How is carbon dating
It is not difficult to see how such a claim could arise, however.There are two characteristics of the instrumental measurement of radiocarbon which, if the lay observer is unaware, could easily lead to such an idea.In the early days of radiocarbon analysis this limit was often around 20,000 radiocarbon years.
Reports of young radiocarbon ages for coal probably all stem from a misunderstanding of one or both of these two factors.
First, any instrument which is built to measure radiocarbon has a limit beyond which it cannot separate the signal due to radiocarbon in the sample from the signal due to background processes within the measuring apparatus.
Even a hypothetical sample containing absolutely no radiocarbon will register counts in a radiocarbon counter because of background signals within the counter.
Measurements made using specially designed, more elaborate apparatus and more astute sampling-handling techniques have yielded radiocarbon ages for anthracite greater than 70,000 radiocarbon years, the sensitivity limit of this equipment. Continuous series of tree-ring dated wood samples have been obtained for roughly the past 10,000 years which give the approximate correct radiocarbon age, demonstrating the general validity of the conventional radiocarbon dating technique.
Several long tree-ring chronologies have been constructed specifically for use in calibrating the radiocarbon time scale.
Other radiometric dating methods such as potassium-argon or rubidium-strontium are used for such purposes by those who believe that the earth is billions of years old.