Column: Welcome to the Multiverse

By Sean Carroll | October 18, 2011 9:47 am

Many of you may know that Discover is not only a web site that hosts a diverse collection of entertaining blogs, but also publishes a monthly “magazine” printed on paper. Wild, right? Just ask this baby, who can tell you that a magazine is kind of broken when compared to an iPad.

Nevertheless, people read these things like crazy. I have recently started contributing an occasional column to the print magazine, known as “Out There.” (Our blog neighbor Carl Zimmer has been columnizing about the brain for a while now.) My first column appeared in the October issue (which comes out in September), and is now online — check it out.

The issue I’m tackling, under the draconian word count limit of an actual print magazine, is whether it’s scientific to talk about the multiverse. (Spoiler: it is!) Let me know what you think.

CATEGORIZED UNDER: Science, Top Posts
  • Gene

    I liked it. No doubt at this stage in the evolution of the theory we should look for as much collaborative evidence as is possible. This is the obvious strategy for now, but I’m not certain it ultimately works- given the complexity of the situation. My guess is that whether its in the context of the string landscape, or even the interpretation of QM, we will have to ultimately decide these realities on the basis of personal judgment rather than experiment alone.

  • Justin

    Sean you’re undoubtedly a better physicist than me, but I think there is a mistake in your article: “Everything we see emerged 13.7 billion years ago from the hot, dense state known as the Big Bang, so we cannot observe anything more than 13.7 billion light-years away.”

    The edge of the observable universe is further away than that, owing to continual cosmic expansion during the 13.7 billion years that the light was traveling towards us; the comoving distance to the edge is now 46 billion light-years.

    http://arxiv.org/abs/astro-ph/0310571
    http://arxiv.org/abs/astro-ph/0310808

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Hmm, I knew that. Not sure how that got into the column, whether it was my brain fart or an editing snafu… I’ll check.

  • Joel Rice

    string theory would allow lots of possibilities, but it would be nice to have some reason to believe in the necessary supersymmetry that goes along with it. A different approach might be that one algebra defines all the particles and their relationships, which might well be fixed and not allow any adjustments. That would be different from Dirac Algebra defining the electron but not the photon, which has to be put in by hand, and invites fiddling with the coupling. Since one would not want any parameters put in by hand, if the algebra requires the construction of Atoms, there would be increasingly tight constraints on the mass of the electron, etc. In that view, all Bangs would be equivalent, and the ‘laws’ would be the same across all Bangs. Anyway, such an algebra would be a game-changer – rather different kind of critter from Dirac algebra.

  • http://boomerstomexico.com david lawrence

    maybe, in response to justin (comment 2), you meant that nothing that happened more than 13.7 billion years ago can be observed. looking back in time, not in distance, as it were.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Upon further review, at one point in the editing process the phrase “so we cannot observe anything more than 13.7 billion light years away” was tacked onto the end of the sentence I wrote. I had a chance to catch it on the final pass, but didn’t. Will try to be more careful next time.

  • Cosmonut

    Am I right in believing that the “diverse multiverse” isn’t really a prediction of either inflation or string theory ?

    If I understand right, inflation generically predicts a huge number of pocket universes where the “inflaton field” (whatever that is) decays. But for all we know, these might be identical to our own in terms of number of dimensions, constants of nature, etc.

    String theory in its current incarnation allows 10^500 solutions, but there is no evidence that any of these correspond to anything in reality.

    It is merely CONJECTURED that one of the 10^500 solutions corresponds to our own universe (not at all clear at the moment) and it is an even bigger conjecture (one which we don’t even know how to verify) that the other solutions might be realized in these other pocket universes.

    I wish the level of speculativeness was made more clear in articles about the multiverse, including this one. You did that very well in the video lecture on cosmic inflation.

    There’s nothing wrong with speculating about other universes, but I get annoyed when the multiverse is invoked as an “explanation”, for, say, why there are 3 dimensions of space.

    To use your analogy, this is like the inhabitants of your cloudy planet claiming that apples fall to the ground because “there are zillions of other worlds where apples move off in all possible directions. We just happen to be on the one where they fall down..”

  • http://backreaction.blogspot.com/ Bee

    I suppose if superluminal information exchange is possible the multiverse increases exponentially in scientification.

    (Our babies also grab and point at printed images and they’ve never seen a touch screen.)

  • Spinons

    As Sean discussed in his Column, the multiverse pictures are mainly driven by two theoretical ideas: Inflation and String theory, both of which remain theoretical speculations at this stage.
    There is no experimental evidence definitely confirming either of these ideas.

    In this sense, I would say that the current multiverse mania is not that different from the approach of Giordano Bruno. By supplementing these ideas with a bunch of mathematical equations doesn’t make it a more scientific theory than pure philosophizing.

    I am not saying that scientists should not think about the possibility of multiverse. But to make it a solid physical science, one still needs experimental or observational results to verify it.

    By the way, at the end of the Column, the example of a tribe of primitive cos­mol­ogists seems to suggest the anthropic argument. Without experiments or observations, it is equally valid to say that their planet is so hospitable by Intelligent Design, which apparently makes sense to many people.

  • Flagitious Nebulon

    You say,
    ” It’s possible that another universe bumped into ours early on and left a detectable signature in the cosmic background radiation…”

    But, as you have explained many times, our universe was initially smooth to a fantastic degree of accuracy — that´s where the arrow of time comes from. If another universe bumped into ours, even gently, wouldn´t that ruin the extreme initial smoothness [absent an extreme fine-tuning]?

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    It might, which is why the bumping would have to be extremely gentle indeed, and why the scenario is something of a long shot. But that doesn’t mean we shouldn’t look, which is exactly what people are doing:

    http://blogs.discovermagazine.com/cosmicvariance/2010/12/22/observing-the-multiverse-guest-post/

  • http://marcofrasca.wordpress.com/ Marco Frasca

    Hi Sean,

    My view is that also people talking about atoms were considered foolish. So, I cannot say to you: “Please, do not discuss the argument of multiverse being just sci-fi”. I would be foolish my self…

    Best,

    Marco

  • Count Iblis

    The funny thing is that if there exists a multiverse, then given that you don’t have precise information about even your own precise state, let alone of your local environment, you cannot locate yourself at precisely one spot in the multiverse. You can be any of a large number of similar copies that are located at a vast distance from each other, that have the same information about their local environments.

    Each has the same consciousness, so it would be wrong to say that out of these copies you are one of them and not some other and that you just don’t know which one. This makes the question of searching for evidence of the multiverse a bit ironic, you are already at multiple locations in the multiverse :)

  • http://wavefunction.fieldofscience.com Curious Wavefunction

    In his latest post, Peter Woit thinks that your argument is circular.

  • Carleigh

    So, The Fried-Egg Cosmologist gets a column with Discover. I think that you will go down in the annals of science right next to Stanton Friedman, aka The Flying Saucer Physicist.

    Nice!

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Actually, String Theory and the multiverse are not science, according to the Great Scientists:

    “But before mankind could be ripe for a science which takes in the whole of reality, a second fundamental truth was needed, which only became common property among philosophers with the advent of Kepler and Galileo. Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and ends in it. Propositions arrived at by purely logical means are completely empty as regards reality. Because Galileo saw this, and particularly because he drummed it into the scientific world, he is the father of modern physics–indeed, of modern science altogether.” -Albert Einstein, Ideas and Opinions. MDT’s dx4/dt=ic honors Galileo and Einstein, as it both “starts and ends” in experience!

    “Once it was recognised that the earth was not the center of the world, but only one of the smaller planets, the illusion of the central significance of man himself became untenable. Hence, Nicolaus Copernicus, through his work and the greatness of his personality, taught man to be honest.” -Albert Einstein, Message on the 410th Anniversary of the Death of Copernicus, 1953

    I don’t like that they’re not calculating anything. I don’t like that they don’t check their ideas. I don’t like that for anything that disagrees with an experiment, they cook up an explanation-a fix-up to say, “Well, it might be true.” For example, the theory requires ten dimensions. Well, maybe there’s a way of wrapping up six of the dimensions. Yes, that’s all possible mathematically, but why not seven? . . . So the fact that it might disagree with experience is very tenuous, it doesn’t produce anything; it has to be excused most of the time. It doesn’t look right.–Nobel Lareate R.P. Feynman

    But superstring physicists have not yet shown that theory really works. They cannot demonstrate that the standard theory is a logical outcome of string theory. They cannot even be sure that their formalism includes a description of such things as protons and electrons. And they have not yet made even one teeny-tiny experimental prediction. Worst of all, superstring theory does not follow as a logical consequence of some appealing set of hypotheses about nature.—Nobel Laureate Sheldon Glashow

  • http://www.darkbuzz.com Roger

    The main point of the article seems to be that Sean has a lot of untestable speculations, but it is all okay if we accept some redefinition of science.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Roger–why would we want to redefine science?

    What is wrong with Einstein’s, Galileo’s, Netwon’s, Bohr’s, Copernicus’s, and Feynman’s definition of science?

    :)

  • Phil

    I’m posting this comment because Peter Woit turned off comments for his posting on this topic — something he rarely does, which leads me to think he does not want to see perfectly sensible comments that disagree with his opinion. I will offer such a comment.

    The truth of the matter is that string theory IS testable. Like quantum field theory, string theory has many possible theories. One particular QFT describes our universe pretty well and, therefore, can be regarded as an effective field theory to a more fundamental field theory we don’t know yet. String theory is one such possibility composed of many possible theories. One such theory is that which holds that TeV scale strings should appear at the LHC and that there are large extra dimensions capable of being observed at the LHC. The LHC has observed no such signatures, therefore that particular theory is wrong.

    But it is still in principle possible to test string theory. All you have to do is collide particles with ever increasing energy, all the way up to the Planck scale, and if you observe stringy behavior, extra dimensions, etc., and if you find a string theory that explains those measurements, then you have experimentally validated string theory. The same things is true for QFT. We found a particular QFT that matches with experiment, even though there are possibly an infinite number of possible QFTs. The same things can be done with string theory, only the wait and experimental effort needed will most likely be very very very long!

    So it’s NOT true to say that string theory is untestable because of the multiverse. It is untestable because we do not have the technology to conduct experiments at every energy scale all the way up to the Planck scale. When we do (if we do), we will have the ability to test string theory. But string theory IS in itself testable.

    Is there anything wrong with what I just said?

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Phil,

    Actually, Nobel Laureate Physicists disagree with you:

    [String Theory] has no practical utility, however, other than to sustain the myth of the ultimate theory. There is no experimental evidence for the existence of strings in nature, nor does the special mathematics of string theory enable known experimental behavior to be calculated or predicted more easily. . . String theory is, in fact, a textbook case of Deceitful Turkey, a beautiful set of ideas that will always remain just barely out of reach. Far from a wonderful technological hope for a greater tomorrow, it is instead the tragic consequence of an obsolete belief system-in which emergence plays no role and dark law does not exist.[xlviii] —A Different Universe, Nobel Laureate Robert Laughlin

    It is anomalous to replace the four-dimensional continuum by a five-dimensional one and then subsequently to tie up artificially one of those five dimensions in order to account for the fact that it does not manifest itself. -Einstein to Ehrenfest (Imagine doing this for 10-30+ dimensions!)

    String theorists don’t make predictions, they make excuses[xl]. – Feynman, Nobel Laureate

    String theory is like a 50 year old woman wearing too much lipstick.[xli] -Robert Laughlin, Nobel Laureate

    Actually, I would not even be prepared to call string theory a “theory” rather a “model” or not even that: just a hunch. After all, a theory should come together with instructions on how to deal with it to identify the things one wishes to describe, in our case the elementary particles, and one should, at least in principle, be able to formulate the rules for calculating the properties of these particles, and how to make new predictions for them. Imagine that I give you a chair, while explaining that the legs are still missing, and that the seat, back and armrest will perhaps be delivered soon; whatever I did give you, can I still call it a chair?[xlii] –‘t Hooft, Nobel Laureate

    It is tragic, but now, we have the string theorists, thousands of them, that also dream of explaining all the features of nature. They just celebrated the 20th anniversary of superstring theory. So when one person spends 30 years, it’s a waste, but when thousands waste 20 years in modern day, they celebrate with champagne. I find that curious.[xliii] –Sheldon Glashow, Nobel Laureate

    Best,

    Dr. E :)

  • Brian Too

    @19. Phil,

    Yes, there is something wrong with what you said.

    My understanding is that in order to create experiments that operate at the Planck scale, you need a particle accelerator the size of the universe. One that would consume the entire resources of the universe!

    There is a world of difference between “testable in principle” and “testable by our civilization”. Any theory which cannot, in good faith, produce a viable testing regime within the next 100 years, falls into the realm of philosophy. Scientific dead ends.

    Why 100 years? It falls outside the lifetime of any scientist who would propose the theory needing testing. Worse yet, the passage of 100 years by no means brings the needed resources into reach. There is no visible mechanism or advance that provides hope, let alone assures, that 100 years from now, experimental verification will be possible. All that we know is that 100 years will have passed and very probably, a plausible testing regime will still be so far out of reach as to be invisible.

    Anything wrong with what I said (now watch the fur fly)?

  • Stephen

    Last month I decided not to renew my Discover subscription of 8 years because of the global warming hysteria articles which have become a staple of every issue this year. I find out today that Discover decided to add a string theory/multiverse column that fits right in with the magazine’s pandering to pop culture pseudo-science. Authentic scientific journalism is backed up by experimental results not philosophical musings with circular reasoning. Maybe a new column should be about the fantastic misrepresentations made by the leading climate change evangelicals, oops I mean scientists. Discover was once a trusted science publication, those days have passed.

  • Phil

    @20, Dr. Eliot,

    Do you have any thoughts of your own on this matter? If so, I would love to read them!

    @21 Brian,

    How do you know in 100 years, or in 1000 years, we won’t be technological enough to be able to somehow probe the Planck scale? Many years ago, people like you thought that atoms were forever unobservable. Now, we can manipulate atoms one by one and spell “IBM” with them.

    Maybe it will take a million years, or a billion years, until some species comes up with the technology to find out what happens at the Planck scale. And then we (or they) will know if the theory that describes their observations is string theory or something else.

    In other words, never say never. If string theory is right, there should be signs of it at the Planck scale and, who knows, maybe we’ll get there some day.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Phil,

    One of the reasons we know that String Theory makes no definitive predictions at the Planck scale is that String Theory has no definitive equations, nor solutions. So even when we find out what happens at the Planck scale, we won’t be testing String Theory, as String Theory has no equations. If, Phil, you happen to believe String Theory has definitive equations, please do share them. Thanks! Also please share the definitive masses of the particles ST predicts, while you’re at it.

    :)

    I agree with the Greats that Multiverses and Strings are “Cargo Cult Science,” which the Great Feynman warned us of:
    http://www.lhup.edu/~DSIMANEK/cargocul.htm

    “But this long history of learning how not to fool ourselves–of
    having utter scientific integrity–is, I’m sorry to say, something
    that we haven’t specifically included in any particular course that
    I know of. We just hope you’ve caught on by osmosis.

    The first principle is that you must not fool yourself–and you are
    the easiest person to fool. So you have to be very careful about
    that. After you’ve not fooled yourself, it’s easy not to fool other
    scientists. You just have to be honest in a conventional way after
    that.

    I would like to add something that’s not essential to the science,
    but something I kind of believe, which is that you should not fool
    the layman when you’re talking as a scientist. I am not trying to
    tell you what to do about cheating on your wife, or fooling your
    girlfriend, or something like that, when you’re not trying to be
    a scientist, but just trying to be an ordinary human being. We’ll
    leave those problems up to you and your rabbi. I’m talking about
    a specific, extra type of integrity that is not lying, but bending
    over backwards to show how you are maybe wrong, that you ought to
    have when acting as a scientist. And this is our responsibility as
    scientists, certainly to other scientists, and I think to laymen.

    For example, I was a little surprised when I was talking to a
    friend who was going to go on the radio. He does work on cosmology
    and astronomy, and he wondered how he would explain what the
    applications of this work were. “Well,” I said, “there aren’t any.”
    He said, “Yes, but then we won’t get support for more research of
    this kind.” I think that’s kind of dishonest. If you’re
    representing yourself as a scientist, then you should explain to
    the layman what you’re doing–and if they don’t want to support you
    under those circumstances, then that’s their decision.”
    –Nobel Laureate R.P. Feynman

    Nobel Laureate Philip Anderson also recognizes the destructive nature of Cargo Cult Science such as string theory, which takes us on back to pre-Baconian methods:

    “My belief is based on the fact that string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance. It proposes that Nature is the way we would like it to be rather than the way we see it to be; and it is improbable that Nature thinks the same way we do.

    The sad thing is that, as several young would-be theorists have explained to me, it is so highly developed that it is a full-time job just to keep up with it. That means that other avenues are not being explored by the bright, imaginative young people, and that alternative areer paths are blocked.” —Philip W. Anderson Physicist and Nobel laureate, Princeton

  • Phil

    Dr. McGucken,

    I don’t claim to be able to calculate standard model parameters with string theory. String theory is not my field. But what do you mean by “no definitive equations, nor solutions”? What kind of equations are you talking about? As for solutions, aren’t there something like 10^500 solutions? If someone comes along and finds a solution that allows one to calculate SM parameters and agrees with the SM and GR at low energies, what then?

  • Navneeth

    Phil’s reply to Brian:

    Maybe it will take a million years, or a billion years, until some species comes up with the technology to find out what happens at the Planck scale. And then we (or they) will know if the theory that describes their observations is string theory or something else.

    But this sort of near-blind-faith is choking the resources out of other approaches in fundamental theory/theoretical physics. [Disclaimer: I’m not a physicsist, but I’m going with what I’ve read from reliable sources with regard to trends — for instance, Lee Smolin’s book.] Can you seriously justify funding string theory research with an unproportionate amount of money when one doesn’t even have the slightest idea when and if it could be tested at all?

  • somebody

    If you can do Planck scale scattering, string theory is definitely testable. That doesn’t depend on the details of which solution (aka, which corner of the landscape) our world is in. The “stringiness” of matter at the Planck scale has distinct implications for scattering.

    So Dr. E, your suggestion that string theory is IN PRINCIPLE untestable is just the usual nonsense one hears against string theory. The real challenge is not that there are no experiments IN PRINCIPLE, but that the standard model is so amazingly successful that IN PRACTICE it is a huge challenge for us to do experiments that probe what lies beyond it.

    It boggles my mind that people geuinely think that there is some simple and easy way to rule out string theory as a theory of science. Really? You think people like Witten are sooooo stupid? The fact of the matter is that string theory remains both tantalizing and frustrating at the same time. And we do NOT have an easy way out of this quandary. Brain farts and opinionated garbage notwithstanding.

    You are not going to come up with a compelling two line argument why string theory is rubbish, not even science, etc. I for one would LOVE it, if it was that easy.

  • http://wavefunction.fieldofscience.com Curious Wavefunction

    I am not a physicist but I have to say I find it extremely disconcerting to hear arguments of the following kind:

    String theory predicts X. But to test X we will need accelerator/device/experiment Y which may or may not be possible to implement for about a thousand years. But until then we still need to accept string theory not only as a testable/verifiable theory but as our best bet for a unified theory.

    I understand that the fact that it may not be possible to test string theory any time soon does not rule it out. But neither should this make it the favorite contender for a theory of everything. The correct approach would be “Let’s wait and see”.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Phil,

    You answered your own question I believe: “As for solutions, aren’t there something like 10^500 solutions? If someone comes along and finds a solution that allows one to calculate SM parameters and agrees with the SM and GR at low energies, what then?”

    Yes if a theory predicts 10^500 different things, it predicts nothing.

    And, as there are 10^500 different solutions, it is rather embarrassing that none of them agree with the SM and GR at low energies, showing that String Theory is a joke that predicts 10^500 not ven wrong entities, but nothing that is right nor true nor good.

    You write, “But what do you mean by “no definitive equations, nor solutions”? What kind of equations are you talking about? As for solutions, aren’t there something like 10^500 solutions?” Yes! If there are something like 10^500 solutions, there are no DEFINITIVE SOLUTIONS.

    And yes–String Theory has no definitive equations. The elite non-theorists have been fooling the laymen, as Feynman warned the lesser physicists (non Nobel Laureates) would for cash gains from the trusting public. If you do not believe me, ask a String Theorist for the String Theory equation. They may call you names and hurl insults at you, but they will provide no equation as there are none. :)

    Also, String Theory is not a finite theory: The first page of String Theory in a Nutshell states in a footnoted sentence:

    String Theory has been the leading candidate … for a theory that consistently unifies all the fundamental forces of nature, including gravity. It gained popularity because it provides a theory that is UV finite.(1) . . . The footnote (1) reads: “Although there is no rigorous proof to all orders that the theory is UV finite…”[xxxviii] –STRING THEORY IN A NUTSHELL

    We don’t know what we are talking about[xxxix]. –Nobel Laureate David Gross on string theory

    The fact is that this book is about physics, and this implies that the
    theoretical ideas must be supported by experimental facts. Neither
    supersymmetry nor string theory satisfy this criterion. They are
    figments of the theoretical mind. To quote Pauli:
    They are not even wrong. They have no place here. –Nobel Laureate Martinus Veltman

    Nobel Laureate Richard Feynman, an heroic physicists who married commonsense to his mathematical genius, stated in 1987, a year before his death:

    “…I think all this superstring stuff is crazy and it is in the wrong direction. … I don’t like that they’re not calculating anything. I don’t like that they don’t check their ideas. I don’t like that for anything that disagrees with an experiment, they cook up an explanation—a fix-up to say “Well, it still might be true.”” –Nobel Laureate Richard Feynman

    String theory has no credibility as a candidate theory of physics. Recognizing failure is a userful part of the scientific strategy. Only when failure is recognized can dead ends be abandoned and useable pieces of failed programs be recycled. Aside from possible utility, there is a responsibility to recognize failure. Recognizing failure is an essential part of the scientific ethos. Complete scientific failure must be recognized eventually.” –Dan Friedan, early Rutgers String Theorist

    This book is about physics, and this implies that theoretical ideas must be supported by experimental facts. Neither supersymmtry nor string theory satisfy this crieterion. They are figments of the theoretical mind. –Dan Friedan

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Somebody Says,

    String Theory has no equations, and thus it does not, and cannot predict anything. If you believe otherwise, please share with me 1. String Theory’s equations and 2. the masses of the particles it predicts.

    Einstein and the Greats stated that physics begins and ends in experience and physical reality, but there is no physical instance of a string (no beginning in physical reality), nor is there any way to test for one (not ending in physical reality either.)

    Please do not take my word for this, but listen to the Nobel Laureates and revered experts:

    Nobel Laureate Max Planck: Let us get down to bedrock facts. The beginning of every act of knowing, and therefore the starting-point of every science, must be our own personal experience.[xiv] (All physicists have personally experienced the double-slit experiment, and as relativity tells us that photons remain stationary in x4, x4 must thus be propagating at c with both a wavelike and quantum nature!)

    Nobel Laureate Einstein: Mathematics are well and good but nature keeps dragging us around by the nose.[xv]

    Einstein: The theory must not contradict empirical facts. . . The second point of view is not concerned with the relation to the material of observation but with the premises of the theory itself, with what may briefly but vaguely be characterized as the “naturalness” or “logical simplicity” of the premises of the basic concepts and of the relations between these which are taken as a basis. [xvi]

    Planck: That we do not construct the external world (String Theory) to suit our own ends in the pursuit of science, but that vice versa the external world forces itself upon our recognition with its own elemental power, is a point which ought to be categorically asserted again and again . . . From the fact that in studying the happenings of nature . . . it is clear that we always look for the basic thing behind the dependent thing, for what is absolute behind what is relative, for the reality behind the appearance and for what abides behind what is transitory. . this is characteristic not only of physical science but of all science.[xvii] (dx4/dt=ic is the “basic, abiding thing” behind all relativity, entropy, and QM!)

    Einstein: Truth is what stands the test of experience.[xviii]

    Nobel Laureate Werner Heisenberg: Science. . . is based on personal experience, or on the experience of others, reliably reported. . . Even today we can still learn from Goethe . . . trusting that this reality will then also reflect the essence of things, the ‘one, the good, and the true (no multiverse!).[xix]

    The great irony of string theory, however, is that the theory itself is not unified. . . For a theory that makes the claim of providing a unifying framework for all physical laws, it is the supreme irony that the theory itself appears so disunited!![xlvi] Introduction to Superstrings & M-Theory –Kaku

    Nobel Laureate Sheldon Glashow: “Is string theory a futile exercise as physics, as I believe it to be? It is an interesting mathematical specialty and has produced and will produce mathematics useful in other contexts, but it seems no more vital as mathematics than other areas of very abstract or specialized math, and doesn’t on that basis justify the incredible amount of effort expended on it.

    Until string people can interpret perceived properties of the real world they simply are not doing physics. Should they be paid by universities and be permitted to pervert impressionable students? Will young Ph.D’s, whose expertise is limited to superstring theory, be employable if, and when, the string snaps? Are string thoughts more appropriate to departments of mathematics, or even to schools of divinity, than to physics departments? How many angels can dance on the head of a pin? How many dimensions are there in a compacted manifold, 30 powers of ten smaller than a pinhead? ” –Nobel Laureate Sheldon Glashow

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Curious Wavefunction,

    You write, “I am not a physicist but I have to say I find it extremely disconcerting to hear arguments of the following kind: String theory predicts X. But to test X we will need accelerator/device/experiment Y which may or may not be possible to implement for about a thousand years.”

    But String Theory has no equations, and thus it does not, and cannot predict anything. If you believe otherwise, please share with me 1. String Theory’s equations and 2. the masses of the particles it predicts.

    String Theory violates Einstein et al.’s definition of science:

    Einstein: Time and again the passion for understanding has led to the illusion that man is able to comprehend the objective world rationally by pure thought without any empirical foundations (string theory has no equations nor empirical foundations)—in short, by metaphysics.[xxiii] (MDT begins and ends with empirical foundations!)

    Any intelligent fool can make things bigger, more complex (String Theory’s 10^500 “solutions”), and more violent. It takes a touch of genius—and a lot of courage—to move in the opposite direction.[xxiv] –Einstein

    Nobel Laureate: “Actually, I would not even be prepared to call string theory a “theory” rather a “model” or not even that: just a hunch. After all, a theory should come together with instructions on how to deal with it to identify the things one wishes to describe, in our case the elementary particles, and one should, at least in principle, be able to formulate the rules for calculating the properties of these particles, and how to make new predictions for them. Imagine that I give you a chair, while explaining that the legs are still missing, and that the seat, back and armrest will perhaps be delivered soon; whatever I did give you, can I still call it a chair?” [xlii] –‘t Hooft, Nobel Laureate

    Nobel Laureate: “It is tragic, but now, we have the string theorists, thousands of them, that also dream of explaining all the features of nature. They just celebrated the 20th anniversary of superstring theory. So when one person spends 30 years, it’s a waste, but when thousands waste 20 years in modern day, they celebrate with champagne. I find that curious.[xliii]” –Sheldon Glashow, Nobel Laureate

    Nobel Laureate Max Born: Max Born wrote, “All great discoveries in experimental physics have been made due to the intuition of men who made free use of models which for them were not products of the imagination but representations of real things (strings aren’t real things).”

    Albert Einstein: Before I enter upon a critique of mechanics as a foundation of physics, something of a broadly general nature will first have to be said concerning the points of view according to which it is possible to criticize physical theories at all. The first point of view is obvious: The theory must not contradict empirical facts (there are not 10 or twenty dimensions in empirical reality). . . The second point of view is not concerned with the relation to the material of observation but with the premises of the theory itself, with what may briefly but vaguely be characterized as the “naturalness” or “logical simplicity” of the premises (of the basic concepts and of the relations between these which are taken as a basis) (string theory is not simple nor natural). This point of view, an exact formulation of which meets with great difficulties, has played an important role in the selection and evaluation of theories since time immemorial.

    Best,

    Dr. E :)

  • Joel Rice

    Dr Elliot – a number of these esteemed gents also decry the fact that fermion generations are a complete mystery. I think it makes more sense to go after that problem than speculate about strings. To put it crudely, which makes more sense – strings or something more tetrahedral ? Space and SpaceTime are defined combinatorially in Clifford Algebra, and one might expect that particles are also defined in a combinatorial fashion, just so all this stuff fits together, but it can not be Clifford – it would have to be complex octonions – without the supersymmetry. So the real issue is not whether ST is testable or a nice theory – but whether there is a structure that manifestly sheds light on the Generation Puzzle. If so, I would think it more likely to lead to results than ST. Yes, I know that Streater regards octonions as a Lost Cause, but he was not talking about complex octonions defining all the particles, but rather using octonions in the mechanics – eg octonions instead of Dirac algebra, which would blow up a methodology that works very well. One can get something that looks like generations of oscillators simply with “o(a(bc))” and all permutations and associations – just because ‘o’ can be in slot 0,1,2,3. The oscillators in slots 1,2,3 look fermionic. No group theory, no PDEs – just elementary combinatoric type stuff. No Theory either, but at least it looks intersting and relevant to the generation puzzle. Oh, and every oscillator can be taken as pointlike with a complex phase, which looks like it might fit very well with Feynman’s approach in QED: the strange theory … So it might not be so hopeless after all. In which case, strings might well be superfluous, along with multiverses.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Joel,

    You write, “A number of these esteemed gents also decry the fact that fermion generations are a complete mystery.”

    Who? Where do they do this? Could you please provide quotes/references?

    Thanks!

  • somebody

    Curious Wavefunction says: “I understand that the fact that it may not be possible to test string theory any time soon does not rule it out. But neither should this make it the favorite contender for a theory of everything. The correct approach would be “Let’s wait and see”.”

    I think the correct standpoint is to work on your theory (whatever it might be) while waiting. Unlike what you seem to think (which is okay, since you say you are not a physicist), there are not many “contenders” for consistent Planck scale physics. The one that we have, we don’t understand very well. Thats pretty much the state of the art. What do you suggest we do? Call off curiosity and not try to fully figure out the half-cooked candidate (i.e., string theory) that seems to be both very tantalizing and very infuriating at the same time?

    String theory is not more expensive to fund than pure mathematics (which is even more “useless”, arguably), so that argument seems weak to me. It would be great if someone comes up with another theory that is better than string theory, but revolutions don’t appear by orchestration, so its hard to do anything with that thought. The only thing that we can really do is to encourage work on what seems promising – we don’t have the benefit of hindsight. Revolutions are by definition going to be outliers. String theory itself was an outlier for the longest time until Green and Schwarz found a remarkable result in 1984.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Monte,

    Sure! No problem. :)

    It is important that the laymen understand that the Multiverse/String Theory is *not* science as defined by the Greats & Nobel Laureates!:

    Einstein: Truth is what stands the test of experience.[xviii] (Nobody has experienced a Multiverse nor Strings!)

    Heisenberg: Science. . . is based on personal experience, or on the experience of others, reliably reported. . . Even today we can still learn from Goethe . . . trusting that this reality will then also reflect the essence of things, the ‘one, the good, and the true. (There is but one–not a multiverse!) [xix]

    Schrodinger: The world is given but once (no multiverse!). . . The world extended in space and time is but our representation. Experience does not give us the slightest clue of its being anything besides that.

    Einstein: Time and again the passion for understanding has led to the illusion that man is able to comprehend the objective world rationally by pure thought without any empirical foundations—in short, by metaphysics.[xxiii] (MDT begins and ends with empirical foundations! There are no empirical foundations for the Multiverse!)

    It is anomalous to replace the four-dimensional continuum by a five-dimensional one and then subsequently to tie up artificially one of those five dimensions in order to account for the fact that it does not manifest itself. -Einstein to Ehrenfest (Imagine doing this for 10-30+ dimensions and multiple universes!)

    The fact is that this book is about physics, and this implies that the
    theoretical ideas must be supported by experimental facts. Neither
    supersymmetry nor string theory satisfy this criterion. They are
    figments of the theoretical mind. To quote Pauli:
    They are not even wrong. They have no place here. –Nobel Laureate Martinus Veltman

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear somebody Says:

    What is your real name? I would like to interview you for a documentary.

    Actually physics comes from individuals, not groupthink bureaucracies, which is what string theory is.

    Please stop ignoring the Nobel Laureate physicists, somebody says (Sean Carroll perhaps?):

    Nobel Laurete Sheldon Glashow:

    Why is the smart money all tied up in strings? Why is so much theoretical capital
    expended upon the properties of supersymmetric systems of quantum strings propagating
    in ten-dimensional space-time? . . . years of intense effort by dozens
    of the best and the brightest have yielded not one verifiable prediction, nor should any
    soon be expected. Called “the new physics” by its promoters, it is not even known to
    encompass the old and established standard model. –Sheldon Glashow, Nobel Laureate & Paul Ginsparg, Ph.D.
    In lieu of the traditional confrontation between theory and experiment, superstring
    theorists pursue an inner harmony where elegance, uniqueness and beauty define truth.
    The theory depends for its existence upon magical coincidences, miraculous cancellations
    and relations among seemingly unrelated (and possibly undiscovered) fields of mathemat-
    ics. Are these properties reasons to accept the reality of superstrings? Do mathematics
    and aesthetics supplant and transcend mere experiment? Will the mundane phenomeno-
    logical problems that we know as physics simply come out in the wash in some distant
    tomorrow? Is further experimental endeavor not only difficult and expensive but unneces-
    sary and irrelevant? Contemplation of superstrings may evolve into an activity as remote
    from conventional particle physics as particle physics is from chemistry, to be conducted
    at schools of divinity by future equivalents of medieval theologians. For the first time since
    the Dark Ages, we can see how our noble search may end, with faith replacing science once
    again. Superstring sentiments eerily recall “arguments from design” for the existence of a
    supreme being. Was it only in jest that a leading string theorist suggested that “super-
    strings may prove as successful as God, Who has after all lasted for millennia and is still
    invoked in some quarters as a Theory of Nature”? –Sheldon Glashow, Nobel Laureate & Paul Ginsparg, Ph.D.

    The trouble is that most of superstring physics lies up at the Planck mass — about
    10 GeV – and it is a long and treacherous road down to where we can see the light of
    day. A naive comparison of length scales suggests that to calculate the electron mass from
    superstrings would be a trillion times more difficult than to explain human behavior in
    terms of atomic physics. Superstring theory, unless it allows an approximation scheme for
    yielding useful and testable physical information, might be the sort of thing that Wolfgang
    Pauli would have said is “not even wrong.” It would continue to attract newcomers to the
    field simply because it is the only obvious alternative to explaining why certain detectors
    light up like video games near the end of every funding cycle.
    –Sheldon Glashow, Nobel Laureate & Paul Ginsparg, Ph.D., Desperately Seeking Superstrings

    In the old days we moved up in energy step by step, seeing smaller and smaller struc-
    tures. Observations led to theories or models that suggested further experiments. The
    going is getting rougher; Colliders are inordinately expensive, detectors have grown im-
    mense, and interesting collisions are rare. Not even a politically popular “Superstring
    Detection Initiative” with a catchy name like “String Wars” could get us to energies where
    superstrings are relevant. We are stuck with a gap of 16 orders of magnitude between
    theoretical strings and observable particles, unbridgeable by any currently envisioned ex-
    periment. Conventional grand unified theories, which also depend on a remote fundamental
    energy scale (albeit one extrapolated upward from known phenomena rather than down-
    ward from abstract principle), retain the grand virtue that, at least in their simplest form,
    they were predictive enough to be excluded — by our failure to observe proton decay.
    –Sheldon Glashow, Nobel Laureate & Paul Ginsparg, Ph.D., Desperately Seeking Superstrings

    How tempting is the top-down approach! How satisfying and economical to explain
    everything in one bold stroke of our aesthetic, mathematical or intuitive sensibilities, thus
    displaying the power of positive thinking without requiring tedious experimentation! But
    a priori arguments have deluded us from ancient Greece on. Without benefit of the
    experimental provocation that led to Maxwell’s equations and, inevitably, to the special
    theory of relativity, great philosophers pondering for millennia failed even to suspect the
    basic kinematical structure of space-time. Pure thought could not anticipate the quantum.
    And even had Albert Einstein succeeded in the quest that consumed the latter half of his
    life, somehow finding a framework for unifying electromagnetism and gravity, we would by now have discarded his theory in the light of experimental data to which he had no access. He had to fail, simply because he didn’t know enough physics. Today we can’t exclude the
    possibility that micro-unicorns might be thriving at a length scale of 10−18 cm. Einstein’s
    path, the search for unification now, is likely to remain fruitless.
    –Sheldon Glashow, Nobel Laureate & Paul Ginsparg, Ph.D., Desperately Seeking Sup

  • Joel Rice

    33 Dr Elliot – sure.
    1) Feynman QED strange theory … p 145 “This repetition of particles with the same properties but heavier masses is a complete mystery.”
    2) M. Veltman – Facts and Mysteries … passim … in about a dozen places !
    also remarks about strings you quoted above.
    3) Weinberg Dreams of a Final Theory p 26 quoting David Gross “… why is the pattern of matter replicated in three generations of quarks and leptons …”
    I’m sure Glashow and others have made similar remarks.
    I should make a file of such references, but thought it “well known” as a central mystery.
    Anyway I agree with your remarks, and it is nice to see the quotes you provide all in one place.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Thanks Joel,

    Could you please provide the exact quotes and places where M. Veltman and Glashow state what you say they stated? Thanks!

    I’m not sure this counts as a scholarly reference: “2) M. Veltman – Facts and Mysteries … passim … in about a dozen places ! also remarks about strings you quoted above.” And I’m not sure what you mean by “also remarks about strings you quoted above.”? Seems like sloppy/careless scholarship on your behalf?

    Also, this mystery and natural phenomena has nothing to do with multiverses nor strings, so I’m not sure it is appropriate to this thread?

    Dr. E :)

  • Charlie

    Boy, there sure is a lot of appealing to higher authority here. I do wonder if Einstein, Feynman and others would really appreciate being used this way, or if they spent much time on these kind of appeals in their time.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Charlie,

    I am not appealing to Sean Carroll’s authority nor the dominant authority of the multiversers/string theorists who neglect physical reality alongside logic and reason, so as to hawk magazines.

    “In questions of science, the authority of thousands of string theorists is not worth the humble reasoning of one individual.[viii]” –Galileo

    I am appealing to the authority of physical reality and those who exalted it in science, as well as to the authority of logic and reason.

    What do you have against the higher authority of the world’s greatest scientists and physical reality, and the authority of logic and reason?

    I mean whose authority do you think we should appeal to?

    Do you not like logic and reason? Do you have something against the Great Scientists? Do you not like physical reality?

    What is driving you?

    Who/what must we all appeal to and kneel before in your multiverse?

  • Joel Rice

    38 Dr Elliot … I did not say that they had anything to say about octonions or any resolution of the Generation mystery – only that they regard generations as an outstanding mystery, and leave it at that. My point is simply that if Generations are resolved without resorting to supersymmetry then the rationale for strings falls apart, and then where is the rationale for Multiverse ? I offer an algebraically based argument to think we do not need supersymmetry or strings, and neither does Mother Nature. The whole point of strings was to define particles. It appears that the quest has led them into a swamp. It seems useful to have a different perspective from which to consider whether strings are ‘the only game in town’. Back in the 80s I thought strings would be a fad, and that Glashow’s remarks in Physics Today ( i think) would have dampened enthusiasm, but apparently not. I think it appropriate to argue that there is no multiverse, in a thread that claims there is.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Thanks Joel!

    I better understand what you are saying now! I agree!

    Simply put, there is no physical evidence for multiverses nor strings, and thus they are not science, in the eyes of all the great physicists, as seen in all the quotes above, as well as in my upcoming book: Why String Theory, M-Theory, LQG, Multiverses, and Parallel Universes are NOT Physics, and why Moving Dimensions Theory (MDT’s dx4/dt=ic) IS

    Thanks again Joel,

    Best,

    Dr. E :)

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Charlie,

    You write, “Boy, there sure is a lot of appealing to higher authority here. I do wonder if Einstein, Feynman and others would really appreciate being used this way, or if they spent much time on these kind of appeals in their time.”

    How do you think Einstein, Feynman, and others would prefer to be used? Or should we ignore them? What are you saying exactly? That we should only appeal to “lower authorities” such as Sean Carroll and the physics-free, non-empirical, unscientific, groupthink-hype, illogical, non-physical mutiverse/string theory, as opposed to the higher authority of Nobel Laureate physicists, physical reality, logic, and reason?

    Einstein humbly appealed to the greatness of Newton, calling him “the Master.” Einstein also humbly appealed to the greatness of Galileo and Copernicus:

    “But before mankind could be ripe for a science which takes in the whole of reality, a second fundamental truth was needed, which only became common property among philosophers with the advent of Kepler and Galileo. Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and ends in it. Propositions arrived at by purely logical means are completely empty as regards reality. Because Galileo saw this, and particularly because he drummed it into the scientific world, he is the father of modern physics–indeed, of modern science altogether.” -Albert Einstein, Ideas and Opinions. MDT’s dx4/dt=ic honors Galileo and Einstein, as it both “starts and ends” in experience!

    “Once it was recognised that the earth was not the center of the world, but only one of the smaller planets, the illusion of the central significance of man himself became untenable. Hence, Nicolaus Copernicus, through his work and the greatness of his personality, taught man to be honest.” -Albert Einstein, Message on the 410th Anniversary of the Death of Copernicus, 1953

    Do you think it was a sin for Einstein to appeal to the greatness of Copernicus, Newton, Faraday, Maxwell, and Galileo, as well as to logic, reason, and physical reality?

    Who, in your view, should have Einstein appealed to?

  • Charlie

    I’m speaking from the point of view of a scientist in an unrelated field. Hence, a lot of ignorance. That is (and should be) a position of weakness in any scientific debate. Nevertheless, the style of argument presented here does not seem likely to sway many of the young folks thinking of entering the field. You should make your case, of course, using logic and evidence (what else do we have?), and some appeal to the old guard is fine.

    If, indeed, it is true that no part of string theory can be tested under any context (a point that seems to be somewhat uncertain at this time, if I understand correctly), then it will die a natural death, or become an interesting branch of math, which isn’t so bad. This process will be hastened greatly if someone provides an alternative that doesn’t suffer the same problem. Though I’m working in another field entirely, I have absolute confidence that physicists will jump all over such an alternative, if it is provided. (Until this time, science will fumble on in a process that is not nearly as “neat” as many would like it to be…)

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Thanks Charlie,

    You write, “I’m speaking from the point of view of a scientist in an unrelated field. Hence, a lot of ignorance. That is (and should be) a position of weakness in any scientific debate.”

    So, as you are ignorant in the realm of physics, why should we hold your authority over the authority of Newton, Einstein, Galileo, Feynman, Copernicus, Nobel Laureate physicists, and physical reality?

    I’m not sure why you attacked the authority of logic, reason, the Great Physicists, and physical reality, as truly, it are these entities which attract young physicists to the field–not the purely political non-physics of the multiverse and string theory. What motivated your attack?

    Again–that would be great if you could please answer my below questions:

    You write, “Boy, there sure is a lot of appealing to higher authority here. I do wonder if Einstein, Feynman and others would really appreciate being used this way, or if they spent much time on these kind of appeals in their time.”

    How do you think Einstein, Feynman, and others would prefer to be used? Or should we ignore them? What are you saying exactly? That we should only appeal to “lower authorities” such as Sean Carroll and the physics-free, non-empirical, unscientific, groupthink-hype, illogical, non-physical mutiverse/string theory, as opposed to the higher authority of Nobel Laureate physicists, physical reality, logic, and reason?

    Einstein humbly appealed to the greatness of Newton, calling him “the Master.” Einstein also humbly appealed to the greatness of Galileo and Copernicus:

    “But before mankind could be ripe for a science which takes in the whole of reality, a second fundamental truth was needed, which only became common property among philosophers with the advent of Kepler and Galileo. Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and ends in it. Propositions arrived at by purely logical means are completely empty as regards reality. Because Galileo saw this, and particularly because he drummed it into the scientific world, he is the father of modern physics–indeed, of modern science altogether.” -Albert Einstein, Ideas and Opinions. MDT’s dx4/dt=ic honors Galileo and Einstein, as it both “starts and ends” in experience!

    “Once it was recognised that the earth was not the center of the world, but only one of the smaller planets, the illusion of the central significance of man himself became untenable. Hence, Nicolaus Copernicus, through his work and the greatness of his personality, taught man to be honest.” -Albert Einstein, Message on the 410th Anniversary of the Death of Copernicus, 1953

    Do you think it was a sin for Einstein to appeal to the greatness of Copernicus, Newton, Faraday, Maxwell, and Galileo, as well as to logic, reason, and physical reality?
    Who, in your view, should have Einstein appealed to?

    Thanks in advance for answering these questions, Charlie. We’re just trying to understand who told you/taught you to attack the Great Physicists, science, physical reality, Nobel Laureates, logic, and reason, so as to bolster the non-science, non-reality of multiverses and string theory, so that we can perhaps help. :)

    Whose authority are you appealing to in your attack? By whose authority are you attacking the authority of the Great Physicists, science, physical reality, Nobel Laureates, logic, and reason?

    Best,

    Dr. E :)

  • http://wavefunction.fieldofscience.com Curious Wavefunction

    @Somebody: What do you suggest we do? Call off curiosity and not try to fully figure out the half-cooked candidate (i.e., string theory) that seems to be both very tantalizing and very infuriating at the same time?

    Of course not. But at the same time there’s no use touting it as the best candidate for a TOE. Instead treat it for what it is; a set of mathematically elegant ideas that may or may not have any connection to reality (and by “reality” I mean stringent experimental testing). The problem seems to be the almost evangelical enthusiasm with which practitioners of string theory seem to pitch their discipline, as if it’s a done deal simply waiting for experiment to catch up. In science experiment takes precedence over everything else and the standards of science (call them cruel if you will) cannot consider ideas unsupported by experimental evidence as anything more than interesting speculation, no matter how mathematically elegant. Any intelligent person can see that it is unreasonable at the very least to cheerfully pitch a theory that is not supported by a shred of hard experiment. Of course nobody should stop you from working on string theory but it should be treated as no more than an interesting idea, and certainly not one that should dictate faculty appointments or media coverage of physics.

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Thanks Curious Wavefunction,

    You write, ” Of course nobody should stop you from working on string theory but it should be treated as no more than an elegant and interesting idea.”

    I was not aware that that String Theory was elegant? With no equations, and literally billions upon billions of solutions, and no concrete formalisms, where is the elegance?

    Even Michio Kaku admits ST lacks elegance: The great irony of string theory, however, is that the theory itself is not unified. . . For a theory that makes the claim of providing a unifying framework for all physical laws, it is the supreme irony that the theory itself appears so disunited!![xlvi] Introduction to Superstrings & M-Theory –Kaku

    Nobel Laureate Physicist: “Actually, I would not even be prepared to call string theory a “theory” rather a “model” or not even that: just a hunch. After all, a theory should come together with instructions on how to deal with it to identify the things one wishes to describe, in our case the elementary particles, and one should, at least in principle, be able to formulate the rules for calculating the properties of these particles, and how to make new predictions for them. Imagine that I give you a chair, while explaining that the legs are still missing, and that the seat, back and armrest will perhaps be delivered soon; whatever I did give you, can I still call it a chair?[xlii]” –‘t Hooft, Nobel Laureate

    “With all the years that String Theory has been studied, no one has ever found a single defining equation! The number at present count is zero. We know neither what the fundamental equations of the theory are or even if it has any.” (p. 204) –The Cosmic Landscape, Leonard Susskind

    Nobel Laureate Physicist: If Einstein were alive today, he would be horrified at this state of affairs. He would upbraid the profession for allowing this mess to develop and fly into a blind rage over the transformation of his beautiful creations into ideologies and the resulting proliferation of logical inconsistencies. Einstein was an artist and a scholar but above all he was a revolutionary. His approach to physics might be summarized as hypothesizing minimally. Never arguing with experiment, demanding total logical consistency, and mistrusting unsubstantiated beliefs. The unsubstantial belief of his day was ether, or more precisely the naïve version of ether that preceded relativity. The unsubstantiated belief of our day is relativity itself. It would be perfectly in character for him to reexamine the facts, toss them over in his mind, and conclude that his beloved principle of relativity was not fundamental at all but emergent (emergent from MDT!) . . . It would mean that the fabric of space-time was not simply the stage on which life played out but an organizational phenomenon, and that there might be something beyond.[xlvii] (MDT!) -A Different Universe, Laughlin, Nobel Laureate

    Nobel Laureate Physicist: [String Theory] has no practical utility, however, other than to sustain the myth of the ultimate theory. There is no experimental evidence for the existence of strings in nature, nor does the special mathematics of string theory enable known experimental behavior to be calculated or predicted more easily. . . String theory is, in fact, a textbook case of Deceitful Turkey, a beautiful set of ideas that will always remain just barely out of reach. Far from a wonderful technological hope for a greater tomorrow, it is instead the tragic consequence of an obsolete belief system-in which emergence plays no role and dark law does not exist.[xlviii] —A Different Universe, Laughlin

  • Wil

    Sean Carroll’s article in Discover draws an analogy between Giordano Bruni’s multi-sun and multi-planet cosmology (derived on philosophical grounds) and today’s multiverse cosmology (derived from string theory plus inflation). Could not one also choose as an analogy the world view of the geographers who, a century before Bruni, constructed maps of the earth that showed all the explored territory more or less accurately and, in the “unexplored” parts labeled simply “terra incognita”, added the annotations “Here there be dragons”? After all, they were led to that conclusion by the “theory of dragons” which posited that dragons exist, and since none were to be found in the explored territory, then they must reside in the unseen parts. This “theory of dragons” was not unreasonable; after all, snakes were of course well understood, and it is easy to extrapolate from that evidence to deduce what a much larger serpent would be like, and surely a much smaller number of hypothetical species than 10^500 would suffice for some of them to assume dragon-sized dimensions. Surely the existence of snakes (to say nothing of the very large reptilian bones that were routinely dug up in China) is much better experimental evidence for the existence of dragons than can has been found to date for the existence of strings. So is the multiverse akin to Bruni’s cosmology (which turned out to be right, but which had no actual experimental data underlying it), or is it more nearly akin to a map of spacetime that labels the “pocket universes incognita” with the annotation “Here there be strings”?

  • http://herosjourneyphysics.wordpress.com Dr. Elliot McGucken

    Dear Wil,

    The problem with basing anything on String “Theory,” is that String “Theory” has no equations and it neither begins nor ends in physical reality, as nobody has ever seen a string, and there is no way to test for one. String Theory is *not* a physical theory. Basing the multiverse on String Theory is like basing a phantasm upon a falsehood that is founded upon the shifting sands of Sean Carrollonian fried-egg fantasies, which in turn are found only within the non-physical M-theory multiverse fallacy, where nobody knows what the M stands for.

    “With all the years that String Theory has been studied, no one has ever found a single defining equation! The number at present count is zero. We know neither what the fundamental equations of the theory are or even if it has any.” (p. 204) –The Cosmic Landscape, Leonard Susskind

    “But before mankind could be ripe for a science which takes in the whole of reality, a second fundamental truth was needed, which only became common property among philosophers with the advent of Kepler and Galileo. Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and ends in it. (Yes! Moving dimensions theory begins in experience–the double slit experiment, entropy, relativity, nonlocality, time and all it arrows and asymmetries, and it ends in experience, by providing a physical model predicting all these entities!) Propositions arrived at by purely logical means (String theory, loop quantum gravity (which might not even use logic)) are completely empty as regards reality. Because Galileo saw this, and particularly because he drummed it into the scientific world, he is the father of modern physics—indeed, of modern science altogether. -Einstein[i], Ideas and Opinions

    Einstein’s above quote is quite prominent in its complete absence from today’s leading “physics” books and blogs, as are many of the Greats’ quotes below, wherein the Greats define what science is and ought to be–wherein they define what science has ever been. Einstein states that, “all knowledge of reality starts from experience and ends in it,” and a glaring problem with string theory is that nobody has ever seen a tiny little string (and thus ST does not begin in experience), nor measured one, nor conceived of an experiment that would allow us to see strings (and thus ST does not, and cannot end in experience either). Nor has anyone ever seen a multiverse, nor come up with a way of measuring or detecting multiverses. Nor has anyone ever come across any of the tiny, little loops of loop quantum gravity, nor any way to detect nor measure tiny little loops. So it is that all these non-theories begin in the imagination, and end in it. One will hear their proponents singing of the great beauty of their theories, but then, when one asks them for the fundamental equation, they are unable to produce any. Indeed, it turns out there are millions of equivalent non-theories with various amounts of dimensions, with ever-changing math which never adds up to predict anything we see in physical reality. In that sense, the theories are actually quite ugly.

  • Steve Turrentine

    People here should be aware of the fact that this fakey “Dr.” McGucken” is a nutball that also uses other names & is the ostensible author of the crackpot “moving dimensions” theory, a well-known quack theory. As can be seen by his entries here, he has almost nothing of his own to say, but merely quotes various other physicists is a lame attempt to bolster his crackpot ideas. Everything he’s said here can be ignored.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    I agree. Let’s ignore “Dr. McGucken” from now on.

  • Craig

    How does thinking about the multiverse effect the types of experiments we do at places like the LHC? How does it effect the way we explore the boundaries of physics? It seems like we hear a lot about things like wormholes because they capture the public’s interest, but my understanding is that they don’t actually exist. Is the multiverse like that or does the possibility give us hints about what types of experiments to try or about how to explain experiments that have already been done?

  • Charlie

    Full confession: I found this website during a late night web surfing spree that started with Plasma Cosmology. One can enjoy crackpottery to a certain limit, as long as it isn’t hurtful like anti-vaxxer conspiracy. However, it’s easy to recognize (even way outside of one’s own research field) by many symptoms. The first is an utter lack of ability, or perhaps interest, in actual communication.

  • curious

    Sean Carroll, have you ever considered the possibility that string/M-theory is physically wrong? SUSY is not a symmetry realized in nature, and space-time is only 4-dimensional., and GUT theories are all unrealized in nature .

  • somebody

    “Sean Carroll, have you ever considered the possibility that string/M-theory is physically wrong? SUSY is not a symmetry realized in nature, and space-time is only 4-dimensional., and GUT theories are all unrealized in nature.”

    No. He has never considered that posibility. Like EVER. Until he ran into this insightful blog comment, that is. Thank you.

    Shrug.

    PS: Sorry about the sarcasm, but it was irresistible to me.

    To Curious Wavefunction: string theory might be over-sold, but it IS also a pretty exciting set of ideas. Nothing wrong in letting the public in on it. Afterall, public exposure of ideas is what lets people have the illusion that they are entitled to have an opinion about things they only have a foggy awareness of: like deciding what is a promising direction of research. :) There is nothing like the sweet smell of napalm in the morning.

    In any event, the public relations aspect might be important sociologically, but that was not my concern in my post. I was talking about where the science stood. And on that you seem to agree with me. Finally: I have always felt that the string theorists are usually more aware of the promises and limitations of their field than anyone else – whatever the public image of the subject might be. There is a touch of irony most (but not all) of us feel when we make jokes about string theory.

    All of these comments are making me look arrogant and unpopular, but they are relevant and true, so they need to be stated.

  • curious

    somebody: to the lay public, is there anything in Sean’s article in Discover magazine, or in popular books by Kaku and Green and Randall or Hawking, that would suggest that string theory is not on the same footing as QFT and GR?

  • Charlie

    @curious Says,

    As a layperson (in this area, anyway), I can say that probably every presentation I’ve seen about ST is packed full of caveats about testability. Sean’s article is more directly about Multiverse, and he provides appropriate caveats: “But the multiverse might be impossible to test directly. Even if such a theory were true, the worry goes, how would we ever know? Is it scientific to even talk about it?” (You have to consider the audience and length restrictions in deciding if this is sufficient, but I think it is.)

    This point is also not understood by the public (and internet trolls): “These concerns stem from an overly simple demarcation between science and nonscience. Science depends on being able to observe something, but not necessarily everything, predicted by a theory.” I can say in studies of evolution (where I am not a layperson, and the theory is on much more solid footing than ST) that the public expectation is that we have to explain everything, perfectly, or else the theory is wrong. The theory tells me a lot of what to expect when we sequence a new animal’s genome. Nevertheless, when a scientist says “this phenomenon is contrary to expectation from evolution”, then the public and the media smell blood in the water (while a biologist sees new exciting science).

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  • http://www.math.columbia.edu/~woit/blog Peter Woit

    Phil (#19),

    I turned off comments about this on my blog not because of the commenters (few if any) who disagree with me about the multiverse, but because of those who agree with me (numerous). This topic attracts comments empty of any intellectual comment, from both sides, and I just didn’t want to deal with them. One reason for this is that I’m pretty tired of the topic, nothing much has changed since Sean started on this promotional campaign even before Cosmic Variance was around:

    http://www.math.columbia.edu/~woit/wordpress/?p=94

    And no, string theory doesn’t make any generic predictions at ANY energy scale. Specific perturbative string theory vacua yes, but there’s an infinity of them, and the non-perturbative ones, which typically you can’t say much about at all. As “somebody” notes, string theorists do know this. They just try and ignore it when they’re writing for the public…

  • Phil

    Peter Woit, #59,

    If you’re so tired of the topic, why do you keep posting about it?

    Doesn’t string theory at least predict extra dimensions to emerge at the Planck scale? Isn’t there any “stringy” signature that can be experimentally differentiated from point-particle behavior at the Planck scale?

    And do you agree with the notion that there are many many quantum field theories, just as there are many many string theories, and that experiment is needed to find the correct quantum field theory that describes our low energy world? Only it’s much more difficult to build string theory vacua that resembles our own low energy universe, but there is no reason why, in principle, it cannot be done. So how is this situation different from QFT?

  • curious

    re: Charlie Says:

    “But the multiverse might be impossible to test directly. Even if such a theory were true, the worry goes, how would we ever know? Is it scientific to even talk about it?” (You have to consider the audience and length restrictions in deciding if this is sufficient, but I think it is.)

    Would this be sufficient if we consider a research program based on intelligent design?

  • somebody

    Woit is again thoroughly missing the point when he says string theory doesn’t make any predictions at ANY energy scale. Or trying to be misleading? His posts in the past make me cynical.

    It doesn’t matter what are all the solutions of string theory or how big the landscape is. Some of the solutions might not even have spacetime phases. But we know -by experiment, ha!- that WE live in a locally flat spacetime where scattering is possible and in such a phase stringiness MUST manifest at some scale below the Planck scale. Details depend on the compactification, but the generic prediction is enough as a smoking gun signature of stringiness (exponential as opposed to power law fall-offs in cross sections with momenta).

    I do expect the target to move momentarily, but ‘nuf said from my side.

  • Observer

    Ive long since abandoned any attempts to explain Peter Woit’s misleading and/or false statements by anything besides a dishonest attempt to sell books and promote himself.

    I think the word “multiverse” can be very troublesome. To me the only sensible definition for the word is the space of possible histories that might be postulated to exist under the many worlds interpretation, which is by definition a metaphysical, untestable idea (not to suggest that we shouldn’t wonder about it). If instead it means something that is connected with our world in any direct way, then clearly that is part of the same “universe”, by definition.

    Sean is right to urge caution in declaring a class of questions unscientific. Something is only unscientific if it cannot be decided *in principle*, and many questions are very hard and unlikely to be answered, but not unanswerable in principle. Woit is now creating an awful lot of fog by dishonestly trying to confuse the truly metaphysical questions with the hard, scientific questions of whether string theory is correct, and if so what is the true structure of our world…

  • Phil

    Isn’t it true that theorists haven’t been able to use QCD to calculate the proton’s mass? From my understanding, this is due to the failure of perturbative QCD and only non-perturbative QCD (which we don’t know very well) can allow us to calculate the proton’s mass. Isn’t this similar to our lack of knowledge of string theory non-perturbatively?

    Maybe if we understand string theory non-perturbatively, we will be able to find our low energy universe in the theory and rule out the rest of the landscape? But we don’t know if such a thing is possible, hence the continuing research in string theory.

    Also, one can argue that string theory is NOT a TOE because it is only a perturbative theory of strings that postulates what the degrees of freedom are beyond the standard model and towards the Planck scale. Perhaps M-theory, or whatever the nonperturbative formulation of string theory is, is the real TOE.

    If QCD is the theory of the strong interactions, why haven’t we been able to use the theory to calculate the proton mass? Because we don’t understand the theory very well non-perturbatively. Perturbative QCD, like perturbative string theory, cannot explain everything (i.e the proton mass), but a more fundamental formulation (i.e. non-perturbative QCD) can. The same may be true with string theory.

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    Ah, this brings back the good old days of spending huge amounts of my time trying to answer anonymous people devoted to characterizing me as a money-grubbing dishonest guy who had no idea what he was talking about. Fun times…

    The best response to this is to just refer people to the old discussions, since they’re still on-line. Try for instance

    http://blogs.discovermagazine.com/cosmicvariance/2005/07/21/two-cheers-for-string-theory/

    and note that in comment 56 Sean agrees with me that the argument about string scattering amplitudes being a definitive prediction of string theory doesn’t work. There’s this thing called M-theory….

  • Phil

    Peter, #65

    There are many quantum field theories possible, corresponding to the many possible choices one can make for the underlying gauge groups. Similarly, there are many possible perturbative string theories, corresponding to the many possible ways of compactifying C-Y manifolds, etc. So what is the difference between these two?

    The only difference I see is that we are able to perform experiments that show us the way towards the gauge groups of the standard model, but we do not yet have the technology to conduct experiments that show us what physics looks like far beyond the standard model or near the Planck scale. When string theorists get better at building stringy models that match the standard model they will have many models that not only contain the standard model, but also have different possibilities for what lies beyond the standard model and near the Planck scale. When or if our technology improves to the point which allows us to conduct much higher energy experiments, nature will guide us to the correct model, just like how nature guided us to the correct SU(3)XSU(2)XU(1) quantum field theory after we performed lots of particle physics experiments.

    Do you agree with the above?

    If it is shown that no stringy model contains the standard model (which hasn’t been done yet) or the results of beyond standard model experiment, then string theory will be shown to be wrong. If such a thing is not shown, then string theorists will keep on looking.

  • Arun

    The idea of atoms was proposed over 2000 years ago. It had a ” testable” prediction, namely, that matter cannot be divided indefinitely. Nevertheless, in the absence of any viable experimental method to test it, the atomic hypothesis could hardly be called science, till relatively recently, historically speaking. Perhaps string theory’s prospects are a little better. Perhaps.

  • Phil

    Peter,

    You say QFT is predictive. Does QFT predict the SU(3) X SU(2) X U(1) group structure as the one that describes our world? No. Experiments were needed to elucidate this fact about our low energy world. Likewise, experiments are needed to elucidate the correct compactification for the extra dimensions, assuming extra dimensions and string theory describe our world. Again, experiments are needed to determine whether or not string theory and compactified extra dimensions describe our world, just as experiments were necessary to show us that group theory and the formalism of quantum field theory describe our world.

    So, in that sense, QFT is just as unpredictive as perturbative string theory.

    Do you agree with this? Why or why not?

  • J

    Phil,

    I completely agree, and this is a point that I do not think is made enough. Allow me to elaborate a little on your very nice point.

    String theory and QFT are both frameworks for physics which are broad and apply in many scenarios.

    A string vacuum or a quantum field theory are examples within their respective frameworks. Mathematical data is needed to specify both, and each makes predictions. Each string vacuum, for example, tells you unambiguously the gauge symmetry and matter content of the theory. If it’s SU(18) with a whole bunch of fundamentals, this string vacuum has made a prediction and it is not our world.

    Other vacua may look a whole lot more like the real world. In my view, the problem isn’t whether a string vacuum makes predictions, it’s that it’s extremely difficult or impossible to determine which vacuum in the landscape is ours.

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  • http://arunsmusings.blogspot.com Arun

    When Newton gave us his 3 laws of motion, they were also just a framework for dynamics. The laws of force had to be specified separately. Newton had a law of force for gravitation, and perhaps Hooke’s law. I suppose he did not even attempt an explanation for the gravitational constant. Yet we call his laws predictive, because they could be applied to phenomena.

    The same holds for quantum field theory, which is a productive framework, in exactly the same sense as Newton’s laws. The contrast of these two frameworks with string theory is stark.

    I also think that the philosophy of science has undergone a huge change, not necessarily for the better. E.g., Mendeleev found the periodic table of elements in 1869 (in my analogy, akin to the Standard Model of particles). It provided a firm indication of an underlying structure, which however, was not figured out for decades. I think Moseley’s law and Bohr’s atomic model, both dating from 1913 were essential ingredients. The span of time of the Standard Model (say 1968-2011) is still less than that of the mysterious periodic table of elements (minimally, 1869-1913). But the chemists didn’t fall into anthropic reasoning or decide that the atomic weights/numbers arose from a landscape. Perhaps it is because they continued to have useful work to do, unlike the particle physicists of today?

    In retrospect, during any particular era of the history of science, there were certain questions that were fruitful to ask, and a great many other questions that led nowhere – though they may have been answered in some future time. The first hard problem in the practice of science, in my opinion, is figuring out which the fruitful questions are. I think if we see ourselves flying off the rails, it may be a sign that we are not asking the questions that are right for our era.

  • Marty

    Phil (#66, #68),

    Hopefully I’m paraphrasing your point correctly. Given that both QFT and string theory can both be thought of as general frameworks that are compatible with a huge number of possible theories/solutions, observational input is needed to choose the one(s) that is/are physically relevant, why should ST be regarded as lacking predictivity, even though QFT is similarly non-predictive without the experimental input that singles out the physically correct QFTs?

    I think it comes down to two words: track record. Consider QED, the most accurate physical theory ever found. As you imply, empirical evidence led to its development, and in fact was instrumental in developing the QFT framework in the first place. Given the QED Lagrangian, the QFT framework makes a large number of very accurate predictions which people take as evidence for the correctness of QFT more generally. This success has been followed by finding QFTs for the standard model and QCD, giving further evidence that QFT is a physically correct framework.

    In fact, it is irrelevant whether experiments were crucial to finding the correct QFTs — once they were found, they made a huge number of accurate predictions that were in no way implied by the experimental input that originally led to them. That’s real predictivity.

    Now consider string theory. One can argue that, like choosing physically relevant QFTs the space of all possible QFTs, experimental input can similarly help choose the physically relevant vacua from the space of all stringy vacua; hence. And that is true, but does it justify putting ST and QFT on similar footing? For now, I’d rather disregard arguments along the lines that there are so many candidate vacua (e.g., the 10^100 to 10^500 that get bandied about) that if you have found one vacuum that matches our world there may be a really huge number that also match our world within the precision of our experiments so that there is no way to operationally choose the correct vacuum and predict new results that weren’t used to select the ‘correct’ vacuum in the first place. That argument is probably beside the point of your question. The key thing is simply that not even one vacuum has been found yet that leads to something like our world, so it is not possible to use the string theory framework to take that vacuum and make predictions that can be checked against new experiments. That means that string theory has not been ‘battle tested,’ in very stark contrast to QFT which has been battle tested to an extraordinary degree.

    Note that this comparison of QFT and ST is purely in terms of earned credibility. String theory can make many claims about explanatory power, but it has no track record at all in making accurate predictions. String theory may ‘really’ be the correct theory of nature in a philosophical sense, and the argument I gave won’t change at all. It’s like going to a well-respected doctor with a long track record of dealing with an ailment you have, versus going to a new doctor who uses flashy advertising in the local newspaper but who has no experience with your ailment: which would you choose?

  • J

    Hi Arun and Marty,

    I have to disagree with you both a bit, though perhaps I agree a little more with Marty.

    Arun: you missed my point. Any given quantum field theory does in fact make predictions, as you point out, in analogy with Newton’s laws. Quantum field theory as a whole, which is a framework, not a theory, does not. Similarly – though you think the contrast to string theory is stark (it is not) – any given string vacuum makes predictions: it gives rise to a field theory at low energies which is often a gauge theory. Furthermore, in some sense it is MORE predictive than field theory: it predicts the gauge symmetry and representation content of the theory. As I stated, the problem isn’t predictivity of an individual vacuum, it’s separating our world out from the landscape of possibilities.

    Marty: You’re point is a better one, I think. One necessary correction is that vacua have certainly been found that look something like our world, in many different contexts in string theory. See the recent work on F-theory GUTs, or slightly older work in type II orientifold compactifications or the heterotic string on orbifolds or smooth Calabi-Yau manifolds with holomorphic vector bundles. A lot of the posts in this thread come across as rants (not yours, though) from people who seem out of touch with the current status of string vacua for the purposes of unification. It’s not that there aren’t problems – there are – it’s just that they’re not the ones a lot of people are ranting about. Just thought I’d mention this correction.

    You’re right to bring up the effectiveness of particular effective field theories in describing the world, in particular the importance of experiment: the experiments told us what terms to write down in the standard model Lagrangian. The issue isn’t quite as serious as you make it though, since string vacua contain field theories at low energies. If I may build on your point a little – the problem is that it’s very hard to distinguish field theory from string theory at low energies, so given new experimental input (help, LHC!) it would be difficult to say whether it’s string theory or just field theory. The typical things distinguishing between field theory and string theory – e.g. Kaluza-Klein modes or stringy excitations – typically come in at high scales. So I agree, touching low-energy experiments and distinguishing between FT and ST is difficult.

    One interesting point, to me, at least, that should be mentioned. In FT, gauge theory is an input. The experiments told us what terms to put into our Lagrangian, and it turns out they’re gauge invariant. That’s a lot of structure – gauge theory! – that has been put into FT by hand. In string theory, this beautiful structure is output of the framework, not input.

    J

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    “Furthermore, in some sense it is MORE predictive than field theory”

    Well, there certainly is one huge difference between string theory and QFT, the level of hype…

    One can try and make a serious argument that string theory is still not understood well-enough, that future fundamental progress in the subject will turn things around and lead to something that is predictive and competitive with QFT. But, claiming now that string theory is in the same situation or “MORE predictive” than the most successful theory ever developed by physicists is to be very, very far gone into the realm of sophistry.

  • Cliff/observer

    I appreciate J’s point. Its one I often try to make, namely that according to Woit’s criteria, quantum field theory would itself be “unscientific” or “failed” or whatever if you imagined an analogous scenario where we had developed the general framework but had not figured out a way to determine the relevant gauge groups, etc.

    But this obviously isn’t an A to B comparison. Besides its proven success, QFT operates at energy scales directly amenable to tests at particle accelerators. The main reason why I often find it hard to imagine that Woit is genuinely honest is that every serious scientist that looks at this knows that the experimental difficulties are guaranteed by the Planck scale. Anyone who promotes the idea that extreme difficulties in finding potent experiments isn’t generic to the entire project of understanding quantum gravity has either dubious honesty or dubious physics knowledge in my opinion.

    Maybe we will find some potent evidence in coming years one way or the other, maybe not. But I think its ridiculous to simply throw stones at the entire project of understanding quantum gravity, and its ridiculous to expect that physicists just abandon the most promising framework for attaining that understanding without much more concrete, convincing reasons (ideally in the format of scientific papers rather than in the popular blogosphere). I dont think there is any rational reason to expect that all answers to the ultimate theory of quantum gravity could be determined without Planck-scale scattering data, but that is apparently the standard by which string theory has “failed”. Its quite simply BS.

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    Cliff/observer/whoever you are,

    As for your accusations of dishonesty, “every serious scientist that looks at this knows that the experimental difficulties are guaranteed by the Planck scale.” is just complete nonsense. I have no idea who you are, but you clearly don’t spend much time talking to serious scientists in this field, most of whom are well aware that string theory’s problems as a unified theory go far beyond not having data from the Planck scale that would pick out a Calabi-Yau. It’s just not true that the theory is well understood at Planck distances.

    The problem with string theory is a problem about unification. It is supposed to not just quantize gravity, but explain the Standard model and particle physics at ALL energies. This simply doesn’t work now, at any energy.

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    As an addendum, anyone who thinks that there’s a definite prediction about how string theory behaves at the Planck scale might want to consider reading the more recent blog post here from Tom Banks.

  • Cliff

    Well Mr Woit, Im pretty much just stating my assessment. Im sure your overall attitude on string theory is just what it appears, but over the years I’ve seen way too many instances of you playing fast and loose with facts, which you seem not to know very well. Among other things you seem to like to deliberately create confusion between the assessments of the string community and the media “hype”, which makes for an all-too-easily distorted picture. I have a hard time imagining someone whose primary devotion is to honest education of the public engaging in this sort of behavior. Overall, a person who reads your blog is apt to get the impression that string theory is one giant blob of undetermined nonsense, as if there is no understanding whatsoever. Im not what you’d call an expert on string theory but I know a bit, and I know enough to know that the image that comes out of your blog is a long way from what the experts understand, as seems to become all the more more clear when I see you interacting with them…

    I think you must have understood what my sentence meant better than your response would indicate. As long as we agree that the Planck scale is likely to be important for quantum gravity, then it follows that any theory of quantum gravity might be called “unscientific” based on a sufficiently religious definition of what science is. Even though you were answering a different issue, I think your response is silly. Im well aware that a complete definition of string theory is lacking, but we all know that certain sectors and limits are well understood. Your ambitious claim that string theory makes “no predictions” would certainly be interesting if you could prove it. Are you claiming some special knowledge of the complete picture? Or are you just taking the liberty of assuming that a very large number of solutions gives license to do anything?

    Anyway, I think you’re setting up an unreasonable standard for what we have the right to expect. There’s no reason why the most ambitious project in science should have an easy answer. There is no reason to think that without very high-energy data we would have anything more than a very broad set of consistency criteria. And since such a set of consistency criteria appears to be extremely rare, maybe even unique, I don’t see any reason why these human-centered demands should be deterring us from investigating these very important questions. I don’t believe what you say can be translated into any *physical* argument against the validity of string theory.

    I dont know whats particularly relevant about me. Im a physics student who works damn hard to understand QFT and some string theory. Ive surely made my share of mistakes, but Im not the one presuming to call into question a large part of the mainstream of the high energy physics community (including their honesty, which you don’t seem to much care for yourself).

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    Cliff,

    You make it very clear that you don’t actually know very much about this subject, you’re just for some reason deeply offended that I publicly make arguments that conflict with some of the hype you’ve been exposed to. Before being so sure that this hype represents the mainstream, I suggest you pick a good research university and try knocking on some faculty office doors, asking them what they think of string theory unification and the “multiverse”. You might learn that the mainstream view among professionals who know something is rather different than what you think it is.

  • Cliff

    Mr Woit, you’ll surely be surprised to learn that Im constantly seeking out viewpoints from all kinds of physicists, most especially those who disagree with me in their assessment, but I always found that quantitative arguments to be much more meaningful than slogans. In fact Im quite grateful whenever someone can provide me with any substantive logic leading me to revise my assessment. I noticed you’ve declined to provide any. Its not news to me that there are many researchers who differ.

    Some physicists whom I respect can, and have, caused me to adjust my views somewhat based on less concrete explanations of how they see things differently, however this only happens if he or she has a unmistakable record of valuing the truth above all else. A person with an agenda has very little chance to influence me without solid arguments. Sorry but my assessment is that your main project in life seems to be to influence popular perceptions of physics in the PR arena, and Ive yet to see any convincing evidence that you’re capable of deviating from that pattern.

    Anyway my assessment is based in large part on a few textbooks and countless papers. Maybe its all still what you consider hype. But Im fairly certain that if there ever exists any rigorous arguments why all of this work must be thrown out the window, I will notice it.

  • J

    Peter and Cliff,

    No accusations of dishonesty out of me towards either of you, for the record. I’m just trying to have a conversation :)

    Peter, I don’t disagree with you that there has been a lot of string hype and that it has been overstated and huge promises have been made that should not have been made. But you still didn’t really deal with the nuances of my statements, instead you just changed to a statement about hype and then made statements about field theory that showed you missed my point.

    As you well know, quantum field theory is a framework for physics that is very good, due to the notion of effective field theory, at describing a wide variety of systems at low energies. For each system it might describe, there is a different quantum field theory. My point is that “a quantum field theory” (e.g., the standard model) is a theory, but “quantum field theory” is a framework. (I know you know all this, I’m just trying to make my point clear, I really don’t mean to sound pedestrian!)

    Similarly, note that I tried to be very careful to denote the difference between a string vacuum and “string theory” as a whole, though many vacua could exist as local minima on a connected moduli space. One of my points was that, in a given string vacuum, the gauge theory and matter content of the theory are completely unambiguous, (at least in all parts of the landscape I know), assuming you know how to do the relevant computations. Most vacua give some sort of gauge symmetry and particle content, and this is one of the great successes of string theory as a framework (and a specific prediction, accessible at low energies, of each individual string vacuum) where quantum field theory fails: gauge symmetry is output in string theory, it is input in quantum field theory.

    What I mean is that you can write down a gauge invariant Lagrangian if you want to, and in particular you should because experiment tells us there is gauge symmetry in the world. But ultimately it’s dependent on the fact that you wrote down your Lagrangian in a particular way. On the other hand, simple considerations of the quantization of a fundamental object – a string – naturally leads to gauge theory, as output of the theory. If you know of a similar argument for why gauge theory is output, rather than input, in quantum field theory, please enlighten me :)

    Let me emphasize that I completely agree with you that the landscape is an ENORMOUS problem. The honest statement, though, is that string theory as a framework predicts the existence of gauge theory, and in particular any particular string vacuum tells you the gauge symmetry and matter content of the theory.

    That’s all I meant. The landscape is a huge, huge problem, I agree. Just because string theory as a framework predicts gauge theory, which we do see in our world and which is input in quantum field theory, doesn’t mean that it predicts our world, or that there is any string vacuum that contains the standard model complete with Yukawa couplings.

    There, hopefully my point is a bit clearer :) I’m agreeing with you that there is a lot of hype, and the landscape is a problem. If you’d like me to elucidate more on gauge symmetry and matter content in string vacua, I’d be happy to, but I think you probably know all this.

    J

  • Phil

    Peter and Cliff,

    Here’s a thought. The QFT formalism makes no definite predictions about what causes electroweak symmetry breaking. There are many possibilities: a single Higgs boson, many supersymmetric Higgs particles (because SUSY is part of QFT), technicolor, extra dimensions (because the QFT formalism does not depend on the dimensionality of spacetime), etc.

    For many years, we have been experimentally unable to determine which of these possibilities is correct (if any).

    Therefore, QFT is not predictive. :)

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    J,

    I just don’t see a meaningful argument here. You’re just playing games with words like “prediction” “string theory” and “gauge symmetry”. And you’re doing this with the goal of making an obviously absurd point (that a theory that cannot, even in principle, be confronted with experiment in any way is as good or better than the one that has done this more successfully than any other scientific theory in human history). What’s the point of trying to argue with someone about an absurdity? It’s an obvious waste of time.

    Cliff,

    OK, you should ignore what I have to say because I’m a dishonest, publicity-hungry, money-grubbing guy whose views are far out of the mainstream, and is completely delusionally unaware that he is so, so wrong and his betters the agenda-free string theory experts are right. You’re quite right to stick to the mainstream point of view presented at this blog on the multiverse and string theory.

    One piece of career advice though: for some mysterious reason, no US physics department is willing any more to offer permanent positions to anyone working in this mainstream. Something to keep in mind…

  • Phil

    “A person with an agenda has very little chance to influence me without solid arguments. Sorry but my assessment is that your main project in life seems to be to influence popular perceptions of physics in the PR arena…”

    I agree. If one follows Peter’s blog, he will get the impression that Peter has it in for SUSY and finds enjoyment in reporting on the LHC’s failure to see any evidence of SUSY. It seems to me like he wants SUSY and String Theory to fail, to not have any evidence in its favor. But why? What difference does it make how nature works one way or another?

  • Phil

    Peter,

    “I just don’t see a meaningful argument here. You’re just playing games with words like ‘prediction’ ‘string theory’ and ‘gauge symmetry’. And you’re doing this with the goal of making an obviously absurd point (that a theory that cannot, even in principle, be confronted with experiment in any way is as good or better than the one that has done this more successfully than any other scientific theory in human history). What’s the point of trying to argue with someone about an absurdity? It’s an obvious waste of time.”

    It seems like arguing with you is a waste of time. I understood J’s argument pretty well. For example, J said, “Most vacua give some sort of gauge symmetry and particle content, and this is one of the great successes of string theory as a framework (and a specific prediction, accessible at low energies, of each individual string vacuum)”

    Now, what’s so hard to understand about that? You specify a vacuum, and out comes a specific gauge symmetry and particle content as a prediction of that particular string vacuum. The trouble, in my opinion, is how to construct promising string vacua? And that because string theory is not that well understood, theorists don’t have a good handle on constructing string vacua. But given a vacuum, out pops the gauge symmetry and particle content. Is what J said incorrect? Do you have any references that shows J’s error in this statement of his?

    Peter, you said that the theory cannot in principle be tested? Intelligent design cannot, in principle, be tested. But if you smash particles together near the Planck scale, and if string theory is true, you surely will see evidence of this at those experiments.

    If QFT is so predictive, how come it doesn’t unambiguously predict the source of electroweak symmetry breaking? There are many possibilities from the QFT framework.

    Peter, you said, “One piece of career advice though: for some mysterious reason, no US physics department is willing any more to offer permanent positions to anyone working in this mainstream. Something to keep in mind…”

    How do you know this? Do you receive reports from every research university and liberal arts college in the US?

  • J

    Peter,

    I’m surprised to be treated with any level of animosity (absurdity? really?) after I tried myself to write so respectfully.

    I’m not playing any games with the words string theory and gauge symmetry. I made a very clear point that you either do not understand or choose not to address. Rather than just calling it absurd, why don’t you address it? Do you disagree that each individual string vacuum predicts the gauge symmetry and matter content one would see at low energies? Just curious . . .

    Happy to keep chatting about this, but I need to ask one question at a time since you’ve now avoided (twice) good arguments from a trained physicist.

    And, just to be clear once more – I DO agree that you make some good points: the landscape is an enormous problem. I’m just criticizing other points and am asking you to address my criticism or back away from the aggressive statements you’ve made in this thread.

    J

    P.S. Phil, just saw your post after I posted this and am posting this edit. I’m glad to hear that you understood my point.

    One thing to correct – string theorists do understand more than you’re giving them credit for, though, including how to construct vacua with promising gauge symmetry and matter content. Doing it uniquely and dealing with all the other issues is the problem. I’m happy to elaborate, if you’d like!

    Also, it seems that a small fraction of vacua look anything like our world wrt gauge theory. But people are clever and can get things a whole lot like the MSSM in terms of gauge symmetry and matter content. These are both scientific facts. One is a con, and one is a pro, in my mind. The important question is why would we be in a string vacuum with our gauge theory (as opposed to many other possibilities), rather than whether there are vacua with similar gauge theory to what we see in the world. The latter is settled, similar vacua exist.

    P.P.S. Phil, I agree completely with the Planck scale argument. That’s predictive at high energies. (More specifically the string scale, but that’s likely close to the Planck scale if we live in a string vacuum).

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    Phil,

    http://particle.physics.ucdavis.edu/rumor/doku.php?id=archive:2011

    No, the statement “string theory is true” makes no predictions about what you will see at the Planck scale. Try reading the discussion between Tom Banks and Sean above to get some idea of how little understood such a question is. Huge questions about the very nature of such a theory are completely open, it’s extremely far from “just look at the string vacua and calculate what they predict”. Generically, you don’t know how to characterize a “string vacuum” (string theorists admit they don’t know what the theory fundamentally is, why do you think they understand its ground states and how to do reliable calculations in them?).

  • http://www.math.columbia.edu/~woit/blog Peter Woit

    J,

    Sorry if my response came off as animosity. But the bottom line remains: I understand exactly what you wrote but I’m not getting any younger, life is short, and I’ve wasted enough of mine already on this kind of thing the past few years. The situation of string theory “predictions” vs. SM predictions speaks for itself.

    A wise and very prominent HEP theorist told me long ago that he felt there was no point in wasting his time arguing with string theorists, since as time went on and it became more and more clear that string theory unification predicted nothing, the field would move on and abandon the idea. I think he was right and I should have listened more carefully to him….

  • Phil

    Peter,

    Thanks for the links. I’ll take a look.

  • J

    Hi Peter,

    It’s okay, we all care a lot about these things (fundamental physics) and it sometimes gets charged up.

    I hear you that you’re sick of arguing about such things. But again, you’re comparing one particular quantum field theory (the SM) to a framework for physics, not a string compactification. But alas, it seems this is not a distinction that you and I are going to reconcile here. Well, perhaps not the importance of it, at least :) We can disagree.

    Regarding what you said to Phil: I agree that there are very fundamental open questions, and that the nature of M-theory is still not understood. But this doesn’t mean that nothing can be said, and in particular weakly coupled corners of string theory definitely are quite well understood, and it IS known what the gauge symmetry and matter content are. Would you like examples? I’m reasonably familiar with most of the semi-realistic corners of the landscape, and can both cite papers and explain examples in a few sentences. Type II and heterotic are probably the best understood. F-theory has some of the most beautiful mathematics. (Kodaira classifications of singular fibers –> ADE –> gauge symmetry from 7-branes)

    J

    P.S. And, yes, I’ll vouch that jobs (as will the rumor mill) are going to phenomenologists more and more. Part of this is string theory PR, but most of it (and the right reason) is that the LHC is cranking up and phenomenologists really should be hired with more frequency.

  • J

    Alright, it seems like conversation has waned, but I’ll check back here periodically for updates.

    The fact of the matter is that the gauge symmetry and matter content at a particular point in the moduli space of a string compactification is very often explicitly known. I’m still happy to provide examples, both in terms of papers and explanation.

    But the fact is that very often the gauge symmetry and matter content at a point in the landscape is known, even if not all aspects of the theory are understood. Just string theory isn’t fully understood doesn’t mean that it’s not understood at all!

    Thanks for the lively discussion,
    J

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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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