system
Given the following post, respond as if you're commenting on Reddit:
human
Could we terraform the moon?
gpt
The biggest problem with trying to terraform the moon is that it's just too small to hold onto an atmosphere. Were we to somehow manufacture an Earth like atmosphere on the Moon, the majority of it would escape into space almost immediately (not enough gravity). What little remained would be too thin to breath, or even for a human to survive without a space suit (imagine being on the summit of Everest, but much worse). And what little trace of atmosphere was left would slowly be worn away by the constant solar radiation, which, over time would strip the remaining gasses away to practically nothing.

There is however one possible option that might make the Moon 'kinda' habitable, or at least slightly more survivable. 

If we were somehow able to manufacture a massive amount of the Nobel Gas Xenon (using perhaps some kind of breeder reactor) we might be able to produce an atmosphere on the Moon that was something close to half normal atmospheric pressure. Xenon is a very heavy gas, and solar radiation lacks the energy to strip Xenon from the Moons atmosphere at this distance from the Sun.

Of course, you could never produce any large bodies of liquid water. Any disassociated hydrogen atoms would float to the top of the atmosphere, and without a magnetic field to block the solar wind, they would be stripped from the atmosphere. All the water would disappear over the course of perhaps a million years. The remaining oxygen would react with the lunar soil...

.... So you'd end up with a large barren desert, with an un-breathable atmosphere. But at least it would be non toxic, and somewhat shielded from radiation by the Xenon atmosphere, so you'd be able to walk around outside wearing a T-shirt, jeans and a scuba tank.

The other advantage would be that if you had a dome filled with breathable atmosphere at say 0.5 bar, and an Xenon atmosphere outside, also at 0.5 bar, if you got a leak in your dome it would be no big deal, no sudden depressurization, you just stick a bit of tape on it and it's fixed.

It's hard to be sure how long it would take to produce a Xenon atmosphere, but assuming you were using large numbers of breeder reactors, perhaps using the Moons molten core as a fuel source, I'd guess you could do it in under 10,000 years.

EDIT: Note the problem of escaping hydrogen could be reduced if you could generate an artificial magnetic field. Using superconductors to create massive electromagnets might make lakes and seas possible. Of course, you'd have to mine the Kuiper Belt for comets, to get the water there in the first place. Then again, if you have a breeder reactor than can make Xenon, why not make Hydrogen and Oxygen while you're at it.

The other option would be to heat up the core of the Moon and somehow make the entire Moon start spinning. This would of course cause massive Moonquakes and require many times more energy that the entire human race has ever expended. The danger being that it could interfere with Earths magnetic field and possibly could result in the Earth becoming uninhabitable.

EDIT2: Correction, Xenon (atomic weight 131)  not Argon (atomic weight 40).