I have a hard time finding an answer to this question: We have all learned that there is a “far” side of the Moon due to the rotation and orbit being “the same”.  This is even though parts of the far side can be seen at times.  My question has always been, are the orbit and rotation really the “same”?  I think of mountains that rise and  fall compared to sea level maybe inches in hundreds or thousands of years.  If not exact, is the Moon slowly turning compared to the Earth?  Could the far side of the Moon become the close side in say 10 million years?  Please satisfy my curiosity.

While the moon is actually moving always from the Earth and the Earth’s tilt coupled to the Moon’s eccentricity in it’s orbit allows us to see more than just 50% of the Moon’s surface, it is indeed locked into it’s current configuration forever and ever (barring any major catastrophe, e.g. a major impact).  At the same time the Moon is moving away from the Earth, the Earth is also slowing down it’s rotation such that ultimately, it will be locked into having the same side of the Earth always facing the Moon as well.  At that point, the Moon will rotate around the Earth at the same rate that the Earth rotates on its own axis.  This transfer of energy happens through tidal friction and can be seen in other “tidal-locked” planetary bodies as well: for example, Pluto and its largest moon Charon.

Brad Bailey

NLSI Staff Scientist

April 16, 009

NESF 2020

Lunar Landing Workshop

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