Carbon dating level chemistry
At the time, no radiation-detecting instrument (such as a Geiger counter) was sensitive enough to detect the small amount of carbon-14 that Libby’s experiments required.Libby reached out to Aristid von Grosse (1905–1985) of the Houdry Process Corporation who was able to provide a methane sample that had been enriched in carbon-14 and which could be detected by existing tools.Top of page You read statements in books that such and such a society or archeological site is 20,000 years old.We learned rather abruptly that these numbers, these ancient ages, are not known accurately; in fact, it is at about the time of the First Dynasty in Egypt that the first historical date of any real certainty has been established.” —Willard Libby, Nobel Lecture, 12 December 1960 The concept of radiocarbon dating focused on measuring the carbon content of discreet organic objects, but in order to prove the idea Libby would have to understand the earth’s carbon system.It showed all of Libby’s results lying within a narrow statistical range of the known ages, thus proving the success of radiocarbon dating.
For organic objects of intermediate ages—between a few centuries and several millennia—an age could be estimated by measuring the amount of carbon-14 present in the sample and comparing this against the known half-life of carbon-14.Libby and graduate student Ernest Anderson (1920–2013) calculated the mixing of carbon across these different reservoirs, particularly in the oceans, which constitute the largest reservoir.Their results predicted the distribution of carbon-14 across features of the carbon cycle and gave Libby encouragement that radiocarbon dating would be successful.He reasoned that a state of equilibrium must exist wherein the rate of carbon-14 production was equal to its rate of decay, dating back millennia.(Fortunately for him, this was later proven to be generally true.) For the second factor, it would be necessary to estimate the overall amount carbon-14 and compare this against all other isotopes of carbon.
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To test the technique, Libby’s group applied the anti-coincidence counter to samples whose ages were already known.