Ever wonder how we know how old dinosaurs were? Or how long humans have been on the Earth? Well, it all comes down to a technique that scientists use called carbon dating. The process starts with the Sun’s radiation colliding with a N-14 causing a proton to fall off and creating C-14. This C-14 reacts with oxygen in the atmosphere to create CO2, which then follows the food chain. The interesting part is that when an animal dies, it stops consuming C-14. C-14 is an unstable isotope meaning that it will eventually go through radioactive beta decay to become N-14 with a half-life of 5,730 years.
This means that by looking at the ratio of the amount of C-14 to C-12 left in the remains of organic life, you can tell roughly how old long ago that specimen lived. C-12 is notably stable meaning its concentration will remain and will not decay any further. Carbon dating does have a limit as beyond a certain half-life the concentration of C-14 becomes too small. However, if you want to date much older things the same principle of carbon dating applies to other radioactive isotopes with much longer half-lives.
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