AAA,
Erm, I finally got the time to read up on carbon dating again. I'll try my best to explain, but it is kinda tough (even for me) so yar.
Anyway, you know carbon can be found in all living organisms. It is like the element of life. There is this naturally occurring carbon radioisotope called C14. The rest I'm quoting from wiki:
"One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains. This is a radiometric technique since it is based on radioactive decay. Carbon-14 is an unstable isotope of normal carbon, carbon-12. Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide. Carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. With death, the uptake of carbon-14 stops. Then this unstable isotope starts to decay into nitrogen-14. It takes 5,730 years for half the carbon-14 to change to nitrogen; this is the half-life of carbon-14. After another 5,730 years only one-quarter of the original carbon-14 will remain. After yet another 5,730 years only one-eighth will be left. By measuring the proportion of carbon-14 in organic material, scientists can determine the date of death of the organic matter in an artifact or ecofact."
Now, only when you measure organic remains, than you can be certain of the time. If you want to date artifacts that do not have an organic origin, then carbon dating can only be used on any accompanying organic remains. Meaning, if for some odd reason pottery that are 300 years old get buried with plants that are 1000 years old, there might be a problem with the dating, of course, besides carbon dating, there are other forms of dating artifacts (like how deep they are buried) but I'm just saying as an example. As of 2007, the upper limit of carbon dating is 60,000 years. So anything beyond that, you can't rely on carbon dating anymore.
Carbon dating has been calibrated on artifacts of known age such as those recorded in ancient text etc. and also tree rings. You know, as a tree grows, each year, it will form a ring so counting the rings will show you the number of years the tree had been living. Some trees have been around for thousands of years. Also, things like atomic bomb tests etc. will change the levels of C14 so scientists need to calibrate before they can use C14 to make accurate measurements.
Personally, i think it is fairly accurate plus minus a few hundred years. So what's the controversy about carbon dating you are talking about?