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From: chiaraviglio@husc2.UUCP (lucius)
Newsgroups: sci.bio,sci.astro
Subject: Re: Mass extinctions
Message-ID: <1256@husc2.UUCP>
Date: Fri, 17-Apr-87 20:10:59 EST
Article-I.D.: husc2.1256
Posted: Fri Apr 17 20:10:59 1987
Date-Received: Sun, 19-Apr-87 13:04:25 EST
References: <6760@alice.uUCp> <496@uokmax.UUCP> <260@rlvd.UUCP>
Organization: Harvard Univ. Science Ctr., Cambridge, MA
Lines: 35
Summary: Reverse rotation of crust relative to core won't work.
Xref: mnetor sci.bio:319 sci.astro:898

In article <260@rlvd.UUCP>, kgd@rlvd.UUCP (Keith Dancey) writes:
> Another interesting theory that I have heard put forward by Dr Clube is the
> possibility of meteor impact of sufficient momentum to reverse the rotation
> of the Earth.  The molten core would continue to rotate as before, but the
> solid crust would be knocked into temporary reverse.  Eventually, frictional
> forces would capture and return the crust rotation to its original direction.

	This won't work.  The only internal layer of the Earth that is really
fluid with respect to rapid shear (as reversed opposite relative rotations
would require) is the outer core.  Between the outer core and the crust you
have the mantle, which is more than half the Earth's mass (way over half the
volume) and is for all practical purposes solid (some circulation over
geological times may be possible, but no rapid shear).  Therefore, if you
reversed the direction of rotation of the Earth's crust you would also reverse
the direction of most of the Earth's mass and

	1.	The whole Earth would end up spinning in the reverse
		direction -- remember that not only is the core less
		than half the mass of the Earth but it is also less
		than half the diameter, so that its rotational intertia
		is disproportionately smaller.


	2.	The impact needed to produce such a reversal would
		be so huge that probably everything except the hardiest
		organisms -- indeed likely everything -- would be killed.
		This obviously has not happened.

-- 
	-- Lucius Chiaraviglio
	   lucius@tardis.harvard.edu
	   seismo!tardis.harvard.edu!lucius

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