Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.

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To determine the ages of these specimens, scientists need an isotope with a very long half-life.

Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.

In short, Genesis was an allegory and not literal history.

The story of this great change in the conception of the history of Earth is not a simple one.

The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age.

Other corrections must be made to account for the proportion of throughout the biosphere (reservoir effects).

The chronicle of this great change can be broken into five periods; ran from AD 1600-1700.

In this period a number of comprehensive cosmogonies were proposed.

Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.

But this sediment doesn't typically include the necessary isotopes in measurable amounts.

The period of time that it takes for half of a sample to decay is called a "half-life." Radiocarbon oxidizes (that is, it combines with oxygen) and enters the biosphere through natural processes like breathing and eating.