Alpern.IBM-SJ%Rand-Relay@sri-unix.UUCP (10/21/83)
From: David M. Alpern <Alpern.IBM-SJ@Rand-Relay> Max Ewell commented in his recent note on "Scientific Creationism" that the best estimates of the earth's age come from measurements made on the radiation from long-lived elements. I've always wondered where the boundary knowledge for such measurements comes from. For example, I've been under the impression that fossil dating assumes that the concentrations of various isotopes in the human body has been reasonably constant throughout the generations, and thus that the original radiation was at a level equal to that of a modern human (on whom we can take measurements). But how does one gain reasonable information on the original concentration of various radioactive isotopes on the planet? How wrong is my understanding of the radioactive dating process? Thanks for any enlightenment you can provide. - Dave p.s. Anybody need a name for a post WW-3 matchmaking service?
gwyn%brl-vld@sri-unix.UUCP (10/23/83)
From: Doug Gwyn (VLD/VMB) <gwyn@brl-vld> The specifics of radioisotope dating are tailored to the particular circumstances. Sometimes the relative abundance of isotopes of an element varies for difference sources of the element (e.g. C-14). Sometimes decay products are found mixed in substances where the decay products would not normally be found (e.g. Pb). Any good archaeology text will explain several fossil dating techniques. Any good geology text will explain mineral dating techniques. One very important point is that these methods have cross-checks for consistency, so there is little danger of radically wrong results remaining undetected for very long.