Dating geological specimens crystal kay dating
Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades.The latest high-tech equipment permits reliable results to be obtained even with microscopic samples.Technical details on how these dates are calculated are given in Radiometric dating. As with any experimental procedure in any field of science, these measurements are subject to certain "glitches" and "anomalies," as noted in the literature.Here is one example of an isochron, based on measurements of basaltic meteorites (in this case the resulting date is 4.4 billion years) [Basaltic1981, pg. Skeptics of old-earth geology make great hay of these examples.There's a small amount of radioactive carbon-14 in all living organisms.When they die no new carbon-14 is taken in by the dead organism.(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.
These materials have a variety of uses and a selection of these are listed below.(a) dating geological specimens, using uranium, rubidium or bismuth; (b) dating archaeological specimens, using carbon 14(c) paper or plastic thickness measurement using beta radiation(d) treatment of tumours;(e) sterilisation of foodstuffs;(f) nuclear pacemakers for the heart;(g) liquid flow measurement;(h) tracing sewage or silt in the sea or rivers;(i) checking blood circulation and blood volume;(j) atomic lights using krypton 85;(k) checking the silver content of coins;(I) radiographs of castings and teeth;(m) testing for leaks in pipes;(n) tracing phosphate fertilisers using phosphorus 32(o) smoke alarms (p) sterilisation of insects for pest control.
To determine the ages of these specimens, scientists need an isotope with a very long half-life.
Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.
This is what archaeologists use to determine the age of human-made artifacts. The half-life of carbon-14 is only 5,730 years, so carbon-14 dating is only effective on samples that are less than 50,000 years old.
Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.