The October/November issue (pp. 1214) sported three
letters in raucous opposition to the August/September article
to thinking new about energy, by Laura Nader (p. 24).
In a paranoid frame of mind, I might suspect that Dr. Nader made
up the three letters to buttress her original case. In a more
charitable view, the letters show the value of free and open speech.
In my reading, Dr. Naders detractors unintentionally provide
strong support for the points made in her original article.
Cascade Microtech, Inc.
Relativity and clocks
I enjoyed the
article on the Global Positioning System in the October/November
issue (pp. 2427). I think it would be of interest to your
readers to note that adjustments are made to the readings of the
clocks to compensate for the general relativity effects on the
signals passing through the Earths gravitational field.
I believe there also may be compensations based on special relativity
consequences of the relative velocity of the satellites in relation
to the receivers on the surface of the Earth.
In his article Global
Positioning System: A High-Tech Success (October/November
2002), Neil Ashby states that Louis Essen and John V. L.
Parry built the first atomic clock in 1955 at the National Physical
Laborator y in Teddington, England. That is incorrect. The
first practical working cesium clock was built by Jesse Sherwood
at the National Bureau of Standards (NBS) shortly before 1952.
Jesse came to Oak Ridge National Laboratory in 1952 after building
the clock and putting it into operation at NBS. He left NBS after
his supervisor, Ernest Lyons, who had little first-hand connection
with the project, took credit for the clock and presented a paper
on the subject. That whole scenario was covered in an article
in Physics Today about 2030 years ago.
Paul E. Thurlow
Raytheon Santa Barbara Remote Sensing
[Author replies: Dick Medvick has called attention to
some important effects arising from both special and general relativity
that have to be accounted for if the Global Positioning System
(GPS) is to work properly. These effects include gravitational
frequency shifts of satellite clocks relative to clocks on Earths
geoid, and Doppler shifts, including second-order Doppler shifts
(time dilation). First-order Doppler shifts are removed by receiver
circuitry. These effects are discussed in a recent article published
in Physics Today (1). The Shapiro effectthe time
delay of electromagnetic signals passing through Earths
gravitational fieldis only a few hundredths of a nanosecond
and ordinarily is negligible in the GPS except in the most demanding
Historians generally credit Essen and Parry with the first successful
cesium clock (24). It is true that research on the cesium
clock was carried out at NBS in Gaithersburg, Maryland, before
Essen and Parry began their work, but a cesium clock was not successfully
operated at NBS until the late 1950s, and the early research apparently
existed only in internal reports and was not published in the
open literature. Essen visited NBS on several occasions and referenced
the early NBS work in the first published paper on cesium clocks
(5). Neil Ashby]
1. Ashby, N. Relativity and the Global Positioning System. Physics
Today, May 2002, pp. 4147.
2. Jones, T. Splitting the Second: The Story of Atomic Time;
IOP Publishing: 2000.
3. Sullivan, D. Time and Frequency at NIST: The First 100 Years;
IEEE International Frequency Control Symposium, 2001; IEEE Catalogue
No. 01CH37218; pp. 417.
4. Forman, P. The first atomic clock program: NBS, 19471954.
Proc. Ann. PTTI Meeting; available from the USNO Time Service;
pp. 117 (1985).
5. Essen, L.; Parry, J. V. L. Atomic standard of frequency and
time interval. Nature, 1955, 176, 280285.
article Introducing a Bachelor of Industrial Physics
(August/September, pp. 2829), was appropriate and interesting,
but not as new in concept as the author assumes.
In 1949, I graduated from Virginia Polytechnic Institute (now
Virginia Polytechnic Institute and State University) with a B.S.
in industrial physics. At the time, the physics department was
small, and, in developing the curricula, it relied on many of
the larger engineering department courses to supplement the available
ones in physics. I omit the usual English course requirements
in the discussion below.
I cannot find the list of my courses, which, considering their
time frame, certainly paralleled those in your article, and their
intent was the same. I still have some of my textbooks and, with
their help, have reconstructed parts of the curriculum. I took
engineering drawing, machine shop (which is still useful), engineering
statistics, and statics and dynamics. I took courses in ac/dc
circuits and electronics in the electrical engineering department,
which were about vacuum tubes at the time, but circuit design
principles are still valid. Inorganic and physical chemistry in
the chemistry department also were required. I remember taking
a course in metallurgy that has been forever helpful. The curriculum
included the usual math courses, along with physics courses such
as optics, thermodynamics, and applied nuclear physics. Quantum
mechanics was not taught at the undergraduate level, although
the introduction to nuclear physics course presented some of the
Advanced laboratory courses were designed to use industrial
instruments (digital computers, scanning electron microscopes,
secondary ion mass spectroscopy, and Auger spectroscopy had not
been invented at that time). We had lab courses in X-ray diffraction
and spectroscopy, both of which were extensively used in industrial
labs for analysis. Looking back, I believe I received good preparation
for my lifes work.
It is worth following my career path after this training.
I was hired as an electronic engineer in 1950, partly because
of my being a ham radio operator. I received an M.S. in physics
in 1959 at the University of Maryland while working, and I published
11 papers in The Physical Review and the Journal of Applied Physics.
However, I eventually migrated back to my industrial physics background
and am now involved in electronics packaging and interconnections,
writing books on wire-bond interconnections (an ultrasonic welding
method used to interconnect chips to the outside circuit), and
publishing mostly in transactions and conferences of the Institute
of Electrical and Electronic Engineers (IEEE). I am a Life Fellow
of the IEEE and still maintain membership in the American Physical
George G. Harman
Chevy Chase, Maryland
[Author replies: I thank George Harman for his comments
and support. His alma mater has an interesting history of the
physics department on its
Web page and lists the years for which a B.S. in industrial
physics was offered as 19371953. A masters degree
in applied and industrial physics was introduced in 1996.
Another parallel to the industrial physics curriculum is the
idea of a core curriculum in engineering. This is the idea that
you are an engineer first, and then you have a specialty. Perhaps
with the pendulum swinging widely to the side of specialization,
the need for generalists is emerging. If this is true, then physics
is in a good position to benefit from the trend. We should try
to convince business and students that more-fundamental training
will serve both industry and students better in the long run than
a highly specialized technology-dependent education. The dividing
line between the sciences and engineering is getting increasingly
blurry. Personally, I welcome the change.
We at East Stroudsburg University have a lot of work to do. Your
encouragement is much appreciated.
David A. Larrabee]
Physicists should be encouraged to look at, and then beyond,
the post-9/11 challenges that have befallen the Nuclear Regulatory
Commission (NRC) as summarized by Richard A. Meserves article
security in a new world, October/ November, pp. 2023).
Probably no other profession is more connected to nuclear security
by its craft or by its history than physics. Physicists can make
themselves knowledgeable about the problems that face the NRC
and about other related issues of nuclear terrorism by accessing
the available information (see some examples in the references).
This playing field is broad, with many competitors in the arena,
but with a bit of effort one can ascertain the primary issues
concerning our nuclear insecurity problem.
They include the following:
1. Nuclear watchdog organizations such as the Nuclear Control
Institute (NCI) contend that the NRC acts like a regulatory agency
captured by the industry it regulates. This, they
say, jeopardizes nuclear security because of the apparent contradiction
in the function of the NRC 1).
2. The NRC has been accused of running mock terrorist drills
that do not sufficiently mimic the present threat (the so-called
design basis threat or DBT). The DBT response by nuclear-plant
security forces has a controversial history. The NCI reported
a failure rate (marked by the inability to repel the mock force)
of about 50%, although the results have been debated (2). According
to Dr. Meserve, the DBT is to be revised. Hopefully, success rates
using a more rigorous DBT will be higher and not as disputable.
3. In an analogous situation, the U.S. Department of Energy (DOE)
faces security threats at some of its installations that hold
inventories of weapons-grade plutonium and highly enriched uranium.
The Project on Government Oversight critiqued the failure of DOE
security forces to repel mock terrorist attacks (3). Again, an
inability to repel many attacks was seen. Recently, DOE moved
plutonium from its Los Alamos valley site to the more-secure Nevada
Test Site because the valley enhanced the ability of terrorists
to steal nuclear materials.
4. Although nuclear containment buildings are sturdy structures
that may be able to withstand the worst of the destructive effects
of an impact by a fully fueled jetliner, ancillary structures
like spent-uranium fuel-holding facilities are not as rugged.
To respond to this problem, reactor operators can strengthen spent-fuel
facilities against fire and impact or, if given the opportunity,
transfer the spent fuel off-site to a national high-level nuclear
waste repository such as the Yucca Mountain, Nevada, site run
by DOE. Its ecological considerations are still debated (4). The
controversial shipments of spent nuclear-reactor fuel that may
also require security measures are not expected to begin until
5. The international nature of nuclear security and how it impacts
home is demonstrated by the demilitarization of nuclear weapons.
By agreement, the U.S. and Russia have both put 34 metric tons
of plutonium derived from weapons into surplus. The plan to burn
plutonium as mixed oxide fuel at privately owned U.S. plants is
controversial (5). The security of this material and highly enriched
uranium in Russia is also worrisome (6). These few points illustrate
that the nuclear terrorism problem goes beyond one agency and
one kind of threat. Consider also the dirty-bomb issue
that the Health Physics Society and the Federation of American
Scientists are attempting to address (go to www.hps.org or www.fas.org
for more information). It has recently been said that Americans
are becoming complacent about homeland terrorism. If so, this
would be a good time for practitioners of physics, a profession
with a legacy of nuclear concerns and debate, to examine the issues
and weigh in with rational solutions to this most terrible of
Mark L. Maiello Health Physicist Ossining, New
1. Hirsch, D. The NRC: What me worry? Bull. Atomic Scientists,
2. Leventhal, P. Nuclear power reactors are inadequately protected
against terrorist attack. Statement of Paul Leventhal on behalf
of the Nuclear Control Institute and Committee to Bridge the Gap,
before the House Committee on Energy and Commerce Subcommittee
on Oversight and Investigations, on A Review of Security
Issues at Nuclear Power Plants, Dec. 5, 2001; available
3. Project on Government Oversight. U.S. nuclear weapons complex:
Security at risk, Oct. 2001; www.pogo.org. Lasse Skarbøvik
4. Taubes, G. Whose nuclear waste? Technol. Rev., January/February
2002, pp. 60.67.
5. Von Hippel, F. Plutonium and reprocessing of spent nuclear
fuel. Science 2001, 293, 2397.2398. 6. Federation of American
Scientists. Closing the gaps: Securing highly enriched uranium.
FAS Public Interest Report, May/June 2002; available at www.fas.org.
[Author replies: I strongly endorse Dr. Maiello's recommendation
that physicists become actively engaged in helping to address
the security issues confronting our nation. We have an adversary
that is quite unlike any we have confronted before, and, as in
the past, I am confident that our best scientific minds can contribute
significantly in developing the policies and the means to protect
Let me comment on a few of the issues raised by Dr. Maiello.
Nuclear security has certainly not escaped the controversy that
generally surrounds nuclear issues. Although there has been criticism
of the NRC by some, significant progress has in fact been made.
The defenses at nuclear facilities are far more substantial than
those available at other critical infrastructure, and that security
has been significantly enhanced over the past year.
In the aftermath of the September 11 attacks, the NRC commenced
a comprehensive review of its policies and procedures relating
to security. As noted by Dr. Maiello, this review will include
a revision of the design basis threat against which our licensees
must prepare. Moreover, the inspection program is being revised
so as to provide force-on-force drills on a three-year cycle at
ever y plant rather than on the eight-year cycle that existed
in the past. These efforts have already commenced with the conduct
of table-top drills that, for the first time, have included extensive
involvement of state, local, and federal law enforcement officials.
Dr. Maiello notes that concerns have been expressed about the
fact that vulnerabilities have been found in past force-onforce
drills. Although the results are subject to different interpretations
from those he cites.the licensee success ratio on a drillby- drill
basis is far better than he indicates .the fact is that the drills
are hard and the NRC has been a hard grader. This should be reassuring
to the public and obviously undermines any claims that the NRC
is a "captive" of its licensees. Perhaps more important,
the NRC has required the correction of any defects in security
strategy that are revealed through these drills.
Dr. Maiello appropriately raises issues concerning a radiological
dispersal device (RDD). Although the health consequences of such
a device are not likely to be substantial, the use of an RDD could
have severe economic consequences and might cause great public
concern. As a result, the NRC has issued advisories to its materials
licensees and is conducting an evaluation of the controls governing
those materials that constitute the greatest hazard to public
health and safety. We are also working with the Office of Homeland
Security and other agencies to ensure that the federal government
is prepared for an event involving the use of an RDD.
I certainly agree with Dr. Maiello's observation that the terrorism
issue extends beyond one agency and one type of threat. Let me
also note, however, that the issues extend far beyond the nuclear
sector. Although there no doubt are improvements in security for
the nuclear plants that should be pursued, many threats are directed
at other sectors for which comparatively little has been done.
The defenses that exist to protect nuclear plants, for example,
are far more robust and comprehensive than those surrounding other
parts of our civilian infrastructure. Although I value thoughtful
input to address our nuclear vulnerabilities, I hope that your
readers will also consider and help address the many other terrorism
challenges that our nation faces.
Richard A. Meserve]