how does radiocarbon analysis work?...when trying to figure the age of something?

Answer 1

Carbon has a radioactive form called Carbon 14 which is generated by solar particles. This exists at a pretty constant ratio between C12 and C14. Plants and then animals absorb the C14 and while they are living the C12/C14 ratio remains the same.

However when the plant dies the C14 decays due to radioactivity. So you can measure the date that the object died from the C14 ratio up to a few thousand years after which there is not enough C14 left.

Answer 2

To add onto the previous answerer. If you take a sample of dead organic matter that you believe to be less than about 25,000 years old, and burn off all the other compounds to extract only the carbon, then weigh the carbon (which consists of C-12 and what's left of the C-14), you can get a ratio of C-14 to C-12 (a very small ratio -- smaller as time goes by). Since the ratio of C-12 to C-14 was known at the time of death (based on the ratio we know today, and still a fair assumption 'back then'), and knowing the rate of decay of C-14 of 5730 years, one can fairly accurately find the age of the dead organic material.

Example: if 1/8th of the original C-14 is left, then the age would be 3 * 5730 = 17190 years old. 3 is used because of 3 half lives: 1/2 of the original, 1/2 of that (1/4), and1/2 of that (1/8)

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