As the rock gets older the proportion of lead increases.
If half of the uranium-238 has turned into lead-206 the rock will be 4500 million years old.
However, the principle of carbon-14 dating applies to other isotopes as well.
Potassium-40 is another radioactive element naturally found in your body and has a half-life of 1.3 billion years.
The age of the rock can be calculated if the ratio of uranium to lead is known.After 5,730 years, the amount of carbon 14 left in the body is half of the original amount.If the amount of carbon 14 is halved every 5,730 years, it will not take very long to reach an amount that is too small to analyze.So, the fossil is 8,680 years old, meaning the living organism died 8,680 years ago.The amount of carbon-14 in the atmosphere has not changed in thousands of years.In the case of radiocarbon dating, the half-life of carbon 14 is 5,730 years.