Atmospheric carbon in CO2 has a fixed ratio of C14 to C12.
Once something dies, it ceases taking in new carbon-14, and the existing carbon-14 within the organism decays into nitrogen at a fixed rate.
Scientists measure the proportion of carbon-14 left in the organism to determine its age.
Geologist Ralph Harvey and historian Mott Greene explain the principles of radiometric dating and its application in determining the age of Earth.
As the uranium in rocks decays, it emits subatomic particles and turns into lead at a constant rate.
So, we rely on radiometric dating to calculate their ages.
Radiometric dating, or radioactive dating as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes.
Radiometric dating, or numeric dating, determines an actual or approximate age of an object by studying the rate of decay of radioactive isotopes, such as uranium, potassium, rubidium and carbon-14 within that object. This rate provides scientists with an accurate measurement system to determine age.
For example, carbon dating is used to determine the age of organic materials.
When the carbon is fixed by a plant it is no longer exposed to cosmic radiation. By measuring the amount of beta radiation emitted by the sample, we can tell what percentage of carbon is C14.