# Isotopic age dating patterson

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You may have heard that the Earth is 4.54 billion years old. If the half-life of a material is 100 years and you have 1 kg of it, 100 years from now you will only have 0.5 kg of it.This was calculated by taking precise measurements of things in the dirt and in meteorites and using the principles of radioactive decay to determine an age. The rest will have decayed into a different nuclide (called a nuclide).Several radioactive nuclides exist in nature with half-lives long enough to be useful for geologic dating.Parts of the rock that have more Rb87 will end up with more Sr87.

By measuring a few samples of the rock and comparing the relative amounts of Sr87 and Rb87, we can figure out how old the rock is! If you think about it, the equation above is a lot like the formula for a line, \(y=mx b\) with \(y=\text_\), \(m= \left(e^-1 \right)\), \(x=\text_\), and \(b=\text_\).

This is the key to figuring out how much time has passed since the rock solidified.