Path: utzoo!mnetor!uunet!wucs1!wucs2!slustl!slu70!guy
From: guy@slu70.UUCP (Guy M. Smith)
Newsgroups: sci.misc
Subject: Re: more Velikovsky
Message-ID: <116@slu70.UUCP>
Date: 23 Mar 88 14:37:31 GMT
References: <5236@uwmcsd1.UUCP> <1138@PT.CS.CMU.EDU> <5250@uwmcsd1.UUCP> <5300@uwmcsd1.UUCP>
Organization: St. Louis Univ., St. Louis, MO
Lines: 14
Summary: radiometric dating

In article <5300@uwmcsd1.UUCP>, markh@csd4.milw.wisc.edu (Mark William Hopkins) writes:
> In article <4006@cup.portal.com> roger_warren_tang@cup.portal.com writes:
> >   "Radiation counts used to date things before a supposed catastrophe cannot b
> Because the catastrophe itself may be a large source of radiation.
External radiation is irrelevant to radiometric dating. The technique involves
measuring the amounts of specific radioactive isotopes (e.g., Rb^87) and
their stable daughter products (Sr^87 in this case). Crudely, the Rb/Sr
ratio is controlled by the age of the rock as Rb converts to Sr at a
known rate. External radiation has no influence on the rate of decay.
The fact that the rock may emit radiation, from whatever source, is
irrelevant as the isotope abundances are generally measured on a mass
spectrometer. A more detailed explanation can be found in most books
on igneous petrology (e.g., Hyndman). I teach this subject in my classes
so I think I can claim at least minimal expertise.