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Gerson Goldhaber (1924–2010)

Published onDec 01, 2011
Gerson Goldhaber (1924–2010)

Gerson Goldhaber was a leading particle physicist who turned his attention to cosmology in the latter part of career. He was the first person to assert from his interpretations of the data, and then report in professional meetings, evidence for the existence of Dark Energy. The evidence came from his study of supernova in the Berkeley Supernova Cosmology Project. In the words of Nobel laureate Sheldon Glashow, “His seminal contributions to our understanding of the smallest structures of Nature (particle physics) and to the largest (cosmology) have been truly remarkable. “ He made substantial, prize-winning discoveries in both fields. Characteristic of Goldhaber’s methods were an unrelenting and continuous pursuit to find and build capabilities to make measurements concerning the most important physics and cosmology questions of our times. He was unparalleled at forming or adding to teams in pursuit of such work, and then quickly moving to data analysis, even in early stages of the experiment. Leon Lederman noted: “Gerson's vitality, intellectual weight, ideas, and presence saved the experiment and directly led to its success. Such teamwork and selflessness is rarely acknowledged in prizes…. His energy, taste in research, imagination and his impressive bibliography indicate Goldhaber to be one of the major figures in the evolution of this field of research, now called “particle astrophysics.” Goldhaber’s uncanny data-analysis skills enabled him to continually invent new methods of analysis and displays of very complex data, and he often was the most enthusiastic member of the team in isolating the most important variables and encouraging the team to see their role in an existing or new physical phenomena. Goldhaber helped lead or co-lead teams but was always involved in deep data analysis, whether the data be quarks or high-redshift supernova. Indeed, his prize-winning work spans 1043 orders of magnitude of length-scale, from the size of quarks — ~10-14 cm to the entire size of the visible Universe — ~ 1029 cm.

Goldhaber was also widely regarded as one of the kindest, most open, and friendly physicists at Lawrence Berkeley Laboratory, and his collegiality and attempts to build group esprit-de-corp were a large part of the group’s success, when financial and other issues were always on the verge of ending the work. Indeed, Goldhaber led considerable weight to the effort.

Goldhaber was born in Chemnitz, Germany, Feb. 20, 1924, and moved with his family to Cairo, Egypt, in 1933 to escape Nazi persecution. He earned his Master’s of Science degree in physics at Hebrew University, Jerusalem, in 1947 and his Ph.D. in 1950 from the University of Wisconsin. He became a naturalized United States citizen in 1953 while working as an instructor at Columbia University. Later that same year, he joined the UC Berkeley Physics Department and the research staff at its Radiation Laboratory, which would later morph into Berkeley Lab, a U.S. Department of Energy national laboratory.

Goldhaber first rose to major scientific prominence with his contributions to the discovery of the antiproton. In collaboration with his first wife, nuclear chemist/physicist Sulamith Löw, Goldhaber led a group that used a photographic emulsion detector technique he developed to confirm the discovery of the antiproton at Berkeley Lab’s Bevatron accelerator by the research group of Emilio Segrè and Owen Chamberlain. Segrè and Chamberlain received the Nobel Prize in 1959 for this discovery.

In 1960, Goldhaber and physicist George Trilling formed the Trilling-Goldhaber experimental particle-physics group, which included his wife, Sulamith. In 1963, the group discovered the A meson, a subatomic particle Goldhaber named after his son, Amos Nathaniel. “The wisest professional decision I ever made was to join Gerson in a collaboration whose success resulted almost entirely from his extraordinary insight into where to find new and important science,” said Trilling. “He was a great physicist and a wonderful human being.”

In 1965, shortly after arriving in India on a family trip around the world, Sulamith Goldhaber went into a coma and died. For solace, Goldhaber took up art, working in various media before gravitating to paintings and drawings. In 1969, he married Judith Margoshes Golwyn, playwright, poet, and for many years a lead science writer at Berkeley Lab. During their 41-year marriage, Gerson and Judith collaborated on many art projects and articles on scientific subjects. They also raised two daughters, Michaela and Shaya.

In 1972, the Trilling-Goldhaber group began a collaboration with a group led by physicist Burton Richter at the Stanford Linear Accelerator Center (SLAC), on an experiment with SLAC’s Stanford Positron-Electron Asymmetric Ring. The collaborators built a machine that was initially called the SLAC-LBL Solenoidal Magnetic Detector, later known as the Mark I detector.

With Goldhaber leading the data analysis, the Stanford-Berkeley collaborators in November of 1974 announced the discovery of a new subatomic particle that turned out to be the first member of the “charm” flavor of quarks. Goldhaber proposed the particle be named “psi” for the Greek letter, because its particle tracks formed a pattern that resembled the psi symbol. The same particle was almost simultaneously discovered by a collaboration at Brookhaven National Laboratory led by MIT physicist Samuel Ting. The Brookhaven group called their discovery the “J” particle. As leaders of the two collaborations, Richter and Ting won the 1976 Nobel Prize for the discovery of what is now known as the J/psi particle.

In 1989 Goldhaber shifted his considerable intellectual focus to astrophysics, and became one of the first members of Berkeley Lab’s Deep Supernova Search. Founded by Richard Muller, Carl Pennypacker, and Saul Perlmutter, this group would later be renamed the Supernova Cosmology Project (SCP). Goldhaber switched his research interests from particle physics to cosmology in 1989 partly because his wife Judith was collaborating with astrophysicist Carl Pennypacker in writing a musical (which was later produced) based on the life and ideas of Stephen Hawking, entitled Falling Through a Hole in the Air, with lyrics by Judith and music by Carl. Gerson thus had many opportunities to talk about cosmology and became intrigued with it. By 1997 the SCP group had collected and analyzed 38 of the Type Ia supernovae “standard candles” in sufficient detail to take a stab at measuring the expansion rate of the universe.

Judith felt that her husband was courageous in changing his field of research from particle physics to cosmology at this point in his career. ‘‘He had reached a prominent level in particle physics. When he went to physics conferences he’d be at the head table and giving the keynote talks.’’ (Interview with Judith Goldhaber, p. 138) When he switched to astrophysics, he worked in relative obscurity—until the discovery of dark energy.

As Ursula Pavlish described ("Gerson Goldhaber: A Life in Science," 2011, Physics in Perspective 13, 189-214), "At that time scientists believed that the ultimate fate of the expanding universe depended on the density of matter it contained, its so-called Omega Mass (ΩM). Above a certain value, gravity would eventually slow down the expansion, and galaxies would begin to move closer together; below that value, the universe would expand forever. The SCP group proposed to measure ΩM by analyzing the light from distant supernovae and calculating their distances from our solar system. An exploding supernova burns up the entire star within seconds, typically producing light as bright or brighter than that of an entire galaxy, but all Type Ia supernovae produce light of essentially the same maximum brightness, so they can be used as ‘standard candles’ in calculating their distances from our solar system. In particular, just after a new moon, a series of reference images—photographs showing galaxies in a certain portion of the night sky—are taken, and three weeks later, just before the next new moon, another set of photographs is taken, the new points of light on which are supernovae whose brightnesses and redshifts are carefully measured and analyzed to determine how fast they are retreating owing to the expansion of the universe."

"Goldhaber showed his discovery of a peak in the SCP data to his team members at the LBL and gave a talk on it in Santa Barbara, California, on December 14, 1997, where Robert Kirshner, one of the leaders of the competing High-z Supernova Search Team, was in the audience. Kirshner did not affirm the significance of the SCP data, perhaps because Goldhaber’s unusual particle-physics method of analysis was unfamiliar to astrophysicists. In any case, Goldhaber recalled that David Gross asked him, ‘‘Can you be sure with such small statistics?’’ Goldhaber answered, ‘‘Yes, I am sure.’’ (I 9, pp. 10–11)"

"Saul Perlmutter actually had presented the teams’s results even earlier, in the fall of 1997, in Santa Cruz, California. Goldhaber and his co-workers’ analysis, as well as similar results developed independently by the High-z Supernova Search Team led by Kirshner, Adam Riess, and Brian Schmidt, soon confirmed Goldhaber’s gut reaction that ‘it looked convincing.’"

These bumps found by Goldhaber were studied by the Berkeley group for some time, to understand if dust or other systematics were confusing such measurements, but no such systematic effect could be found.

Both teams published in 1998, and such work lead to the Nobel Prizes for the team leaders, in 2011.

Photo courtesy of Judith Goldhaber.

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