This is the “half-life.” So, in two half-lives, or 11,460 years, only one-quarter of that in living organisms at present, then it has a theoretical age of 11,460 years.Anything over about 50,000 years old, should theoretically have no detectable C.It then takes the same amount of time for half the remaining radioactive atoms to decay, and the same amount of time for half of those remaining radioactive atoms to decay, and so on. The amount of time it takes for one-half of a sample to decay is called the half-life of the isotope, and it’s given the symbol: It’s important to realize that the half-life decay of radioactive isotopes is not linear.For example, you can’t find the remaining amount of an isotope as 7.5 half-lives by finding the midpoint between 7 and 8 half-lives.

Knowing about half-lives is important because it enables you to determine when a sample of radioactive material is safe to handle.

So, we have a “clock” which starts ticking the moment something dies.

Obviously, this works only for things which were once living.

It cannot be used to date volcanic rocks, for example.

The rate of decay of N in 5,730 years (plus or minus 40 years).