Carbon dating and its importance

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• By Nivedita Kannan

Carbon dating is one of the scientific methods that has revolutionised man’s understanding not only of his present but also of the past. It is a concept that has itched our curiosity from little kids to young adults but we hardly know the backstory to such a marvellous discovery. Carbon dating is a form of radiometric dating, measuring the decay of carbon-14 atoms found in a once-living organism to determine when it was last alive. The upper atmosphere of the earth has a lot of nitrogen-14 atoms, which get bombarded by cosmic rays knocking of their neutrons and protons and forming new unstable carbon-14 atoms that are radioactive. The upper atmosphere also has carbon-12 atoms, which are much more abundant and also more stable. Carbon-14 atoms are formed at a reliable steady rate, which makes them very predictable, i.e. at any given time, we have a pretty good idea of the ratio of carbon-12 atoms to carbon-14 atoms in the atmosphere. Plants breathe in CO₂, animals feed these plants, and we consume both plants and animals. Basically, carbon-12 and carbon-14 atoms get in everything. The ratio is the same in these living organisms as in the atmosphere, i.e. predictable.

Some smart scientists found a formula to statistically predict this rate of decay. Like all radioactive particles, carbon-14 also has something called a half-life. Half-life is the time it takes for the number of radioactive particles in a sample to decrease in half. Carbon-14 has a half-life of 5,730 years. Using this concept, tracing back time takes us back to a point where there is no carbon-14 left. And now we would not know whether this took place a day before or 100,000 years before. This means that the time limit that we can date things using carbon-14 is roughly 50,000 years. We do that by measuring the rate of decay of carbon-14 atoms compared to the slow and steady carbon-12 atoms. It gets more interesting when we realise that future archaeologists are going to have a tough time using carbon-14 dating. Our industrial activities have been pumping CO₂ into the atmosphere and messing with the ratio of carbon-12 to carbon-14 atoms, and even more astounding is, all of the nuclear bombs that we set off are in the mid-20^th century. Nevertheless, we can still be very grateful for the concept as its application is existing not only in the archaeology field but also in geology, sedimentology, and lake studies.

Keywords: Carbon dating, Carbon-14, Carbon-12, Half-life, Radioactive, Decay

Image source:
Geological time spiral.png by United States Geological Survey, available under Public Domain at https://commons.wikimedia.org/wiki/File:Geological_time_spiral.png

Citation:
Nivedita Kannan. Carbon dating and its importance. The Torch. 2021. 2 (12).
Available from: https://www.styvalley.com/pub/magazines/torch/read/carbon-dating-and-its-importance/.

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