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James Shields suggests that the tilt of the earth may have
changed during the last few billion years and changed the
temperature gradient between poles and equators.
Not so! The tilt of the axis of Mars is unstable and chaotic,
wandering all over the place on a scale of millions of years.
Jack Laskar published a paper on this in Nature, about 3 years
ago. If y ou really need it I will look it out.
Venus started the same way up as all the other planets but the
axis tilted right over at some time, and now Venus is upside
down. This is more stable than right way up. Mars is spinning
in the same direction as it it revolving around the sun; Venus
is spinning in the *opposite* direction which is far more stable.
Earth's axis h as not behaved like this because of the stailising
effects of the moon. Resonance between the earth and the moon is the
cause both of the moon keeping the same face to us
AND for stabilizing the earth's axis. The axis of the earth
has not varied by more than a degree in 4 billion years.
Another possible partial explanation for conditions on the north
slope of Alaska during the Cretaceous is that the tectonic plate
was drifting (as usual), but also turning. Since the K-T North
America has turned about 30 degrees anticlockwise. During the
Cretaceous the North Slope was the northernmost part of the
continent, farther north (closer to the north pole) than the
Canadian Arctic Islands.
A quite different subject: I 'm a total novice at the network
and I keep in screwing up. A couple of days ago I lost
completely something that interested me. Whoever it was that
suggested a JOURNAL OF PALEOHERPETOLOGY had a good idea, and
I've lost all trace of the article. I might even be prepared
to offer to h elp with editing such a j ournal. Please get in
David (and don't you dare call me Dave)
>From: David Brez Carlisle