Belief in multiverse requires exceptional vision

Tom Siegfried at Science News has a new piece about how Belief in multiverse requires exceptional vision that starts off by accusing critics of multiverse mania of basically being ignoramuses who won’t accept the reality of anything they can’t see with their own eyes, like those in the past who didn’t believe in atoms, or superstrings:

If you can’t see it, it doesn’t exist. That’s an old philosophy, one that many scientists swallowed whole. But as Ziva David of NCIS would say, it’s total salami. After all, you can’t see bacteria and viruses, but they can still kill you.

Yet some scientists still invoke that philosophy to deny the scientific status of all sorts of interesting things. Like the theoretical supertiny loops of energy known as superstrings. Or the superhuge collection of parallel universes known as the multiverse.

It’s the same attitude that led some 19th century scientists and philosophers to deny the existence of atoms.

The problem with the multiverse of course is not that you can’t directly observe it, but that there’s no significant evidence of any kind for it: it’s functioning not as a testable scientific explanation, but as an excuse for the failure of ideas about unification via superstring theory. Siegfried makes this very clear, with his argument specifically aimed at those who deny the existence of “supertiny loops of energy known as superstrings”, putting such a denial in the same category as denying the existence of atoms. Those who deny the existence of superstrings don’t do so because they can’t see them, but because there’s no scientific evidence for them and no testable predictions that would provide any.

Siegfried has been part of the string theory hype industry for a long time now, and was very unhappy with my book, which he attacked in the New York Times (see here) as misguided and flat-out wrong for saying string theory made no predictions. According to him, back in 2006:

…string theory does make predictions — the existence of new supersymmetry particles, for instance, and extra dimensions of space beyond the familiar three of ordinary experience. These predictions are testable: evidence for both could be produced at the Large Hadron Collider, which is scheduled to begin operating next year near Geneva.

We now know how that turned out, but instead of LHC results causing Siegfried to become more skeptical, he’s doubling down, with superstring theory now accepted science and the multiverse its intellectual foundation.

The excuse for Siegfried’s piece is the Wilczek article about multiverses that I discussed here, where I emphasized only one part of what Wilczek had to say, the part with warnings. Siegfried ignores that part and based on Wilczek’s enthusiasm for some multiverse research takes him as a fellow multiverse maniac and his article as a club to beat those without the exceptional vision necessary to believe in superstrings and the multiverse. Besides David Gross, I’m not seeing a lot of prominent theorists standing up to this kind of nonsense, leaving those invested in failed superstring ideology with the road clear to turn fundamental physics into pseudo-science, helped along by writers like Siegfried.

Update: A commenter points to this from Wilczek, noting his lesser multiverse enthusiam than Siegfried’s.

Update: Ashutosh Jogalekar at The Curious Wavefunction has a similar reaction to the Siegfried piece.

Update: There’s an FQXI podcast up now (see here), with Wilczek discussing the multiverse.

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73 Responses to Belief in multiverse requires exceptional vision

  1. Peter Woit says:


    Thanks for the advice that I should run this blog more like Lubos’s witty and entertaining one that you so much enjoy. The great thing about the internet is that there’s a place for everyone. I think you’ve found your place and I’m sorry but I can’t allow you anymore to try and change this one.

    Others: please don’t feed the troll.

  2. Experimental Physicist says:

    Peter and Lucretius

    This is my first comment in any blog. I am SM experimentalist, I consider myself a layperson in BSM physics. Though I came to know about this blog very recently, I have read most of the earlier entries and comments. I read a lot of other blogs on different subjects too. The aspect of this blog I admire the most is the sensible comments from experts from different fields whether their arguments are either for or against Peter’s. For instance, though Peter Shor and Matt Strassler may have different opinions, their arguments are worth admiring equally. There are a lot of other regular commentators in this blog whose insights sometimes outweighs than that of the main enetry. Thanks Peter for creating such a wonderful platform. Lucrtius, to me, correct scientific insights are far more important than wits.

    Exp Physicist

  3. Peter Woit says:

    Thanks! I should say that among the most rewarding aspects of running this blog is learning new things from and hearing the point of view of some of the commenters here, well-known (not always visible from the name they leave..) and not-so-well-known. It’s not always easy though to try and keep this a place that sensible people would want to participate in…

  4. george ellis says:

    In his previous post at The Curious Wavefunction, Ashutosh Jogalekar (commenting on whether psychology is a science or not) gives the following criteria

    ” The five basic requirements for a field to be considered scientifically rigorous [are] clearly defined terminology, quantifiability, highly controlled experimental conditions, reproducibility and, finally, predictability and testability.”

    Sounds good to me.

  5. srp says:

    Don’t think you want to rule out the observational sciences–astronomy, meterology, oceanography, structural geology, etc.–because they can’t do experiments.

  6. Maynard Handley says:

    “Don’t think you want to rule out the observational sciences…”
    Oh give that old canard a rest. The cloud chamber was invented precisely to study the phenomena that result in clouds, and then repurposed by physics. The whole point of the diamond anvil is try to get at the actual conditions of matter inside the earth.
    And so on, and so on.

    If I’m an oceanographer, yes, I observe the existing ocean currents. But I ALSO hypothesize that they are driven by density differences caused by salinity and/or temperature. I do experiments to see how these effects play out. I make predictions about where the ocean water will be above average in salinity or whatever, and test the predictions. I fantasize about what might happen to currents if a mass of fresh water were to hit a particular ocean, and then look in the historical record for any possible such events. etc etc

    The issue is not experiments (something like a controlled environment run by the scientist), it is a feedback loop between observations and predictions. The observations can come from experiments, examining “nature”, or the historical record; likewise a variety of predictions are possible. What matters is both observation (to keep one tethered to reality) AND predictions (so that one is approaching some sort of understanding, doing more than just stamp collecting).

  7. huhiho says:

    The issue is not experiments (something like a controlled environment run by the scientist), it is a feedback loop between observations and predictions. The observations can come from experiments, examining “nature”, or the historical record; likewise a variety of predictions are possible. What matters is both observation (to keep one tethered to reality) AND predictions (so that one is approaching some sort of understanding, doing more than just stamp collecting).

  8. Neil says:

    The multiverse, along with the anthropic principle, in some sense “explains” fine tuning to me, and I like that. It is not traditional science, but it is not religion either. If, someday, fine tuning can be explained without these concepts, I will be happier.

  9. Lee Smolin says:


    Cosmological natural selection can explain the fine tunings of the parameters of the standard model of particle physics without the anthropic principle. And it makes falsifiable predictions, for example that the upper mass limit of neutrons stars is at most two solar masses. This is so far consistent with observations but could be falsified at any time. This doesn’t mean its right, but it means its a testable scientific hypothesis.



  10. Giotis says:

    Bottom line is that although other universes cannot be observed, even in principle, it may be indeed the case that there is a Multiverse out there. The thing is, are we clever enough to theoretically deduce its existence even if we can observe it?

    I think it is possible if we have a strong belief in the corresponding theoretical framework which predicts it. Besides pure theoretical considerations we may gain confidence on the validity of the corpus of theories supporting the multiverse idea by circumstantial experimental evidence.

    In any case the last thing we want to see is wasting decades of research trying to understand the values of parameters which indeed may have a pure environmental explanation. So the sooner we reach conclusions regarding the Multiverse idea the better. In that respect research should continue of course. Don’t forget that Nature is full of surprises and you never what you may found just around the corner; either a dead end or a revelation, the only way you could find it out is by walking the path…

  11. Armin Nikkhah Shirazi says:


    I am struck by how the first part of your third paragraph seems to contradict the second part. You seem to consider “trying to understand the values of parameters” at least potentially a waste of time but then say “the only way you could find out is by walking the path”. If this is correct then efforts to understand those values cannot be considered a waste of time as long as “walking the path” promises a resolution one way or another.
    I think the unspoken assumption behind this incongruence is that you already deem research around the multiverse to be more promising than other approaches (as evidenced by the second paragraph and prior posts).
    I think there is nothing inherently wrong with holding that assumption, the problems arise when it is used as a criterion for evaluating and comparing distinct approaches to solving a problem without making it explicit that it has been used that way. If you are not aware of this, it will make it that much more difficult to understand the point of view of those who do not share your assumptions.

  12. Nathalie says:

    Let us assume that there are billions and billions of universes out there. After all, we already know that there are billions and billions of galaxies. Can any of you explain why humans on our tiny little planet should care about the number of Universes? Don’t tell me that it’s because we want to understand our own universe better. Such an argument doesn’t make sense as our universe need not be a typical one. Of course, you could make further assumptions but who tells you that your assumptions are correct?

  13. Low Math, Meekly Interacting says:

    I’m also utterly confused by the notion that exploring the multiverse deductively could be superior, under any circumstances, to working on alternatives with observable consequences, or even just devoting more effort to increasing our confidence in current theory. I see no way to escape the fact that deductive reasoning about unobservables, no matter how well grounded in established theory, requires belief. And systematic, potentially interminable reliance on belief would be a radical, arguably self-negating paradigm shift in the way science is currently performed, at least at the level of an entire discipline. How can being correct even matter under such circumstances?

  14. fuzzy says:

    hi lee smolin,

    i would like to ask you to elaborate your point concerning “falsifiable predictions” based upon “cosmological natural selection”.

    can you provide me with the proof of the upper bound you have cited? what are the uncertainties in the prediction? moreover, can you recognize or not a quark star with a neutron crust (that can be a rather heavy object) from a “true” neutron star, on observational bases?


  15. Lee Smolin says:

    Dear Fuzzy,

    The argument is in many places beginning with my 1992 paper and my 1997 book. For a recent discussion with references see
    The relevant calculations of the UML of a kaon condensate neutron star are not mine, they are discussed in James M. Lattimer, M. Prakash, What a Two Solar Mass Neutron Star Really Means. 4. arXiv:1012.3208 , to appear in Gerry Brown’s Festschrift; Editor: Sabine Lee (World Scientific)

    I haven’t thought about how a quark star might be produced or distinguished observationally. Is there a plausible argument that one might be the remnant of a supernova?

  16. Tmark48 says:

    The multiverse, along with the anthropic principle, in some sense “explains” fine tuning to me, and I like that. It is not traditional science, but it is not religion either. If, someday, fine tuning can be explained without these concepts, I will be happier.

    It explains jack shit. You say it is not traditional science implying that it is some kind of science. No, it is no science at all. I think scientific faculties should start doing a very heavy selection in terms of students that want to start a scientific career. Start explaining to them what the scientific method is all about. It seems an ever increasing percentage of those students (especially those that go into theoretical high energy physics or theoretical cosmology) suddenly forget this principle. So when are you going to discredit Galileo ?

  17. Neil says:


    I was careful to say that it “explains” it to me. If you think my standards of explanation are too low, fine.

    The point is, there are levels of explanation. Dark matter is a good example. We do not know what it is, and have not isolated a single piece of it, yet it provides an “explanation” for things that cannot be explained otherwise.

    It may be that the dark matter explanation is completely wrong and a better explanation will be discovered. Actually, I hope so. Likewise, and perhaps more likely, the multiverse will not be needed. For now, they are explanations.

  18. fuzzy says:

    dear lee smolin,

    i understand that you have not exhibited a proof but an argument, however, i am sorry, but i fail to find it convincing. when you state: “as low as possible”, you mean: “as low as possible compatibly with that we know now”. thus, the borderline is set from what we know now, and in fact, it changed in the course of the time. for this reason, i think that the lower bound of 2 solar masses tests the correctness/completeness of our actual ideas of astrophysics and of nuclear physics, rather than fundamental physics.

    (incidentally, concerning that, i am not sure that there is a very clear idea of the uncertainties; i do not know whether also rotation might somehow play a role; the role of quark matter remains largely unknown; but this is not the issue under discussion).

    thanks for the references and the patience.

  19. CVP says:

    It seems pretty clear that putting large sums of money into terrestrial accelerators is a game that is about over. Let’s put that money to work in looking at the rest of our universe and see what we can determine. Many of the puzzles seem to involve gravity in one way or another, and our universe has a lot of gravitational (as well as other) experiments underway. I think the HEP community is having a hard time accepting that their day in the sun, and their method of working, is coming to an end.

    In terms of the debates about multiverse pursuits, I think theorists, including many on this blog, have a confusion about what the word “explain” should mean. Claiming that a universe is anthropically selected from an infinite ensemble of randomly produced unobservable universes is not really an explanation of anything. They are “just so” stories. Such a hypothesis can never be true or false in any useful definition of those words. Theorists need to think about those notions. If it turns out the universe has no free-parameter explanation we can determine – OK so be it – don’t create a non-explanation explanation and try to shill it for funding.

  20. martibal says:

    A question maybe a bit off topic (I let Peter decide) but I take the occasion of this discussion to ask something I never understood about anthropic principle/multiverses: the anthropic principle states that the value of the fundamental constants are as they are, because otherwise we would not be here to ask why the constants have the value they have, right ? But have the simulations of these universes-with-other-values-of-the-fundamental-constants been pushed so far, that one can claim with certainty that – at no point of their history – no intelligence form (difference than ours) can emerge and wonder why the constants have the value they have ? Said differently: to what extend can one trust simulations of universes with different values of the fundamental constants, based solely on the (very approximative, cf e.g. dark matter) knowledge of our one single universe ?

  21. Peter Woit says:


    I don’t want to encourage a rehash here now of problems with anthropics, but, yes, one of the well-known problems is that it’s not at all clear that if you change fundamental parameters and get very different chemistry and nuclear physics, there won’t be some way for “intelligence” to emerge from this.

    Then, of course, given pieces like Siegfried’s, there’s the question of whether intelligence actually did emerge in our particular universe….

  22. martibal says:

    Peter: thanks ! Your last remark sounds like a nice no-go theorem against anthropics 🙂

  23. Evert says:

    I am no scientist, just a very stupid layman interested in understanding “reality” (whatever that may be). While I agree that certain theories posed by the scientific community are questionable (like string theory or multiverses), I would like to think the scientific community could transcend the notion of “war” and create a field of study of its own related to these theories rather than dismiss them to philosophy or (god forbid) theology.
    We need something that is at least in part based on scientific thinking which can at some point be either incorporated into science or debunked properly rather than throwing everything in the corner of the opposite of the spectrum of thinking.

    Surely there must be some middle ground? If not for the “purity” of science at least for the greater good of human understanding of “reality”.
    Personally (remember I am no scientist) I always thought that it was a theoretical scientist’s job to concoct (forgive the undignified term) theories based on probabilities of possibilities left open by our understanding of the universe, and that it is the practical scientists job to either confirm of debunk those theories. However, based on discussions and arguments on blogs and videos all over the internet I am inclined to think I was wrong and no matter the field of science, it seems to me it is more important trying to convince each other based on arguments long before we are capable of proving or disproving something practically. This whole war seems to me a war of wits rather than a constructive means to come to an answer?
    By no means do I mean to insult anyone and I apologise if I offend in any way. But it seems to me it would be preferable to have a lot of silly and contradictory theories in my inbox waiting for a time in which they can be tested, rather than wasting energy in convincing each other to be right. That been said, I understand the need for discussion since it can lead to new insights. But at this point I feel a lot of discussions do not serve this purpose any more and are more subjective than objective.
    Again, I do not want to start a war of my own and by no means is this meant as critique, it is simply my observation as an idiot.
    In the end, what matters is how we all (the entire human race, intellectuals like you and idiots like me) understand reality and base our lives upon it. And while I accept that certain concepts will remain enigmatic to the greater public (like infinity for example, which deludes me to no end, despite analogies of hotel rooms) in the end we want some sort of straws we can grasp, and I for one would like those straws to be tangible (at least to some extent) rather than magical or biblical.
    As such I understand and am a proponent of opposite theories in science, but I fail to see the advantage of them becoming heated arguments to the point of name-calling, rejecting them to the land of theology or worse.
    Then again, I may either misunderstand or be a hopeless utopian.

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