ecently an anti-creationist geochemist, a part-time instructor at the University of Kentucky named Kevin Henke[1], posted on the Internet a 25,000-word rejection[2] of scientific evidence that the world is only about 6,000 years old, the helium-leak age of zircons (radioactive crystals) from deep underground. In politics, his procedure would be called “mud-slinging,” which in this case tries to bury truth under a mountain of minutiae. I normally don’t reply to Internet posts from skeptics because I want them to try to publish their criticisms in peer-reviewed scientific journals, the proper place to carry out scientific debates. However, in this case I want to take the opportunity to share updated information about our research which will appear later this year in the RATE[3] “results” book[4] and in the accompanying book for laymen.[5] I also plan to submit technical details of this reply to a peer-reviewed scientific journal, the Creation Research Society Quarterly (CRSQ). If Henke chooses to sling yet more mud, let him try to do so in a scientific journal. The RATE helium research has been peer-reviewed and published in several different scientific venues. Critics like Henke must gird up their loins and undergo the same kind of scientific discipline—if they want people to take them seriously. If they refuse to do that, I plan not to reply to them further.
First I’ll point out what it is that the skeptics are trying to obscure. Then I will go through Henke’s summary of his criticisms point-by-point. Amazingly, in his entire fifty pages he specifies only two real errors of mine: (a) I misspelled a name in one of my references, and (b) I was not precise enough in my geological description of a rock formation. The only other possibly significant items are (1) a quibble about how much helium should have been deposited in the zircons, and (2) a minor mistake I made (which Henke failed to discover) in summarizing our results. Last I’ll analyze Henke’s tactics and try to plumb his motives.
The Evidence Henke Wants to Hide
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Figure 1. Microscopic zircons. Photo by R. V. Gentry. |
I’ll try to keep this simple, so for the scientific details, please consult the two most relevant publications, which are also archived on the Internet. I’ll call them ICC 2003[6] and CRSQ 2004.[7] Decades ago, Robert Gentry analyzed tiny zircon (zirconium silicate) crystals recovered from hot Precambrian (over 545 million years old according to the geologic timescale) “basement” rock in New Mexico.[8] Figure 1 shows some of the zircons he analyzed, between 50 and 75 microns (millionths of a meter) long.
Enough of the uranium in the zircons had decayed to lead to give them a radioisotope (radioactive element) age of “1.5 billion” years. But Gentry found that up to 58% of the helium that the nuclear decay would deposit in the zircons was still in them. This was surprising, because helium diffuses (leaks) rapidly out of most minerals.
Not knowing how fast helium leaks from zircon, I estimated what the leak rates would be when we measured them. In essence (of course the math is more complicated), all I did to get the estimates was to divide the amount of helium lost from the crystal by the time (assumed by each model) during which it had been lost. That gives us the leak rates for each of the two models. The “1.5 billion year” model has rates over 100,000 times slower than the “6,000 year” model, because the former has to retain the helium for a much longer time. Then in the year 2000, the RATE group published the estimates as numerical predictions for those two models.[9]
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Figure 2. Model-predicted (red and magenta diamonds) and measured (blue dots) helium leak rates of zircons. The data fit the 6,000-year prediction very well. |
Figure 2 shows the predictions as red and magenta diamond symbols. The bottom axis shows the temperature (in °C) of each sample in situ, that is, while it was in the granitic rock unit. (I have reversed the direction of temperature from what is traditional in such “Arrhenius” plots.) The vertical axis shows “diffusivity”, which is a measure of how fast helium leaks from a material. The vertical axis is tremendously compressed, representing a factor of one trillion increase in leakage rates from bottom to top. The black numbers under the diamonds are the percentages of helium retained in each sample.
The red and magenta vertical lines through the diamonds are the “two-sigma error bars”. These statistical error bounds were implicit in our reports, but we had not shown them explicitly in our graphs before now. The bars essentially show the 95% confidence limits I estimate for the accuracy of the predictions. The forthcoming RATE “results” book gives details on how I estimated the error bounds.
In 2001 we commissioned one of the world’s most respected experimenters in this field to measure the diffusivity of helium in the same-size zircons from the same borehole in the same rock formation. We used an existing mining company as an intermediary, and we asked it to not tell the experimenter about us or our goals. The experimenter, being a uniformitarian (believer in long ages) and not having read our prediction, had no idea what results we were hoping for. It was a truly “blind” experiment, and we (the RATE team) were eagerly awaiting the data.
Figure 2 shows the experimental results as blue dots with blue “2-sigma error bars” going vertically through them. If we repeated the experiments hundreds of times, we estimate the data points would remain within the caps on the error bars over 95% of the time. Again, the RATE “results” book (which has now passed through extensive peer review and is being proofread) will have the details on the error estimates.
To our great delight, the data fell right on the “6,000 year” prediction! This alignment validates the young-age model even for readers who are not experts in this field, because the probability of such a lineup by accident is small. The data resoundingly reject the “1.5 billion year” model. The experimenter, whose name is in one of our articles, stands by his data, even though as a uniformitarian he does not like our interpretation of them. (Even after several years, he has not offered an alternative interpretation.)
This sequence of events places the burden of disproof on the critics, because they must explain how, if there is no truth to our model, the data “accidentally by sheer coincidence just happened by blind chance” to fall right on the predictions of our model.
Rebutting Henke’s Charges
In his abstract, Henke summarized his fifteen principal charges. I’ll number them and quote them, in bold maroon text. I’ll answer each charge with no more detail than necessary to dispose of it.1. “invoking groundless miracles to explain away U/Pb dates on zircons”
This means he does not find RATE’s “accelerated nuclear decay” hypothesis to his taste. But, as the ancient Romans said, “There’s no disputing about taste.” In other words, Henke’s personal preference in theories means exactly nothing to the rest of us. Moreover, it is beside the point. The main subject of my articles is the experimental data, and I offered only a few paragraphs about our hypothesis simply to explain what we think really happened. If Henke doesn’t like our explanation, let him offer his own. I’d be very interested to hear (preferably in a peer-reviewed scientific journal) how he thinks the zircons suffered 1.5 billion years worth of nuclear decay but only 6,000 years worth of helium losses!2. “misidentifying samples as originating from the Jemez Granodiorite”
Henke means that I didn’t specify that the top 1000 meters or so of the Precambrian granitic rock unit in question might contain gneiss or schist instead of granodiorite. What he doesn’t realize is that “Jemez Granodiorite” is a name I invented (since the literature had not previously named it) to apply to the whole unit from about 700 meters depth down to below 4,310 meters. Our co-author John Baumgardner, a geophysicist, saw large portions of the GT-2 core at Los Alamos and picked our samples from it. He says:
Yes, there are occasional veins of material other than the coarse-grained granodiorite that forms the vast majority of the core. In making the selections I made of what samples to use, I purposely avoided these occasional veins. In fact I tried to select sections of the core well removed from such veins. So at least from my vantage point, the samples of core we used for the helium diffusion measurements were indeed coarse-grained granodiorite, not gneiss.
The important point is that, regardless of the name we put on the rock unit, the zircons throughout it have been measured to contain essentially the same amounts and ratios of lead isotopes,[10] and therefore have undergone the same amount of nuclear decay. The uranium, helium, and lead levels in our samples are perfectly consistent with the corresponding levels Gentry reported for his. The effect of variation from sample to sample is probably smaller than the 2-sigma error bars around our prediction. So here Henke is making a distinction without a difference.3. “performing helium analyses on impure biotite separations”
That, of course, is a gratuitous slap at the quality of the ICR geological lab, which did that particular separation. In the lab’s defense, I would point out that their separation of biotite from another rock unit, the Beartooth Gneiss, was excellent. I’m judging that by the helium data from that unit in Appendix B of ICC 2003, which our experimenter called “remarkably linear”. Henke’s allegation is also unproven. Different localities, having different minerals, offer different degrees of difficulty with separation. The only way to gauge quality in this case would be to have another lab work on the same rocks and try to get a yet higher purity. I challenge Henke to procure his own samples of the same core from Los Alamos and to try to do a better separation himself!
However, haggling about the exact diffusivity of biotite is irrelevant, because as we pointed out in numerous parts of our articles, it is clear that that zircon has a diffusivity an order of magnitude lower than that of biotite in the low-temperature range of interest to us. That makes the diffusivity of zircon much more important to know accurately. Henke’s attack here is a good example of what I meant by “mud-slinging”—nasty, irrelevant, and intended to distract the readers from the important issues.Source