Carbon Dating: The Technique
Carbon Dating is a controversial dating technique. The method is based on the rate of decay of the radioactive carbon isotope, Carbon-14, which is formed in the upper atmosphere through the effect of cosmic ray neutrons upon Nitrogen-14. The Carbon-14 is rapidly oxidized and enters the earth's organic life through photosynthesis (plants) and the food chain (animals). Carbon-14 also enters the earth's oceans in an atmospheric exchange and as dissolved carbonate. Plants and animals, which utilize carbon in organic functions and food chains, absorb Carbon-14 during their lifetimes. The assumption is that the earth-bound carbon exists in equilibrium with the Carbon-14 in the atmosphere, which means that the number of Carbon-14 atoms and non-radioactive carbon atoms stays approximately the same over time. As soon as a plant or animal dies, it ceases its carbon intake. Thereafter, there is no replenishment of
radioactive Carbon-14, only decay. In 1949, a team of scientists led by Willard Libby of the University of Chicago discovered that this decay occurs at a constant rate. They found that after 5,568 years, half the Carbon-14 in a dead sample will decay, and after another 5,568 years, half of that remaining Carbon-14 will decay, and so on. Thus, the "half-life" for Carbon-14 was measured by Libby and his team at 5,568?0 years. After ten half-lives, there is a miniscule amount of radioactive carbon left in a sample, which means that the limit of the Carbon Dating method is reached at between 50,000 and 60,000 years.
Carbon Dating: The Controversy
Carbon dating is controversial in that it shares some of the fundamental assumptions inherent to all Radiometric Dating techniques. In order for Carbon Dating to have any value, Carbon-14, produced in our outer atmosphere as Nitrogen-14 and changed into radioactive Carbon-14 by cosmic-ray bombardment, must be at equilibrium in our atmosphere. That is, the production rate must be equal to the decay rate. Based on the mathematics inherent in Libby's research, it takes approximately 30,000 years of Carbon-14 build up from a zero concentration level to reach this state of equilibrium. Recent studies indicate that Carbon-14 has not yet reached equilibrium in our atmosphere, thus indicating that the atmosphere is not yet 30,000 years old.
Carbon Dating: The Use Of Dendrochronology
Carbon Dating advocates have turned to Dendrochronology (tree ring dating) to help solve the "equilibrium" dilemma. They claim that Dendrochronology allows them to determine past concentration levels of Carbon-14 in the atmosphere, by measuring the Carbon-14 to Carbon-12 ratios in tree rings. The problem is that no trees have been shown to exceed 4,500 years in age. The Methuselah Tree in Southern California has been called the oldest living tree, and it has been dated at approximately 4,500 years. Carbon Dating advocates use tree rings from dead trees thought to overlap the Methuselah Tree to mathematically determine ages exceeding 4,500 years. They determine whether a dead tree's age overlaps the Methuselah Tree's age by ring patterns, and then they assume that the dead trees are older through a comparison of ring patterns, carbon ratios, etc. There seems to be an illogical methodology here. To
complicate matters, tree ring patterns are typically inconsistent. Even living trees can show dissimilar patterns caused by differing soil nutrients, direction of prevailing sunlight, fire history, distance to water sources, etc.
Carbon Dating: What Do The Experts Think?
Carbon Dating can best be summed-up with the following statement by T. Save-Sodebergh and I.U. Olsson (Institute of Egyptology and Institute of Physics, respectively, University of Uppsala, Sweden) in their publication, C-14 Dating and Egyptian Chronology in Radiocarbon: "If a C-14 date supports our theories, we put it in the main text. If it does not entirely contradict them, we put it in a footnote. And if it is completely 'out of date' we just drop it." This illustrates the fact that accepted carbon dates are not necessarily accurate dates -- they are merely selected dates. "It should be no surprise, then, that fully half of the dates are rejected. The wonder is, surely, that the remaining half come to be accepted" (Robert E. Lee, "Radiocarbon, Ages in Error," Anthropological Journal of Canada, Vol. 19, No.3, 1981, pp.9, 29).
Republished by permission from http://www.carbon-dating.net/