Expert: Jayendra Upadhye - 3/2/2007

Question
I don,t think the moon's spin cancels it's orbit by accident(causing the same side to face Earth)That would be one big coincidence. I think that the moon's center of gravity is offset from it's center of volume.  "The heavy side faces us" Do you agree that this could be possible?


Answer
Hi richie,
No that is not the reason.

The reason is fairly well known to students of astronomy, and is result of tidal locking of a satellite by its parent.

Many other satellites in the solar system exhibit this behaviour and i believe mercury, the closest planet to the sun also shows this behaviour.

The mechanism of tidal locking is well known and described on number of www sites.

go into google and just type in tidal locking of the moon.
you wil get many pages.
type my name and tidal lock and perhaps my old answers on the subject will crop up, where i have actually given links to the sites. my cybercafe today is very slow and hence i cannot do so now.

The consequence of this process is also increase in the moons orbital speed, a slowing down of the earth, and the moon receding from the earth at 4 cm/year!!
[law of conservation of earth-moon system angular momentum].

read all about it on the web!
Jayen