The unreliability of carbon 14 date testing is a great concern to honest archaeologists.
They get particularly concerned when C14 testing shows obviously inaccurate results and they are left in uncertainty about the reliability of the dates that they have previously never questioned.
The most important archaeological dating method is radiocarbon dating.
It is a technique that can yield absolute dates with accuracy up to approximately 5000 years before present.
The stable C12 and C13, and the unstable or radioactive Carbon 14. Only one C14 atom exists for every one trillion C12 atoms.
Nitrogen atoms in the upper atmosphere are struck by cosmic radiation and create C14 atoms.
The industrial revolution has belched hundreds of thousands of tons of carbon gases into the atmosphere increasing the C12 ratio and atomic weapons testing have increased neutron levels.
Thirdly, the environment in which the artefact lies heavily impacts on the rate of decay.As with any radioactive particle it decays over time. Libby in 1948 at the University of Chicago, showed that C14, tested in his laboratory, decayed at the rate that, projected out, would cause half of its weight to be lost in 5568 years.Hence, the term ‘half-life’ was given to radioactive substances.For radiocarbon dating to be reliable scientists need to make a number of vital assumptions.Firstly, Dr Libby assumed that C14 decays at a constant rate.However, experimental evidence indicates that C14 decay is slowing down and that millennia ago it decayed much faster than is observed today.