Many people assume that rocks are dated at “millions of years” based on radiocarbon (carbon-14) dating. The most well-known of all the radiometric dating methods is radiocarbon dating.
Carbon-14 can yield dates of only “thousands of years” before it all breaks down.
When animals eat the plants, the carbon-14 enters their bodies.
The carbon-14 in their bodies breaks down to nitrogen-14 and escapes at the same rate as new carbon-14 is added. CARBON-14 IS DEPLETED (Figure 1c): When an animal dies the carbon-14 continues to break down to nitrogen-14 and escapes, while no new carbon-14 is added.
Radiocarbon then enters animals as they consume the plants (Figure 1b).
So even we humans are radioactive because of trace amounts of radiocarbon in our bodies.
After plants and animals perish, however, they no longer replace molecules damaged by radiocarbon decay.Since each beta particle represents one decayed carbon-14 atom, we know how many carbon-14 atoms decay during a month.Chemists have already determined how many atoms are in a given mass of each element, such as carbon.4 So if we weigh a lump of carbon, we can calculate how many carbon atoms are in it.If we know what fraction of the carbon atoms are radioactive, we can also calculate how many radiocarbon atoms are in the lump.Knowing the number of atoms that decayed in our sample over a month, we can calculate the radiocarbon decay rate.