Carbon 14 dating

By comparing the rations of two isotopes of carbon, carbon-12 and carbon-14 you can tell the age of once-living material. It works only for samples up to 50,000 years old, a mere eyeblink of evolutionary time. It works because living material absorbs carbon-14, which then deteriorates slowly to carbon-12 after death. There are other kinds of radiometric dating useful for dating rocks even billions of years old.

~ Roedy (1948-02-04 age:69) carbon 14 dating click to watch