The earth was divided up into layers. The shirt you're wearing, the carbon dioxide you inhale and the animals and plants you eat are all formed mostly of Carbon Response: I asked several people who know about this field. Radioactive carbon thus was visualized as gaining entrance wherever atmospheric carbon dioxide enters—into land plants by photosynthesis, into animals that feed on the plants, into marine and fresh waters as a dissolved component, and from there into aquatic plants and animals.
Organisms capture a certain amount of carbon from the atmosphere when they are alive. They use tree rings as the calibration standard. Calibration curves have been constructed using dendrochronological data tree-ring measurements of bristlecone pines as old as 8, years ; periglacial varve, or annual lake sediment, data see above ; and, in archaeological research, certain materials of historically established ages. That carbon dating deemed the moss to have been frozen for over 1, years. After showing the essential uniformity of carbon in living material, Libby sought to answer the second question by measuring the radiocarbon level in organic samples dated historically—materials as old as 5, years from sources such as Egyptian tombs.