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xkcd #2908: Moon Armor Index (imgs.xkcd.com)

submitted 8 months ago by randomaccount43543 to c/xkcd

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https://xkcd.com/2908

Alt text:

Astronomers are a little unsure of the applicability of this index, but NASA's Planetary Protection Officer is all in favor.

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[–] topinambour_rex 10 points 8 months ago (1 children)

As Moon is slowly moving away, at some point in the future there will be no more full eclipse. And there is 2 full eclipse by year !

[–] [email protected] -5 points 8 months ago (2 children)

Nah, it's just a moving away, then moving closer again thing over millions of years. Balance between gravity and centrifugal force.

[–] teft 9 points 8 months ago

This is incorrect. The moon is moving away from the earth and will stop. At some point in the future the tidal forces will balance out and the earth-luna system will be tidally locked. From that point on they will remain locked in orbit neither moving away or towards one another unless some other large gravitational force perturbs them (e.g. an extra solar planet wandering through the solar system and passing by earth-luna).

[–] topinambour_rex 7 points 8 months ago

Ok I read somewhere it would reach it's farthest orbit (29d and half) and stays there then.