Radiometric dating worksheet when radioactive isotopes

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How do scientists know the bones are really 68 million years old?Today's knowledge of fossil ages comes primarily from radiometric dating, also known as radioactive dating.The more parent isotopes there are -- and the fewer daughter isotopes -- the younger the sample.The half-life of the isotope being measured determines how useful it is at dating very old samples.Once all the parents have become daughters, there's no more basis for comparison between the two isotopes.Scientists can't tell whether the clock ran down a few days or millions of years ago.When paleontologist Mary Schweitzer found soft tissue in a Tyrannosaurus rex fossil, her discovery raised an obvious question -- how the tissue could have survived so long?The bone was 68 million years old, and conventional wisdom about fossilization is that all soft tissue, from blood to brains, decomposes.

You can't predict when a specific unstable atom, or parent, will decay into a stable atom, or daughter.

Read on to see what it takes to date a fossil and what volcanic ash has to do with it.

They are also found in fossils and remains of organisms.

One way that helps scientists place fossils into the correct era on the Geologic Time Scale is by using radiometric dating.

Also called absolute dating, scientists use the decay of radioactive elements within the fossils or the rocks around the fossils to determine the age of the organism that was preserved.

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