The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant.Maybe one in a trillion carbon atoms are carbon-14.
However, atmospheric testing of nuclear weapons in the late 1950's and early 1960's greatly increased the amount of radiocarbon in the atmosphere, so the decay rate of 14 decays per minute more than doubled. The ratios are consistent among species, and the slight (1-3%) differences can also be calculated from the ratio of C) decreases as the radiocarbon decays. Libby determined, one gram of pure carbon should produce about 14 (13.56) radioactive decays per minute. The Beta-counting method detects the rate at which purified carbon decays. A rate of 7 decays/gram/minute would indicate an age of one half-life, or 5730 years old. View the full list Radiocarbon dating has transformed our understanding of the past 50,000 years.Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts.Carbon-14 is radioactive, with a half-life of about 5,700 years.