Radiocarbon dating beta analytic


23-May-2016 04:01

Research has been ongoing since the 1960s to determine what the proportion of 14C in the atmosphere has been over the past fifty-thousand years.The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age.The development of radiocarbon dating has had a profound impact on archaeology.The older a sample is, the less 14C (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by radiocarbon dating are around 50,000 years ago, although special preparation methods occasionally permit dating of older samples.The idea behind radiocarbon dating is straightforward, but years of work were required to develop the technique to the point where accurate dates could be obtained.Other corrections must be made to account for the proportion of 14C throughout the biosphere (reservoir effects).Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.

Fossil fuels contain little detectable 14C atoms in a sample.Samples were converted to solid carbon for the earliest devices, but it was quickly discovered that converting them to gas or liquid form gave more accurate results.More recently, accelerator mass spectrometry has become the method of choice; it counts all the 14C atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly.Dates are often reported in years "before present", or BP; this actually refers to a baseline of 1950 AD, so that a date of 500 BP means 1450 AD.

The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen.The resulting radiocarbon combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire 14C in a sample from a dead plant or animal such as piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died.



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