Beyond the specific topic of natural 14 C, it is hoped that this account may serve as a metaphor for young scientists, illustrating that just when a scientific discipline may appear to be approaching maturity, unanticipated metrological advances in their own chosen fields, and unanticipated anthropogenic or natural chemical events in the environment, can spawn new areas of research having exciting theoretical and practical implications.
This article is about metrology, the science of measurement.
More specifically, it examines the metrological revolutions, or at least evolutionary milestones that have marked the history of radiocarbon dating, since its inception some 50 years ago, to the present. The series of largely or even totally unanticipated developments in the metrology of natural 14 C is detailed in the several sections of this article, together with examples of the consequent emergence of new and fundamental applications in a broad range of disciplines in the physical, social, and biological sciences.
Following the discovery of this year half-life radionuclide in laboratory experiments by Ruben Kamen, it became clear to W. Libby that 14 C should exist in nature, and that it could serve as a quantitative means for dating artifacts and events marking the history of civilization. The search for natural radiocarbon was itself a metrological challenge, for the level in the living biosphere [ca.
That was but the beginning, however. Subsequent metrological and scientific advances have included: The year before last marked the 50th anniversary of the first edition of Willard F. Eight years later Libby was awarded the Nobel Prize in Chemistry.
In a very special sense that small volume pages of text captured the essence of the path to discovery: Libby, about the time of publication of the first edition of his monograph, Radiocarbon Datingand statement of the Nobel Committee [ 3 ]. Like many of the major advances in science, Radiocarbon Dating was born of Scientific Curiosity. Through intensive study of the The invention of carbon dating ray and nuclear physics literature, Libby made an important series of deductions, leading to a quantitative prediction of the natural 14 C concentration in the living biosphere.
Based on the observed production rate of neutrons from cosmic rays ca. A graphical summary of the above points is given in Fig. Graphical representation of the production, distribution, and decay of natural 14 C courtesy of D.
Parameter values are approximate. Libby first postulated the existence of natural 14 C inat a level of 0. The plan was to search for natural 14 C in bio-methane, but the background of his well-shielded 1. Libby and coworkers did succeed in demonstrating the presence of 14 C in living matter, however. Having detected 14 C in the living biosphere, Libby and his colleagues had to develop a measurement technique that was both quantitative and practical.
The thermal diffusion enrichment technique [ 6 ] was not: Development of an acceptable technique was formidable, as outlined in Table 1. At this point, Libby "The invention of carbon dating" an inspiration, from the analysis of the nature of the background radiation [ 4 ].
The final background to signal ratio of 0. The 14 C screen wall counter is visible through the open, 8 inch thick cantilevered steel doors having a wedge-like closure.
Low-level anticoincidence counting apparatus devised by Libby for the original 14 C measurements that led to the The invention of carbon dating of the radiocarbon dating technique Ref.
California Press, Berkeley Once the measurement of natural 14 C became feasible, the immediate task tackled by Libby and his colleagues was to test the validity of the radiocarbon dating model. The first step consisted of determining the zero point of the natural radiocarbon decay curve— i. This was a major component of the PhD thesis of E. Anderson [ 7 ]; the result R o was The absolute age derives from the inversion of first order The invention of carbon dating decay relation, using Although the relative measurement uncertainties are moderately large ca.
Note that the curve shown is not fit to the data! Rather, it represents the absolute, two-parameter nuclear decay function.
See [ 8 ] for detailed information on the validation samples selected. Radiocarbon dating validation curve The exponential function is not fit to the databut derived from the independently measured half-life and the 14 C content of living matter [ 2 ], Fig.
This The invention of carbon dating absolute dating function served to establish the method, but it indicated the need for a universal radiocarbon dating standard, since the reference value for the intercept here The problem was tackled by the international radiocarbon community in the late s, in cooperation with the U.
National Bureau of Standards.
Its 14 C concentration was ca. It was prepared from oxalic acid derived from the fermentation of French beet molasses from harvests of A copy of the Certificate Analysis of SRM C, together with pertinent references, may be obtained from the website: Already, by the time the Nobel Prize was awarded, Radiocarbon Dating appeared to be approaching maturity, with a rich future in application as opposed to new fundamental discovery.