The following text was forwarded to me by David Plaisted on August 3, 1999. Not previously available to me, this text was Dr. Plaisted's reply to Dr. Henke's comments that appear in the previous parts of the series, which were provided by Dr. Henke.
Text is by David Plaisted, HTML formatting by Tim Thompson. I have inserted a couple of clearly marked editorial comments, for the purpose of providing references to research mentioned by Dr. Plaisted on the possibility of time variation in the speed of light and the fine structure constant.
DAP = comment by David A. Plaisted, creationist.
KRH = comment by Kevin R. Henke, geologist and advocate of radiometric dating.
See part two, provided by Kevin Henke, for the list of books & papers referenced by him in the text.
David A. Plaisted
December 29, 1998
DAP: This is an initial response to just a few of the main points of Kevin Henke's response.
DAP: In the first place, Dr. Henke did not inform me that his review and my response would be posted on talk.origins, which would only be courteous. I do plan to add some comments to the Radiometric Dating Game article eventually, however.
KRH: I'm sorry that you didn't want our correspondence publicized. Unless someone states that they don't want something circulated, I always feel free to share it. I also sent copies to Timothy Wallace. I have been corresponding with creationists for a long time and y comments always seem to get circulated. I accept that. That's why I always do my best when writing emails, because often they end up in the hands of others. For example, some of my emails with Karl Crawford went to Woodmorappe. Karl didn't ask my permission, but I didn't expect him to do this. Public airing of correspondence encourages each side to do their best. It's a good thing.
DAP: One of the key points is whether different methods agree on the Cambrian and later strata. Dr. Henke cites examples of K-Ar and Ar-Ar agreeing, but this is not significant since in my understanding they are attempting to measure the same property.
KRH: No. Not quite. Nature can cause argon to escape from a biotite, which would wreck the K/Ar date for an igneous event. However, nature can't selectively remove 40Ar more than 39Ar. The mass difference is too small. So, Ar/Ar dating may still be reliable. It's like comparing U/Pb, Pb/Pb, and Th/Pb.
DAP: Ar-Ar dating subjects a sample to a process that converts some of the K to an isotope of Ar and thus two isotopes of Ar can be compared to date the rock. It is not surprising that this would agree with K-Ar. But if I misunderstand, I'd appreciate a clarification.
KRH: K/Ar and Ar/Ar aren't measuring exactly the same thing. Dalrymple (1991, p. 111-115 discusses some of the advantages of 40Ar/39Ar over traditional K/Ar dating
DAP: I'm not primarily interested in comparisons with fission track dating, either. How about comparisions of K-Ar and Rb-Sr and U-Pb on the phanerozoic? Comparing U-Pb and Pb-Pb (or Th-Pb and Pb-Pb) might not be as interesting in this regard.
KRH: I already gave you the following example out of Young (1977):
KRH: Young (1977, p. 190f) provides an excellent example of fossil data confirming the results of Rb/Sr and K/Ar dates for the Beemerville Nepheline Syenite in New Jersey. The syenite intruded into the Ordovician Martinsburg Formation, but it does not intrude into the overlying Lower Silurian Tuscarora Formation. Cross-cutting relationships, fossil data, and the geologic time scale indicate that the syenite should be 425 to 450 million years old. Rb/Sr and K/Ar dating of the syenite yielded dates of 424 +/-20 million years, 436 +/- 41 million years, and 437 +/- 22 million years, which are reasonably consistent.
KRH: Again, there's numerous examples in Harland et al. (1990) and its references.
DAP: It's fine to cite a lot of references, but it would help me a lot more if you would mention which methods were compared, and the average percentage of disagreement, and how many dates were given, and whether all anomalies were included. That would save a lot of work on my part.
KRH: No. Like it or not, you are True.origins expert on radiometric dating. As long as your report remains posted on True.origins or any other web site, you have the RESPONSIBILITY to keep up on the literature of your opponents. Furthermore, if I summarize the literature for you, I might misquote or misrepresent it. Like it or not, you are going to have to track down Harland et al. (1990), Dalrymple (1991) and my other references and read them for yourself. I'm not going to take on your responsibilities.
DAP: I think you misunderstood my point about the meteorite dating. I didn't question whether the dates were young or old. The 4.5 billion year history of the earth was derived from an isochron involving about 5 or 6 meteorites. Can this isochron be extended to more meteorites? I saw somewhere a quotation that it cannot. Shouldn't the t.o. FAQ mention this, to be honest?
KRH: You can talk to the author of the TO FAQ about his post. Dalrymple (1991, p. 294) lists a Rb/Sr whole rock isochron with 38 chrondite meteorites. This isochron gives an age of 4.498 +/- 0.015 billion years. For reasons discussed on p. 293 and Dalrymple's references, this date probably represents the condensation and aggregation of planets in the solar nebula. In other words, here is an example where 38 meteorites are used to date the age of the Earth, NOT just 5-6. What more information? Read Dalrymple (1990, chapters 6 and 7).
DAP: Dr. Henke misunderstood my article in a few other places, as well. One example is his reference to a neutron sea, which is not at all what I was discussing. I passed these over initially, but now that this is all public, it is worth noting.
DAP: I'm not sure what the effect of neutrinos on non-radioactive elements would be. But in general, for something that is unstable, a small energy input can cause it to decay, which might have little effect on a more stable object (except to heat it a little).
KRH: For reasons discussed in Brush (1983), neutrinos, neutrons, etc. are not a serious concern for radioactive decay rates.
DAP: As for physical constants, even some secular scientists recently proposed that c was much, much larger in the past.
KRH: Who? Does the scientific community take their claims seriously? You can always find someone that will support something. Why a good chunk of the American people still trust Bill Clinton. There are Ph.D.'s that believe that the sun goes around the Earth (e.g., Gerardus Bouw). Quotations from books or articles claiming one thing or another are cheap and I don't rely on them very much. Instead of relying on 20 year old quotes from Stansfield or whomever, we should be looking at dozens of the most recent articles on radiometric dating to get a real feel for what's going on. That is, what works and what does not.
Editorial comment by Tim Thompson:DAP: In addition, there is some evidence of a change in the fine structure constant. But this is not something that concerns me much one way or the other.
See A time varying speed of light as a solution to cosmological puzzles; Andreas Albrecht & Joao Magueijo; Physical Review D 59(4) article 043516 (15 February 1999), and Cosmologies with varying light speed; John D. Barrow; Physical Review D 59(4) article 043515 (15 February 1999). Albrecht & Magueijo explore time variability of the speed of light in the very early stages of the big bang as an alternative to inflationary cosmology. Barrow does a more detailed construction of such a cosmology within general relativity. Both papers are purely theoretical. However, see Astrophysical Probes of the Constancy of the Speed of Light for a discussion of how one might go about an observational program to determine whether or not the speed of light has been time variable. Contrary to common thought, a cosmologically constant speed of light is not a basic requirement of relativity theory.
Editorial comment by Tim Thompson:
See A Search for Time Variation in the Fine Structure Constant; John K. Webb et al.; Physical Review Letters 82(5) 884-887, 1 February 1999. They argue that their observations of quasar spectra show a time variability in the fine structure constant. However, see Does the Fine Structure Constant Really Vary in Time?; Mario Livio & Massimo Stiavelli; Astrophysical Journal Letters 507 L13-L15, 1 November 1998; Livio & Stiavelli argue that the data from Webb et al. do not reliably show the purported time variability (it is a peculiarity of the new internet that Livio & Stiavelli got their response into print before the paper they were responding too; they found the preprint on the web and got their paper past the referees faster than Webb et al. were able to). Both of these papers deal with time variability over cosmological time scales. See Atomic Clocks and Time Variations of the Fine Structure Constant; John D. Prestage, Robert L. Tjoelker & Lute Malecki; Physical Review Letters 74(18): 3511-3514, 1 May 1995. An intense study at the JPL Frequency Standards Laboratory shows that any current time variability in the fine structure constant must be fractionally less than or equal to 3.7 x 10-14 per year (the paper itself is accessible as a PDF file through the JPL Technical Report Server, number 142 on the 1995 list. The fine structure constant is e2/h.bar*c where "e" is the electronic charge, "h.bar" is Planck's constant divided by 2pi and "c" is the speed of light. A time variability in the fine structure constant could be interpreted in terms of any of the 3 constituent "constants" that make it up, but the speed of light would be the most convenient from a fundamental viewpoint.
DAP: It doesn't surprise me that radiometric dates should agree sometimes. Even on dates that are much less than 600 million years. But these rocks could still be much older than fossils. What is needed are rocks that give convincing old dates (by at least 2 unrelated methods) that lie above fossils, or something of the sort. The 2 dates need to be on the same sample.
KRH: I have already given you the example from Young (1977). There's also Tucker et al. (1998) and Harland et al. (1990). Look at the literature and you'll see that consistency between different radiometric dating methods is very common
DAP: One possible scenario is that the earth is old, and some dates are valid and old. Then life appeared recently (thousands of years ago) and since then a violent catastrophe occurred with processes that in some cases mimic apparent ages and sometimes not. So you have many kinds of dates -- very old dates that are correct, anomalous dates on very old samples, old dates on phanerozoic samples that are taken as correct but really are not, cases where phanerozoic dates disagree, and very young dates on phanerozoic samples that are correct but considered to be anomalous. There are a number of processes that might make dates appear older lower down, that have nothing to do with age. So what I am interested in is information that would refute this complicated mix of 5 different kinds of dates.
KRH: Fundamentalist Creationists consider this interpretation to be anti-scriptural. Again, the evidence in Young (1977, 1982) and Strahler (1987) refutes the idea that the geologic column and life on Earth can only be a few thousand years old.
DAP: So we could even get agreement between methods, since the great majority are K-Ar dates. Then some process unrelated to age could make K-Ar dates old lower down (such as a lot of excess argon at the start which gradually dissipated with succeeding eruptions). Maybe the earth is very old and was very quiet for a long time, building up argon in the interior. The a lot of eruptions occurred in the past several thousand years, gradually releasing it. Then we might get other dating methods sometimes agreeing with K-Ar dates and sometimes not, producing a situation much like that observed today.
KRH: Look at the geochronology literature. Also see Young (1982, p. 100-103). Ar/Ar and K/Ar isochron dating could deal with the extraneous argon. Morgan (1998), Kamijo et al. (1998), Albarede (1998) and Jackson (1998, p. 169-171) place clear restraints on the degassing of the mantle, based on field data. If you want to speculate, it should be consistent with the field data in these and other sources that I mentioned in my reply to you yesterday.
DAP: So just producing many dates that agree with conventional ages proves little.
KRH: No. Consistent fossil, radiometric and magnetic data are a serious problem for creationists. Again, check Harland et al. (1990) and its references.
DAP: I realize that the problem of distinguishing true ages from false ages produced by some such scenario is difficult, but it is what I am concerned with. This is not an easy task, and just listing a bunch of references without careful analysis does not answer the question.
KRH: It's often not difficult. You're making it sound more difficult and unreliable than it really is. See Dalrymple (1984).
DAP: You criticize my quote from Stansfield, since he asserts that dates support a long history of geological evolution. But the first part of his quote mentions many discrepancies, which was my point. This does undermine the second part of his quote.
KRH: Stansfield is wrong. Period. Don't believe everything you read. Again, you have to read dozens of current literature to get a real feel of what is going on in radiometric dating. Quoting anonymous emails and 20 year old references from biologists aren't good enough.
DAP: And there are many other quotes of the same nature from other authorities about common discrepancies between methods, and the fact that anomalies are often not published or explained.
KRH: I know there are. Just look at Dickin (1995). But, again, quotes are cheap. To really understand what's going on you have to sample the recent works of many different authors. You have to follow arguments between experts on different issues and see where they go. Overall, the geologic time scale is in great shape. Yes, scientists are still making minor adjustments. However, it's clear from Strahler (1987), Dalrymple (1991), etc. that the creationists have lost.
DAP: There is another excellent and very long article by Snelling at http://www.icr.org/research/as/as-r01.htm with numerous references to the literature. I had trouble even skimming the whole thing. He explains where the excess argon may be coming from. He also mentions that some minerals have appreciable argon but no potassium, so this must be excess argon, and it must come from somewhere. He gives quite a few cases of excessively old K-Ar dates.
KRH: I'll look at Snelling's site again before I comment on it in detail.
DAP: He also mentions that excess argon can be found in defects and holes in crystals and in boundaries between regions. This can arise from argon present during cooling. I don't see how this can be detected, as (especially in holes and defects) it is largely indistinguishable from radiogenic argon.
KRH: Again, crystallographers know this. Look at Deer et al. (1972-1977) to see where the argon can hide. Young (1982, p. 99-103) also talks about argon adsorption onto mineral surfaces. Snelling's concerns are nothing new or serious. Again, K/Ar isochron dating, 3-dimensional graphs, and Ar/Ar dating can often deal with these problems. Snelling is exaggerating the problems just as Slusher (1981) did.
DAP: But anyway, there was too much in this article for me to absorb, so I encourage you (and others on t.o. if they see this) to read it.
KRH: David, please read my references. They'll help you.
DAP: So far those with whom I have discussed this subject have given me a total of about 2 examples of agreement between methods (other than K-AR and Ar-Ar) on the phanerozoic.
DAP: But anyway, I will make looking up some of your references my highest priority in the creation-evolution area. Thank you for the pointers.
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