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By: Ikedi Ani-okoye.

Carbon dating explained

This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature. C-12 is by far the most common isotope, while only about one in a trillion carbon atoms is C-14. C-14 is produced in the upper atmosphere when nitrogen-14 (N-14) is altered through the effects of cosmic radiation bombardment (a proton is displaced by a neutron effectively changing the nitrogen atom into a carbon isotope).

The new isotope is called "radiocarbon" because it is radioactive, though it is not dangerous. It is naturally unstable and so it will spontaneously decay back into N-14 after a period of time. It takes about 5,730 years for half of a sample of radiocarbon to decay back into nitrogen. It takes another 5,730 for half of the remainder to decay, and then another 5,730 for half of what's left then to decay and so on. The period of time that it takes for half of a sample to decay is called a "half-life."

Things that cant be Carbon dated

Yes. The method doesn't work on things which didn't get their carbon from the air. This leaves out aquatic creatures, since their carbon might (for example) come from dissolved carbonate rock. That causes a dating problem with any animal that eats seafood.

We can't date things that are too old. After about ten half-lives, there's very little C14 left. So, anything more than about 50,000 years old probably can't be dated at all. If you hear of a carbon dating up in the millions of years, you're hearing a confused report.

We can't date oil paints, because their oil is "old" carbon from petroleum.

We can't date fossils, for three reasons. First, they are almost always too old. Second, they rarely contain any of the original carbon. And third, it is common to soak new-found fossils in a preservative, such as shellac. It is also standard to coat fossils during their extraction and transport. Acetone is sometimes used while extracting fossils, because it dissolves dirt. 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.

We also can't date things that are too young. The nuclear tests of the 1950's created a lot of C14. Also, humans are now burning large amounts of "fossil fuel". 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.

CONCLUSION

Because the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old. However, the principle of carbon-14 dating applies to other isotopes as well. Potassium-40 is another radioactive element naturally found in your body and has a half-life of 1.3 billion years. Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).