The Nobel Prize in Physics 1990
Jerome I. Friedman, Henry W. Kendall, Richard E. Taylor
Presentation Speech by Professor Cecilia
Jarlskog of the
Royal Swedish Academy of Sciences
Translation from the Swedish text
Your Majesties, Your Royal Highnesses,
Ladies and Gentlemen,
One of the most important tasks of physics is to provide us with a clearer picture of the world we live in. We know that the observable universe is much larger than any of us could imagine and is even, perhaps, no more than just an island in an ocean of universes. But the creation also has another unfathomable frontier - that towards smaller and smaller constituents: molecules, atoms and elementary particles.
It is the business of science to probe elementary particles as well as the most remote galaxies, collecting facts and deciphering relationships at all levels of creation. The amount of information increases rapidly and without understanding can become overwhelming. Such confusion prevailed at the end of 1950s. At the deepest level of the microscopic world were the electron, the proton and the neutron, particles which for years had been considered to be the fundamental building blocks of matter. However, they were no longer alone but were accompanied by many newly discovered particles. The special roles of the proton and the neutron are evident among other things they are responsible for more than 99 percent of our weight. But what roles did the other particles play? Where had nature's elegance and beauty gone? Was there a hidden order not yet discovered by man?
There could be order but only at the price of postulating an additional, deeper level in nature - perhaps the ultimate level - consisting of only a few building blocks. Such an idea had been advanced and the new building blocks were called "quarks" - a word borrowed by the 1969 Nobel Prizewinner in Physics, Murray Gell-Mann, from "Finnegans Wake," for most of us an incomprehensible masterpiece by the great Irish novelist James Joyce. But the quark hypothesis was not alone. There was, for example, a model called "nuclear democracy" where no particle had the right to call itself elementary. All particles were equally fundamental and consisted of each other.
This year's Laureates lit a torch in this darkness. They and their coworkers examined the proton (and later on also the neutron) under a microscope - not an ordinary one, but a 2 mile-long electron accelerator built by Wolfgang K.H. Panofsky at Stanford, California. They did not anticipate anything fundamentally new: similar experiments, albeit at lower energies, had found that the proton behaved like a soft gelatinous sphere with many excited states, similar to those of atoms and nuclei. Nevertheless, the Laureates decided to go one step further and study the proton under extreme conditions. They looked for the electron undergoing a large deflection, and where the proton, rather than keeping its identity, seized a lot of the collision energy and broke up into a shower of new particles. This socalled "deep inelastic scattering" had generally been considered to be too rare to be worth investigating. But the experiment showed otherwise: deep inelastic scattering was far more frequent than expected, displaying a totally new facet of proton behavior. This result was at first skeptically received: perhaps the moving electron gave off undetected light. But this year's Prizewinners had been thorough and their findings were subsequently confirmed by other experiments.
The interpretation was given primarily by the theorists James D. Bjorken and the late Richard P. Feynman (Feynman stood in this Hall exactly 25 years ago to receive a Nobel Prize for another of his great contributions to physics). The electrons ricocheted off hard point-like objects inside the proton. These were soon shown to be identical with the quarks, thus simplifying the physicist's picture of the world; but the results could not be entirely explained by quarks alone. The Nobel Prize-winning experiment indicated that the proton also contained electrically neutral constituents. These were soon found to be "gluons," particles glueing the quarks together in protons and other particles.
A new rung on the ladder of creation had revealed itself and a new epoch in the history of physics had begun.
Dear Professors Friedman, Kendall and
On behalf of the Royal Swedish Academy of Sciences I wish to convey to you our warmest congratulations for having taken us to the land of deep inelastic scattering where the colourful quarks and gluons first revealed themselves. You will now receive the Nobel Prize from the hands of His Majesty the King.
From Nobel Lectures, Physics 1981-1990, Editor-in-Charge Tore Frängsmyr, Editor Gösta Ekspång, World Scientific Publishing Co., Singapore, 1993
Copyright © The Nobel Foundation 1990