Carbon Dating

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    • Recently, a court in Varanasi rejected a plea asking for a scientific investigation into the structure found inside the Gyanvapi Mosque that the Hindu side has claimed is a Shivling.
      • The dispute is now in the Supreme Court.  

    What is carbon dating?

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    • Carbon dating is a widely-used method to establish the age of organic materials, things that were once living.
      • Living things have carbon in them in various forms.
    • The dating method is based on the fact that Carbon-14 (C-14), an isotope of carbon with an atomic mass of 14, is radioactive, and decays at a well-known rate.
    • This is how it works: 
      • The most abundant isotope of carbon in the atmosphere is C-12. 
      • A very small amount of C-14 is also present. 
      • The ratio of C-12 to C-14 in the atmosphere is almost static, and is known.
      • Plants get their carbon through photosynthesis; animals get it mainly through food. Because plants and animals get their carbon from the atmosphere, they too acquire C-12 and C-14 in roughly the same proportion as is available in the atmosphere.
      • When they die, their interactions with the atmosphere stops. 
      • While C-12 is stable, the radioactive C-14 reduces to one half of itself in about 5,730 years known as its ‘half-life’. 
      • The changing ratio of C-12 to C-14 in the remains of a plant or animal after it dies can be measured, and can be used to deduce the approximate time when the organism died.

    What about non-living things? / Radiometric dating methods

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    • Carbon dating cannot be applied in all circumstances
    • 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 old cannot be arrived at through carbon dating.
      • This is because after 8-10 cycles of half-lives, the amount of C-14 becomes almost very small and is almost undetectable.
    • Radiometric dating methods: 
      • Many of these involve elements with half-lives of billions of years, which enable scientists to reliably estimate the age of very old objects.
      • Two commonly employed methods for dating rocks are:
        • Potassium-argon dating
        • Uranium-thorium-lead dating
      • The radioactive isotope of potassium decays into argon, and their ratios can give a clue about the age of rocks.
      • Uranium and thorium have several radioactive isotopes, and all of them decay into the stable lead atom.
      • The ratios of these elements present in the material can be measured and used to make estimates about age.

    Source: IE