During a long career spent in the exploration of the most basic problems of physics and cosmology, he won lasting renown as a creator of an “electroweak” theory that unifies electromagnetism and the “weak” force that operates on the subatomic scale and is one of the four forces that govern the universe.
The electroweak theory lies at the core of what physicists know as the Standard Model, a framework that guides physics in accounting for all the particles from which the world is made, and for how they influence one another.
Over a long career, Dr. Weinberg produced many books and hundreds of scientific papers at the frontiers of his discipline. Ideas, according to the stories told in the literature of physics, came to him everywhere — seated on a park bench, driving to work, at home in his study with the television playing in the background.
In awarding him its Benjamin Franklin Medal in 2004, the American Philosophical Society said he was “considered by many to be the preeminent theoretical physicist alive in the world today.”
Not many years before Dr. Weinberg came upon the physics scene, in the years shortly after World War II, science had reduced to four the number of fundamental forces that acted in the world around us. These were the relatively familiar forces of electromagnetism and gravity as well as two forces that act on subatomic particles, the strong force and the weak force.
Years of pioneering work, along with the new availability of powerful atom-smashing machines, made it possible to split apart what had once seemed to be the irreducible constituents of matter. New particles appeared in profusion, intensifying the urgency of a search to explain this unseen world and its laws.
“Our job in physics is to see things simply, to understand a great many complicated phenomena in a unified way,” Dr. Weinberg said in the science lecture he delivered as part of the ceremonies connected to his Nobel Prize.
In a way, his own work provided a prime example of unification.
Electromagnetism is well known from everyday life and lies at the heart of so many of the devices that have revolutionized society, from computers to communications. It in itself represents a unification, of electricity and magnetism.
The weak force is one that is unseen in daily life and exists at the subatomic level, accounting for the radioactive decay of certain particles into certain others. It also underlies, although invisibly, the process that supplies the energy needed for life: It accounts for the initial step in the nuclear fusion reaction that powers the sun.
His work in showing how electromagnetism and the weak force could be jointly viewed as the electroweak force was made known to the world in a paper published in 1967 in Physical Review Letters.
The 2 1/2-page submission became in time one of the most quoted papers in the world of particle physics.
Illuminated by a variety of earlier concepts, theories and suggestions, it offered a theory that required the existence of particles yet undiscovered.
Two were known as weak vector bosons and given the names of W and Z. In physical theory, bits of matter on the subatomic scale exert forces on one another through the exchange of particles. The Z particle is electrically neutral, and an exchange of such particles is known as a neutral current.
In time the particles and the neutral current were found. The discoveries of the W and the Z were regarded by science as a confirmation of Dr. Weinberg’s theory.
In announcing the award of the Nobel Prize in physics in 1979 for contributions to the theory of the unified weak and electromagnetic interactions, the prize committee specifically noted that the theory had predicted the weak neutral current.
The prize was shared by Dr. Weinberg and two other physicists, Sheldon Glashow and Abdus Salam. All three had worked independently of one another.
In Dr. Weinberg’s paper, a need was also implied for another particle, to provide mass. This particle was what in time became known as the Higgs boson. It became important to physics for many reasons beyond the scope of Dr. Weinberg’s work, and its ultimate discovery gained widespread attention.
In addition to his work in science, Dr. Weinberg was known as a cultured man fond of poetry and the theater, and he gave attention to the philosophical and metaphysical aspects of the scientific quest. Like many others who also sought to know nature at its essence, he speculated on the meaning of scientific discovery for human life and the human place in the universe.
Beyond the vast scholarly output, he was highly regarded as a popularizer of science and praised for his clarity of expression. One of several books addressed to a general audience, “The First Three Minutes” (1977), sought to describe the development of the universe in the first seconds after creation. Another of his books, on the history of science, was titled “To Explain the World” (2015).
“I think it’s very important not to write down to the public,” he told the publication Third Way. “You have to keep in mind that you’re writing for people who are not mathematically trained but are just as smart as you are.”
His popular works took their place alongside such more abstruse tomes that he also produced, such as “Gravitation and Cosmology” (1972) and “The Quantum Theory of Fields” (1995).
He weighed in on public controversies, opposing a state law that would permit the carrying of concealed handguns in his classroom.
Steven Weinberg was born in New York City on May 3, 1933, and recalled that his interest in science stemmed in part from the chemistry set he had as a child.
He graduated in 1950 from the Bronx High School of Science, a public high school renowned for training the children and grandchildren of immigrants and transforming many into Nobel winners. Glashow, with whom he shared the Nobel, also went there, at the same time.
Dr. Weinberg received a bachelor’s degree from Cornell University in 1954, then spent a year in Copenhagen at what was then the Institute for Theoretical Physics. He obtained a doctorate in physics from Princeton University in 1957.
From 1959 to 1966, he worked at the Berkeley campus of the University of California. At Berkeley, in his 20s, he stood out among the many physics department luminaries merely by his physical appearance: He had a shock of hair of a color that was almost flame-red, and his expression conveyed a look of special urgency and intensity.
On leave from Berkeley in the late 1960s, he lectured at Harvard and served as a visiting professor at MIT. While at MIT in 1967, he published his celebrated paper on unification. He became a professor of physics at Harvard in 1973 and moved nine years later to the University of Texas as a professor of science.
In 1954, he married Louise Goldwasser, who became a legal scholar. In addition to his wife, survivors include their daughter, Elizabeth.
A statement Dr. Weinberg once made about the implications of seeing the universe at its deepest level created controversy. “The more the universe seems comprehensible,” he said, “the more it also seems pointless.”
He rejected any criticism that he was being nihilistic.
“If there is no point in the universe that we discover by the methods of science,” he told PBS, “there is a point that we can give the universe by the way we live, by loving each other, by discovering things about nature, by creating works of art.”
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