Science Questions

Can you tell me how carbon dating works? Roland in Cambridgeshire

With carbon dating we're talking about different isotopes of carbon. This basically means different forms of the element. Most of the carbon in the world is a form called carbon 12, which means that there are six neutrons and six protons in the nucleus. There is also a heavier but much rarer form of carbon called carbon 14 and that's also slightly radioactive. The fact that it is radioactive means that it will break down over time. When plants photosynthesise, they take on some of this C14 and have an amount of it in their tissues. Once they die, that carbon 14 starts to break down. If you can measure the amount of carbon 14 in that organism, you can tell how long ago it died. It's effective for about 40 000 years.

September 2006