The less radioactivity a carbon-14 isotope emits, the older it is. But the amount of carbon-14 in tree rings with known ages can help scientists correct for those fluctuations. To date an object, researchers use mass spectrometers or other instruments to determine the ratio of carbon-14 and carbon-12.

How is carbon-14 used in plants?

The carbon-14 atoms that cosmic rays create combine with oxygen to form carbon dioxide, which plants absorb naturally and incorporate into plant fibers by photosynthesis.

What is carbon-14 testing used for?

Radiocarbon dating uses carbon-14 to determine the last time something (or someone) was alive. Carbon-14 originates in the upper atmosphere of the earth and is created when neutrons originating from solar radiation bombardment collide with nitrogen in the air.