posted
A long time ago, I started a thread about what would happen if the sun were to be destroyed, or disappear, etc. This time, it's a different question altogether.
For a science fiction story that is currently residing in my mind (nothing on paper yet) I am trying to come up with a functional world that never had a sun. Is this possible? I don't think it is, but are there any possible ways for it to work? What kind of heat source would it have? I was hoping for this world to be some sort of arctic world. Any ideas?
[This message has been edited by scm288 (edited February 15, 2006).]
posted
Well, a planet-sized body can form around a brown dwarf. (Generally, plants are considered to orbit stars, which means there's a question as to whether something orbiting a brown dwarf is a planet or a satellite.)
A brown dwarf is not a star, because it doesn't have enough mass to fuse hydrogen-1. (Some brown dwarfs do fuse deuterium.)
As chemo_man suggests, there would be geothermal energy -- particularly if the planet orbited close enough to the brown dwarf that tidal stresses kept it geologically active (like Io around Jupiter.)
posted
I've always thought the concept of a planet with no sun would be fascinating as well. This week I read a story in the March 2006 Asimov's that uses the no-sun concept: Dark Eden by Chris Beckett. Really cool world. Worth checking out.
Posts: 818 | Registered: Aug 2004
| IP: Logged |
posted
How about severe thunder-electric storms? Not 10,000 volts but upwards and over say 1 million volts, possibly even say 10 million. A billion, possibly? It could work for an artic planet, would it?
Posts: 384 | Registered: Oct 2005
| IP: Logged |
posted
I'm OK with a world warmed by tidal friction; some thing Europa may be that, deep down. Life should be a slow process and slow to develop; speed takes energy. Where would your life get its? Sulfur ejected from geothermal vents could support some, but Earth's vast variety evolved over huge areas -- a few vents probably wouldn't be enough to get you the evolution for interesting animals. Maybe some other source of energy can be found.
(And it can. Camelot 30K: nuclear-energy life.)
I don't like the "arctic world" idea, at least if it's to be habitable. If the entire Earth were covered with ice, there'd be no trees and no plankton beds, and therefore no free oxygen. There's also the fact that there's variety, or can be. Earth is a room-temperature world, on average, but it has the Dead Sea, Antarctica, the Amazon, and Ireland. (I'm reacting against Star Wars's "ice planet" and "jungle planet" idea. But it *can* work; the moon is pretty homogeneous.)
posted
Any world with a sizable moon in close orbit will produce geothermal energy. If the moon were four times its size, the Earth would be so volcanically active that heat would not be a problem.
All life would be heat based rather than the light based ecosystem on earth. (Plants convert air(CO2) Water (H20) and sunlight to sugars (like C6H12O6) which the rest of the food chain uses for food.) Something on your planet would have to convert air (CO) water and heat to sugars.
Once you have those basic building blocks, the rest comes easy.
posted
If you had two bodies of equal mass orbiting eachother, you would lose the tidal friction because both would become tidally locked with eachother. In a double planet, They would actually both orbit around a point in space equidistant between them. Posts: 370 | Registered: Feb 2006
| IP: Logged |
This is scifi, people. Anything is possible. The trick is making it believable, and that's really not as hard as many people think. 90% of believability is consistency. If your story makes since internally--as long as it doesn't contradict itself--contradicting the rest of the known universe isn't much of a problem.
You could, for example, say that the planet's core was made out of some super freaky highly radioactive elements whose decay provided enough heat to keep the place warm. Of course, there'd be no light, but if you could invent some sort of radiosynthesis to replace photosynthesis (just like chemosynthesis does in those deep sea vent communities) you'd be fine.
I guess it really depends on what you want to happen on that planet and who you want to live there.
posted
The concept of a figure-eight orbit seems too implausible for me as any such orbit would be far too unstable to last very long. As for the question of two same-mass planets acting tidally on each other, what would likely happen if they were like that for a long time, is that they would become tidally locked to each other.
Tidal forces tend to slow down the rotation of the smaller body until its period of rotation = its day. For example, our moon always faces the same side towards the earth for this very reason. The tidal force of the earth on the moon has caused enough frictional slowing in the past so that the same side always faces us (meaning it rotates once per period).
A similar thing has happened with Mercury facing the sun, but the most insteresting thing is Pluto and its one moon, Charon. Since Charon is very close to the same mass as Plute (something like a factor of 2 or 3 times lighter) both objects are tidally locked to each other. In other words, hypothetically, one could build an elevator that went from a point on Pluto to the corresponding point on Charon and it should stay intact, because both bodies are tidally locked, facing the same side towards each other at all times.
This is likely what might happen with two similarly sized bodies orbiting each other. This in itself would be a very interesting idea for a story about two planet-sized objects rotating around each other, tidally locked in this fashion.
posted
If you can find a copy of the old book published by Writers Digest called World Building, it is a fantastic book for building believable worlds of almost any kind. It is written by a PhD geophysicist. I know quite a bit about astronomy and the hard sciences in general, but having read this book, I would never write a hard SF story without it. It is an extremely valuable piece of literature.
Posts: 2 | Registered: Aug 2010
| IP: Logged |
posted
Darn. There's a brilliant website out there about creating planets for a SF and I can't find it.
wbriggs, when you bring up oxygen you're already locking into the idea of supporting human life. There are lots of forms of life on Earth for which oxygen is a poison.
posted
Well, not necessarily human. But we can't expect animals to breathe methane or CO2; there's no energy in it for them. Or nitrogen. Hydrogen would work.
posted
Oxygen is a by-product of life on Earth. The important thing is that you need to trap most of the natural CO2 and CO (CO is stable at high temperatures)that comes with planet creation, otherwise you end up with a run-away greenhouse effect and you have another Venus. On earth, it's tied up in limestone. After that, there is a cold zone in the atmosphere that helps keep the oxygen on the planet rather than escaping into space after UV photo-dissociation of water vapor into the component atoms.
A planet is a very complicated system that has many seemingly unrelated processes that are in reality all interconnected. Probably humans wouldn't exist on Earth without plate tectonics. That might surprise you, but in part, it has to do with making potassium available at the surface. Potassium is necessary for earth plant life.
[This message has been edited by Spaceman (edited February 18, 2006).]
posted
For every parameter there is a goldilocks zone where conditions are just right for life. So it's all a matter of statistics of exactly how often this occurs... Just because life can survive somewhere, doesn't mean it will spring up there. Or if it does, the more limited the enviroment, the slower the evolution of complex life. The first evolutionary steps are the longest. I think it would be more believalbe if a world with a limited biosphere were seeded from the outside.
Posts: 50 | Registered: Feb 2006
| IP: Logged |
posted
Panthos, are you sure about tidal locking? Would it not be a function of distance? The moon is tidally locked to the Earth, but the Earth is not locked to the sun. Anyway, what's the differance whether two bodies are of equal in size or not?
The attaction between two bodies is a vector. The magnitude of the attaction is either strong enough to lock a body to another or it isn't. Of course, if the bodies are equal then one locking means the other will too. But they can also be just far enough apart that one locks and the other doesn't because they're not perfectly equal. Or they can be far enough so that neither locks.
You would just need to have both far enough away from other bodies to keep them from being disrupted. But then that would obviate it as a cool setting for a story.
How about this, could not the alignment of other tidal forces in a system cause one or both of an orbital pair to occaisionally break lock? Wouldn't that be an interesting event to set a story around?
[This message has been edited by Ted Galacci (edited February 20, 2006).]
[This message has been edited by Ted Galacci (edited February 20, 2006).]
posted
Distance is definitely a factor. So is original rotational speed. Even with two objects the same size and mass, if one originally rotates faster, it will take longer than the other to become tidally locked.
The biggest problem I see with the elevator is that the two planets will probably not be in exactly circular orbits about their center of gravity, so your elevator would have to be somewhat elastic.
Probably the best scenario for tidal heating is to have a number of bodies, such as the Jupiter system. Io is tidally locked, but the passage of Europa and Ganymede cause it to twist somewhat, resulting in tides of 50 meters or so (and that's not water; it's the stuff of the moon itself!). Plenty of energy is available there; probably too much. The same effect works on Europa, though to a lesser extent.
posted
If it's a simple two body system with low eccentricity orbits, and both bodies have solid surfaces (this is very important), then it isn't a question of whether they lock but when.
Posts: 8322 | Registered: Aug 1999
| IP: Logged |
posted
Survivor is right. The earth and moon will eventually lock. The sun may never lock the earth because of the moon, but the moon is certainly slowing the earth. Estimations are that the original day was something like ten hours.
Posts: 2 | Registered: Aug 2010
| IP: Logged |
posted
Timescales are also important to keep in mind. Even as we speak the rotation of the earth is slowing down, tidally locking with the moon. I remember in one undergrad astro class I took a couple years back, after plunging through the physics involved, I asked the professor what would happen if we became locked with the moon, how that would affect life on earth.
He told me not to worry. The sun would run out of fuel far before the earth became tidally locked with the moon. So yes there are lots of factors to tidal locking. Distance, original rotation speed, relative mass, other interferring bodies (like the moon on the earth keeping the earth from locking to the sun, or the other moons of Jupiter messing around with IO, as previously mentioned). The whole mutual-locking idea like Pluto and Charon I mentioned was an example of similar mass, relatively close distance, and (presumably) somewhat similar initial rotation speeds. Since you're making a story on the planet/moon of your choice, you can essentially choose whatever initial conditions you want, so it boils down to, do you want things to be tidally locked already or not?
posted
I'm going to throw another story on this theme into the collective hopper. Fritz Leiber's "A Pail of Air." Also, it's a terrific read in its own right.
Posts: 8809 | Registered: Aug 2005
| IP: Logged |
posted
Remember that tidal locking doesn't have to be 1:1. There are other resonant ratios, like Mercury's 3:2 tidal locking.
Posts: 2 | Registered: Aug 2010
| IP: Logged |
posted
Concider if there was a couple blue giants nearby. I read somewhere that the earth's warm region for a blue giant would be around the orbit of pluto, but the radioactive particles would make it dangerous for life. The radiation from them could give the energy requirements for the planet's heat. That and a high level of radioactive materials (aluminum, unranium, plutonium, argon, and so on) within the crust of the planet.
Another thought, If one is in the right region close to the core of the galaxy, the core itself might provide a sun's requirement of energy, both light, heat and radiation. Of course, one would have to work out how the planet, which we assume is traveling without a sun, is able to not be picked up by gravity perturbtions of passing stars.
posted
Well, the issue with being close to the galactic center is the level of gamma radiation. You'd get lots of light and heat, but you'd bake anything with even the remotest chance of life.
The other issue is that planets form in a solar nebula, which always produces either a star or a brown dwarf. I suppose something could happen to a brown dwarf to cause the planet to be removed from its neck of the woods... a nova, maybe? Or would that just incinerate any nearby planet-like formations?
I have another question to ask: could humans survive in a dark world as outlined above? We need sunlight to modify seratonin levels, as well as to produce vitamin D--could a society with a high enough level of technology circumvent those issues and live on a planet that is only habitable due to geo-thermal energy?
posted
If you had two stellar systems pass through each other, there would be a significant chance of at least some of the planets being ejected. There is also the issue of gas giants, they can throw terrestrial type planets right out of the system when things are still forming.
As for humans living there, if you have power, you can have light. It's true that artificial light technology only recently reached the level where it could supply what humans get from daylight, but it's not rocket science (which, you know, you'd need to get to this planet of darkness).
By the way, Mercury isn't tidally "locked" so much as it's reached an equilibrium between the acceleration of its rotation during perigee and the decceleration during apogee.
Printer-friendly view of this topic
Even if I DON'T understand it all.
