# Carbon dating and half life calculations

The Half Life is independent of the physical state (solid, liquid, gas) temperature, pressure, the chemical compound in which the nucleus finds itself, and essentially any other outside influence.

If a fossil contains 60% of its original carbon, how old is the fossil? That means this is how long it takes for half the nuclei to decay.

It uses the naturally occurring radioisotope carbon-14 (14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years old.

Carbon has two stable, nonradioactive isotopes: carbon-12 (12C) and carbon-13 (13C).

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.

Archaeologists use the exponential, radioactive decay of carbon 14 to estimate the death dates of organic material.