Every living thing, animal or plant must have carbon to live and this is being taken in, or constantly, else the organism dies. Carbon dioxide is the process formed after an oxidation process has taken place. The food eaten is oxidized and the resultant used oxygen is carbon dioxide that will be breathed out and a fresh supply of oxygen is taken in. A simple explanation of carbon is the after effects of oxygen combustion. The body, therefore is constantly taking in carbon while it is alive and stops taking in new carbon when it dies. Carbon is a necessity for life.
Carbon 12, the regular carbon, stays constant in the living organism, but carbon 14 is the carbon that is decaying. Its half life is 5,700 years. Therefore a scale model of a human, a plant, a rock, or some other substance must be known as to its content of carbon 12 and its relative content of carbon 14. Then when a fossil or some other material that is to be carbon dated is examined and the age is to be determined, the amount of carbon 14 left in the organism is calculated as to how much has already vanished and how much remains.
According to How Stuff Works, Carbon 14 dating, with its 5,700 half life, is only good to measure the age of artifacts no older than 60.000 years. Otherwise there will be no carbon 14 in the fossil. Deciding the age of the object to be carbon dated is a matter of subtracting the amount of carbon 14 found in the object against the relative amount that it had when it was alive.
For this to be a viable way of determining the age of artifacts and other substances, a few facts must be understood. When an object is no longer alive, it no longer takes in new carbon, as in trees and plants and animals. How is carbon 14 created in the first place is a most logical question?
Cosmic rays are delivered to the earth by the sunshine and other forces from the atmosphere. Possibly a ray from the sun came into contact with an atom floating around and this changed the ray into a lively neutron that ran into or was attracted by nitrogen in the air. Nitrogen 14 has an equal amount of protons and neutrons, seven of each - and then turns into carbon14 by losing one of its protons and gaining a neutron. It is now radioactive and has a life of 5,700 years.
Carbon 14 atoms, when aligned with oxygen, create carbon dioxide and are taken in by plants by the mechanism of photosynthesis. In other words, they must have light to complete this process. People and animals who eat the plants take in carbon 14 as a matter of process. However, for stability, the ratio of carbon 12, the normal variety, to carbon 14 remains nearly constant. In the human body, all above this normal ratio is passed off by the body's waste disposal system.
Therefore while the process of carbon dating sounds as if it might be a little like hocus-pocus and a guessing game, there is solid evidence that it is a science that has been carefully thought through. While there may be errors in the process, educated guesses as to the age of specimens, even those older than the 5,700 years, can arrive somewhere at the near age.
Where carbon 14 is used most effectively is in classifying fossils, rocks, and found bones of animal and humans, and giving clues as to their age. This is important and may add to further knowledge about how people lived in times past. By this method, too, human skeletal bones be aged as to an approximate time of death.