Radioactive decay dating method
"The rate of diffusion will vary, based on the sample -- what type of rock it is, the number of cracks and amount of surface area, and so on," Hayes says.
"So, there's not a simple equation that can be applied to every circumstance.
So, researchers "normalize" the data by making a ratio with strontium-86, which is stable -- meaning it doesn't decay over time.
"It's a slow process, but not necessarily a negligible one when you're talking about geological time scales," says Robert Hayes, an associate professor of nuclear engineering at NC State and author of a paper describing the work.If we knew the fraction of a radioactive element still remaining in a mineral, it would be a simple matter to calculate its age by the formula To determine the fraction still remaining, we must know both the amount now present and also the amount present when the mineral was formed.Contrary to creationist claims, it is possible to make that determination, as the following will explain: By way of background, all atoms of a given element have the same number of protons in the nucleus; however, the number of neutrons in the nucleus can vary.Then, by assessing the isotope concentrations of rubidium and strontium, scientists can back-calculate to determine when the rock was formed.The three isotopes mentioned can be used for dating rock formations and meteorites; the method typically works best on igneous rocks. The data from radioisotope analysis tends to be somewhat scattered.