Questions on a planet with no external heat source

[Booper]

I had an idea for a planet either with no sun, a sun thats too far away, or a dying/small sun that doesn't provide enough heat. The only things keeping this planet warm are its overactive core and/or a large population of fire elementals.

How would this planet look? How would life survive? I already figured that plants would be much like the ones found at the bottom of the ocean since theres no/hardly any light. Most animals wouldn't need eyes since they live in darkness (or perhaps there's another light source? magic glowing trees, mountains, rivers, or clouds??).

Any thoughts or suggestions?

[VoxRationis]

Well, there's not going to really be any plants, not as we know them. They'd have to be replaced by chemosynthetic organisms. And this means that rather than spreading over wide areas of the world, life is going to be spotty, made up of scattered oases around areas with volcanic vents and the like. Tales of screwing up the small, delicate ecosystems and producing locally catastrophic failures will be a common theme for any civilizations that appear. The distribution means that speciation will be easy. Large predators are unlikely; expect "tricky" ones instead, with poison/camouflage/restraining techniques. In aquatic areas, electric senses may well become common. (This world is really starting to sound perfect for horror, by the way.)

[Yora]

If you still have starlight, that's still good enough to use eyes. Human eyes are terrible at those conditions, but even we are not completely blind with no sun or moon. And plenty of Earth animals are much better at seeing at low light. If they evolved with such conditions, they probably would not have much trouble with sight at all.
However, it would mean that to such creature any fire is extremely bright. Being close to a campfire would be like looking into floodlights. (Though that can easily be compensated by putting a barrier around the fire that is open on the top, so you don't have to look at the flames directly to stir a pot that hangs above it.)

Plants would not be green, though. With no real sunlight, there probably wouldn't be any plants with leaves at all. They would produce energy by splitting up chemicals from their surroundings (like animals get energy from digesting plants and other animals). However, anything in the environment that occours in large number probably has undergone most possible chemical reactions that don't require energy, so there most likely would not be much energy to gain from them. (Like you can't really make a fire by burning ash. It already burned out long ago.)

[ace rooster]

If you still have starlight, that's still good enough to use eyes. Human eyes are terrible at those conditions, but even we are not completely blind with no sun or moon. And plenty of Earth animals are much better at seeing at low light. If they evolved with such conditions, they probably would not have much trouble with sight at all.


Unless you have seriously freakishly good night sight, you are pretty much completely blind. I didn't realise quite how blind until I was driving though proper wilderness and got out for a pee on a moonless night. The stars were fantastic, so I spent a good few minutes letting my eyes adjust, and just looked at them. I then got quite a fright, because I discovered that I could not see my car, even trying to let my eyes adjust to staring at the ground. I was 3 feet away from it, and I consider my night sight pretty good (would not use a torch if there is a quarter moon). :smalleek:

The light pollution from a major settlement is enough to function by for about 50-100 miles, but stars are not in my experience.

Anyway, as you said, any creature evolved to work in these conditions would not have a problem, so it is not important.


What life needs is an energy source. Chemical sources would certainly work, but I would also suggest electrical ones. If there was some strange resonance in the magnetic field then life could harvest the energy from that. If we are in fantasy land then we can just invoke magic, and it is fine.

[hiryuu]

Unless you have seriously freakishly good night sight, you are pretty much completely blind. I didn't realise quite how blind until I was driving though proper wilderness and got out for a pee on a moonless night. The stars were fantastic, so I spent a good few minutes letting my eyes adjust, and just looked at them. I then got quite a fright, because I discovered that I could not see my car, even trying to let my eyes adjust to staring at the ground. I was 3 feet away from it, and I consider my night sight pretty good (would not use a torch if there is a quarter moon). :smalleek:

The light pollution from a major settlement is enough to function by for about 50-100 miles, but stars are not in my experience.

Anyway, as you said, any creature evolved to work in these conditions would not have a problem, so it is not important.


What life needs is an energy source. Chemical sources would certainly work, but I would also suggest electrical ones. If there was some strange resonance in the magnetic field then life could harvest the energy from that. If we are in fantasy land then we can just invoke magic, and it is fine.

How weird. I can understand that in the woods or the swamp - those places turn pitch black because there's trees. Things just didn't slowly turn blue and visible after about twenty minutes for you?

Anyway, yeah. I'd expect to see lots of bioluminescence, and nothing we'd call "plants," except as a convenience term. Lots of stuff that crawls low to the ground. Things grow up to compete for more sunlight. In this case, things would grow out to compete for more chemical coverage. Maybe the whole surface is covered with a soft, fleshy padding in many places. Maybe there's not a lot growing on the surface at all, and mobile members of the ecosystem travel long distances only to dig things up.

I can imagine a massive creature that walks along looking for chemical vents and digs them bigger and wider, and how important it is for both ecological reasons and to the locals - and everyone bellyaches over whaling making it damn near impossible to farm, and whalers complain that if they don't kill them, nobody gets any meat or light or drilling equipment or bones for tools or stomachs to make bags and containers.

If you're going to invoke magic, then we have to start thinking about what kind of magic and how it's going to be used. Elemental gateways would result in a very different sort of place than, say, life forms that harvest arcane energy from passing phlogiston rivers.

[Bearon]

I'm imagining something of an expansive underdark, while the surface is barren and anathema to life. Geothermal heat seems likl a viable way to support life underground, especially with an overactive core. Perhaps lifeforms would have to live nomadic lives, trying to avoid lava flow or other underground dangers. Bioluminescence should definitely be a thing if there are no other natural light sources. If you're up for some sci-fi inserted into this fantasy world, maybe a previous civilization's ruins scatter the surface, skeletons telling the story of a world before an expired sun. Perhaps some find profit in looting these ruins for the technology (or magic) of the ancients.

[sktarq]

Few questions?

Firstly- what do you plan on doing about the fact that your world would be about 3-4 degrees kelvin unless something else gets involved. -Radioactivity perhaps.
This will basically freeze solid almost any solvent for biochemical reactions. Liquid helium for blood, perhaps?

Also what energy source feeds the base of the food chain? For us it is sunlight powering chemical reaction in phytoplankton and plants. But we have found chemical seep based ones here on earth too-now that could be useful to you.

Go modern godzilla and have some bacteria / plants absorb "radiation"?



Have the planet be near the galactic central cluster so some forms of radiation that humans don't think of as "light" may be available in densities high enough to support life?

Also what kind of planet? Rocky? Frozen Gas giant? Size?

These questions say what is available to eat and thus says what things may do the eating.

And for starlight-having seen my own shadow cast by the milky way-moonless nights can be plenty visual.

[Gogolski]

The only things keeping this planet warm are its overactive core and/or a large population of fire elementals.
This planet is probably quiet huge!
A migrating brown dwarf is about the only thing short of a star that has enough core activity to provide a temperature that would not freeze water on it's "surface" without an external heat source.
This brown dwarf like thing will most probably be an enormous gas giant, so speaking of a surface is a shady business. These planetary bodies tend to go from gas in the outer reaches over liquidy-gas deeper inside to solid-gas in te center in an +/- continuous way.

You might want to read "The Algebraist" by Iain M. Banks for a fictional impression of what it could be like inside a gas giant. (And I advise everybody to read it because it's a fantastic book!!!)

My advise:
Don't keep it real!

Let your core go wild with radiation to heat some part of the planet. Cover your planet with a layer of water and a thick mantle of ice to insulate it and keep the warmth inside or something. Let the inhabitants live in a happy symbiosis with radiation soaking bacteria as sktarq said in previous post.

Most of all, have fun designing your planet!

[NRSASD]

As several people have mentioned before, all life needs a source of energy besides heat. You could have an extremely thick atmosphere that contains lots of nutrients belched up by volcanic activity constantly, though this would make the surface nigh-uninhabitable due to hellish incessant sandstorms that are necessary for life. Creatures here would resemble mollusks I suspect, putting out tendrils to gather food during periods of "light" weather but hiding within shells/crevices when the storms get too severe.

Another thing would be naturally occurring nuclear reactions in subsurface levels. This actually happened on Earth 1.7 billion years ago in Gabon due to the extremely high-deposits of uranium. However, this implies that your world is rather young geologically speaking, since radioactivity decays beyond necessary levels after a period of time.
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

Finally, you could have a planet that looks like Mustafar from Star Wars, being a gigantic ball of mostly molten rock. It'd definitely need some serious radioactive or magical reactions to keep it from freezing solid though.

Hope this helps!