Carbon-14

Carbon-14, also called radiocarbon, is a special kind of carbon that slowly changes over time. It was first found on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. This discovery helped scientists learn how to figure out the age of old things, like ancient artifacts or fossils.

There are three main kinds of carbon in nature: carbon-12, carbon-13, and carbon-14. Carbon-12 makes up almost all the carbon on Earth, and carbon-13 is less common. Carbon-14 is very rare, with only about 1.2 atoms of it for every trillion atoms of carbon in the air. Unlike the other two, carbon-14 is not stable and slowly turns into nitrogen-14 over time.

Scientists use carbon-14 to date old objects using a method called radiocarbon dating, which was developed by Willard Libby and his team in 1949. This helps us learn about history by telling us how long ago something lived or was made. Carbon-14 is created when high-energy particles from space, called cosmic rays, hit the air and change some nitrogen into carbon-14.

Radioactive decay and detection

Carbon-14 changes over time through a process called beta decay. During this process, one of the neutrons in carbon-14 turns into a proton. This changes carbon-14 into a stable form of nitrogen-14.

The change happens by sending out an electron and a tiny particle called an electron antineutrino. This decay process happens slowly, with carbon-14 taking about 5,700 years to lose half of its activity. Special tools are needed to find small amounts of carbon-14, and scientists use methods to study it.

Radiocarbon dating

Main article: Radiocarbon dating

Radiocarbon dating is a way to find out how old something is by using a special kind of carbon called ¹⁴C. This method can help us learn the age of materials that are up to about 60,000 years old. It was created by a scientist named Willard Libby and his team in 1949 when he worked at the University of Chicago.

One common use of this dating method is to figure out the age of old plants and animals. Plants take in carbon from the air as they grow, so the amount of ¹⁴C in a plant or animal when it dies is about the same as in the air at that time. After death, this amount slowly goes down, so by measuring it, we can estimate when the plant or animal died. This dating method helps scientists study how nature has changed over time.

Origin

Carbon-14 is made high up in the sky where the air is very thin. It forms when tiny particles from space, called cosmic rays, hit the air and create something called neutrons. These neutrons then change a type of air called nitrogen into carbon-14.

Besides this natural way, carbon-14 can also come from nuclear tests and power plants. When nuclear tests happened a long time ago, they put carbon-14 into the air. Even today, nuclear power plants can make small amounts of carbon-14.

Occurrence

Carbon-14 is a special kind of carbon that forms high up in the sky. It changes into a gas called carbon monoxide and then into carbon dioxide. This gas mixes around the world in a few weeks and can dissolve in the ocean, though this takes longer.

There is about 300 megacuries of Carbon-14 in the world, most of it in the oceans. In living things, the amount of Carbon-14 stays about the same as in the air. It can be used in medicine to help find problems.