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 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.
The original radioactive atom is known as a parent isotope, while the atom produced by the decay process is known as a daughter isotope. For example Uranium-235 and Uranium-238 are both Uranium atoms with the same number of protons, but they have a different number of neutrons.
The number used to identify the isotope refers to the total number of particles in the nucleus of each atom.
This is used to date the remains of things that were once living.
All living things absorb Carbon from the atmosphere into their bodies, and excrete Carbon back into the environment.
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However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.
So, we rely on radiometric dating to calculate their ages.
When the isotope is halfway to that point, it has reached its half-life.