Our moon being formed.

[u/howimetyourcakeshop]

[u/OneGalacticBoy]

If you know the current position and movement of both bodies, and the laws of motion, you can wind the clock back and predict what probably happened. Fun fact, the moon moves further away from the earth every year even now.

[u/Universe_XoX → u/OneGalacticBoy]

That actually does kinda make sense, never thought about it like that before.

So pretty much the momentum of that impact is still being shown right now in the lunar and earth spinning.

[u/majikmonkie → u/Universe_XoX]

Yeah, sort of. We know the moon is made of mostly the same stuff as earth, with some differences. And on earth we see some similarities in different proportions. It's those slight differences that lead to the theory of another celestial body colliding. Then they run millions of different models with varying sizes, material compositions, initial conditions (spin, momentum, direction, etc.) and then look for convergence of the models with current or known conditions. If you've got a number of models that tend to show the conditions we see, then you can theorize that you're on the right track.

The earth's spin is only one of the aspects. The moon doesn't spin, but rather wobbles slightly, as it's tidally locked. I'd imagine it was spinning atbone point and because tidally locked due to proximity and gravitational effects (this is fairly common with systems with a larger and a smaller body).

[u/killfirejack → u/majikmonkie]

The moon does spin, though... It rotates once per rotation of the earth, hence the same side is always facing earth.