Start Reliability of radioactive dating

Reliability of radioactive dating

The discovery allowed him to correctly date a piece of wood from an Egyptian tomb that was known to be about 4,600 years old.

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Many people assume that the dates scientists quote of millions of years are as reliable as our knowledge of the structure of the atom or nuclear power.

A later method that used rubidium (which changes into strontium) proved more useful because it is found in nearly all rocks, although it still was not useful for younger specimens.

Perhaps the best method for rock dating is the potassium-argon method. Libby (1908–1980) discovered the radiocarbon method for determining the age of organic materials.

All plants absorb carbon during photosynthesis (the process in which plants use light energy to create food), and animals absorb this carbon by eating plants or eating other animals that ate plants.

Libby also found that as long as an organism remains alive, its supply of carbon-14 remains the same.

This method proved useful to date rocks as young as 50,000 years old. Called the carbon-14 dating technique, this ingenious method used the simple knowledge that all living plants and animals contain carbon (a nonmetallic element that occurs in all plants and animals).

Libby also knew that while most of this carbon is a common, stable form called carbon-12, a very small amount of the total carbon is radioactive carbon-14.

When a substance is described as radioactive, it means that at the subatomic (relating to parts of an atom) level, some parts of it are unstable.

When a substance is described as unstable, it means that it has a tendency to break down or decay.

Since each radioactive element decays at a known rate, it can be thought of as a ticking clock.