Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.Examples: For all of these, and more, reasons, calibration is needed in C-14 dating.
As a result it is always undergoing natural radioactive decay while the abundances of the other isotopes are unchanged.
Carbon-14 is most abundant in atmospheric carbon dioxide because it is constantly being produced by collisions between nitrogen atoms and cosmic rays at the upper limits of the atmosphere.
I understand calibration might have something to do with this, but then in the article it says in italicized words that the uncalibrated date “Must Always Be Mentioned”. CMI’s Dr Rob Carter responds: Anthony, As a fan of biblical archaeology, I was asked to address your question.
But when I read articles about the results, they never mention the uncalibrated data, which could actually be correct. I am not an expert in every subject that impinges on the discussion, but I will do my best.
They have masses of 13 and 14 respectively and are referred to as "carbon-13" and "carbon-14." If two atoms have equal numbers of protons but differing numbers of neutrons, one is said to be an "isotope" of the other.
Carbon-13 and carbon-14 are thus isotopes of carbon-12.
This does not mean that recalibration is bad, indeed it is necessary, but it should make one more soberly assess any reported dates as being tentative.
The problem is that most people reporting on these issues fail to report the initial number along with the calibrated date. The Jericho controversy is soundly rooted in C-14 calibration.
American physical chemist Willard Libby led a team of scientists in the post World War II era to develop a method that measures radiocarbon activity.