Carbon Dating [UPSC Notes]

Carbon dating is an important topic in the Geology as well as Science and Technology sections of the UPSC Exam. Hence, for the IAS Exam, aspirants should know about carbon dating as it is featured in the news in some form or the other often.

In this article, you can read all about carbon dating.

Carbon Dating

Carbon dating is a method to determine the age or date of organic materials that were once living. Archaeologists, palaeontologists and scientists use carbon dating to estimate the age of fossils and archaeological artefacts from ancient sites.

Living things have carbon in them in various forms. The carbon dating method makes use of the fact that a particular isotope of carbon called C-14, with an atomic mass of 14, is radioactive and decays at a rate that is well known. When living things such as plants and animals die, the radioactive carbon that they have accumulated begins to change. Carbon dating uses the decay of carbon-14 to estimate how long something has been dead.

How does Carbon Dating Work?

Carbon-14 is a weakly radioactive isotope of carbon (also known as radiocarbon).

• Carbon-14 is applicable only to organic and a few inorganic materials as living beings absorb carbon-14 from the atmosphere and food sources around them. Therefore, it is not applicable to most inorganic materials.

• There are three principles of carbon dating methods:
  • Gas Proportional Counting 
  • Liquid Scintillation Counting
  • Accelerator Mass Spectrometry

Carbon Dating Impact

The carbon dating technique has had a huge impact on the modern world and has been one of the most significant discoveries of the 20th century, in fact, leading to the “reconstruction of the history of the world”.

• No other scientific method has managed to revolutionize man’s understanding not only of his present but also events that already happened thousands of years ago.
• Carbon dating is the technique widely used by archaeologists, scientists and other human sciences to prove or disprove theories.
• Geology, geophysics, hydrology, atmospheric science, palaeoclimatology, oceanography and even biomedicine has applications from carbon dating over the years.
• The Shroud of Turin – whose image is believed to represent Jesus Christ, is one of the most popular cases where scientists used carbon dating for their investigation. In 1988, scientists determined that it originated in the 13th century, 1200 years later after the death of Jesus Christ.

Image Source: Bbc.com

Basic Principles of Carbon Dating

• Carbon-14 is an isotope of the element carbon that is weakly radioactive and unstable.
  • The stable isotopes are carbon-12 and carbon-13.
• Carbon-14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons in nitrogen 14 atoms.
  • It is rapidly oxidized in air to form carbon dioxide and enters the global carbon cycle.
• 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.

Carbon – 14 Datable Materials:

• Most, if not all, organic compounds can be dated. Some inorganic matters can also be dated as long as the minerals’ formation involved the assimilation of carbon-14 in equilibrium with the atmosphere.
• Samples that have been carbon dated since the inception of the method include- 
  • Charcoal, wood, twigs, seeds, bones, shells, leather, lake mud, fabrics, soil, hair, pottery, peat, pollen, wall paintings, corals, blood residues, paper or parchment, resins and water among others.

Carbon Dating Limitations

In this section, the limitations of the carbon dating method are mentioned.

• Limited to Organic Materials: Carbon dating is only applicable to organic materials. It cannot be used to determine the age of rocks, metals, or other inorganic materials.
• Sample Size: The sample size used for carbon dating is relatively small, usually only a few grams of material. This means that the sample may not be representative of the entire object being dated.
• Contamination: Carbon dating can be affected by contamination from outside sources. This can occur during the collection or preparation of the sample, or during the dating process itself.
• Age Limitations: Carbon dating is only accurate up to a certain age. Beyond a certain point, the amount of carbon-14 remaining in a sample is too small to measure accurately, resulting in a maximum age limit of around 50,000 years.
• Calibration: Carbon dating relies on the assumption that the ratio of carbon-14 to carbon-12 in the atmosphere has remained constant over time. However, changes in the atmosphere’s composition can lead to inaccuracies in the dating process. Calibration is required to account for these changes.
• Interpreting Results: Carbon dating provides a range of possible ages for a sample, rather than a precise date. Interpreting the results requires knowledge of the sample’s context and potential sources of error.
• Limited Applicability: Carbon dating is only applicable to materials that were once alive and have carbon-based structures. This limits its usefulness for dating certain types of objects, such as ceramics or metal artefacts.

Carbon Dating Latest News

The Allahabad High Court, in May 2023, ordered a scientific survey, including carbon dating, of a “Shivling” found inside the Gyanvapi mosque complex in Varanasi to determine its age and other constituents.

Gyanvapi Mosque and Carbon Dating: Carbon dating has been proposed as a potential method for determining the age of the disputed Shivaling at the Gyanvapi mosque in Varanasi, India. 

• The Gyanvapi mosque stands on the site of an older temple, which some Hindus believe was dedicated to Lord Shiva.
• In 1998, a local court ordered a survey of the site to determine whether there was evidence of a pre-existing temple.
• The survey found several features that were consistent with the remains of a temple, including a stone slab with Hindu iconography and a structure resembling a doorway.
• In April 2021, a petition was filed in the Allahabad High Court seeking permission for a comprehensive archaeological survey of the site, including carbon dating of the disputed Shivaling.
• The petitioner argues that carbon dating could help establish the age of the Shivaling and determine whether it predates the mosque.
• However, there are some challenges to using carbon dating in this context, including the fact that the Shivaling has likely been exposed to a variety of environmental factors that could affect its age.
• In addition, there are concerns about the potential misuse of scientific evidence in the context of a highly politicized and sensitive issue.
• Recently, Allahabad High Court has also removed the carbon dating of the Shivalinga inside the Gyanvapi Mosque to determine its age and settle the dispute over its origins and ownership.

Conclusion: The ongoing Gyanvapi mosque case has highlighted the complexities and sensitivities involved in archaeological and historical investigations. The use of modern scientific techniques, such as carbon dating, can aid in determining the age of artefacts and structures, but their interpretation should be done with caution and in conjunction with other evidence and perspectives.

Also read: Minerals and Rocks

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