By Sean Carroll | May 13, 2011 1:46 pm

It started with an innocent, and possibly joking, request on Twitter: “Can you explain M-theory?” Having previously been asked to defend the Many-Worlds Interpretation of quantum mechanics and various other topics, I didn’t take it very seriously.

But upon further reflection — why not? Obviously nobody is going to give a full and comprehensible account of any reasonably complex topic when limited to 140 characters, but it might be fun and even useful to try to distill the basic point of something down to its tweetable essence. Still, in a single tweet there is almost no chance to do much but introduce jargon, so I decided to allow myself three tweets. Here’s my go at summarizing M-theory. (Remember chronology is bottom-up.)

Obviously, there is more to be said, but I think some actual information is conveyed. Different people might choose different aspects of a subject to spend their precious three tweets on, but that’s part of the beauty. As someone pointed out, a poetic aspect results from subjecting yourself to such stringent limitations on what you can say.

And if it works for M-theory, what else? And thus a hashtag was born: #3tweets. Yesterday I took a stab at the Higgs boson.

This reminded me that quantum field theory is probably the single most under-popularized subject in all of fundamental physics. Particle physics, yes; string theory, sure; quantum mechanics, endlessly; but the structure of QFT itself is rarely explained in its own right. It’s worth at least a few tweets.

I certainly hope to try a few more examples. But — it’s everyone’s internet. Feel free to join in, with new topics or ones previously covered. I’m sure someone has a different take on quantum field theory than I do.

  • http://twistedphysics.typepad.com Jennifer Ouellette

    It’s like Twitter-verse haiku. With physics. :)

  • RayS

    Next theory to be explained: Why anything can be explained in 3 tweets.

  • Massaro

    OK, with M-theory and QFT done, all that’s missing is General Relativity, no? :)

  • http://Notes.kateva.org John Gordon

    Now I want blog posts or an article on QFT. I agree, way under popularized.

  • Anchor

    Subtweets for those who don’t understand what mysterious concepts or crypotographical jargon like (strong or weak) “coupling” and “b/c” means…

    The beginning of a horrible prospect: public education in bite-sized chunks of questionable nutritious value. Because a communications facility which may be perfectly suited to asking a simple question is utterly LOUSY at providing an answer.

    Unless one likes poetry more than understanding.

    After a short while one might as well admit the effort isn’t worth a tweet and get down to the serious business of writing decent articles or blog posts that actually convey the possibility of comprehension, instead of pretending to distill an “explanation” with twitterpated bullet-points…even if those in the know find them poetically lovely.

  • dilefante

    I have “From eternity…” waiting on the shelf, hoping to find the time to read it. Meanwhile, could you 3-tweet a summary?

  • http://mirror2image.wordpress.com Serge

    What I’s like to see:
    1. symmetry breaking in 3 tweets
    1. renormalization in 3 tweets

  • http://tristram.squarespace.com Tristram Brelstaff

    You’ve got the basis for a popular book there. (It could be even bigger than “Teach your Dog Quantum Physics”)

  • ChuckWhite

    3tweets … what an interesting idea … also seems like a concept anyone can use to clarify their thinking when confused or distracted … hee, not that that is why YOU used it.

  • Chris

    QFT: What you’ve done there is describe classical field theory (which I understand), and the exclusion principle/spin statistics (which I sort of understand). And completely skipped the quantum part or the many particle part, neither of which anyone has ever even sketched adequately.

  • Gordon

    Of course you could just tweet “42′ and dispense with all other tweets.

  • Kai Teorn


    sorry if you already wrote about it and I missed it, but what is your opinion on the recent attempts to derive all of physics from entropy and information (Verlinde, Jae-Weon Lee and many others)? Do they have a point or is this just jugglery with symbols?

  • James

    Alright, I have a twitter account and have used it for almost nothing, but I thought this worth a challenge, so I tried the AdS/CFT Correspondence (holographic or gauge/gravity duality) in three tweets. I thought it might be impossible before I tried it and now, having done it, I think… yep, still impossible. Anyone else care to have a go?


  • God

    Because that’s how things have worked for thousands of years.

    Why do we read from top to bottom?

  • http://www.qwertyous.blogspot.com/ John R Ramsden

    @Massaro (#3)

    Didn’t Prof John Wheeler summarize General Relativity in one tweet, before Twitter was even invented?

    “”Space tells matter how to move; matter tells space how to curve.”

  • Anders R

    I guess the caveat that “when the couplings are small” is what makes it possible to omitt the 10 times whatever number of other possible string vacuua.

  • Anders R

    And the problems with lack of posibility to experimentally falsify the hypothesis. Even if no Higgs boson and no supersymmetry is found there will still be string theories available to cover up for that situation. Through the work of people like Peter Woit among others there seem to be a gradual decline in respect for the subject however. One interesting example of this is the interview Brian Greene did on NPR in january. There was a distinct amount of scepticism in that interview that hasn’t really been part of the mainstream discussion on the subject until now. For a more interesting approach (that is immediately falsified if supersymmetry, extra dimension, a higgs boson or dark matter is foun) see for example Cristoph Schillers strand-theory.

  • Anders R

    Here you go Sean. read and weap:


  • http://people.maths.ox.ac.uk/daviesr/ Rhys

    ‘Weap’ is right…

    But more on topic: I *hate* the “moving through molasses” analogy. People aren’t going to understand the Higgs mechanism without studying some QFT, and the associated mathematics. Short of that, you might as well leave it at “the Higgs field gives mass to the W and Z bosons, and elementary fermions”.

  • Anders R

    They’re not going to find the Higgs so it’s alright.

  • James


    I agree about disliking the “molasses” analogy, but then see http://xkcd.com/895/. I don’t actually mind the “warped sheet” analogy for warped space, but it’s when people use to demonstrate gravitational attraction that it bugs me.

  • Missy

    LOL I think that was as much fun as seeing you speak at Griffith Observatory last year 😛

  • https://www.cfa.harvard.edu/~rkirshner/ Bob Kirshner

    Concision is not wisdom.

    As ever,


  • DPSinVenice

    This post reminds me of twitterature: eg,
    Pride and Prejudice: janeaustin: Woman meets man called Darcy who seems horrible. He turns out to be nice really. They get together.

  • Weisskid

    The Hubbell telescope detects light that was emitted by galaxies ~10 billion years ago. Where were these galaxies relative to ours when they emitted that light and why has it taken that long to get here?

  • http://www.astro.multivax.de:8000/helbig/helbig.html Phillip Helbig

    What is the simplest thing which cannot be explained in three tweets?


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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] cosmicvariance.com .


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