Volume 22, Number 1 January 1993


Physics and Cancer

As a physicist, who happens also to be a sometime American Cancer Society Research Scholar, may I make the following comments on Dr. L. Cranberg's commentary (October 1992)?
  • Dr. Cranberg seems worried about cancer: Many people eventually die of something or other, so it is not surprising to see that physicists get it, too.
  • The biology of cancers is an extremely complex subject, far removed from the physics for pre-med students which Dr. Cranberg mentions. For readings on this fascinating field, which is intrinsic to fundamental biology, see a modern biochem or genetics text for graduate students.
  • The "war" on cancer was, in large part, a politically-inspired one, perhaps on a par with "wars" on illicit drugs. The reader may judge the success of such "wars". (It was rumored, with some truth, that more scientists were supported by cancer funds than died of cancer.)
  • In spite of Dr. Cranberg's claim, physicists have been active in diagnosis and treatment of cancers (CAT, NMR imaging, etc., etc.).
  • Should Dr. Cranberg really wish to get excited about preventing cancer, then we already know how to prevent a substantial number of cancers: phase out tobacco smoking (but be kind to cigarette smokers; they're a dying breed). His library should subscribe to Tobacco Control.
  • Should Dr. Cranberg be personally afflicted or influenced by cancers, then I'm sorry, but my remarks stand.
  • Dr. Cranberg should join the Division of Biological Physics of APS which is an interface between biology and physics, pure and applied.

Leonard X. Finegold
Department of Physics Drexel University Philadelphia, Pennsylvania 19104

I am a physicist in the foxhole! Each day, I descend to the basement of the hospital where I am employed to do direct battle with the enemy, cancer. So do hundreds of other physicists--many of them belonging to the American Association of Physicists in Medicine (AAPM), a member organization of the AIP. In addition to the hand-to-hand combat of our daily work, many of us are actually involved in research, using our knowledge of physics and mathematics to improve treatment techniques, increase speed and accuracy of diagnosis, and model the basic biology of cancer cells and their response to radiation and other therapies. The AIP. journal "Medical Physics" publishes this research, as do at least half a dozen other journals.

Perhaps, as Larry Cranberg's comment suggests, the role of the physics foot soldiers has not received enough publicity in the wider community. But the enemy is wily and persistent. The war continues and we are always looking for new recruits!

It's good physics and a good fight.

Ellen D. Yorke, Ph.D.
Clinical Physicist George Washington University Medical Center Division of Radiation Oncology and Biophysics 901 23rd Street, NW Washington, D.C. 20037

Global Warming, Further Comments

I take the editor (October 1992, page 15) at his word and write to say that I am encouraged that serious discussions of economics, and not just political exhortations, are appearing in Physics and Society. The letter by John McGervey (October 1992), supporting the oft-proposed federal tax of roughly $1 per gallon on gasoline, is a mixture of the two. McGervey says such a tax would bring in $100 billion per year, and "Forty billion of that could cover the cost of maintaining naval forces in the Middle East --." Absent the need for gasoline, could our naval forces really be withdrawn from the Middle East? Would the Israeli lobby, for example, permit that? Why should drivers alone pay this cost of American foreign policy?

McGervey also wants to use that $100 billion to pay for "public transportation and rail travel." Should a poor but honest rural Nebraskan, commuting over many miles of prairie in an old car to hold a job, be taxed so that well-heeled Washingtonians can have a fancy subway? Raiding the gas tax to pay for mass transit and railroads is a misuse of public money, but I think it's happening a lot. In the dim past we young liberals learned that one group shouldn't be forced to subsidize another, except perhaps on the basis of need, or ability to pay. Has that changed?

Sad to say, Washington subway fares are now so high that for many trips, particularly outside rush hour, it's cheaper and faster to drive, even for one person alone, provided you're healthy enough to walk to free parking. Conversely, pay parking at the outlying stations is filled at rush hour, and feeder buses are inadequate. The economics of mass transit in some cities is iffy. Change and growth in such systems should be shaped by real marginal costs and not by subsidies. Control of people's lives by the fantastic tastes and prejudices of big-city mandarins isn't a proper use of the tax code.

Finally, McGervey makes the interesting point that the toll paid by a driver on a toll road is roughly $1 per gallon of gas used. He suggests that this indicates the real cost of the highway and shows that the gas tax is too low. Maybe so, but then why is the gas tax being raided for purposes other than road construction? Maybe, on the other hand, the tolls are set politically and are too high. (Many of us, not well off, have learned to avoid toll roads, and instead spew out pollution on stop-and-go streets.) Where are the subsidies? Who knows? Our establishment newspapers print many pages of electoral gossip but are short on economic analysis, and in fact discourage actively any challenge to liberal orthodoxy in matters such as high-occupancy-vehicle lanes on freeways and toll roads. Facing this obfuscation, the American people show good sense by rejecting a heavy gas tax. Would anyone write a competent article for Physics and Society on the economics of highways?

James E. Felten
8569 Greenbelt Road, #204 Greenbelt, Maryland 20770

David Hafemeister's discussion (October) of non-renewable resource pricing reflects little understanding of the market and an apparent unwillingness to learn the lesson of his own experience in government.

The fact that anticipated future prices affect the present value of resources makes the market far more prescient than the government, in which politicians' time horizons tend to stretch no farther than the next election. In a free market, the market value of finite resource reserves is bid up in anticipation of higher prices in the future, when the resource will become increasingly scarce. This causes prices to rise well in advance of the actual depletion of the reserves, thereby stimulating conservation, development of alternatives, and (as Hafemeister does note) the search for new reserves and exploitation of more costly, lower quality reserves. Some people may indeed reap high profits. (Hafemeister calls this "obscene," but what I find obscene are the wholesale robbery and coercion involved in economic collectivism.) Government intervention to prevent such profits disrupts the proper functioning of the market. Then, collectivists like Hafemeister can claim that the market didn't work, when in fact it is government intervention that didn't work.

The $400 billion deficit will not, as Hafemeister claims, be reduced by monstrous taxes on gasoline, for two reasons: first, because new taxes will leave people with less money to spend on other goods and services, thereby decreasing business activity and employment and reducing government revenues from other taxes; second and most important, because politicians will spend every last dollar of additional revenue, no matter how much, and still run up as big a deficit as they dare.

Allan Walstad
Associate Professor of Physics University of Pittsburgh Johnstown, Pennsylvania 15904

Hafemeister responds:

Concerning "somewhat obscene profits": Allan Walstad quotes me out of context. My letter discusses the Congressional control of oil prices after the oil embargo for three years, at a time when the OPEC oil embargo and arbitrary price hikes clearly destroyed normal market mechanisms. My letter states: "Around 1974, excess profits from oil that went from $1.50 to $12 per barrel were somewhat obscene." To first order the domestic profits were about $10/barrel x 10 M barrels/day x 365 d/y = $40 B/y. I think my use of "somewhat obscene" to describe this situation was justified. Since market force springs were broken, a temporary three year band-aide was a good idea, but as I pointed out it was a "political compromise."

Concerning gas taxes: It doesn't follow that a 50 cent/gallon tax, phased in over five years, would be used to create new programs. With a budget deficit of $300 billion, we will need both smaller government and a modest gas tax. My guess is that all three presidential candidates would agree, but that the issue is too political for them to come out for this idea. This is the kind of proposal that most politicians favor when they are out of office. Europe and Japan have much larger gas taxes and are in better financial shape than we are. Only a few large oil fields have been discovered in the past two decades, and the transition to alternate fuels (coal-based or renewable) will not be easy.

Space Station as Space Launcher

There has been considerable debate over the usefulness of a low earth orbit (LEO) space station. The civilian redirection of military sensor, guidance, homing, steering, global positioning, capacitor and electromagnetic massdriver (or "coil-gun") technology may enable such a station to become an integral part of a relatively inexpensive space-launch system.

Small high-acceleration-tolerant payloads could first be launched from Earth, e.g. by small linear mass drivers (MDs) to just barely reach points just above the atmosphere with zero velocity; launch velocities no higher than about 1.8 km/s should be sufficient to reach 140 km. Here they would be made to home in on and be "caught" at zero relative velocity by pre-accelerated catchers or buckets attached to external armatures sliding along space-station magnetic-coil MDs, and be rapidly slowed down to rest relative to the station by the MDs acting in reverse. The momentum of the station can be conserved by ejecting part of the payload at twice LEO speed relative to the station, so that it then ends up in an orbit opposite to that of the station.

Payloads which can tolerate up to 10^5g would require 65m-long catcher MDs and 260m ejector MDs, including the catcher-bucket pre-acceleration and deceleration distances. For a 16kg payload every 9 minutes an MD capacitor of 20 tons would be required with near-future capacitor technology, unless lighter superconducting or other alternative energy storage is developed. The 1 MW average power required could come from a nuclear reactor or a 120 x 120 m^2 3-ton solar array, although the latter would be exposed to the sun and provide power only half the time without mirrors or other relays. Eventually, however, the power could come from material launched by MDs from the moon and arriving just above the atmosphere with about 20 times its original launch energy, perhaps after undergoing one or more complete high-eccentricity "parking" orbits to guarantee optimal or continuous delivery. Most of it could then be slowed to LEO or zero velocity (relative to earth) by 365m-long MDs acting in reverse, thereby generating electrical power (which could also be beamed by microwave or laser to points in space or on Earth or the moon). But a portion could be speeded up instead and sent back to the moon to provide similar power for launching additional material and repeating the cycle.

Low-acceleration payloads could first be lifted by air-fuel explosions impacting "pusher plates" attached to the payloads to again just barely reach points just above the atmosphere with zero velocity. Here these plates would be impacted by explosively-expanded orbiting packets assembled at and launched in succession from the space station (or the moon). By using shock absorbers between the plates and the payloads (as in Orion-project nuclear-bomb propulsion) non-damaging acceleration of even relatively fragile payloads into LEO should be possible.

Louis A.P. Balazs
Department of Physics Purdue University West Lafayette, Indiana 47907-1396