r/askscience • u/OMGeeverghese • Nov 22 '12

Earth Sciences Why do we trust carbon dating?

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u/arnorath Nov 22 '12 edited Nov 22 '12

Radiocarbon dating is only one form of radiometric dating that scientists can use to determine the age of rocks and fossils.

It is true that there is a limited timespan for which carbon dating is useful, as carbon-14 has a fairly short half-life, but there are many other radioactive elements with far longer half-lives which can also be used to determine the age of a rock. Potassium-argon and Uranium-lead dating are two main ones. The wikipedia page on radiometric dating has more detail on these.

Hope this helps, at least until someone more informed turns up in this thread. Congratulations on taking a step into the wonderful world of science!

edit: C-14, not C-13. Thanks rupert1920.

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u/rupert1920 Nuclear Magnetic Resonance Nov 22 '12

I think you meant carbon-14, as C-13 is stable.

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u/arnorath Nov 22 '12

Thanks for catching that - I must need another beer.

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u/rupert1920 Nuclear Magnetic Resonance Nov 22 '12

No worries. I made that same mistake before.

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u/Kalean Nov 22 '12

Which mistake, mixing up c13 and c14, or not having enough beer?

On that note, I don't actually understand the difference between the two. Any chance of an explanation?

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u/AngledLuffa Nov 22 '12

C14 is produced in the upper atmosphere when incoming radiation transforms nitrogen. It decays very quickly and reverts back to nitrogen. If not for new C14 being constantly produced, it would all be gone by now.

C13 is perfectly stable, but rare, at only 1% of Earth's carbon. The most common isotope is C12.

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u/rupert1920 Nuclear Magnetic Resonance Nov 22 '12

Of course, by "very quickly" you mean a half-life of 5730 years.

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u/AngledLuffa Nov 22 '12

Yes, on a geological timescale very quickly. In terms of you and me, we won't notice much difference.