This also has to be corrected for. Second, the ratio of C in the atmosphere at that time to be estimated, and so partial calibration of the “clock” is possible.Accordingly, carbon dating carefully applied to items from historical times can be useful.This is the “half-life.” So, in two half-lives, or 11,460 years, only one-quarter of that in living organisms at present, then it has a theoretical age of 11,460 years.Anything over about 50,000 years old, should theoretically have no detectable C.However, even with such historical calibration, archaeologists do not regard C produced and therefore dating the system.The amount of cosmic rays reaching the Earth varies with the sun's activity, and with the Earth's passage through magnetic clouds as the solar system travels around the Milky Way galaxy.Overall, the energy of the Earth's magnetic field has been decreasing, so more C is being produced now than in the past.This will make old things look older than they really are.
There are various other radiometric dating methods used today to give ages of millions or billions of years for rocks.Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.These techniques are applied to igneous rocks, and are normally seen as giving the time since solidification.
The isotope concentrations can be measured very accurately, but isotope concentrations are not dates.
Also, the Genesis flood would have greatly upset the carbon balance.