By measuring the amount of carbon-14 left in dead organic material the approximate time since it died can be worked out.For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.
When they die no new carbon-14 is taken in by the dead organism.
The carbon-14 it contained at the time of death decays over a long period of time.
Cancer cells absorb the radioactive substance more than normal cells.
This means they receive a higher dose of radiation, causing the cells to die.
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