Steven Weinberg is dead, at the age of 88. He was a leading intellectual leader in physics during the second half of the 20th century, and remained a leading voice, active collaborator and teacher during the first two decades of the 21st century.
In the lists of the greats of his time he was always mentioned along with Richard Feynman, Murray Gell-Mann and… well, just Feynman and Gell-Mann. Among his colleagues, Weinberg was one of the figures more respected than all physics or perhaps all science.
He exuded intelligence and dignity. When news of his death spread on Twitter, other physicists expressed their remorse for the loss: “One of the most skilled scientists of our time”, they commented, “A particularly eloquent spokesperson for the scientific world view”. It’s still: “One of the best physicists we’ve had, one of the best thinkers of any kind.”
The Weinberg Nobel Prize, awarded in 1979, it was for his role in developing a theory that would combine 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 of phenomena rooted in mathematics which describe subatomic particles and forces.
It is so effective in explaining the experimental results that physicists have long pursued every opportunity to find the slightest deviation, hoping to identify a “new” physics that further deepens human understanding of nature.
Steven Weinberg has also done important technical work in other areas of physics and has written several authoritative textbooks on topics such as general relativity, cosmology and quantum field theory. He was an early supporter of the superstring theory as a promising path in the ongoing quest to complete the standard model by unifying it with general relativity, Einstein’s theory of gravity.
At first, Weinberg also realized the desire to communicate more broadly. His popular book The First Three Minutes, published in 1977, introduced a generation of physicists and physics enthusiasts at the Big Bang, the birth of the universe and the fundamental science behind that metaphor.
He later wrote deeply insightful examinations on the nature of science and its intersection with society. And he’s been a longtime contributor to thoughtful essays in places like the New York Review of Books.
Steven Weinberg: a volcano of knowledge
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 “final theory” that would unify all physics. Progress towards that goal seemed to be hampered from the apparent incompatibility of general relativity with quantum mechanics, the mathematics behind the standard model.
But in a 1997 interview, Steven Weinberg argued that the difficulty of combining relativity and quantum physics in a mathematically consistent way was an important clue. “When you put the two together, you find that there really isn’t much free play in the laws of nature”, he said. “This has been a huge help to us because it’s a guide to the kind of theories that might work.”
The attempt to bridge the gap between relativity and quantum, he believed, “Pushed us to take a huge step towards the ability to develop realistic theories of nature based on mathematical calculations and pure thought alone”.
The experiment had to come into play, of course, to verify the validity of the mathematical intuitions. But the standard model worked so well that finding the deviations involved in the new physics required more powerful experimental technology than that possessed by physicists.
“We have to reach a whole new level of experimental competence before we can do experiments that reveal truth below the standard model, and this is taking a long, long time,” he said. “I really think physics in the style it is done … will eventually reach a final theory, but probably not while I am and most likely not while you are.”
He was right that he wouldn’t be around to see the final theory. And perhaps, as he has sometimes acknowledged, no one ever will. Perhaps it is not the experimental power that is lacking, but rather the intellectual power. “Humans may not be intelligent enough to understand the basic laws of physics”, wrote in his 2015 book To Explain the World, the history of science up to the time of Newton.
Weinberg studied the history of science in depth, wrote books and taught courses on it. Explaining the world aimed explicitly at evaluating ancient and medieval science in the light of modern knowledge. For this he incurred criticism from historians and others who claimed that they did not understand the purpose of history, which is to understand the human endeavors of an era in its own terms, not with anachronistic hindsight.
But Weinberg he perfectly understood the point of view of the historians, he just didn’t like it. For Weinberg, the history of science that was meaningful to people today was like the first steps towards understanding nature, and how it evolved into a foolproof system for finding correct explanations.
And it took many centuries, without the prospect of where we are now, he believed, and an appreciation of the lessons we have learned, “The story of how we got here makes no sense”.
The future historians of science perhaps they will insist on evaluating Weinberg’s work against the standards of his time. But even when viewed in the light of future knowledge, there is no doubt that Steven Weinberg’s achievements will remain in the realm of the Herculean, or the Titanic.