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# KCC's Quizzes AQQ245 on Fossil Dating with Carbon14

You probably heard the method of dating fossils by measuring Carbon14 (also note C14 concentration. To refresh, the concentration of C14 in the air and on earth surface is constant (thanks to cosmic radiation) since ever (in fact it is assumed so). C14 is not stable and is changed into Nitrogen and an electron: C14 concentration versus the standard carbon (C12) decades with time. That speed is characterized by Its half-life period which is 5568 years for C14 (quantity of C14 still present in an isolated place decays by half after each 5568 years).

Today, in free air and on the earth surface, the ratio N0 = C14/C12 is 0.8 10-12

A mammoth bone has been just extracted and the concentration of C14/C12 is 0.2 10-12.

Questions:

1. How old is that bone?

2. Since humanity is constantly putting more carbon in the atmosphere. How it affects the Carbon14 dating? For example, if C12 concentration is doubled. How will be the dating of our previous bone?

Good Luck!

P.S. If you think there are colleagues who should try those quizzes, please forward them the link!

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[edited by: StephenV at 3:24 PM (GMT -4) on 18 Oct 2023]
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• 3113 yrs old, ratio in old bone would remain the same if c12 doubled and the baseline is known so no problem there but future dating of artefacts from today would need a new baseline if the c14/c12 constant shifts due to more c12 in future years.

• Thanks Simon for your reply! But 3113 years is quite low.... If the half life period is already 5568 years, it means, the concentration of C14 is decreased by 2 after 5568 years and by 4 after 2 x 5568 years = 11136 years. And here, we are well facing to that latter situation: concentration of C14 has been decreased from 0.8 to 0.2 10^-12.

• Thanks Simon for your reply! But 3113 years is quite low.... If the half life period is already 5568 years, it means, the concentration of C14 is decreased by 2 after 5568 years and by 4 after 2 x 5568 years = 11136 years. And here, we are well facing to that latter situation: concentration of C14 has been decreased from 0.8 to 0.2 10^-12.

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