From: Donald Nield (d.nield@auckland.ac.nz)
Date: Thu Oct 02 2003 - 21:30:13 EDT
allenroy wrote:
> "D. F. Siemens, Jr." wrote:
>
> > I did a quick search by Google on "Carbon 14." First, the ratio of
> > radio-carbon in contemporary living things is about 10^-12. This is the
> > 100% level, approximately, for there are technicalities to the standard.
> > Measurement by the most advanced techniques gets down to a little more
> > than 1%, for an age of 40,000 years. Theoretically, the newest techniques
> > might get to 60K, but the practitioners say it doesn't work. In other
> > words, 0.1% is a full order of magnitude better than the best labs get.
> > Do you suppose it's artifactual?
>
> >From http://www.icr.org/pubs/imp/imp-364.htm (ICRs Impact #364)
> "The AMS (Accelerator Mass Spectrometer) method improved the sensitivity of the
> raw measurement of the 14C/12C ratio from approximately 1% of the modern value
> to about 0.001%, extending the theoretical range of sensitivity from about
> 40,000 years to about 90,000 years. The expectation was that this improvement in
> precision would make it possible to use this technique to date dramatically
> older fossil material.1"
>
> from http://www.talkorigins.org/faqs/c14.html (Talk.Origins Archives and
> FAQS)
> "Dr. Gove and his colleagues are currently trying to improve AMS technology to
> be able to identify certain fossil fuels that have extremely low 14C content.
> Current AMS techniques have a 14C/C detection limit of about 10^-15
> (corresponding to 60,000 yrs), and Dr. Gove's current research, this year, is
> aimed at improving detectability to 10^-18 (110,000 yrs)."
> "Their ultimate goal is to reliably measure 14C/C ratios down to the
> unbelievably low levels of 10^-22 (180,000 yrs). "
> This Talk.origins paper talks about possible in-situ occurrence of 14C due to
> several factors and the site ends with:
> "So, it looks like in-situ production of new 14C is the best-supported
> hypothesis; but research is ongoing, and I look forward to seeing the results of
> the Old Carbon Project and new research on the deep subterranean bacteria."
>
> Impact #364 say this about contamination.
> "The big surprise, however, was that no fossil material [other than oil] could
> be found anywhere that had as little as 0.001% of the modern value! Since most
> of the scientists involved assumed the standard geological time scale..., the
> obvious explanation for the 14C they were detecting in their samples was
> contamination from some source of modern carbon with its high level of 14C.
> Therefore they mounted a major campaign to discover and eliminate the sources of
> such contamination. Although they identified and corrected a few relatively
> minor sources of 14C contamination, there still remained a significant level of
> 14C—typically about 100 times the ultimate sensitivity of the instrument—in
> samples that should have been utterly "14C-dead," including many from the deeper
> levels of the fossil-bearing part of the geological record."
>
> Allen
OK, what does this tell us? From the ICR's own information we learn that the
methodology works OK down to a ratio of 0.001% of the modern value, that is 10^(-5)
of that value, so the method works OK for about 17 half-lifetimes of C14, that is
about 10^5 years. That is no help to the YECs !
Don
-
This archive was generated by hypermail 2.1.4 : Thu Oct 02 2003 - 21:32:25 EDT