PHYSICS TODAY Research Articles

Gender matters: Cures for bias

Women in physics departments are an underrepresented population group and will likely continue to experience bias until they are seen as valuable assets rather than as a diversity issue needing to be rectified.11. B. M. Ferdman, B. R. Deane, eds., Diversity at Work: The Practice of Inclusion, Jossey-Bass/Wiley (2014), p. 5. Jennifer Blue, Adrienne Traxler, and Ximena Cid, the authors of “Gender matters” (Physics Today, March 2018, page 40), articulately identify and document biases against women in university physics departments. They suggest two solutions: Change the way women are welcomed into physics departments, and customize pedagogy to enable female physics students to succeed in physics careers. Although those solutions have been suggested for decades,22. “Physics departments explore innovative curriculum approaches,” APS News, August/September 1997, p. 2.,33. New England Consortium for Undergraduate Science Education, Achieving Gender Equity in Science Classrooms, Office of the Dean of the College, Brown University (June 1996). the biases persist.© LIGHTPOET/123rf.comPPT|High-resolutionThere may be another solution if biases exist because people have minimal positive experience with women as employees, researchers, and leaders and thus are stereotyping them rather than deliberately deciding against them. Ga-eun Seo and coauthors provide action steps women in physics can take to help replace those stereotypical beliefs.44. G. Seo, A. H. Mehdiabadi, W. Huang, J. Furth. High. Educ. 41, 741 (2017). https://doi.org/10.1080/0309877X.2016.1177167The focus of initiatives should be on realizing the benefits of diversity. Women can enrich a science team by bringing unique points of view, new ways of interpreting data, and creative ideas for approaching and solving problems.55. S. Ritchie et al., https://www.biorxiv.org/content/early/2018/01/22/123729. Increasing the presence of women scientists in physics departments could catapult physics beyond the current horizons and into a realm not yet imagined. I have been a high school physics teacher for the past 18 years, and I know that as female students transition to university physics departments, they need women there who can serve as role models.Rather than establish new department rules and new pedagogical methods, the bias cure may be to recognize the intrinsic value women can bring to physics departments and work with greater intensity to enroll them.ReferencesSection:ChooseTop of pageReferences <<1. B. M. Ferdman, B. R. Deane, eds., Diversity at Work: The Practice of Inclusion, Jossey-Bass/Wiley (2014), p. 5. Google Scholar2. “Physics departments explore innovative curriculum approaches,” APS News, August/September 1997, p. 2. Google Scholar3. New England Consortium for Undergraduate Science Education, Achieving Gender Equity in Science Classrooms, Office of the Dean of the College, Brown University (June 1996). Google Scholar4. G. Seo, A. H. Mehdiabadi, W. Huang, J. Furth. High. Educ. 41, 741 (2017). https://doi.org/10.1080/0309877X.2016.1177167, Google ScholarCrossref5. S. Ritchie et al., https://www.biorxiv.org/content/early/2018/01/22/123729. Google Scholar© 2018 American Institute of Physics.

Topological materials offer chemists a new experimental challenge

In 2008, Michael Ruck was frustrated. The inorganic chemist at Technical University Dresden was trying to figure out a way to build even smaller transistors than already existed, making nanowires of bismuth and nickel that were only four to 10 atoms thick. He had synthesized the wires and asked a colleague to measure their conductivity. Alas, the nanowires turned out not to conduct electricity as well as Ruck expected, rendering them useless as electronic circuits. He still doesn’t precisely know why the wires had such high resistance and therefore low conductance. But fortunately, he found a paper in Physics Today that offered a way to get around the limit on conductance, based on a theory that was then gaining currency. “I was very much disappointed until I read this paper,” he says. He already knew that at such small length scales, resistivity is mostly controlled by backscattering—a process in which

Readers’ thoughts on science and religion

I am a committed student of science and have been a member of the American Physical Society for 40 years. As a practicing applied physicist, I enjoy reading Physics Today and the weekly email alerts. I am also a practicing Christian, like William Newsome of Stanford University and Tom McLeish of Durham University.I have always claimed that if Physics Today is to remain open-minded to worldviews other than the ontological naturalist approach,11. See, for example, L. M. Krauss, “Cosmic humility,” APS News (April 2017), p. 8. it needs to consider other views such as those of Newsome, McLeish, and John Polkinghorne. Those scientists adhere to a Judeo-Christian worldview in the tradition of Michael Faraday, Johannes Kepler, James Clerk Maxwell, and others.You have finally done it. Thank you very much for publishing McLeish’s commentary “Thinking differently about science and religion” in your February 2018 issue.ReferenceSection:ChooseTop of pageReference <<CITING ARTICLES1. See, for example, L. M. Krauss, “Cosmic humility,” APS News (April 2017), p. 8. Google Scholar© 2018 American Institute of Physics.

Readers’ thoughts on science and religion

As a retired physics professor who has made the occasional foray11. G. L. Baker, Religion and Science: From Swedenborg to Chaotic Dynamics, Solomon Press (1992). into the topic of science and religion, I thank Tom McLeish for his civilized and hopefully civilizing approach to the discussion (“Thinking differently about science and religion,” Physics Today, February 2018, page 10). Center stage is too often dominated by militant atheists, willfully ignorant antiscience religionists, and cynical politicians who feed on the fears of a badly educated segment of the public. McLeish eloquently catalogs the harm done by the rabid nondialog from those groups.I believe there is a silent minority—at least—of capable academics who could bring their expert views to provide a much-needed elevation of the science and religion discussion. The task is daunting for those professionally involved in a single discipline, be it physics, biology, philosophy, theology, or other, but we need to step outside our comfort zone and take back the center ground of discourse on this important topic.ReferenceSection:ChooseTop of pageReference <<CITING ARTICLES1. G. L. Baker, Religion and Science: From Swedenborg to Chaotic Dynamics, Solomon Press (1992). Google Scholar© 2018 American Institute of Physics.

Readers’ thoughts on science and religion

Readers’ thoughts on science and religion

Physics Today ads track employment boom and bust

<em>Physics Today</em> ads track employment boom and bust

Biographical Memoir and Publications of Paul F. Zweifel

Paul Zweifel served as the founding editor of the Transport Theory and Statistical Physics journal from 1971 to 1981. An overview of his professional life gives a detailed list of his publications, broken down by his research interests, and also illustrates his leadership of the International Conference on Transport Theory meetings over the past 50 years. This paper provides supplementary material to the Paul Frederick Zweifel obituary published in Physics Today 70 (8):73 (2017); doi:10.1063/PT.3.3671.

Rosenfeld’s work on Fermi compilation

The obituary honoring Arthur Rosenfeld (Physics Today, September 2017, page 72) did not mention the very important contribution that he, together with Jay Orear and R. A. Schluter, made to the education of my generation of physicists. The trio compiled Enrico Fermi’s 1949 physics lectures from the University of Chicago into the book Nuclear Physics, originally published in 1949–50. Students at the time universally referred to it as Fermi’s Notes.A dense compilation of just about all the nuclear physics understood at the time—including a chapter each on nuclear reactors and cosmic rays—this modest and reasonably priced volume sparkles with the kind of physical insight said to be characteristic of Fermi’s style as a teacher.I remember one of its sample problems: An American car was shown to be tunneling quantum mechanically through a one-foot-high bump in the road. Would this be a solution to our crumbling roads? Not quite. The probability of that happening is not zero, but it is infinitesimally small! Section:ChooseTop of page <<© 2018 American Institute of Physics.

Physics and human rights

“In 1989 I had the privilege to travel to the International Center for Theoretical Physics at Trieste, Italy. Besides other things, I watched in the Italian television how the China government sent war tanks against the students in the Tiananmen Square. When I returned to Cuba, I discovered that all the Cuban media, totally controlled by the government, lied about what happened in Tiananmen.”The opening quote comes from the personal website of Texas Tech physicist Luis Grave de Peralta. The Cuban government’s whitewashing of the Tiananmen Square Massacre spurred him to resign from the Communist Party of Cuba, an action that cost him his job at the University of Santiago de Cuba. Out of work, he wrote a book critical of the Cuban government, an action that caused him to be sentenced in 1992 to 13 years in prison. Intervention on his behalf by the US National Academy of Sciences, Amnesty International, and Congressman Bill Richardson led to his release and expulsion to the US after he had spent nearly four years behind bars. At first, the Cuban government denied exit visas to his wife and two sons. They joined him in the US in 2008.On page 48 you’ll find a feature-length report by Physics Today’s Toni Feder on physics in Cuba. Despite economic hardship, physicists there do world-class research. A crucial element is Cuban physicists’ professional and economic ties to colleagues abroad. Strengthening those relationships is important. I’m glad that the American Physical Society and other professional organizations are working with that goal in mind. APS grants Cuban physicists free access to Physical Review Letters and its other journals.International scientific collaboration is virtuous, even with physicists who live under regimes that violate their citizens’ human rights. Two years ago, Feder wrote about a collaboration between geophysicists from France, the UK, and the US and a team from arguably the most politically oppressed country on Earth: North Korea. Brokered by the American Association for the Advancement of Science, the collaboration sought to evaluate the threat of an eruption by Mount Paektu, a volcano on North Korea’s border with China (see Physics Today, February 2016, page 20). On a boat in Russia in 1928 were (from left) Paul Dirac, Yakov Frenkel, and Alfred Landé. (Courtesy of the AIP Emilio Segrè Visual Archives.) PPT|High resolutionShould physicists discount human rights when weighing international collaborations? We are all entitled to set our own personal political limits, as Paul Dirac evidently did. Known for his single-minded devotion to theoretical physics, Dirac was also an enthusiastic traveler, especially to the Soviet Union. In his biography of Dirac, The Strangest Man (2009), Graham Farmelo describes the warm and fruitful interactions that Dirac had with Igor Tamm, Peter Kapitza, and other Russian physicists. Farmelo also noted that Dirac was likely ignorant of Joseph Stalin’s mass-murderous collectivization campaign of 1928–30 and his Great Purge of 1937–38.But there were limits to Dirac’s internationalism. To converse and collaborate with German physicists, Dirac had learned German. In 1933, after Hitler came to power and promptly began persecuting Jews and others, he vowed never to speak the language again. Section:ChooseTop of page <<CITING ARTICLES© 2018 American Institute of Physics.

Reconnecting reconnection with its current roots

The review by Jack Zirker and Oddbjørn Engvold (Physics Today, August 2017, page 36) of recent coronal research makes extensive use of the concept of field lines—in particular, magnetic reconnection. But like the analogous streamlines in fluids, magnetic field lines are not physical entities. They are just a convenient way of visualizing the structure and behavior of magnetic fields. To convince yourself of this, think of the familiar pattern of field lines connecting the poles of a bar magnet. How many lines are there?It follows that field-line reconnection itself is not a physical phenomenon and cannot cause either coronal heating or the propulsion of plasma in coronal mass ejection events. Such coronal phenomena result from dynamical processes involving electromagnetic fields, currents, and pressures, which are physical. Reconnection merely describes the way the magnetic field topology changes.As mentioned in the article, reconnection events are associated with thin current sheets, which are related to the magnetic field by Ampere’s law. Their evolution is fundamental to understanding coronal phenomena. Eric Priest and Terry Forbes (Zirker and Engvold’s reference 3) note that James Dungey, the originator of the reconnection model, “found that small perturbations in the vicinity of the null point lead to the explosive formation of a current sheet. Near the null point, plasma motions induced by a small current perturbation cause the current to grow, and this current further enhances the plasma motions resulting in a positive feedback.”11. E. Priest, T. Forbes, Magnetic Reconnection: MHD Theory and Applications, Cambridge U. Press (2000), p. 8. Focusing on the role that the currents play in reconnection would make for a clearer understanding.ReferenceSection:ChooseTop of pageReference <<1. E. Priest, T. Forbes, Magnetic Reconnection: MHD Theory and Applications, Cambridge U. Press (2000), p. 8. Google ScholarCrossref© 2018 American Institute of Physics.

Magnetic monopoles and a cheap detector

The letters from Ken Frankel and Christopher Harrison (Physics Today, June 2017, page 13) in response to Arttu Rajantie’s article on the history of searches for magnetic monopoles (Physics Today, October 2016, page 40) brought back a memory. After Blas Cabrera’s 1982 publication of a candidate monopole event detected with a superconducting loop,11. B. Cabrera, Phys. Rev. Lett. 48, 1378 (1982). https://doi.org/10.1103/PhysRevLett.48.1378 three groups22. J. Incandela et al., Phys. Rev. Lett. 53, 2067 (1984); https://doi.org/10.1103/PhysRevLett.53.2067S. Bermon et al., Phys. Rev. Lett. 55, 1850 (1985); https://doi.org/10.1103/PhysRevLett.55.1850A. D. Caplin et al., Nature 317, 234 (1985); https://doi.org/10.1038/317234a0S. Somalwar et al., Nucl. Instrum. Methods Phys. Res. A 226, 341 (1984). https://doi.org/10.1016/0168-9002(84)90046-9—a University of Chicago, Fermilab, and University of Michigan collaboration; IBM; and Imperial College London—built Faraday induction detectors with larger areas. Using a coincidence technique of two gradiometer detectors in a nonzero but pinned magnetic field, Joe Incandela and coworkers showed that a likely explanation of the candidate event was a flux jump rather than the transit of a monopole.33. J. Incandela et al., Phys. Rev. D 34, 2637 (1986); https://doi.org/10.1103/PhysRevD.34.2637J. R. Incandela, “A search for magnetic monopoles using superconducting induction detectors,” PhD thesis, U. Chicago (1986). I was invited by the organizers of the First Aspen Winter Conference to give a review talk of the hot though cryogenic topic.44. H. J. Frisch, Ann. NY Acad. Sci. 461, 652 (1986). https://doi.org/10.1111/j.1749-6632.1986.tb52444.xI had been a graduate student at the University of California, Berkeley, and had great admiration for Luis Alvarez, so I sent him a draft asking for comments. I had leaned over backwards to give him credit for inventing the Faraday induction technique, as my looking in depth at monopole detection by ionization brought home that there was no way to calibrate the ionization detector, and hence a nondetection could never be definitive. Faraday detection, however, can be calibrated with a “pseudopole,” a very long but small-diameter, tightly wound, magnetic solenoid much akin to a Dirac string.I was working at my desk when my phone rang, with a furious Luis on the other end. Without any introduction, he barked, “Henry, this was my idea, and I should be the first reference.” I was stunned, as I thought I had done him proud, but I managed to say, “Luis, the guys ahead of you are not to be sneezed at—Faraday, Maxwell, Dirac… .” Still angry, he said, “Yes, but who are these other guys?” Luis later sent a nice note praising the review, and all was well.A brief addendum: Sunil Somalwar’s PhD thesis followed up on Incandela’s superconducting gradiometers by showing that using just copper wire and a field-effect transistor operating at liquid nitrogen temperature, one could build an inexpensive detector, capable of covering large areas and sensitive to a single Dirac charge.55. S. Somalwar, H. Frisch, J. Incandela, Phys. Rev. D 37, 2403 (1988). https://doi.org/10.1103/PhysRevD.37.2403ReferencesSection:ChooseTop of pageReferences <<1. B. Cabrera, Phys. Rev. Lett. 48, 1378 (1982). https://doi.org/10.1103/PhysRevLett.48.1378, Google ScholarCrossref2. J. Incandela et al., Phys. Rev. Lett. 53, 2067 (1984); https://doi.org/10.1103/PhysRevLett.53.2067, Google ScholarCrossrefS. Bermon et al., Phys. Rev. Lett. 55, 1850 (1985); https://doi.org/10.1103/PhysRevLett.55.1850, , Google ScholarCrossrefA. D. Caplin et al., Nature 317, 234 (1985); https://doi.org/10.1038/317234a0, , Google ScholarCrossrefS. Somalwar et al., Nucl. Instrum. Methods Phys. Res. A 226, 341 (1984). https://doi.org/10.1016/0168-9002(84)90046-9, , Google ScholarCrossref3. J. Incandela et al., Phys. Rev. D 34, 2637 (1986); https://doi.org/10.1103/PhysRevD.34.2637, Google ScholarCrossrefJ. R. Incandela, “A search for magnetic monopoles using superconducting induction detectors,” PhD thesis, U. Chicago (1986). , Google Scholar4. H. J. Frisch, Ann. NY Acad. Sci. 461, 652 (1986). https://doi.org/10.1111/j.1749-6632.1986.tb52444.x, Google ScholarCrossref5. S. Somalwar, H. Frisch, J. Incandela, Phys. Rev. D 37, 2403 (1988). https://doi.org/10.1103/PhysRevD.37.2403, Google ScholarCrossref© 2018 American Institute of Physics.

Energy efficiency in motion and thought

Simon Sponberg’s article (Physics Today, September 2017, page 34) addresses important topics in the physics of insect locomotion in terms of muscle motion, sensing, and information processing. However, one especially important and astonishing aspect of physics, common to living objects and unattainable by manmade machines, is the energy efficiency in both muscle motion and information processing. One impressive example is the energy consumed by the human brain in playing Go or chess with a supercomputer. Although humans now lose both games, the energy consumed by the human brain while playing is five to six orders of magnitude less than that of the supercomputer.11. See, for example, Y. Yanagida, Y. Ishii, Proc. Japan Acad. B 93, 51 (2017). https://doi.org/10.2183/pjab.93.004ReferenceSection:ChooseTop of pageReference <<1. See, for example, Y. Yanagida, Y. Ishii, Proc. Japan Acad. B 93, 51 (2017). https://doi.org/10.2183/pjab.93.004, Google ScholarCrossref© 2018 American Institute of Physics.

The problem of the electron’s mass

As I read “An electron–proton collider could bridge the gap between the LHC and its successor” (Physics Today, May 2017, page 29) and how it would serve in high-precision studies of Higgs decays as a portal to new physics, I was disappointed. I saw no mention of a long-standing problem in connection with the electron: What fraction of the electron’s mass is due to its interaction with the quantized electromagnetic field? Despite its enormous success in quantum electrodynamics, renormalization does not solve the problem, nor does it even tell us how to tackle it. Furthermore, the Higgs contribution to the electron’s mass is unknown. We also don’t know how to measure those respective contributions. Perhaps in thinking about the electron–proton collider, one should be thinking about opening portals to these long-neglected areas as well. Section:ChooseTop of page <<© 2018 American Institute of Physics.

Paradise as a kind of library

“Professor Kittel has succeeded admirably in his purpose, announced in the preface, of producing a textbook suitable for an introductory course in the subject of solid state physics for seniors and graduate students.”Thus began Physics Today’s review of the first edition of Charles Kittel’s textbook, Introduction to Solid State Physics, which appeared in August 1954. The reviewer was Joseph Masi, the head of physical chemistry at the Callery Chemical Company, which I’m happy to report is still in business. A selection of books sent by publishers for review at Physics Today. CYNTHIA CUMMINGSPPT|High resolutionOther famous books have been reviewed in the pages of Physics Today. In the August 1974 issue, you’ll find Subrahmanyan Chandrasekhar’s review of the first edition of Gravitation by Charles Misner, Kip Thorne, and John Wheeler. The review includes the prescient quote, “The part on gravitational waves is a most useful one, particularly in the enumeration of the astronomical sources of gravitational waves and the means of detection that are available.” Back in 1974, the book cost $39.50 in hardcover, which is $195 in 2018 dollars. Today it retails on Amazon for $54.Banesh Hoffmann, in the January 1983 issue, was the reviewer of Abraham Pais’s “Subtle Is the Lord . . .”: The Science and the Life of Albert Einstein. Hoffmann was especially qualified to review the book. A general relativist, he not only had collaborated with Einstein, but had also written, with Helen Dukas, the book, Albert Einstein: Creator and Rebel, which was reviewed in Physics Today in April 1973 by another Einstein collaborator, Peter Bergmann. Despite being a rival Einstein biographer, Hoffmann was effusive in his praise of Pais’s book: “Here is an outstanding biography of Albert Einstein that one finds oneself reading with sheer pleasure.”Book reviews have appeared in every issue of Physics Today since the magazine’s debut in May 1948. I’m determined that they should remain, and not just because I’m a bibliophile. Few other magazines review books written expressly for physicists and their professional relatives.Evidence of our commitment to books appears in two places in this issue. On page 10, Physics Today’s former Books editor Jermey Matthews contributes a Readers’ Forum Commentary entitled “It’s the 21st century. Why are scientists still writing books?” On page 53, you’ll discover that the Books department has been revamped. As usual, four solicited reviews of new and notable books form the core of the department. But instead of a list of books received, you’ll find capsule reviews of four books and one documentary. You’ll also notice that the department has an attractive new look.Even in this short piece about books and Physics Today, it would be remiss not to mention Freeman Dyson’s contributions to the department. His first review, of John Blatt and Victor Weisskopf’s Theoretical Nuclear Physics, appeared in March 1953. His 20th, of Roald Hoffmann’s The Same and Not the Same, appeared in January 1996.On behalf of Physics Today’s current Books editor, Melinda Baldwin, and all her predecessors, I thank Dyson and everyone who has written a review for the magazine. And in case you’re wondering, this editorial’s title comes from a poem by Argentine writer and bibliophile Jorge Luis Borges: “I have always imagined Paradise as a kind of library.” Section:ChooseTop of page <<CITING ARTICLES© 2018 American Institute of Physics.

Commentary: It’s the 21st century. Why are scientists still writing books?

Commentary: It’s the 21st century. Why are scientists still writing books?

Improving undergraduate labs

The April 2017 issue of Physics Today included a report by Toni Feder on the current poor state of student advanced physics labs and efforts by the Advanced Laboratory Physics Association to improve the situation. But a few aspects need discussion to complete our understanding of the situation.Some colleges advertise that all their undergraduates have the opportunity to participate in faculty research projects. I wonder whether such arrangements are an attempt to compensate for poor or nonexistent advanced labs.As the US population ages, an increasing share of federal revenue will go for Social Security and health care benefits. Less money will be available for discretionary federal spending, such as for student lab equipment, so petitioning NSF for funds is not promising. Physics teachers should be petitioning their own universities to make some tuition money available for that purpose.The typical department budget for lab equipment and supplies is approximately $1000, according to the report. If the college charges $30 000 annual tuition, why not use $1000 of that to upgrade lab equipment? If 20 students took the lab each year, that lab would receive $20 000, which should be enough to pay for one new or refurbished experiment set-up. If we assume student pairs rotated through 10 experiments and that each required only one apparatus set, after 10 years all experiments would be upgraded or refurbished!The article reports complaints about century-old lab experiments. Yet there is nothing wrong with letting students perform a few classic experiments such as the Millikan oil drop, the Michelson interferometer, or the Franck–Hertz tube. Recent Physics Today pieces (July 2016, pages 8 and 38; March 2017, page 11) have suggested that students should learn the history of physics. Doing classic experiments allows students to experience using simpler equipment and getting meaningful results without using computerized black boxes. I never appreciated how hard it is to measure the universal constant of gravitation G until I used a Cavendish balance.Feder reports that new professors are reluctant to get involved with maintaining student lab equipment because such activity does not contribute to obtaining tenure. Perhaps we need a reform of the tenure process so that ratings include those activities that directly help undergraduate students. For their tuition dollars, students should be getting good laboratory training.In a separate editorial (Physics Today, June 2016, page 8), Charles Day commented that the student labs he took did not inspire him to become an experimental physicist. I think his complaint is invalid. Student labs are not recruiting events for the field but training sessions that should Teach some laboratory techniques and practices. Give experience in analyzing real-world data whose error distribution does not follow a Gaussian distribution. Observe physics phenomena firsthand. Verify firsthand that some textbook theory is borne out by experiment. Allow one to learn some physics topics not covered in other courses. As demonstrated by the effort required to become proficient at playing a musical instrument, learning a craft is hard work, and not all of it is inspiring.[Editors’ note: Some of the issues Victor Slabinski mentions are also discussed in the feature article “Introductory physics labs: We can do better” by Natasha Holmes and Carl Wieman on page 38 of this issue.] Section:ChooseTop of page <<© 2018 American Institute of Physics.

Tales of the Soviet hydrogen bomb

I was one of a very few non-Russian and non-US participants at the fascinating History of the Soviet Atomic Project conference held in May 1996 at the Joint Institute for Nuclear Research in Dubna, north of Moscow. The article “The secret of the Soviet hydrogen bomb” by Alex Wellerstein and Edward Geist (Physics Today, April 2017, page 40) brings up many memories from that meeting.After arriving home from the conference, I wrote an article about it for my institute’s magazine. I think a few details and reflections from that article are worth adding to the international record. They mainly derive from my discussions with Arnold Kramish, a Manhattan Project veteran whom I got to know well during the Dubna meeting and through letters exchanged in the years before his death.After the war Kramish had worked for the US Atomic Energy Commission as a liaison to the Central Intelligence Agency; he provided intelligence estimates on Soviet nuclear capabilities. Shortly before the Teller–Ulam idea was born in early 1951, he had passed on to Stanislaw Ulam intelligence material about Soviet experiments in which extremely strong magnetic fields had been used to compress fusion materials. That information had come from repatriated Austrian physicist Josef Schintlmeister, who, as a victim of the Soviet Alsos operation, was forced to work on the Soviet atomic bomb project and then got insight into work by Peter Kapitza and Andrei Sakharov. Kramish strongly believed that the information Schintlmeister had gathered was the seed of Ulam’s idea of arranging extreme compression of thermonuclear fuel by a physically distinct primary fission charge. Add to that Edward Teller’s idea to employ radiation implosion and the now classical hydrogen bomb was conceived.However, as mentioned in the Wellerstein and Geist article, the concept of radiation implosion stems from a patent filed by Klaus Fuchs and John von Neumann at Los Alamos in May 1946. Fuchs then, like all other British participants in the Manhattan Project, had to go back to the UK in June 1946.Did Fuchs provide the radiation implosion idea to the Soviets? Yes he did, according to former Soviet intelligence chief Vladimir Barkovsky, who spoke at the Dubna meeting. He had collected the documents from Fuchs in London on 13 March 1948; during his talk Barkovsky even showed sketches of the patent. In conversation during the conference banquet, he also said that he thought Fuchs, back in Washington, DC, in 1947 or 1948 for a meeting about UK and US cooperation on nuclear weapons, had gotten new material from an unknown messenger.It is ironic that the development of the H-bomb actually proceeded in a kind of behind-the-scenes de facto cooperation between the two nuclear powers at the time, the US and the Soviet Union. While both nations were struggling to develop thermonuclear weapons, they didn’t realize that the three most important components—compression, staging, and radiation implosion—were already available to be put together. The breakthrough was delayed in the US by Teller’s long inability to give up his belief in his baby, the Classical Super; and in the Soviet Union, by Sakharov’s preoccupation with his baby at the time, the Sloika.A final note on the inflamed relationship between Stan Ulam and Teller: Kramish told me that right after the new H-bomb idea had been conceived, Teller called for a meeting to discuss it. He asked Kramish to take part, and then, after a short pause, Teller added, “Don’t tell Stan!” Section:ChooseTop of page <<CITING ARTICLES© 2018 American Institute of Physics.

Improving undergraduate labs

Toni Feder’s news story “Undergraduate labs lag in science and technology” (Physics Today, April 2017, page 26) is a welcome analysis of the challenges facing advanced undergraduate physics laboratories and current efforts to provide effective solutions for undergraduate physics programs at US colleges and universities.The Advanced Laboratory Physics Association (ALPhA) sponsors a laboratory immersion program in which physics faculty receive three days of dedicated instruction and hands-on experience with modern advanced undergraduate physics experiments. The goal is to provide enough training so that participants can implement the experiments at their own institutions.Since the inception of the program, I have participated in nine immersions. Each was excellent, and I have implemented at least one experiment—and in one case, five—from each immersion I attended. The topics have been fascinating, and they included single-photon tests of quantum mechanics, external-cavity diode lasers, laser-induced fluorescence, Compton scattering, precision laser interferometry, Fourier methods, and saturated absorption spectroscopy.At my small undergraduate institution—10 physics majors per year on average—the primary obstacle I faced in implementing those experiments was locating funds to purchase the equipment. Fortunately, the Jonathan F. Reichert Foundation started the ALPhA immersions equipment grant program, which has been a godsend to me and my students. Its support has allowed me to acquire a Leybold x-ray diffraction apparatus, a TeachSpin diode laser spectroscopy instrument, a Stanford Research lock-in amplifier, and a TeachSpin Fourier Methods system.As a direct result of the efforts of ALPhA and the Reichert Foundation, I have implemented 13 advanced undergraduate physics experiments at my institution. Additionally, I proposed a new course, Advanced Laboratory in Physics, which was offered for the first time in the fall of 2017.Some friends and colleagues suggest that after 30 years of professorial experience I should be thinking about retiring. I disagree. I am more excited now than ever, because I see my students’ enthusiasm as they perform the new experiments. I look forward to many more years in the best job on the planet. Section:ChooseTop of page <<© 2018 American Institute of Physics.

The Concept of the Photon—Revisited

concept is one of the most debated issues in the history of physical science. Some thirty years ago, we published an article in Physics Today entitled The Concept of the Photon, 1 in which we described the photon as a classical electromagnetic field plus the fluctuations associated with the vacuum. However, subsequent developments required us to envision the as an intrinsically quantum mechanical entity, whose basic physics is much deeper than can be explained by the simple 'classical wave plus vacuum fluctuations' picture. These ideas and the extensions of our conceptual understanding are discussed in detail in our recent quantum optics book. 2 In this article we revisit the concept based on examples from these sources and more.

The most popular Physics Today articles of 2017

Two of the top five stories addressed the personal side of pursuing a career in the physical sciences.