1. Absolute dating methods are those that produce dates without reference to other indexes or chronologies. Two such absolute methods important to the study of human culture are radiocarbon dating and thermoluminescent dating. Relative methods are those such as dendrochronology which rely on other indexes or on a succession of dating events. Dendrochronology, for example, is the calculation of dates based on the growth rings in trees. But since there is no single super-tree that provides an absolute index the accumulation of successive dates (calibrated in accordance with literary evidence and general weather trends observed in other samples) produces a relative date for timbers used in Western Europe and the American Southwest up to 4,500 BC. Absolute dating methods often produce calendar dates by means of coordination with relative methods such as dendrochronology.
Radiocarbon dating is based on the fact that C14 atoms are absorbed by living organisms and decay at a particular atomic rate from the moment of the death of the organism. Radiocarbon dating (which is constantly being refined on the basis of new information about the amount of C14 in the atmosphere and the atomic rate of decay for the particle) provides dates up to 40,000 years ago. The radiocarbon method is, however, far less accurate for objects from the last 2,000 years--and its dating is "absolute" only to the point of assigning dates within a century or so.
Thermoluminescent dating similarly determines the age of ceramic materials fired anywhere between 100,000 years ago and the present. But ceramic dating is based on the addition of radioactive particles to the object after it has been fired. Ceramic materials absorb radiation in the form of identifiable particles and the level of radiation in them can be determined by heating them to certain temperatures. Because the accumulation of radioactive particles can be affected by numerous factors this me...