Booboo writes:
The problem is, the magnetic field is decaying around the earth. The earth is covered in a magnetic field, which is STEADILY losing its strength by 1/2 every 1400 years. There are no magnetic reversals--there are only areas of stronger and weaker magnetism. So, if there are no reversals, then we know that the magnetic field has been shrinking at a measurably-stable rate. So, by the half-life of the magnetic field, the magnetic field would have been 320% stronger around 4500 years ago.
First, the evidence says that the earth's magnetic field has modestly fluctuated over the past tens of thousands of years, thereby causing fluctuations in the levels of atmopheric C14, but nothing anywhere near the hundreds of percent you claim. C14 dating is corrected for these fluctuations, which never have an impact greater than about 10% anyway.
Second, though there has not been a reversal of the earth's magnetic field in the time period covered by C14 dating (the last 50,000 years or so), reversals of the earth's magnetic field are copiously recorded in the sea floor produced at mid-oceanic ridges. I can't remember the exact figure, but I think I'm at least in the right order of magnitude if I say that magnetic field reversals occur on average every half million years or so.
Third, C14 dating has been calibrated very precisely using tree ring data back about 11,000 years. For example, see
How tree rings are used as a radiocarbon record at the
Waikato Radiocarbon Dating Laboratory.
--Percy