Relative dating radiometric absolute
Atoms of the same element that have different numbers of neutrons are called isotopes. Most carbon on Earth exists as the very stable isotope carbon-12, with a very small amount as carbon-13.Here’s an example using the simplest atom, hydrogen. Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.
It can be used on objects as old as about 62,000 years.Radiocarbon dating uses isotopes of the element carbon. Cosmic rays – high energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 isotopes.Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.However, because Rb substitutes for K in minerals and these minerals have different K/Ca ratios, the minerals will have had different Rb/Sr ratios.During fractional crystallization, Sr tends to become concentrated in plagioclase, leaving Rb in the liquid phase.
Development of this process was aided by German chemists Otto Hahn and Fritz Strassmann, who later went on to discover nuclear fission in December 1938.