Carbon-14 is considered a radioactive isotope of carbon. Because its unstable, carbon-14 will eventually decay back to carbon-12 isotopes. And thats the key to radiocarbon dating. Scientists measure the ratio of carbon isotopes to be able to estimate how far back in time a biological sample was active or alive.

Why is carbon useful in absolute dating?

Absolute dating methods measure the physical properties of an object itself and use these measurements to calculate its age. One of the most useful absolute dating methods for archaeologists is called radiocarbon dating. When they die, the carbon-14 in their wood and bone starts its radioactive decay process.