2.7\*10^{8} \frac{m}{s} = area \* (419,600kg / 8.17\*10^{-6} \frac{kg}{m/{s^2}}) \* 86,400^{2}s$
This gives us an area of: $39,244,411.97 m^{2}$ or about 429,182 (square) football fields.
That's not good for us, but fear not, we can focus light energy in the form of lasers.
The pressure given off by light (reflection only) is $P\_{pressure} = \frac{2E\_{f}}{c}\*cos^2(\alpha)$ where $\alpha$ is the angle between the light and the surface normal, which we'll round to $0$ radians because it's easy to calculate. $E\_{f}$ is the energy flux of the light, which is the *rate of transmission per unit area*, or $\frac{W}{m^2}. The pressure term turns out to have units of N/m^2, since you can convert watts to Joules/second but that's another story. What we care about is seeing the amount of watts of power we need to provide this sail:
This time, we'll solve for a more reasonable sail size, say 1 square kilometer. This may seem big, but trust me, it's about to seem very unrealistic.
$2.7\*10^{8} \frac{m}{s} = 1,000 m^{2} \* (\frac{419,600kg}{P\_{pressure}}) \* 86,400^{2}s$
From this, we see that the pressure required is $11,601,100,800 \frac{N}{m^{2}}$. We can use our new equation to approximate the power of the laser required for this kind of travel. Note that we are just glossing over all the losses that take place between the power generator and the light hitting the sail, but those exist too, and are also dependent on distance - more on that later.
$\frac{1}{2}\*c\*P\_{pressure} = \frac{W}{m^{2}} = 1.74016512 x 10^{18} \frac{W}{m^{2}}$
You might be asking yourself how big is that number, really? To give a helpful size comparison, I looked at <http://www.climatecentral.org/blogs/helpful-energy-comparisons-anyone>, which said:
>
> Terawatts (TW) are millions of megawatts, and this is a helpful unit when you’re talking about the rate at which humans are using energy worldwide. In 2008, for example, humans used energy (this includes all types of energy, not just electricity) at an average rate of about 16.5 TW of power — the U.S. consumed about one fifth of that, at 3.3 TW.
>
>
>
Our solar sail requires $1,740,165.12 TW$ of power, or about $105,465$ times the total energy consumed by the world in 2008.
Before I go farther, I apologize if any of my calculations are incorrect. I'm doing some quick napkin math here so I could easily be off by a lot, so please correct me if you notice something.
Still, it holds that solar sails require huge amounts of power to operate at, or they require very large sails. As for how tight an interstellar laser can be kept, that depends on where it's coming from. A laser originating on Earth will have to pass through our atmosphere - not efficient. Optimally, a laser would be generated in some kind of orbit where it could maintain direct contact with the craft.
How tight it can be kept really depends on how long you want to accelerate for. Since you are in space, once you achieve your optimal travel speed, you no longer need to step on the gas. In my calculations, I set travel speed at $.9c$ and our time to get to that speed at one day, but you could achieve the same speed at **much** lower energy costs if you took more time to accelerate to it, say a month.
Finally, the weight of a solar sail would have to factor into these calculations, but as I said before, you could make a solar sail out of a very lightweight material such as carbon fiber, which would greatly reduce the impact of this weight on transportation cost. Realistically, a method for creating large areas of solar sail cloth hasn't been engineered yet, so I can't give you a real estimate on how light your sail could be.
Those are the absolute basics, plus some more advanced knowledge. For anything else, the Wikipedia page on solar sail is very informative on the history of the subject and future projections.
I hope I've answered your question.
Edit:
Once you get to your destination, you need to be able to [slow down](https://space.stackexchange.com/questions/14502/can-a-solar-sail-reduce-the-speed-from-1-10-light-speed-to-achieve-a-solar-orbi). In the 1970s, [Robert Forward](https://en.wikipedia.org/wiki/Robert_L._Forward), an American physicist/sci-fi writer, [proposed](https://en.wikipedia.org/wiki/Rocheworld) [methods](https://en.wikipedia.org/wiki/Solar_sail#Interstellar_flight) of interstellar flight using solar sails. [One method](https://en.wikipedia.org/wiki/Starwisp) even involved using microwave beams to propel an unmanned spacecraft to an acceleration of nearly $24\frac{m}{s^{2}}$.
However, there are many problems associated with these high acceleration/high speed trips. For one, any acceleration over $25G$s ($245.16\frac{m}{s^{2}}$) will result in death or serious injury. Additionally, at even 20% the speed of light, interstellar hydrogen becomes a significant radiation hazard, along with causing [other problems](https://space.stackexchange.com/questions/3405/durability-of-solar-sails-how-big-of-a-problem-is-high-energy-proton-flux) for your sail.
I have also found a quick [calculator](http://www.georgedishman.f2s.com/solar/Calculator.html) that you can use to simplify solar sail calculations. However, it doesn't give an option of using an external source of light aside from the sun. However, [one of the links](https://en.wikipedia.org/wiki/Rocheworld) to Robert Forward's methods above gives a good approximation for the size and energy constraints of a craft accelerating over multiple years using lasers.
A good resource on the physics and material science of the sail itself is: <http://www.niac.usra.edu/files/studies/final_report/333Christensen.pdf>. The NIAC is the NASA Institute for Advanced Concepts and is a reliable resource. The paper talks about the material stresses and manufacturing concerns that might arise in the large-scale production of a solar sail.
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Seek and ye shall find. There are, of course, resources such as the following books: --
*Solar Sails*: A Novel Approach to Interplanetary Travel, Gregory Matloff, Les Johnson and Dr. Giovanni Vulpetti, Springer/Praxis Books, 2008.
*Starsailing*: solar sails and interstellar travel, Louis Friedman. John Wiley & Sons, 1988.
*The Starflight Handbook*: A Pioneer's Guide To Interstellar Travel", Gregory Matloff, Dr. Eugene Mallove, Wiley Science Editions, 1989.
There are chapters on beamed-power and solar-sail spacecraft.
*Centauri Dreams*: Imagining and Planning Interstellar Exploration, Paul Gilster. Copernicus Books, 2004.
Like Matloff and Mallove (1989) above, this work has chapters on beamed-power and solar-sail spacecraft.
Websites with articles on the solar sail technology:
<http://gregmatloff.com/solar_sails.html>
This webpage has the text of several articles by Gregory Matloff about solar-sails.
<http://www.masteringphysicssolutions.net/mastering-physics-solutions-solar-sail/>
<http://www.physicspages.com/2015/05/14/solar-sails/>
The two webpages above have the basic details supported by calculation for solar-sails.
www.esa.int/esapub/bulletin/bullet108/chapter6\_bul108.pdf
The ESA Bulletin article details various solar-sail missions.
Proceedings of the Second International Symposium on Solar Sailing
www.citytech.cuny.edu/isss2010/ISSS2010Proceedingsvx.pdf
The Proceedings are a gold mine of papers on solar-sails and lightsails. No other way of summarizing its contents.
On a related space technology dusty plasma sail vehicles.
<http://spacescience.msfc.nasa.gov/colloquium/archives/2003/summer/robert.html>
This presentation outlines an alternative sail technology, while similar to magnetic sails, it utilizes a plasma confined inside an artificial magnetosphere laced with very small particles of dust and interacts with the plasma of the solar wind instead of solar radiation. The proposal suggests this would be comparable to conventional solar-sails, possibly better.
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In my story women all women just suddenly stopped having male babies eventually causing there to be little to no men around the world.
I'm looking for a way to explain why this happened.
I thought a virus or disease may fit best here. Maybe transmitted by mosquitoes like in Brazil at the moment.
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A virus attacking the Y-chromosome might work.
If it's just preventing birth of male babies (presumably causing miscarriages) you'd need a way to explain why that same virus doesn't harm already living male humans though - maybe it's only transmissible from mother to child? That'd be a strange way to evolve though - while definitely making sense for an engineered disease. Someone is attacking us with bioweapons!
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One of the lowest levels determining sex we've found so far is the <https://en.wikipedia.org/wiki/Testis_determining_factor>.
This gene is responsible for starting the differentiation of male sex organs, from a common base.
So anything that can affect this gene, or the structures that this gene is usually contained in (the whole Y chromosome) should do the trick.
One thing that might influence your choice is whether you want all babies to be born female, or whether you want male babies to be stillborn, ie. does your population initially keep growing at the same rate or at half rate.
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Diseases work fine. You can either
* have the disease on the mother, make the womb reject the male embryo.
* have the disease on the father, killing or weakening Y chromosome sperms (in which case artificial insemination might still work)
* have the disease on the egg itself, causing cell death if a Y chromosome is introduced.
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From what I can tell, we're already moving in that direction.
[This article in Scientific American](http://www.scientificamerican.com/article/are-men-the-weaker-sex/) reports that boys are more vulnerable to a variety of environmental poisons than women are, and also reports that "...wherever researchers have looked, the rate of male newborns has declined."
Though the Y chromosome may be an obvious target, I suggest that it wouldn't work: men with a fatal Y wouldn't live long enough to breed. If, however, it were the X chromosome that were damaged (see, e.g. [Fragile X Syndrome](https://ghr.nlm.nih.gov/condition/fragile-x-syndrome), a recessive trait in women could be passed to sons, causing them to die in utero.
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We'll all be able to choose many characteristics of our offspring soon, it may well become normal and acceptable and even expected. If people decided daughters were more desirable than sons (insert your reasons here) then little boys would become very scarce.
Artificial selection, I know, but not unreasonable.
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You just *think* that "all women just suddenly stopped having male babies" for natural reasons.
Really, though, the Pink Revolution has overthrown the patriarchy and established a One World Gynocracy. Women are getting sonograms for perfectly innocent-sounding reasons, but then get a sex-selective abortion if the fetus is a hated Y-carrier.
Essentially, it's the opposite of what goes on now in countries like China, India, Pakistan and Vietnam where people think little of getting a sonogram to determine the sex and then kill the fetus if it's a girl.
[](https://i.stack.imgur.com/FxwAR.jpg)
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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 wrote a novel based on a human civilization that lives floating cities and dirigibles on a small, atmosphere-abundant super-Earth with a liquid water core (there's a smaller solid core under that, but it's not important).
In this story, the largest floating city looks something like a giant ceiling fan, with a central "city" suspended in the eye of a giant hurricane on seven kilometer-long rotors which generate lift from rising hot air coming from deep inside the planet.
Now that I am going back to edit this novel, I realize there is a problem wit this: in the eye of a hurricane or typhoon on Earth, air is actually *cold* and traveling *down* due to the fluid dynamics of how hurricanes are generated and work. Hot air rises all around the eye, contacting the cold layer above it and precipitating the stormwall as it goes. Thus my city really needs a hurricane flipped on its head, so to speak, so that hot air is rapidly rising through a tight eye-like hole, breaking through some kind of large cold upper layer.
My planet has Earth-like temperature, atmospheric composition, pressure, and gravity about halfway down in its atmosphere, where the people live. Above this is a large, sparse layer of helium and hydrogen. Below it is a large, very dense layer of carbon dioxide, carbon monoxide, and lesser amounts of other dense gases and vaporized particulates. Below that the world-ocean's surface is subject to rampant greenhouse-gas effects, its temperature perpetually on average being near boiling.
Is there a way to explain a flipped hurricane type of storm system on my planet?
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The closest weather form I can find is the [Anticyclone](https://en.wikipedia.org/wiki/Anticyclone) caused by
a warm high pressure system.
Interestingly most gas giant 'spots' are anti-cyclones (we can tell by the rotation direction).
<https://en.wikipedia.org/wiki/Anticyclone#Extraterrestrial_versions>
These type of weather patterns on Earth are much more diffuse than a hurricane or cyclone. You would need some form of constant unmoving heat source to make any kind of constant large weather form. On Earth they normally form over warm land masses.
If your planet was a water world with a small continent (possibly volcanic for added heat generation), this might form a semi-stable large anticyclone directly over the continent.
Even given this unlikely weather system forming, it would be unlikely to support a city from it's updraft winds. In hurricanes the higher wind speeds are in the horizontal direction around the storm, with the average vertical wind speed of only [4.2 m/s](http://weather.ou.edu/~hblue/metr6413/Blacketal94.pdf) ~10 mile per hour. This light breeze isn't going to hold up a city.
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You may need to do a lot more editing.
Large Gas giant planets like Jupiter and to a lesser extent Saturn have such a large standing column that the pressure under the atmosphere is enough to compress hydrogen into a metallic solid. Even "Ice Giants" like Uranus and Neptune are thought to have some pretty exotic physics and chemistry going on deep below the atmosphere.
[](https://i.stack.imgur.com/DCwvK.jpg)
The reason I mention this is most gas giant planets have a core which radiates more heat than the planet receives from the Sun. This factoid will certainly drive "upside down" cyclones and any other sort of weather you can think of, so you issue of riding updrafts is easily solved.
Of course, if the core is liquid water, then the problem becomes far greater.
First off, the water will only stay liquid in a very narrow range of temperatures and pressures. It is actually thought that "Super Earth" planets might have oceans a thousand kilometres deep, but much of the water far below the surface will have been transformed into one of the multitudes of [ices](https://en.wikipedia.org/wiki/Ice) that water assumes under different pressure regimes.
Secondly, a Gas or Ice giant planet is far larger than the Earth, which explains the ultra compressed core and heat radiation coming from it. Even Ice Giants like Uranus and Neptune are large enough that their cores radiate the heat of formation, even after 4 billion years.
[](https://i.stack.imgur.com/KZ0ci.jpg)
Finally, the radiation environment is going to be pretty intense inside and even in orbit around gas or ice giant planets, so your intrepid settlers will need to be in pretty heavily shielded habitat modules as well.
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**Tidally lock your Super Earth and give it a Super Storm.**
You mentioned that your planet is mostly water. If you tidally lock your planet to the star, one side will receive all the sunlight while the other remains cooler (but not frozen).
Directly at the spot on the day-side that receives the most sunlight would naturally reside a Super Storm, sorta like a juiced up endless hurricane. Now this would get us our desired storm, but how do you float a city on it? Especially one like you described?
You have a couple of options.
1.) You extend the tips of the city into the eye-wall on all sides. With a Superstorm and its winds of possibly 400mph or greater there should be plenty of lift to overcome the city weight and the meager eye downdraft. There would be some hurdles to overcome however.
Hurricanes commonly go through eye-wall replacement cycles in which a new eye-wall springs up inside the outer regions of the eye. These would have to be dealt with extendable arms that could adjust for rapid changes.
Superstorm meanderings and orbital cyclones: Does your city have the ability to move on its own power at times? How well does it do if one side is receiving more torque than the others? With other low pressures (or even other full fledged cyclones) orbiting around the central low your city would need to be able to handle severe turbulence.
These hurdles are not impossible to overcome; your city just needs to be designed with these in mind.
2.) You use the cold descending air to create the galaxies best hot air balloon city.
Fill your city with large amounts of hot air containers. Like a hot air balloon, hot air will want to rise in respect to cold air. The greater the temperature difference (the lower the internal air pressure), the more the effect.
This would allow you to stay above the turbulence of the storm, bypassing most of the previous hurdles.
**Things you should know**
Only **low pressure storms** create eyes like the one you are describing. The eye is created by centrifugal force as their fastest winds are found **right outside the center**. The exception to having the strongest winds in the center are the extra-tropical storms. However, their eyes are not stable over long periods and 1are far more rare.
**High pressure storms** such as Jupiter's Great Red Spot and our high pressure zones on Earth feature their strongest winds on the **outside edges**. Hence no eye.
So if you want a storm with an eye it needs to be a low pressure storm. Flipping the direction of the updraft to a downdraft would not give you what you desire. It would turn what looks like a hurricane, into a vast area of sunny weather surrounded by showery bands of thunderstorms on the outside. Turning just the eye downdraft into an updraft also wouldn't work. Even if you somehow ignored the effect of centrifugal force, an updraft would condense into a cloud, rain, and storm. No eye. It is the downward moving air that cuts out the clouds in the eye so we can see it. Without it the storm would have a very cloudy and foggy mess for the eye.
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So I was working on this concept for a sci-fi story and in this universe it uses a "warp" drive.
The Genesis Field is a supra-dimensional field that causes spacetime to be created or destroyed (explaining dark energy), based on the pole of the field. This field used in an interstellar drive works much like the "Warp" Drive but it would not be called a warp drive. Basically it destroys space in front of it and creates space in back of it. Matter is not destroyed though. Matter that is in the space that is destroyed moves probabilistically to the space that was in front of or behind the space that was destroyed. If the matter is in the space being "grown" the matter moves in much the same way.
Here's my question. In space, the density of matter is low enough to not cause a problem because any matter that gets into the field would not be enough to collect (at least I don't think so) and cause a problem either exiting the field at a rate equal or greater than the amount of matter that would enter. However, in an atmosphere this field would have all that air in it already and entering it from when it's traveling...
What you have then is the field is moving forward at or above light speed with all the matter that was in it coming with it, creating an empty space where it was while simultaneously you have some of the air from where it moved to is moved to inside the field, assuming it's half in/half and half the volume of the field is filled with the ship, then the density of the air doubles... while, again, simultaneously half the air from that volume it just pushed into is being moved forward possibly with a seeming velocity of c and this is all done at the speed of light. And then this is done continuously for whatever length of time the ship is in atmosphere or using this drive.
What would the effect of this happening be? Since the air displaced by the field is not getting energy from this "move" I'm of the thought that any air that gets brought into the field would get just sorta start gathering in the front of the field.
So to clarify, there are sorta 3 parts...
1. What is happening to the empty space left behind? Would air be rushing in? Would something like that be dangerous to Earth?
2. What would the effect of the air density in the front of the field increasing so fast be?
3. Similarly what would the effect of all that increase density air being pushed forward, but not having "energy" imparted into it be?
When I first realize the consequences of this idea in an atmosphere my guess is that it would possibly cause the air to ignite, but I have no idea.
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Edit: There seems to be misunderstand from the 2 answer received. When the Space in front of the field is destroyed, the matter isn't so there needs to be someplace that it goes. This being the case it moves in any direction from where space was to where it is, to the closest it can reach. The result is not that half the matter moves to the other side of the ship's field, but rather goes inside the field, to the bubble volume that the ship is in.
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It actually works out much better than you would think.
Let's work through what happens little bit by little bit by looking with our infinity-frames-per-second camera (it's made from unobtanium and the film is handwavium, shush). We're going to cheat with the units a bit though - we're working with a small prototype, so it's only got a surface area of one square foot. Also, the normal density of air has been tautologically redefined to be measured in units of normal density of air (one per cubit foot) (by density, here I mean the number of of particles per volume, not the standard definition).
We start at time zero. The ship is there, the field is there, the air density is the same (one per cubit foot) at all places around the field. No space has been created or destroyed. All is normal. Time to skip ahead by a fraction of a nanosecond.
Time one. The ship and field have moved forward by one foot. A cubic foot of space has been destroyed and recreated at the back. Statistically speaking, half of the air in the destroyed cubic foot stays in front of the ship (therefore the air in front of the ship has density 1.5) and half is moved to the created cubic foot (which then has density 0.5).
Time two. The ship and field move forward by one foot. A cubit foot of air is destroyed and recreated at the back. You get the idea. Again, half the air moves forward and half moves to the back. The back cubic foot has density 0.75, and the front cubic foot has density 1.75.
Time three. Same deal. The back cubic foot has density 0.8.75, and the front cubic foot has density 1.875.
Skip ahead, time eight. The back cubic foot has density 0.996, the front has density 1.996.
At time ten we're at 0.999 and 1.999 respectively, and I'm just going to stop there.
See, what you have here is the magic of limits. Since your Genesis Field basically works by continuously halving whatever matter is in front of you, you're never going to get a major buildup that gets out of control. The amount in front never reaches above double the standard air density -- which makes sense, if you think about it. You're halving whatever you have in front and adding one, so as long as the amount you're adding is less than one, you're never going to reach two.
So then in the back, you're going to have 0.5, 0.75, 0.875, .... 0.999, 0.9999,...... Almost, but not quite, reaching standard density. The less dense air at the back would be (relatively) slowly filled in by the surrounding pressure.
So all in all you'd be fine using this in an atmosphere. Yes, you're doubling the number of molecules in the air in the space in front of the field, which would double the pressure, but that's still less pressure than [is in a bicycle tire](https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)) (scroll down to the 100 kPa range).
TLDR, bicycle tires exist, therefore your warp drive won't blow up the atmosphere.
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This is a bit tricky to through because some of the concepts are slippery to deal with.
Firstly, spacecraft in your story use a Genesis Field (GF) drive to 'move' at lightspeed and above. Space is destroyed in front and new space is created behind the vehicle. Somewhat like an Alcubierre metric drive, but instead of contracting space in front and expanding it behind GF ships create and destroy space (presumably in accordance with a conservation law applied to the nature of space). Secondly, matter caught in the forward lobe of the GF isn't destroyed along with the space it reappears half and half in both the forward and rear GF lobes respectively.
Note: a GF ship have any momentum or velocity with respect to its 'motion' due to the GF travel. It will retain whatever state of motion, momentum and velocity it possessed when the GF drive was activated. GF travel is more a matter of space rearranging itself, so a GF drive vessel is undergoing a continuous process of repositioning itself with respect to the rest of the universe.
Let's just do a little thought experiment. A GF ship is cruising through the solar system at twice lightspeed. Its course will take through the upper atmosphere of planet Earth. We will assume its passage through Earth's atmosphere is a chord three thousand kilometres long. At twice the speed of light the GF drive vessel will only take one-two-hundredth of a second to traverse its course through the Earth's atmosphere.
Half the matter in the air along that traverse will pile up in the front GF lobe of the ship. While the other half of the air will be distributed along the traverse through the atmosphere. This means a high pressure will form on the frontal area of the GF vessel in one-two-hundredth of a second, this will be more like a burst of pressure but this will dissipate into the vacuum of space. Depending on the pressure involved this might be like an explosion and there could be damage to the frontal area of the GF ship. Air pressure and density along the path of the GF vessel through the atmosphere will be halved. Also, half the mass of air along that traverse will be carried off into the space.
This is unprofessional conduct by the captain of the GF vessel. He or she should expect a severe reprimand and have to face a disciplinary tribunal. No self-respecting planet wants to have space vessels removing chunks of its atmosphere. The atmosphere won't blow up, but illegal depletion of planetary atmospheres should not be encouraged.
Most of the effects will depend the rapidity of the 'motion' or the pseudovelocity of the GF ship. It will be subject to the planet's gravity, so it won't want to linger. Mostly you expect possible damage to the ship from the sudden pressure increase and loss of atmosphere. Plus the repercussions from the owners for damaging their property (including costs of repairs) and planetary authorities who object to the loss of atmosphere.
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You now have an explanation why spaceships do not enter planets atmosphere using their FTL.
Going off of [John Robinson's wonderful answer](https://worldbuilding.stackexchange.com/a/46594/96965) the air pressure in front of your ship will approach (but not reach, unless the ship travels an infinite distance inside of a 1 Pressure atmosphere) 2 atmospheres of pressure. Which is problematic for cities, will shatter glass, etc.. This will create a shock which will be capable of destroying even extremely heavily reinforced concrete structures, produce a wind speed of close to 502 mph [According to the CDC](https://www.cdc.gov/niosh/docket/archive/pdfs/niosh-125/125-explosionsandrefugechambers.pdf), and have fatalities approach 100% (the human body is surprisingly tough, the majority of deaths will not be due to overpressure, but due to collapsing buildings, and hurled debris). This is if the ship survives long enough traveling down the atmosphere to effect a city. Which depends on the effective speed of travel thru realspace, as if it is fast enough, it is possible that a ship could punch thru the middle of a star before the matter that is captured by the ship propagates thru the bubble of space sorounding the ship.
The space time bubble surrounding the ship (assuming the ship moves fast enough that the amount of air escaping from the bubble is negligible) will slowly increase until the ship is crushed by the pressure. As every ship length the vessel travels thru atmosphere the space bubble adds .5 atmospheres worth of air near the front of the ship.
Looking at this further, it might mean that ships are required to perform microleaps while traveling to prevent a dangerous buildup of a pressure front inside of the ships travel bubble.
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I have a race of carnivorous mammals (the same from [this question](https://worldbuilding.stackexchange.com/q/2498/1971)) for whom blood plays an extremely important role in cultural rituals. For complex cultural reasons, a member of this race (call him Fred) decides it's a good idea to preserve a few milliliters of his blood so that another member of his race will be able to perform a ritual using it several centuries later, at which point the main body of my story takes place.
The obvious problem is that blood doesn't last for centuries, so when Mr. Hero-of-the-story finally finds Fred's body, he'll have nothing to drink but a bit of brown dust. Hence, my question:
# How can I keep a sample of blood recognizable after being stored for centuries?
By recognizable, I mean the blood must:
* Be liquid.
* Be a reddish color.
* Have a taste and smell that at least resemble blood, although they may have changed noticeably. It can have acquired a sour or "aged" aspect, but shouldn't smell like lilacs or gasoline. These are a very animalistic people and having it smell and taste right is going to be extremely important if the ritual is to respected.
* Ideally, change from a dark red to a bright red upon being exposed to the air, although this isn't strictly necessary.
The blood does NOT:
* Have to be actually have to be functional as blood; it's going to be ingested and digested, not infused.
* This means gas transport doesn't matter.
* It doesn't have to contain any living red or white blood cells.
Solutions involving some sort of preservational chemical additive are acceptable (this race is generally pretty backwards when it comes to technology but they have an almost alchemical aptitude for applied chemistry with minimal equipment). However I'd prefer some sort of container that could maintain the blood without a need for additives.
When Fred preserves his blood he is on the brink of death, alone in a distant corner of his realm. At his disposal, he has:
* An unrealistically powerful and portable array of chemistry equipment.
* Salt water.
* His own body.
* Sand and dust.
* Anything appropriate to his people's level of technological advancement that he can be reasonably carry on his person through a many-week long journey through a desert.
Available technology is very limited. Refined metals are not available as construction materials but they are available as chemical compounds (so having pure platinum as an ingredient in a formula is okay but an iron cannister is not). Microbes, naturally occurring compounds and animal parts are fair game, but there needs to be a good reason for them to exist and be effective preservatives.
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Also worth noting is that this world is based in real-world science, there does exist one "magical" substance that, while still bound by physical laws, follows very different laws than known matter in our universe does. I don't want this substance to become a catch-all excuse for throwing realism out the window, so I don't want to say "Fred put his blood in a container fashioned out of Substance Plot Device and it froze in time" (elsewhere in universe this material actually breaks down most molecules so this wouldn't make much sense anyway). But if there's some critical step in your idea that you can't make happen using real-world chemistry, you can throw in this mystery material as a small ingredient in the bigger picture.
Edit:
I suppose it doesn't have to be a liquid while in storage as long as it's immediately convertible back to a liquid upon recovery.
If it makes any difference, it's going to be stored at extremely high elevation. Low temperature, moisture, and air pressure. No soil, but maybe a few handfuls of rock dust. And of course Fred's body, which I imagine will mummify.
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**If there are mountains in the area, or in the far north: freeze it.**
Assuming your race doesn't have access to cooling technology, one option would be to freeze the blood in an alpine area. Find a region in which the ground stays frozen near round and bury a vial of the blood in the permafrost. All of the cells within the blood will be destroyed by freezing, but it should retain its moisture content and its iron content, which will give it a blood-like flavor.
**Option #2: preserve the blood in alcohol.**
Another option would be to use alcohol to preserve the blood. Create a mixture of 70-90% alcohol, with the rest being blood, and store it in a sealed container. A 70-90% concentration of alcohol will be enough to kill any bacteria living in the blood, which should prevent it from rotting over the intervening millennia. Some bacteria are alcohol resistant, so you should also boil your blood/alcohol mixture in a pressure cooker to provide additional sterilization.
After the blood sample is recovered, your scent-sensitive carnivores will need to remove the alcohol from the blood. Luckily, alcohol evaporates readily at temperatures below the boiling point of water. Since your blood is mostly water and some solids, you can boil away your alcohol to leave a biologically inert but mostly still there sample of blood, which you can drink. Then you can drink the alcohol you've distilled out of the blood in the process of purifying it and call it a party.
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I'll start with a couple disclaimers:
* I am no biologist, chemistrician, nor biochemist;
* this involves so much handwaving that your wrists are going to hurt;
* if anyone finds correctable flaws in my science here, feel free to edit my answer or refine it into a new one. I'll upvote you if you improve on my idea.
First, mix the blood with distilled water. The red blood cells are literally going to pop, because water will rush in due to osmosis. Now centrifugate it (I am no native speaker and I don't know if "centrigugate" is the proper term). Throw the topmost, pure water phase of the result out. Sterelize what's left.
Now is where biology and chemistry teachers will want to kill me. Crystallize whatever's left. You may start with a quartz seed, and then you add silicon dioxide to make it grow. You'll need a catalyst to make the crystal grow fast (fast as in minutes or hours instead of millenia).
The crystal will envelope your important blood content. It should not clot, since the plattelets are gone, but it may go from red to black die to the concentration of iron going way up. It will look like black, or red patches of impurities within the crystal.
Now I don't know how long a quartz rod will last, but I am sure it will last orders of magnitude more than what you want.
To recover: break the crystal VERY carefully. This may require some microscope and micro drills... But a thousand years is a lot of time for technology to advance. It should allow this. After you break the crystal, mix the payload with water. It will become brighter and "redder". You may now drink it.
Last but not least. Document what you've done. You don't want that crystal ending up as an ornament or new age healing tool.
P.s.: red blood cells carry no DNA an whatever traces you get from a few white blood cells in the mix will spoil over time, even inside the crystal. DNA chains will become useless for reconstruction with this method. Just a reminder and food for thought.
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# Thousands-Of-Years-Old Blood
Without reading the other answers (for time's sake) I'd say that you *could* feasibly preserve just about *anything* in an airtight container or room *-even a body-* for hundreds or thousands of years. Were it just the **DNA** that you needed. it's *possible* that this *may* be intact after massive amounts of time, even dried and in dust form. But I think that's going to be a percentage chance and lower and lower with time and environmental variables.
Were you going with the airtight container, being able to remove oxygen from the equation would help. A vacuum sealed vial, say, ***better yet***, AND/OR...in a cold cavern beneath this desert, sealed off from the light and air by a collapse? Perhaps your hero, anti-hero, or whatever "**Fred**" is can be led to this location by a note or map, or even a tracking-device with an audio recording or hand-written message, if ancient or lost technology is an option.
*And* if this technology is available, then *many* things are possible, especially if this is from an advanced race, or a time-line far advanced from our own.
The cave scenario works, I think, because scientists have recovered dna from just blood-stains over a hundred years old. There was a show just last year that matched DNA from a scarf obtained over a hundred years ago during the Jack-The\_Ripper investigations in London at one of the crime scenes, and they were able to match it to some people. That shows that, despite the worst, uncared-for conditions, not all of the DNA had degraded. There were enough of the cells left to identify people. But in caves, on mountain-sides, in air-tight tombs, frozen in ice, bodies have been discovered -fully-preserved. (in the frozen case, sometimes as viable as if they'd just died, with far less cell degradation than scientists had even *dreamed*. I.E. The Wooly-Mammoths, over five thousand year old "Otzi-The-Iceman" found frozen in The Alps, The 500 year old perfectly preserved Incan maiden, found in a buried mountain chamber. She was so well preserved, she looked to have just died. Her arms and hands look alive. they have her on display. there are other examples of mummies found buried in the desert, in caverns, in bogs, in ice, etc. But I digress a wee bit, because you asked about blood specifically.
I mentioned all of this because it shows the possibility for preservation beyond what was once thought possible. Scientists have stated the life of dna at something like 500 years, but around a million or so, given the right circumstances. Do your research to get the right number on that as I'm only *close*. Even so, viable DNA has been obtained from prehistoric samples *much* older than a million years.
DNA *does* break down over time, however, -due to bacteria and other variables, which is where your technology, *-and maybe **just** the right addition of circumstance and location-* comes in. I.E. cold,subterranean, air-tight chamber, air-tight vial of blood, some technology... perhaps just something added to the blood to stop progress of and/or kill any bacteria and preserve it in its liquid form. That would probably be the most simple option. Or even the body itself could have some gelled blood, possibly mostly useless, but smelling enough in the dark chambers that haven't been exposed to air in thousands of years to lead your "Fred" to the body and the vial, or other container. hell, you could even have the S.O.B. have chopped off a digit of his pinky finger and placed it in a capsule-like device with some kind of circulating apparatus on it to keep blood flowing nearly indefinitely with some kind of added futuristic chemical that keeps the blood fresh. The purpose of this would be to use the digit to clone him when he was found, but maybe that technology is lost, or maybe that was what you had in mind. Maybe his memories are stored in a chip on it, or they're stored in the blood if your "Fred" is a vampire or something like that.
*Anywho*, hope I have been of help. This has been a fun few minutes away from what I was doing. I reserve no rights to anything I've typed, obviously. (except obviously reposting the whole thing as an article or something somewhere and claiming it as your own, because that's just lame.) Be inspired, copy and paste parts, or ignore it, but *hopefully* you found it useful.
P.S. As an after thought. In that last scenario, with some kind of technology to preserve part of himself or a sample of blood, there really is no need for any kind of temperature control or protective environment, as long as the device is safe. The corpse could be bones nearly turned to dust, half buried in the desert sands, in the shade of some large rocks or something, as long as the device was safe, or tough enough to survive the time and weather and anything that may have come along. The trick is how he *smells* it.
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The easiest thing to relate the creature itself to is a mixture of an armadillo and a bear. It's a large animal with essential physiology similar to that of a Spectacled Bear and large plates of interlocking armored shell along its back and partially down its limbs and head. Its skin is a light grey and covered in rough, almost translucent hair.
The environment is the intersection between a large dune-based desert and a type of Hamada desert consisting of broken stone and natural rises/outcroppings. There are natural water sources, both above and underground.
I'm wondering whether it makes sense for such a creature to exist wild in this kind of environment and what kind of behavior it could have as a result.
(Preferably science based but open to options)
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I think it's safe to say armadillos aren't the only armored creatures in the desert. Tortoises, carapaced beetles, scaled reptiles. So armadillo bear is reasonable assuming its lacking the fur and fatty insulation that its bear cousins would be known for.
Fair to assume that, like both a bear and an armadillo it would be omnivorous. Can't be picky in the desert. Maybe, being essentially a very large armadillo, I could picture the local insect-life being much larger too. Perhaps they have a favorite foot long grub worm or beetle they feast on? If there are underground water/caves I could see these creatures hibernating much like bears, but perhaps during the summer instead of winter to avoid the very hot instead of very cold. Armadillos are built defensively burrowing and hiding, not to fight. So I'd wonder how you would approach their demeanor. I'd imagine reserved rather than aggressive.
Fun idea.
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I'd have to say **maybe.**
Natural armor, from a survival standpoint, is useful to protect from predators. Would there be any creatures preying on this theoretical armadillo-bear?
If so, then yes, it would make sense to develop a naturally hard coating for defense. However, otherwise, it'd be simpler to develop something less weighty, to be able to catch prey faster.
If it was a thin coating to protect from, say, desert storms or what have you, then that would be a decent middle-ground.
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Would something like the [Thorny Dragon](https://en.wikipedia.org/wiki/Thorny_dragon) meet your criteria?
It also has a trick to gather water using it's skin <http://www.asknature.org/strategy/3f47ec0d4343c94f82e19e103ac20c34>
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Those actually exist. For example, many scorpions live in the desert. They are prettymuch 100% armor-plated. Consider *[Hadrurus arizonensis](https://en.wikipedia.org/wiki/Hadrurus_arizonensis)* (Arizonian Giant Desert Hairy Scorpion):
[](https://i.stack.imgur.com/u9xRb.jpg)
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> Hadrurus arizonensis is distributed throughout the Sonora and Mojave deserts.
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I know there are questions similar to this, but I'm not very scientific minded, and wanted to check with you guys how this would work exactly. I don't care what else I need to add into the equation to make it work. (like more planets, size or distance changes, etc...) As long as it can, plausibly, work.
Large sun as the main mass of gravity/pull (please excuse me if I get terms mixed up), a couple of uninhabitable orbits/planets in close orbit.
Then the first large habitable planet in my crappy drawing in its own orbit - a bit larger than earth so the gravity of that planet would be similar to ours. For that matter - how large could I make that planet and have it still relatively similar to earth?
Then a second orbit with three smaller habitable planets in rotation (again, only slightly smaller than earth, so the gravity would be similar to ours) though I don't mind if I have to make one of them bigger, as long as its still habitable, if not, I'd need to add in an additional uninhabitable planet.
This would mean that the large planet and the three smaller planets would have to each line up at one point. Like the first answer in [this](https://worldbuilding.stackexchange.com/questions/36822/twin-tidally-locked-planets-non-rotating/36831#36831) post. (though I don't understand half of Michael's answer, hence why I'm asking again, and with more specifics to my problems) My planets would be far enough away from one another though that I wouldn't have to worry about gravity pull or collisions.
Ideally, I would want all four planets to share the similar species. I know that the lone planet, being in a different orbit, would function quite differently, and create different species - but would there be a chance of anything human like with human intelligence?
Similarly with the planets sharing an orbit, would they have a better chance of developing/evolving the same, since they are in the same conditions?
I suppose something to ask on that front, would it work if a large early-stage planet (obviously no life form or anything on it yet) was pulled to the sun, and then somehow broke into three smaller rocks which then created the three planets (or the four, if that could work, the forth being pushed into that first orbit, away from the others?) At least then each world would have been started with the same materials, and then maybe the evolution would be similar - I mean, humans evolved with minor differences on opposite sides of the world? so it could work?
Solar Eclipses are actually a bit important in my story, how would they be affected by this situation? Especially for the smaller tri-planets? EDIT.
What I mean by this is, the tri-planets would still view an eclipse the same as we do, yes? So once or twice a year?
But the lone planet might view them more times a year, as three planets are on the same orbit one orbit away from it?
And then beyond from that second main orbit would be more uninhabitable plants in more orbits, etc..
NOT TO SCALE. I don't care how far away the orbits have to be, as long as the planets are habitable.
[](https://i.stack.imgur.com/wHaQA.jpg)
I'm sorry if I'm confusing guys, thanks in advance for your answers.
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I think you would be best having multiple planets that are gravitationally locked with one another as in a planet/moon system. A prime example would be Pluto and its moons (largest Charon). Charon is so large when compared to Pluto that Pluto doesn't completely command it gravitationally...Charon actually drags Pluto around as well. The result is that the two (as well as the other moons) all revolve around a void space between them whose location within the system is based upon the relative masses of the bodies. The spot that is the center of the system would be closest to Pluto since it is the largest of the system and commands the greatest amount of gravitational pull. The net effect is that the Plutonian system orbits the sun and Pluto seems to wobble (as it is orbiting the Plutonian System's center of gravity). Eclipses of the sun and each other would be common as the bodies would be very close to one another. The effect of seeing "moons" that were of this type would make them appear in the sky several times the size of the host star. Nights would be twilit often times due to reflected light of the other planets. One thing to consider would be how close would be considered too close...if they were too close together, their gravity might cause collisions or they might tear each other apart (that might reduce the size in the sky and amount of reflected sunlight). Lots to research and consider before attempting...tides would also be wild...
As to the prescience of life, if they were in the habitable zone and all had the requisite elements/conditions, it would be more alarming if only one had life while the others didn't. There is a theory that basic life may have "seeded" Earth millions of years ago from elsewhere (Mars?!?) and that it was ejected into space through a collision which later fell onto Earth within space rocks. Some of the theory holds water when you add I. That meteorites on earth have been found to have Martian origin. So ultimately, microscopic life that develops one one would easily traverse and seed the others in a system. Keep in mind that such an event would be highly devastating to the planet of origin and life on it (the impact would have to be great enough to send rocks into space and would likely be considered an extinction event). Life on the planets would evolve separately (with the potential for some microscopic aliens from time to time) and would result in different species on each planet. Also keep in mind that cosmic events would likely affect each planet unless one or two were shielded by the others.
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Gravity has very strict rules and as others have said, your ideas are impossible.
It is possible, though it's rare, to have 2 planets sharing an orbit. See [here](https://www.newscientist.com/article/dn20160-two-planets-found-sharing-one-orbit/), but never 3. Earth and the mars sized [Theia](https://en.wikipedia.org/wiki/Theia_(planet)) are thought to have shared an orbit for a time. But co-orbitals work best if they're not pulled about by neighboring planets so you'd want those to planets to have lots of space on both sides. Your larger planet on the inside of those two and not far away. That's also wouldn't work.
The co-orbitals has to be at specific orbital distance too, which means, no eclipses and just a dot in the sky. Not very interesting. A permanent morning star for one, a permanent evening star for the other.
There's no way to do what you propose with 4 planets.
The most impressive planet viewed from another planet is Earth, viewed from Venus, though Venus has clouds so it's a terrible planet for star gazing, but if you could see stars from Venus, Earth would look quite impressive.
If you want an interesting visual with 2 planets, where they pass relatively close and perhaps have the occasional eclipse, try something like [this](http://www.omgfacts.com/nerd/15832/Saturn-s-Moons-Orbit-So-Close-They-ve-Learned-To-Switch-Orbits-So-They-Don-t-Collide). Two planets can share similar orbits and swing past each other every few years. That's perhaps not stable on the scale of hundreds of millions of years either, but it's almost arguable.
Two planets orbiting around each other is possible too, like the Earth-Moon system. That's rare that two planets would do that, but theoretically possible. Both planets would have large tides though and you could have fairly regular eclipses.
The problem with 3 or more is, you can't have 3 planet sized objects in relatively close orbits. There's too much instability with three. Two kind of works though, but the 3rd would need some sizable distance.
@JDługosz you mention L3 and L4, the only stable Lagrange points are L4 and L5. You can have a 2 planet system 60 degrees apart from each other, the planet that's ahead is in L4 to the planet that's behind and the planet that's behind is L5 to the planet that's ahead. This is stable provided there are no other near-by planets and provided that the Sun they both orbit is measurably larger than the 2 planets.
If you add a 3rd planet and all 3 are equal sized, then the first and last planet are in L4 and L5 to the center planet, but they are 120 degrees apart from each other and that's the problem, if they're both equal size to the center planet, they would attract each other at 120 degrees and the saddle points would both become unstable. You can only have objects in both L4 and L5 if they are both comparatively small, or you can have 2 comparatively large objects, but not a 3rd. (I looked, I couldn't find a reference to back this up, and I can't do the math, but I know it to be true and it's logically consistant. The Trojan saddle is quite narrow and the two fairly large objects at 120 degrees from each other in the same orbit would gravitationally attract each other.
[](https://i.stack.imgur.com/CAJCs.jpg)
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# This setup cannot work
Lots of stuff, but here is where it falls apart. You say:
"all four planets to share the same [species]"
...and...
"Solar Eclipses are actually a bit important in my story".
If the planets are that similar in size... and so close they can eclipse one another, then the orbits cannot be stable. This system will fly apart, even if you "imported" planets.
In order to make this work you need magic to hold this together, or have it be an artificial, simulated system.
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The problem with the setup as described is the planets will gravitationally interact and kick each other out of their current orbits. You can see this in our own solar system, many planets or moons in the Gas Giant systems orbit in resonant periods with each other, since this provides stability.
When planets are in non resonant orbits, the best way to think of what happens is to think of a man pushing his child on the swing. If he pushes the swing correctly, the child will rise higher and higher, while if not, the swing could come to a stop. Planets "passing" each other in non resonant orbits will interact gravitationally and deliver much the same effect as the man pushing the swing.
Needless to say, being flung out into interstellar space or dropped into a close orbit around the sun will wreak havoc with the planetary biosphere and make much of the rest of your story moot as well.....
Without commenting on the plausibility of all the planets on the habitable zone sharing the same sort of biosphere (maybe they were all settled and terraformed by colonists from one single planet), the best way to get the effect I think you are looking for is to have a much larger star as the central sun, and have the planets in 4 separate orbits with the proper resonant periods so they do not fling each other out of orbit. This will take some calculating power (starting with the size and luminosity of the sun, which defines the habitable zone), and the planets will necessarily have long "years" so eclipses or transits (given the distances, a transit of the sun is far more likely than an eclipse) will be decades or centuries apart, depending on the planet.
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Your setup is fine. 2 planets can share an orbit. The most stable setup is for them to be 60 degrees apart (technical term: in each other L4/L5 points). And there is plenty of space for multiple orbits within the habitable zone.
I've written a series of blog posts about how to design a planetary system. The main page is here (with links): <https://planetplanet.net/the-ultimate-solar-system/>
You will be specifically interested in these two posts:
1. Orbits (with 1 planet per orbit) <https://planetplanet.net/2014/05/21/building-the-ultimate-solar-system-part-3-choosing-the-planets-orbits/>
2. Moons and co-orbital planets: <https://planetplanet.net/2014/05/22/building-the-ultimate-solar-system-part-4-two-ninja-moves-moons-and-co-orbital-planets/>
Hope this helps.
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In an alternate Earth (or even in a pos-exctintion future), suppose **intelligent but primitive** **humanoids 1/10 the size of humans** inhabit the planet. They don't coexist with current humans or have access to any previous technology.
How difficult would be to these small humanoids to achieve an **equivalent** **technology** and society level comparable to us? I'm going to focus this question in the following:
1) **Food** and **water** supplies, basic **tooling**, **wheel**, **fire** and **agriculture**;
2) **Energy** (water/windmill, steam, electricity, solar);
3) **Long distance** (transporting, navigation, communications, Internet, space travel and moon landing).
I suppose this is now a new concept in the fictional world, so if anyone could guide me through some work related to this question, I would really appreciate.
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Early on, we'd have trouble with large predators, but history has shown enough times our willingness and ability to go toe-to-toe with much larger animals and wipe them out of an area if they pose a danger to us. Between fire, traps, and weapons, if we're capable of taking out whole herds of mammoths at our current size for food we'd be just as capable of killing proportionally mammoth-sized wolves and the like for our own protection.
Domestication could be interesting. The animals that are easiest to domesticate are herding herbivores. Cavies, hamsters, and similar rodents live in groups and could replace our sheep as a grass-eating source of meat and milk, but while sheep are migratory, rodents often live in burrows. This might lead to earlier farming and fewer nomadic human groups. Some of the larger burrows might even become repurposed for human habitation. On the other hand, we might just go and domesticate sheep and cattle anyway. We managed to domesticate elephants, after all. Dogs could be trickier - wolves would be too prone to viewing us as snacks, so we'd probably kill them rather than ally with them. Some crazy person might manage to tame them at some point, but they probably wouldn't be man's best friend in the stone age.
One interesting possibility that might greatly change things is the ability to domesticate and ride large birds. If we could pull this off, travel would become very different, very early.
Beyond our relationship with animals, life probably wouldn't be much different. Natural non-biological landscape obstacles tend to be distributed on a logarithmic scale, so while the tallest mountains would seem taller and the widest oceans would seem wider the structures we dealt with on a daily basis and the distances between them would feel about the same. This means that the wheel would be just as useful; our roads would be narrower but we'd have to clear out the same amount of material proportionally to make them. The square/cube law might make us able to travel proportionally farther in a day on foot so cities might still be spaced out about the same as ours are, but by the same measure it would be easier to clear the roads by hand so the pressures would balance out.
We're already way out of our league when crossing seas, so we'd probably manage to do it in about the same time period. We might start out with proportionally larger boats, which would mean larger groups of people settling in new regions, but not to the extent that life would be significantly changed.
The more we advanced technologically and shaped the natural world to our own whims, the more things would start to resemble our own world. Most high technologies would either work just as well on small scales or we'd compensate for physical limitations by making them proportionally larger. Airplanes and rockets might be a little easier since they would need to carry less weight. Computers tend to brush up against the very limits of physics so it would probably take us more time to develop high-quality smart phones.
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I know that there are many questions about where to go to actually build your own world, where you can actually be your own god, totally visualizing your world's geography, geology and climate.
But the thing is, my world is so similar to our Earth that it's not possible for me to rebuild a world from scratch. Are there any websites where I can find a map of the Earth and alter it in any way I wish?
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I'm a fan of procedural generation myself. For less of a hands-on approach to a unique map, a quick Google search for map generation reveals sites such as [donjon that offers tools for various types of generation](https://donjon.bin.sh/fantasy/world/). High enough in detail that it's easy to use as a baseline, yet somewhat plausible in general geography.
For actual earth maps, is the site [mapsofworld.com](http://www.mapsofworld.com/map-of-countries.html) high definition enough, or are you looking for more "realistic" looking maps? If so, maybe [topographical maps section in WikiCommons](https://commons.wikimedia.org/wiki/Category:Topographic_maps_by_country) is your source.
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Just an idea that occurred to me – if you wanted a world that was geologically plausible on a planet similar or identical to Earth, you could always use the geography of Earth at an earlier time period, or even Earth with a higher/lower sea level. This doesn't allow you to "alter it in any way you wish", unfortunately, but it *would* allow you to browse the various continental configurations throughout the Earth's life and choose the one you like the best.
Geography is a fairly different concern than geology, and you have a lot more freedom in this regard. You can probably draw a political map any way you like, as long as you account for certain reliable factors from human history such as civilisations liking water, political borders being demarcated by natural geographic features like rivers and mountain ranges, and powerful states having a preference for controlling their whole local landmass given the opportunity (e.g "Manifest Destiny" in the US, various attempts to "unify" Europe)
Some resources:
* [A Smithsonian Magazine feature on paleogeographic maps](http://www.smithsonianmag.com/science-nature/travel-through-deep-time-interactive-earth-180952886/?no-ist)
* [A mobile app illustrating some of the changes the earth has undergone](http://www.ancient-earth.com)
* [View Earth with different sea level](http://calculatedearth.com) (This one is better than others for our purpose because it allows entering crazy numbers, like a 1000m rise in the sea level)
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In the fourth and fifth centuries AD, the Roman Empire had fallen under bad times. Within its boundaries, the once powerful nation had been getting compromised by political corruption and civil unrest. The final straw were countless barbarian invasions, most notably one led by the Gothic warlord Alaric, who succeeded in breaching the city's gates and sacking the city of Rome. From there, Europe underwent a period of cultural stagnation and unrelenting war, a period stereotypically known as "The Dark Ages", before germinating into the Middle Ages which would blossom into the Renaissance and the Enlightenment.
But in this alternate scenario, the final nail in the coffin of Rome wasn't wave after wave of Eurasian tribesmen, but a volcanic winter coming from the likes of either of these choices:
* Yellowstone
* Toba
* Campi Flagrei
Considering that each of the three volcanoes had different chemistries and compositions, would the timeline of the Dark Ages and the Middle Ages be identical, or would the really bad weather change every aspect of European history?
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There seems to still be a [fair amount](http://www.livescience.com/20714-yellowstone-supervolcano-eruption.html) of [debate](https://en.wikipedia.org/wiki/Toba_catastrophe_theory) on just how severe the global effects of a super volcano eruption were historically or would be now. The greatest devastation is always localized, so the locations of your three choices matter quite a bit.
**Yellowstone**
A Yellowstone eruption, from the perspective of the Europeans, would most likely take the form of a few years of colder weather and low-yield harvests. This would certainly have an impact in the short term with some starvation and a greater tendency toward uprising, barbarian movement, or chaos, but the long term effects wouldn’t be too serious. North America and its inhabitants would experience some devastation, possibly leading to forced migrations southward. Thus the biggest difference would come during the age of exploration, when Europeans might find far fewer Native Americans occupying North America.
**Toba**
Toba’s distance from Europe is also substantial enough to lessen the direct impact of the explosion, but its proximity to Asia might have interesting effects. Similarly to Yellowstone, Europeans would probably experience several years — maybe even a decade or two — of much colder weather, but it’s unclear how severe it would be. Starvation and increased disorder would happen, but it’s hard to know how much it would affect Europe long term. What might happen, however, is a much earlier migration from Asia into Europe. If Toba’s local effects are devastating enough, you might see eastern invasions happening much sooner, possibly with great long-term consequences.
**Campi Flagrei**
Campi Flagrei seems to have less historically documented destructive power than the other two, but it’s definitely a more local threat. If it were to experience an eruption on the level of Toba or Yellowstone, you could feasibly see devastation on the continent. With severe ash fall throughout Europe and severe damage in Italy, there might not be a Rome left to sack. Now you might see migrations out of Europe, perhaps east into Asia and the Middle East or south into Africa. This would fundamentally reshape Europe for the rest of history, but how the changes look is really up to you.
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I am creating a Pangaea type continent for a D&D series with some friends and I was wondering (since this continent will last us years) if we should add every biome to it. IE: equatorial dry/wet season areas, polar, and wetlands, and everything else, or would it a better idea be to have smaller islands with the biomes that will not be visited anytime soon?
I am asking this from a logical perspective rather than a opinionated perspective. So please don't respond with an opinion, respond with how this would change the creation of the world and affect the various lifeforms on the planet.
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For the most part, you *could* have all the biomes if the supercontinent is properly positioned and aligned (i.e. if it crosses the equator and generally half is north and half is south of the equator).
The biggest problem is that the biomes will be in thin strips along the coasts, because the interior of the continent will be a huge, dry "continental" steppe. The interior will be so far from the moderating effects of the oceans, and indeed so far away from the oceans that moisture will mostly have evaporated from the air long before it reaches the central parts of the supercontinent. The vast majority of the supercontinent will resemble the steppes or prairies, surrounding a central desert which would make the Gobi desert look like a hospitable place for a resort.
The other "missing" biomes might well be mountains, since they are created by the process of uplift as various plates are driven together. If this is an older planet and the continents are reforming a supercontinent (for example the Earth of +100 million years in the future), then you will have your mountain ranges, but an older planet won't have the vigour of a "new" planet (the core is cooler) so your mountains might not be as impressive as the Andes or Himalayas.
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**Don't be shy.**
Fantasy world don't have to obey the common laws of physics. They need some form of logic, the most obvious breach of realism should get some explanations, but that's it.
So, you can have anything and everything, just remember Tchekov's Gun rule : talk about it only if it's useful. You can draw a broad picture of your continent, prepare a few answers for the most obvious questions and a couple locations with heavier background where you expect your characters to come from or to go tomorrow.
On the topic of Islands versus pangea, you have to consider the mindsets of the inhabitants.
It's hard to give a more detailed answer as the options are really opened.
Aim for believable, keep in mind how the inhabitants should be and you'll get something good.
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So here’s the rough idea. I’m trying to figure out what kind of life could exist that spends basically its entire life in the air, for an alien world I’m working on. No sentient life, just wilderness. In my mind, it’s not so much something that actively flies (like birds or planes), and lands in-between, but something that literally never stops flying. It is born, eats, breeds, lives, and eventually dies in the air. So my main questions are these:
* What would be necessary for there to be an actually functioning aerial ecosystem, and how complex would it be? Would it be similar to a ground ecosystem, or would it have to be completely different?
* What kind of life would it be? Plant, animal, fungi, single-celled, or maybe something else entirely? What is/would be best suited to life in the air?
* How would it fly? Would it be some sort of [living gasbag](http://tvtropes.org/pmwiki/pmwiki.php/Main/LivingGasbag), or something kind of like [spiders ballooning](https://en.wikipedia.org/wiki/Ballooning_(spider)), but on a much larger scale? Maybe something like a living glider? Or jellyfish-type propulsion? Is using magnets to float around in the geomagnetic field at all possible?
* How big would it be? Would it be one big organism, or a giant colony composed of millions of tiny ones?
* What would it eat? Would it have to go down near the ground to feed, catching low-flying/ground life, or would it catch other aerial life in midair? Could it maybe strain smaller forms of life out of the sky, like whales eating krill?
* How would it reproduce? Would it have a larval/seed stage on the ground, where it releases seeds/spores/polyps/eggs/larvae/whatever that fell to the ground, grew, then took off?
* How high would it be? It is confined to a certain altitude, or can it move around? Could there be life all the way up at the edge of space?
* What would be different about the planet itself that could help this happen? Would the atmosphere be composed of some heavier gas that could make it easier for other gasses to float? What about the planet itself having less gravity?
* What happens when the life dies? Does it go crashing down to earth, or just float around and decay, forming a place for new life to grow?
I think that’s pretty much it. I’m also interested in what possible mechanisms would be needed for life like this. Also, if there’s anything that just makes this whole thing blatantly impossible, then tell me so that I can hopefully handwave around it.
[Answer]
**The Gibble**
I created a species of flying creatures a few years ago. They're like a mixture of Blimps and manta rays. They are shaped like manta rays, and have an air sack they fill with gases like helium using special gill like filters. They use the appendages by their mouths to catch other flying prey (perhaps HDE's little pufferpolyp friends).
These creatures also fly in swarms, with the females in the middle. The babies grow on the mother's belly in a special clear sack. This means the females have larger air sacks; so they can carry their babies. The babies learn how the males protect the females, see their parents catch food, etc. Once they are fully developed and ready to fly, they either puncture the sack, or spit acid on it to dissolve it. I haven't decided which. Life goes on (for everyone but the pufferpolyps).
These creatures would have a lifespan of about twenty years, and they periodically refill their air sacks. Their filters can control the amount and type of gas in these sacks, to adjust the elevation the creature sides at. If they died of disease or old age in the air, their sacks would slowly leak and they'd drift to the ground. Or they'd be eaten by some other creature first.
While these creatures may look like manta rays, they are very different on the inside. Their bones would be hollow, their "wings" would catch up drafts, and their wingspan be more along the lines of three feet, instead of three yards. (Scaled down from actual manta rays.)
[Answer]
**Musca Turbela**
A type of fly that has evolved to swarm in large airborne "mats." A swarm starts when a number of flies find a piece of airborne matter. They latch themselves to the underside and keep it afloat through sheer numbers, feeding off of it, breeding, laying eggs, dying, pushing their waste and the newly-dead into the "anchoring mass," hatching, and continuing their quick life cycle. Eventually, the mass (and supporting swarm) is large enough to collect rainwater and support algae (and eventually some other flora). Mature mats would look like an airborne set of black-grey stalactites slowly and loudly hovering maybe 50-150 meters off the ground, surrounded by a cloud of loose flies and capped with some greenery (moss, tendriled plants that primarily catch moisture out of the air, various carnivorous plants). Birds would be attracted to these mats by the plentiful food, but carnivorous plants would be evolutionarily motivated to trap birds and provide food for themselves and the flies they primarily subsist on.
The planet in question would either have to have a rather hostile surface to drive these insects to make permanent residence in the skies, or have significantly lower gravity than earth to make this type of arrangement a convenient way to avoid ground-based predators.
[Answer]
**The Hindenburg Fish**. Pinnacle of aero-piscine evolution!
Fish have swim bladders that are currently filled with air in order to control buoyancy. The Hindenburg fish (through an unfortunate accident including a bottle of tequila and an electric eel) gained the ability to decompose seawater into oxygen (that it uses to supplement it's O2 requirements) and hydrogen (which fills the swim bladder). Now shoals of Hindenburg fish can be seen swimming along the coastlines of many countries, though they never venture too far from water sources in case they need more gas. Their eggs can be found laid in rock pools and shallow waters everywhere.
Their volatile nature has led to a whole new dining experience, known as 'Oh, The Fuganity!', where skilled chefs attempt to slice sashimi from the Hindenburg Fish without causing it to accidentally detonate in their diner's faces.
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[Question]
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I am building a Dieselpunk-ish science fantasy setting and for aesthetic reasons, I decided to make the [aether](https://en.wikipedia.org/wiki/Aether_theories) a real phenomena in the setting. Later I realized that aether could be a tool to justify space combat as commonly portrayed in space opera, [that is taking place at relatively slow speed and close range with big slow ships and small fast ones](https://www.youtube.com/watch?v=xPZigWFyK2o).
I established the properties of the aether in order to create the conditions for space opera style space combat.
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> The Aether is an omnipresent field of exotic-particles giving space a faint silvery hue. Aether particles flow from the aethereal plane into the material plane and back in an unending cycle.
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> Aether particles disrupt radar and radio/microwave communication, they also diffuse coherent beams making lasers and charged particle beam weapons useless.
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> Aether particles can also be used for levitation, through aethereal buoyancy, as well as propulsion. Aethereal propulsion differs slightly from levitation, the act of pushing against the aether generates potentially destructive feedback that must be compensated for; because it could potentially tear a ship apart. An idea I had was that the aethereal feedback compensators scale up poorly leading to a prevalence of small nimble craft.
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> The Aether field behaves like a fluid (which is air technically) so aether-engine craft maneuver as though they were in atmosphere, and must deal with shifts, currents, up- and down-drafts.
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All of the above works, at the very least it doesn't give me any more conceptual headaches; I am however always open to ideas.
However I ran into a problem, if there were other forms of propulsion available no one would use aether-engines, they have far too many complications. The solution that I devised was that people had no choice but to use aether-engines.
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> The aether-field clings to matter, unless you're using an aether-engine trying to move through it; it is like driving through quick sand, the more you fight the tighter it clings to you. While this works out just fine for slowing down it causes all manner of cosmological problems. So the solution to that was to have the gravity of high mass objects, planetoid-mass and up cause the aether-field to diffuse enough for stellar bodies to move at least somewhat normally.
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Before I have to cut the aether from my setting, I ask how to resolve the issues with the aether and it's effect on objects. The solution that I have only opens up more questions. That is that gravity displaces aether for planetoid mass objects and greater. However if that is true then shouldn't a star's mass displace most of the aether in a solar system?
I find my self asking similar question of any sci-fi setting where planetary gravity wells inhibit FTL travel but the Sun's doesn't?
[Answer]
I don't think that you have to modify the aether in any way past your first idea. People may prefer non-aether engines over aether engines for many applications, however they would need to invent those other engines first: and in most cases it would just be better to use an aether engine over inventing a whole new field of engineering. Lets have a look at the pros/cons in some situations:
*In space travel:* Your Aether engines are the only way to go. Seriously. They're effectively reactionless, you don't have to carry reaction mass for them and they can be used anywhere. To stress how important this is: Rocket launch pads require a huge clear zone around them, even modern rockets are prone to exploding, and they have to carry so much fuel to lift their own fuel that launching to space (to say nothing of manoeuvring in space) is exorbitantly expensive. I can't think of any reason aside from raw power that you'd want to go with rockets, and if the aether engines were developed before safe rocket technology (Don't be fooled into thinking rocket development was simple. 'It's not rocket science' is a phrase for a reason), I can't even think of a reason rockets would be invented.
*In high altitude travel:* Much the same as space travel. Scram/Ramjets require a high level of technological development, and the air is too thin to push off with jet engines at high altitudes, so again your Aether engines come out on top. No 'aether resistance' necessary.
*In low altitude travel:* Here you get to the point where propellers/jet engines become useful. Again: If aether engines came before jet engines (depending on the efficiencies) I can't see why research would go into inventing the hideously complex and dangerous jet engine when you could instead focus on better aether feedback damping.
Propellers could be useful for big ships but they would be far less efficient than the aether engines and have the downside of being external, and thus susceptible to enemy attacks/meteorological effects/unfixable mechanical problems etc. Not only that but they cause actual wind effects, which may be inconvenient for the people that are in the ships or on the ground. For large, planetgoing ships I can see propellers still being in use, but these vessels wouldn't be capable of high-altitude or space travel unless outfitted with aether drives, at which point you may as well just go full aether.
*On the ground or in the sea*: Of course they'll use other engines. Oceangoing liners with big-ol diesel engines and pistons larger than I am? Chugging, smoke belching factories? Reassuringly growly automobiles? These things are just awesome. A potential use for Aether engines in this scenario would be for all-terrain vehicles, if wheel grip can't be guaranteed to transfer engine power to the ground, but other than that I think that internal combustion engines are pretty safe, even if you introduce the aether drag. They would need more horsepower, but stopping internal combustion engines effectively would also require stopping other things, such as actual horses or fast punches.
TL:DR: In essence, at the tech level of a dieselpunk setting, if the Aether engine came before the jet engine I can't see a reason why people would invent other engines rather than focusing on making their aetherial tech better.
[Answer]
The simplest way is just to have rockets not work or be inefficient. Anything else already doesn't work in space as there is no air to push against.
So gunpowder for example is very diesel/steampunk ish and actually doesn't have great energy density. Some gunpowder rockets strapped to a ship may be able to give it a temporary burst of speed but you'd rapidly run out of gunpowder.
Restrict access to high explosives or advanced rocket fuels and you're fine.
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