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Re: "giant molecular clouds"

Subject: Re: "giant molecular clouds"
From: Steve Willner
Date: 22 Mar 2006 16:19:56 -0500
Newsgroups: sci.astro
In article <dv7cll$8a8$1@xxxxxxxxxxxxxx>,
 spope33@xxxxxxxxxxxxxx (Steve Pope) writes:
> Solarviews.com, in a discussion of the Oort cloud and comets.

Thanks.  At first glance it looks like a nice site.  The reference I
found is at http://solarviews.com/eng/oort.htm , and as far as I can
tell the estimate of 300 to 500 Myr is a statistical average.  As I
wrote earlier, at first glance it looks high to me, but I haven't
tried to work out the correct value.  It wouldn't surprise me if
there have been a few such encounters over the age of the solar
system, but offhand I don't see how to determine exactly when they
might have occurred.  Maybe detailed study of lunar craters would
tell something.  (I'm thinking of radioisotope dating of rock samples
associated with a large number of craters -- clearly a major
undertaking.)  Does anyone know whether there's a pattern in the
dates of lunar meteorites?

-- 
Steve Willner            Phone 617-495-7123     swillner@xxxxxxxxxxxxxxx
Cambridge, MA 02138 USA                 
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