I am skeptical because I do not understand carbon dating. So if I’m getting this right:
>most of the time carbon isn’t radioactive
>carbon-14 reaches the upper atmosphere via cosmic rays, and is then absorbed by plants
>about $10^{-10}$ percent of carbon on earth is carbon-14
>animals eat plants which contain carbon-14
>we can use this and our knowledge of the half-life of carbon-14 to infer the age of an animal
What confuses me is a few thing.
1) How do we know the initial concentration of carbon-14 in a sample? Isn’t the only measurement we can take of the current concentration?
2)How do we know the half-life of carbon-14? Surely we couldn’t watch a sample for 5,000 something years to realize that about half of the atoms decayed, so how was the half-life inferred?

Sure I could just google it, but this is a science and math board and it’s more fun this way.