What is relative and absolute dating

There are over 130 radiocarbon dating laboratories around the world producing radiocarbon assays for the scientific community. A series of movie clips walks you through the process.

The Carbon14 technique has been and continues to be applied and used in many, many different fields including hydrology, atmospheric science, oceanography, geology, palaeoclimatology, archaeology and biomedicine. Isochron methods avoid the problems which can potentially result during radiometric testing.

Information about Simon Winchester's delightful biography of Smith, The Map That Changed the World is available at Tree-Ring dating is based on the principle that the growth rings on certain species of trees reflect variations in seasonal and annual rainfall.

Trees from the same species, growing in the same area or environment will be exposed to the same conditions, and hence their growth rings will match at the point where their lifecycles overlap.

James Hutton and William Smith advanced the concept of geologic time and strengthened the belief in an ancient world.

This is made up of numerous regional tree-ring chronologies, particularly in the medieval and post-medieval periods, for which the laboratory now has more than 200 reference chronologies from many areas. By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined.

A specialized form of cross-dating, using animal and plant fossils, is known as biostratigraphy.

Keyed to the relative time scale are examples of index fossils, the forms of life which existed during limited periods of geologic time and thus are used as guides to the age of the rocks in which they are preserved.

These tests have been performed on what are thought to be the earth's oldest surviving rocks, meteorites, and moon rocks.

These tests have consistently given the same ages for each of these objects.

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