Application of radioactive dating
Cosmic rays – high energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 isotopes.
Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.
Most carbon on Earth exists as the very stable isotope carbon-12, with a very small amount as carbon-13.
Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.
Here’s an example using the simplest atom, hydrogen. Cosmic rays bombard Earth’s atmosphere, creating the unstable isotope carbon-14.Radiocarbon dating uses isotopes of the element carbon. This isotope lets scientists learn the ages of once-living specimens from long ago.