If a sample has 6.25 % of the amount of Carbon 14 present in a living sample then four half lives have passed since the sample died and stopped absorbing Carbon. Carbon 14 has a limited of approximately 50,000 years or less.
The percentage of Carbon 14 becomes extremely small and difficult to measure.
Learn about different types of radiometric dating, such as carbon dating.
Understand how decay and half life work to enable radiometric dating.
(This, in turn, is caused by variations in the magnetic fields of the earth and sun, for example.) Although the ratio of radiocarbon to stable carbon in the atmosphere has varied over time, it is quite uniform around the globe at any given time because the atmosphere mixes very quickly and constantly.
Plants obtain all their carbon atoms from the atmosphere.
This is because the amount and strength of cosmic radiation entering the earth's atmosphere has varied over time.
Part of the result of these collisions is the production of radiocarbon (C, pronounced "c fourteen"), carbon atoms which are chemically the same as stable carbon, but have two extra neutrons.
Radiocarbon is not stable; over time radiocarbon atoms decay into nitrogen atoms.
Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson. As we age, our hair turns gray, our skin wrinkles and our gait slows.
However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.