With our focus on one particular form of radiometric dating—carbon dating—we will see that carbon dating strongly supports a young earth.
Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.
Organisms at the base of the food chain that photosynthesize – for example, plants and algae – use the carbon in Earth’s atmosphere.
This process causes a proton to be displaced by a neutron, effectively turning atoms of Nitrogen it into an isotope of carbon – known as”radiocarbon”.
It is naturally radioactive and unstable, and will therefore spontaneously decay back into N-14 over a period of time.
Aboveground nuclear testing almost doubled the amount of carbon-14 in the atmosphere. The black arrow shows when the Partial Test Ban Treaty was enacted that banned aboveground nuclear tests. A special kind of radiocarbon dating: Bomb radiocarbon dating.
As we mentioned above, the carbon-14 to carbon-12 ratio in the atmosphere remains nearly constant.
Before we get into the details of how radiometric dating methods are used, we need to review some preliminary concepts from chemistry.
Recall that atoms are the basic building blocks of matter.
The unstable carbon-14 gradually decays to carbon-12 at a steady rate. Scientists measure the ratio of carbon isotopes to be able to estimate how far back in time a biological sample was active or alive.
This plot shows the level of carbon-14 in the atmosphere as measured in New Zealand (red) and Austria (green), representing the Southern and Northern Hemispheres, respectively.
It’s not absolutely constant due to several variables that affect the levels of cosmic rays reaching the atmosphere, such as the fluctuating strength of the Earth’s magnetic field, solar cycles that influence the amount of cosmic rays entering the solar system, climatic changes and human activities.