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.
Think of it like a teaspoon of cocoa mixed into a cake dough—after a while, the ‘ratio’ of cocoa to flour particles would be roughly the same no matter which part of the cake you sampled.
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.
Libby knew that if these figures were correct, it would mean that the atmosphere was young, so he dismissed the results as being due to experimental error!
(We are not implying dishonesty here, merely showing how powerfully the evolutionary/uniformitarian concepts of Earth history influence great scientists to mould or discard evidence which appears to contradict that viewpoint.) What about modern measurements, using advanced technology such as satellites?
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.
We’ve seen that it would have been the same as in the atmosphere at the time the specimen died. Do scientists assume that it was the same as it is now? It is well known that the industrial revolution, with its burning of huge masses of coal, etc.
It is assumed that the ratio has been constant for a very long time before the industrial revolution. (For on it hangs the whole validity of the system.) Why did W. Libby, the brilliant discoverer of this system, assume this?
Libby knew that C was entering and leaving the atmosphere (and hence the carbon cycle).
As soon as it dies, however, the C ratio gets smaller.
In other words, we have a ‘clock’ which starts ticking at the moment something dies.
Carbon-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth’s atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere.