Bruce Schechter

Reports on Subfields of Physics: Gravitation, Cosmology and Cosmic‐Ray Physics

In 1982 the Astronomy Survey Committee, under the direction of George Field, published Astronomy and Astrophysics in the 1980s (see PHYSICS TODAY, April 1982, page 96, and November 1982, page 25), a report similar in purpose to the current Brinkman report. Gravitation, cosmology and cosmic‐ray physics were then, properly, considered as subfields of astrophysics. But these three fields, because they are concerned with the nature of the fundamental forces and constituents of matter, are also of direct interest to physicists. For this reason one volume of the Brinkman report is devoted to recounting the achievements in and identifying goals for the related fields of gravitation, cosmology and cosmic‐ray physics.

Reports on Subfields of Physics: Plasmas and Fluids

Plasma physics and fluid physics are large fields that are themselves divided into subdisciplines: Plasma physics is practiced by fusion and space researchers and applied to the development of novel particle accelerators and coherent‐light sources, to isotope separation and to astrophysics; fluid physics is important to geophysics, biology, medicine, meteorology, combustion research and pollution control—as well as to plasma physics. The panel devotes one chapter each to fluid physics; general plasma physics, fusion plasmas, confinement and heating; and space and astrophysical plasmas. The highlights and recommendations of the panel report are numerous; space limitations permit only a relatively small number of these to be described below.

Reports on Subfields of Physics: Condensed‐Matter Physics

Such extraordinary technological innovations as the transistor, superconducting magnets, solid‐state lasers, liquidcrystal displays and highly sensitive detectors of radiant energy come under the umbrella of condensed‐matter physics. The basic contributions of condensed‐matter physics to the study of critical phenomena, broken symmetry and defects have had a major impact on nuclear physics, elementaryparticle physics, astrophysics, molecular physics and chemistry. The panel report on condensed‐matter physics is a fascinating tour of this diverse yet unified field. Some of the stops include:

Searching for Gravity Waves with Interferometers

A collaboration of physicists from Caltech and MIT has recently produced detailed plans for a pair of large detectors, based on laser interferometry, that they believe should be sensitive enough to detect gravity waves from several types of astrophysical sources. The detectors, which will each consist of an L‐shaped vacuum chamber 4 kilometers long through which laser‐interferometer beams will travel, are tentatively to be located in Columbia, Maine, and at Edwards Air Force Base, California. The projected cost is between

Voyager Visits Uranus and Observes Rings and Moons

50 and

Reports on Subfields of Physics: Elementary‐Particle Physics

60 million. If this sum is forthcoming from NSF the detectors could be on the air as early as 1991. According to Ronald Drever (Caltech), who, along with Rainer Weiss (MIT), heads the collaboration, the leap in sensitivity from existing detectors to their planned interferometer is like “going from the human eye to the Mount Palomar telescope.” Successful detection would not only help sort out competing theories of gravity, but open up a new window on violent processes throughout...

Reports on Subfields of Physics: Nuclear Physics

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 worlds scientific community will be granted full access to the Voyager 2 Uranus data. Until then they will have to be satisfied with the Voyager teams preliminary conclusions, which were published last month.

Measuring the Hubble Constant

In the past 20 years the subnuclear world—which, due to a seemingly endless supply of “elementary” particles, was once likened to a zoo—has become a gratifyingly orderly place. The Elementary‐Particle Physics Panel of the physics survey committee begins its report with a summary of the astounding progress of the last two decades: the emergence of a standard model of the universe as being made of quarks and leptons bound together by photons, gluons and W and Z particles; the unification of the weak and electromagnetic forces in a single gauge‐field theory; the understanding of baryon and meson structure in terms of quantum chromodynamics; the theory of interacting quarks and gluons; the possibility of a grand unification of all of the forces of nature; and the convergence of elementary‐particle physics and cosmology, each helping to elucidate the other. So much, the panel report explains, has been achieved. But many questions remain:▸ What is the origin of mass, and what sets the masses of the different el...

Reports on Subfields of Physics: Atomic, Molecular and Optical Physics

In the 50 or so years between the discovery of the neutron and the meeting of the Panel on Nuclear Physics of the physics survey committee our understanding of the physical universe has been immeasurably expanded. In its report the panel first reviews the impressive achievements in nuclear physics of the decade passed, then goes on to make recommendations designed to insure continued achievement in the future.

Magnetic Fields Induce Superconductivity

Hubbles celebrated constant, which relates the recessional velocities of galaxies to their distances, is perhaps the most important number in extragalactic astronomy. Using it, along with their favorite models, astronomers and cosmologists derive the age of the universe, estimate its size, calculate the luminosity of quasars and much more. Unfortunately, astronomers are far from agreeing on a value for Hubbles constant. Some believe that H0 is about 50 km/sec Mpc; others think it is closer to 100 km/sec Mpc. Depending on the details of the cosmological model chosen, this can lead to a discrepancy of a factor of 2—ten billion years or so—in the age of the universe.