In this method, the carbon 14 content is directly measured relative to the carbon 12 and carbon 13 present.The method does not count beta particles but the number of carbon atoms present in the sample and the proportion of the isotopes.No other scientific method has managed to revolutionize man’s understanding not only of his present but also of events that already happened thousands of years ago.Archaeology and other human sciences use radiocarbon dating to prove or disprove theories.
There are three principal techniques used to measure carbon 14 content of any given sample— gas proportional counting, liquid scintillation counting, and accelerator mass spectrometry.
By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known. Some inorganic matter, like a shell’s aragonite component, can also be dated as long as the mineral’s formation involved assimilation of carbon 14 in equilibrium with the atmosphere.
It must be noted though that radiocarbon dating results indicate when the organism was alive but not when a material from that organism was used. Samples that have been radiocarbon dated since the inception of the method include charcoal, wood, twigs, seeds, bones, shells, leather, peat, lake mud, soil, hair, pottery, pollen, wall paintings, corals, blood residues, fabrics, paper or parchment, resins, and water, among others.
The radiocarbon age of a certain sample of unknown age can be determined by measuring its carbon 14 content and comparing the result to the carbon 14 activity in modern and background samples.
The principal modern standard used by radiocarbon dating labs was the Oxalic Acid I obtained from the National Institute of Standards and Technology in Maryland. Around 95% of the radiocarbon activity of Oxalic Acid I is equal to the measured radiocarbon activity of the absolute radiocarbon standard—a wood in 1890 unaffected by fossil fuel effects.