Dating techniques : radiocarbon (C-14)

a. Principle :

consists in estimating the age of a material containing carbon knowing that, in the biosphere, all living creatures comprise a constant quantity of radioactive carbon (C-14) relatively to the total amount of stable carbon but that, as soon these creatures die, they don't accumulate carbon anymore and their radioactivity diminish owing to the phenomenon of the radioactive decay. When one knows the rate of this decrease and the modern activity of the material, one can measure the activity (number of desintegrations of unstable atomic nuclei per second) of the object to be dated and therefore calculate its age

b. Applications :

all objects containing carbon (wood, ivory, bone, textile, paper, ...)

c. Limits :

• for all objects prior to 1660 A.D., we obtain a reliable date assorted with a certain margin of error
• for all objects which date between 1660 and 1954, we obtain a few possible dates each characterized by a different coefficient of probability (cf. important fluctuations of the C-14 grade of the atmosphere during these last 350 years)
• all dates subsequent to 1954 can be defined on account of the alteration of the C-14/C-12 ratio due to the nuclear trials

d. Remark :

the date obtained is that of the constitutive material and not the one corresponding to its workmanship