Reflectorites
On Thu, 02 Mar 2000 13:56:04 -0800, Tedd Hadley wrote:
[...]
>
> Somehow, this "adjustment" went from uncertain in Jones' article
> to all but certain in your post. Keep the following statements
> from the article in mind:
>
>| Such fine distinctions matter, for example to researchers who are
>| using the decay of potassium-40 (half-life of 1.25 billion years)
>| to sort out the mass extinction of 250 million years ago (Science,
>| 15 May 1998, p. 1007). But, although potassium-40, like beryllium-7,
>| decays by electron capture, its innermost electrons-the ones most
>| likely to be snagged-are more strongly shielded from external
>| effects. The potassium ion has two complete shells of electrons
>| protecting its two innermost electrons, whereas the beryllium ion
>| has none. Thus, researchers expect the effect of chemical form on
>| potassium-40 to be far less than on beryllium-7.
My understanding is that the Cambrian Explosion has been dated by the
Uranium-Lead method in single Zirconium crystals.
"Zircon dating, which calculates a fossil's age by measuring the relative
amounts of uranium and lead within the crystals, had been whittling away
at the Cambrian for some time. By 1990, for example, new dates obtained
from early Cambrian sites around the world were telescoping the start of
biology's Big Bang from 600 million years ago to less than 560 million
years ago. Now, with information based on the lead content of zircons
from Siberia, virtually everyone agrees that the Cambrian started almost
exactly 543 million years ago and, even more startling, that all but one of
the phyla in the fossil record appeared within the first 5 million to 10
million years. "We now know how fast fast is," grins Bowring. "And what I
like to ask my biologist friends is, How fast can evolution get before they
start feeling uncomfortable?" (Nash J.M., "When Life Exploded", Time,
December 4, 1995, p74)
I presume that now they know that different compounds of the same
elements may have different rates of geophysicists will re-examine all the
data as well as their previous uniformitarian assumptions.
It may be that previous anomalies between different compounds might
become new data..
Since Tedd is new to the Reflector I wish to make it clear that while I am a
creationist, I am not a *young-Earth* creationist. While I agree with YECs
that radioactive dating can be unreliable, I do not believe they have yet
established that it is so unreliable that it can be out by a factor of about
*half a million* so that a real 10,000 years looks like an apparent 4.6
billion years.
But I do consider it likely that radioactive dating may have been adversely
influenced by evolutionary expectations of long time-frames, which are
now being reduced as more information becomes available.
Steve
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"The point of my letter (Science's Compass, 30 July, p. 663), which
perhaps was not well articulated, is that there is one hypothesis, central to
evolution, that remains barely tested-that evolution proceeds through the
process of survival and reproduction of the fittest." (Hogg, David. W.,
Science, Vol. 286, 26 November 1999, p167)
Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones
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