However, the carbon-14 already in the organism's body continues to decay at a constant rate.
Therefore, the amount of carbon-14 in an artifact decreases at a predictable rate while the amount of carbon-12 remains constant.
This restriction extends to animals that consume seafood in their diets, as well.
Carbon dating also cannot be used on artifacts over about 50,000 years old.
These artifacts have gone through many carbon-14 half-lives and the amount of carbon-14 remaining in them is miniscule and very difficult to detect.
Carbon dating cannot be used on most fossils, not only because they are almost always too old, but also because they rarely contain the original carbon of the organism.
These collisions create secondary cosmic rays in the form of energentic neutrons.
When it collides with an energetic neutron it becomes carbon-14, with six protons and eight neutrons and gives off a hydrogen atom with one proton and zero neutrons. Carbon-14 is an isotope of carbon, which exists only is small amounts in the environment (1 in one trillion carbon atoms is carbon-14).PADUA, Italy — Just in time for the current Easter season, news emerged from Italy that a new approach to dating the Shroud of Turin has located it squarely in the time frame necessary for it to have wrapped the crucified body of Jesus Christ.A new book written in Italian, (The Mystery of the Shroud), by Giulio Fanti, professor of mechanical and thermal measurement at the University of Padua’s Engineering Faculty, and journalist Saverio Gaeta, states that by measuring the degradation of cellulose in linen fibers from the shroud, two separate approaches show the cloth is at least 2,000 years old.Scientists now realize that production of carbon-14 has not been constant over the last 10,000 years, but has changed as the radiation from the sun has changed.Carbon dates reported in the 1950s and 1960s should be questioned, because those studies were conducted before carbon dating was calibrated by comparision with other dating methods.