Of Particular Significance

Tag: quantum field theory

So Much News, So Little Time

[No AI was used in composing this blog post.]

I’ve been trying to get back to the blog recently. But every time I plan to write a blog post, something happens that requires my attention and adds to the list of items I should be writing about.

I’ve decided that the best I can do, for now, is to summarize some of the key stories that have been on my radar. The overarching news, aside from the 2026 physics Nobel Prize, is what you’ve heard: artificial intelligence (AI) is transforming mathematics and high-energy theoretical physics, no question. That said, what is reported in the media about this is usually wrong in key details, and almost always wildly overstates what’s been accomplished. Nevertheless, the advances in AI models in the last couple of months are historic and transformative, and there is every reason to expect this to accelerate. For people like me, 2027 will surely be very different from autumn 2026, which in turn barely resembles spring 2026.

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POSTED BY Matt Strassler

ON October 30, 2026

A New Interview

A pause from my quantum series to announce a new interview on YouTube, this one on the Blackbird Physics channel, hosted by UMichigan graduate student and experimental particle physicist Ibrahim Chahrour. Unlike my recent interview with Alan Alda, which is for a general audience, this one is geared toward physics undergraduate students and graduate students. A lot of the topics are related to my book, but at a somewhat more advanced level. If you’ve had a first-year university physics class, or have done a lot of reading about the subject, give it a shot! Ibrahim asked great questions, and you may find many of the answers intriguing.

Here’s the list of the topics we covered, with timestamps.

00:00 Intro
00:40 Why did you write “Waves in an Impossible Sea”?
03:50 What is mass?
09:03 What is Relativistic Mass? Is it a useful concept?
17:50 Why Quantum Field Theory (QFT) is necessary
23:50 Electromagnetic Field, Photons, and Quantum Electrodynamics (QED)
36:17 Particles are ripples in their Fields
38:47 Fields with zero-mass particles vs. ones whose particles have mass?
46:49 The Standard Model of Particle Physics
52:08 What was the motivation/history behind the Higgs field?
1:02:05 How the Higgs field works
1:05:33 The Higgs field’s “Vacuum Expectation Value”
1:12:02 The hierarchy problem
1:24:18 The current goals of the Large Hadron Collider

POSTED BY Matt Strassler

ON March 17, 2025

The Particle and the “Particle” (Part 2)

In my last post, I looked at how 1920’s quantum physics (“Quantum Mechanics”, or QM) conceives of a particle with definite momentum and completely uncertain position. I also began the process of exploring how Quantum Field Theory (QFT) views the same object. I’m going to assume you’ve read that post, though I’ll quickly review some of its main points.

In that post, I invented a simple type of particle called a Bohron that moves around in a physical space in the shape of a one-dimensional line, the x-axis.

I discussed the wave function in QM corresponding to a Bohron of definite momentum P₁, and depicted that function Ψ(x₁) (where x₁ is the Bohron’s position) in last post’s Fig. 3.
In QFT, on the other hand, the Bohron is a ripple in the Bohron field, which is a function B(x) that gives a real number for each point x in physical space. That function has the form shown in last post’s Fig. 4.

We then looked at the broad implications of these differences between QM and QFT. But one thing is glaringly missing: we haven’t yet discussed the wave function in QFT for a Bohron of definite momentum P₁. That’s what we’ll do today.

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POSTED BY Matt Strassler

ON February 25, 2025

The Particle and the “Particle” (Part 1)

Why do I find the word particle so problematic that I keep harping on it, to the point that some may reasonably view me as obsessed with the issue? It has to do with the profound difference between the way an electron is viewed in 1920s quantum physics (“Quantum Mechanics”, or QM for short) as opposed to 1950s relativistic Quantum Field Theory (abbreviated as QFT). [The word “relativistic” means “incorporating Einstein’s special theory of relativity of 1905”.] My goal this week is to explain carefully this difference.

The overarching point:

in QM, an electron really is a particle, at least to the limited extent that QM can handle that notion;
in QFT, an electron is at best a “particle”, with the word in quotation marks
- (and I personally prefer the term wavicle.)

I’ve discussed this to some degree already in my article about how the view of an electron has changed over time, but here I’m going to give you a fuller picture. To complete the story will take two or three posts, but today’s post will already convey one of the most important points.

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POSTED BY Matt Strassler

ON February 24, 2025

Elementary Particles Do Not Exist (Part 2)

[An immediate continuation of Part 1, which you should definitely read first; today’s post is not stand-alone.]

The Asymmetry Between Location and Motion

We are in the middle of trying to figure out if the electron (or other similar object) could possibly be of infinitesimal size, to match the naive meaning of the words “elementary particle.” In the last post, I described how 1920’s quantum physics would envision an electron (or other object) in a state |P₀> of definite momentum or a state |X₀> of definite position (shown in Figs. 1 and 2 from last time.)

If it is meaningful to say that “an electron is really is an object whose diameter is zero”, we would naturally expect to be able to put it into a state in which its position is clearly defined and located at some specific point X₀ — namely, we should be able to put it into the state |X₀>. But do such states actually exist?

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POSTED BY Matt Strassler

ON February 11, 2025

Public Talk at the University of Michigan Dec 5th

This week I’ll be at the University of Michigan in Ann Arbor, and I’ll be giving a public talk for a general audience at 4 pm on Thursday, December 5th. If you are in the area, please attend! And if you know someone at the University of Michigan or in the Ann Arbor area who might be interested, please let them know. (For physicists: I’ll also be giving an expert-level seminar at the Physics Department the following day.)

Here are the logistical details:

The Quantum Cosmos and Our Place Within It

Thursday, December 5, 2024, 4:00-5:00 PM ; Rackham Graduate School , 4th Floor Amphitheatre

When we step outside to contemplate the night sky, we often imagine ourselves isolated and adrift in a vast cavern of empty space—but is it so? Modern physics views the universe as more full than empty. Over the past century, this unfamiliar idea has emerged from a surprising partnership of exotic concepts: quantum physics and Einstein’s relativity. In this talk I’ll illustrate how this partnership provides the foundation for every aspect of human experience, including the existence of subatomic particles (and the effect of the so-called “Higgs field”), the peaceful nature of our journey through the cosmos, and the solidity of the ground beneath our feet.

POSTED BY Matt Strassler

ON December 2, 2024

Speaking at Brown University Nov 18th

Just a brief note, in a very busy period, to alert those in the Providence, RI area that I’ll be giving a colloquium talk at the Brown University Physics Department on Monday November 18th at 4pm. Such talks are open to the public, but are geared toward people who’ve had at least one full year of physics somewhere in their education. The title is “Exploring The Foundations of our Quantum Cosmos”. Here’s a summary of what I intend to talk about:

The discovery of the Higgs boson in 2012 marked a major milestone in our understanding of the universe, and a watershed for particle physics as a discipline. What’s known about particles and fields now forms a nearly complete short story, an astonishing, counterintuitive tale of relativity and quantum physics. But it sits within a larger narrative that is riddled with unanswered questions, suggesting numerous avenues of future research into the nature of spacetime and its many fields. I’ll discuss both the science and the challenges of accurately conveying its lessons to other scientists, to students, and to the wider public.

POSTED BY Matt Strassler

ON November 15, 2024

Video: A Public Lecture About “Waves in an Impossible Sea”

If you’re curious to know what my book is about and why it’s called “Waves in an Impossible Sea”, then watching this video is currently the quickest and most direct way to find out from me personally. It’s a public talk that I gave to a general audience at Harvard, part of the Harvard Bookstore science book series.

My intent in writing the book was to illuminate central aspects of the cosmos — and of how we humans fit into it — that are often glossed over by scientists and science writers, at least in the books and videos I’ve come across. So if you watch the lecture, I think there’s a good chance that you’ll learn something about the world that you didn’t know, perhaps about the empty space that forms the fabric of the universe, or perhaps about what “quantum” in “quantum physics” really means and why it matters so much to you and me.

The video contains 35 minutes of me presenting, plus some Q&A at the end. Feel free to ask questions of your own in the comments below, or on my book-questions page; I’ll do my best to answer them.

POSTED BY Matt Strassler

ON November 4, 2024

Why is the Speed of Light So Fast? (Part 2)

This is my second post on the subject of why “the speed of light (in empty space)”, more accurately referred to as “the cosmic speed limit”, is so fast. This speed, denoted c, is about 186,000 miles (300,000 km) per second, which does indeed seem quick.

But as I pointed out in my first post on this subject, this isn’t really the right question, because it implicitly views humans as centrally important and asks why the cosmos as strange. That’s backward. We should instead ask why we ourselves are so slow. Not only does this honor the cosmos properly, making it clear that it is humans that are the oddballs here, this way of asking the question leads us to the answer.

And the answer is this: ordinary atomic material, from which we are made, is fragile. If a living creature were to move (relative to the objects around it) at speeds anywhere close to c, it couldn’t possibly survive its first slip and fall, or its first absent-minded collision with a door frame.

Today I’ll use a principled argument, founded on basic particle physics and its implications for atomic physics, to show that any living creature made from atoms will inevitably view the cosmic speed limit as extremely fast compared to the speeds that it ordinarily experiences.

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POSTED BY Matt Strassler

ON October 3, 2024

An Answer to a Question from a Reader: About Forces

Every now and then, I get a question from a reader that I suspect many other readers share. When possible, I try to reply to such questions here, so that the answer can be widely read.

Here’s the question for today:

I do have one question that I couldn’t find the answer to in your book. Maybe I missed it, but here it is:

You explained what the strong force does (encapsulate the quarks and gluons within the proton), but what is the source of the strong force’s agency? I know it has energy used to hold the protons and neutrons together, but where does that force originate? It seems counter-intuitive, given the electromagnetic forces that pull particles apart due to equal charges — but how and why did the strong force come about? — Jeff Cox

Below I give a qualitative answer, and then go on to present a few more details. Let me know in the comments if this didn’t satisfactorily address the question!

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POSTED BY Matt Strassler

ON July 25, 2024

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Tag: quantum field theory

POSTED BY Matt Strassler

POSTED BY Matt Strassler

POSTED BY Matt Strassler

POSTED BY Matt Strassler

The Asymmetry Between Location and Motion

POSTED BY Matt Strassler

The Quantum Cosmos and Our Place Within It

POSTED BY Matt Strassler

POSTED BY Matt Strassler

POSTED BY Matt Strassler

POSTED BY Matt Strassler

POSTED BY Matt Strassler

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