Carbon dating and the shroud of turin
Carbon-14 has a half-life of 5,730 ± 40 years—, half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years.
Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon.
A weight of 20th century carbon equaling nearly two times the weight of the Shroud carbon itself would be required to change a 1st century date to the 14th century (see It may interest skeptics to know that many people of faith believe that there is scientific evidence which supports their belief in the shroud's authenticity.
Of course, the evidence is limited almost exclusively to pointing out facts that would be true the shroud were authentic.
Some believers think the crown of thorns was made of this type of tumbleweed. His sample of pollen grains originated with Max Frei, who tape-lifted pollen grain samples from the shroud.
Frei's pollen grains have been controversial from the beginning.
But even if there were blood on the shroud, that would have no bearing on the age of the shroud or on its authenticity.
It is claimed that the cloth has some pollen grains and images on it that are of plants found only in the Dead Sea region of Israel.
The method is widely used by Pleistocene geologists, anthropologists, archaeologists, and investigators in related fields.
(Another equally famous painting, also claimed to have miraculously appeared on a cloth, cropped up in Mexico in the 16th century, "Our Lady of Guadalupe.") The case for the forged shroud is made most forcefully by Joe Nickell in his Inquest On The Shroud Of Turin, which was written in collaboration with a panel of scientific and technical experts.