Carbon-14, or radiocarbon, is a carbon atom which has 8 neutrons and 6 protons. Having 8 neutrons, carbon-14, is unstable, unlike other types of Carbon. Carbon-14 is one of three naturally occurring carbon isotopes. The others are Carbon-12 and Carbon-13. Carbon-14, or 14C, was discovered in 1934 by Franz Kurie. Carbon-14 makes up approximately one part-per-trillion of the carbon atoms in the atmosphere. Carbon-14 is used for Radiocarbon dating, or estimation on how old something is, based off of how much 14C is left over, since 14C breaks down at a known rate. Radiocarbon decomposes to a stable 13C isotope slowly over time. The isotope 14C has a half-life of approximately 5730 years. The following equation shows how Carbon-14 can be made: 1n + 14N → 14C + 1H. An explanation of this is in the troposphere and the stratosphere, thermal neutrons are absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo changes and transformations, including the creation of neutrons. Resulting neutrons(1n) participate in the equation above.