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Peter D. Zimmerman discusses radiological dispersion devices (RDD's or "Dirty Bombs") and their economic and psychosocial effects in The Back Page of the March 2004 issue of APS News.
One of the members of the 911 families that visited Iraq in February 2003 indicated during a presentation here in Detroit that "Dirty Bombs" were dropped by the US during Operation Desert Storm. It was reported that the radiation has had a major effect on Iraqi civilians. Is it true that the US dropped "Dirty Bombs" during Operation Desert Storm? If so, why didn't Zimmerman address this example either along with or in place of the 1987 Goiania, Brazil event? It is clearly more relevant to terrorism than the Brazilian event, and should be studied extensively.
James R. Woodyard
Peter D. Zimmerman wrote about the threat of terrorists using radioactive "Dirty Bombs."
However, he neglects to mention the US military's use of depleted uranium weapons in Iraq and elsewhere. The US and Britain used 1,100 to 2,200 tons of depleted uranium shells in Iraq in March and April, 2003 alone. Depleted uranium is approximately 40% less radioactive than natural uranium, but its use has still resulted in measured radiation levels 1,000 to 1,900 times higher than normal background levels in Baghdad.
This radiation is affecting our own troops and Iraqi civilians. For example, military personal who served in the 1991 Gulf war, in which approximately 630,000 pounds of depleted uranium were used, were 5.6 times more likely to develop lymphomas and 4.8 times more likely to develop leukemia than a control group. "The death rate per 1000 Iraqi children under 5 years of age increased from 2.3 in 1989 to 16.6 in 1993".
The threat of terrorists using radioactive weapons is certainly a frightening possibility, but the US military's use of radioactive weapons is a deadly reality. We must end the use of "Dirty Bombs" by our own military if we expect others not to use "Dirty Bombs" on us.
Peter D. Zimmerman replies:
Contrary to the assertion by James R. Woodyard, the United States has no radiological dispersion devices or "dirty bombs" in its stockpile of weapons. RDDs are demonstrably useless as weapons intended to kill or incapacitate people in a predictable way-unless the amount of radioactive material used is so large as to prevent an aircraft from taking off because of the mass of shielding needed to protect ground and air crews. The United States did not drop dirty bombs during Operation Desert Storm or Operation Iraqi Freedom, period.
I am saddened that a member of the 9/11 families group should have been so badly taken in by Iraqi propaganda.
We did, however, as Ashley James suggests, use depleted uranium (DU) shells and warheads to engage and destroy Iraqi armor. The half-life of depleted uranium (essentially just pure U-238) is around 4.5 billion years, essentially the age of the earth. Thus, depleted uranium is, for all practical purposes, not radioactive enough to cause a health hazard.
However, as are almost all metals at the high-Z end of the periodic table, uranium is toxic and can be dangerous to the kidneys. Frank von Hippel and Steve Fetter, neither one a "hawk," demonstrated fairly conclusively that the contamination from our DU weapons posed no significant hazard to civilians in their decade-old article in the journal Science and Global Security.
I used DU as shielding material in some experiments I've done, and as a target in others, all with very little in the way of precautions other than handwashing and rubber gloves. Indeed, at one laboratory we used a DU shielding brick as a door stopper.
Some Iraqis were badly injured after Operation Iraqi Freedom when they "liberated" blue plastic drums used by the Iraqi atomic energy establishment to store uranium tetrachloride.
The Iraqis dumped the uranium compounds and then used the drums for water and bathing without first flushing the containers. The residual UCl4 formed hydrochloric acid in solution and produced serious chemical burns.
As a physicist in the laser field since 1969, I enjoyed reading the article "This Month in Physics History, December 1958: Invention of the Laser".
However, one statement about the first realization of the laser in 1960 raises some criticism. The relevant sentence should read, in my opinion, "...the same year the first working laser was built by Collins and coworkers at Bell Labs..."1-and not by Theodore Maiman, as stated.
What is a working laser? It is a light-amplifying device that operates above a certain threshold with mode selection. The latter gives rise to a large line narrowing and an intense emission in a drastically reduced beam angle. To support this statement, I point to the paper of Maiman et al. submitted in January 1961 to Physical Review. The authors write2: "...the nature of the output radiation from the various ruby samples which were tried could be divided into two categories:
A. Crystals which exhibited R1 line narrowing of only 4 or 5 times, a faster but smooth time decay of the output (compared to the fluorescence), an output beam angle of about 1 rad, and no clear-cut evidence of a threshold excitation. This type of behavior was reported and discussed by Maiman [See reference 3 below].
B. Crystals which exhibited a pronounced line narrowing of nearly four orders of magnitude,...beam angle of about 10-2 rad;...a very clear-cut threshold input energy....This second category of behavior was reported by Collins et al. [See reference 1 below], and is the subject of further study reported here."
Obviously case B represents a working laser.
1. R.J. Collins, D. F. Nelson, A. L. Schawlow, W. Bond, C.G.B. Garrett and W. Kaiser, Phys. Rev. Lett. 5, 303 (1960) [received August 26, 1960].
2. T. H. Maiman, R.H. Hoskins, I.J. D'Haenens, C.K.Asawa and V. Evtuhov, Phys. Rev. 123, 1151 (1961) [see page 1154].
3. T. H. Maiman, British Communications and Electronics 7, 674 (1960); Nature 187, 493 (1960) [issue August 6].
I was struck by the fact that the front page of the February APS Newsfeatured several items relating to government policy on national and international affairs.
These are contentious times, and the public is deeply split about our national government. The only way an organization such as ours can maintain its integrity is to be absolutely factual—no value-laden words or phrases.
Two of the front-page stories met this criteria and were both objective and informative. The Beltway article, however, featured several partisan expressions about one political party, saying, for example, "They succeeded in their mischief."
To avoid any misunderstanding, I hope that in future we can choose our words with more care.
George F. Bertsch
The letter in the March 2004 APS News by Paul Weisz on the basic science constraints of a hydrogen economy states that the annual addition of carbon dioxide to the environment by fossil fuel combustion is about 2.5 x 109 tons. The global number is actually close to 2.5 x 1010 metric tons/year, of which roughly half accumulates in the atmosphere, and half is absorbed in the ocean or on land. The total US carbon dioxide emissions in 2002 were about 5.8 x 109 metric tons. A single 1000-MW coal-fired electric utility plant operating at 100% capacity releases about 24,000 metric tons of carbon dioxide into the atmosphere every day.
The Kyoto Protocol treaty signed by the United States in 1998 set an annual limit of about 4.7 x 109 metric tons by 2012.
The only alternative to reducing carbon dioxide emissions is sequestration. Weisz states that "pumping of high concentrations of carbon dioxide into deep sea or geological locations is possible but permanence of such disposal would be variable and uncertain." Pipelines carrying high pressure liquid carbon dioxide have been successfully used in the United States for oil recovery.
One example is the Sacroc pipeline system in West Texas, which has transported up to 12,000 tons/day in over 100 miles of 16" diameter pipe. But sequestering high concentrations of carbon dioxide under pressure is also a health risk. In 1986, Lake Nyos (in Cameroon), in which thousands of tons of carbon dioxide had been sequestered naturally, suddenly and without notice "erupted" and asphyxiated over 1700 people. Global warming is a serious concern, and sequestering carbon dioxide emissions on such a massive scale is both uncertain and risky.
Los Alamos, NM
In his letter in the March 2004 APS News, P. Weisz seems to miss the point that hydrogen can be produced in other ways than just by isolation from fossil fuels, a process which, as he points out, renders hydrogen as an alternative fuel mostly advantage-less. Electrolysis of water, using electricity generated by windmills, solar arrays, and even dams, comes immediately to mind.
C. Cunningham, in turn, doesn't point out probably the biggest advantage to using hydrogen generation by an alternative energy source: that generating hydrogen would alleviate the problems of highly variable output associated with alternative sources (since they depend on wind, sun and even river levels) since, even with inefficiencies, hydrogen would provide a great energy storage medium.
It would be a definite improvement over storage batteries, which require much maintainance and replacement, are often toxic or dangerous, and have their own inefficiencies. Hydrogen could even be burned right at the generating site when needed, the power carried in the existing electrical grid, and the water recycled for further use.
Cunningham does point out several other advantages to hydrogen power: environmental friendliness (both in terms of human health and terrestrial climate effects) and energy independence for the US, and the attendant advantages in terms of American foreign policies.
The time to begin seriously developing such real alternatives to foreign oil development is now, not when the ill effects of our oil and coal addiction become critical, or when these fuels begin to run out.
And what country on Earth is better equipped with scientific and technical expertise for the task? Unfortunately, to our current short-sighted administration, the term "energy independence" is essentially synonymous with drilling for more oil, regardless of the consequences, and it views with poorly- concealed contempt the very idea of energy efficiency and conservation.
The one technology the Bush administration seems to have any enthusiasm for is just that hydrogen- from-fossil-fuel technology that Weisz mentions. This has few advantages and, by a remarkable coincidence, preserves US dependence on big oil.
Paul B. Weisz (APS News March 2004)reminds us of the fundamental importance of thermodynamics: Nothing is free and, in the last analysis, a hydrogen economy has its own costs.
In the same issue, Clarence M. Cunningham optimistically suggests that we should generate hydrogen using renewable resources such as solar cells and wind energy to avoid environmental degradation.
Energy (whether it comes from coal, oil, hydroelectric sources, or someplace else) must be added to the system that produces solar cells and windmills. Of course, along the way much of this energy is lost before the assembled devices generate energy on their own.
What is the efficiency of this process? How long must manufactured devices operate before the input energy (cost) is repaid? How long will the device continue to produce energy before it wears out and needs to be replaced (more energy input)? In the end, thermodynamics is not forgiving.
Ernest L. Lippert
It was interesting to see the Michelson watercolor on your front page of APS News.
In 1987, for the Centennial Celebration of the Michelson Morley experiment here at Case Western Reserve (where the experiment was done), we had a couple dozen of the Michelson watercolors copied and framed. They decorate the public areas of our physics building and are so familiar to everyone here that the appearance of one tiny work on your front page came as a surprise.
The February issue of APS NewsBack Page article by W. A. Wulf addresses a timely issue of visa problems faced by foreign students and scholars. He referred to the current practice as out of balance. It'd be more direct to say that it is out of control. In the past three years at UMass Dartmouth, our graduate applicant pool in physics has dwindled from about twenty, to low teens, to single digits now. It has created a crisis in our department, negatively impacting research and teaching. Our evidence is anecdotal, but we know many small physics departments experience similar trends.
The impact on larger departments will surely follow suit as more students will look elsewhere, such as Europe or Canada. The current visa restrictions are causing great damage. This is like a fool lifting the stone just to drop it on his own feet. There is good news, though.The time graduate committees spend reviewing applications has been reduced. We owe our thanks to the infinite wisdom of our government bureaucrats and some politicians who cook up schemes, like charging $100 non-refundable fees, which amounts to a two-month salary in some countries. Better yet, if a student dares to mention words such as "atomic, biological, or nuclear" in his studies, he must be planning to make WMDs, and we just cannot allow that.
But complaining by itself will accomplish nothing. We as individuals need to spring into action, to write to our congressmen, and to bring it to the public's attention.
The APS, perhaps in alliance with other similar organizations, should redouble its effort to lobby Congress, to advocate for dismantling or severely scaling back SEVIS, and to collect data from member departments to document the damage. Unless the tide turns quickly, we may be witnessing the beginning of the dismemberment of homeland science, and the end of an era of in free scientific exchange with the US.
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