Carbon dating half lives
After all, we should be able to estimate how long ago a creature lived based on how much radiocarbon is left in its body. Radiocarbon (carbon-14) is a very unstable element that quickly changes into nitrogen.
Half the original quantity of carbon-14 will decay back to the stable element nitrogen-14 after only 5,730 years.
Since the atmosphere is composed of about 78 percent nitrogen,2 a lot of radiocarbon atoms are produced—in total about 16.5 lbs. These rapidly combine with oxygen atoms (the second most abundant element in the atmosphere, at 21 percent) to form carbon dioxide (CO This carbon dioxide, now radioactive with carbon-14, is otherwise chemically indistinguishable from the normal carbon dioxide in the atmosphere, which is slightly lighter because it contains normal carbon-12.
Radioactive and non-radioactive carbon dioxide mix throughout the atmosphere, and dissolve in the oceans.
The most well-known of all the radiometric dating methods is radiocarbon dating.
Although many people think radiocarbon is used to date rocks, it is limited to dating things that contain carbon and were once alive (fossils).
Knowing the number of atoms that decayed in our sample over a month, we can calculate the radiocarbon decay rate.
With time, those sand grains fell to the bottom bowl, so the new number represents the carbon-14 atoms left in the mammoth skull when we found it.
Let’s suppose we find a mammoth’s skull, and we want to date it to determine how long ago it lived.
We can measure in the laboratory how many carbon-14 atoms are still in the skull.
Through photosynthesis carbon dioxide enters plants and algae, bringing radiocarbon into the food chain.
Radiocarbon then enters animals as they consume the plants (figure 2).
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After plants and animals perish, however, they no longer replace molecules damaged by radioactive decay.