Because the time it takes to convert biological materials to fossil fuels is substantially longer than the time it takes for its in the atmosphere, which attained a maximum in 1963 of almost twice what it had been before the testing began.
Measurement of radiocarbon was originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying 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.
In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research.
By measuring the ratio of Carbon-14 in a sample and comparing it to the amount in a recently deceased sample its date can be determined.The age of glaciers, snow fields, and even wines can be estimated by radioisotopic dating. In these cases, the radioactivity level of tritium (an isotope of hydrogen having mass number of 3) Preserve Articles is home of thousands of articles published and preserved by users like you. Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages.For example, two samples taken from the tombs of two Egyptian kings, Zoser and Sneferu, independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus or minus 250 years. Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the ocean, and is taken up by plants via photosynthesis.
Research has been ongoing since the 1960s to determine what the proportion of in the atmosphere has been over the past fifty thousand years.