Physicist Steven Weinberg was born #OTD in 1933. His 1967 paper "A Model of Leptons" presented a unified theory of the electromagnetic and weak nuclear interactions, and is the most cited paper in particle physics.
Besides his groundbreaking work in particle physics, Weinberg is known for contributions to cosmology and astrophysics, as well as numerous textbooks and popular works.
Image: AIP Emilio Segrè Visual Archives
Weinberg submitted "A Model of Leptons" to Physical Review Letters in October of 1967. It describes a key component of the Standard Model, and is the most cited particle physics paper in inSPIRE.
His model describes a unified electroweak interaction at high energies. At low energies, spontaneously broken gauge symmetry gives mass to the W and Z bosons, while the photon remains massless. The result is a short range weak force and a long range electromagnetic interaction.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.19.1264
“It’s what keeps you going as a theoretical physicist to hope that one of your squiggles will turn out to describe reality.”
They were very good squiggles!
https://home.cern/news/news/cern/50-years-iconic-model-leptons-published
Today, 50 years ago, Steven Weinberg published the iconic paper A Model of Leptons, which determined the direction for high-energy particle physics research from them on. This paper lies at the core of the Standard Model, our most complete theory of how particles interact in our universe. Just two pages long, Weinberg’s elegant and simply written theory was revolutionary at the time, yet was virtually ignored for many years. But now, it is cited at least three times a week. Proving the validity of Weinberg’s theory inspired one of the biggest experimental science programmes ever seen and CERN has built major projects with these discoveries at their heart: the Gargamelle bubble chamber found the first evidence of the electroweak current in 1973; the Super Proton Synchrotron showed, in 1982, the first evidence of the W boson; and most recently the Large Hadron Collider, in 2012, confirmed the existence of the Higgs Boson. Steven Weinberg visiting the ATLAS collaboration in 2009. (Image: Maximilien Brice/CERN) Speaking to the CERN Courier Weinberg, now 84, describes what it’s like to see his work confirmed: “It’s what keeps you going as a theoretical physicist to hope that one of your squiggles will turn out to describe reality.” He received the Nobel Prize for this iconic, game-changing theory in 1979. Read more about the original theory, and an interview with Steven Weinberg in this month’s CERN Courier.
If you haven't already, I encourage you to read Weinberg's "The First Three Minutes," a beautifully written particle physics history of the Hot Big Bang. If you have, I encourage you to read it again.
It was last updated in 1993, so in some ways it is outdated (inflation, dark energy). But it's a classic. My copy is tattered from re-reading.
"The First 3 Minutes" opens with a creation story: the frost giant Ymir, the primeval cow Auðumbla, and the yawning void Ginnungagap.
My favorite popularizations of cosmology, whether Norse or modern, all begin with this story.
He also wrote this in his cosmology textbook. Funny and relatable as a matter-of-fact statement, but also my favorite inadvertent physics humblebrag.
"Look, I tried to recreate the mistakes, but my brain just kept replacing them with the correct results."
Steven Weinberg passed almost two years ago. He was a towering figure of 20th and 21st century physics and I admired him tremendously. I read his books to pieces, joined his research group at UT-Austin, learned Cosmology from him, graded his courses, read drafts of his textbooks.
Let me share a things he wrote, some of which I've written about at length on here, all of which are worth your time. No attempt to be comprehensive or even representative in what follows!
First, “What is Quantum Field Theory, and What Did We Think It Is?” A short, personal history of the development of quantum field theory and a lovely explanation of our modern understanding of QFTs as Effective Field Theories.
Next, “The Cosmological Constant Problem.”
Weinberg’s classic review of the catastrophic mismatch between the amount of vacuum energy measured by cosmologists and astronomers, and the predictions made by quantum mechanical theories of particle physics.
Imo this remains one of the most intriguing problem in all of physics. The paper was published about ten years before the discovery of the accelerating Hubble expansion likely driven by a minuscule positive vacuum energy.
https://repositories.lib.utexas.edu/bitstream/handle/2152/61094/Weinberg_1989.pdf
“Living in the Multiverse”
An opening talk for a conference in which Weinberg confronts the String Landscape and its anthropic implications. “We lose some, and win some.”
One time, when I was in grad school, I asked Weinberg about some point from the anthropic discussion in the 1989 review paper. He gave me a funny look and said that people my age shouldn’t be flirting with anthropic reasoning, we should try to come up with real solutions.
And finally, this fun little bit from his book “Gravitation and Cosmology.”
A great book, but a common complaint is that it is maybe not the best place to learn GR.
On the other hand, does your favorite GR textbook tackle the really big questions like “Is Middle Earth flat?”
Anyway, here is a remembrance of Weinberg in Physics Today, with stories and anecdotes from me, @preskill, and others:
https://pubs.aip.org/physicstoday/Online/5387/Steven-Weinberg-1933-2021
Oh, and please take just a few minutes to watch this wonderful animated conversation with Weinberg.
“The effort to understand the universe is one of the very few things that lifts human life a little above the level of farce, and gives it some of the grace of tragedy.”
— Steven Weinberg, The First Three Minutes
@mcnees That seems fair, and I'll defer to your expertise — not least for your point that experts are (of course) human like everyone else. That said, it's a real problem when they forget that, something I was thinking about this AM.
https://tldr.nettime.org/@tb/110305059398760859
And thank you for your thoughtful reply, which my own cantankerous one maybe didn't deserve.
I realized just now that "impostor syndrome" is one of these psycho-social phenomena that'll spread and spread, chewing up and spitting out whole demographics tranche by tranche. And as more and more people are convinced they're somehow "fake," #AI will fill the gap with a new "real." Signs of this happening are everywhere already.
Love this whole Weinberg tribute thread. In many of your OTD posts, you weave in beautiful anecdotes about the quiet, graceful humanity of the person. I find this Weinberg example very touching in his perceptual awareness of the situation that prompted him to gift you the book. Another shining example you told of this kind of perceptual awareness by a prominent person recognizing how a simple act could benefit others is the magnificent Joe Polchinski anecdote at https://twitter.com/mcnees/timelines/805900100862115841
@mcnees Does he find a positive curvature ?
Tolkien lore says that the Earth got round at some point before the Lord of the Rings takes place (but the final resting places of the Elves did not move, so that now it's up in the skies).
@legendarybassoon Yes! We can see this explicitly. Given four points on a flat plane there are six distinct pairs of points. The distances between them should satisfy a constraint.
Here it is, illustrated with six random points on a 10,000 x 10,000 grid.
@mcnees I'm very happy ! Now how much is it curved ? If it were a sphere, how much of the sphere would be covered by the usual Middle earth map?
I hope it doesn't wrap around several times...
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