Steven Weinberg has sadly passed away today at the age of 88. Typically, whenever I hear about an influential physicist passing away, I often talk about their achievements and contribution to physics. However, it’s hard to do that for Weinberg because firstly, even going through just his major achievements and explaining them is a massive undertaking in itself since Weinberg has had a huge impact on most areas of modern physics — from particle to nuclear physics to cosmology to quantum gravity etc. — and anyone who knows anything about physics is probably already aware of his contributions and his genius. Secondly, even though I never met Weinberg, he had a very personal impact on my life and though I am a bit irreverent towards the notion of having ‘idols,’ I can say that Weinberg was a personal hero of mine, certainly when it comes to physics. This makes it harder to write an exposition on what he did because I am truly saddened by his death. Hence, this blog is more of a personal reflection of some of his work and its influence on my life.
Throughout my intellectual development, Weinberg’s influence has not been far away. I read his book The First Three Minutes, which focused on early universe cosmology, in my teens and found his explanations lucid as ever. I could obviously never read his papers back then or go through the catalog of his excellent textbooks; still, I focused on watching his many videos on YouTube back then. In fact, but one of my motivations for studying physics was that I could understand his papers. I remember during undergrad how giddy with happiness I was when any lecturer would even mention the name Weinberg and the absolute catharsis when during my particle physics lecture, I heard the term ‘Weinberg angle’ as we started to learn more and more about the Weinberg-Salam model. I remember how excited I felt that I was finally starting to grasp the technical details of Weinberg’s contribution to physics which landed him a Nobel Prize.
Later on, I read his ‘pop’ book Dreams of Final Theory and I learned the plethora of information that I thought I could never gain from a popular book at that stage. It’s rich with the history of particle physics which tries to highlight why unification was (and is) such a big deal in the subject, his debates with the biologist Ernst Mayr on emergentism v/s reductionism, philosophy of science, his scorn for positivism, and ultimately why there is a need for a final theory. This book is probably the best popular science book that I have ever read (popular in the sense there is little mathematical detail but that does not circumvent the rich conceptual and historical details that Weinberg goes to). Nima Arkani-Hamed described it along the lines of ‘the deepest popular science book you’ll ever read’ which I think is an apt description of it.
During my postgrad, I read some of his textbooks on quantum mechanics (QM) which were different than most books on QM that I had read since Weinberg forgoes the state vector notation. I wrestled (and still do) with his volumes (bits of the first two, I have never tried picking up the third) on Quantum Field Theory (QFT) and I hope I can get through them someday. I invested and bought his textbook on cosmology that sits on my shelf and I use it as a reference book. When it comes to philosophy of science, I think his article The Revolution That Didn’t Happen is one of the best criticisms of Kuhn’s work. Even at 88 years old, Weinberg continued to work; he just published a whole textbook, Foundations of Modern Physics, just a few months ago and was participating in workshops and seminars online. His last paper on effective field theory came out earlier this year (based on an earlier lecture he gave last year), and I have been slowly chipping away at it for the past few days. The topic of my master’s thesis was built around effective field theory (of which Weinberg was one of the earlier pioneers) and once again I was learning from Weinberg’s work directly.
I have just glossed over most of his work that influenced me, but I hope this communicates somewhat how from my teens till now, Weinberg’s work in one form or another has been a constant presence in my life and I owe a lot to him for my intellectual growth. Three years ago, I started to read his book Third Thoughts and he mentions in that book how he thinks it’s probably going to be his last book since he wouldn’t survive to write 4th thoughts (this was his third essay collection that was published). I remember the absolute sadness I felt because I knew that given his age, he was probably right but I wanted him to be wrong. Sadly, as is more often than not, he was right and he has died today, about 3 years after the book’s publication. I am deeply saddened by his death and it’s weird to feel that way about a person who has had a major influence on your life but they are probably not even aware of your existence, even though I know I am not alone in feeling like this. Today is a sad day for physics as a whole because we truly lost one of the last few remaining 20th century titans of the field. Weinberg lived a long and very productive life. Weinberg has immortalized himself with his work. You can count on about two hands the number of physicists in the history of humanity who have successfully worked on unification; Weinberg was one of them, thus joining the ranks of Maxwell, Einstein, and Newton. Even though Weinberg, the person (the first-person subjective experience he had of himself) has passed away, he will live on through his work and in the thoughts of people who have been influenced by his work — and there are many.