<P> Thermoluminescence testing also dates items to the last time they were heated . This technique is based on the principle that all objects absorb radiation from the environment . This process frees electrons within minerals that remain caught within the item . </P> <P> Heating an item to 500 degrees Celsius or higher releases the trapped electrons, producing light . This light can be measured to determine the last time the item was heated . </P> <P> Radiation levels do not remain constant over time . Fluctuating levels can skew results--for example, if an item went through several high radiation eras, thermoluminescence will return an older date for the item . Many factors can spoil the sample before testing as well, exposing the sample to heat or direct light may cause some of the electrons to dissipate, causing the item to date younger . </P> <P> Because of these and other factors, Thermoluminescence is at the most about 15% accurate . It cannot be used to accurately date a site on its own . However, it can be used to confirm the antiquity of an item . </P>

Absolute-age dating techniques can be used to determine the age of which of these