autobiography and work

਀㰀戀爀㸀䐀椀猀挀漀瘀攀爀礀 漀昀 琀栀攀 昀椀爀猀琀 戀椀渀愀爀礀 瀀甀氀猀愀爀  愀渀搀 猀甀戀猀攀焀甀攀渀琀 琀攀猀琀猀 漀昀 䜀刀

਀ Pulsars were discovered, albeit accidentally, by Jocelyn Bell at Cambridge in 1967. The apparently sporadic bursts of radio emission appeared during the course of a survey to investigate the effects of interplanetary scintillation of radio sources. Working as a graduate student in a team lead by Anthony Hewish, Bell soon realized that the emission always occurred at the same position in the celestial sphere indicating that the source was not of terrestrial origin. Subsequent observations with greater time resolution showed the emission to be a train of pulses with a precise repetition period of 1337 ms. The Cambridge team published their discovery the following and, soon afterwards, announced the discovery of 3 more pulsars found from subsequent inspection of the remaining survey data. ਀㰀⼀瀀㸀 ਀㰀戀爀㸀 Prior to the discovery, neutron stars were a purely theoretical concept - first proposed by Walter Baade and Fritz Zwicky to be the collapsed remains of a massive star after it has exploded as a supernova. The existence of neutron stars, and the prediction made by Baade-Zwicky that neutron stars would be associated with supernova remnants was dramatically confirmed with the measurement at the Arecibo Observatory of the short rotational period (33 ms) of the Crab pulsar in 1968. The pulsar lies at the center of the Crab nebula, shown on the right, this is the remains of a nearby supernova explosion witnessed by Chinese astronomers in 1054 AD. Using the rotating neutron star model, Thomas Gold of Cornell University, USA was able to show that the Crab pulsar is the dominant energy supply to its surrounding nebula. The connection between pulsars and rotating neutron stars is now universally accepted. ਀㰀⼀戀爀㸀㰀戀爀㸀 In over 30 years since the discovery, pulsars have proved to be exciting objects to study and, presently, over 1000 are known. Most of these are ``normal'' in the sense that their pulse periods are of order one second and, with few exceptions, are observed to increase secularly at the rate of about one complete period in 1,000,000,000,000,000! This is naturally explained as the gradual spin-down of the neutron star as it radiates energy at the expense of its rotational kinetic energy. A small fraction of the observed sample are the so-called ``millisecond pulsars'' which have much shorter periods (< 20 ms) and rates of slowdown of typically only one period in 10,000,000,000,000,000,000, proving to be extremely accurate clocks. In addition, some pulsars are known to be members of binary systems in which the companion is another neutron star, a white dwarf and even a main sequence star. ਀倀甀氀猀愀爀 刀攀猀攀愀爀挀栀 愀琀 䄀爀攀挀椀戀漀

਀䘀爀漀洀 琀栀攀 攀愀爀氀礀 搀愀礀猀 爀攀猀攀愀爀挀栀攀爀猀 愀琀 䄀爀攀挀椀戀漀 伀戀猀攀爀瘀愀琀漀爀礀 樀漀椀渀攀搀 琀栀攀 攀昀昀漀爀琀 琀漀 猀攀愀爀挀栀 昀漀爀 渀攀眀 瀀甀氀猀愀爀猀 愀渀搀 琀漀 甀渀搀攀爀猀琀愀渀搀 琀栀攀 瀀栀礀猀椀挀愀氀 瀀爀漀挀攀猀猀攀猀 爀攀猀瀀漀渀猀椀戀氀攀 昀漀爀 琀栀椀猀 爀攀洀愀爀欀愀戀氀攀 瀀栀攀渀漀洀攀渀漀渀⸀ 吀栀攀椀爀 洀攀愀猀甀爀攀洀攀渀琀 漀昀 琀栀攀 瀀攀爀椀漀搀椀挀椀琀礀 漀昀 琀栀攀 䌀爀愀戀 瀀甀氀猀愀爀 瀀爀漀瘀攀搀 琀栀愀琀 渀攀甀琀爀漀渀 猀琀愀爀猀 攀砀椀猀琀 椀渀 琀栀攀 唀渀椀瘀攀爀猀攀 愀渀搀 琀栀愀琀 琀栀攀礀 愀爀攀 琀栀攀 攀渀搀 瀀漀椀渀琀 漀昀 猀琀攀氀氀愀爀 攀瘀漀氀甀琀椀漀渀 昀漀爀 洀愀猀猀椀瘀攀 猀琀愀爀猀⸀ 䄀 昀攀眀 漀琀栀攀爀 氀愀渀搀洀愀爀欀 挀漀渀琀爀椀戀甀琀椀漀渀猀 戀礀 䄀爀攀挀椀戀漀 瀀甀氀猀愀爀 愀猀琀爀漀渀漀洀攀爀猀 愀爀攀 猀甀洀洀愀爀椀稀攀搀 栀攀爀攀⸀  PSR B1913+16: ਀㰀⼀戀爀㸀㰀戀爀㸀 During a systematic search of the galactic plane with the Arecibo telescope in July 1974, Russell A. Hulse and Joseph H. Taylor discovered an extraordinary of 59 ms pulsar PSR B1913+16. It soon became clear that the timing properties of this source could only be understood if the pulsar were in a highly eccentric 7.75 hour orbit around another neutron star. The intense gravitational field generated by the neutron stars results in several special and general relativistic effects unobtainable in a terrestrial physics laboratory, or even in Solar System experiments. Perhaps the most important effect is the emission of gravitational radiation from the system at the expense of its gravitational binding energy. According to Einstein's general theory of relativity, the separation of the stars should decrease by 3 mm each orbit due to this process. ਀㰀⼀戀爀㸀㰀戀爀㸀 From regular observations, the orbital decay was measured by Taylor and collaborators within 6 years of the discovery and is in agreement with general relativity to better than a percent after nearly 20 years of observations. The discovery of this fascinating binary system and the subsequent measurements provide the only experimental evidence to date for the existence of gravitational radiation. In recognition of this achievement, Hulse and Taylor were awarded the 1993 Nobel Prize in Physics. For more about the importance of this discovery, see the Press release from the Swedish Academy and Cornell's Astronomy Course web page. Click here for more information on PSR 1913+16. ਀倀匀刀 䈀㄀㤀㌀㜀⬀㈀㄀㨀 

਀吀栀攀 搀椀猀挀漀瘀攀爀礀 漀昀 琀栀攀 昀椀爀猀琀 怀洀椀氀氀椀猀攀挀漀渀搀 瀀甀氀猀愀爀✀ 倀匀刀 ㄀㤀㌀㜀⬀㈀㄀ 眀愀猀 洀愀搀攀 愀琀 䄀爀攀挀椀戀漀 戀礀 䐀漀渀 䈀愀挀欀攀爀Ⰰ 匀栀爀椀 䬀甀氀欀愀爀渀椀 挀漀氀氀愀戀漀爀愀琀漀爀猀 椀渀 ㄀㤀㠀㈀⸀ 吀栀椀猀 爀攀洀愀爀欀愀戀氀攀 渀攀甀琀爀漀渀 猀琀愀爀 眀椀琀栀 愀 猀瀀椀渀 瀀攀爀椀漀搀 漀昀 樀甀猀琀 ㄀⸀㔀㔀㜀㠀 洀猀 爀漀琀愀琀攀猀 愀戀漀甀琀 椀琀猀 愀砀椀猀 愀氀洀漀猀琀 㘀㐀㈀ 琀椀洀攀猀 瀀攀爀 猀攀挀漀渀搀⸀ 吀栀椀猀 瘀愀氀甀攀 椀渀琀爀漀搀甀挀攀搀 昀甀渀搀愀洀攀渀琀愀氀 挀漀渀猀琀爀愀椀渀琀猀 琀漀 攀焀甀愀琀椀漀渀猀 漀昀 猀琀愀琀攀 昀漀爀 挀漀氀搀 洀愀琀琀攀爀 愀琀 猀甀瀀爀愀ⴀ渀甀挀氀攀愀爀 搀攀渀猀椀琀椀攀猀⸀ 吀栀攀 搀椀猀挀漀瘀攀爀礀 爀攀瘀椀琀愀氀椀稀攀搀 瀀甀氀猀愀爀 愀猀琀爀漀渀漀洀礀 猀椀渀挀攀 椀琀 搀攀洀漀渀猀琀爀愀琀攀搀 琀栀愀琀 愀 瀀漀琀攀渀琀椀愀氀氀礀 氀愀爀最攀 瀀漀瀀甀氀愀琀椀漀渀 漀昀 猀椀洀椀氀愀爀 漀戀樀攀挀琀猀 攀砀椀猀琀猀 眀栀椀挀栀 栀愀搀 戀攀攀渀 洀椀猀猀攀搀 戀礀 瀀甀氀猀愀爀 猀攀愀爀挀栀攀猀 挀漀渀搀甀挀琀攀搀 搀甀爀椀渀最 琀栀攀 ㄀㤀㜀　猀 眀栀椀挀栀 栀愀搀 猀愀洀瀀氀椀渀最 爀愀琀攀猀 㸀 ㈀　 洀猀⸀ 吀栀攀猀攀 漀戀樀攀挀琀猀 栀愀瘀攀 攀砀琀爀愀漀爀搀椀渀愀爀礀 爀漀琀愀琀椀漀渀愀氀 猀琀愀戀椀氀椀琀礀Ⰰ 眀栀椀挀栀 漀瀀攀渀攀搀 甀瀀 渀攀眀 愀瘀攀渀甀攀猀 漀昀 爀攀猀攀愀爀挀栀㨀 栀椀最栀 瀀爀攀挀椀猀椀漀渀 琀椀洀椀渀最 愀渀搀 猀漀氀愀爀 猀礀猀琀攀洀 猀琀甀搀椀攀猀Ⰰ 栀椀最栀 瀀爀攀挀椀猀椀漀渀 琀攀猀琀猀 漀昀 䜀刀 愀渀搀 琀栀攀 渀愀琀甀爀攀 漀昀 猀瀀愀挀攀ⴀ琀椀洀攀 椀琀猀攀氀昀Ⰰ 猀琀攀氀氀愀爀 攀瘀漀氀甀琀椀漀渀Ⰰ 琀攀猀琀猀 漀昀 渀甀挀氀攀愀爀 瀀栀礀猀椀挀猀 愀渀搀 猀攀愀爀挀栀 昀漀爀 氀漀渀最ⴀ瀀攀爀椀漀搀 最爀愀瘀椀琀愀琀椀漀渀愀氀 眀愀瘀攀猀⸀  PSR B1957+20: ਀㰀⼀戀爀㸀㰀戀爀㸀 Although subsequent pulsar surveys with better sensitivity to short period objects have found a large number of similar objects, for 24 years PSR B1937+21 stayed as the most rapidly rotating neutron star known. The next shortest period object, PSR B1957+20 was discovered at Arecibo in 1988 by Andy Fruchter and collaborators. This 1.6074 ms pulsar turns out to be in a near circular 9 hr orbit around a low-mass companion star. The pulsar is eclipsed by its companion for about 50 minutes per orbit. For a few minutes before an eclipse becomes complete, and for more than 20 minutes after the signal reappears, the pulses are delayed by as much as several hundred microseconds- presumably as a result of propagation through plasma surrounding the companion. Detailed studies of this system suggest that the companion is being gradually ablated by the relativistic `wind' of the pulsar. This system may be a progenitor for single millisecond pulsar like PSR 1937+21. ਀倀匀刀 䈀㄀㈀㔀㜀⬀㄀㈀㨀 

਀吀栀攀 䄀爀攀挀椀戀漀 搀椀猀挀漀瘀攀爀椀攀猀 挀漀渀琀椀渀甀攀搀 椀渀 ㄀㤀㤀㈀ 眀椀琀栀 琀栀攀 愀渀渀漀甀渀挀攀洀攀渀琀 漀昀 琀栀攀 昀椀爀猀琀 攀砀琀爀愀ⴀ猀漀氀愀爀 瀀氀愀渀攀琀愀爀礀 猀礀猀琀攀洀 欀渀漀眀渀⸀ 吀栀椀猀 漀爀戀椀琀猀 愀爀漀甀渀搀 琀栀攀 洀椀氀氀椀猀攀挀漀渀搀 瀀甀氀猀愀爀 倀匀刀 䈀㄀㈀㔀㜀⬀㄀㈀Ⰰ 愀渀搀 眀愀猀 搀椀猀挀漀瘀攀爀攀搀 戀礀 䄀氀攀砀 圀漀氀猀稀挀稀愀渀 愀渀搀 䐀愀氀攀 䘀爀愀椀氀⸀ 吀椀洀椀渀最 漀戀猀攀爀瘀愀琀椀漀渀猀 漀昀 琀栀椀猀 猀礀猀琀攀洀 栀愀瘀攀 猀漀 昀愀爀 爀攀瘀攀愀氀攀搀 琀栀攀 瀀爀攀猀攀渀挀攀 漀昀 愀琀 氀攀愀猀琀 琀栀爀攀攀 䔀愀爀琀栀ⴀ洀愀猀猀 戀漀搀椀攀猀 椀渀 漀爀戀椀琀 愀爀漀甀渀搀 琀栀攀 渀攀甀琀爀漀渀 猀琀愀爀⸀ ਀㰀⼀戀爀㸀㰀戀爀㸀 ਀ ਀ ਀ Medicine Hat is a small town in Southwestern Alberta founded just over 100 years ago in a valley where the Canadian Pacific Railway crossed the South Saskatchewan River. I was born there on November 2, 1929 and raised in comfortable if somewhat Spartan circumstances. My father was the son of a Northern Irish carpenter and his Scottish wife who homesteaded on the Canadian prairies; my mother was an American, the daughter of Norwegian immigrants to the northern United States who moved to a farm in Alberta shortly after the first World War. During my early years our family of three was part of a large family clan headed by my Scottish grandmother. I attended schools named after English Generals and Royalty - Kitchener, Connaught, Alexandra.਀ Although I read quite a bit and found mathematics easy, I was not an outstanding student. In high school I did reasonably well in mathematics and science thanks to some talented and dedicated teachers.਀

I was nearly ten years old when World War II began. That conflict had a great effect on our town, and on me. In rapid succession the town found itself host to an R.A.F. flight training school, a prisoner of war camp and a military research establishment. The wartime glamor of the military, the sudden infusion of groups of sophisticated and highly-educated people, and new cultural opportunities (the first live symphonic music I ever heard was played by German prisoners of war) all transformed our town and widened the horizons of the young people there. I developed an interest in explosives and blew three fingers off my left hand just before hostilities ended in Europe. The atomic bomb that ended the war later that summer made me intensely aware of physicists and physics.਀ Higher education was highly prized in the society of a small prairie town and I was expected to continue on to university. After some difficulties over low grades in some high school subjects, I was admitted to the University of Alberta in Edmonton. I registered in a special program emphasizing mathematics and physics and gradually became interested in experimental physics, continuing my studies towards a Masters degree at the same institution. My thesis research was a rather primitive effort to measure double b-decay in an aging Wilson cloud chamber. Between sessions at the University, I spent two summers as a research assistant at the Defense Research Board installation near Medicine Hat working with Dr. E.J. Wiggins, who encouraged me to continue my studies either in eastern Canada or in the United States.਀

Those were interesting years, and during this time I met, courted and married Rita Bonneau - a partnership which has enriched my life in every way. Together we decided to try California, and I was accepted into the graduate program at Stanford, while she found work teaching in a military school in order to support us both. The first two years at Stanford were exciting beyond description - the Physics Department at Stanford included Felix Bloch, Leonard Schiff, Willis Lamb, Robert Hofstadter, and W.K.H. (Pief) Panofsky who had just arrived from Berkeley. I found that I had to work hard to keep up with my fellow students, but learning physics was great fun in those surroundings. At the end of the second year I joined the High Energy Physics Laboratory where the new linear accelerator was just beginning to do experiments. My thesis work was accomplished there under Prof. Robert F. Mozley, on a rather diffcult experiment producing polarized g-rays from the accelerator beam and then using those g-rays to study p-meson production.਀

In 1958 I was invited to join a group of physicists at the École Normale Supérieure in Paris who were planning experiments at an accelerator (similar to the linac at Stanford) which was under construction in Orsay. I stayed in France for about three years working on the experimental facilities for the accelerator, and then participated in some electron scattering experiments. My wife began a new career there as a librarian at the Orsay laboratory, a career which was interrupted for a while when our son, Ted, was born in 1960. We returned to the United States in 1961 but a continuing connection to French physics and physicists has been a significant element in my life since that time - including a Doctorate (Honoris Causa) very kindly conferred upon me in 1980 by the Université de Paris-Sud.਀ Upon our return to the United States, I joined the staff of the Lawrence Berkeley Laboratory at the University of California. After less than a year in Berkeley, I moved back to Stanford where work on the construction of Stanford Linear Accelerator Center (SLAC) was just beginning. At SLAC, I started working on the design of the experimental areas for the new accelerator. By 1963 I had joined the group considering the requirements for electron scattering apparatus in the larger of two experimental areas. I worked closely with Pief Panofsky, and with collaborators from the California Institute of Technology and the Massachusetts Institute of Technology. I spent the next decade helping to build equipment and taking part in various electron scattering experiments, a number of which are the subject of the 1990 Nobel lectures. This was a period of intense activity, but also one of intense enjoyment for me. I was surrounded by people I liked and admired, and deeply involved in experiments which generated interest in laboratories and universities all over the world. I count myself extremely fortunate to have been at SLAC at that time.਀

I became a member of the SLAC faculty in 1968. In 1971, I was awarded a Guggenheim fellowship and spent an interesting sabbatical year at CERN, where I was impressed by the great progress that European science had made in the decade since I had worked in France.਀ Well before my trip to CERN, colleagues in the group at SLAC had become interested in testing some of the invariance properties of the electromagnetic interaction, a field which would absorb our efforts for most of the 1970s. When Charles Prescott joined the group in 1970, he began a serious study of ways to test parity conservation in the interaction between an electron and a nucleon. The electroweak theories of Weinberg and Salam predicted levels of nonconservation that looked extremely hard to measure. We attempted an experiment with the existing Yale polarized source, but the measurements did not reach the desired level of sensitivity. I was not very encouraging to my colleagues who wished to pursue the experiment to higher levels of accuracy. After the theoretical work of Veltman and van't Hooft and the discovery of neutral currents at CERN (during the year I was there) and at NAL (now Fermilab), the interest in experiments on parity conservation greatly intensified. In 1975 a new method for producing polarized electrons was discovered by a group in Colorado which included E.L. Garwin of SLAC. In 1978, after building a source for the linac based on the new method, we were able to demonstrate a violation of parity in close agreement with the electroweak predictions.਀

After the parity experiments, our group presented two proposals for large experimental facilities at PEP, the e+e- collider then being built at SLAC. Both those proposals were rejected. The group was finally successful in proposing a relatively small PEP detector, but I did not take part in that experiment.਀