h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Something I have never understood about carbon dating:

Why do all plants maintain a constant level of Carbon 14 when they are alive?

Well plants get their carbon form the atmosphere, by removing carbon dioxide and realising oxygen. The levels of carbon 14 in the atmosphere remain constant, as it is produced when the atmosphere reacts with radiation form space.

Fishboy

Isn't there a thought going round that levels of C14 have shown fluctuations, i.e. that it's not been completely constant to allow for guaranteed radiocarbon dating?

IIRC there was this chap on the radio talking about the "catastrophic" (don't you just love their choice of words?) effect of major volcanic eruptions etc etc on ambient C14, which would then stabilize after a period of time. Net result is that anything which came from that period of instability would be inaccurately dated.

I'm not sure if this is verifiable, crackpot or merely theory yet to be proved (or not as the case may be), but Shroud-watchers seem to have taken it to mean that the Shroud could still be the real thing

After all, wasn't it from the Nine O'Clock News:
Be the first in your in crowd
To wear a T-Shirt of the Turin Shroud
You'll be so proud
Of your Turin Shroud
T-Shirt. Amen

OK, that was the bit I was missing - the reason that carbon 14 levels in the atmosphere remained constant. It had always struck me that the half life of carbon 14 must surely be the same for an atom whether it's in a live plant, a dead plant, or out in the atmosphere.

I wonder why you never hear the part about atmospheric levels being kept constant by background radiation, since without that the whole process makes absolutely no sense...

I just wanted to say that my entry was originally much larger, and that I had to split it in half, as people were dying of old age before they even got half way through.

The 'missing' half refers to a theory I discovered in a book by Christopher Knight and Robert Lomas. As far as I know it hasn't received a great deal of publicity, which is a shame as it seems highly plausible (note that I use the word 'plausible' rather than truthful'!)

http://www.h2g2.com/A256934

How much do they back up the theory with documentary evidence?

A lot of this reads a lot like The Holy Blood And The Holy Grail - a fascinating book, but one which has been pretty much discredited... It seems like pushing misinformation on the Knights Templar has been a popular hobby for many in Europe over the last 2 centuries, so it's very hard to know what's true and what isn't now.

(Not trying to put down your entry or anything - it's very interesting, it just contains a lot of information, and I'm intruiged to see what's it's based on.)