From nuclear weapons to solar neutrinos, black holes to quarks, Napoleon and Tolstoy to current science policy - it was all on the table as friends, colleagues and Cornell honored Hans Albrecht Bethe last week.
In a Physics Department symposium March 31-April 1 that included a public convocation, "Celebrating 60 Years at Cornell with Hans Bethe," speakers that included some of the nation's most illustrious scientists and educators contributed with a wide range of topics, all of which were of import to Bethe at some time during the past 60 years or more.
Lauded by colleagues as the "social conscience of physics," the "father of nuclear physics" and the world's "Dean of Physics," Bethe was feted with scientific talks and public discussions about the smallest constituents of matter, nuclear non-proliferation and the state of basic research today.
Bethe, 88, came to Cornell in 1935 and never left, except to head the Theoretical Division at Los Alamos, N.M., for the Manhattan Project during World War II. He spent many subsequent years as an influential advocate of nuclear disarmament.
The John Wendell Anderson Professor of Physics Emeritus, Bethe won the Nobel Prize in physics in 1967 for solving the problem of energy production in stars. "I can do that," Bethe said, remembering the pre-war days when he looked at the problem that had dogged other physicists of the 1930s. And he did.
Indeed, said Gerald Brown, a physicist at the State University of New York at Stony Brook and Bethe collaborator, it did not take Bethe long to solve many difficult problems. Seventeen years ago to the day - April 1, 1978 - Brown left a problem for Bethe on his desk in Copenhagen, where Bethe was about to visit. The problem concerned what happens to a star when its nuclear fuel is spent.
"By 10 a.m. the next day, he had solved the problem of the collapse of stars," Brown told the symposium audience in Schwartz Auditorium, Rockefeller Hall. "The mechanism of stellar collapse was described."
In his talk during the scientific symposium, "Supernova Explosions, Black Holes and Nucleon Stars," Brown described the latest research into how stars collapse and form black holes.
"The core grows and then, after 10 million years of burning, collapses in just a few seconds," he said. "Electrons are eaten by protons; neutrons go out into space."
And showing that Bethe's productivity has not slackened, Brown described a recent collaboration in which he and Bethe calculated the maximum mass of neutron stars (about 1.5 solar masses). Their paper is in press, due to be published in Applied Journal Letters.
"We believe we've pinned down the maximum mass of neutron stars," he said, adding that most main sequence stars explode and return mass to the galaxy, forming a low-mass black hole. "It may be there are as many black holes as stars in the universe," he said.
Bethe gave a technical talk as well, on "Solar Neutrinos." Speaking to a packed auditorium and finishing to a standing ovation, Bethe described his theories of neutrinos emanating from the sun and bombarding the Earth. They come in different flavors - low energy, "which get to Earth 100 percent," he said, and high-energy neutrinos, "which on the other hand come out of the sun . . . and are unobservable" by the same radioactive-based detectors used for other particles.
He described that in 1934 he wrote a letter to Nature magazine, in which he said that "the free neutrino probably never will be observed. This talk is based on observing them."
Underground experiments around the world are being made to detect high-energy neutrinos. And with at least one of the experiments, he said, "You can get an exact value of the central temperature of the sun. That would be something, because we can't even get that for the surface."
On Friday, the symposium featured talks by Silvan S. Schweber of Brandeis University and Bethe's biographer, who summarized Bethe's career, both as a first-rate scientist and as a man of social conscience. Bethe had "enormous self-confidence" in both respects, Schweber said. "No calculation bothers him." Andre LeClair, Cornell assistant professor of physics, described "Just Over 60 Years of Bethe's Ansatz," concerning a 1931 paper in which Bethe solved a problem that still is used in physics and mathematical physics. "It's his most cited work," LeClair said, eclipsing even the 1935 paper that explains how stars shine. LeClair also showed photographs of the last blackboards of Richard Feynman, the late Nobel physicist who studied under Bethe at Cornell. Feynman was working on Bethe equations when he died, LeClair said.
Also during the scientific session on Friday, John Bahcall of the Institute for Advanced Study at Princeton University described recent results from the Hubble Space Telescope. "In just a little over a year (since Hubble's correction), we have a very rich set of scientific results. We have great things to look forward to," he said.
Among Hubble's accomplishments, he said, was that it proved that faint red stars were not the source of dark, or missing, matter, as some scientists had proposed. It also showed a galaxy had a double nucleus where it was thought there was one, and proved there was not a triple nucleus to another galaxy - instead, astronomers were viewing two other objects behind the galaxy.
Among his slides were Hubble photos of an "extraordinary quasar directly behind the center of a galaxy." This "1-in-1-million" opportunity was made into a false-color image and put in a framed print, which Bahcall presented to Bethe at the end of his talk.
Also Friday, Kenneth G. Wilson, who won the Nobel Prize in physics in 1982 while at Cornell and now is at Ohio State University, described in a technical talk quarks and other constituents of matter. .