Radioactive isotopes used in dating fossils
Later called Ötzi the Iceman, small samples from his body were carbon dated by scientists.The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out. Results from different techniques, often measured in rival labs, continually confirm each other.Every few years, new geologic time scales are published, providing the latest dates for major time lines.Carbon-14 has a half-life of 5,730 ± 40 years—, half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years.Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon.Current understanding of the history of life is probably close to the truth because it is based on repeated and careful testing and consideration of data.
The carbon-14 it contained at the time of death decays over a long period of time.
If the relatiom betwen normal carbon, also known as carbon - 12 (12 = mass) and carbon - 14 are pretty same, altough there are little more isotopes, the organism or organic material didnt die a long time ago.
There's a small amount of radioactive carbon-14 in all living organisms.
Our understanding of the shape and pattern of the history of life depends on the accuracy of fossils and dating methods.
Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better.