
Two Chinese Stalagmites Are a 'Holy Grail' for Accurate Radiocarbon Dating - curtis
https://gizmodo.com/two-stalagmites-found-in-chinese-cave-are-a-holy-grail-1831074289
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njarboe
Original paper links

Science (subscription required):
[http://science.sciencemag.org/content/362/6420/1293](http://science.sciencemag.org/content/362/6420/1293)

SciHub: [https://sci-hub.tw/10.1126/science.aau0747](https://sci-
hub.tw/10.1126/science.aau0747)

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bostonpete
Wouldn't Rosetta Stone be a better metaphor than Holy Grail?

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hetman
"Holy grail" is being used as an idiom and not a metaphor here.

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b_tterc_p
Idioms are colloquial metaphors

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macleginn
No, they are not. The meaning of an idiom is not predictable from its
constituent words, that’s it. A metaphor involves some kind of meaning
transfer. In this case some properties of the ‘prototypical’ Holy Grail
(desirability mostly) are transferred to the stalagmites. The source for the
transfer itself could potentially be an idiom, but in this case it’s not,
actually. The word ‘grail’, albeit rare, has a normal meaning (a kind of cup),
and ’holy grail‘ is what it is: a holy cup. We just decided based on the
strength of the literary tradition to call a particular object that way.

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nvahalik
So... how do people actually know how much C14 was in something? Does dating
only work if you know how much C14 was there originally? Otherwise how would
you be able to measure the difference between what is there and what was there
originally?

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cpburns2009
The idea is the level of C14 in the atmosphere is constant, and living
organisms will have about about the same ratio of C14 to C12. When they die
they no longer replenish the C14 so the amount decreases over time as it
decays (it's radioactive). You can then calculate how old something is based
on the ratio of remaining C14 to C12. I'm not sure what the process is that
relates C14 to stalagmite because it's inorganic.

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nitrogen
The article says they used thorium-230 dating to calibrate layered samples
from the stalagmites. This cave was special because the stalagmites did not
contain much carbon from limestone, but did include atmospheric carbon.

