Carbon Dating Accuracy

Carbon dating accuracy is a widely used technique to determine the age of archeological objects, fossils or any remnant from the past. The phenomenon of radioactivity makes carbon dating possible. The method was developed by Willard Libby and his associates in 1949. The impact of carbon dating on the world of science, led to Libby being awarded the Nobel Prize in Chemistry in 1960.

The carbon dating method is based on comparison of ratios of two isotopes of carbon which are C-12 and C-14. C-14 is radioactive while C-12 is not. Isotopes are elements with the same atomic number, but different atomic mass numbers. C-14 has a half life of approximately 5730 years. By comparing the amount of radioactive carbon present now, with the amount at the beginning, an age estimate can be made based on laws of radioactive decay. Why was carbon chosen for the dating method, out of all the list of radioactive elements? One reason is the fact that it has a radioactive isotope and second reason is that life is based on carbon compounds! This made age determination of carbonaceous life possible.

Reasons for Limitations on Carbon Dating Accuracy

Below we have discussed the reasons for doubting carbon dating accuracy and see what are the inherent limitations of this method. Every scientific method has its limitations. This is because the fundamental assumptions or axioms, on which a method like carbon dating is based, are only approximately true or accurate. All the physical laws we know have limits of validity. The fact that scientific methods like carbon dating fail beyond a certain domain of approximation, doesn't make them redundant. It only means that these need to be used with caution and with a knowledge of the limits of their accuracy. Carbon dating accuracy is not perfect but its deviation from accurate values can be improved.

C-14/C-12 Ratio is Not Absolute
The carbon dating accuracy is largely dependent on an assumed absolute ratio of C-14 to C-12 which is supposed to have remained constant over time. However, in reality the ratio varies with time and place.

C-14 is created in the upper layers of the atmosphere by the bombardment of Nitrogen with cosmic rays. It then enters the lower atmosphere and gets distributed forming carbon dioxide in the process. This carbon dioxide made of radioactive carbon is assimilated by plants through the process of photosynthesis and it enters into food cycle. Carbon forms the backbone of life on earth.

This ratio of carbon-14 to carbon-12 is taken to be the one detected, in 1950, which is taken as the 'Present' or the point in time up to which the age is determined. Hence the ages are given as for example, 3400 BP (3400 years BP). Where 'BP' stands for before present. The flaw in this method is that, it assumes that the carbon 14/carbon 12 ratio has been the same till 1950, which is not the case in reality. However, this problem is taken care of by calibration curves which account for the change in the ratio. Still, this changing ratio of carbon isotopes does make a minuscule dent in carbon dating accuracy.

Contamination of Carbon Dating Sample
There is another possibility which may affect carbon dating accuracy. It is necessary that the carbon dating sample be as uncontaminated as possible, to give it an accurate age. However, that may not be possible for samples which are too old. The possibility of contamination of very ancient samples is unavoidable. Contamination disturbs the ratio of carbon isotopes found in situ, in the sample. This may lead to an inaccurate determination of age. There is nothing we can do in this case. However, error in determination of age by carbon dating methods can be compensated by using other dating methods, which use radioactive elements other than carbon.

So if you ask me, how accurate is carbon dating, I would say quite accurate if you take its inherent limits into consideration. It is inaccurate at times but its error levels are very low and certainly not inaccurate enough to be called wrong! Carbon dating accuracy is not perfect, but it has given remarkably accurate results, when tested to calculate age of artifacts, whose age was known, by other methods. It has given consistently accurate results of varying kinds of objects. After all, no method that dependents on multiple variables, which are out of our control, can be accurate!