Carbon dating stonehenge
In short, unless you have evidence to the contrary, you should assume that most of the carbon in a fossil is from contamination, and is not originally part of the fossil. The nuclear tests of the 1950's created a lot of C14.Also, humans are now burning large amounts of "fossil fuel".If you hear of a living tree being dated as a thousand years old, that is not necessarily an example of an incorrect dating. Wood taken from the innermost ring really is as old as the tree. We can date things for which historians know a "right answer".And, we can date things that have been dated by some other method.Radioactive atoms decay into stable atoms by a simple mathematical process.Half of the available atoms will change in a given period of time, known as the half-life.If you hear of a carbon dating up in the millions of years, you're hearing a confused report. Second, they rarely contain any of the original carbon.We can't date oil paints, because their oil is "old" carbon from petroleum. And third, it is common to soak new-found fossils in a preservative, such as shellac.
Potassium or uranium isotopes which have much longer half-lives, are used to date very ancient geological events that have to be measured in millions or billions of years.Then, we have wood for which we know the right answer.So, carbon dating has been calibrated against the rings of California bristlecone pines, and Irish bog oaks, and the like.As the name suggests, fossil fuel is old, and no longer contains C14.Both of these man-made changes are a nuisance to carbon dating.