For example, how do we know that the Iceman, whose frozen body was chipped out of glacial ice in 1991, is 5,300 years old?
Well, we know this because samples of his bones and hair and even his grass boots and leather belongings were subjected to radiocarbon dating.
Free 5-day trial Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.
So, we start out with two isotopes of uranium that are unstable and radioactive.
They release radiation until they eventually become stable isotopes of lead.
These differing rates of decay help make uranium-lead dating one of the most reliable methods of radiometric dating because they provide two different decay clocks.
This provides a built-in cross-check to more accurately determine the age of the sample.
When the isotope is halfway to that point, it has reached its half-life.