The half-life of an isotope like C14 is the time it takes for half of it to decay away: in C14, every 5,730 years, half of it is gone.
So detecting the subtle change in the ratio of normal to naturally occurring radioactive carbon over just a few years is incredibly hard.
But Jonas Frisén of the Karolinska Institute in Stockholm, Sweden, says it can be done if one takes advantage of the signal left by nuclear testing, which spewed high levels of carbon-14 into the air during the Cold War.
The rate of decay depends upon the number of atoms you have.
This means that as more of these atoms decay you have a lower rate of radioactive decay. If you roll a one, then that object decays and turns into something else.
Carbon dating looks at the ratio of radioactive carbon, which is naturally present at low levels in the atmosphere and food, to normal carbon within an organism.