Ok, I've spent the last three days reading through this thread (not constantly, but between doing important things like eating, sleeping and pooping) and I have seen some amazing answers from our residents.
I have a few questions of my own.
I noticed someone asked if a planet could orbit a black hole, obviously far enough away to not fall into it, although I think I'm right that all orbits degrade over time, but I'm not sure if this was ever answered. If it is possible, and I don't see why not, would the planet get any kind of heat in the form of Hawking (or other) radiation?
I have seen mocked up pictures of large orbiting bodies as seen from a planet, and I wondered how large a body could look before it is too large. Io would have a very large Jupiter in the sky, but it would be too large as Io is so close that it is affected by the gravity to such an extent that it would be nigh on inhabitable. I understand that a planet could be big but not dense, so I'm guessing the answer will also depend on the mass of the planet, but how realistic are large Suns and planets when viewed from the surface of another planet?
We had a great discussion in a thread ages back about the terminal velocity of water, and for the purposes of a waterfall that starts in ice and ends in steam the best suggestion was ice that was travelling very fast from outside of a planet's atmosphere and heating up on re-entry until the friction with the atmosphere managed to turn it into steam. So how could this work, I have supposed two closely orbiting bodies and one somehow (gravity i guess) takes water from the other, I'm sure the other has to asssit in giving it away, so that it accelerates through space before hitting the atmos of the other planet and becoming the eternal waterfall. the other issue with this is how does the water then flow back to the first planet?
ok, that is all for now. But as I am working on the second draft of my first novel which happens to be a comedy space opera, it involves lots of strange places that will require some scientific justification, I maybe back to ask plenty more.
So for you brain boxes out there, be ready to have your brains boxed