It's difficult to tell what is being asked here.This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form.Unhappily for many creationists who criticize evolution, they fail to realize that carbon 14 dating is only rarely used in the context of fossils and mostly used in Archeology.This is because the half-life is just over 5,700 years, which makes it useless for dating the vast majority of rocks as the furthest back in time it will work fairly accurately is about 60,000 years.C (carbon-14) in the upper atmosphere as a result of bombardment by neutrons in so-called cosmic rays: high-energy particles bombarding the Earth's atmosphere from outer space. On formation, the newly-born carbon atom quickly oxidizes to form a molecule of carbon dioxide (COC being produced annually is more or less constant, whereas the quantity being destroyed is proportional to the quantity that exists, it can be shown that the quantity in the atmosphere at any given time will be more or less constant: the processes of production and decay of C, which need not concern us in this article.The terrestrial carbon cycle is fairly simple: plants get their carbon from the atmosphere via the process of photosynthesis; herbivores get their carbon from plants, and carnivores from the herbivores.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
What methods do they use and how do these methods work?
In this article, we will examine the methods by which scientists use radioactivity to determine the age of objects, most notably carbon-14 dating.
So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.