Explain relative dating
These isotopes break down at a constant rate over time through radioactive decay.By measuring the ratio of the amount of the original (parent) isotope to the amount of the (daughter) isotopes that it breaks down into an age can be determined.For example, if an area used for trash has modern refuse in it such as CDs and computers, and the layer underneath has cans made of tin, then it is safe to say the layer of tin cans have a greater relative age than the layer with modern refuse.However, this does not say anything about the absolute age of the layers.
These techniques were first articulated by Nicolas Steno, a Dane living in the Medici court of Italy in the 17th C.
We define the rate of this radioactive decay in half-lives.
If a radioactive isotope is said to have a half-life of 5,000 years that means after 5,000 years exactly half of it will have decayed from the parent isotope into the daughter isotopes.
An example of this type of aging includes rocks in Canada that scientists identified as being hundreds of million years old.
Absolute age is more straight-forward and does not require any other objects for comparison.