Holocene radiometric dating
It is the supposed accuracy of the new method that allows measurements sensitive enough to date objects claimed to be more than twenty or thirty thousand years old.
A recent test by the British Science and Engineering Research Council has shown that the accuracy of the new technique is greatly overrated.
As you might guess, radioactive carbon (C) is quite rare.
Only one out of every trillion carbon atoms is C14. The C14 created in the upper atmosphere reacts with oxygen to become carbon dioxide.
They found large variations in the radiocarbon 'dates' of objects of known age sent to 38 radiocarbon 'dating' laboratories around the world.
Thirty-one of the labs gave results that the British group called unsatisfactory.
It uses accelerator mass spectrometry to determine the amounts of C14 and C12 in a small sample which is vaporised in the test.
However, because it has too many neutrons for the number of protons it contains, it is not a stable atom.