History of radiometric dating
Some isotopes can break down in more than one way -- in these cases, each different breakdown type has its own half-life.The decay rate and therefore the half-life are fixed characteristics of an isotope. That's the first axiom of radiometric dating techniques: the half-life of a given isotope is a constant.The second assumption is that the organism in question got its carbon from the atmosphere.
If we measure how much C14 there currently is, we can tell how much there was when the organism died, and therefore how much has decayed.
Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth.
When I first became interested in the creation-evolution debate, in late 1994, I looked around for sources that clearly and simply explained what radiometric dating is and why young-Earth creationists are driven to discredit it.
Contents: The half-life of a radioactive isotope is defined as the time it takes half of a sample of the element to decay.
A mathematical formula can be used to calculate the half-life from the number of breakdowns per second in a sample of the isotope.