IUBio

carbon dating for age determination

Tom McCloud mccloud-tom at worldnet.att.net
Sat Jun 28 18:43:43 EST 2003


On 28 Jun 2003 23:07:09 GMT, mydogatemypw at aol.com (Mydogatemypw)
wrote:
>ok silly me, but substitute skeleton on corpse for ceramic bowl and explain
>this to me then

All living organisms, plants, animals, microbes, utilize carbon in
some way.   Both isotopically stable C12 and radioactive C14  (as well
as paramagnetic C13)  are naturally present in the environment in
fixed amounts.  Since those enzymes carrying out metabolism in a
living organism essentially cannot tell any difference among the
carbon isotopes, all those isotopes get incorporated into sugars,
amino acids, proteins, fats, nucleic acids, etc.

When the organism dies, the carbon in that organism is 'fixed' as it
were, presumably no flux or exchange is occurring with carbon in the
environment any longer.   So since no C14 is being 'added to the
closed system', the amount of C14 contained can only decrease with the
age of the material.    Therefore,  if one carefully measures that
admittedly very small amount of C14,  that quantity is related to the
length of time since the organism died.   Now there are assumptions
being made.  The half life of C14 is an estimate, and the rate of
decay is assumed to be constant.   Contamination of an old sample with
environmental carbon will throwoff the date estimate.   The measured
or determined date is generally given within a certain 'range' of
years, because the method cannot be made any more precise. A range of
even several thousand years for an old specimen is not unusual. 
        Tom McCloud



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