What do scientists learn about fossils by using carbon-14?

Carbon-14 is a radioactive isotope of carbon which is unstable. Over time it decays or breaks down into more stable isotopes of carbon. Scientists know the percentage of carbon-14 that naturally occurs and do by measuring the percentage of carbon-14 in a fossil they can see how many half lives the fossil has gone through. This can tell them how old a fossil is and help them work out what time period it came from. If you want a more in depth explanation on half lives or this process (which is called carbon dating) send me a message!