Varve dating method
Because of this relatively short half-life, radiocarbon is useful for dating items of a relatively recent vintage, as far back as roughly 50,000 years before the present epoch.Radiocarbon dating cannot be used for older specimens, because so little carbon-14 remains in samples that it cannot be reliably measured.
Radiocarbon dating, which is also known as carbon-14 dating, is one widely used radiometric dating scheme to determine dates of ancient artifacts.
In discussions of the age of the earth and the antiquity of the human race, creationists often assail perceived weaknesses in radiocarbon dating. Morris, for instance, wrote, "Despite its high popularity, [radiocarbon dating] involves a number of doubtful assumptions, some of which are sufficiently serious to make its results for all ages exceeding about 2000 or 3000 years, in serious need of revision." [Morris2000, pg. Radiocarbon dating is based on the fact that the interaction of cosmic rays from outer space with nitrogen atoms in the atmosphere produces an unstable isotope of carbon, namely radiocarbon.
Since it is chemically indistinguishable from the stable isotopes of carbon (carbon-12 and carbon-13), radiocarbon is taken by plants during photosynthesis and then ingested by animals regularly throughout their lifetimes.
When a plant or animal organism dies, however, the exchange of radiocarbon from the atmosphere and the biosphere stops, and the amount of radiocarbon gradually decreases, with a half-life of approximately 5730 years.
Thus creationists and others who invoke perceived weaknesses in radiocarbon dating as justification to cast doubt on the great age of the earth are either uniformed on very basic scientific facts, or else are highly being disingenuous to their audience.
Radiocarbon dating has been studied at great length over the past few decades, and its strengths and weaknesses are very well understood at this point in time.
For instance, even in the 1950s, when Willard Libby first developed the process, it was recognized that the scheme assumes that the level of carbon-14 in the atmosphere is constant.
But researchers have known at least since 1969 that the carbon-14 level has not been constant, so that the radiocarbon clock needs to be "calibrated." As a result, various schemes are used to correct and calibrate radiocarbon dates, including: In each case, radiocarbon dates, determined by well-established procedures and calculations, are compared directly with dates determined by the above methods, thus permitting the radiocarbon dates to be accurately calibrated with distinct and independent dating techniques.
In 2009, several leading researchers in the field established a detailed calibration of radiocarbon dating, based on a careful analysis of pristine corals, ranging back to approximately 50,000 years before the present epoch [Reimer2009].