Imagine that the earth is hit by another Mars-ish sized object causing a second moon to be formed. If the second moon were orbiting the Earth inside or outside of the orbit of The Moon, and assuming it was not orbiting the Earth parallel to The Moon, the two moons would have to cross each other at some point, right? A sort of moon-over-moon eclipse thing. How would you calculate how often this would occur? What would it look like? Does this happen on planets with more than one natural satellite? Does the premise of this question make no sense because my knowledge of astrophysics is basically nil? Explain to me like I am in fifth grade, please. [more inside]
posted by Lutoslawski on May 30, 2012 - 7 answers

How far up do you have to go to see the Blue Marble? [more inside]
posted by alms on Apr 9, 2012 - 10 answers

Could mining the moon destroy the oceans? [more inside]
posted by asnider on Feb 27, 2012 - 12 answers

I'm looking for usable 3d meshes of Earth, Moon and Mars I know the data is out there for free, but the data I've found is ridiculous (4 terabyte high resolution files), hard to use (5 degree slices that would need to be assembled), in formats that only planetary geologists can use, or simply stuck in the labyrinth of poorly maintained and documented government web sites where I can't find it. [more inside]
posted by Ookseer on May 8, 2011 - 8 answers

What was the size of the earth, proportionally to it today, before whatever hit it to create the moon?
posted by Sparx on Jan 13, 2011 - 12 answers

Is there anywhere on Earth, where you can't see the Moon? [more inside]
posted by Dub on May 24, 2009 - 16 answers

After a long and ridiculously heated quasi-scientific discussion last night, I absolutely must know: what would happen to life on earth if the moon suddenly disappeared? I say the results would be disastrous, but my friend doesn't think it would matter much. I'd be interested to know who is more accurate in her assessment and the specific problems associated with a moonless earth.
posted by TheGoldenOne on May 24, 2005 - 43 answers

Something I've never understood. It takes a giant rocket to achieve escape velocity and leave the Earth. The Apollo mission made it all the way to the moon. But in all the pictures I've ever seen, the only thing they've got on the moon is a lander, a small capsule on legs. Where's the rocket they used to get off the moon? How did they get off the moon? I know the moon is much smaller and has almost no atmosphere, but is leaving it really as easy as firing a few booster rockets? Why is the rocket to leave the Earth so much bigger?
posted by scarabic on May 18, 2004 - 29 answers