Carbon 14 dating summary
It is not uncommon for a cosmic ray to collide with an atom in the atmosphere, creating a secondary cosmic ray in the form of an energetic neutron, and for these energetic neutrons to collide with nitrogen atoms.When the neutron collides, a nitrogen-14 (seven protons, seven neutrons) atom turns into a carbon-14 atom (six protons, eight neutrons) and a hydrogen atom (one proton, zero neutrons).The carbon-14 atoms that cosmic rays create combine with oxygen to form carbon dioxide, which plants absorb naturally and incorporate into plant fibers by photosynthesis.Animals and people eat plants and take in carbon-14 as well.Carbon-14 is radioactive, with a half-life of about 5,700 years.For more information on cosmic rays and half-life, as well as the process of radioactive decay, see How Nuclear Radiation Works.
It can also be pressed into shapes and is used to form the cores of most dry cell batteries, among other things.
Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.
When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
Graphite, one of the softest materials known, is a form of carbon that is primarily used as a lubricant.
Although it does occur naturally, most commercial graphite is produced by treating petroleum coke, a black tar residue remaining after the refinement of crude oil, in an oxygen-free oven.