Nitrogen normally occurs in a seven proton, seven nuetron, nitrogen-14 state.When it collides with an energetic neutron it becomes carbon-14, with six protons and eight neutrons and gives off a hydrogen atom with one proton and zero neutrons. Carbon-14 is an isotope of carbon, which exists only is small amounts in the environment (1 in one trillion carbon atoms is carbon-14).The ratio of carbon-14 to carbon-12 in the atmosphere and on earth is nearly constant, although there has been some change in carbon-14 concentration over the last 10,000 years.

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Carbon-14 is created from nitrogen-14 in the upper atmosphere of the earth.

Radiation from the sun collides with atoms in the atmosphere.

These collisions create secondary cosmic rays in the form of energentic neutrons.

When these neutrons collide with nitrogen-14 in the atmosphere carbon-14 can be created.

This carbon-14 labeled carbon dioxide is taken up by plants in their normal process of photosynthesis.

Animals and people that eat these plants take the carbon-14 into their bodies as well.

Carbon-14 in the bodies of animals and plants is constantly decaying.

Carbon dating is used to determine the age of biological artifacts up to 50,000 years old.

This technique is widely used on recent artifacts, but teachers should note that this technique will not work on older fossils (like those of the dinosaurs which are over 65 million years old).

This technique is not restricted to bones; it can also be used on cloth, wood and plant fibers. The short half-life of carbon-14 means its cannot be used to date extremely old fossils.

Carbon-14 dating has been used successfully on the Dead Sea Scrolls, Minoan ruins and tombs of the pharohs among other things. Levels of carbon-14 become difficult to measure and compare after about 50,000 years (between 8 and 9 half lives; where 1% of the original carbon-14 remains undecayed).