Carbon has different isotopes, which are usually not radioactive.
Plants take up atmospheric carbon dioxide by photosynthesis, and are eaten by animals, so every living thing is constantly exchanging carbon-14 with its environment as long as it lives. In 1958 Hessel de Vries showed that the concentration of carbon-14 in the atmosphere varies with time and locality.
Signals of this kind are often used by chemists studying natural environments.
A hydrocarbon found in beach sediments, for example, might derive from an oil spill or from waxes produced by plants.
People wonder how millions of years could be squeezed into the biblical account of history. Christians, by definition, take the statements of Jesus Christ seriously.
Clearly, such huge time periods cannot be fitted into the Bible without compromising what the Bible says about the goodness of God and the origin of sin, death and suffering—the reason Jesus came into the world (See Six Days? He said, This only makes sense with a time-line beginning with the creation week thousands of years ago.
Carbon-14 is most abundant in atmospheric carbon dioxide because it is constantly being produced by collisions between nitrogen atoms and cosmic rays at the upper limits of the atmosphere.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
So, we have a “clock” which starts ticking the moment something dies.
Isotopes participate in the same chemical reactions but often at differing rates.
When isotopes are to be designated specifically, the chemical symbol is expanded to identify the mass (for example, C is not stable.