This plot shows the level of carbon-14 in the atmosphere as measured in New Zealand (red) and Austria (green), representing the Northern and Southern Hemispheres, respectively.Aboveground nuclear testing almost doubled the amount of carbon-14 in the atmosphere. The black arrow shows when the Partial Test Ban Treaty was enacted that banned aboveground nuclear tests. A special kind of radiocarbon dating: Bomb radiocarbon dating.It takes another 5,730 for half of the remainder to decay, and then another 5,730 for half of what's left then to decay and so on.The period of time that it takes for half of a sample to decay is called a "half-life." Radiocarbon oxidizes (that is, it combines with oxygen) and enters the biosphere through natural processes like breathing and eating. This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature.
Here’s an example using the simplest atom, hydrogen. Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.Most radiocarbon dating today is done using an accelerator mass spectrometer, an instrument that directly counts the numbers of carbon 14 and carbon12 in a sample.A detailed description of radiocarbon dating is available at the Wikipedia radiocarbon dating web page.As we mentioned above, the carbon-14 to carbon-12 ratio in the atmosphere remains nearly constant.It’s not absolutely constant due to several variables that affect the levels of cosmic rays reaching the atmosphere, such as the fluctuating strength of the Earth’s magnetic field, solar cycles that influence the amount of cosmic rays entering the solar system, climatic changes, and human activities.