Thermoluminescence is another dating technique. It does not rely directly on half-lives but uses the fact that radioactive decay causes some electrons to end up in a state of higher energy. The longer the radioactivity, the more high-energy electrons collect. If the material is then taken into a lab and heated, it puts the higher-energy electrons back into their normal orbits. As the orbits return to normal, a small amount of light is given off. This measurement can be calculated into an age. This technique is useful to date materials less than half a million years old.
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