That dating game
ESR can be used to evaluate materials up to one million years old and has become an indispensable tool for paleoanthropologists, who often use it to date the teeth of animal remains found among the precious human fossils.
AMINO ACID RACEMIZATION Over time, the amino acids that make up proteins slowly convert from their so-called left-handed state to their right-handed forma phenomenon known as racemization.
The decay of argon 40 to argon 39, for instance, played a vital role in underscoring the significance of two ancient human skulls unearthed in the Republic of Georgia last summer. Swisher III of the Berkeley Geochronology Center and his colleagues reported, are more than 1.7 million years old, and as such represent the first humans to leave Africa to colonize the rest of the world.
Argon dating can also be used to date materials as young as 10,000 years and as old as billions of years.
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.
In the case of thermoluminescence, resetting the crystal clock means heating it to around 500 degrees Celsius.Although Boltwood's resulting estimates for things like the age of Earthwhich he placed at around 2.2 billion yearshave since been significantly revised, he indicated correctly that our planet was far older than people had imagined possible.In the decades that followed, scientists made important new discoveries about the structure and behavior of atoms, and they refined their existing dating techniques.Geologists, paleontologists and archaeologists have pieced together a fairly detailed account of how Earth and its inhabitants evolved.But just how do researchers determine the ages of the materials they unearth?