APS News

Letters

Last Word on Creationism

Since his letter was sent to APS News, we may assume that John Cimbala has been trained in science. That he is able to crowd so many misconceptions about the scientific method and the theory of evolution into so little space is a sad commentary on the quality of that training.

Although a letters column is not the place for an extended discussion, the following should be noted: in contrast with creationism, evolution is a science, not a religion, and as such takes no position on the existence of God, either for or against. Science provides for inferences regarding unobserved past events, such as the origin of life, basing them on present observations. The mounting evidence is mostly for, not against, evolution. Even if evolution were eventually rejected on the basis of future evidence, it would not then follow that creationism would be proven, since it is not, in fact, the only alternative.

John G. Fletcher
Livermore, Calif.

Intratomic Superconductors?

In the APS News of July 1997, the summary of events from Washington, DC, mentioned "Proton-Neutron Correlations"; an effect was introduced by the statement (p. 1) that, "It is a little-known fact that all nuclei are superconductors,."

I think it should be even less known than little: In a classical regime, electrical conductors dissipate energy as heat because the individual electrons can excite the crystal lattices at random. But, it seems that a superconductor conducts by paired electrons, which pairs have so low a spatial frequency that they rarely transfer energy to the crystal lattice. So, superconductors dissipate essentially zero heat.

All energy or momentum transfers inside a nucleus are quantized; it can't transfer random, small amounts of heat to the surrounding electron cloud or neighboring atoms. So, why apply the term "superconductor" in a circumstance in which infinite conductivity, and perpetual motion, is the norm, anyway? Are paired nucleons faster than single ones-or, do they waste less energy when used to do work?

Let's look at the phenomena, and leave the analogies for the after-hours poetry meets.

John Michael Williams
Redwood City, Calif.

Pittel Responds

On the one hand, what Dr. Williams says in his letter is correct. Nuclear superconductivity is not the same thing as superconductivity in solids. As noted in the [Virtual Press Release], for example, the pairing correlations that enter are somewhat different in the two cases. In solids, it involves "momentum pairing." In nuclei, it is "angular momentum pairing." Clearly the physical manifestations will be different. In addition, the number of particles contributing to the collectivity is different in the two cases. It is a fairly small number. In solids, the number is much much larger. AIt is only the "valence nucleons" that pair correlate in this way. The nucleons of the core do not.

Nevertheless, there are some interesting similarities. In both cases, there is a sizable gain in energy associated with the "superconducting solution" of the BCS equations. In both cases, the system behaves as a set of "independent correlated pairs". And there are other similarities as well, athough some people may feel they are a bit forced. The Josephson tunneling analogy is one example.

From my perspective, the important point is that there is a pervasive collective mode in nuclei which involves pair correlations. Whether it should be called superconductivity (in the strictest sense) isn't the key point.

Let me add, however, that it is nice to think of this collective mode vis a vis superconductivity. It establishes a connection between physical phenomena in very different fields. Not a precise connection, I agree. But an interesting and useful one, I believe.

Stuart Pittel
Bartol Research Institute, Del.

U.S. Productivity Figures Underestimated

In the Back Page article by President Clinton (APS News, July 1997), there occurs the following sentence: "Fully half the growth in economic productivity over the last half-century can be traced to research and technology." I have seen this statement elsewhere, though none of the people who use it say where the information comes from. I would like to challenge this statement as a gross underestimate.

Over the period in question, productivity wealth generated per member of the workforce in the United States has about doubled. The implication of the statement is that, if the incorporation of new science and technology into the workplace had ceased in 1947, that half of this increase in productivity would have happened anyway.

Moreover, this does not take into account the greater variety, power, durability, value and usefulness of the products produced today - all of which comes from science and technology. If I were to claim that 95 percent of the increase in productivity and the increase in our material wealth as being due to research and technology, could anyone contradict me?

Alwyn Eades
University of Illinois

Importance of Publicly Funded Science to Industry

This article was interestingly juxtaposed with the George E. Brown piece claiming that publicly funded science needed to be downsized. Does this not make clear that we need a method of funding science which has a direct feedback with the needs, rather than as filtered though our politicians? This will not happen unless scientists take the initiative of inventing better methods than the patent system currently in place.

Elmer Eisner
Houston, Texas


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Editor: Barrett H. Ripin