Questions About the Multiverse

The August issue of Scientific American has the multiverse on the cover, with a skeptical feature article on the topic by George F. R. Ellis, Does the Multiverse Really Exist?, which argues that heavily promoted multiverse research isn’t really testable and can’t explain much of anything. Vilenkin and Tegmark respond with The Case for Parallel Universes.

I just took a look at some of the earliest postings on this blog about the multiverse from as far back as seven years ago (e.g. here and here). Things haven’t changed at all. One might be tempted to criticize Scientific American for keeping this alive, but they just reflect the fact that this pseudo-science continues to have significant influence at the highest levels of the physics establishment. The Perimeter Institute recently ran a conference on Challenges for Early Universe Cosmology, which was dominated by multiverse mania. Unlike the case at SciAm, multiverse skepticism didn’t get prominent play at Perimeter.

Update: For those of you who just can’t get enough multiverse, the Sci-Fi film Another Earth opens Friday. Click on “Parallel Worlds” for an explanation of “the theoretical physics behind the film.”

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29 Responses to Questions About the Multiverse

  1. Brilliant article by Max Tegmark. I’m not a physicist, but I find his arguments compelling and perfectly rational. What about Tegmark’s arguments do people here object to?

    My only disagreement with Tegmark is his last statement: “The price we have to pay is becoming more humble—which will probably do us good—but in return we may find ourselves inhabiting a reality grander than our ancestors dreamed of in their wildest dreams.” Actually, if science continues to humble us in this manner, I fear we may do what Lovecraft warned about in the face of our mind-boggling cosmic insignificance, and “flee from the light into the peace and safety of a new dark age.”

  2. Peter Woit says:

    Sean the Mystic,

    Unlike mysticism, where there may be other ways to convince people you have interesting insight into something, in science there’s traditionally just one way to do this: use your insight to make a convincing testable prediction and then check it. This is what neither Vilenkin nor Tegmark can do, and they’ve made no progress towards doing this in the years and years that they have now spent promoting multiverse studies.

    There may very well be a multiverse, of levels I, II, III, IV or whatever. But at this point all the years of work on this have led to nothing but:

    1. claims that if everything worked out just right, there’d be a signal visible in the CMB, of exactly the right size to now be just beyond the level detectable. This appears to be just wishful thinking, and even Tegmark says he doesn’t believe it:
    “I totally share his skepticism to these claims.”

    2. claims that string theory will allow statistical predictions by analyzing the landscape of string theory solutions. This has been a complete failure and there are strong arguments that it is guaranteed to fail.

    As for the argument that skepticism about multiverse studies is some sort of hubris, I think the opposite is true: the hubris of multiverse maniacs with their conviction that we don’t need conventional standards of science any more and can happily go on about level IV multiverses is just staggering.

  3. Thank you for this reply. Maybe there should be a new field of study then, call it “multiverse studies” or something, so these multiversalists can pursue their ideas separately from the more traditional empirical scientists? Maybe these theories are more pure math or even art than science, but that doesn’t mean they aren’t worth exploring.

  4. Peter Woit says:


    The burgeoning field of “Multiverse Studies” definitely isn’t pure math. The papers in this subject typically just use high school algebra. Categorizing the subject as an art form and not a science would be a step forward.

  5. Hakeem Shabazz says:

    Let them do all the multiverse studies they want, on their own nickel.
    Just cut off uncle sam’s gravy, although that may thin out the crowd milking a nice conference.

    BTW, is this not a corollary, in headline form, of the theory of the infinite mutiverse, where anything consistent with physical laws will happen:
    President Obama and Palin Have Love Child in Alternative Universe.
    ‘He cheated with that racist dingbat’, sobs Michelle.

  6. Peter Woit says:


    There’s very little of Uncle Sam’s money in multiverse studies, since NSF and DOE panels tend to not support this. Private money (Templeton Foundation for Tegmark’s FQXI, Blackberry for Perimeter) is funding most multiverse mania.

    And, by the way, multiverse jokes have also gotten really old by now…

  7. So is that what this is about? A power struggle for government funds? I suppose you could argue that if the public finds multiverse studies more interesting than experimental particle physics, and wants to spend their tax money on it, then that’s their perogative. My impression is that we’re fully in the postmodern era now, so the pursuit of objective truth for its own sake no longer carries much weight. Multiverse studies fits perfectly with postmodern thinking, whereas traditional physics just seems like intellectual tyranny. These are just the random thoughts of a mystic who used to study physics, feel free to ignore them 😉

  8. Eric habegger says:


    “My impression is that we’re fully in the postmodern era now, so the pursuit of objective truth for its own sake no longer carries much weight. Multiverse studies fits perfectly with postmodern thinking, whereas traditional physics just seems like intellectual tyranny.”

    I think you are being too kind by half by describing the current mood as post-modern. If this new era continues as it has been in physics for the last thirty years and isn’t just a temporary blip I think it would be better called the second dark age. Or better yet, in the spirit of the times we should now call the dark ages the first post modern era. That would then make everyone feel better about the second post modern era we may be entering. Anyone interested in eye of newt to put into your latest physics experiment? I have them at rock bottom prices.

  9. Markus Schwarz says:

    Dear Sean,

    this “traditional intellectual tyranny” has brought to you such things as electricity, cell phones, GPS systems… In chemistry it led to things like plastics, and in medicine to antibiotics… The list is still growing. If your multiverse/postmodern thinking could produce things like warpdrives or teleporters, or even improve known technologies, I am sure it would have a justified place in natural science. However, they have not contributed anything so far, and my impression is that they don’t even try. Instead, they invent new rules and still want to be part of the natural sciences. To me, they sound like soccer players who pick up the ball by punching other players and, when the referee shows them the red penalty card, argue that this is allowed in rugby. If someone wants to pursue these ideas, he should indeed do so in the humanities department. But why should I abandon the successful traditional way of thinking?

  10. Bobito the Payaso says:

    “more traditional empirical scientists”

    This made me laugh. And cry.

  11. Ignatz Thugg says:

    Perhaps Alan Sokal can revise his first book (Fashionable Nonsense)
    by replacing the literary post modernists by the mystics and new-agers
    within the Physics community. Not much would have to be changed –
    appropriate quotations of course, but Sokal’s commentary could
    (almost) be left intact.

  12. Aleksandar Mikovic says:

    “If someone wants to pursue these ideas, he should indeed do so in the humanities department. But why should I abandon the successful traditional way of thinking?”

    The reason why many physicist are working on the multiverse ideas is that any attempt to extend the current fundamental physical theory, i.e. the Standard Model of particle physics and cosmology, without an experimental input, boils down to the problem of formulating a mathematical theory with certain properties. The main property is to recover the Standard Model in a certain limit, and the other requirements are based on the authors philosophical inclinations. Hence this type of research cannot be done in the humanities departments, since the people there do not know enough physics and math to do it or to evaluate it. Although this type of research is not a traditional science, I think that it is useful, if it is done in an adequate proportion to the usual science research, since it opens new vistas and provides new ideas. There are several episodes in the history of science when such an approach was fruitful, for example: General Relativity and Dirac’s equation.

  13. Alexander Kruel says:

    Have you ever heard about Eliezer Yudkowsky and his take on the multiverse? I am curious about your opinion:

  14. Igor Khavkine says:

    Alexander, this is a case of one word with multiple distinct meanings. The ‘multiverse’ discussed on Yudkowsky’s blog is logically distinct from the notion of ‘multiverse’ discussed in the recent SciAm issue. The former consists of a certain way of looking at a mathematically precise, empirically well tested theory of quantum mechanics, while the latter consists of a loosely grouped collection of speculative ideas about how to explain some features of our universe, though without any empirical way of separating good ideas from bad ones.

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  16. Markus, who wants you to abandon a successful way of thinking? I just suggested a new field of study, so the different camps don’t have to fight each other. I think it would be great if multiversalists joined artists, writers, mystics and other creative people who like to speculate about possible worlds. Maybe it would all be nonsense, but it would be a lot of fun and they might even discover something “important”. I just find it fascinating that creatives had ideas about parallel universes a long time ago that sound very similar to what physicists are saying now. (See for some examples).

    I think you’re on a slippery slope if your justification for science is its practical applications; we might as well abolish many areas of higher math, stop building space telescopes and forget about astronomy and cosmology with that attitude. For that matter, what is the practical value of the LHC? I like to think that anything the human mind can imagine is real in a larger multiverse of ideas, and that exploring that realm is a form of empirical science — but then, I am a bit of a crackpot. 🙂

  17. Bob Levine says:

    Sean, I think you’ve missed the point of Markus’s post. If I read him right, he was pointing out a substantial number of technological developments that count as existence proofs of a particular connection between science and something normally labeled ‘reality’ that corresponds to how the world works, and was suggesting that the multiverse has no such evidence to favor it. The old question, ‘If it were wrong, how would we know?’ is relevant here. If the multiverse, on your or anyone else’s conception were wrong, how would we know. Markus’ and Peter’s point, and that of a lot of the other contributors to this site, is that hype notwithstanding, there isn’t any way we would know. So whether you enjoy ‘exploring’ the multiverse or not, it’s unconnected to science, period.

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  19. Christian Takacs says:

    Dear Sean,
    Perhaps you need to reassess your definitions of science… Like I did. When I was growing up I read a great deal of Science Fiction and watched Star Trek, Babylon 5, and other Sci-Fi oriented programming. I read The Time Machine, Permutation City, The Broken God, and many other fine books. When I started in great excitement to look into how such things as Warp Drive, Time Travel, Alternate Universe Travel, Teleportation might work, what I discovered was that there was not so much “science” as “plot devices” at work. I began to realize that my love of good fictional stories with technological plot devices was clouding my understanding of what science actually was. While there is truth to be found in fiction, it is usually in the form/message of good and bad human choices and consequences, and not how scientifically accurate or valid the plot devices are. When you read an Aesop Fable like The Fox and the Crow, or The Tortoise and the Hare, you aren’t supposed to take away that animals talk, have foot races, or are genetically predesposed to have philosophical discussions, Or that they actually exist in an alternate universe; You ARE supposed to consider the concepts and implications behind the character’s actions, masks, and words.

    When you study Science/ and or Physics, you are going after “what is it and how does it work?” and to do this you follow very strict rules of definition, methodology, heirarchy, logic and confirmational experimentation. These “rules” are not to be mistaken for “plot devices” and vice versa. These “rules of science” are also designed to be resistant (not fool proof) to sophistry and deceitful manipulation.
    As a good general rule, when anyone claiming to be doing science/physics avoids or denies “confirmational experimentation” they should be met with a healthy dose of skepticism, then slapped with a ruler on both palms before being made to write “I shall not evade confirmational experimentation while in THIS particular universe” on a white board for as many times as there are theoretical unproven multiverses, or until they repent, or just renounce all their government funding and start quacking like a duck.

  20. Paul D. says:

    And, by the way, multiverse jokes have also gotten really old by now…

    I’m sure there are universes where the jokes are still funny.

    Just … not this one.

  21. lun says:

    As a general point, this discussion has been going in circular form in many places, physical and virtual. I think the question is very simple:
    Can the multiverse make experimentally verifiable predictions?
    Since there have been at least two proposals in the affirmative ((a) cosmological signals of neighbouring universes and (b) correlations among physical constants), dismissing the multiverse idea as unscientific a priori is wrong.

    ON THE OTHER HAND, claiming that the multiverse must exist because string theory “must be right” but no other solutions exist for problems like the cosmological constant and vacuum selection is also wrong. I believe I can not explain why.

    What gets me about modern string theory is not so much that they do research on the multiverse, as I said to me its a potentially legitimate and productive area of investigation. Its that SOME string theorists make claims of results (“we know string theory is the theory of everything!” “We know the multiverse is predictive”) well before results are on the horizon (indeed, well before the results will be on the horizon).

    The fault here is not with string theorists, ALL fields of science, today, make wildly overhyped claims because so much of their funding depends on their PR ability.
    In the long-term, this corrupts the science. Feynman explained this in much better than I can here.
    String theory, because of the fuzziness of its fundamental picture and the
    lack of experimental verification, is more susceptible to this corruption than other fields, thats all.

    It is not just with the multiverse: I saw a seminar where an eminent AdS/Condensed matter person and his collegues had a near-shouting match with AdS/condensed matter skeptics on whether AdS/CFT has anything to say about condensed matter.
    And the crucial question, “is there a way to tell that a certain system can be described by a classical supergravity dual”, was not even addressed!
    It is a question which we could answer for some systems. For QCD, for example, it probably is no because of asymptotic freedom and the fact that the number of colors is about the same as the number of flavors.

    Which brings me to the second problem of modern science to which string theory is susceptible: the fact that young people have to publish on very short time-scales.
    Both the multiverse and AdS/whatever provide a good way to publish many papers in a short-time, so they are “popular”, even if everyone knows these ideas are probably profounds flawed. Again, this is not because string theory is particularly evil, its just the economics of modern research.

  22. lun says:

    ps: Igor, there have been attempts to unify the two pictures by string theorists:

  23. Condensed Matter Theorist says:

    To all the non-physicist readers out there I would like to point out one thing regarding the potential demise of physics or the burgeoning second dark-age being discussed in the comments. The largest swath of physicists in the American Physical Society are categorized as condensed matter physicists. Virtually EVERY cmt physicist I know thinks the multiverse business is completely without merit and ridiculous. Further, almost all cmt physicists I know also think that string theory is complete pseudo-science and likely to be looked at as the greatest hoax ever played on physics.

    Just wanted to assure people that MOST physicists are stuck solidly to the scientific method where theorists are only taken seriously if they make testable predictions and nothing is considered to be close to reality until it is experimentally demonstrated beyond a reasonable doubt.

  24. Giotis says:

    Condensed Matter Theorist you are not qualified to reject HEP/QG theories using such dismissive language. Have you ever studied String theory in depth?

    In my mind your opinion about String theory or the Multiverse has the same weight as the opinion of a TAXI driver.

    Be modest and don’t make pompous statements for things you have no idea about.

  25. Condensed Matter Theorist says:

    Giotis, you’re joking, right? Taxi driver? Really? Even most taxi drivers are able to dismiss string theory due to it’s lack of adherence to the scientific method. Experimentally verifiable. It’s very simple. Taxi drivers….come on, who’s pompous?

    …I should have guessed I would get a “condensed matter theorists are intellectually inferior to string theorists” type response in the comments of this blog. Most theorists I know actually are quite knowledgeable about “HEP/QC” theories–as you call them–and astonishingly to you–still think they are ridiculous and choose to work on something else. I know it’s probably hard to believe but the complement of the set of all string theorists does not equal the set of all theorists too stupid to be string theorists. That may hurt your ego (and I understand that the ego is one of the only thing most string theorists have left) but it’s true.

  26. Condensed Matter Theorist says:

    Giotis, one more thing. You’ve set up such a standard that ONLY a world-renowned and string-theory-establishment-certified expert’s rejection of string theory would have any meaning for you. Any other rejection would necessarily come from someone who is “unqualified”. That’s very convenient for you. I suppose until Witten turns his back on string theory, how dare any other mere mortal to have a judgement. Although, I imagine that if Witten jumped ship, you all would convince yourselves that you threw him overboard due to his loosing his marbles and being no longer credible.

  27. Peter Woit says:


    CMT makes the obvious points about this, but in addition it’s worth pointing out that most multiverse papers use very little mathematics (and not that much physics). A bright (or even not so bright) high school student could read and follow some of them (as well as figure out why it wasn’t science…)

  28. gregor berkens says:

    Michael Faraday also used very little mathematics, and yet Einstein had a picture of the great Faraday hanging in his office.

    This blog also uses very little mathematics, so perhaps this blog isn’t really about physics. 🙂

  29. Thomas Curran says:

    The article ” Does the Multiverse Really Exiist” states astronomers are able to see to a distance of 42 billion light years……
    My question is what do they see past 13.7 billion light years?

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