Changes

First, it had not been proven scientifically whether the rate of decay of <SUP>14</SUP>C has remained constant over hundreds or thousands of years: nor has it been proven that it has ''not'' remained constant. (Notably, the decay of other isotopes that have half-lives over the course of days to microseconds all follow the characteristic first-order kinetics; hundereds of isotopes follow this pattern, and their properties extenstively have been studied.) Some scientists have suggested, based on experimental observations, that the laws of physics do change over time.<ref>"The idea that nature's laws change over time was proposed in the 1930s by one of the titans in the history of physics, Paul Dirac of England. According to Dirac's large numbers hypothesis, the force of gravity changed over time." See Keay Davidson, "Recent study forces scientists to rethink basic law of physics," San Francisco ''Chronicle''[http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2005/05/09/MNG5LCLEU41.DTL]</ref> The "change" discussed here - in a study that is still very controversial - occurred over billions of years, though, and not in the near enough future to have had an effect on the utility of carbon dating (since carbon dating is only useful to date life within the past 50,000 years, only a change within 50,000 years would affect the dating method).