Re: [asa] Denver RATE Conference (Thousands...Not Billions)_Part 2

The general background radiation limits C14 to about 50-60KYears

<quote>
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.

</quote>

http://www.c14dating.com/agecalc.html

To me the YEC arguments appear to be highly misleading as the noise
level would lead to a typical max age based of 50-60k.

On 9/25/07, Jon Tandy <tandyland@earthlink.net> wrote:
> Kirk,
>
> It sounds like what you are saying is that the measurement process
> (instrument?) itself yields a "background" of C14 roughly equal to an age of
> 40,000 years. Thus a measurement of 40,000 years old for a diamond equals
> the measurement of C14 from the AMS background, plus zero C14 from the
> diamond itself. Is this about right?
>
> If so, I suppose the process of calibrating the instrumentation is much more
> involved and has much more history and "check and balance" than what
> Baumgardner has represented. But still (and I'm not disputing the age of
> the earth), the last paragraph below seems on the surface a little like the
> scientific "circular reasoning" that YEC claims to expose. If the diamond
> is used to calibrate the instrument because it is "known" to have no C14
> (due to its great age), isn't this assuming the conclusion as part of the
> proof? What if the diamond really isn't that old, and/or really does have
> some C14 in it? How would we know, if that assumption is taken at the
> first?
>
> I can envision some answers to this, but don't have the technical expertise
> to know for sure how certain they are.
> 1. There are (hopefully more than one) independent methods of determining
> the great age of diamonds that doesn't depend on the C14 assumption or other
> initial condition or uniformitarian assumptions.
> 2. When fossils from the Paleozoic, Mesozoic, and Cenozoic ages all come out
> with the same age, that is "red flag" evidence that something is wrong with
> the measurement, because the evidence is abundant that those geologic layers
> are from different ages based on type of fossil content, other dating
> methods such as radioisotope, etc. This is of course disputed in YEC
> literature, but there is much evidence for the geologic age of the earth.
> 3. Perhaps there are other semi-independent means of calibrating the
> background AMS C14, which confirms the same quantity as obtained from
> diamond sample measurements, etc.
> 4. The C-14 measurements is calibrated back at least to a certain age, by
> measurements for instance of fossil trees or varves which clearly indicate
> multiple 10's of thousands of years. This not only shows that the
> measurement itself can in fact validate an age of the earth much greater
> than 5000 years, but also validates some of the assumptions inherent in the
> measurement.
> 5. Similar dates obtained from AMS and traditional C-14 measurement
> independently corroborate each other's measurement validity, along with
> being corroborated with other well-established dates from tree rings,
> varves, etc.
>
>
> On another subject, does anyone has any technical response to Baumgardner's
> comment on the "excess carbon may have diluted the C14 in the pre-flood
> world such that the initial C14/C12 ratio would be a lot smaller; erhaps by
> a factor of 100 - 500 times" ? This sounds to me like pure hand-waving,
> like "theory" in the common sense of "speculation" rather than the
> scientific sense of the word, simply to make a rhetorical argument that
> agrees with what the audience wants to hear, i.e., that a 5000 year old
> earth might have some scientific plausibility. Does anyone know what he's
> talking about, and what (if any) basis it has in fact or evidence?
>
>
> Jon Tandy
>
>
>
> -----Original Message-----
> From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On
> Behalf Of Kirk Bertsche
> Sent: Tuesday, September 25, 2007 12:42 AM
> To: Steven M Smith
> Cc: asa@calvin.edu
> Subject: Re: [asa] Denver RATE Conference (Thousands...Not Billions)_Part 2
>
>
> It would be interesting to know where they sent these coal and diamond
> samples, how they were prepared, and whether or not backgrounds were
> subtracted. Based on what he said earlier, I suspect he is quoting raw
> numbers without background subtraction; in this case his dates are just
> the AMS background.
>
> I found one reference to C14 and diamond in the literature (by former
> colleagues):
> http://llnl.confex.com/llnl/ams10/techprogram/P1246.HTM
> But the authors were not trying to measure C14 IN diamond. They were
> using diamond to eliminate all sources of C14 in the sample so they
> could characterize the background of the instrument itself.
>
> Kirk
>
>
>
>
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Received on Tue Sep 25 11:32:08 2007