There are numerous arguments between even those who do such dating about the dates derived by such means. While the decay of radioctive substances at certain specific rates is well established scientifically, the ability of such methods to date long buried items which have been subjected to many environmental pressures is not. Further, the only which we have been able to verify by external evidence - carbon-14 dating (which is accurate only within the last 50,000 years at most) had to be calibrated for some 20% error by historical evidence.