That is, they take up less than would be expected and so they test older than they really are.Furthermore, different types of plants discriminate differently.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.The strength of the Earth's magnetic field affects the amount of cosmic rays entering the atmosphere.
The common application of such posterior reasoning shows that radiometric dating has serious problems.
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.
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.