A funny mistake by ICR and example of poor scholarship

Percy,You can read my excruciatingly painstaking attempts at explaining these concepts to bob b over at theologyonline... Update on the "argon" problem (should be helium of course)Reiners himself puts in a word at the end.If you ask me, bob is loosing his grip on reality. How old is bob, anyway? Is he suffering from some kind of dementia?

Percy,you said:

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Basically he's saying that after a short period, less than thousands of years, the He concentration within the zircon would have reached equilibrium. I didn't try to check Humphreys math about the time period, but let's say he's correct. In that case the zircons are not evidence either way for either a young or old earth.

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That's not correct. IF Humphreys' math is correct, "excess" helium is evidence of accelerated decay in the very recent past. Your "equilibrium" assumes constant decay rates. I think what Humphreys now claims is that the helium levels are far above equilibrium - therefore decay rates were much higher a few thousand years ago.But let's check his math before throwing in the towel. The devil is in the details AND in the equations...I'm nearly hopeless in math, and it's even harder when we are not shown all the equations, but just looking at what Humphreys did give us, I see this:

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Solving for tci gives us the approximate closure interval:

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tci ~= a^2 / 15 *D

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where a = radius of the zircons grains and D = diffusivityBut "a" is a measure of length, and diffusivity has the units of 1/seconds, so if you look at the units of those terms, tci (closure interval) seems to have the units of length^2 * timeI don't think we can express a time with those units. Something is missing (or added) to that equation to get to a "closure interval of dozens to thousands of years".This is where we desperately need some mathematical expertise. Maybe Joe can handle this stuff... I can't... especially with most of the equations missing or unexplained. As I nearly said in the very beginning, too bad Creationists never show (all) their work. We now have a little teaser from Humphreys, which is sufficient to raise serious questions about the units of the equations used (in my own nearly ignorant mind, at least), but we may have to wait until next summer to learn the rest.In the mean time, someone will have to pony up a little brain power, or call on Reiners again to explain diffusivity at a constant temp and rising He concentration.Notice that Humphreys' latest result clashes severely with Reiners' statement:

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Taking the approximate diffusion parameters for He diffusion in zircon from our experiments, one would predict that zircon would retain 90% of its He over 10 myr if it were held at about 165 oC (would retain more if held at lower T), or over 1.5 byr if it were held at about 100-120 C (more if held at lower T).

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This certainly seems to imply that a constant temp of 100-120 C will allow 90% retention for 1.5 byr. But Humphreys is basically accusing Reiners et al of ignoring Fick's Law (diffusion increases linearly with concentration). Clarification is required from Reiners on this point, IMHO.Any thoughts on the units of Humphreys' "closure interval", Joe? Am I missing something?

Thanks Joe, I suspected I was missing something simple like that on the units.Can you use some real life numbers to illustrate this diffusion problem? I would like to see, in simple terms, how much helium is produced in a zircon with ~1000 ppm U, what the He concentration would be at various time intevals, and what the diffusion rate would be at those concentrations at various temps.In other words, show us mathematical dimwits how to use all those fancy equations that Reiners and Zeitler and Dodson throw around.Thanks