Posted by bistiza on 9/10/2013 5:11:00 PM (view original):
Here, BL, just so you can't say I didn't provide facts, I'll give you an example of how radiocarbon dating is not correct because it is based upon assumptions which aren't always true.
Here you go:
A very common rock that contains U-238 is granite. If we look at some of the very small zircon crystals in granite, we can accurately measure how much U-238 and Pb-206 the crystal contains. In order to calculate the age of the rock, we need three other pieces of information.
First, we need to know how fast the U-238 turns into Pb-206. The half-life gives us this value, provided the half-life has never altered during the lifetime of the zircon crystal.
Second, we need to know how much Pb-206 there was in the original rock. This is clearly impossible. It is usually assumed, without justification, that the original quantity of Pb-206 in the rock was zero
Third, we need to be sure that no lead compounds have been added to or taken away from the rock. Given that lead compounds are fairly soluble in water, this is something that we cannot be very sure of.
Using the above assumptions, it is calculated that the zircon crystals have an age of about 1.5 billion years.
The radioactive decay process above can be seen to produce 8 alpha-particles for each one atom of U-238. Each alpha-particle could gain new electrons and become an atom of helium. The rate of diffusion of helium from a zircon crustal can be measured. It turns out that this rate of diffusion of helium is compatible with the crystals being about 5,000 years old, not 1.5 billion years old. Although assumptions 2 and 3 are not provable, they actually seem very likely in this particular example. Therefore, it seems that the first assumption must be wrong. Remember these experimenters are highly skilled. It is therefore unlikely that the laboratory technicians have made a mistake in their measurements of U-238 or Pb-206. The only possible conclusion, therefore, is that the half-life of U-238 has not been constant throughout the lifetime of the granite and its zircon crystals.
Helium diffusion rates? One study, full of errors, done on one group of rocks from one test well in New Mexico doesn't disprove nuclear decay rates.
The experimenters did make mistakes. Lots of them.
The biggest mistake they made was assuming a constant temperature when the actual temperature varied significantly.
In reviewing the two main RATE reports (Helium Diffusion Age of 6,000 Years Supports Accelerated Nuclear Decay and Helium Diffusion Rates Support Accelerated Nuclear Decay), I discovered an error in the data analysis. The RATE team used a prior estimate by Robert Gentry for the total amount of helium produced from nuclear decay. However, Gentry’s own calculation was off by a factor of over three. Once this error was corrected, the fraction of helium remaining in the zircon samples dropped considerably
The RATE argument is based upon the claim that there is still a lot of helium in these zircons. However, according to the corrected calculations these zircons actually contain far less helium than the RATE researchers originally thought, which weakens their case.
Next, I corrected errors in the geometry and boundary conditions of their diffusion model. The RATE team used an effective radius that was too large (30 µm versus 20 µm). Furthermore, their model included a second mineral called biotite, surrounding a zircon core. Although zircons are often embedded in larger flakes of biotite, they treated this second mineral as if it had the same material properties as zircon despite the fact that their own data showed that the diffusivity of helium in biotite was orders of magnitude higher. With such a high diffusivity, a biotite envelope would offer little resistance to a migrating helium atom once it left the zircon crystal.
Neither of those errors is as significant as the error in the temperature calculation or as significant as the kinetic error:
Second, the RATE researchers used a simple kinetic model in their diffusion study. This type of model ignores the possibility that helium atoms behave differently depending upon their location in the crystal, with atoms in the vicinity of defects moving more readily than those that are in the bulk crystal. Instead, I incorporated amulti-domain diffusion model which takes this effect into account. This type of model has been used by several leading scientists in the noble gas thermochronology field (see for example: Reiners and Farley, 1999, pp. 3850-53; Reiners et al., 2004, pp. 1872-74; Shuster, et al., 2003, pp. 28-29; Shuster, et al., 2005, pp. 669-70).
And the conclusion:
The old-earth model matches the revised measurements better than the young-earth model. The RATE team claimed that essentially no helium would be left in these zircons if they were more than a few thousand years old. However, by direct computation, I have demonstrated otherwise. The helium content and the 1.5 billion year radiometric age of these zircons are in agreement. Since no anomaly exists, there is no scientific need to postulate the existence of exotic physics, like accelerated nuclear decay, to explain the phenomenon.
Not only does this result deprive the accelerated nuclear decay hypothesis of its best case, it actually counts as evidence against accelerated nuclear decay. Two independent clocks (nuclear decay and helium diffusion) are now in agreement on the billion-year-age of these rocks. Consequently, the notion of accelerating natural processes becomes an untenable scientific position, and one must read nature’s clocks at face value. Obviously RTB and young-earth creationism remain at odds. However, the RATE group posited a model and subjected it to scientific testing. And for that they are to be commended.
Your "facts" aren't facts. Nice try though.