One important change in the Earth-Moon system hasn't been mentioned. If
the Earth's rotation changes directions but all other orbital parameters
(e.g. Moon's orbit) don't change, tides would change the nature of the
Earth-Moon system.
Currently, the tidal bulges on Earth rotate ahead of the Moon, relative
to the Moon's revolution around the Earth because a day is shorter than
a month. Over the long term, this leads to the Moon slowing the Earth's
rotation down as it pulls the tidal bulges back towards alignment. The
slowing occurs primarily via friction between water and the ocean floor.
Similarly, these tidal bulges cause the Moon to recede from the Earth
approximately 4cm/yr. Over approximately 100 million year, this process
has slowed the Earth's rotation from 22hr/day to the current 24hr/day,
and has increased the size of the Moon's orbit accordingly (conservation
of angular momentum).
Reversing the direction of the Earth's rotation and not the Moon's
revolution direction would reverse this effect. Days would get shorter
and the Moon would get closer. Over a few hundred million years, this
would have a noticeable effect on both the Earth and the Moon. For
example, tides would be stronger. This could significantly alter coastal
areas, independent of weather or climate patterns.
Neptune's moon Triton is experiencing this effect because its orbit is
retrograde. Mars' Moon Phobos is also getting closer to Mars because its
revolution rate is faster than Mars' rotation rate. It will actually
crash into Mars or be tidally disrupted in approximately 50 million
years.
David Vakil
Astronomy & Physics Professor
El Camino College
310-660-3134