It has been found that the activity of carbon 14 in living materials is about 19 counts per minute per gram of specimen.
Archaeology, which is situated between the hard natural sciences and social sciences, has adapted the techniques developed in these fields to answer both archaeological and anthropological questions that span the globe over both time and space.
Example problems A piece of bone from an archaeological site is found to give a count rate of 15 counts per minute.
A similar sample of fresh bone gives a count rate of 19 counts per minute. The activity A of a sample is proportional to the number of radioactive atoms within it.
One difficulty with this method is that it has to be assumed that the cosmic ray intensity has remained constant, and in fact this has been found not to be the case.
By comparison with the tree rings in the extremely old bristle-cone pines, however, a corrected carbon date can be found for objects over about 1500 years old.