Carbon dating or updating hosts with lotus notes
So in the real world, looking at a sample like say a bone dug up by an archaeologist, how do we know how much carbon 14 we started with? This process is constantly occurring, and has been for a very long time, so there is a fairly constant ratio of carbon 14 atoms to carbon 12 atoms in the atmosphere.
Now living plants 'breathe' CO indiscriminately (they don't care about isotopes one way or the other), and so (while they are living) they have the same ratio of carbon 14 in them as the atmosphere.
Radiocarbon dating is one of the most widely used scientific dating methods in archaeology and environmental science.
Voila, now you can tell how old a sample of organic matter is.
And given the fact that the ratio of carbon 14 to carbon 12 in living organisms is approximately 1 : 1.35x10 In actually measuring these quantities, we take advantage of the fact that the rate of decay (how many radioactive emissions occur per unit time) is dependent on how many atoms there are in a sample (this criteria leads to an exponential decay rate).
We have devices to measure the radioactivity of a sample, and the ratio described above translates into a rate of 15.6 decays/min per gram of carbon in a living sample.
Some notes: 1) Obviously, this technique only works for dead organic material.
2) This technique is best for dating items which died between on the order of 1000 to on the order of 1,000,000 years ago.
Since physics can't predict exactly when a given atom will decay, we rely on statistical methods in dealing with radioactivity, and while this is an excellent method for a bazillion atoms, it fails when we don't have good sample sizes.