Dating geological specimens
(a) Iodine-131 with a half-life of 8.0 days and activity of 8 C may be taken as liquid or in a capsule.(b)Technetium-99 with a half-life of 6 hours gives gamma-rays of 140 ke V energy.(c) Iodine-123 is suitable for medical studies since it gives no beta- radiation.(d) Cobalt-60 sources of up to 10 000 curies have been used; such a source gives 200 R per minute at 1 m. The very long half-lives of these isotopes make them particularly suitable for finding the age of rocks.For example if you consider the uranium series that the final stable isotope is lead-206, and if we assume that there was no lead in the rock when it was formed the ratio of the number of atoms of lead 206 (N The carbon 14 is then absorbed by plants; these in turn are eaten by animals which may then be eaten by other animals.In a separate article (Radiometric dating), we sketched in some technical detail how these dates are calculated using radiometric dating techniques.As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.
When they die no new carbon-14 is taken in by the dead organism.
These skeptics do not provide scientific evidence for their views.
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.
In the past 150 years they have not found any fossils that Darwin would not have expected.
New discoveries have filled in the gaps, and shown us in unimaginable detail the shape of the great ‘tree of life’.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.