On Wed, 29 Dec 2004 03:44:28 -0800, "Ed Price"
wrote:

At first, you might think this was just a one-day aberration, but if you
redistribute enough mass on our rotating globe, you should be able to make
permanent changes in the rotational velocity. And that makes me think it
might be a permanent change (permanent until the next big mass
redistribution event).

I believe you are right. If a chunk of crust was subsumed into the
mantle (i.e. "went down and got melted"), this would increase the
rotation of the earth fractionally in the same way a skater doing a
spin increases her rotation as she draws her arms tight toward her
chest (same mass rotating in a smaller radius).

By the same token, a sufficiently large volcanic event that pushed a
lot of magma to the surface would fractionally SLOW the earth's
rotation, and likely produce even more navigational hazards and
Notices to Mariners. G

The earth's rotation has been slowing due to gravitational/tidal drag
since its creation, and the moon is creeping ever farther away.

Give it enough time, and tides will drop and total eclipses will
become impossible. I, however, don't expect to be sailing then G.

I often think that going back in a time machine wouldn't be
interesting for the biology (very little on land before 300 million
years ago anyway), but for the astronomy: a 20 hour day and the
biggest moon you'll ever see. Highest tides, no doubt, as well.

R.