Joseph Weber, professor emeritus of physics at the University of Maryland, College Park, died on 30 September 2000 in Pittsburgh, Pennsylvania, while undergoing treatment for non-Hodgkins lymphoma.
Born on 17 May 1919 in Paterson, New Jersey, Weber was awarded an appointment to the US Naval Academy as a result of a competitive examination. He received a BS degree in 1940 from the academy. That same year, he was commissioned as an ensign and was posted to the aircraft carrier Lexington, which narrowly escaped disaster by steaming out of Pearl Harbor on 5 December 1941. Weber survived the sinking of the ship during the Battle of the Coral Sea on 8 May 1942. He then commanded the submarine chaser SC 690, which helped protect convoys crossing the Atlantic Ocean, and participated in the landings on Sicily in July 1943.
After World War II ended, Weber became head of the electronic design section of the Navy’s Bureau of Ships. Because of his experience as a radio amateur and his involvement with radar, Weber was assigned responsibility for electronic countermeasures. In 1948, he resigned his commission as a lieutenant commander and joined the University of Maryland as a full professor of electrical engineering. That year, he also entered graduate school at the Catholic University of America. He received his PhD in physics in 1951 for research carried out with Keith J. Laidler on the microwave inversion spectrum of ammonia.
At about the same time, Weber realized that the Einstein A and B coefficients can be exploited to produce amplifiers of electromagnetic radiation of the sort that are now called masers and lasers. He presented his ideas in a talk at the June 1952 conference of the Institute of Radio Engineers in Ottawa, Canada, and published the first open-literature paper on what is now called quantum electronics. His efforts were acknowledged by the IRE when they awarded him a fellowship (in 1958) “for his early recognition of concepts leading to the maser.” The development of operating maser and laser devices was achieved by Charles Townes, Nikolai Basov, Aleksandre Prokhorov, Theodore Maiman, and Arthur Schawlow.
Weber spent the 1955–56 academic year as a fellow of the Institute for Advanced Study in Princeton, New Jersey, where he immersed himself in general relativity. In 1961, he joined the physics department at the University of Maryland as a full professor.
During the early 1960s, Weber turned his attention to testing the general relativistic prediction of gravitational waves from collisions or collapses involving strong gravity. In typical fashion, he first studied the field, published a beautiful and concise monograph on gravitational waves in 1961 (Interscience Publishers), and then set about developing a detector that might be able to measure displacements smaller than the size of the nucleus in a macroscopic-sized object. He was alone in charting these unknown waters: His first paper on how to build a gravity wave detector was published in 1959 and the second, in 1960. Weber developed an experiment using a large suspended bar of aluminum, with a high resonant Q at a frequency of about 1 kH; the oscillation of the bar after it had been excited could be measured by a series of piezoelectric crystals mounted on it. The output of the system was put on a chart recorder like those used to record earthquakes. Weber studied the excursions of the pen to look for the occasional tone of a gravitational wave passing through the bar. The signals seemed to show the presence of gravitational waves. He published his results in Physical Review Letters (1969), claiming evidence for observation of gravitational waves in 1969 based on coincident signals from two bars separated by 1000 km. These and subsequent observations by Weber were greeted with great excitement in the early 1970s; however, the strength implied by his signals was very much in excess of what was expected. In the following years, various experimenters built more sensitive bars, including low-temperature bars, and looked for signals, but it was difficult to see gravitational signals without ambiguity. Even so, the Weber gravitational detector stands as an important milestone in the development of gravitational wave astronomy.
When Weber first reported the possible observation of gravitational signals by his bar detectors, Sandy Wall and one of us (Yodh) immediately suggested to him that we should determine whether energetic cosmic-ray showers could produce observable pulses in his bars. We carried out (in 1970) a coincidence experiment with a cosmic-ray telescope consisting of scintillation counters above and below Weber’s room-temperature detector. We showed that the observed coincidences with cosmic-ray events were consistent with being accidentals, thus eliminating cosmic-ray showers as being necessarily a source of the signals. Nearly three decades later, the Rome (Italy) group again studied the problem using the sensitive NAUTILUS detector, a 2300-kg bar at 100 mK. The group reported observing events that may be attributed to cosmic-ray showers in the bar. Weber continued doing coincidence experiments with several bar detectors, some at the University of Maryland and another at Argonne National Laboratory in the 1970s, and later with bar detectors built by the Rome group. Experiments to observe coincident events are currently being carried out by the International Gravitational Event Collaboration, which consists of low-temperature bars in Australia, the US, and Europe. None have yet been observed, and new upper limits for amplitude and rate of gravitational wave bursts have been set.
Weber also proposed the idea of doing an experiment to detect gravitational waves using laser interferometric techniques. Robert Forward, Weber’s student and postdoctoral associate, did the first laser interferometric gravitational wave experiments while at Hughes Research Laboratories in Malibu, California.
The pioneering work of Weber spawned a new and vibrant field: the search for gravitational waves. The international physics community is now constructing more sensitive detectors for gravitational wave signals using interferometric techniques, such as the US project for the Laser Interferometer Gravitational Wave Observatory (LIGO); the French–Italian VIRGO experiment; the Japanese 300-m TAMA interferometer; and GEO-600, the 600-m German–British interferometer. Planning is under way for future space-based interferometers, such as the Laser Interferometer Space Antenna (LISA), a NASA–European Space Agency collaboration, to explore the low-frequency window.
Weber loved the outdoors and was an exercise enthusiast. He was an ardent and able rock climber. One of us (Yodh) remembers climbing with him on the rocks flanking the Potomac River in Carderock, Maryland. He also jogged and swam regularly and was in fit condition until his last few years. He would say that “health is the most important thing for a physicist to have, for you cannot do physics once you are dead.” He set a great example to students and colleagues in colloquia and seminars by keeping a good, written record in a hardbound logbook. His workbooks were very carefully kept and cross referenced. He was married to astronomer Virginia Trimble, who is a professor at the University of California, Irvine, and at the University of Maryland. After 1973 until before his death, he split his research time between the University of Maryland and UC Irvine. Weber was a dedicated scientist and an inspiration to many who interacted with him.
