Carbon dating moon rocks
The strength of the Earth's magnetic field affects the amount of cosmic rays entering the atmosphere.
A stronger magnetic field deflects more cosmic rays away from the Earth.
However, even with such historical calibration, archaeologists do not regard C produced and therefore dating the system.
Obviously, this works only for things which were once living.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.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.