Carbon dating practice questions
This is a digitized version of an article from The Times’s print archive, before the start of online publication in 1996.To preserve these articles as they originally appeared, The Times does not alter, edit or update them.
If a sample has 6.25 % of the amount of Carbon 14 present in a living sample then four half lives have passed since the sample died and stopped absorbing Carbon. Carbon 14 has a limited of approximately 50,000 years or less.
Uranium 234, a radioactive element present in the environment, slowly decays to form thorium 230.
Using a mass spectrometer, an instrument that accelerates streams of atoms and uses magnets to sort them out according to mass and electric charge, the group has learned to measure the ratio of uranium to thorium very precisely.
It is too soon to know whether the discovery will seriously upset the estimated dates of events like the arrival of human beings in the Western Hemisphere, scientists said.
But it is already clear that the carbon method of dating will have to be recalibrated and corrected in some cases.