This is a formula which helps you to date a fossil by its carbon.
In 1960, Libby was awarded the Nobel Prize in chemistry for this work.
He demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from a series of samples for which the age was known, including an ancient Egyptian royal barge dating from 1850 BCE.
Radiocarbon dating (usually referred to simply as carbon-14 dating) is a radiometric dating method.
It uses the naturally occurring radioisotope carbon-14 (14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years old.
I can do this by working from the definition of "half-life": in the given amount of time (in this case, hours.
I do not have the decay constant but, by using the half-life information, I can find it.
Thus, if we start out with 1 gram of the parent isotope, after the passage of 1 half-life there will be 0.5 gram of the parent isotope left.
After the passage of two half-lives only 0.25 gram will remain, and after 3 half lives only 0.125 will remain etc.
After plants die or are consumed by other organisms, the incorporation of all carbon isotopes, including 14C, stops.