I'm tired of being told "there are many possible mechanisms; look it up." I want, and this is to be considered a direct question according to board rules, a brief but detailed summary of the few you consider most reasonable and why. Further, I want you to tell me why these ideas are preferable to you over relatively fixed sizes of planets/moons.

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Gillian

"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

"You can't erase icing."

"I can't believe it doesn't work! I found it on the internet, man!"