How does “Carbon Dating” work?
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a tiny fraction of carbon in the environment is slightly radioactive, when a living organisms eats it takes in some of this radioactive carbon and as it ages some is lost so the ratio is fairly constant
when an organism dies the radioactive carbon stays in them and slowly the radioactive one decays at a predictable rate and tuns into nitrogen, by measuring how much radioactive carbon-14 is left, you can estimate how long ago that thing died
It’s first important to note that carbon dating is something done on things that were alive and are now dead. Specifically. There are other radio dating techniques for minerals, and there are other techniques for dating really old but alive creatures.
There’s a constant process in which nitrogen in the atmosphere is converted into Carbon 14, which then can combine with oxygen to form carbon dioxide. Normally carbon has 6 protons and 6 neutrons (for a total of 12, Carbon 12). Carbon 14 has 8 neutrons. This C14 CO2 is absorbed by plants as normal, and integrated into their structure. When animals eat the plants, they use their carbon fir themselves as well. So this C14 will be carried through.
The important thing here is that the amount of C14 to C12 is a known ratio. And the amount of it in the bodies of plants and animals when alive will be the about the same (with some known caveats) as the atmospheric ratio. So you know how much the living being should have had when they were alive.
Now, the next thing is that C14 is radioactive. It decays. And the half live (how long it takes for half of it to disappear) is 5730 years.
So you know how much C14 a sample should have had. We can measure how much C14 it actually has. Because we know the decay rate, we can fairly accurately tell how long it would have taken for the missing amount to disappear. We now know how long ago the creature died.
Most organic matter contains carbon. Atoms of carbon all have the same number of protons, but different isotopes of carbon have a different numbers of neutrons. Carbon-14, C-14, ¹⁴ C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its half-life (time it takes to reduce its radioactivity by half) is about 5,730 years. This makes it possible to tell the age of substances that contain carbon as long as they are less than about 60,000 years old.
Scientists measure the amount of carbon-14 present in the sample and compare this against the known half-life of carbon-14. Carbon-14 is ordinarily at the same level among all living organisms, but that equilibrium ends once the organism dies. So by measuring the amount of carbon-14 remaining in a once-living organism, one can determine when it was still alive, and therefore the approximate age of the organic matter.
Imagine there’s a water leak at an abandoned house. It leaks water at a known pace, so if we go in the house an measure the amount of water, we can have an idea of how long it’s been leaking.
With living organisms, after they die, they begin to change. In particular for carbon dating, we’re interested in carbon atoms that contain 6 protons and 8 neutrons (=14), and we know how fast they’ll change or “decay”, which basically means they transform into something else. When we find a dead thing, we can measure the amount of carbon 14 left, and have an idea of how long it’s been changing.
You see, when a Carbon atom and oxygen atom love each other very much, they make a special bond that tells scientists how long they have been together.
Carbon is the primary ingredient for all life on Earth. It forms key molecules like protein and DNA. Plants use it for photosynthesis. It also facilitates energy storage in the form of carbohydrates and lipids. Carbon makes up approximately 50% of all biomass on Earth.
All living beings are constantly exchanging carbon atoms with the environment. Once they die, this cycle stops and all carbon atoms in the body remain where they are.
Now, there is one special kind of carbon atom called radiocarbon, or carbon-14. This atom is radioactive, and is constantly decaying. We know the rate at which it decays (50% in about 5,730 years, also known as its half-life).
Say the ratio of carbon-14 to regular carbon in the atmosphere is 2%, which means that when a certain organism was alive, 2% of all carbon atoms in its body were carbon-14.
We can do the same measurement today, and find that after decay the number is actually 1.5%. So, doing some math we can figure out what percentage of c14 atoms have decayed from the body, and so figure out an approximate age since the decay started.
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