If you have a fossil, you can tell how old it is by the carbon 14 dating method.This is a formula which helps you to date a fossil by its carbon.They synthesized Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, and after isotopically enriching their samples they were able to demonstrate that they contained radioactive .By contrast, methane created from petroleum showed no radiocarbon activity because of its age.In addition to permitting more accurate dating within archaeological sites than previous methods, it allows comparison of dates of events across great distances.Histories of archaeology often refer to its impact as the "radiocarbon revolution".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.When a date is quoted, the reader should be aware that if it is an uncalibrated date (a term used for dates given in radiocarbon years) it may differ substantially from the best estimate of the actual calendar date, both because it uses the wrong value for the half-life of and each component is also referred to individually as a carbon exchange reservoir.

Other corrections must be made to account for the proportion of throughout the biosphere (reservoir effects).

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.

the average or expected time a given atom will survive before undergoing radioactive decay. The calculations involve several steps and include an intermediate value called the "radiocarbon age", which is the age in "radiocarbon years" of the sample: an age quoted in radiocarbon years means that no calibration curve has been used − the calculations for radiocarbon years assume that the , which for more than a decade after Libby's initial work was thought to be 5,568 years.

The results were summarized in a paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin.

Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages.

This was revised in the early 1960s to 5,730 years, which meant that many calculated dates in papers published prior to this were incorrect (the error in the half-life is about 3%).

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