Rubidium strontium dating formula

The oldest rock so far dated is a zircon crystal that formed 4.4-billion-years ago, which was only 200 million years or so after the Earth itself formed.YEC biblical literalists are necessarily bound to the dogmatic religious conclusion that the Earth is of a certain age based on a particular literal interpretation of the Genesis creation myth.It suffers from the problem that rubidium and strontium are very mobile and may easily enter rocks at a much later date to that of formation.This method for rock dating is based on the decay of potassium-40 into argon: until the rock solidifies, argon can escape, so it can in theory date the formation of rock.Radiometric dating — through processes similar to those outlined in the example problem above — frequently reveals that rocks, fossils, etc.are very much older than the approximately 6,000 to 10,000 years reckoned by young earth creationists.Symbolically, the process of radioactive decay can be expressed by the following differential equation, where N is the quantity of decaying nuclei and k is a positive number called the exponential decay constant.

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The time that it takes for half of a sample to decay is known as the half life of the isotope.The key is to measure an isotope that has had time to decay a measurable amount, but not so much as to only leave a trace remaining.Given isotopes are useful for dating over a range from a fraction of their half life to about four or five times their half life.We can measure directly, for example by using a radiation detector, and obtain a good estimate of by analyzing the chemical composition of the sample.The half-life , specific to each nuclide, can be accurately measured on a pure sample, and is known to be independent of the chemical composition of the sample, temperature and pressure.

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