The relatively short-lived C taken into organic matter is also slightly variable. However, under about 20,000 years the results can be compared with dendrochronology, based on tree rings.
Libby knew that C was entering and leaving the atmosphere (and hence the carbon cycle).Because Libby believed that the Earth was millions of years old, he assumed that there had been plenty of time for the system to be in C was entering the atmosphere as fast as it was leaving—calculations show that this should take place in about 30,000 years, and of course the Earth was much older than that, said the geologists.In other words, we have a ‘clock’ which starts ticking at the moment something dies.Obviously this only works for things which once contained carbon—it can’t be used to date rocks and minerals, for example. We obviously need to know this to be able to work out at what point the ‘clock’ began to tick.The method was developed by Willard Libby and his colleagues at the University of Chicago in 1949.
In 1960, he was awarded the Nobel Prize in Chemistry for this work.
Carbon-14 dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50,000 years old.
It is used in dating things such as bone, cloth, wood and plant fibers that were created in the relatively recent past by human activities.
The fact that the N doesn’t matter in a living thing—because it is constantly exchanging carbon with its surroundings, the ‘mixture’ will be the same as in the atmosphere and in all living things.
As soon as it dies, however, the C ratio gets smaller.
In other words, the further you go back, the more you have to shrink the radiocarbon dates to make them fit the facts.