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Name: Brian
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Question:
If we could change the rotational speed of the moon, would this momentum change necessarily change its orbital parameters?



Replies:
Brian,

In the short run, giving the Moon a spin would not affect its orbit around the Earth. In the long run, the energy of that spin might gradually be transferred to its orbital motion and consumed, by means of tidal deformation of the moon. Personally I do not how much coupling to tidal stresses happens in a cold, all-solid body like the Moon. The degree of coupling could be much less than that of largely-fluid Earth if the moon is infinitely rigid or perfectly elastic, or it could be much greater if there is any yield or crumbly sliding deformation within the body.

Perhaps you have heard: the spin energy of the Earth has been partly transferred to moon's orbit over the time since the Moon was created, driving the Moon farther out and slowing the Earth's day/night cycle. This is the type of coupling I am referring to above.

Jim Swenson


Brian

If you are speaking about the rotational speed of the moon on its axis, Then no, that will not affect its orbital parameters.

If you change the speed of the moon's orbit around the earth, the moon will move out to a more distant orbit until its velocity vector parallel to the surface of the earth equals its velocity Vector that points toward the center of the earth.

Sincere regards,

Mike Stewart



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