Radiocarbon dating principles

How is C14 used for dating the past?

¹⁴C (or Radiocarbon) is the radioactive isotope of the common element carbon. It is generally formed in the upper atmosphere by the interaction of cosmic rays with nitrogen gas (N₂). The radiocarbon is oxidised to carbon dioxide (or CO₂) and is instantantly mixed throughout the atmosphere. As carbon dioxide is used as the basis for photosynthesis, the radiocarbon is integrated into all living things. As far as plant or animal dies, the radiocarbon decays.

It is known that half-life of radiocarbon is 5730 years. At radiocarbon dating laboratory could be measured the amount of remaining radiocarbon relative to the stable one which don’t change in concentration. Back-calculation to the time of death could be done using the known radiocarbon half-life.

Radiocarbon content in the earth atmosphere is varying in time due to past changes in the strength of the earth’s magnetic field, the strength of the sun and changes in the carbon cycle. It cause that the one radiocarbon year does not equal one calendar year. Therefore radiocarbon age should be converted to calendar age using one of several available software packages CALIB 4, OxCal, CalPal.