This half life is a relatively small number, which means that carbon 14 dating is not particularly helpful for very recent deaths and deaths more than 50,000 years ago.After 5,730 years, the amount of carbon 14 left in the body is half of the original amount.The amount of carbon-14 in the atmosphere has not changed in thousands of years.Even though it decays into nitrogen, new carbon-14 is always being formed when cosmic rays hit atoms high in the atmosphere.The carbon-14 decays with its half-life of 5,700 years, while the amount of carbon-12 remains constant in the sample.By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely. So, if you had a fossil that had 10 percent carbon-14 compared to a living sample, then that fossil would be: t = [ ln (0.10) / (-0.693) ] x 5,700 years t = [ (-2.303) / (-0.693) ] x 5,700 years t = [ 3.323 ] x 5,700 years Because the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old.

This means all living things have radioactive carbon-14 in them.When it decays it forms thorium-234 which is also unstable.Finally, after a series of radioactive isotopes are formed it becomes lead-206, which is stable.The halflife of carbon 14 is 5730 ± 30 years, and the method of dating lies in trying to determine how much carbon 14 (the radioactive isotope of carbon) is present in the artifact and comparing it to levels currently present in the atmosphere.Above is a graph that illustrates the relationship between how much Carbon 14 is left in a sample and how old it is.If half of the uranium-238 has turned into lead-206 the rock will be 4500 million years old.

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