Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.Carbon-14 has a half-life of 5,730 ± 40 years—, half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years.
One is for potentially dating fossils (once-living things) using carbon-14 dating, and the other is for dating rocks and the age of the earth using uranium, potassium and other radioactive atoms.
The atomic number corresponds to the number of protons in an atom.
All organisms have a certain amount of 14C present in their bodies – it is absorbed out of the atmosphere by plants during the process of photosynthesis, and transferred to animals when the plants are eaten.
While alive, organisms experience a balance of 14C intake and dissipation.
The method is widely used by Pleistocene geologists, anthropologists, archaeologists, and investigators in related fields.