Radiocarbon dating works by precisely measuring the ratio of radiocarbon to stable carbon in a sample. The tree-ring chronologies have been constructed by counting the annual rings in living trees and matching patterns in these rings to older wood and dead trees.
By cross-matching tree-ring sequences in individual specimens a long, continuous tree-ring chronology is constructed with very little dating uncertainty. for more information on tree-ring chronologies.) By measuring radiocarbon concentrations in these tree-rings of known age a calibration table is constructed giving the true date of a sample versus its raw radiocarbon date.
The foregoing article was primarily based on a discussion of radiocarbon dating found in The Biblical Chronologist Volume 5, Number 1.
Plants obtain all their carbon atoms from the atmosphere.
Thus the ratio of radiocarbon to stable carbon in living animal tissue is also virtually the same as the ratio of radiocarbon to stable carbon in the atmosphere at any given time.
This ratio is the same for all organisms across the globe at a given time due to the mixing of the atmosphere mentioned above.
When an organism dies (whether plant or animal) its intake of carbon atoms ceases.
The starting ratio of radiocarbon to stable carbon is locked in at that point. The purpose in each of these methods is to determine the ratio of radiocarbon to stable carbon in the sample.
The raw radiocarbon date of any sample can then be converted to true date by using this calibration table.