OFF: Re: what new century?!

[Jill]

> Eric Siegerman wrote:
> > On Fri, Jan 21, 2000 at 12:48:49PM -0500, K Henderson wrote:

> > Anyway, in 'my' academic world, we denote time in BP, years before
> > present.  Of course, with the 'present' held constant at A.D. 1950.
> > Which I think is the year that radiocarbon dating was first
> > established by the folks at U.

And I think that was because it was the year that atomic testing started
in earnest and the background radiocarbon level stopped being just
minimal and solar produced!

> > Of course, this doesn't get away from the problem that a radiocarbon
> > year and a'real' calendar year aren't the same.  Like 10,000 BP 14C
> > is really 11,700 BP 14Ccal (calibrated to calendar years).
>
> Now this is just plain f***ed.  What does an RC "year" correspond
> to, then?

It's usually a radiocarbon *date* you are looking for which will
correspond
to a spread of calendar years and is then calibrated more exactly by
matching it to the known fluctuations in background radiation around the
years in question.     These fluctuations are known because objects with
absolute calendar dates (such as tree rings) have also been radiocarbon
counted so
the background radiation for that date has been established.

jill

(I hope I've got the attributions right - apologies if I've misnamed
someone)
--
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Jill Strobridge <jill at theta-orionis.freeserve.co.uk> or
J.D.Strobridge at ed.ac.uk
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