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Atmospheric nuclear weapon tests almost doubled the concentration of concentrations in the neighbourhood of large cities are lower than the atmospheric average.

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.Animals eat the plants, and ultimately the radiocarbon is distributed throughout the biosphere.The ratio of λ is a constant that depends on the particular isotope; for a given isotope it is equal to the reciprocal of the mean-life – i.e.To verify the accuracy of the method, several artefacts that were datable by other techniques were tested; the results of the testing were in reasonable agreement with the true ages of the objects.Over time, however, discrepancies began to appear between the known chronology for the oldest Egyptian dynasties and the radiocarbon dates of Egyptian artefacts. The method was developed by Willard Libby in the late 1940s and soon became a standard tool for archaeologists.

Libby received the Nobel Prize in Chemistry for his work in 1960.

For consistency with these early papers, and to avoid the risk of a double correction for the incorrect half-life, radiocarbon ages are still calculated using the incorrect half-life value.

A correction for the half-life is incorporated into calibration curves, so even though radiocarbon ages are calculated using a half-life value that is known to be incorrect, the final reported calibrated date, in calendar years, is accurate.

thus introduced takes a long time to percolate through the entire volume of the ocean.

The deepest parts of the ocean mix very slowly with the surface waters, and the mixing is uneven.

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.