Answer:
In a process called radiometric dating, scientists measure the fix decay rate of an isotope to determine the age of the earth.
Step-by-step explanation:
In the process of radiometric dating we can find the age of fossils, how long the rocks formed and fossils contains within those rocks. Radiometric is very accurate to date the earth, and radioactive decay of unstable isotopes like uranium, carbon and potassium that are slow to decay.
Scientist measures the fixed decay rate during the radioactive decay, it happens when an unstable atomic nucleus continuous changes to lower energy state and splits the radiation.