Matt Strassler

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

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?"

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...

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?

⚛️🧪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...

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.

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.

⚛️🧪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...

⚛️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...

⚛️🧪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...

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.)

⚛️🧪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...

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

⚛️🧪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...

"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.

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?

⚛️🧪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...

Of Particular Significance Conversations About Science with Theoretical Physicist Matt Strassler

⚛️🧪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/

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.

⚛️🧪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...

YouTube video by blackbirdphys How the Higgs ACTUALLY gives particles Mass - Matt Strassler | Blackbirdphys #3

⚛️🧪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...

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

Nicely done.

I was curious about this so I corrected the scale.

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

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

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".

⚛️🧪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...

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

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

⚛️🧪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...

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.

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.

⚛️🧪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...

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

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

#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...

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

⚛️🧪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...

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.

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.

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.

⚛️🧪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...