Cyclotron sometimes used carbon dating
However, there is strong evidence which suggests that radioactive decay may have been greatly accelerated in the unobservable past.
We must also assume that the ratio of C-12 to C-14 in the atmosphere has remained constant throughout the unobservable past (so we can know what the ratio was at the time of the specimen's death).
Plants and animals naturally incorporate both the abundant C-12 isotope and the much rarer radiocarbon isotope into their tissues in about the same proportions as the two occur in the atmosphere during their lifetimes.
When a creature dies, it ceases to consume more radiocarbon while the C-14 already in its body continues to decay back into nitrogen.
It is naturally unstable and so it will spontaneously decay back into N-14 after a period of time.
It takes about 5,730 years for half of a sample of radiocarbon to decay back into nitrogen.
This man-made fluctuation wasn't a natural occurrence, but it demonstrates the fact that fluctuation is possible and that a period of natural upheaval upon the earth could greatly affect the ratio.
Volcanoes spew out CO which could just as effectively decrease the ratio.
The new isotope is called "radiocarbon" because it is radioactive, though it is not dangerous.
Specimens which lived and died during a period of intense volcanism would appear older than they really are if they were dated using this technique.
The ratio can further be affected by C-14 production rates in the atmosphere, which in turn is affected by the amount of cosmic rays penetrating the earth's atmosphere.
And yet we know that "radiocarbon is forming 28-37% faster than it is decaying," which means it hasn't yet reached equilibrium, which means the ratio is higher today than it was in the unobservable past.
We also know that the ratio decreased during the industrial revolution due to the dramatic increase of CO produced by factories.
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature.