Figure 1: Diagram of the formation of carbon-14 (forward), the decay of carbon-14 (reverse). Both processes of formation and decay of carbon-14 are shown in Figure 1. The carbon-14 isotope would vanish from Earth's atmosphere in less than a million years were it not for the constant influx of cosmic rays interacting with molecules of nitrogen (N 2 ) and single nitrogen atoms (N) in the stratosphere. Carbon-14 has a relatively short half-life of 5,730 years, meaning that the fraction of carbon-14 in a sample is halved over the course of 5,730 years due to radioactive decay to nitrogen-14. There are also trace amounts of the unstable radioisotope carbon-14 ( 14C) on Earth. Carbon has two stable, nonradioactive isotopes: carbon-12 ( 12C) and carbon-13 ( 13C). It uses the naturally occurring radioisotope carbon-14 ( 14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years old. Radiocarbon dating (usually referred to simply as carbon-14 dating) is a radiometric dating method. Radiocarbon dating is used in many fields to learn information about the past conditions of organisms and the environments present on Earth. From this science, we are able to approximate the date at which the organism lived on Earth. However, when an organism ceases to exist, it no longer takes in carbon from its environment and the unstable 14C isotope begins to decay. The reason this process works is because when organisms are alive, they are constantly replenishing their 14C supply through respiration, providing them with a constant amount of the isotope. Radiocarbon dating is the process of determining the age of a sample by examining the amount of 14C remaining against its known half-life, 5,730 years. Although 12C is definitely essential to life, its unstable sister isotope 14C has become of extreme importance to the science world. When we speak of the element Carbon, we most often refer to the most naturally abundant stable isotope 12C.
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