He eventually designed a device that used Geiger counters (which measure radiation) to accurately measure the amount of carbon-14 left in an organic substance.
Libby won the 1960 Nobel Prize in chemistry for his discovery.
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.
However, once the organism dies, the supply stops and the carbon-14 in its body begins to decrease according to its own rate of decay.
Libby realized that this could be a practical dating tool.
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Another drawback was that uranium is not found in every rock.
During this decay, one substance actually changes into another and radiation is released.
As long ago as 1907, the American chemist Bertram B.
Boltwood (1870–1927) suggested that knowledge of radioactivity might be used to determine the age of Earth's crust.
He suggested this because he knew that the end product of the decay of uranium was a form of lead.