Re: Laurence Kulp
George Murphy (gmurphy@raex.com)
Wed, 08 Dec 1999 15:57:46 -0500
Diane Roy wrote:
>
> I have been reading Numbers' "The Creationists" (again) and came across something I'd like to get clarified.
>
> According to Numbers, J. Laurence Kulp led many of the ASA (in 1948) in "boldly shedding the trite fundamentalist apologetics of the past." [i.e. Flood geology
>
> Here is where I'd like some clarification. In 1948, Kulp presented a paper at the ASA convention on the antiquity of man. Afterwards he pointed out that "only
>
> Here is why I wonder if Numbers got it right. The reason geologists would be concerned about a uniform rate for radioactive disintegration is so that one can t
>
> All measuring tools must be long enough (or short enough) to be able to be used accurately. One would not use a yard stick to measure the dimension of an atom,
>
> Here is why I'm puzzled by Kupl's statement: "only one assumption -- a uniform rate of radioactive disintegration -- was necessary to prove a very old earth."
>
> Help me out here.
>
> Allen
>
> ---------------------------------------------------------------
>
> I have been reading Numbers? "The Creationists" (again) and came
> across something I?d like to get clarified.
>
> According to Numbers, J. Laurence Kulp led many of the ASA (in 1948)
> in "boldly shedding the trite fundamentalist apologetics of the past."
> [i.e. Flood geology] (p165) And that, "Largely because of Kulp?s
> powers of persuasion, flood geologists found themselves increasingly
> isolated within the ASA." (p169) Kulp, a chemist and geologist,
> studied under Libby, Fermi and Urey and set up the "second carbon-14
> laboratory in the country," and then pioneered "in the application of
> radiocarbon dating to the geological problems," (p163)
>
> Here is where I?d like some clarification. In 1948, Kulp presented a
> paper at the ASA convention on the antiquity of man. Afterwards he
> pointed out that "only one assumption -- a uniform rate of radioactive
> disintegration -- was necessary to prove a very old earth." (p164) Is
> this still the general consensus among those of the ASA? Does Numbers
> correctly explain Kelp's position?
>
> Here is why I wonder if Numbers got it right. The reason geologists
> would be concerned about a uniform rate for radioactive disintegration
> is so that one can then compute the age of organic material (in the
> case of 14C) or magma (in the case of other radiometric schemes). If
> it happened to be non-uniform, then there might be problems, but
> scientific evidence does seem to point to a fairly uniform rate for
> most radioactive elements.
>
> All measuring tools must be long enough (or short enough) to be able
> to be used accurately. One would not use a yard stick to measure the
> dimension of an atom, nor use a yard stick to physically measure the
> distance between the earth and the moon. It is assumed that whatever
> is to be measured corresponds to the measuring device one uses. In the
> case of radiometric dating magmatic rocks one must assume that the
> rocks have existed for as long as radiometric dating can measure.
> Otherwise, what is the point of trying to measure the date. If the
> rocks are much older than the measuring tool can reach then why
> bother. In fact, this very idea is why no one bothers to measure the
> age of non-mineralized "fossils" found in rock much older than the
> 100,000 year limit of 14C. The same would hold true, if rocks were
> actually much younger than what the measuring tool might seem to
> indicate.
>
> Here is why I?m puzzled by Kupl?s statement: "only one assumption -- a
> uniform rate of radioactive disintegration -- was necessary to prove a
> very old earth." (p164) We all know that you cannot prove what you
> assume. Since we must first assume the rocks are old enough to be
> measured, the measuring device cannot be used to prove that the rock
> is old. Yet Kulp appears to do just that. Radiometric dating proves
> an old earth, but an old earth must first be assumed in order to use
> radiometric dating. Wasn?t Kulp aware of this false twist of logic?
> Surely such a highly educated and knowledgeable student of the
> sciences would not make such a glaring mistake as this. Or, Did
> Numbers misrepresent Kulp?s position?
I can't help much with the history or geology, but can with the physics. The
half-life of a radioactive isotope can be measured on a time scale significantly less
than that half-life. E.g., the half life of U-238 can be determined as about 4.5
billions years but you don't have to wait that long (which is about current estimates of
the earth's age) in order to determine that parameter.
If radioactive decay is a purely statistical process, the number of atoms
decaying per unit time at any instant in a given sample will be proportional to the
number of atoms N present at that instant. The proportionality constant in this
relation is related to the half-life, the time it will take for N to decrease to half
its initial value. Thus by measuring the rate of decay of a sample the half-life can
be determined without actually waiting for half the sample to decay.
What we can't determine simply from laboratory measurements is that the
proportionality constant, & thus the half life, doesn't change on a geological time
sclae, so we have to make the assumption that Kulp mentions. But this is not pure
hypothesis: Some observational and theoretical constraints can be placed on
possible variations of decay rates.
Shalom,
George
George L. Murphy
gmurphy@raex.com
http://web.raex.com/~gmurphy/