17001_1511@uwovax.uwo.ca (11/12/90)
Angular momentum in a system evolving towards synchronous rotation:
Angular momentum has to be preserved - several people pointed this
out - and it is. As the total rotational angular momentum changes due to
slowing of rotation (on both bodies), the orbital characteristics of the
system change in step. For instance, right now the Moon is in synchronous
rotation, but Earth is not (the fully evolved system is that of Pluto and
Charon, both rotating synchronously with their orbital motion with respect
to each other). Therefore the Moon brakes the Earth, and the angular momentum
which is lost from Earth's slowing is made up by an increase in the Moon's
orbital radius.
Phil Stooke,
Department of Geography,
University of Western Ontario,
London, Ontario, Canada N6A 5C2