Radiometric dating means

Libby later received the Nobel Prize in Chemistry in 1960: (From Taylor, 1987).Today, there are over 130 radiocarbon dating laboratories around the world producing radiocarbon assays for the scientific community.These isotopes are present in the following amounts C12 - 98.89%, C13 - 1.11% and C14 - 0.00000000010%.Thus, one carbon 14 atom exists in nature for every 1,000,000,000,000 C12 atoms in living material.As 14C decays it emits a weak beta particle (b ), or electron, which possesses an average energy of 160ke V.The decay can be shown: Thus, the 14C decays back to 14N.The 14C formed is rapidly oxidised to 14CO2 and enters the earth's plant and animal lifeways through photosynthesis and the food chain.

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As soon as a plant or animal dies, they cease the metabolic function of carbon uptake; there is no replenishment of radioactive carbon, only decay.

There is a useful diagrammatic representation of this process given here Libby, Anderson and Arnold (1949) were the first to measure the rate of this decay.

They found that after 5568 years, half the C14 in the original sample will have decayed and after another 5568 years, half of that remaining material will have decayed, and so on (see figure 1 below).

The C14 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.

There are three principal isotopes of carbon which occur naturally - C12, C13 (both stable) and C14 (unstable or radioactive).

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