The moon as a covert space station

I do like the idea a lot of the Moon being a space station, but for me the story would have to be set in the far-future because the creation of the Moon isn't in any way an unexplained mystery. I'm guessing (and I hope you don't mind me doing so) that the basic mental image you might have of how the Earth formed was that there was a central mass that gradually got bigger as chunks of material were gravitationally drawn to it, until you were left with the Earth-sized object.

There are gaps in Solar System formation theory, but the overall scenario is well-accepted and is different from the above. I don't think this is the place to go into details (unless you wish it), but as a general overview, a cloud of gas and dust began to gravitationally contract. It had a bit of rotational motion, and as it contracted, it span faster, as a spinning ice dancer would when they pull in their arms. The cloud flattens into a disc with a young Sun at its centre.

Dust particles in the disc collide and stick together, becoming larger (in a process called accretion), until they are a few kilometres across and are known as planetesimals. They collide with each other, and the growth of larger ones in a region would start to outpace the others, sweeping them up. Eventually you go from lots of planetesimals to a few hundred objects that are a few thousand kilometres across, called planetary embryos. The main point here is that there is no one object at the start that is 'destined' to become the Earth, or any other planet.

Chance collisions between planetary embryos would have been devastating, melting both bodies and causing them to combine. The embryos would grow through these giant impacts. The Earth would have taken 100 million years to be the final result of a series of these collisions.

The Moon likely resulted from the last giant impact to affect the 'Earth'. A smaller embryo hit a larger one: some of the material of the two bodies combined, and some ended up in orbit around it. This was a bit unusual, but not unlikely. The orbiting material eventually accreted to form the Moon, and the larger body cooled to form the Earth.

This is all supported by things like evidence from density measurements of the Earth and Moon and the other terrestrial planets; studies of meteorites, including some dating from the planetesimal stage and of what we understand about how the planets evolved internally after their growth essentially stopped. The mid-Atlantic ridge is not a signature of an impact, but a result of tectonic activity, where the plates that make up the Earth's crust are diverging and material from the magma below is welling up and adding to the crust. This is balanced by places like all down the west coast of South America, where one plate is forced below another and crust is being destroyed. Tectonic activity is a one of the results of heat trying to escape the Earth's interior after it formed; it is separate to the planetary formation process.

Sorry about the ramble; my point is that personally, although the Moon as a space station has lots of possibilities, I wouldn't be able to suspend disbelief if these basics weren't taken into account in the story. I can't think of examples where it was done.

Dammit Sophia, evidence-backed scientific theory and observable phenomenon have no place in a total flight of fancy thread like this!

-Derek