Definition of absolute age dating
Perhaps the most widely used evidence for the Theory of Evolution through Natural Selection is the fossil record.The fossil record may be incomplete and may never fully completed, but there are still many clues to evolution and how it happens within the fossil record.A few days ago, I wrote a post about the basins of the Moon -- a result of a trip down a rabbit hole of book research.Here's the next step in that journey: the Geologic Time Scales of Earth and the Moon.The Wheeler Formation has been previously dated to approximately 507 million year old, so we know the trilobite is also about 507 million years old.But, how can we determine how old a rock formation is, if it hasn’t previously been dated?The half-lives of several radioactive isotopes are known and are used often to figure out the age of newly found fossils.Different isotopes have different half-lives and sometimes more than one present isotope can be used to get an even more specific age of a fossil.
The majority of the time fossils are dated using relative dating techniques. This process involves measuring the rate of decay of radioactive isotopes.Radioactive substances give off protons (positive particles) and neutrons (neutral particles) at a steady rate.The Geologic Time Scale is up there with the Periodic Table of Elements as one of those iconic, almost talismanic scientific charts.Long before I understood what any of it meant, I'd daydream in science class, staring at this chart, sounding out the names, wondering what those black-and-white bars meant, wondering what the colors meant, wondering why the divisions were so uneven, knowing it represented some kind of deep, meaningful, systematic organization of scientific knowledge, and hoping I'd have it all figured out one day.
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Using relative dating the fossil is compared to something for which an age is already known.