Carbon dating or
Carbon 14 dating is not great for dating things like a year old because if much less than 1 half-life has passed, barely any of the carbon 14 has decayed, and it is difficult to measure the difference in rates and know with certainty the time involved.On the other hand, if tons of half-lives have passed, there is almost none of the sample carbon 14 left, and it is really hard to measure accurately how much is left.It is unstable, and scientists know that it radioactively decays by electron emission to Nitrogen 14, with a half life of 5730 years.This means that given a statistically large sample of carbon 14, we know that if we sit it in a box, go away, and come back in 5730 years, half of it will still be carbon 14, and the other half will have decayed.
The net effect of this is that all living organisms have the same radiocarbon to stable carbon ratio as the atmosphere.
If it weren’t for the amiability of carbon, simple organic matter couldn’t have evolved to achieve the extraordinary, inscrutable complexity it now boasts: the complexity to develop a system to sense, to breathe, to digest, to excrete and in a lean, hairless primate, even a system to think.
Measuring the quantity of this radioactive carbon in organic matter allows us to determine its age; the method of doing so is called radioactive carbon dating or, simply, carbon dating. Carbon has a twin brother that only a few know about.
Animals, including humans, consume plants a lot (and animals that consume plants), and thus they also tend to have the same ratio of carbon 14 to carbon 12 atoms.
This equilibrium persists in living organisms as long as they continue living, but when they die, they no longer 'breathe' or eat new 14 carbon isotopes Now it's fairly simple to determine how many total carbon atoms should be in a sample given its weight and chemical makeup.