How long can carbon be detected after death?

Question

I have seen many science specials on telling how old human bones are found after many thousands of years. In these specials they say they are judging the carbon. I think I heard 10,000 years is the max....I could be wrong.

Answer 1

There are two forms of Carbon. C12 is the regular stuff and Carbon 14 is radioactive carbon that is formed in the atmosphere when the regular carbon is altered by radiation from space. The Carbon 14 in the air gets into everything that grows, especially plants. Over a long period of time the C14 radiates and changes back into C12. So, if you have some thing that was alive a long time ago you can check what per cent C14 it has in it and that gives you a measure of how old it is. Radiocarbon dating is pretty accurate for things like pieces of wood or animal remains that are up to 20,000 years old or so. It is less accurate for things back to about 50,0000 years ago because the amopunt of C14 in the objects has decayed down to really small amounts that are hard to measure, and contamination becomes more of a problem. Also, in some materials, like coal, the Carbon in the coal can receive radiation from surrounding rocks and then the amount of new C14 from that source will be enough to mess up the calculations - the coal could falsely appear to be only a few 10,000s of years old, even though other geologic evidence shows that it is millions of years old.

Answer 2

Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 to determine the age of carbonaceous materials up to about 60,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" (BP), "Present" being defined as AD 1950. Such raw ages can be calibrated to give calendar dates.