Cambridge carbon dating
The NERC Radiocarbon Facility (East Kilbride) is a central facility for the UK's Natural Environment Research Council (NERC), providing dating support in the environmental sciences.
The laboratory has an "open-door" policy for all existing and potential users of its facilities at all stages of their research projects, and collaboration is strongly encouraged.
It is also worth noting that the half-life used in carbon dating calculations is 5568 years, the value worked out by chemist Willard Libby, and not the more accurate value of 5730 years, which is known as the Cambridge half-life.
Although it is less accurate, the Libby half-life was retained to avoid inconsistencies or errors when comparing carbon-14 test results that were produced before and after the Cambridge half-life was derived.
This tree-ring sequence, established by Wesley Ferguson in the 1960s, aided Hans Suess to publish the first useful calibration curve.
Libraries of tree rings of different calendar ages are now available to provide records extending back over the last 11,000 years.
The trees often used as references are the bristlecone pine (Pinus aristata) found in the USA and waterlogged Oak (Quercus sp.) in Ireland and Germany.
Tree rings provided truly known-age material needed to check the accuracy of the carbon-14 dating method.
During the late 1950s, several scientists (notably the Dutchman Hessel de Vries) were able to confirm the discrepancy between radiocarbon ages and calendar ages through results gathered from carbon dating rings of trees.