The calculation uses 8, the mean-life derived from Libby's half-life of 5, years, not 8, the mean-life derived from the more accurate modern value of 5, years. This cylinder was inserted into the counter in such a way that the counting wire was inside the sample cylinder, in order that there should be no material between the sample and the wire. However, if we could measure the amount of Carbon in the atmosphere when they lived, we would be living during the time and there would be no reason for dating. Because of the short length of the carbon half-life, carbon dating is only accurate for items that are thousands to tens of thousands of years old. These factors affect all trees in an area, so examining tree-ring sequences from old wood allows the identification of overlapping sequences. Carbon 14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms.
Scientists have calculated that the amount Carbon in the atmosphere would become stable after 30, years from the beginning of the reaction.
How do geologists use carbon dating to find the age of rocks?
Reviews of Geophysics. Can this be assumed to be correct? Peers to Contact. A much larger effect comes from above-ground nuclear testing, which released large numbers of neutrons and created 14 C. Other materials can present the same problem: