Involved with nuclear weapons and nuclear power since 1950, a member of the APS study group on the safety of lightwater reactors (1975), and various government-sponsored studies on reactor safety and allied topics, I judge nuclear power to be a valuable option now and for the future. I have studied the Chernobyl and Three-Mile-Island accidents, and the French, Japanese, Chinese, and Russia nuclear power programs. But Wolf tells only part of the story, reminding me of the "not proven" arguments of the tobacco executives. The merits of nuclear power should carry the day, without propaganda-- either for or against. The best judgment of the International Commission on Radiation Protection (ICRP) is that even for low-level radiation, deaths due to cancer occur at a rate of 0.04 per person-sievert (400 per million person-rem). There is little dispute over the collective exposure to the population of the European community and the (former) USSR as 600,000 person-Sv. The cancer deaths are thus likely to be 24,000 (and not the 40 cited by Wolf).

No critic of nuclear energy, Morris Rosen of the IAEA at a session in Nagoya in April 1996 stated, "For the 3.7 million residents of other contaminated areas the predicted lifetime excess is 2500 over the normal 430,000." He stated that the average dose to each of those individuals was 7 mSv, for a collective dose of 26,000 person-Sv. (The background exposure averages some 3 mSv per year.) But at that session (see http://www.fas.org/rlg and look for "Nagoya") and in further correspondence, IAEA has never been willing to concede that a collective dose of 600,000 person-Sv to the population of the USSR would correspond to 24,000 additional deaths, despite the judgment of the ICRP and the Board on Effects of Ionizing Radiation--BEIR--of the National Academy of Sciences, and despite the IAEA spokesman himself indicating that 26,000 person-Sv at nearly the same dose and dose rate would eventually lead to 2500 excess cancer deaths. These additional hazards due to Chernobyl are less than 0.5% of natural cancer deaths among the exposed population. Radiation hazards due to nuclear power, including accidents, are low enough to be taken into account in normal cost-benefit analyses; but they are not zero.

As for the "maybe healthy effects of low radiation levels", Wolf may be referring to a speech of John Graham of 1996, that cited a comparison of two areas in China, one with high background radiation and one with more normal. I have analyzed these data in conjunction with a book that Georges Charpak and I will publish in English in 1999 (derived from a book we published in France in 1997), and find that the ICRP estimates of radiation-induced cancer would lead to the observation of 4 excess deaths in the high-radiation area. Compared with the 25 expected fluctuation (standard deviation of the difference), radiation induced deaths could simply not be observed.

I oppose the use of legal intervention for delaying (as contrasted with settling) siting decisions. I think that commercial and competitive mined geologic repositories in various countries and areas would be highly beneficial to public health and to the nuclear industry, but this is true even with the predicted radiation exposures from the nuclear fuel cycle and the ICRP estimates of deaths due to cancer. It is not helpful to hinge the future of the nuclear industry and an important element of the energy supply to a claim that low levels of radiation cause "negligible" damage or are even helpful.

Richard Garwin

Senior Fellow for Science and Technology, Council on Foreign Relations;

IBM Emeritus Fellow; Adjunct Prof. of Physics, Columbia University

e-mail: RLG2@watson.ibm.com

In an article about "Voodoo Science," in Physics and Society, 27, # 4, Robert L. Park accuses NASA of "trying to beat the laws of thermodynamics" by the flight of the Tethered satellite (TSS) experiment, comparing NASA to "backyard inventors with a grade school education."

Unfortunately, Dr. Park seems to be utterly in the dark about the TSS experiment. This is a pity, since the TSS experiment was an interesting demonstration of quite simple physics. An electrodynamic tether-- that is, a flexible, conductive cable deployed from an other orbital vehicle--is a method of exchanging momentum between the Earth and a spacecraft's orbit, via the Earth's magnetic field. There's nothing "mysterious" or "pseudoscience" about it, in fact, it makes a fine example problem for an introductory class in electromagnetism. As the tether crosses the Earth's magnetic field, a voltage builds up along the tether. If current is allowed to flow resistively, energy is taken out of the orbit and can be used for electrical power; if current is instead applied to the tether, power can be taken out of an electrical power source (such as a solar array) and the orbital energy increased. This effect is known as a "Plasma Motor-Generator" ("plasma" in this case refers to the fact that the circuit is closed through the ambient space plasma).

Despite Parks' disparaging references, a Plasma-Motor Generator does not violate the laws of thermodynamics, although it is a method of orbit raising (or lowering) with no expenditure of rocket fuel. In "rocket scientist" lingo, it has infinite specific impulse, which is as close a thing to a free-lunch as you're ever likely to see. A number of innovative applications for tethers and tether propulsion systems have been proposed, ranging from power and propulsion in the Jupiter system, to orbital reboost in Earth orbit. It's a pity that Robert Park lumps these in the same category as perpetual motion machines, since some of these are quite elegant applications of simple principles to physics.

Information about tethers can be found on the Tethers Unlimited web site, http://www.tethers.com/, at the NASA Marshall Tether site, http://infinity.msfc.nasa.gov/Public/ps01/ps02/space.html, the ShuttleElectrodynamic Tether Experiment page, http://setswww.sprl.umich.edu/ , and in the tutorial "Electrodynamic Tether Power Generation," http://infinity.msfc.nasa.gov/Public/ps01/ps02/sstp.html

Geoffrey A. Landis

Ohio Aerospace Institute

http://www.oai.org/SRA/g_landis.cfm

In "Voodoo Science: Perpetuum Mobile" (Physics & Society,27, No.4, Oct.1998, p.4), Robert Park gives an amusing account of devices that were claimed to forever produce more energy than was put into them. Such "proposals" can have considerable pedagogical value, however. So can schemes which may, at first sight, resemble typical perpetual-motion machines, but which, whatever their practical utility, actually do obey all the laws of physics.

Several years ago, I was personally accused of proposing a perpetual-motion machine (by a Mechanical-Engineering Professor with a Ph.D. in Physics) when I outlined a hypothetical space-power scheme in which packets of lunar material would first be "slung" electromagnetically from the moon towards earth. Their original launch kinetic energy would then be amplified gravitationally by a factor of about twenty on reaching the "edge" of the earth's atmosphere. Here, (e.g. after rapid expansion to non-damaging density), their homed-in controlled horizontal "impacts" with initially- slow spacecraft and orbiting generators could convert part of their kinetic energy into usable craft propulsion and electrical energy. A fraction of the latter could then be sent back to the moon, e.g. by microwave beam, there to launch additional lunar material and repeat the cycle,seemingly perpetually.

Eventually, of course, the moon, which acts as a vast reservoir in this siphon-like scheme, would shrink, preserving thereby the laws of physics. But this would take hundreds of millions of years to be significant at present global energy-consumption rates.

Louis A.P. Balazs

Department of Physics

Purdue University

West Lafayette, IN 47907-1396

balazs@physics.purdue.edu

I read with interest the debate on science by Alan Scott, Bob Salt, and Ken Parejko in the October, 1998, issue of Physics and Society. Perhaps an experience of mine may be relevant.

Four years ago, my wife and I were walking in Brown County State Park in south-central Indiana. Shortly after we entered a grassy clearing in the woods, a flying saucer, about 50 feet in diameter and 8 feet high, landed beside us. A half dozen green manlike creatures emerged and wanted to abduct my wife. I tried to stop them, but one of the green men pulled out a sword and lopped off my head. My wife quickly pulled out of her purse a magnet that we had acquired in India during our visit in January, 1971. She pointed the magnet toward my head, which then rolled two feet to my body and attached itself smoothly. Shortly afterwards, I got up, a little weak from loss of blood, but otherwise whole. There was not even a line around my neck. The green men lost all interest in my wife, but snatched the magnet and flew off. We never saw them again.

I have little doubt about what Alan Scott's attitude would be toward this story. He would think that the probability that the story was true was much smaller than the probability that it was a dream, a hallucination, or a hoax. He would reason that he, as a scientist, should not investigate because he would be be much better off working on a problem with a greater, probability of having a positive payoff. Good scientists do not spend their time chasing chimeras.

On the other hand, I don't know what Bob Salk's attitude would be. Would he really fault scientists for dismissing my story without examining the evidence? I think not. But Salt wants scientists to examine other phenomena that are also extremely unliely to be true. No convincing evidence has ever been found for the existence of transpersonal or paranormal phenomena. The scientist who follows Salk's advice to investigate the subject will have a very high probablity of just wasting his/her time. But I don't expect scientists to follow Salk's advice.

Don Lichtenberg

Department of Physics

Indiana University

Bloomington, IN 47405

812-855-2329 (phone); 812-855-5533 (Fax)

lichten@indiana.edu

This letter is in response to the public debate on science that appeared in the October issue of Physics and Society. My concern is that not only is pseudo-science speculative and deals with unverified claims, it targets people when they are most vulnerable and are not always in a position to make rational decisions. Take the example of the mother whose child burned her hand. I have no problem with her choosing to use a healing magnet if she had some understanding of what magnets can do and cannot do, and of the dangers involved. My problem is her unquestionable and complete faith in them. A hospital minister told me of an incident that happened to her. She was sitting in the emergency room of a hospital with a family whose child was almost dying because he had swallowed a poisonous chemical. As they were waiting for the doctor, a young woman comes in and tried to convince the parents that she can cure their child if they would only let her see him. The parents being in such a vulnerable state were tempted to listen to her. Fortunately, for all involved that woman was escorted out. And that is exactly the point I am trying to make. That family could have wasted precious time and had false hopes had they trusted her. I will even play the devils advocate and assume that there are such things as healing devices. Not educating people on this subject will lead to ignorance of whom to trust and whom not to trust. So far, these healing gadgets are simply a business. I dare anyone who sells and profits from selling healing devices to burn his hand, or even better his/her childs hand, if possible, and then use a magnet to cure the hand! I realize scientific demonstrations may often fail, but we are not dealing with scientific demonstrations here. As an educated society, we have a moral responsibility to help people make informed choices.

When I was younger I was fascinated with astrology and fortune reading. I read quite a few books on the science of astrology, and tried to experiment. I made up this card game and went around reading peopleUs fortune. I had the best time of my life shocking people, telling them what is going on in their lives and what will happen. Basically, I tested my water and by studying body movements and reactions, regardless of how subtle. If the issue was not related to a job or romance I kept prodding to find out what made the person react. I always got at least a "How did you know this?U or "Should I do this or that?" I found out where they were vulnerable and they looked up to me. After having my fun, I always told the person I made the whole thing up. The point that pseudo -science, ESP, and astrology are often directed at the most vulnerable is important to consider.

R-M Marroum

marroum@bc.edu