bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear Matter in Extremis Sought with Ultrarelativistic Heavy-Ion Beams
Authors: Schwarzschild Bertram
Published: January 2008

Last summer's Quark Matter '87 conference, at Schloss Nordkirchen near Dortmund, was the sixth in a series of quasiannual gatherings of physicists interested in extended nuclear matter under extreme conditions of density and temperature. But it was the first that had significant data to chew on. At sufficiently high energy densities, it is confidently believed, we will reach the Holy Grail—the phase transition from ordinary nuclear matter to the “quark-gluon plasma.” (See PHYSICS TODAY, March 1985, page 40.) The experimental method of choice is to bang heavy nuclei together at the highest possible collision energies. Before September 1986 the best one could do (aside from examining a handful of spectacular cosmic-ray events) was to accelerate uranium ions to a modest 1 GeV per nucleon at the Berkeley Bevalac and fire them at a uranium target.
Nucleon Correlations Seen in Pion Double Charge-Exchange Reactions
Authors: Levi Barbara Goss
Published: January 2008

The position of one nucleon in a nucleus is assumed to affect the location of another, but such spatial correlations are hard to demonstrate. Many hoped they would appear in pion double charge-exchange reactions once the meson factories were built in the 1970s. Unfortunately, any correlations were masked by other complex interactions at the normal operating energies of the meson factories. Only recently—in new data taken at energies as low as 35 MeV—have nucleon correlations begun to surface. They show up in pion double charge exchange because these reactions necessarily involve two nucleons: The ingoing positive pion has successive charge-exchange scatterings with two neutrons in a nucleus, changing them into protons in the process. At low energies the cross sections for pion double charge-exchange transitions to certain states are larger than expected, and they are peaked in the forward direction. Theorists have explained these features and others in terms of nucleon correlations. Their work indicates that the pion interacts with two valence nucleons outside a closed shell that are within one femtometer (about a proton radius) of each other.
Super Collider Magnet Program Pushes Toward Prototype
Authors: Levi Barbara Goss , Schwarzschild Bertram
Published: January 2008

The most, expensive component of the proposed multi-billion-dollar Superconducting Super Collider is the double ring of nearly 8000 17-meterlong superconducting bending magnets required to hold its countercirculating beams of 20-TeV protons in their 52-mile course. Thus the magnet program will soon undergo particular scrutiny as Congress begins to consider the President's request for $363 million in fiscal 1989 for firstyear SSC construction and continuing R&D. Some parts of the magnet program, such as the development of the superconducting cable, the cryogenic system and the achievement of good dipole-field quality, have been extremely successful.
Numerical Simulations Reveal Fluid Flows Near Solid Boundaries
Authors: Khurana Anil
Published: January 2008

A thin layer of dust is not blown off the blades of a fan when the fan is turned on; only large dust particles are. Nor can one remove the fine layer of dust from a tabletop by blowing parallel to the table's surface. Richard Feynman, in his famous lectures on physics, used these examples to illustrate that in the relative motion of a viscous fluid past a solid, the component of the fluid velocity along the solid surface vanishes at the solidfluid interface. Recent molecular dynamics simulations by a group at Schlumberger-Doll Research (Ridgefield, Connecticut) elucidate the nature of fluid flows near a solid boundary, and especially near the line where the meniscus (or interface) between two fluids meets the solid boundary.
Space Science in the United States
Authors: Alexander Joseph K. , McDonald Frank B.
Published: January 2008

Space research began as an exploratory endeavor, representing a natural evolution of science in which new opportunities were exploited and new capabilities were developed. The exploratory disciplines that originated with these early efforts, such as space physics, Earth remote sensing, planetary science and astronomy, have evolved and matured. They remain, in one way or another, fields that one might collectively describe as the science of space. On the other hand, several new disciplines that pertain to the pursuit of science in space are still in the early, developmental phase. These “microgravity sciences” involve investigations into basic physical, chemical and biological processes in very low gravity. Although research in these fields once possessed a certain Edisonian character—“let's try it and see what happens”—one now can see strong signs of sharpening scientific focus, maturing experimental capability and the promise of important scientific impact.
Rayleigh-Bénard Experiment Probes Transition from Chaos to Turbulence
Authors: Khurana Anil
Published: January 2008

Progress in understanding chaos—actually, temporal chaos—has been enhanced over the past ten years by the close agreement between some experiments and the theoretical descriptions of chaotic behavior. Our understanding of turbulence is not yet at the same level. However, a group led by Albert Libchaber at the University of Chicago has recently characterized with great accuracy turbulent flows in a Rayleigh-Bénard cell. The Rayleigh-Bénard experiment studies convective flows in a fluid that is confined in a gravitational field between two parallel horizontal plates and heated from below. Earlier experiments on this system by Libchaber, among others, played an important role in our understanding of chaos.
Ozone Depletion at the Poles: The Hole Story Emerges
Authors: Levi Barbara Goss
Published: January 2008

Last August, in the dark of the Antarctic winter, more than 100 scientists descended to the southern tip of the globe, some to monitor the stratosphere from airplanes flying high above Antarctica, others to sample it with balloons and remote sensing equipment from ground stations on the continent. The massive assault was an urgent effort to determine the cause of the ozone hole—the depletion of ozone in the lower stratosphere that has occurred with increasing severity each spring since the mid-1970s. After analyzing their data, these scientists reconvened last May in Snowmass, Colorado, to present for the first time all the details of their findings. The extensive new data leave no doubt that man-made chlorofluorocarbons are primarily responsible for the ozone hole. They elucidate more clearly than ever before the unique wintertime meteorological conditions that allow chlorine compounds from these CFCs to destroy virtually all the ozone in the lower stratosphere over the Antarctic: The ice clouds that form in the dry, frigid stratosphere seem to facilitate chemical reactions that free chlorine atoms from those compounds in which they are normally trapped. The freed chlorine atoms can then ravage the ozone. Although this general hypothesis was gaining wide support even before the recent expedition, the new data put it on firmer grounds and allow the specialists to start filling in the details.
From Mine Shafts to Cliffs—The ‘Fifth Force’ Remains Elusive
Authors: Schwarzschild Bertram
Published: January 2008

Is there really a “fifth force”? Since Purdue particle theorist Ephraim Fischbach and his colleagues dusted off the 80-year-old data of Roland von Eötvös three years ago, pointing out that this classic test of the equivalence principle hinted that all was not well with Newtonian gravity, a broad array of physicists have been investigating the possible existence of a force weaker than gravity, with a finite macroscopic range. A lonely band of geophysicists had been gathering evidence of such a force in Australian mine shafts since 1981. (See PHYSICS TODAY, October 1986, page 17.) But the jury is still out.
CERN Experiment Clarifies Origin of CP Symmetry Violation
Authors: Schwarzschild Bertram
Published: January 2008

Experimental and theoretical floodgates were opened in 1957 by the discovery that parity inversion (P) and charge conjugation (C) are not among nature's elite of inviolate symmetry transformations. By contrast, the even more surprising discovery of CP violation seven years later has been something of a disappointment. In the quarter-century since James Cronin, Val Fitch, James Christenson and Rene Turlay at Princeton discovered that the decay of neutral K mesons is not precisely invariant under the combined operations of parity inversion and charge conjugation, CP violation has been seen in no other physical system. Nor have the experimenters been able to clarify the mechanism underlying this exotic asymmetry of the elementary particles.
HERA Stores Its Frist Beam
Authors: Schwarzschild Bertram
Published: January 2008

HERA, the world's first electron-proton storage-ring collider, successfully stored its first electron beam on 20 August. The 6-km-circumference accelerator is nearing completion at the DESY (Deutsches Elektronen-Synchrotron) laboratory in Hamburg. In this first trial, a circulating beam of some 3 billion 7-GeV electrons was maintained in the ring for two minutes. When physics experiments begin at HERA in 1990, countercirculating beams of 30-GeV electrons and 820-GeV protons will produce e-p collisions with center-of-mass energy of 314 GeV.
Voyager Visits Uranus and Observes Rings and Moons
Authors: Schechter Bruce
Published: January 2008

Last January, having survived the hazards of interplanetary space, previous close encounters with Jupiter and Saturn, four Administrations and numerous budget cycles, Voyager 2 passed within 107 000 kilometers of the planet Uranus. The data collected on its historic flyby took 2 hours and 45 minutes to reach radiotelescopes on Earth, 2.8 billion kilometers away. And while the aptly named Voyager coasts off to an encounter with Neptune and its large moon Triton in August of 1989, the Voyager scientists will be busy analyzing their precious data for clues to the origin and evolution of the Uranian system. In January of 1987 the world's scientific community will be granted full access to the Voyager 2 Uranus data. Until then they will have to be satisfied with the Voyager team's preliminary conclusions, which were published last month.
Laser Beam Focus Forms Optical Trap for Neutral Atoms
Authors: Schwarzschild Bertram
Published: January 2008

The first color photographs ever to grace the pages of Physical Review Letters show us the fluorescent glow from some 500 sodium atoms caught in the first successfully demonstrated optical trap for neutral atoms. The 21 July Letter by Steven Chu, John Bjorkholm, Arthur Ashkin and Alex Cable at Bell Labs, reports that this tiny “optical dipole” trap, formed at the focus of a single laser beam, was able to hold onto an ultracold, high-density accumulation of atoms for several seconds and manipulate them in space. In recent days the group has been able to hold a much larger collection of sodium atoms for a fraction of a minute with a newer optical-trap design.
Ion orbits in plasma etching of semiconductors
Authors: Madziwa-Nussinov Tsitsi G. , Arnush Donald , Chen Francis F.
Published: January 2008

Fabrication of high-speed semiconductor circuits depends on etching submicron trenches and holes with straight walls, guided by sheath accelerated ions, which strike the substrate at a normal angle. Electrons accumulate at the nonconductive entrance of each trench, charging it negatively and preventing the penetration of electrons to the bottom of the trench. This “electron shading” effect causes an ion charge at the bottom, which is well known to cause damage to thin oxide layers. In addition, the deflection of ions by electric fields in the trench can cause deformation of the trench shape. To study this effect, the ion orbits are computed self-consistently with their charging of the trench walls. It is found that (a) the orbits depend only on the electric fields at the entrance and are sensitive to changes in the shape of the photoresist layer there; (b) there is an “ion shading” effect that protects part of the wall; and (c) the number of ions striking the wall is too small to cause any deformation thereof.
Noise thermometry and electron thermometry of a sample-on-cantilever system below 1Kelvin
Authors: Bleszynski-Jayich A. C. , Shanks W. E. , Harris J. G. E.
Published: January 2008

We have used two types of thermometry to study thermal fluctuations in a microcantilever-based system below 1K. We measured the temperature of a cantilever’s macroscopic degree of freedom (via the Brownian motion of its lowest flexural mode) and its microscopic degrees of freedom (via the electron temperature of a metal sample mounted on the cantilever). We also measured both temperatures’ response to a localized heat source. We find that it is possible to maintain thermal equilibrium between these two temperatures and a refrigerator down to at least 300mK. These results are promising for ongoing experiments to probe quantum effects using micromechanical devices.
A sequential logic device realized by integration of in-plane gate transistors in InGaAs∕InP
Authors: Sun Jie , Wallin Daniel , He Yuhui , Maximov Ivan , Xu H. Q.
Published: January 2008

An integrated nanoelectronic circuit is fabricated from a high-mobility In0.75Ga0.25As∕InP heterostructure. The manufactured device comprises two double in-plane gate transistors with a current channel of 1.1μm in length and 100nm in width. The two transistors are coupled to each other in a configuration that the source of one transistor is directly connected with one in-plane gate of the other transistor. Electrical measurements reveal that this device functions as an SR (set-reset) latch (a sequential logic device) with a gain of ∼4 in the logic swing at room temperature. The demonstrated device provides a simple circuit design for SR latches.
Ions motion effects on the full unstable spectrum in relativistic electron beam plasma interaction
Authors: Bret A. , Dieckmann M. E.
Published: January 2008

A relativistic fluid model is implemented to assess the role of the ions motion in the linear phase of relativistic beam plasma electromagnetic instabilities. The all unstable wave vector spectrum is investigated, allowing us to assess how ion motions modify the competition between every possible instability. Beam densities up to the plasma one are considered. Due to the fluid approach, the temperatures must remain small, i.e., nonrelativistic. In the cold limit, ions motion affect the most unstable mode when the beam gamma factor γb≳αM∕mZi, α being the beam to plasma density ratio, Zi the ion charge, M their mass, and m the electrons. The return current plays an important role by prompting Buneman-type instabilities which remain in the nonrelativistic regime up to high beam densities. Nonrelativistic temperatures only slightly affect these conclusions, except in the diluted beam regime where they can stabilize the Buneman modes.
Depth sectioning of individual dopant atoms with aberration-corrected scanning transmission electron microscopy
Authors: Xin Huolin L. , Intaraprasonk Varat , Muller David A.
Published: January 2008

The ability to detect individual impurity atoms has been greatly enhanced by the development of aberration-corrected electron microscopes. The reduced depth of focus potentially enables three-dimensional reconstructions of impurity atoms from through-focal series. We test the robustness of this depth-sectioning method for detecting impurity atoms in gate oxides using multislice simulations. For amorphous materials, dopants can be reliably imaged, and are accurately described by a simpler three-dimensional linear imaging model. For crystalline materials, however, channeling artifacts can render the signal uninterpretable. These artifacts can be eliminated by orienting the crystal slightly off the zone axis, which still preserves atomic resolution.
The Weak Interactions From Now On
Authors: Weinberg Steven
Published: January 2008

We like to think of physics as moving toward unity, but at any one moment it is fragmented into specialties, which sometimes seem even to define different scientific personalities. This certainly appeared to be the case when I arrived in Palmer Lab at Princeton University as a new graduate student just 30 years ago. Physicists who worked on strong and weak interactions seemed to me to be very different sorts of animals, differentiated especially by the quantity and nutritional value of the data on which they fed.
Giant Resonances in Hot Nuclei
Authors: Bertsch George F. , Broglia Ricardo A.
Published: January 2008

Nuclei interact with the external environment through a number of different fields—electromagnetic, weak and hadronic. The collective excitations induced by these interactions are known as giant resonances. The best-known example is the giant dipole resonance, which is stimulated when the electric field of an incident gamma ray exerts a force on the positively charged protons in a nucleus, moving them relative to the uncharged neutrons (see figures 1 and 2). Other giant resonances that have been studied are the monopole, quadrupole and spin-isospin modes of oscillation. The spin-isospin mode involves charge-changing processes, in particular beta decay. The quadrupole and monopole giant resonances are most easily seen with fields that act equally on neutrons and protons, because in these modes the neutrons and protons oscillate in the same mode.
The Plasma Universe
Authors: Alfvén Hannes
Published: January 2008

For millennia we have based our views of the universe on observations in the narrow visual octave of the electromagnetic spectrum, 400–800 nm, supplemented during the last half-century by infrared and radio observations. During the last decade, however, space research has opened the full spectrum, including the entire infrared region and the ultraviolet, x-ray and γ-ray regions (see the photo on the cover and figure 1).
Maria Goeppert Mayer: Atoms, Molecules and Nuclear Shells
Authors: Johnson Karen E.
Published: January 2008

Maria Goeppert Mayer is frequently mentioned as an example of a woman who managed to make significant contributions to science in spite of tremendous obstacles. Robert Sachs, Mayer's first graduate student, has given a personal account of her life and career (PHYSICS TODAY, February 1982, page 46). Joan Dash has written a longer biography of Mayer, focusing on her family life. In this article I look at the distinctive character of Mayer's scientific accomplishments. As a mathematical physicist, she worked on a number of apparently unrelated topics during the years 1930–46. I will focus on her work during this period and show how it prepared her for the nuclear physics research for which she received the Nobel Prize in 1963.
Policy Challenges Facing the US Space Research Program
Authors: Lanzerotti Louis J. , Rosendhal Jeffrey D.
Published: January 2008

In a companion article in this issue (page 56), Joseph K. Alexander and Frank B. McDonald discuss the current state of space research in the United States, some of the changes that are taking place in the US space science program and the contributions that the space sciences have made to addressing a wide variety of scientific questions. Based on these accomplishments, the space research community has developed an ambitious menu of possible new initiatives for the end of this century and beyond. But describing scientific dreams, identifying trends and carrying out elaborate planning studies to define and choose new missions will constitute purely intellectual exercises unless both NASA management and the scientific and engineering communities take specific actions to improve program implementation. Also, the need for a stable policy that leads to orderly planning and execution of such programs must be recognized by the executive and legislative bodies that formulate and approve both the plans for space research and their budgets.
The Physicist as Mad Scientist
Authors: Weart Spencer
Published: January 2008

A crazed scientist with a deadly “atomic robot” set out to enslave the human race in a recent Saturday morning cartoon show. He was no exception: Unstable scientists plotting to master and destroy can be found almost anywhere one looks in children's television and comics—and in a surprising amount of adult fiction as well. Probably no other profession is so consistently drawn upon for storybook villains. To many people, then, the words “nuclear physicist” bring to mind a weird and evil picture.
Local Structural Order in Amorphous Semicondcutors
Authors: Lannin Jeffrey S.
Published: January 2008

Noncrystalline condensed matter presents contemporary physics with a number of basic questions. Traditional solid-state physics has emphasized the study of periodic systems, whose energy levels may be labeled by the wavevector. The concept of reciprocal space, or of allowed wavevector values, therefore provides a convenient and consistent framework for describing electronic, vibrational and magnetic properties of crystalline solids in terms of energy bands. In a nonperiodic system, the concept of a wavevector is not valid. The need for a fundamental concept that might be useful in the study of nonperiodic systems therefore forces us to focus attention on structural configurations in real space.
Chandrasekhara Venkata Raman
Authors: Jayaraman Aiyasami , Ramdas Anant Krishna
Published: January 2008

The year 1988 marks the centennial of the birth of C. V. Raman, the discoverer of the effect that bears his name. During his extraordinarily creative career, which spanned more than six decades, he had a profound impact on the scientific world. He made significant contributions to acoustics, physical optics, magnetism and molecular physics, including, of course, his extensive studies on elastic and inelastic light scattering. Modern India owes him much for her entry into the world of science, and for the strength of her scientific tradition.
Kramers's Contributions to Statistical Mechanics
Authors: Dresden Max
Published: January 2008

Hendrik A. Kramers was a major figure in the long and painful struggle that propelled quantum physics from the inspired but artful guessing game of the Bohr rules to a well-defined, coherent and systematic quantum mechanics. Kramers's basic and deep contributions in this struggle are barely known nowadays, and he actually suffers in comparison with Niels Bohr and Louis de Broglie, let alone Paul Dirac, Werner Heisenberg and Wolfgang Pauli. Kramers is still known for a number of isolated and disconnected results, such as the WKB method, the Kramers degeneracy in magnetism and the Kramers-Kronig relations. Although these are unquestionably significant and first-rate contributions, they do not demonstrate Kramers's deep physical insight and his profound concern for fundamental questions. They show Kramers as an extraordinarily skillful craftsman rather than as a scientific innovator. This may be an important reason why Kramers's reputation has faded so markedly in comparison with those of, say, Heisenberg or Pauli, whose contemporary he was and who, as his fellow architects of quantum mechanics, recognized him as a talented physicist and deep thinker. For example, when Bartel L. van der Waerden started to collect what he believed were the seminal papers in quantum mechanics, Pauli, hardly a person known for his generosity in giving undeserved credit, alerted him to the importance of Kramers's investigations.
Addressing Public Concerns in Science
Authors: Ahearne John F.
Published: January 2008

Mistrust of technical experts by the general public is a growing problem in science policy. The National Science Board reports that whereas 80 percent of the public believes that scientists work for the good of humanity, 55 percent believes that their knowledge gives scientists a power that makes them dangerous. The image of the crazed scientist plotting to master and destroy remains a staple of both children's and adult fiction, as Spencer Weart explained in a recent article in this magazine (June, page 28).
Physics and Soviet-Western Relations in the 1920s and 1930s
Authors: Josephson Paul R.
Published: January 2008

The recent intensification of Soviet interest in participating in international scientific activities is not merely a result of new policies introduced under Mikhail Gorbachev. Soviet scholars have sought out contacts with Western scholars since the first years of the Russian Revolution, although under Joseph Stalin and during times of heightened political tensions with the West these contacts have been reduced. On the eve of the revolution, the Russian empire had no more than a hundred physicists—including professors, docents and laboratory assistants with the equivalent of graduate degrees, but not including primary- or secondary-school teachers—and very few well-equipped laboratories. While creating conditions propitious to the long-term growth of physics as a dispcipline, the revolution led to short-term disruptions of research. Making matters worse, World War I cut physicists off from their customary contacts with Western scholars and laboratories, and the 1918–20 civil war between the Reds (the Bolsheviks and their allies) and the Whites (the monarchists and their sympathizers) atomized the domestic physics community.
Special Issue: Disordered Solids
Authors: Lee Patrick
Published: January 2008

Millions of years separated the formation of the first sedimentary rocks on our Earth from the emergence of the central nervous system. Some aspects of these very disparate systems have recently yielded to the language and methods of physics: The porous structure of sedimentary rocks can be modeled as a fractal, and neural networks, which provide models for understanding some simple aspects of the nervous system, may be regarded as dynamical systems. By collecting in a special issue of PHYSICS TODAY articles on sedimentary rocks and neural systems, which traditionally have been regarded as too complex for physicists, with ones on topics such as random magnets and disordered electronic systems, we hope to show that a common thread runs through these diverse subjects. That thread is the physics of disorder.
Disordered Electronic Systems
Authors: Al'tshuler Boris L. , Lee Patrick A.
Published: January 2008

The electrical conductivity of an ordinary metal such as gold is usually thought to be well understood. The electrons form a Fermi sea made up of plane waves modulated by the periodic crystal lattice. Because electrons obey Fermi statistics, only a narrow band of them, with an energy within kBT of the Fermi energy, contributes to the conductivity. At room temperature these electrons are scattered by lattice vibrations, resulting in a loss of momentum and a nonzero resistivity ρ(T). At low temperatures electron-electron scattering is the dominant scattering mechanism. In the limiting case of zero temperature there is a residual resistivity ρ0 caused by the scattering of the electrons at the Fermi energy by lattice imperfections such as impurities and vacancies. The static defects that disrupt the translational symmetry of the crystalline lattice are the source of the disorder considered in this article.
Quantum Interference Fluctuations in Disordered Metals
Authors: Webb Richard A. , Washburn Sean
Published: January 2008

In statistical physics one is trained to think about the properties of large ensembles of particles, and to calculate bulk properties by averaging over many microscopic configurations. Although the quantum mechanical properties of the individual constituents of a macroscopic object are important over some length scale (typically a few lattice spacings), they are usually not correlated across the whole object. We are, however, becoming acquainted with more and more disordered systems for which this effective length scale, at low temperatures, can be 100–10 000 times the characteristic microscopic scale; the correlation can involve more than 1011 particles. Such phenomena occur in an intermediate “mesoscopic” regime that lies between the microscopic world of atomic and molecular orbitals and the thoroughly macroscopic world where averages tell all. The wealth of novel quantum coherence phenomena recently observed in this intermediate size regime is the subject of this article.
Statistical Mechanics of Neural Networks
Authors: Sompolinsky Haim
Published: January 2008

A neural network is a large, highly interconnected assembly of simple elements. The elements, called neurons, are usually two-state devices that switch from one state to the other when their input exceeds a specific threshold value. In this respect the elements resemble biological neurons, which fire—that is, send a voltage pulse down their axons—when the sum of the inputs from their synapses exceeds a “firing” threshold. Neural networks therefore serve as models for studies of cooperative behavior and computational properties of the sort exhibited by the nervous system.
Getting out the Word: An Insider's View of Physical Review Letters
Authors: Passell Laurence
Published: January 2008

Those of you who are in the habit of reading the mastheads of journals may have noticed that Gene Wells—after a well-earned sabbatical at Los Alamos National Laboratory—has returned to his accustomed post as editor of the condensed matter physics section of Physical Review Letters. I was one of the “gang of four” who filled in for him while he was away (the others were Per Bak, Kelvin Lynn and Myron Strongin), and now that the dust has settled a bit and the ringing in my ears has died down, I'd like to share the experience with you.
Making Weapons, Talking Peace
Authors: York Herbert F.
Published: January 2008

My earliest memories of public affairs include the election of Herbert Hoover, the Great Depression, the election of Franklin Roosevelt, the rise of Adolf Hitler, the Japanese invasion of China, and the Italian invasion of Ethiopia—all of which took place while I was still in grade school. They continue with the Spanish civil war, which occurred when I was in high school. The European branch of World War II started in the same month that I entered college at the University of Rochester.
New Particle Accleration Techniques
Authors: Sessler Andrew M.
Published: January 2008

In 1932 John Cockcroft and Ernest Walton developed an electrostatic accelerator at the Cavendish Laboratory, thus starting the modern age of particle accelerators. Since then, our capabilities have increased tremendously, as may be seen in figure 1, which shows the energy of acceleratorsthrough the years. There has been an exponential increase in energy (the “Livingston curve”)—but it is the envelope that displays this exponential behavior, not any particular technique. One can conclude that if we are to stay anywhere near the Livingston curve, new techniques need to be developed.
The Biophysics of Visual Photoreception
Authors: Lewis Aaron , Del Priore Lucian V.
Published: January 2008

Vision is awe inspiring. The wondrous nature of this sensory process becomes clear when we consider just a few of its features. In the terminology of today's technology, the human visual system has a set of stereoscopic foreoptics that are instantly and automatically focusable to a few centimeters and are fully corrected for geometric aberrations, a servo-controlled two-axis scanning mechanism, a millisecond framing rate, sensitivity to brightnesses varying by a factor of 100 billion, the ability to detect a single photon, nearly 100% quantum efficiency and a spatial as well as temporal image processor that could not be matched by the fastest supercomputer.
How the Military Responded to the Laser
Authors: Seidel Robert W.
Published: January 2008

“I feel as do others here that the LASER may be the biggest breakthrough in the weapons area since the atomic bomb.” This statement, made in 1962 in a letter by Major General August Schomburg, head of the Army Ordnance Missile Command, reflected an attitude that was pervasive in the military in the first years after the birth of the laser. According to one contemporary assessment, there was “scarcely an Air Force, Army [or] Navy agency that does not now support, or talk of sponsoring in the near future, some type of basic or applied research or experimental development with optical masers.”
Photorefractive Nonlinear Optics
Authors: Feinberg Jack
Published: January 2008

Shine a helium-neon laser at a crystal of barium titanate, and at first the beam merely passes through the crystal. After a few seconds, however, the incident beam begins to scatter into a broad fan of light. After a few more seconds, a weak beam of light emerges from the crystal, traveling back exactly along the direction of the incident beam. As the laser continues to illuminate the crystal, the fan of scattered light disappears and the backscattered beam grows in strength, until it has stolen over half the power of the incident beam.
Western European Space Science
Authors: Axford Ion
Published: January 2008

In Europe space research began in the early 1960s, not long after the Soviet Union and the United States launched their first satellites. In the 1970s, after proceeding for many years at a rather leisurely pace, European nations stepped up their activity in space. Today the European Space Agency—a 13-nation intergovernmental organization that is Europe's counterpart to NASA—is well known for its successes with geophysical, interplanetary, astrophysical and other scientific spacecraft, as well as for technological and commercial projects such as communications satellites and the Ariane launcher (and its launch site in Kourou, French Guiana). ESA and individual European nations have planned many scientific space projects for the next decade and have even laid out an ambitious, but reasonable and well-grounded, plan for scientific projects beyond the year 2000. This article traces European space efforts from their beginnings a quarter of a century ago to their future in the next century, discussing not only the projects but also some of the intergovernmental politics that affect them. The discussion includes national programs (see figure 1) as well as those of ESA.
Mr. Eliot's Guide to Quantum Theory
Authors: Lowell John
Published: January 2008

Last year was the centenary of T. S. Eliot, perhaps the most influential of 20th-century poets writing in English. That Eliot pursued careers in publishing and banking in addition to his literary work is widely known, but many of his readers will be astonished to learn of the discovery last year of manuscripts that suggest he might at one time have been a student of physics. Published here for the first time, the poems are strongly influenced by the quantum theory that was growing vigorously when Eliot was a young man. They exhibit unmistakable echoes of “The Waste Land,” “Four Quartets” and Old Possum's Book of Practical Cats. (They also show remarkable physical prescience: Several of the ideas hinted at postdate Eliot's death in 1965.)
Liquids, Crystals and Liquid Crystals
Authors: Brock Joel D. , Birgeneau Robert J. , Litster J. David , Aharony Amnon
Published: January 2008

In thinking about the states of condensed matter, we usually consider two extremes. At one extreme are crystalline solids, in which atoms form a perfectly periodic array that extends to infinity in three directions. At the other extreme are fluids or glasses, in which the atoms or molecules are completely disordered and the system is both orientationally and positionally isotropic—that is, the materials look the same when viewed from any direction.
Reaching the Critical Mass in High School Physics
Authors: Neuschatz Michael
Published: January 2008

In the past decade a new wave of apprehension about public education—especially science education—has come to the fore. A spate of recent studies has heightened the sense of unease by suggesting a lack of improvement in science proficiency among succeeding cohorts of US students and a slippage in international standings in comparative tests of science knowledge. Such widespread alarm over the academic health of our nation is a relatively new development. Until two generations ago the United States was widely regarded as a pioneer in instituting and extending free and universal public education. Education was extolled as a national resource, and a literate populace was regarded by many as critical to the maintenance of political democracy, to the attainment of a society committed to equal opportunity and the reward of merit, to the pursuit of a robust and internationally competitive economy and to the preservation of a strong national defense.
Special Issue: The Physics of Imaging
Authors: Snavely Benjamin B.
Published: January 2008

The science of imaging and its applications touch all aspects of physics. The response of materials to light and other forms of radiation yields insights into some of the most fundamental properties of matter. Imaging technology also provides a means for viewing and understanding physical processes, as well as for recording and sharing the results.
Physics of the Photographic Latent Image
Authors: Tani Tadaaki
Published: January 2008

How does photographic film give such good images with so little exposure to light? The answer, in a word, is amplification. Light causes clusters of silver atoms to form on silver halide microcrystals in a photographic emulsion. These clusters, which may contain as few as three or four silver atoms, catalyze the reduction of all the silver ions in the microcrystals to which they are attached, giving a “gain” of over a billion. This is the basis for the high sensitivity and image quality of silver halide photographic film. As I will explain in this article, much is known about the physical mechanisms involved, and by using this knowledge one can improve the sensitivity and efficiency of film.
Confocal Scanning Optical Microscopy
Authors: Kino Gordon S. , Corle Timothy R.
Published: January 2008

Virtually everyone has used an optical microscope, if only to dissect a frog in school or to observe the life forms in a drop of pond water. The optical microscope is a powerful research tool in many areas of science, such as biology, geology, medicine and, more recently, semiconductor metrology. As the need to visualize submicron structures has become more pressing, several new types of microscopes have been developed—for example, the confocal scanning optical microscope, the scanning acoustic, the scanning electron and the scanning tunneling microscopes.
The Unification of Electromagnetism with the Weak Force
Authors: Langacker Paul , Mann Alfred K.
Published: January 2008

The year 1983 marked the end of a particularly noteworthy decade in the development of elementaryparticle physics. Between 1973 and 1983 there were three accomplishments of special, perhaps historic, importance:

▹ The theoretical and experimental unification of the forces that govern all of the phenomena of both electromagnetism and the weak interactions.

▹ The recognition that the strongly interacting particles (nucleons, mesons and other hadrons) are in fact made of still smaller entities, now known as quarks, and the development of a tentative theory of the force between the quarks.

▹ The identification of three almost identical (except for mass) families of elementary “particles,” each family consisting of two quarks, one charged lepton (the electron, the muon or the tau) and a neutrino.
Special Issue: Richard Feynman
Authors: Lubkin Gloria B.
Published: January 2008

The diagram you see scattered throughout this issue is a reminder of the legacy Richard Feynman left us. Feynman was a hero to me, as he was to many of us. When he died on 15 February 1988, the world lost one of the finest theoretical physicists of the 20th century.
Feynman at Cornell
Authors: Dyson Freeman J.
Published: January 2008

Just a brief letter before we go off to Rochester. We have every Wednesday a seminar at which somebody talks about some item of research, and from time to time this is made a joint seminar with Rochester University. Today is the first time this term that we are going over there for it. It is a magnificent day, and it should be a lovely trip; Rochester is due north of here, and we go through some wild country. I am being taken in Feynman's car, which will be great fun if we survive. Feynman is a man for whom I am developing a considerable admiration; he is the brightest of the young theoreticians here, and is the first example I have met of that rare species, the native American scientist. He has developed a private version of the quantum theory, which is generally agreed to be a good piece of work and may be more helpful than the orthodox version for some problems; in general he is always sizzling with new ideas, most of which are more spectacular than helpful, and hardly any of which get very far before some newer inspiration eclipses them. His most valuable contribution to physics is as a sustainer of morale; when he bursts into the room with his latest brain-wave and proceeds to expound it with the most lavish sound effects and waving about of the arms, life at least is not dull. [Victor] Weisskopf, the chief theoretician at Rochester, is also an interesting and able man, but of the normal European type; he comes from Munich, where he was a friend of Bethe from student days.
Dick Feynman—The Guy in the Office Down the Hall
Authors: Gell-Mann Murray
Published: January 2008

When I think of Richard, I often recall a chilly afternoon in Altadena shortly after his marriage to the charming Gweneth. My late wife, Margaret, and I had returned in September 1960 from a year in Paris, London and East Africa; Richard had greeted me with the news that he was “catching up with me”—he too was to have an English wife and a small brown dog. The wedding soon took place, and it was a delightful occasion. We also met the dog (called Venus, I believe) and found that Richard was going overboard teaching her tricks (leading his mother, Lucille, with her dry wit, to wonder aloud what would become of a child if one came along). The Feynmans and we both bought houses in Altadena, and on the afternoon in question Margaret and I were visiting their place.
Using Computers in Teaching Physics
Authors: Wilson Jack M. , Redish Edward F.
Published: January 2008

The computer has revolutionized the way we do physics, but surprisingly, it has not significantly altered the way we teach physics. Talks and papers on teaching with computers fill the meetings and journals of the American Association of Physics Teachers, and workshops on the topic abound, yet the real impact of computers in the classroom is slight. In physics research, change comes quickly, disseminates rapidly and is widely appreciated. In physics teaching, change evolves gradually, spreads slowly and frequently meets with resistance. On 6 June 1988 The Wall Street Journal published a story with the headline “Computers Failing as Teaching Aids.” The reasons the Journal cited for this failure at the general pre-college education level apply equally well to physics teaching at the introductory college level: lack of access to computers, poor software and faculty members who are inadequately prepared to use computers effectively.
The Site Contest for Fermilab
Authors: Westfall Catherine L.
Published: January 2008

On 10 November the Department of Energy announced that the Superconducting Super Collider will be located on the Blackland Prairie corn and cotton fields around Waxahachie, Texas. The decision ended a competition entered by 25 states more than a year earlier. The contest for the SSC was reminiscent of way the site for Fermilab was chosen in 1966. Indeed, the procedure invented for selecting Fermilab was copied for the SSC, right down to the preliminary run-off refereed by a panel appointed by the National Academy of Sciences and the visits by a government team to the final few sites in the competition. Even the complaints from local citizens and the rumors of political influence that were rife during the Fermilab competition had their counterparts in the SSC contest.
Nuclear Magnetic Ordering at Nanokelvin Temperatures
Authors: Lounasmaa Olli V.
Published: January 2008

Just as electrons engage in spontaneous magnetic ordering, accounting for such phenomena as ferromagnetic domains, so too can nuclei order spontaneously. However, because nuclear magnetic moments are very much smaller than electron magnetic moments, spontaneous nuclear ordering occurs only at extremely low temperatures. As we will see, experiments conducted in the course of research on nuclear ordering have produced spin temperatures as low as 25 nanokelvins in copper and 2 nanokelvins in silver.
Science and Scientists for a Nuclear-Weapon-Free World
Authors: Velikhov Evgeny P.
Published: January 2008

The scientific communities of the USSR and the US have been active both in developing new weapons and in attempting to curb the arms race, or at least in trying to prevent it from leading to the ultimate catastrophe. Scientists on the two sides have worked sometimes independently and sometimes with a degree of interaction, direct or indirect.
Laser Optics of Neutral Atomic Beams
Authors: Balykin Victor I. , Letokhov Vladilen S.
Published: January 2008

In ordinary optics one exploits the interaction of radiation with matter to manipulate beams of light. One can also turn the tables and control beams of charged or neutral material particles through their interaction with light. There are deep analogies and similarities between these two sorts of optics, even though they involve very different kinds of interactions between matter and radiation. Perhaps one can exploit every such interaction for some kind of “optics”—controlling beams of photons or massive particles. In this article we will describe recent developments in the laser optics of atomic beams—how experimenters are using the radiation pressure of laser light to manipulate neutral atoms.
Where on Earth is the Crust?
Authors: Anderson Don L.
Published: January 2008

Astronomers confidently speak of the chemistry of stars, galaxies and even interstellar space, but curiously, we are grossly ignorant of the composition of our own planet. “Whole Earth” scientists work under an extreme handicap compared with investigators in most other disciplines. Physicists, astronomers and biologists can formulate general theories and design experiments on the basis of many examples. By contrast, there is a single Earth, the result of a unique experiment, and we have direct access only to its outer portions. (Another obvious “singular” object of scientific study is the universe itself.)
Ebert Spectrometer Reflections
Authors: Fastie William G.
Published: January 2008

The Ebert spectrometer, named for its inventor, the 19th-century German spectroscopist Hermann Ebert, emerged from obscurity after the Second World War to play a significant role in the exploration of the solar system. I had a part in its resurrection, and the Ebert spectrometer has played a dominant role in my scientific career. Therefore I've taken the trouble to look into its history. The evolution of this instrument, now a century old, was curiously haphazard and fraught with mistakes. I have attempted here to put these events into chronological, and somewhat autobiographical, perspective.