From: D. F. Siemens, Jr. (dfsiemensjr@juno.com)
Date: Fri Oct 03 2003 - 22:49:39 EDT
Al,
I cannot speak definitively, but my impression is that the quotation
included AMS. I gathered that its benefit was not so much that it could
measure smaller percentages in the ratio, but that the measurements
require much smaller quantities of carbon or carbon dioxide. Your
suggestion of noise in the measurement seems to be buttressed by other
parts of the site I cited. Were the Creation Research team noted for
meticulous investigations and exact citation, I'd be more apprehensive of
a discovery.
Apparently the radiocarbon dates have been calibrated by bristle-cone
pines back 10K BP. An earlier CRSQ article claimed that the pines
sometimes produced two rings in a year. With the Flood 4350 BP, they must
produce at least two rings every year, and often three. I think that is a
bit much of a fudge factor.
Dave
On Fri, 3 Oct 2003 15:17:50 -0400 Mccarrick Alan D CRPH
<MccarrickAD@nswccd.navy.mil> writes:
The preferred method of C14 dating is to use a mass spectrum to actually
separate the carbon isotopes. This does not involve counting radioactive
decays which would be subject to background decays. Atomic Mass Spec
(AMS) in principle would be much more sensitive. The claim of the ICR
publication is that those samples which are expected to have zero C14
left appear to have residual C14.
I still wonder whether the problem still lies in the noise when looking
at the lowest amounts of C14. They do report attempts to exclude
contamination in several ways. They hint that isotopically pure "zone
refined, reactor grade graphite samples" were tested by the anonymous
laboratory - although the results were not given (p. 10).
Al McCarrick
-----Original Message-----
From: D. F. Siemens, Jr. [mailto:dfsiemensjr@juno.com]
Sent: Friday, October 03, 2003 2:59 PM
To: allenroy@peoplepc.com
Cc: asa@calvin.edu
Subject: Re: RATE
On Thu, 02 Oct 2003 17:33:20 -0700 allenroy <allenroy@peoplepc.com>
writes:
>
> 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.c14dating.com/agecalc.html
It is vital for a radiocarbon laboratory to know the contribution to
routine sample activity of non-sample radioactivity. Obviously, this
activity is additional and must be removed from calculations. In order to
make allowances for background counts and to evaluate the limits of
detection, materials which radiocarbon specialists can be fairly sure
contain no activity are measured under identical counting conditions as
normal samples. Background samples usually consist of geological samples
of infinite age such as coal, lignite, limestone, ancient carbonate,
athracite, marble or swamp wood. By measuring the activity of a
background sample, the normal radioactivity present while a sample of
unknown age is being measured can be accounted for and deducted.
In an earlier section we mentioned that the limit of the technique is
about 55-60 000 years. Obviously, the limit of the method differs between
laboratories dependent upon the extent to which background levels of
radioactivity can be reduced. Amongst accelerator laboratories there has
been mooted the theoretical possibility of extended range dating to 75
000 yr +, at present this seems difficult to attain because of the
problems in accurately differentiating between ions that mimic the mass
and charge characteristics of the C14 atom. Beukens (1994) for instance
has stated that this means the limit of the range for his Isotrace
laboratory is 60 000 yr which is very similar to the conventional range.
End quote.
Looks to me as though the ICR report exaggerates the limit and involves
mistaking background for age.
Dave
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