Many isotopes have been studied, probing a wide range of time scales.C **and** counting the amount of each) allows one to date the death of the once-living things.Transmutation can occur naturally or by artificial means.

Histories of archaeology often refer to its impact as the "radiocarbon revolution".

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.

Radiocarbon **dating** has allowed key transitions in prehistory to be dated, such as the end of the last ice age, **and** the beginning of the Neolithic **and** Bronze Age in different regions.

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.The best estimate from this **dating** technique says the man lived between 33 BC. From the ratio, the time since the formation of the rock can be calculated.

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