Carbon dating explained
However it is possible, when dating very old rocks for instance, to use longer lived isotopes for dating on a longer time scale.
3) The assumption we based this on (that the ratio of carbon 14 in the atmosphere and thus in living organisms is constant) is a decent one for ballpark figures, but this method will not be able to give results accurate to, say, a couple of minutes.
Where t is the age of the fossil (or the date of death) and ln() is the natural logarithm function.
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).When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death.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.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.
When finding the age of an organic organism we need to consider the half-life of carbon 14 as well as the rate of decay, which is –0.693.