Radiometric dating problem set
The vast majority of carbon atoms, about 98.89%, are C12. And since carbon is an essential element in living organisms, C14 appears in all terrestrial (landbound) living organisms in the same proportions it appears in the atmosphere. Animals and fungi get C14 from the plant or animal tissue they eat for food. The C14 already in the organism doesn't stop decaying, so as time goes on there is less and less C14 left in the organism's remains.
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.
Some isotopes have very long half-lives, measured in billions or even trillions of years.
Others have extremely short half-lives, measured in tenths or hundredths of a second.
When I first got involved in the creationism/evolution controversy, back in early 1995, I looked around for an article or book that explained radiometric dating in a way that nonscientists could understand. Young-Earth creationists -- that is, creationists who believe that Earth is no more than 10,000 years old -- are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error.
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 fourth one is that we know what the concentration of atmospheric C14 was when the organism lived and died.The story of radiocarbon dating shows science at its finest.Radiocarbon dating does not work on anything inorganic, like rocks or fossils.