I've forgotten most of my Earth Science knowledge, but to keep a "realistic" feel on the science-fiction project I have I need to create a realistic planet. My imagination of the planet is a frigid and barren land, yet inhabited by creatures that can survive its temperatures. The problem is humans, who will come into contact with the alien species. Giving room for technological advancement, what do you think the coldest temperatures are that a human (with proper space gear on) could survive on another planet? And how far from a sun-sized star would this planet be? Another question: Is it possible (realistically) for a planet to be in permanent darkness, or at least semi-permanent (3/4 of the day)?
Logically, with "proper space gear" on, there is virtually no limit to the temperatures they can withstand. This is science fiction after all so you don't necessarily have to restrict yourself to what is currently possible. As a general comparison, I'd say the distance of Pluto. Even if that isn't the distance you plan on making it, for the readers sake, make a reference to our own solar system so they have a familiar marker to reference it to. For it to be so dark as you imply, it may need to be a little farther. You will have to do some research on how far out a sun-sized star's gravity will keep a hold of a planet sized mass without it breaking free. I've never really thought about it, but I suppose a planet could be in permanent near darkness. The planet will obviously orbit a star otherwise it wouldn't be a planet. Therefore it will invariably receive at least some light from the star. The planet may be far out enough that it doesn't receive much light, but there will be some. It also largely depends on the atmosphere of the planet. It could have such an atmosphere that filters away a lot of the light that actually does reach the planet.
Do you think it would be possible for a moon (or several) to be in a constant eclipse, so that no light it brought in? I know eclipses (solar or lunar, I forget which one) are very rare, although the possibility seems to be there. It looks like I've got several days of research ahead of me.
Rarely were words more true . . . just suggesting that perhaps a planet could be in darkness for 3/4ths of the day made my inner astronomer wince. You don't want a planet; you're looking for an area on the planet that your characters can live in. There's a huge difference. You can't easily get 3/4ths-of-the-time darkness, but you can figure out ways for particular sections of a planet to get more or less sun. For example: tidally lock a planet. This means that it keeps the same half of it turned constantly toward the sun. The Earth's moon is tidally locked, which is why we only see one side of it no matter when we look up. If your characters are on a tidally locked planet, they will be in constant darkness or (if they live on the "edges" of the shadow) in constant twilight. Alternately, give the planet large volcanoes. Dust in the upper atmosphere can make the ground-level light quite gray and dim, and extreme latitudes might be cold anyway, so you could perhaps have an alien species living in dim light that way. How far away from a star? Depends on what you want, honestly. This bit you'll have to research yourself; I've got no idea what you really want, as you say you want a planet but your intent is closer to wanting an environment. Humans in space suits can already survive cold temperatures, as long as heat isn't being transferred away too quickly. (Easier to survive cold in vacuum or thin atmosphere than when you're sitting on a rock, for example.) But they'd need a base that was heated close to "human-normal" temperatures, to sleep in and live in when they weren't exploring or doing diplomatic work.
Make it a moon orbiting a huge planet. The moon would be shaded by the planet almost 1/2 of the time. But since the sun only shines on one half of the moon at a time (the other half is turned away), any given area on the moon would be in darkness almost 3/4 of the time. With this scheme, the periods of light and darkness would probably be irregular, though.
It is likely possible. With several orbiting moons or planets (around the star), it could be possible to permanently, or nearly permanently, shroud a planet in darkness. Keep in mind though, a planet that is nearly always in darkness will be very, very cold.
I'd like ot thank eveyrone for the information; it's been a big help in begining my research. Because the planet is supposed to be very cold, the distance from the star would prevent tidal locking, wouldn't it? The only examples I've seen are moons with planets, and the distance is extremely small when compared to the probable distance the planet will be to achieve such a cold temperature. Unless..... Unless this. Would large amounts of dust in the atmosphere signifigantly lower the average temperature, to possibly three or four times colder than the Artic regions of the Earth.
Large amounts of dust will drop the temperature to very cold, yes. Arctic levels? I don't know; depends on the thickness of the atmosphere, the distance of the planet from the sun, and how much heat you're getting from the magma inside the planet. No offense aimed at R-e-n-n-a-t, but space is frickin' huge, and you can't shade a planet by surrounding it with moons! Seriously, Saturn and Jupiter have a lot of moons, and Pluto has a huge moon; in both cases, the planet is still lit up brightly with sunlight. As for Islander's suggestion of setting your world on a moon, that's also incorrect; the Moon is not shaded by the Earth very darn much, and even if the Earth were much larger than it is, the area of the Earth's shadow would still only shade the moon for some small fraction of its orbit. The only way a tidally locked moon would work is if the moon were in a circular orbit perpendicular to the plane of the ecliptic, so that (for example) the southern hemisphere of the moon never got exposed to sunlight. Yes, distance makes same-face-always-toward-sun tidal locking harder. But you're trying to order a damn near impossible situation in the first place. The real solution is to have there be no sun at all, but I imagine you don't want that, so we're giving you the best alternatives we can. As for "three or four times colder than the Arctic," at some point I'm going to give up on your request as "Request Denied: Error exists between chair and keyboard." The Arctic gets to sub-zero temperatures as it is. What, do you want something that radiates at 50 K? Your humans can survive there for a while, but they'll need a base that's warmer -- at liveable temperatures -- and they'll have issues with fuel for heating. Unless there's a really really good reason for humans to be there, you'll have to pull the writer version of cartwheels in order to justify why the humans would bother with this place at all. Why not just set up a base on another planet, drop radios on the dark moon, and contact them that way? It's a lot safer than going someplace where just walking around can kill you in a few hours. By the way: the colder your setting's temperature, the harder it is to keep the humans' base warm, and the more ridiculous your characters seem for even trying.
Snowball Earth A supervolcano erupts and triggers a planetary cooling. Ice sheets expand far enough outside polar regions to create a feedback loop and a tropical distribution of land facilitates Earth looking like a snowball. Pretend your planet already had a thriving cold-climate ecology which flourished globally on an ice covered planet. Earth's equator was roughly as cold as modern day Antartica, and humans can survive there without a vast amount of complication. As for permanent darkness... who says life has to exist outside of the snowball? Why not inside? The day/night cycle won't mean anything at that point.
It doesn't have to be an eclipse to have little (no by our standards) light. Your planet could be in semi darkness for all of the day. At Pluto's distance, the Sun is just a rather bright star. True. Your particles would be big, probably large carbon molecules. It could even be blocking out the majority of the star's light. Life as we know it needs energy to survive, but that doesn't have to come from the Sun. Take Jupiter's moons, for example. Jupiter radiates its own heat, and on top of that, the gravitational pull it (and its largest moons) has causes Io to have tides of solid materiel. That friction causes heat, of course, the same reason (probably) why there might be a liquid ocean underneath Europa's icy crust. Keep in mind for this that there is no way for us to know now what other life may be like. We're only guessing at what it needs to survive and we've got no idea as to what it would look like. Basically, you've got an enormous amount of freedom here while still remaining in the vaguely believable. The sky's the limit, if you'll pardon the pun. As for space suits, they're designed to withstand the vacuum of space, which feels just about as cold as you can possibly get (it might not actually be cold, depending on where you are, but that's a physics tidbit for another day). I wouldn't worry about the temperature for your astronauts (particularly if it's in a more advanced time than our own). What I'd worry about is air. If the suit busts, then you worry about temperature, pressure and if the atmosphere contains anything corrosive or toxic (probably, as almost everything is toxic to us :3 ) Hope that helps!
This is awesome. I like you. Seriously, this is a completely realistic(imo) and original idea, and I think it could potentially be done right. I think it's realistic because I can see an audience of people believing it, or a reader buying in. I could buy into it, largely because of the equater thing. Everyone knows the Earth is warmer at the equator, which makes the setting believable through transitive logic. Are you thinking new species of life are born on Earth anew? So awesome, so freaking sweet! Evolution. Life and death. Survival of the fittest. Perhaps humans are no longer the dominant species? Perhaps they remain dominant. I just thought of another piece of "logic" to make this world more believable to an audience. T new species, singular or plural, should exist out in the edges as the world, in the most extreme cold. It'd be interesting if a creature that's habitat was in the extreme, in the poles of the Earth, evolved which enabled it to cross over into neighboring land of the equator. With that in mind, a neighboring frigid wasteland, what if we approach the society kind of the wild west? Ruthless mercenaries, and tough heros of few words? Maybe there's mining oppurtunites for other worlds? Who knows...I really like the potential options with this world though. I also like the feel and tone; make it dark and gritty. Another piece that would be interesting was if the equator was lower down, and the rest of the planet was covered in extremely deep snow, think like frozen sand dunes, that they had to get on top of to explore. Or perhaps they have to go through it. Keep in mind, the whole new species idea is just that, an idea. If you disagree, vocalize. With this setting, the question becomes, who are the characters and what is the society like?
