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Carbon 14 can thus reliably date items only up to around 40,000 years old.Other radioactive isotopes can be used to accurately date objects far older.Researchers can thus determine the amount of time that has passed since the buried crystal was last exposed to heat.In the case of thermoluminescence, resetting the crystal clock means heating it to around 500 degrees Celsius.
In the decades that followed, scientists made important new discoveries about the structure and behavior of atoms, and they refined their existing dating techniques.
Each isotope has what is known as a half-lifethat is, a period of time in which half of the atoms in a population decay into stable daughter elements.
This half-life differs dramatically from isotope to isotope.
ANCIENT ARTWORK, such as this Chinese horse, can be evaluated using thermoluminescence.
The dating confirmed that the horse does indeed date back 1,000 years to the Tang dynasty, as its style suggests.
Still others, like amino acid racemization, show promise but have not yet taken wing.