Yeah, you’d have to have either a magic technology to change ordinary matter into antimatter by some low-energy process (and if you have that, you might as well just go all the way and make it a magic total conversion ray instead, like in Larry Niven’s “The Soft Weapon” and the Man-Kzin Wars), or a source to harvest the antimatter from, which of course has its own problems. Or have a big processing plant on a planet or something that produces antimatter “batteries” for starships, but that seems like a bad idea.
Thanks for the specifics. I never knew that a proton’s decay would be hugely accelerated in the presence of a magnetic monopole. That would make for a very interesting fuel source. Neutrinos might be a problem … I’ll have to think about that.
Hmm. I also need to find my calculator and see if I can figure out the potential difference in effective gravity on the far side of the moon vs. the planet-facing side due to centrifugal force as the moon revolves around the planet.
It seems to me that your main problem here will be that a spherical blanket isn’t going to be anything like orbitally stable. In order to be an effective insulator, your blanket’s going to have to cover essentially all the planet’s surface, but every individual fragment of mirror will need to be independently orbiting your moon. To cover the entire surface you’ll need particles in many different orbits, from equatorial to polar, with an average density high enough to be visually opaque. That’s going to result in a huge collision rate between mirror fragments, to the point where each fragment might survive only a few orbits before hitting another fragment. I don’t think the global mirror shell would last at all long - I doubt you could boost material into orbit fast enough to keep up with the attrition rate.
I think I’m going to agree with the others who say that the only way to make this work is going to be to allow the surface to freeze solid and have everyone living in insulated underground cities.
That was something I was wondering about. Could you create a bunch of different bands, each at a different altitude, so they cover the planet overall but don’t intersect?
Another question, this one (I suspect) stupider than most: on a body like Europa, where the gravity is, say, 10% of Earth’s, would the pressure under a certain amount of air or water be 10% of what it is on Earth? Like, if you were 10 meters under water, would the pressure go up by 0.1 atmospheres instead of 1 like it does on Earth? Or is there some other factor I’m forgetting?
It seems possible; I recall a similar suggestion for terraforming the Moon, although there the problem is the terraformed atmosphere dissipating over a hundred thousand to a million years, not heat loss. The idea was to set up orbital shrouds to bounce back air molecules, not mirrors to reflect lost heat, but the principle is similar. It’s not like you need 100% coverage, after all.
Also, another idea for keeping the moon warm, yet dark; have replicating/self repairing machines left behind by the original terraformers floating in the gas giant’s atmosphere. Have millions of them designed to use fusion power from the gas giant’s hydrogen to fire infrared or microwave beams at the moon, heating it without lighting it.
Another possibility that just occured to me; replace the gas giant ( or have it orbit one ) with an ancient black dwarf ( you might have to set this long, long in the future to be possible ), that has cooled enough to be dark, but still hot enough to warm, or help warm, an object like a captured planet or moon, if it’s close enough. I don’t know enough astrophysics to say if that’s actually possible, however.
Is there any real possibility of a twin-planet system that’s not in tidal lock?
You can always toss out the original ejection as the reason they’re not tidally locked, but it gives you a source of geothermal energy without requiring too much in the neighborhood.
How long you’d need would depend on what kind of black dwarf you’re referring to. On the one hand, that term can be used for the eventual end state of a red dwarf, but that’s trillions of years or so into the future, easily long enough that you have no business talking about humans. On the other hand, it can also refer to a cooled white dwarf, which there might be a few of in the Universe right now. Basically, it hinges on the question of how dark is dark. Anything warmer than absolute zero will give off some light, and anything warmer than 2.7 K will be in principle visible, to a good enough telescope looking in the right direction. But you could probably get something which would be good enough for your colonists. The parent body will probably fill a considerable fraction of darkworld’s sky, so darkworld’s equilibrium temperature will be a considerable fraction of the parent body’s, and a dwarf-sized object at a few times a comfortable planetary temperature will be unnoticeable at stellar distances.
If the primary object is your main heat source, though, you’ll absolutely need to not be tidally locked. If one side is perpetually towards the heat source, then that side will get too hot, while the other side gets too cold. Your atmosphere will blow over onto the cold side, where it’ll condense or freeze out and never return to the hot side, so even if the temperature is right at some point on the planet, you won’t have any air.
That’s what I was talking about. I think the OP is thinking more in terms of dark to the naked eye, not dark to instruments.
Not necessarily, if we are talking about a terraformed planet/moon; orbiting mirrors or some such could help even out the temperature. The idea behind the dwarf is to avoid needing a huge artificial energy source to keep the planet warm.
Also; if the habitable body is orbiting a gas giant, perhaps even tidally locked to that, couldn’t that prevent only one side being presented to the star ? I’ve often wondered about that since our astronomers started finding gas giants close to other stars. I’ve always heard that red dwarfs couldn’t support life because a planet close enough to be warm would be tide locked, but that idea came out when it was assumed that gas giants were always far from the star, like in our system.
This is fascinating. Thanks for the further posts, people. A brown dwarf is an interesting idea, but how long would a brown dwarf radiate enough heat to keep the planet warm? If the planet is heated significantly by tidal flexion, and (however it happens) retains enough of that heat to remain habitable, then it’s basically getting its heat by stealing energy from the rotation of the planet it orbits, right? Would a brown dwarf last longer as a heat source than the rotation of a Jupiter-sized planet? (And these characters, paranoid as they are, would prefer something that would keep the planet warm for millions or billions of years.)
Yeah, obviously you could find it with instruments, but they’re hoping it will be too small and dark for anything but giant arrays of probes that happen to be looking at it.
Regarding the parent body filling a good portion of the sky – the only dry land on the Darkworld (I like that. Thanks!) is going to be on the side facing away from the planet, for what it’s worth. I was going to have them awed at the big black hole in the stars that occurs when they go to the other side of Darkworld, but now I may abandon that plotline if there’s a big blanket of chaff around the world … but wait, I forgot, they do have satellite telescopes up to watch the sky for starship drives (you know, paranoid and all) so I could still have them do that.
If you want the moon to be tidally locked to its primary already, but still get heated, I think that you’ll need to throw in a few more moons to regulate its orbit and contribute to the heating. Io would not be as hot as it is without Europa and Ganymede in resonance with it.
Earth’s Moon is tidally locked to Earth- ignoring a small wobble here- and it doesn’t get heated by tidally-induced flexion any more. It does cause some flexing and heating of Earth, and in the process gets boosted into a larger orbit. Earth gets heated more than the Moon does in the process.
A brown dwarf and a black dwarf are two completely different types of objects. A brown dwarf never had enough mass to initiate hydrogen fusion, while a black dwarf does have enough mass and has already fused and burned out. For these purposes, I think a black dwarf is much more useful, since it can have any temperature you like, from white-hot to absolute zero. A brown dwarf can’t get nearly as hot.