more 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.Uranium-238 is a highly radioactive source used to date objects such as rocks.When uranium decays it slowly turns into lead, lead is not radioactive and the presence of lead in the rock would stay constant, we can then use the ratio of lead to uranium to find out how much time has passed since it was formed. the half-life of uranium-238 is about 4500 million years.While the lighter isotopes C has decayed that what remains can no longer be measured. In 5,730 years half of the C in the atmosphere, and therefore in plants and animals, has not always been constant.Radioactive decay can be used as a “clock” because it is unaffected by physical (e.g. For instance, the amount varies according to how many cosmic rays reach Earth.
By measuring the ratio, R, in a sample we can then calculate the age of the sample: T = -8033 ln(R/A) Both of these complications are dealt with by calibration of the radiocarbon dates against material of known age.All animals in the food chain, including carnivores, get their carbon indirectly from plant material, even if it is by eating animals which themselves eat plants.The net effect of this is that all living organisms have the same radiocarbon to stable carbon ratio as the atmosphere.Further complications arise when the carbon in a sample has not taken a straightforward route from the atmosphere to the organism and thence to the measured sample.