Re: Extinction

[smithjb@sas.upenn.edu (Joshua Smith)]

Michael wrote:
> 
> I agree with you.  I don't see a major bolide impact as being "fair" 
> experimentation either.
> 
> I spoke with an astonomer this morning.  He stated that the sun 
> oscillates in the plane of the galaxy enough to disturb the Ort 
> Cloud.  He also says that the sun is stable enough that fluctuations 
> in the amount of energy given off is enough to change the weather but 
> not over long periods.  However, changes in the earth's orbit as a 
> result of interaction with the other planets does happen and may be a 
> cause of the Ice Ages.  (I'm sure some of you know this, but since I 
> didn't I'm reiterating it for the masses).  The tilt of the earth can 
> change as well.  He did not say if the tilt and/or the orbit of the 
> moon could be changed enough to affect life on earth.  He did say he 
> doubted it.  He mentioned that the orbit of the moon could be changed 
> by a near miss, but I didn't get to ask about how close, how large, 
> and if so, how much change.  If it's happened in the past then it was 
> so long ago that the orbits are stable and likely to be so forever 
> without intervention.  
> 
        Yeah.  I have heard some (certainly not all) of this before.  I 
do remember hearing stuff about the orbit of the moon being altered by a 
large enough planetoid moving between it and the earth when I was in 
college.  Those folks didn't think it would do much to climate either, 
but I always thought it was a pretty cool idea, even if it didn't work.



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Josh Smith
Department of Geology
University of Pennsylvania
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