ericmurphy
Posts: 2460
Joined: Oct. 2005
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| Quote (JonF @ June 15 2006,17:45) | | Well, to be fair, as far as we know if we knew all the relevant properties as functions of the relevant variables and if we knew the values of those variables during the "lifetime" of the zircons then we could calculate the age of the zircons from helium diffusion alone. However, it's essentially certain that the aamount of helium left today is not a single-valued function of age; there are many different ages which (when combined with other environmental scenarios) would result in the same amount of helium present today. So we do need more information than measurements of helium amounts, but I think everyone acknowledges that. |
Except for Dave. He doesn't acknowledge that at all. Dave seems to believe that Humphreys is not only justified in assuming that He diffusion has been constant during the last 6,000 years, but that he actually knows what that rate has been for the last 6,000 years. Since Humphreys knows neither one of those things, he simply cannot make any estimates of the age of his zircons, and therefore cannot make any claims as to the age of the earth.
| Quote | | The argument is over whether or not Humphreys' assertions and arm-waving are sufficient evidence for knowing all the relevant values and discarding hundreds of thousands, possibly millions, of independently obtained and cross-correlated and consistent evidence. I don't think so. |
And so far it's been pretty much established that Humphreys has not eliminated every possible source of error in his calculations, because he simply doesn't have enough data on the thermal history of the rocks, nor on the possible contamination from other sources of helium in the vicinity. This is why, Dave, Humphreys' results simply don't pass the smell test.
Add in that his results are completely contradicted by every other result out there, and it's no wonder he hasn't made much of a splash in the field of radiometric dating.
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2006 MVD award for most dogged defense of scientific sanity
"Atheism is a religion the same way NOT collecting stamps is a hobby." —Scott Adams
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