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Matt Strassler

@mattstrassler.bsky.social

1.5K followers 121 following 222 posts

Theoretical physicist (particle physics, string theory, black holes), semi-retired professor, writer (author of the popular science book "Waves in an Impossible Sea"), amateur musician, and activist for founding public policy on facts and logic

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Reposted by Matt Strassler

Daniel Whiteson @danielwhiteson.bsky.social · 13/11/2025

Are you in Boston next week and want to hear two serious physicists have a conversation about aliens? I will discuss whether aliens speak physics with @mattstrassler.bsky.social on Nov 17 at the Harvard Bookstore. @harvardbookstore.bsky.social

Matt Strassler @mattstrassler.bsky.social · 14/11/2025

At the Harvard Bookstore (the independent bookshop in Harvard Square) at 7pm on Monday November 17th: Professor Whiteson will be talking about his whimsical-yet-serious book and answering tough questions from me and from you. profmattstrassler.com/2025/11/14/e...

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Event with Prof. Daniel Whiteson on Monday November 17 at 7pm

Monday, November 17th at 7pm, I'll be at Harvard Bookstore with particle physicist and author Daniel Whiteson, co-author of "Do Aliens Speak Physics?"

Matt Strassler @mattstrassler.bsky.social · 14/04/2025

⚛️🧪Is Superposition Really an "OR"? If a quantum system is in a superposition state "A+B", does it mean that "A AND B" are true, or that "A OR B " is true, or something else? An example of why ordinary language is not easily applied to #quantum physics. profmattstrassler.com/2025/04/14/i...

profmattstrassler.com

Is Superposition Really an "OR"?

If a quantum system is in a superposition state "A+B", does it mean that "A AND B" are true, or that "A OR B " is true, or something else?

Matt Strassler @mattstrassler.bsky.social · 03/04/2025

I understand your concern, but the phraseology is careful & correct. The 2 particles (distinguishable, like an electron and a positron) have positions & momenta that are still measurable separately, and thus measurement results for each of the entangled particles can separately be obtained.

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Matt Strassler @mattstrassler.bsky.social · 03/04/2025

⚛️🧪In the #quantum double slit experiment, the famous #interference pattern disappears if we measure which slit the particle went through. Why does it disappear? It's often described in vague, mystical terms, but in fact it's conceptually straightforward: profmattstrassler.com/2025/04/03/d...

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Double Slit: Why Measurement Destroys the Interference Pattern

Measurement eliminates the interference pattern in the quantum double slit experiment. This fact, despite its reputation, is conceptually straightforward.

Matt Strassler @mattstrassler.bsky.social · 31/03/2025

⚛️The interference of water waves happens somewhere -- wherever the waves are, obviously. But #quantum interference happens... nowhere. If you try to say exactly where two #entangled particles interfere, you will find yourself lost in space. profmattstrassler.com/2025/03/31/q...

Matt Strassler @mattstrassler.bsky.social · 31/03/2025

⚛️🧪If particles are #entangled, observing #quantum interference effects can be subtle, often requiring measuring multiple particles. As a result, quantum interference cannot generally be located in a specific place, unlike interference of e.g. water waves. profmattstrassler.com/2025/03/31/q...

Matt Strassler @mattstrassler.bsky.social · 28/03/2025

⚛️🧪In the #quantum double-slit experiment, it's natural to ask, "where does the interference occur?" But it's a dicey question: an answer is only possible in special situations, as when the particles are independent (i.e. their behavior is "uncorrelated".) profmattstrassler.com/2025/03/28/q...

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Quantum Interference 4: Independence and Correlation

It's a natural question: "where does quantum interference occur?" But it rarely has an answer, unless e.g. 2 particles are truly independent (uncorrelated.)

Matt Strassler @mattstrassler.bsky.social · 26/03/2025

⚛️🧪The #quantum double-slit experiment shows an interference pattern; but what is interfering with what? Today I explore examples that show how seemingly minor changes can eliminate interference, and why locating the interference in space is ... problematic. profmattstrassler.com/2025/03/26/q...

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Quantum Interference 3: What Is Interfering?

What interferes with what in the quantum double-slit experiment? Minor changes can eliminate interference, & locating the interference in space is misguided

Reposted by Matt Strassler

Brian Cook @2ndadminstate.bsky.social · 20/03/2025

"Nobody really knows what the elementary laws of nature are like yet; there are still too many unknowns." Still, @mattstrassler.bsky.social's astounding book Waves in an Impossible Sea is for me a refuge from the constant barrage of chaos and danger surrounding us right now.

Matt Strassler @mattstrassler.bsky.social · 20/03/2025

⚛️🧪Here are 10 examples of simple one- or two-particle systems in #quantum superpositions. Some show quantum interference (like double-slit), others don't. Do you see the pattern that distinguishes the two groups? Why & when does interference happen (...or not)? profmattstrassler.com/2025/03/20/q...

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Quantum Interference 2: When Does It Happen?

Here are 9 examples of simple 2-particle systems in quantum superpositions, some with interference, some without. What pattern distinguishes the 2 sets?

Matt Strassler @mattstrassler.bsky.social · 19/03/2025

⚛️🧪In yesterday's post, I showed a simple example where one particle can give the same #quantum interference as in the double-slit experiment. Then I posed a puzzle about two particles, which has generated a debate in the comments. Can you solve the riddle? profmattstrassler.com/blog/

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Of Particular Significance

Conversations About Science with Theoretical Physicist Matt Strassler

Matt Strassler @mattstrassler.bsky.social · 18/03/2025

⚛️🧪A super-simple example of #quantum #interference, in which an interference pattern emerges #particle by particle (as in the double slit expt). It frames a question clearly: is the particle interfering with itself, or is it not? Answer to follow. profmattstrassler.com/2025/03/18/q...

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Quantum Interference 1: A Simple Example

An example of quantum interference so simple that important questions about the origin of the interference can be investigated explicitly.

Matt Strassler @mattstrassler.bsky.social · 17/03/2025

⚛️🧪I've been interviewed on the Blackbird #Physics YouTube channel by UMich. grad student & LHC physicist Ibrahim Chahrour. The interview, aimed largely at physics undergrad & grad students, covers mass, fields, #particles & the #Higgs boson. www.youtube.com/watch?v=ly15...

How the Higgs ACTUALLY gives particles Mass - Matt Strassler | Blackbirdphys #3

YouTube video by blackbirdphys

Matt Strassler @mattstrassler.bsky.social · 16/03/2025

:-) Many truphs come from the mouths of the young...!

Matt Strassler @mattstrassler.bsky.social · 14/03/2025

Nicely done.

Reposted by Matt Strassler

Drew Olbrich @drewolbrich.bsky.social · 14/03/2025

I was curious about this so I corrected the scale.

Matt Strassler @mattstrassler.bsky.social · 14/03/2025

🔭 The eclipsed Moon from Earth, and the eclipsing Earth from the Moon spaceweathergallery2.com/indiv_upload...

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Blue Ghost And Earth Comparison Of The Total Solar Eclipse

Matt Strassler @mattstrassler.bsky.social · 14/03/2025

Me too. That's why I became a physicist. Some things I now understand. Some... nobody does.

Matt Strassler @mattstrassler.bsky.social · 13/03/2025

⚛️🧪To make sense of the #quantum double slit experiment, one must first learn this strange lesson: in 1920s quantum physics, the interference arises *neither* from particles moving through both slits *nor* from a wave function moving through both slits. profmattstrassler.com/2025/03/13/d...

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Did the Particle Go Through the Two Slits, or Did the Wave Function?

In the quantum double-slit experiment, did the particle go through the slits or did the wave function? 1920's quantum physics has a simple answer: "NO".

Reposted by Matt Strassler

Manu 🌊🐋 @manelcamacho.bsky.social · 27/02/2025

This is another one that is a "must read" to entertain myself this gloomy/cloudy afternoon... ❤️

Matt Strassler @mattstrassler.bsky.social · 10/03/2025

⚛️🧪Do wave functions describing #quantum objects actually "collapse" (i.e., suddenly change shape and lose pieces) when those objects are measured? Here's how to think about the issue clearly, without getting mired in illogical conundrums and bad arguments profmattstrassler.com/2025/03/10/d...

profmattstrassler.com

Do Quantum Wave Functions Collapse?

Do wave functions "collapse" when the objects they describe are measured? Here's how to think about the issue clearly while avoiding illogical arguments

Matt Strassler @mattstrassler.bsky.social · 06/03/2025

One step at a time --- we'll get to interference in a later post. Here a measurement is being made that makes such overlap and interference impossible. But even when such interference occurs, **the particle does not go in two directions at once.** That's a key point, to be shown soon.

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Matt Strassler @mattstrassler.bsky.social · 06/03/2025

⚛️🧪A #quantum superposition, in which a wave function contains 2 possibilities simultaneously, does not mean that both possibilities occur. It means that one *or* the other may occur; e.g. a quantum particle cannot be observed to go in 2 directions at once. profmattstrassler.com/2025/03/06/c...

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Can a Quantum Particle Move in Two Directions at Once?

A wave function superposition shows a quantum particle moving in either direction, but the particle itself can only be moving in one direction OR the other.

Matt Strassler @mattstrassler.bsky.social · 03/03/2025

*stationary* particles are standing waves in fields. Moving particles are traveling waves.

Matt Strassler @mattstrassler.bsky.social · 03/03/2025

#quantum #physics: In measurements of ultra-microscopic objects, the resulting measurement evidence is fragile & easily lost. How do experimental physicists preserve the evidence quickly, before it's too late? profmattstrassler.com/2025/03/03/m...

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Making a Measurement Permanent

Evidence in measurements of microscopic particles is fragile & easily lost. Experimental physicists must preserve it quickly, using amplification.

Matt Strassler @mattstrassler.bsky.social · 27/02/2025

⚛️🧪What is a measurement? A tricky question, especially in our #quantum world. As a first step, here's a way to think about it: a sketch of a simple measurement device in a simple quantum setting, one that we can use in future in more complex situations. profmattstrassler.com/2025/02/27/w...

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What Is a Measurement?

A measurement requires a device with some important properties that I describe. I then focus on a simple intuitive quantum measurement device

Matt Strassler @mattstrassler.bsky.social · 26/02/2025

Hard for me to answer these questions: they are more general questions about your own thinking than about physics itself, and I'd have to be an expert in your approach to answer them. If you have precise questions about physics, I can answer those.

Matt Strassler @mattstrassler.bsky.social · 26/02/2025

Sure, but I can't guarantee answers; it depends on the nature of the question as to whether a quick answer or clear answer is readily available.

Matt Strassler @mattstrassler.bsky.social · 26/02/2025

⚛️🧪A grasp of the "space of possibilities" [a.k.a. "configuration space"], and how to convert from it to the physical space we live in, is crucial in #physics, especially #quantum physics. I've added an article to help readers develop more intuition for it. profmattstrassler.com/articles-and...

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Understanding the Space of Possibilities: An Example

To understand quantum physics, one must first understand the space of possibilities. Simple illustrative examples are covered here.

Matt Strassler @mattstrassler.bsky.social · 26/02/2025

I'm not wedded to "wavicle" either --- but I used it because it has a history going back to 1927, and others of my colleagues have used it too. If someone wants to propose something else, go ahead... but it needs to capture the way in which these objects are indivisible yet wave-like.

Matt Strassler @mattstrassler.bsky.social · 25/02/2025

⚛️🧪#Wave functions in #quantum field theory are hard to visualize, & thus hard to understand. Today I address that problem, partially depicting the wave function for a field's vacuum state (no "particles") & comparing it to that of a state with 1 "particle". profmattstrassler.com/2025/02/25/t...

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The Particle and the "Particle" (Part 2)

I depict and explain the wave function for quantum field theory, for both the vacuum state (with zero particles) and for a state with one particle in it.

Matt Strassler @mattstrassler.bsky.social · 24/02/2025

⚛️🧪A #particle in 1920s #quantum #physics is a different beast from a "particle" in modern quantum field theory. This important distinction is inherently confusing. My aim this week is to bring a new level of pedagogical clarity to this tricky issue. profmattstrassler.com/2025/02/24/t...

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The Particle and the "Particle" (Part 1)

A particle in 1920s quantum physics is a different beast from a "particle" in modern quantum field theory. I use novel methods to explain this tricky issue

Matt Strassler @mattstrassler.bsky.social · 22/02/2025

Sounds right. It's something you can make in many theories of waves, not specifically limited to those of quantum physics. But while it is very useful, and I use it a lot, people often overstate its importance; it's more convenient than profound.

Matt Strassler @mattstrassler.bsky.social · 21/02/2025

⚛️🧪From this example one can see (even more so in the 2-dimensional versions) that in 1920s quantum physics the double-slit interference pattern arises from interfering *possibilities*. [But caution: quantum field theory changes the perspective!] profmattstrassler.com/2025/02/20/c...

profmattstrassler.com

Can You Interpret This Quantum Wave Function?

A challenge for readers: here's a wave function evolving over time, as I described in a post earlier this week. Can you interpret what is happening here?

Matt Strassler @mattstrassler.bsky.social · 21/02/2025

No, wavicles arise in quantum field theory, whereas here we are still doing 1920's quantum physics. The distinction is one I will explain carefully soon, but we have to walk before we can run.

Matt Strassler @mattstrassler.bsky.social · 21/02/2025

Yes, sort of... but for various reasons I think "two wave packets passing through each other" is not good phraseology. It suggests they are passing through each other in physical space, whereas in fact they are passing through each other in the abstract space of possibilities. This matters a lot!

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Matt Strassler @mattstrassler.bsky.social · 21/02/2025

⚛️🧪Yesterday I posted an animation of a #quantum wave function & asked readers to try to interpret it. Most people thought it shows 2 particles passing/colliding. In fact it shows just one particle in the midst of a disguised double-slit experiment! profmattstrassler.com/2025/02/21/i...

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It was the Double Slit Experiment All Along!

The animation of a quantum wave function that I posted yesterday shows one particle, not two, and is closely related to the double slit experiment.

Matt Strassler @mattstrassler.bsky.social · 21/02/2025

In a sense. I've added an explanation now to the original post, so you can read that and see if it agrees with how you were thinking.

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Matt Strassler @mattstrassler.bsky.social · 21/02/2025

Right now we're just trying to understand how it works, not to decide what it "is".

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Matt Strassler @mattstrassler.bsky.social · 21/02/2025

Nope...

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Matt Strassler @mattstrassler.bsky.social · 21/02/2025

"They"? It's not two particles; it's one.

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Matt Strassler @mattstrassler.bsky.social · 20/02/2025

⚛️Most people -- even #physics students -- mistakenly think this #quantum wave function shows two #particles approaching each other and interfering with one another. But no. What, in fact, is it?

Matt Strassler @mattstrassler.bsky.social · 20/02/2025

⚛️🧪A brain teaser for blog readers: here's an interesting #quantum #wave function evolving over time, shown 3 ways. Can you interpret what this wave function describes? Note the interference effects... what do they represent? Answers tomorrow. profmattstrassler.com/2025/02/20/c...

profmattstrassler.com

Can You Interpret This Quantum Wave Function?

A challenge for readers: here's a wave function evolving over time, as I described in a post earlier this week. Can you interpret what is happening here?

Matt Strassler @mattstrassler.bsky.social · 19/02/2025

⚛️🧪What is a wave function in #quantum #physics? It's not a thing; it sits outside the physical system it describes. Its origin dates to the 1830s, not the 1920s; the word "#wave" in its name often isn't appropriate; and one needn't even use it. profmattstrassler.com/2025/02/19/s...

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More On Wave Functions: Simple and Complex

What is Schroedinger's quantum wave function for, in what sense does it wave, and what's the wider context for it across physics?

Matt Strassler @mattstrassler.bsky.social · 18/02/2025

⚛️🧪Actor & science communication expert Alan Alda has a #podcast "Clear & Vivid" which often covers topics in #science and science communication. I was delighted to be on the podcast; our conversation about waves of the cosmos & my recent book is now posted clear-vivid-with-alan-alda.simplecast.com

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Clear+Vivid with Alan Alda

Learn to connect better with others in every area of your life. Immerse yourself in spirited conversations with people who know how hard it is, and yet how good it feels, to really connect with other ...

Matt Strassler @mattstrassler.bsky.social · 18/02/2025

Sometimes bluesky scrambles the thread enough that I get lost. But it is true, I am always working very hard and only get on to social media occasionally.

Matt Strassler @mattstrassler.bsky.social · 18/02/2025

Yes, things are normalized for clarity, since only the shape matters here.

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Matt Strassler @mattstrassler.bsky.social · 17/02/2025

Tomorrow is PODCAST DAY! Alan Alda speaks with with @mattstrassler.bsky.social . What Are You Made Of? The answer, regrettably, is unbelievable... Available tomorrow 👉 bit.ly/3Q0rUMV After production costs, all proceeds of #ClearAndVivid go to @AldaCenter . 🗣️💙

Clear+Vivid with Alan Alda

Learn to connect better with others in every area of your life. Immerse yourself in spirited conversations with people who know how hard it is, and yet how good it feels, to really connect with other ...

Matt Strassler @mattstrassler.bsky.social · 17/02/2025

If 1st/2nd year university math is no problem for you, you can also read this set of articles (which themselves depend on my set on fields and particles, relevant links are found within) profmattstrassler.com/articles-and...

profmattstrassler.com

How the Higgs Field Works (with math)

This set of articles explains how the Higgs field gives mass to other particles, and some details about the Higgs particle. These articles require the kind of math that you’d come across in a…