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Re: orion-list Radiocarbon

> From owner-orion@panda.mscc.huji.ac.il Sat Aug 28 00:09:51 1999
> >Hence a radiocarbon 
> >date after 63BC indicates that the material the scrolls are made from 
> >was still alive after 63BC and thus could not have been deposited
> >on or before that date. 
>    Nope.  The dates are the LATEST possible.  Since we have NO 
>    protocols showing how the effects of contamination were taken
>    into account we must assume these are the LAST dates possible. 
>    IOW, tests done on uncontaminated samples would show EARLIER
>    dates.

You seem to be questioning the underlying theoretical understanding
of the method here. In a living system the ratio of C-14 to C-12 
is in equilibrium with the environment. Once the system is dead
there is no mechanism to maintain that equilibrium hence the ratio
of C-14 to C-12 changes as the C-14 decays. But if I understand your
argument correctly you are saying:-

(1) The equilibrium state is maintained until deposit.
(2) Contamination in modern times makes the samples appear younger.

I don't think (1) is right. If this is what you are claiming can you 
explain a mechanism whereby the C-14/C-12 ratio in the scrolls are 
kept in equilibrium with the environment after the material is no
longer living.

The problem of (2) is supposed to be addressed by the cleaning of the

>    Some, possibly, but each present serious questions.  There are
>    FOURTEEN others earlier than 63 BC.  Unless you can show evidence
>    of multiple deposits - which would help explain the dating dif-
>    ferences - you must consider the whole deposit.

But this assumes (1) above. I think the *method* of radiocarbon
dating determines the date of the death of the organic material 
on which the scrolls were written. A simpler explanation for
the different dates is that the scrolls were "manufactured" over
a lengthy period of time.


>    Irrelevant.
>    You seem to have ignored my layman's argument showing how rapidly
>    contamination can skew results.
>    Again, you fail to consider that the dates reported are the
>    latest for each artifact, not the earliest.  Until the contamin-
>    ation issue is fully addressed, you're stuck with what's there.

I haven't failed to consider this, at this point I don't believe it.
Provide me with a mechanism to keep the C-14/C-12 ratio in equilibrium
with the environment and I'll come round to your point of view.
Yes, the contamination issue is real, but on this I have to bow to the
superior knowledge and experience of the AMS people.  

Bill Rea, Information Technology Services, University of Canterbury  \_ 
E-Mail b dot rea at its dot canterbury dot ac dot nz                 </   New 
Phone   64-3-364-2331, Fax     64-3-364-2332                        /)  Zealand 
Unix Systems Administrator                                         (/' 

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