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By passing accelerated carbon atoms through argon gas, the instrument next stripped electrons from the carbon atoms, thereby giving them positive charges.
In the process, ''background'' molecules having the same masses as carbon atoms were removed, eliminating a potential source of error.
The method developed in the 1940's and was a ground-breaking piece of research that would change dating methods forever. Libby calculated the rate of radioactive decay of the C isotope (4) in carbon black powder.
As a test, the team took samples of acacia wood from two Egyptian Pharaohs and dated them; the results came back to within what was then a reasonable range: 2800BC /- 250 years whereas the earlier independent dates (largely the dendrochronology records) were 2625 /- 75 years (3), (5).
The three laboratories conducting the analyses were at the University of Arizona in Tucson, the British Museum in London and the Swiss Federal Institute in Zurich.Heavier atoms are deflected less by the magnetic fields than are lighter atoms, and this difference separates the trajectories of atoms according to their masses. Donahue of the University of Arizona explained in an interview that the instrument's very high energy endows it with great precision.By counting the atoms that strike any given part of the detector, the apparatus can estimate their abundance in the original sample. The accelerator, which can impart an energy of 10 million electron volts to the atoms it accelerates, can easily distinguish between the carbon atoms of interest and other atoms and molecules having the same mass that must be excluded from the result.Finally, the electrically charged carbon atoms emerging from the accelerator were sorted out by magnetic fields, permitting precise measurement of the ratio between carbon 14 and carbon 13.From this, scientists concluded that the flax plants from which the linen in the Shroud of Turin was made were grown in medieval times, long after the death of Jesus.
Living organisms assimilate carbon 14 from the environment along with two stable isotopes, or forms, of carbon - carbon 12 and carbon 13.