In a similar vein, William A. Howard’s recent Journal of Chemical Education article “The Relationship between Balancing Reactions and Reaction Lifetimes: A Consideration of the Potassium–Argon Radiometric Method for Dating Minerals” (2) is written to create confusion in his primary audience—undergraduate chemistry students—by implying there is a controversy about the validity of radiometric dating. Instead of its purported objective of “stimulating critical thinking”, the article is itself a caricature of critical thinking, shot through with straw man arguments, false analogies, and red herrings.

Howard begins with a straw man argument: There is controversy about the validity of radiometric dating. Though Howard states the “purpose of this paper is not to suggest that mineral ages determined by the potassium–argon method are erroneous”, the entire paper is designed to cast doubt on the accuracy of radiometric dating. Indeed, one of his conclusions is that “…many of those involved with the teaching of biological evolution in public schools erroneously believe that scientists understand radioactive decay reactions very well….The reality is that no one understands these reactions entirely; the present exercise in critical thinking underscores this truth.” Radiometric dating is “controversial” only to young earth creationists, who continually misuse the technique (for examples, see refs 3 and 4).

To cast doubt on the accuracy of K–Ar dating, Howard sets up nonsense criteria—red herrings—that inculcate doubt in his audience, but are irrelevant. He also resorts to false analogies.

Red herring #1. Howard’s complaint is that “…nobody knows what the actual complete potassium–argon reaction is!” and “If a geochronologist truly knows a mineral’s age, then that geochronologist should be able to describe the chemistry behind the radioactive decay of ⁴⁰K in that mineral in great detail. If the geochronologist is not able to do so, then the mineral’s age is not really known.”

This is nonsense. The only requirement to get a good radiometric K–Ar date is that the system be closed to the isotopes involved in dating. Brent Dalrymple, author of many books and journal articles in this field, offers the following assessment:

Like all radiometric methods, the K–Ar method does not work on all rocks and minerals under all geologic conditions. By many experiments over the past three decades, geologists have learned which rocks and minerals act as closed systems and under what conditions they do so (5, p 93).

Those of us who develop and use dating techniques to solve scientific problems are well aware that the systems are not perfect, and we have provided numerous published examples in which the techniques fail. We often test them under controlled conditions to learn when and why they fail so we can avoid using them incorrectly” (6, p 80).

Nowhere in Howard’s article does he reveal anything that affects the ⁴⁰K:⁴⁰Ar ratio, the only quantity necessary to determine this age. He implies that there may be “unknown” ways of argon entering or leaving the rock, but provides no specifics, let alone references to scientific research. Dalrymple has already addressed this problem: “Some cases of initial ⁴⁰Ar remaining in rocks have been documented but they are uncommon, as noted by Dalrymple and Lanphere, who also described studies of historic lava flows showing ‘excess’ argon is rare in these rocks” (5, p 92).

Red herring #2. Howard complains that only the argon is quantified by geochronologists; the “identities and quantities of the ⁴⁰Ca products are unknown.” Dalrymple again, regarding ⁴⁰Ca, “…it is usually not possible to determine the amount of ⁴⁰Ca present initially, and the ⁴⁰K–⁴⁰Ca method is rarely used for dating.” Red herring, non-problem.

Red herring #3. The equations in Scheme 2 and the ensuing discussion. Howard’s two “very important facts” from these equations are: (1) Some compounds with unusual oxidation states are probably produced; and (2) ⁴⁰Ar is only a “minor product” in the reaction. These “facts” may sound important to undergraduates, especially those who are predisposed by their religion to reject radiometric dating, but what Howard fails to explain is that the small amounts of ⁴⁰Ar are completely analyzable by modern analytical techniques! Furthermore, the fact that some unusual oxidation states may be produced in no way affect the ⁴⁰K:⁴⁰Ar ratio, the only quantity relevant in the type of radiometric dating. Howard’s own equations demonstrate this.

False analogy #1. The corn in the grocery store. Howard states: “Just as the manager must count cans of corn and discarded cartons in order to judge how long the stocker had been working, so must the chemist identify and quantify all products from a reaction in order to determine how long the reaction has been going.”

No—this grocery store is locked! K–Ar dating is only performed on rocks that are closed systems. The only way the “corn” gets on the shelf is by the regular decay of ⁴⁰K, which Howard admits occurs at a known rate. Ideally no one can remove this “corn”, but if the “corn” does get removed, there are ways of detecting this, and the radiometric age may still be determined using the ⁴⁰Ar–³⁹Ar method detailed by Dalrymple and others.

False analogy #2. Corn, carrots, and beans in the grocery store. Howard diminishes the importance of using multiple dating methods (italics mine): “In order to build confidence in their work, geochronologists will occasionally determine mineral ages by more than one dating method…. Many times, the independent dating methods yield very similar ages, usually within experimental error, and so one may think that such results verify the accuracy of the age determination.” This thinking is specious according to Howard, because the “complete chemistries” of uranium–lead and rubidium–strontium dating are not known, either! He asserts that one only improves the precision, but not the accuracy, of the radiometric date.

This is a worse analogy than the first. The grocery store is still closed (or you don’t use corn, carrots, and beans to date anything) and it ignores the fact that the discarded cartons would at least be labeled “corn”, “carrots”, and ‘beans” (i.e., there would be distinct parent nuclides)! Howard might have a point if exactly the same assumptions about initial conditions were made in all three dating methods (Rb–Sr and U–Pb—the only additional ones Howard lists). In fact, the chemistries of the K–Ar, Rb–Sr, and U–Pb methods are totally different. The fact these disparate methods have led to convergent ages provides powerful support for radiometric dating.

Howard claims this paper “provides a detailed examination of a commonly accepted practice in geology” and “offers an example of how to stimulate critical thinking”. Instead, the paper is a caricature of how radiometric dating is performed and how successful it actually is. Rather than stimulating critical thinking, it is itself a great case study in logical fallacies.

The Journal of Chemical Education should pull this article from its Web site. You goofed.

Literature Cited

1. Krugman, P. Design for Confusion. The New York Times, August 5, 2005, p A15.
2. Howard, W. A. J. Chem. Educ. 2005, 82, 1094–1098.
3. Stassen, C. Criticism of the ICR’s Grand Canyon Dating Project. 1997 (accessed Feb 2006).
4. Bartelt, K. E. A Visit to the ICR. 1998 (accessed Feb 2006).
5. Dalrymple, G. B. The Age of the Earth; Stanford University Press: Stanford, CA, 1991.
6. Dalrymple, G. B. Ancient Earth, Ancient Skies; Stanford University Press: Stanford, CA, 2004.

See the author's reply, and the replies of two reviewers (1, 2) of Howard's article.