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by gus_leonel 293 days ago
> I'll never see an earth-rise

You wouldn't see one even if you were on the Moon, which doesn't rotate with respect to the Earth. (In the spirit of your comment, you can satisfy yourself about this intuitively by reflecting that we always see the same face of the Moon, so somebody on that face wouldn't see the Earth changing position in the sky, either.)

2 comments

You'd probably get into lunar orbit before descending to the surface, so that would offer you an opportunity to see the Earth rise (sort of).
You are not wrong, and I am not trying to be pedantic. But I want to take this opportunity to bring up an interesting phenomenon.

While the Moon is tidally locked with Earth, a slight wobble in the Moon's motion (an effect called lunar libration) allows us to see more than 50% of its surface over time.

Therefore for an observer positioned on the Moon's limb (the boundary between the near and far sides), this wobble would cause the Earth to slowly rise just above the horizon and then dip back down. This movement would be extremely slow, taking place over many days, and would only involve a portion of the Earth's surface, not the entire planet rising completely into the sky. But it is the closest thing to earth-rise and set, you can get from the surface of the moon.

The wobble is caused by the moon speeding towards earth (on approach in its elliptical orbit) and then slowing down (on receding away) while still having a constant spin on it axis.