Few areas of science have posed a greater challenge to Young-Earth Creationism than radiometric dating of rocks and minerals.These techniques, which have been in use for nearly a hundred years, show that rocks from the earth and moon, as well as some meteorites, are as old as 4.0 to 4.5 billion years.While such behavior is more typical in polycrystals where grain boundary diffusion becomes rate controlling at lower temperatures, there is apparently some structural factor in these monocrystals that promotes low temperature diffusion.
presents diffusion rates for helium in the Fenton Hill zircons over a range of temperatures. The diffusion rates are plotted on semilog axes against the reciprocal of the temperature in degrees Kelvin.The result is a line with a negative slope, which is typical of the Arrhenius Law behavior of a thermally activated process.These techniques can also be applied to other minerals such as titanate and apatite.Farley and Reiners and have developed the sophisticated laboratory equipment needed to accurately analyze microscopic crystals for the different isotopes of concern.The ratios of uranium and thorium to the corresponding daughter product lead isotopes can be used to date the time of formation of the crystal, based on the known half-lives of the original uranium and thorium isotopes.
In theory, the helium contents can also be used for dating the crystals, but generally are not because at elevated temperatures the helium will rapidly diffuse out. Kenneth Farley of the California Institute of Technology and Dr.Most of the radiogenic helium is still present in the zircon crystals.If the crystals were really 1.5 billion years old the helium should have all diffused out into the surrounding mineral formations. and I will not repeat most of those issues here, beyond mentioning that there are some serious questions as to how RATE calculated the ratios of theoretical to actual residual helium contents in the zircons Any valid scientific theory must have predictive power.Thus, the crystals cannot really be 1.5 billion years old rather they are only a few thousand years old. The RATE research includes some limited analyses of helium contents of some zircon crystals, some diffusion rate measurements and calculations to support their claims about the short time of the diffusion process. The authors of the RATE zircon-helium study claim that their primary thesis, that the earth is only 6000 years old, is vindicated by their calculations of the expected residual helium levels in the Fenton Hill zircon crystals.They claim that their "theory" has predictive power because they can use it to correctly calculate the remaining helium levels in zircons from various depths (and temperatures) in the well.That observation is clearly at odds with the belief that world is only around 6000 years old.