Dna and radio carbon dating


Emilio Segrè asserted in his autobiography that Enrico Fermi suggested the concept to Libby in a seminar at Chicago that year.

Libby estimated that the steady state radioactivity concentration of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram.

For approximate analysis it is assumed that the cosmic ray flux is constant over long periods of time; thus carbon-14 is produced at a constant rate and the proportion of radioactive to non-radioactive carbon is constant: ca. In 1958 Hessel de Vries showed that the concentration of carbon-14 in the atmosphere varies with time and locality.

For the most accurate work, these variations are compensated by means of calibration curves.

The neutrons resulting from the cosmic ray interactions participate in the following nuclear reaction on the atoms of nitrogen molecules (N The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km (30,000 to 50,000 ft), and at high geomagnetic latitudes, but the carbon-14 spreads evenly throughout the atmosphere and reacts with oxygen to form carbon dioxide.

Carbon dioxide also permeates the oceans, dissolving in the water.

After plants die or they are consumed by other organisms (for example, by humans or other animals) the C allows the age of the sample to be estimated.