This is a common misunderstanding the general layman has of radiocarbon dating that is important to clarify.
What makes C14 significant is that it is an unstable atom.
C14 on average emits 15.2 beta particles per minute, or 15.2 disintegrations per minute (dpm), for every gram of carbon (Warf, 213).
After one half-life (5,730 years) activity will drop to 7.6 dpm, then 3.8 dpm (Warf, 213).
There is therefore no way for additional C14 to enter the organism once dead.
This leads to an important fact: Only materials once part of the biosphere (organic) can be dated with radiocarbon (Bowman, 12), with the exception of some non-organic materials which can be dated with radiocarbon if their formation involved C14.
Knowing that C14 degrades into nitrogen at a known rate and organisms do not take in C14 once they’re dead, then it logically follows that the presence of C14 in a dead organism will decrease over time.
Therefore, by measuring the amount of C14 in an organism, it can be known how long ago it lived with high C14 remains representing a recent age and lower C14 remains representing an older age. There are in essence, two different forms of carbon dating: the original conventional methods and the more recent AMS (Accelerated Mass Spectrometry).
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source radiocarbon dating A technique for measuring the age of organic remains based on the rate of decay of carbon 14.
Because the ratio of carbon 12 to carbon 14 present in all living organisms is the same, and because the decay rate of carbon 14 is constant, the length of time that has passed since an organism has died can be calculated by comparing the ratio of carbon 12 to carbon 14 in its remains to the known ratio in living organisms. Our Living Language : In the late 1940s, American chemist Willard Libby developed a method for determining when the death of an organism had occurred.
Of the conventional dating methods there are three types; Solid Carbon Counting, Gas Counting, and Liquid Scintillation Counting. The limit for conventional carbon dating is 10 half-lives (57,300 years) (Warf, 213) or within 40,000 to 60,000 years (Taylor, 3).
After that, background radiation and cosmic rays overwhelm the miniscule amount of C14 left.
Yet, as simple and straightforward as this seems, the process of dating objects via radiocarbon is far from simple and straightforward.