Archaeological dating important
It is used for human and animal bone and other organic material.
Specific changes in its amino acid structure (racemization or epimerization) which occur at a slow, relatively uniform rate, are measured after the organism's death.
It can be used for the dating organic material up to 75,000 years old. Libby (1947); his radioactive-carbon dating provided an extremely valuable tool for archaeologists, anthropologists, and earth scientists.
When organic matter dies it ceases to exchange its carbon, as carbon dioxide, with the atmosphere, so its C14 dwindles by decay and is not replenished.
Other problems of contamination have occurred, so the technique is not fully established.
It is fairly reliable for deep-sea sediments as the temperature is generally more stable.. Libby showed the essential uniformity of carbon-14 in living material and went on to measure the radiocarbon level in organic samples dated historically -- materials as old as 5,000 years from sources such as Egyptian tombs.
The reasons for the fluctuation are not yet fully understood.
The specimen is bombarded with neutrons which interact with nuclei in the sample to form radioactive isotopes that emit gamma rays as they decay.Determination of the radioactivity of carbon from a sample will reveal the proportion of C14 to C12, and this will in turn, through the known rate of decay of C14, give the age of, or more accurately the time elapsed since the death of, the sample.