Carbon dating is used to measure the age of biological objects like bones, cloth, wood and plant fibers. Its importance in tracing human history is undeniable. C-14 was used to tell the age of things like the Dead Sea Scrolls and tombs of Egyptian kings. Carbon 14 is referred to as a radioactive isotope of carbon. This means that it gives off radioactivity, although it is weak. Although this isotope is always decaying, living things continuously replenish the supply of C-14 by consuming it in their diet or from the air. When plants die or are used for things like paper, they no longer take in this carbon and the carbon decays. The same principle applies with animals after they die.
Establishing the age of a sample requires complex mathematical calculations. However, the premise is quite simple. Since living things are constantly taking in carbon, every piece of biological matter on earth contains the same amount of C-14. Scientists measure how much C-14 has decayed from the sample. Since researchers know exactly how slowly C-14 decays, they can count the amount of deterioration to establish an age. The more carbon decay in the sample, the older it is.
There are three different techniques used for dating C-14 isotopes. The first is called gas proportional counting. When carbon decays, it gives off things called beta particles. In order to determine the level of decay, the beta particles must be counted. In this case, the carbon sample is made into a gas form as carbon dioxide. Once this is complete, a machine called a gas proportional counter begins counting the beta particles.
Liquid scintillation is similar to the gas proportional method because it also counts beta particles. The carbon sample is put into a liquid form, after which a scintillator is added. A scintillator flashes brightly when it comes in contact with a beta particle. The flashes are counted by two devices called photomultipliers. When both photomultipliers pick up a flash of light, the flash is counted.
The third technique is called accelerator mass spectrometry. It is also the most efficient dating method available. Unlike its liquid and gas counterparts, it does not measure and count beta particles. Instead, it measures all of the carbon atoms in the sample and counts the amount of C-14 isotopes that are left.