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xkcd #3205: Carbon Dating
(imgs.xkcd.com)
Title text:
This dating is corroborated by the presence of stone tools at the site, rather than earlier and less effective helium ones.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3205/
a cosmologist wouldn't even know what carbon is. it's just some kind of metal.