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From: hull@hao.UUCP (Howard Hull)
Newsgroups: net.astro
Subject: Re: C14
Message-ID: <1667@hao.UUCP>
Date: Wed, 31-Jul-85 02:14:56 EDT
Article-I.D.: hao.1667
Posted: Wed Jul 31 02:14:56 1985
Date-Received: Thu, 1-Aug-85 06:24:33 EDT
References: <173@husky.uucp>
Organization: High Altitude Obs./NCAR, Boulder CO
Lines: 17

Says Mark A. Johnson:
> 	                 My understanding is that the C12/C14 ratio in
> 	an organism approached zero asymptotically with passing time
> 	(e^-at) following the creature's death, since C14 is no longer
> 	being moved through the living organism.  Where does the initial
> 	atmospheric C14 concentratio data come from?  Simply assuming
> 	that C14 concentration is constant since the beginning of time
> 	seems questionable to me, at best.  How 'bout it, folks?
I'm no expert, but, I think the C14 comes from cosmic ray disintegrations
(some of which may be due to energetic solar protons).  Solar activity may
not have been strictly constant over time, but researchers can compensate
for this by referencing other isotope abundances, and by correlating this
with ice strata thicknesses in Antarctica and Greenland.  Another exciting
thing is that modern Accelerated Mass Spectrometers can find as little as
*10 Atoms* of, say, Beryllium 10 in some samples carefully prepared for
spectroscopy!  Such studies are being used to bolster the C14 data.
Howard Hull	{ucbvax!hplabs | allegra!nbires | harpo!seismo } !hao!hull