Name: Unknown
Status: Other
Age: N/A
Location: N/A
Country: N/A
Date: Prior to 1993
Question:
I have heard that the moon and earth are slowing in their
respective rotations due to the gravitational attraction between them. Does
this mean that an earth day was shorter in the past?
Replies:
Yes, in fact the angular momentum of the earth-moon system
remains constant, but tidal forces cause a kind of friction that slowly slows
the earth's rotation. In order to conserve angular momentum, the moon's orbit
is slowing increasing its diameter. It is interesting that we (humans) exist
right now because some millions of years ago the moon would have been closer
and looked larger and total solar eclipses would not have been as spectacular
as they are now. Similarly, some millions of years in the future, the moon
will be further away, will look smaller, and there will never again be a total
solar eclipse, only annular eclipses. We just happen to be living during the
relatively small period of time when the moon and sun have the same apparent
size as seen from the earth!
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