Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth.
All these methods point to Earth being very, very old -- several billions of years old.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
A nuclide of an element, also called an isotope of an element, is an atom of that element that has a specific number of nucleons.
The rules are the same in all cases; the assumptions are different for each method.
To explain those rules, I'll need to talk about some basic atomic physics. Hydrogen-1's nucleus consists of only a single proton.
Choosing the best method for radiocarbon dating depends on the quantity of available sample or, in the case of expensive materials, how much of it you can afford to be destroyed.
AMS dating, for example, involves burning a sample to convert it to graphite.