Mythology has its titans. So do the movies. And so does physics. Just one fewer now.
Steven Weinberg died July 23, at the age of 88. He was one of the key intellectual leaders in physics during the second half of the 20th century, and he remained a leading voice and active contributor and teacher through the first two decades of the 21st.
On lists of the greats of his era he was always mentioned along with Richard Feynman, Murray Gell-Mann and тАж well, just Feynman and Gell-Mann.
Among his peers, Weinberg was one of the most respected figures in all of physics or perhaps all of science. He exuded intelligence and dignity. As news of his death spread through Twitter, other physicists expressed their remorse at the loss: тАЬOne of the most accomplished scientists of our age,тАЭ one commented, тАЬa particularly eloquent spokesman for the scientific worldview.тАЭ And another: тАЬOne of the best physicists we had, one of the best thinkers of any variety.тАЭ
WeinbergтАЩs Nobel Prize, awarded in 1979, was for his role in developing a theory unifying electromagnetism and the weak nuclear force. That was an essential contribution to what became known as the standard model of physics, a masterpiece of explanation for phenomena rooted in the math describing subatomic particles and forces. ItтАЩs so successful at explaining experimental results that physicists have long pursued every opportunity to find the slightest deviation, in hopes of identifying тАЬnewтАЭ physics that further deepens human understanding of nature.
Weinberg did important technical work in other realms of physics as well, and wrote several authoritative textbooks on such topics as general relativity and cosmology and quantum field theory. He was an early advocate of superstring theory as a promising path in the continuing quest to complete the standard model by unifying it with general relativity, EinsteinтАЩs theory of gravity.
Early on Weinberg also realized a desire to communicate more broadly. His popular book The First Three Minutes, published in 1977, introduced a generation of physicists and physics fans to the Big BangтАУbirth of the universe and the fundamental science underlying that metaphor. Later he wrote deeply insightful examinations of the nature of science and its intersection with society. And he was a longtime contributor of thoughtful essays in such venues as the New York Review of Books.
In his 1992 book Dreams of a Final Theory, Weinberg expressed his belief that physics was on the verge of finding the true fundamental explanation of reality, the тАЬfinal theoryтАЭ that would unify all of physics. Progress toward that goal seemed to be impeded by the apparent incompatibility of general relativity with quantum mechanics, the math underlying the standard model. But in a 1997 interview, Weinberg averred that the difficulty of combining relativity and quantum physics in a mathematically consistent way was an important clue. тАЬWhen you put the two together, you find that there really isnтАЩt that much free play in the laws of nature,тАЭ he said. тАЬThatтАЩs been an enormous help to us because itтАЩs a guide to what kind of theories might possibly work.тАЭ
Attempting to bridge the relativity-quantum gap, he believed, тАЬpushed us a tremendous step forward toward being able to develop realistic theories of nature on the basis of just mathematical calculations and pure thought.тАЭ
Experiment had to come into play, of course, to verify the validity of the mathematical insights. But the standard model worked so well that finding deviations implied by new physics required more powerful experimental technology than physicists possessed. тАЬWe have to get to a whole new level of experimental competence before we can do experiments that reveal the truth beneath the standard model, and this is taking a long, long time,тАЭ he said. тАЬI really think that physics in the style in which itтАЩs being done тАж is going to eventually reach a final theory, but probably not while IтАЩm around and very likely not while youтАЩre around.тАЭ
He was right that he would not be around to see the final theory. And perhaps, as he sometimes acknowledged, nobody ever will. Perhaps itтАЩs not experimental power that is lacking, but rather intellectual power. тАЬHumans may not be smart enough to understand the really fundamental laws of physics,тАЭ he wrote in his 2015 book To Explain the World, a history of science up to the time of Newton.
Weinberg studied the history of science thoroughly, wrote books and taught courses on it. To Explain the World was explicitly aimed at assessing ancient and medieval science in light of modern knowledge. For that he incurred the criticism of historians and others who claimed he did not understand the purpose of history, which is to understand the human endeavors of an era on its own terms, not with anachronistic hindsight.
But Weinberg understood the viewpoint of the historians perfectly well. He just didnтАЩt like it. For Weinberg, the story of science that was meaningful to people today was how the early stumblings toward understanding nature evolved into a surefire system for finding correct explanations. And that took many centuries. Without the perspective of where we are now, he believed, and an appreciation of the lessons we have learned, the story of how we got here тАЬhas no point.тАЭ
Future science historians will perhaps insist on assessing WeinbergтАЩs own work in light of the standards of his times. But even if viewed in light of future knowledge, thereтАЩs no doubt that WeinbergтАЩs achievements will remain in the realm of the Herculean. Or the titanic.
