Seriation is the ordering of objects according to their age.James Ford - used seriation to determine the chronological order of American Indian pottery styles in the Mississippi Valley.
For instance, if an object has 50 percent of its decay product, it has been through one half-life.
A popular way to determine the ages of biological substances no more than 50,000 years old is to measure the decay of carbon-14 into nitrogen-14.
The key is to measure an isotope that has had time to decay a measurable amount, but not so much as to only leave a trace remaining.
Given isotopes are useful for dating over a range from a fraction of their half life to about four or five times their half life.
Although the time at which any individual atom will decay cannot be forecast, the time in which any given percentage of a sample will decay can be calculated to varying degrees of accuracy.
The time that it takes for half of a sample to decay is known as the half life of the isotope.
Radioactive dating uses the decay rates of radioactive substances to measure absolute ages of rocks, minerals and carbon-based substances, according to How Stuff Works.
Scientists know how quickly radioactive isotopes decay into other elements over thousands, millions and even billions of years.
This is consistent with the assumption that each decay event is independent and its chance does not vary over time.