The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value.Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson. As we age, our hair turns gray, our skin wrinkles and our gait slows.However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.Later called Ötzi the Iceman, small samples from his body were carbon dated by scientists.
The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay.
The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out.
Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.
This provides a built-in cross-check to more accurately determine the age of the sample.
Uranium is not the only isotope that can be used to date rocks; we do see additional methods of radiometric dating based on the decay of different isotopes.