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EducationWhy carbon-dating Gyanvapi mosque's interiors may not be viable

Why carbon-dating Gyanvapi mosque’s interiors may not be viable

The court allowed a petition on 22 September that asked for carbon dating of the structure inside the Gyanvapi mosque that the Hindu side has claimed is a Shivling (Linga). The court issued notices to other parties, seeking objections if any.

Carbon dating is an established radioactive method employed to determine the age of organic material, things that were once living and, therefore, are bound to decay. Living things have carbon in them in different forms. The dating method makes use of the fact that an isotope of carbon C-14, with an atomic mass of 14 rather than 12 (double the number of protons in its nucleus, which is the atomic number), disintegrates at a known rate.

The most abundant isotope of atmospheric carbon is carbon 12 while carbon 14 is sparse. The ratio of carbon-12 to carbon-14 in the atmosphere is more or less static and known too.

Carbon-dating things that were once living

Plants get their carbon through the process of photosynthesis whereas animals get it mainly from food. Since both plants and animals get carbon from the atmosphere, they accumulate both isotopes in roughly the same proportion as is available in the atmosphere. However, when they die, the body stops further intake as well as emission of carbon, as metabolism has stopped. In this situation, carbon-12 does not decay, though, but carbon-14 does because it is radioactive. Carbon-14 reduces to half its volume in about 5,730 years. This is referred to as its "half-life" in the lingo of physics and chemistry.

Now, the ratio of C-12 to C-14 in the body or remains after a plant or animal dies starts changing. This change can be measured and used to deduce the approximate time when the organism died.

Difficulty in carbon-dating objects

Though quite effective, carbon dating cannot be applied in all circumstances. Specifically, it cannot be used to determine the age of non-living things, like rocks, for example. Also, the age of things that are more than 40,000-50,000 years cannot be arrived at through carbon dating. This is because, after eight to ten cycles of half-lives, the amount of C-14 becomes negligible and undetectable.

Other methods are employed to calculate the age of inanimate things, but carbon dating can be used in an indirect way in certain circumstances like determining the age of the ice cores in glaciers and polar regions. This is done by studying the carbon dioxide molecules trapped inside large ice sheets. The trapped molecules have no interaction with the ambient atmosphere and are found in the same state as when they were trapped.

How long a rock has been at a particular place can be determined using similar indirect methods. If there are organic materials, dead plants or insects trapped beneath the rock, they can give an indication of when that rock, or any other thing, had reached that place.

Other methods to date sedimentation around an object are used at times. In the Gyanvapi case, the petitioners want to establish that the ‘Shivling’ existed where it is seen now before the mosque came up on the spot. Ascertaining that is possible on paper.

Though several methods exist to know the age of a certain object, not everything can be dated. The accuracy of the methods varies too.

Challenges in applying the C-14 decay method to Gyanvapi interiors

Although Hindu petitioners in the Gyanvapi case have asked for carbon dating, it is not clear yet whether carbon dating can be applied in this case or if some other method would be suitable. 

Some methods, like looking for trapped organic material beneath it, might not be feasible for reasons such as the date of the sedimentation must have arrived long after it allegedly went inside the Gyanvapi mosque. Then, finding the sediments would involve uprooting the structure or making some other disruptions that are not desirable. What can be done to date the structure can be finalised only after a detailed scientific study.

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