The evidence crisis

220px-Calabi-Yau-alternateby Jim Baggott

Thanks to a kind invitation from the Simons and John Templeton Foundations and the World Science Festival, last Friday (30 May) I participated in a public discussion on ‘Evidence in the Natural Sciences’ with Professors Brian Greene and Peter Galison.

This discussion was the final act in a one-day symposium of the same name, held at the Simons Foundation’s Gerald D. Fischbach Auditorium on 5th Avenue, in New York City. These were comfortable, well-appointed surroundings. But the overwhelming message from the symposium was actually quite discomfiting. In its 300-year maturity, it seems that science is confronted with nothing less than a crisis of evidence.

The crisis takes many forms. I learned that mathematicians are increasingly resorting to computer-based proofs that signal a loss of certainty and the ‘end of conviction.’ Efforts are underway to develop computer-based algorithms that will soon provide the only way to review such proofs, leading one audience member to wonder how long it will take to eliminate mathematicians entirely from the process.

Eliminating humans, and their biases and general lack of self-criticism, appears to be the only workable solution to a crisis of evidence in the bio-medical sciences as well. This is a field in which John P. Ioannidis (now at the Stanford School of Medicine) famously declared in 2005 that ‘most published research findings are false’ [1]. This was real sit-up-and-take-note stuff. The research findings in question are of the kind that can lead eventually to clinical trials of new drugs.

I’d been invited to address yet another type of evidence crisis. Last year I published a book, called Farewell to Reality, which challenges some of the prevailing opinions about contemporary theoretical physics of the kind which address our ‘big questions’ concerning the nature of the physical universe. In it I argue that some theorists have crossed a line. They are suffering a ‘grand delusion,’ a belief that they can describe physical reality using mathematics alone, with no foundation in scientific evidence. I call the result ‘fairy-tale’ physics.

My role in our public discussion was that of interlocutor and facilitator. Greene is of course widely known for his Pulitzer short-listed The Elegant Universe and follow-ups The Fabric of the Cosmos and The Hidden Reality, his many radio and TV appearances and his growing role as a popular science educator (he is co-founder of the World Science Festival with his wife, former ABC News producer Tracy Day). Galison is a Harvard science historian with a flair for popularization, author of Einstein’s Clocks, Poincaré’s Maps and Objectivity. He has developed a couple of TV documentaries, about the H-bomb and about national secrecy and democracy, and is currently working on a film about the long-term storage of nuclear waste.

And then there was me, sitting in the middle. An interlocutor with an agenda. What follows is not a transcript of our discussion (I’m hoping that the Simons Foundation will post a video of this online), but rather a summary of my position.

So What’s the Problem?

Wind the clock back. On 4 July 2012, I watched a live video feed from the CERN laboratory near Geneva, and celebrated the announcement that a particle that looked a lot like the Higgs boson had finally been discovered.

This was a triumph for a theoretical structure called the standard model of particle physics. This is the theory that describes physical reality at the level of elementary particles and the forces between them and which helps us to understand the nature of material substance.

But our joy at the discovery of the Higgs was tempered by concern. We know that the standard model can’t be the whole story. There are lots of things it can’t explain, such as the elementary particle masses and the nature of dark matter. And it is not a ‘theory of everything’: it takes no account of the force of gravity.

We build scientific theories in an attempt to describe and hopefully explain empirical data based on observations and measurements of the physical universe around us. But in the twenty-first century we’ve run into a major obstacle. We have evidence that tells us our theories are inadequate. But we have no data that provide meaningful clues about how our theories might be improved. Theorists have therefore been obliged to speculate.

But in their vaulting ambition to develop a ‘theory of everything,’ some theorists have crossed a line without any real concern for how they might get back. The resulting theories, invoking superstrings, hidden dimensions and a ‘multiverse,’ among other things, are not grounded in empirical evidence and produce no real predictions, so they can’t be tested. Arguably, they are not science.

Albert Einstein once warned [2]:Time and again the passion for understanding has led to the illusion than man is able to comprehend the objective world rationally by pure thought without any empirical foundations — in short, by metaphysics.” What did Einstein mean? Quite simply, there can be no science without evidence or at least the promise of evidence to come.

How Should We Interpret ‘Reality’?

I believe that the root of the problem lies in the way we seek to interpret the word ‘reality.’ Pick up any text on philosophy and you’ll find discussions of reality under the general heading ‘metaphysics.’ How come? Physical reality seems really rather tangible and logical. It confronts us every morning when we wake up. Surely, despite what the philosophers might say, we can be pretty confident that reality continues to exist when there’s nobody looking. The science fiction writer Philip K. Dick once declared: “Reality is that which, when you stop believing in it, doesn’t go away.” [3]

But reality is curiously schizophrenic. There is an ‘empirical reality’ of things as we observe or measure them. This is the reality that scientists try to address. The purpose of science is to seek rational explanations and ultimately an understanding of empirical reality by establishing a correspondence between the predictions of scientific theories and the results of observations and measurements. Such a correspondence gives us grounds for believing that the theory may be ‘true.’

Here’s an example. In 1964, Peter Higgs, Francois Englert and Robert Brout speculated that there must exist a special kind of quantum field — which became known as the Higgs field — responsible for giving mass to elementary particles. In 1967 Steven Weinberg used this field to predict the masses of some exotic particles called W and Z bosons, which we can think of as ‘heavy photons.’ These particles were discovered at CERN in 1983, with more-or-less the masses that Weinberg had predicted. Consequently, the Higgs field was incorporated into the standard model of particle physics.

But there could in principle have been other possible explanations for the masses of the W and Z particles. If the Higgs field really exists, then it should produce a tell-tale field quantum — the Higgs boson. In 2012, establishing a correspondence between the empirical data produced at CERN and theoretical predictions for the behavior of the Higgs boson gave us grounds to believe that the Higgs field really does exist and that the standard model is ‘true’ within its domain of applicability.

We would perhaps not hesitate to declare that lying beneath this empirical reality must be an independent reality of things-in-themselves, a reality of things as they really are. But such an independent reality is entirely metaphysical. Kind of by definition, we cannot observe or measure a reality that exists independently of observation or measurement. We can only speculate about what it might be like. As Werner Heisenberg once said: “We have to remember that what we observe is not nature in itself, but nature exposed to our method of questioning.” [4]

It is this independent reality that philosophers try to address, which is why their speculations appear under the heading of ‘metaphysics.’ Now, philosophers are not scientists. They don’t need evidence to establish a correspondence between their interpretation of an independent reality and our empirical world of observation and measurement. They’re more than satisfied if their interpretation is rationally and logically structured and coherent. There is truth here, but of a subtly different kind.

Crossing the Line

Contemporary theorists find themselves caught in a bind. Without any clues from empirical data to guide theory development, and ever eager for answers to the ‘big questions’ of human existence, it seems that theorists have had no choice but to cross the line from physics to metaphysics.

There’s nothing wrong with this. Theorists have been doing this for hundreds of years. But, as scientists rather than philosophers, they have speculated about the nature of an independent reality of things-in-themselves with the aim of getting back across the line as quickly as possible. Einstein’s special and general theories of relativity were founded in arguably metaphysical speculations about the nature of space and time. But Einstein was at pains to get back across the line and show how this interpretation of space and time might manifest itself in our empirical reality of observation and measurement. The rest, as they say, is history.

Contemporary theorists have simply stopped trying to find their way back. Worse, they have built a structure so complex and convoluted and riddled with assumptions that it’s virtually impossible to get back.

What do I mean? As they have explored the metaphysical landscape of a mathematically-defined independent reality, the theorists have misappropriated and abused the word ‘discovery.’ So, they ‘discovered’ that elementary particles are strings or membranes. They ‘discovered’ that there must be a supersymmetry between different types of particle. They ‘discovered’ that the theory demands six extra spatial dimensions which must be compactified into a space so small we can never experience them. They ‘discovered’ that the five different types of superstring theory are subsumed in an over-arching structure called ‘M-theory.’ Then, because they ‘discovered’ that there are 10-to-the-power-500 different ways of compactifying the extra dimensions, each of these must describe a different type of universe in a multiverse of possibilities. Finally, they ‘discovered’ that the universe is the way it is because this is one of the few universes in the landscape of 10-to-the-power-500 different kinds that is compatible with our existence.

I want you to be clear that these are not discoveries, at least in the sense of scientific discoveries. They are assumptions or conclusions that logically arise from the mathematics but for which there is absolutely no empirical evidence. It’s not really so surprising that the theory struggles to make any testable predictions. There is simply no way back to empirical reality from here.

Don’t be blinded by all the abstract mathematics, all the ‘dualities’ which connect one kind of mathematical description with another. These help to establish ‘coherence truths,’ of the kind X = Y. But when neither X nor Y correspond to anything in the empirical world that even hints at the possibility of an observation or a measurement, then we can be clear that this all remains firmly metaphysical.

Alarm Bells

We have a problem. The theorists are stuck on the wrong side of the line, and most believe there is no viable alternative. As Nobel laureate Steven Weinberg remarked to me a little while ago [5]:

String theory still looks promising enough to be worth further effort. I wouldn’t say this if there were a more promising alternative available, but there isn’t. We are in the position of a gambler who is warned not to get into a poker game because it appears to be crooked; he explains that he has no choice, because it is the only game in town.”

Obviously, we sympathize. But what if, instead of being obliged to attend remedial therapy, those addicted to gambling were able somehow to influence the rules, to make gambling an acceptable pastime? No scientist likes to be stigmatized, to be accused of pseudo-science. This is why some in the theoretical physics community are seeking to change the way we think about science itself.

For example, string-theorist-turned philosopher Richard Dawid recently argued [6]: “final theory claims introduce the new conception of a scientific process that is characterized by intra-theoretical progress instead of theory succession … The status of a merely theoretically confirmed theory will always differ from the status of an empirically well-tested one. However, in the light of the arguments presented, this difference in status should not be seen as a wide rigid chasm, but rather as a gap of variable and reducible width depending on the quality of the web of theoretical arguments.”

The problem with this is that as soon as we accept the notions of ‘intra-theoretical progress’ and ‘theoretically confirmed theory’ we risk completely disconnecting from any sense of real scientific progress. We risk losing respect for evidence, deepening the crisis, unplugging from empirical reality and training — how many? one, two? — generations of theorists to believe that this is all okay, that this is science fit for our modern, post-empirical age. We ensure they inherit an addiction to gambling.

Some are already talking of these theorists as ‘lost generations’ [7]: “It is easy to estimate the total number of active high-energy theorists. Every day hep-th and hep-ph bring us about thirty new papers. Assuming that on average an active theorist publishes 3-4 papers per year, we get 2500 to 3000 theorists. The majority of them are young theorists in their thirties or early forties. During their careers many of them never worked on any issues beyond supersymmetry-based phenomenology or string theory. Given the crises (or, at least, huge question marks) in these two areas we currently face, there seems to be a serious problem in the community. Usually such times of uncertainty as to the direction of future research offer wide opportunities to young people, in the prime of their careers. To grab these opportunities a certain reorientation and re-education are apparently needed. Will this happen?”

Maybe it’s already too late. In a more recent assessment, Dawid writes [8]: “Many physicists may wish back the golden old days of physics when fundamental theories could (more often than not) be tested empirically within a reasonable period of time and a clear-cut empirical verdict in due time rendered irrelevant all tedious theoretical considerations concerning a theory’s viability. Empirical science, however, must answer to the situation it actually faces and make the best of it. A sober look at the current situation in fundamental physics suggests that the old paradigm of theory assessment has lost much of its power and new strategies are already stepping in.”

There’s more. Scientists have a duty of care to a public that has developed an unprecedented appetite for popular science. This is an appetite that was greatly enhanced by the success of Stephen Hawking’s A Brief History of Time and has been fed by some excellent science writing, not least from Greene himself.

I haven’t done the research, but I very much suspect that if you were to ask a randomly selected group of scientifically literate readers about the theories we use to describe and understand the universe, many of these readers will likely tell you something about superstrings, hidden dimensions and the multiverse.

In truth, today these theories describe nothing and add nothing to our understanding, because this is metaphysics, not science. These theories do not form part of the accepted body of tried-and-tested scientific theory used routinely to describe our physical world, the kind used at CERN in the hunt for the Higgs boson. As Nobel laureate Tini Veltman claimed, paraphrasing Wolfgang Pauli, these theories are ‘not even wrong.’ [9]

Now readers of popular science might just want to be entertained with the latest ‘Oh wow!’ revelations from contemporary theoretical physics. But surely they also deserve to know the truth about the scientific status of these theories. I think Danish science historian Helge Kragh hit the nail squarely on its head when he observed, in a review of John Barrow and Frank Tipler’s The Anthropic Cosmological Principle [10]:

“Under cover of the authority of science and hundreds of references Barrow and Tipler, in parts of their work, contribute to a questionable, though fashionable mysticism of the social and spiritual consequences of modern science. This kind of escapist physics, also cultivated by authors like Wheeler, Sagan and Dyson, appeals to the religious instinct of man in a scientific age. Whatever its merits it should not be accepted uncritically or because of the scientific brilliancy of its proponents.” Amen.

In the end

I believe that contemporary theoretical physics has lost its way. It has retreated into its own small, self-referential world. In search of a final ‘theory of everything,’ theorists have been obliged to speculate, to cross the line from physics to metaphysics. No doubt this was done initially with the best of intentions, the purpose being to get back across the line carrying some new insight about the way the universe works that would provide an empirical test. Instead, the theorists have become mired in a metaphysics from which they can’t escape.

We might ask if there’s any real harm done. I personally think there’s a risk of lasting damage to the nature of the scientific enterprise. Admitting ‘evidence’ based on ‘theoretically confirmed theory’ is a very slippery slope, one that risks undermining the very basis of science. In the meantime, the status of this fairy-tale physics has been mis-sold to the wider public. We’re in crisis, and we need a time-out.

_____

I’d like to acknowledge a debt to Columbia University mathematical physicist Peter Woit, and especially his book Not Even Wrong: The Failure of String Theory and the Continuing Challenge to Unify the Laws of Physics, Vintage, London, 2007.

Jim Baggott completed his doctorate in physical chemistry at the University of Oxford and his postgraduate research at Stanford University. He is the author of The Quantum Story, The First War of Physics, and A Beginner’s Guide To Reality. Most recently he published Farewell to Reality: How Modern Physics Has Betrayed the Search for Scientific Truth.

[1] J.P.A. Ioannidis, ‘Why Most Published Research Findings are False,’ PLoS Medicine, 2(8), e124, August 2005.

[2] Albert Einstein, ‘On the Generalised Theory of Gravitation,’ Scientific American, April 1950, p. 182.

[3] Philip K. Dick, from the 1978 essay ‘How to Build a Universe that Doesn’t Fall Apart Two Days Later,’ included in the anthology I Hope I Shall Arrive Soon, edited by Mark Hurst and Paul Williams, Grafton Books, London, 1988. This quote appears on p. 10.

[4] Werner Heisenberg, Physics and Philosophy: The Revolution in Modern Science, Penguin, London, 1989 (first published 1958), p. 46.

[5] Steven Weinberg, personal note to the author, 13 January 2013.

[6] Richard Dawid, ‘Underdetermination and Theory Succession from the Perspective of String Theory,’ Philosophy of Science, 73/3, 2007, pp. 298-332.

[7] M. Shifman, ‘Frontiers Beyond the Standard Model: Reflections and Impressionistic Portrait at the Conference’, arXiv:1211.0004v2, 14 November 2012.

[8] Richard Dawid, ‘Theory Assessment and Final Theory Claim in String Theory,’ Foundations of Physics, 43/1, 2013, pp. 81-100.

[9] Martinus Veltman, Facts and Mysteries in Elementary Particle Physics, World Scientific, London, 2003, p. 308.

[10] Helge Kragh, Centaurus, 39, 1987, pp. 191-194. This quote is reproduced in Helge Kragh, Higher Speculations: Grand Theories and Failed Revolutions in Physics and Cosmology, Oxford University Press, 2011, p. 249.



Categories: Science

Tags: , , , ,

196 replies

  1. It must have been an interesting symposium MP. For what it’s worth, what is said here seems spot on to me. The problem is that a fundamental theory must be metaphysical. So either we stick to a non-reductive physics or we venture into metaphysics. ‘Twas ever thus. But I’m not sure it would be impossible to get back again. Doesn’t Ulrich Mohrhoff show us how to do it?

    • No, the article is certainly not “spot on”. It presents an extremely oversimplified view of a complicated topic and completely mischaracterizes the theories that physicists are studying.

      Contrary to what Baggott has written, string theory is not really analogous to the standard model of particle physics, and one shouldn’t expect it to be testable in the same sense that the standard model is testable. The standard model is a particular phenomenological model that postulates specific properties for the particles observed in nature, whereas string theory is more of a general framework for constructing such models.

      It would be more appropriate to compare string theory to quantum field theory, the general formalism that physicists use to understand elementary particles. Just as the standard model is a particular example of a quantum field theory, one can construct particular models of fundamental physics based on string theory.

      Models of physics based on string theory have been used to explain aspects of the real world with varying degrees of success. Many string-inspired models of particle physics have already been ruled out at the LHC, while certain stringy models of cosmology may help to explain the results of the BICEP2 experiment, assuming those results hold up. Outside of particle physics and cosmology, string theory been used successfully to explain many aspects of strongly coupled quantum field theories, and this has implications for our understanding of nuclear and condensed matter physics.

      As soon as one specifies a particular model, string theory provides plenty of testable predictions, and it has contributed a great deal to our understanding of fundamental physics. But it is meaningless to talk, as Baggott does, about general predictions of string theory. One could just as easily say that quantum field theory is scientifically meaningless since there are no testable predictions common to all quantum field theories.

      • At last, someone who understands the different ideas.

        • Mr. Woit,

          In my last comment, I made a couple of very simple, uncontroversial points, and your link doesn’t really address any of them. It basically just says that you like the standard model better than string theory because it’s simpler.

          I don’t really care if the standard model is a particularly simple quantum field theory because that’s not the point I was making. The point of my comment was to draw an analogy between string theory and quantum field theory and point out that it’s unfair to ask for generic predictions of string theory since one doesn’t have such things in quantum field theory either.

          As you know, there are a gazillion different quantum field theories–in fact, there are infinite families of quantum field theories parametrized by various mathematical data–and these theories have all sorts of applications. Some of them, like quantum chromodynamics or quantum electrodynamics, describe particles that we observe in high energy physics experiments. Others are used in condensed matter physics where experimentalists can engineer systems that exhibit all sorts of exotic behaviors. There are still others that don’t describe any real world system but have nice features that allow theorists to study the general formalism in a simpler setting. Some of these theories even have applications in pure mathematics.

          In string theory, the situation is very similar. You have a theory in ten or eleven dimensions, and you can study all sorts of different limits and compactifications of this theory. One popular approach is to compactify the theory on a Calabi-Yau threefold to get a model roughly like the standard model of particle physics, but there are many different ways of doing this. Alternatively, you can compactify the theory on some other compact manifold like a five-sphere, and you end up with a model that describes something roughly like a system of quarks and gluons. By taking other limits of string and M-theory, you get all sorts of other interesting theories, like models of condensed matter physics, noncommutative field theories, topological quantum field theories, and more. These things all have important applications in theoretical physics and pure mathematics.

          Since string theory has so many different applications, it doesn’t make sense to talk about predictions in general. The theories that string theorists study exhibit a range of properties and describe a range of different physical scenarios. The point of my previous post was that the same is true in quantum field theory. You can’t talk about “testing quantum field theory” because the term refers to an enormous class of theories with completely different physics.

          • You’re just ignoring my argument. No, it’s not “I like the SM better because it’s simpler”.

          • To expand on my comment, since I realized there is a simple way to explain the basic point: it’s not that I “like” simple theories, it’s that those are the ones that are testable, where the theory has explanatory power. Yes, you can make qfts arbitrarily complicated and untestable if you want, but the simple, testable ones work (spectacularly well). In string theory, the simple, testable models don’t work, and all people are doing is looking for ones complicated enough to evade testability.

            I suspect that this is an issue well-known among philosophers of science, perhaps they could perform a public service by explaining this to string theory ideologs, who are extremely fond of the “QFT just as bad as string theory” argument.

          • None of this has anything to do with the point I’m making. I’m not talking about whether these theories are simple or complicated. All I’m saying here is that the statements

            String theory is untestable

            and

            Quantum field theory is untestable

            are equally meaningless because the terms “string theory” and “quantum field theory” each refer to enormous classes of distinct ideas about fundamental physics. It’s a very simple point that I’m making, and I doubt that you actually disagree with it…

          • If what you are saying is that string “theory” is actually a (large) family of theories, nobody disagrees. But if all members of this family are untestable the problem worsens, significantly, depending on how many members the family has.

          • To be precise, “string theory” is not a family of theories. It is a unique mathematical structure (whose existence is still partly conjectural but consistent with many, many consistency checks).

            What I am saying is that one can obtain a large family of theories by looking at different compactifications and limiting cases of this one unique theory. Some of these theories describe the real world, at least in some approximation, but it is absolutely incorrect to say that they are all untestable. Indeed, some of these theories have already been ruled out experimentally. It all depends on what model you’re talking about.

          • Massimo,
            The issue isn’t really the testability of particular string theory models, which gets complicated. String theory models that have any hope of reproducing the Standard Model are ferociously complicated (for example, the Calabi-Yau spaces needed are 6d manifolds for which we don’t know an explicit form of the metric, making any calculation with them very hard). For generic values of the various data needed to define a “string theory vacuum”, and thus a string theory model to be compared to experiment, calculating the low energy effective field theory parameters of the theory is way beyond any current technology (which justifies to a lot of people working on improving the technology). The state of the art is that you can at best reliably compute certain discrete data (like the number of generations). All evidence I’ve seen is that you can get any values you want for this discrete data by changing your choice of “string theory vacuum”.

            To the extent people are able to calculate more than something like the number of generations, or the low energy gauge group, it is essentially in a toy model, taking the Calabi-Yau to be a torus or some such. You can also imagine doing calculations with parameters that are not generic, but are very small, making some approximation valid.

            Back in 1985 the hope was that string theory vacua were a small set parametrizing things simple enough to calculate with. What has happened over the last 30 years is that people have found more and more ways to make such vacua (M-theory drastically increased the possibilities), while finding that any of the cases simple enough to analyze and extract predictions from don’t give the SM at low energies. With our limited understanding of what generic examples will give at low energy, all the evidence is that there’s no reason you can’t get the SM this way, but also no evidence you can’t get essentially any QFT at low energy this way.

            Claims that “given any string theory model, you can just calculate its predictions and compare to experiment” are pretty misleading, not mentioning that no one has any idea what the full space of string theory models looks like, or how to do such a calculation except in very special cases.

            I’d describe this as a theory with essentially zero explanatory power. You can get anything you want out of it, and it has shown zero ability to explain anything about the Standard Model.

            It’s true that, in principle, if you consider all qfts, you can possibly also get anything you want by taking complicated enough examples. But, the set of consistent (renormalizable) qfts is much simpler and better understood than the set of string models, and we have a lot of calculational control over large parts of this set. The history of QFT is that from the earliest days, the simplest examples of QFTs did a remarkable job of agreeing with experiment, and we’ve ended up with a rather simple example of a QFT (the SM) that does a spectacular job of total and complete agreement with experiment. If simple QFTs didn’t work, and somebody claimed that it was the really complicated ones that you couldn’t calculate with that were needed, the subject would have never gotten off the ground and long ago been abandoned.

            The basic difference between the two cases is that in the case of a QFT, you specify a small amount of info, and get out a complicated structure of predictions that you can compare to experiment in a detailed way, and this works beautifully. The explanatory power of the structure is huge and unparalled anywhere else in science. The case of string theory is at the opposite extreme: its explanatory power is zero, since you need to put in more info than you get out. Remarkably, MathPhysPhD and others want to claim that these cases are the same, because in both of them in principle you can get more or less anything by using complicated enough examples.

            I’m guessing philosophers of science recognize some well-known issues about theories and their confrontation with experiment, wonder if this sounds familiar.

          • Peter, thanks for the clarification. The move been attempted by MathPhys is precisely the same that Greene tried at one point during the debate with Jim. Unsuccessfully, from my point of view as an external observer. Then again, I’m a philosopher of biology, not physics.

          • It’s important to realize that Peter Woit is only talking about small parts of QFT and string theory. He’s only talking about those QFTs that appear in the standard model and the more complicated theories that you get by enlarging the gauge groups or adding supersymmetry. Likewise, when he talks about string theory, he’s only talking about very specific string theory models obtained by compactifying on a Calabi-Yau manifold.

            But QFT and string theory offer many other possibilities. There are a gazillion different QFTs in condensed matter physics and string theory that are important for a variety of reasons that have nothing to do with the standard model. There are also alternative ways of getting the standard model from string theory that don’t involve compactification.

            If you think about string theory from this more general point of view, then Woit’s aesthetic argument becomes totally irrelevant. There are lots of ways in which string theory could be related to the real world, and it’s not so clear what are the simplest string theory models. Moreover, the question of what one means by the statement “string theory is right” becomes extremely subtle and complicated.

            Because of this, I think it’s best to view string theory as a kind of theoretical tool or formalism. It’s possible that elementary particles are well described by string theory compactified on some Calabi-Yau manifold, but there are lots of other ways in which string theory could describe our world, and there are probably lots of applications that we haven’t even imagined yet.

      • Fair enough. But I was not speaking about string theory. I was agreeing that scientists regularly claim too much for science, The examples in the article would be just that, examples. There a lots of others. Even if I had to grant your point I would still see the article as being spot on. if I had a criticism it would be that it understates the problem.

        My apologies to the author for misattributing it to Massimo. It was the ‘posted by’ line that threw me.

  2. Hi Jim,

    … the theorists have misappropriated and abused the word ‘discovery.’ So, they ‘discovered’ that elementary particles are strings or membranes. [...] I want you to be clear that these are not discoveries, at least in the sense of scientific discoveries.

    Do string theorists actually use the word “discovered” in this way? Aren’t physicists well aware that before string theory can be regarded as confirmed it needs some good empirical evidence and predictive success?

    At the moment it does not have that, which is fine in a way, because what string theory currently is is mathematics, an exploration of mathematical structures that may or may not prove to have physical relevance. Often in history mathematical exploration has run ahead of physics and empirical evidence, so allowing some leeway there is not a problem. But isn’t everyone well aware that in the end it needs empirical verification?

    • Hi Coel,

      I meant to pick up on the usage of the word ‘discovery’ also. I’m not sure Jim is really fair here, although I guess we can say there are discoveries in conceptual or mathematical space even if we don’t know that these apply to the real world.

      • I think it’s fair if that distinction is not made very clear when presenting these ideas to the public. When Briane Greene talks about discovery of strings in a popular TV documentary, it’s understandable that people will view it as the same as electrons or maybe something closer to Higgs Boson, which was much more likely to be tested empirically but people might get the impression that strings will be just as easily and directly proven as well.

        • We need to be careful not to misrepresent string theorists such as Brian Greene. For example, here are some remarks from Brian Greene about 3 months ago (on reddit).

          “There is much new in string theory. [...] But what we lack is any connection to experiment or observation. And that is the only way to know if these ideas are correct.”

          “Not too long ago I was at home listening to a radio program about science when the host described me as a “staunch believer in string theory.” I almost hit the roof. I don’t believe in string theory. I don’t believe in anything that doesn’t have experimental support, observational evidence. So, similar to your description I would say this:

          “I think that string theory represents the most compelling approach we currently have for melding quantum theory with Einstein’s general relativity. And that’s a big deal. The failure to unite these two theories has been a large gap in our understanding for decades. But the union of which I speak is on paper. We don’t yet know if the theory is correct. And indeed, there are other approaches (eg loop quantum gravity).

          “I don’t work on those other approaches because they seem less promising to me. But nature is what decides what’s right and what’s wrong. And as of today, the jury is still out….”.

          • Coel,

            I agree that we shouldn’t misrepresent Brian but your quote themselves further my point. Clearly people view what he is saying differently from what his actual views are, which is at least partially his responsibility, especially as a public speaker.

            He doesn’t make himself clear enough when he presents his ideas and potential of string theory that this is pure speculation at this point. Brian is a really good public speaker and writer so he really sells the ideas and even though he occasionally adds in “We need to test this”, he argues very forcefully that this is likely true.

            Also, I’m pretty sure he refers to string theory as a discovery in his NOVA special, I’m at work right now but I’ll run through it later today to get a direct quote. In the meantime, here is a quote from a Columbia University page about his work on string theory.

            “String theory also says that the fabric of space can rip, an important discovery made by Greene and a colleague a few years ago, and that there are more than three space dimensions — perhaps as many as 10″

          • That last comment can be construed as a discovery about what string theory says, rather than a discovery about how nature is.

    • Coel,
      Aren’t physicists well aware that before string theory can be regarded as confirmed it needs some good empirical evidence and predictive success?

      I am puzzled. Is this the same Coel who has spent the last few days arguing that we don’t need “some good empirical evidence and predictive success” for the speculative multiverse hypothesis?

      Have you reversed your position or do you apply less stringent conditions to your favoured hypotheses?

      You carry on to say
      But isn’t everyone well aware that in the end it needs empirical verification?
      Have you really changed your position to that extent?

      • Hi labnut,

        I am puzzled. Is this the same Coel who has spent the last few days arguing that we don’t need “some good empirical evidence and predictive success” for the speculative multiverse hypothesis?

        No, I did not argue that. Indeed I argued that we do need empirical evidence and predictive success for the multiverse hypothesis. What I have said is that that empirical evidence can be indirect and that if a theory is validated by some of its aspects being both falsifiable and empirically verified then it isn’t necessarily a problem if other aspects are not falsifiable. There is no difference at all between my stance in that article and my comments on this post.

        Exactly the same applies to string theory. The problem with string theory is that currently no aspects of it have been empirically verified or shown to have had predictive success, and thus is it much more speculative than the eternal-inflation-multiverse theory, which has done a very good job of predicting CMB fluctuations (whatever one thinks of BICEP2 and the dark energy prediction).

        [Can I also suggest that we try not to derail this comment thread. It seems to me from our past interactions that I say things multiple times and you read me as saying something different multiple times.]

        • Coel, you said
          I argued that we do need empirical evidence and predictive success for the multiverse hypothesis.
          I am very happy we agree on that point. There is of course the small matter of absence of empirical evidence and lack of predictive success.

          I note that you said ‘need’ and not ‘have’. I presume this means you agree we do not yet have empirical evidence and predictive success for the multiverse hypothesis? I also note you call it a ‘hypothesis’ which, I suppose, reflects this understanding?

          In that case I need to remind you of your exact words, which seem to contradict this understanding.
          First you said:
          I thus argue that claims about a multiverse are entirely scientific

          Later you went on to explain what being scientific meant:
          we are being scientific if the information content of a model is motivated by and justified by empirical evidence. We are being unscientific if our model has information content that is not justified by empirical evidence.

          In other words, you are arguing that claims about the multiverse are scientific, because it is justified by empirical evidence and does not have information content that is not justified by empirical evidence. When you qualify the claim as being ‘entirely scientific’ you mean it is true in every respect, bar none.

          That is a very strong claim indeed. Do you still stand by it?
          Is it really true that the multiverse hypothesis is
          1) justified by empirical evidence? (justified is a strong claim)
          2) does not have information content that is not justified by empirical evidence? (another strong claim)

          These are strong claims. Do you still stand by them?
          Please do not use the derailing argument. This is directly related to Jim Baggot’s post because it nicely illustrates the issues that he talks about.

          Finally I want to reiterate an earlier point. What this debate is really about is choosing accurate and honest labels that truly reflect the state of the art. We must not inflate our claims or misrepresent them by using inaccurate labels.

          • Hi labnut,

            I presume this means you agree we do not yet have empirical evidence and predictive success for the multiverse hypothesis?

            No. As I explained at length in my article and the comments to it, we have *some* empirical evidence and predictive success for the multiverse hypothesis, though well short of sufficient to consider it secure.

            I also note you call it a ‘hypothesis’ which, I suppose, reflects this understanding?

            You suppose wrongly; physicists generally don’t read much into different words like “hypothesis”, “theory”, etc.

            When you qualify the claim as being ‘entirely scientific’ you mean it is true in every respect, bar none.

            You really do come up with the most astonishing interpretations of what I write! By “entirely scientific” I mean within the province of science at the cutting edge and the sort of thing that science should be investigating. At the cutting edge, many of the models and ideas of science turn out to be wrong.

            [Can I suggest that if you want to analyse what *I* have said, rather than what Jim Baggott wrote, then out of respect to him it might be more appropriate to do so on the comments to my article?]

      • Labnut,

        He hasn’t changed his position at all. He is being perfectly consistent, but you have been misunderstanding him.

        Coel never once said that we have grounds for accepting eternal inflation as true.

        He made two claims which are consistent with what he has said here.

        1) We should accept eternal inflation as a scientific hypothesis, not metaphysics or unscientific speculation.

        2) We do in fact have some rather indirect, limited evidence for inflation.

        There is no conflict between these claims and the agreement here that we need to be clear that these ideas remain unconfirmed and that further evidence is required before they can be accepted as true.

        • DM,
          see my reply to Coel above.
          I want to make a procedural point, in this instance. Both you and Coel frequently make the accusation ‘you don’t understand’.
          1) That is a form of put-down. It is out of place here and many forums forbid that kind of accusation.
          2) That is often the retort of those who are stuck for answers.
          3) Make your point clearly and explicitly. Quote the other person’s words, produce the facts and show where they are wrong.

          • labnut does have a point, though really I should have been the one to make it. Please let’s refrain from that sort of writing and focus on the very enjoyable, vigorous intellectual debate this site is attempting to offer (and succeeding, to some extent!).

          • Labnut, Massimo,

            I really don’t feel that these comments are fair.

            Both you and Coel frequently make the accusation ‘you don’t understand’.
            1) That is a form of put-down. It is out of place here and many forums forbid that kind of accusation.

            Firstly, I’m not saying that there is something about the world that Labnut doesn’t understand. I’m saying specifically that he was misunderstanding Coel, which is demonstrably true as we can see in the ensuing exchange. Labnut was under the impression that Coel was arguing that we should accept inflationary theory as true, but this was not in fact the case.

            2) That is often the retort of those who are stuck for answers.

            I was very clear to explain exactly the nature of the misunderstanding, and I fell my claim was vindicated.

            3) Make your point clearly and explicitly. Quote the other person’s words, produce the facts and show where they are wrong.

            I was very specific about my point. I claimed that Coel never once said that inflationary theory should be accepted as true. On Coel’s side, there is no citation I can provide to support this point because I can’t prove a negative. On your side, I was replying to a short message which was all about your interpretation of Coel’s position so I didn’t see the point of quoting you.

            I stand by what I said. I accept that perhaps I could have found a more diplomatic way to say it.

  3. This was a very well written article which makes a very good case for the problems besetting theoretical physics. It’s hard to disagree with it too much, especially with the view that theoretical physicists have an obligation to be clear on how well-confirmed their ideas are.

    However, while I agree with and acknowledge the problem, there are a few reasons why I don’t see much of an alternative to the status quo (apart from encouraging theorists to be more forthcoming about their uncertainty).

    1) As stated, it’s the only game in town at the moment. It remains a possibility that these avenues of research will yield empirical results.
    2) If there are very compelling theoretical reasons to believe something, this is more than speculation and it is appropriate that it be represented as such, even as we acknowledge that we have no way of achieving empirical confirmation.
    3) We may be blurring the line between physics and metaphysics, but unless you want to charge metaphysics with pointlessness this is not necessarily a bad thing as long as we make it clear what we are doing.
    4) We must remember that just because an idea is untestable does not mean that it is false. For instance, if the anthropic principle is indeed the explanation for fine-tuning, as it may well be, then a search for a single-universe explanation of the constants is doomed to failure. That doesn’t mean we shouldn’t try, but it also means we should take seriously the idea of a multiverse.

    • DM,
      This was a very well written article which makes a very good case for the problems besetting theoretical physics. It’s hard to disagree with it too much, especially with the view that theoretical physicists have an obligation to be clear on how well-confirmed their ideas are.

      You put it well.
      To this I would add that speculation is the normal precursor to good science. It is the necessary exercise of the mind wherein we explore conceptual possibilities. There is nothing disreputable about informed speculation that is grounded on good science and we should not be afraid to admit to speculation.

      But, and this is the big but, we must always be careful to label our speculation as being just that, speculation. This whole debate is about a labelling problem. We must be careful to apply the correct label.

  4. Few questions. Why should any independent reality, and there can be many, be any more accessible to everyday language purported to report purely subjective experiences – aka metaphysics – then any other human activity? There can be an independent reality of tooth fairies as well, let’s remember.

    Can any “metaphysical” statement ever be disproven or proven? Since the answer is no, by definition, why aren’t these statements just more magical thinking “Mind over matter.” – or really just everyday language over matter.

    Also by definition, any statement claiming to be testable by evidence must be disprovable.

    Finally, isn’t the “crisis” of unexplainable observations and measurements always how knowledge advances? Knowledge being the prediction of measurable future events.

    It seems a too clever marketing trick for philosophers to claim where there is uncertainty in language and empirical statements metaphysics and philosophy should be rushed in – like religious folks and the “god of the gaps” rhetorical trick.The author is proposing a “philosophy of the gaps” argument.

    Give the “gaps” a little while and some will be spanned.

    • BMM, I thought hard about whether to approve this comment. On the one hand, I don’t want to impede the flow of discussion, especially from people who disagree with my positions (or, in this case, the guest author’s). But please be consider that my patience is not infinite. Your comment has actually precious little to do with the essay itself, and Jim is most certainly not advancing a “philosophy of the gaps” argument, whatever the heck that may be. Cheers.

  5. The big question for me on this issue is what is the best and most productive course of advancing science or physics in this case. I can see the force of the arguments on each end, with string theory being the only game in town, it makes sense to work towards it. However, it can also be argued that too many resources in terms of talented people and money has been spent in that direction with little to show for it. Maybe putting string theory on the back seat will give physicists a new way of looking at the problem.

    This is of course tricky because neither strategy is guaranteed to lead to success but considering we have been trying at String theory for decades now and have not made any progress, I would lean towards putting it in the back seat but not getting rid of it completely.

    • Except I don’t know how putting string theory in the back seat will give physicists a new way of looking at the problem. Unfortunately, we don’t automatically get new ideas by setting old ideas to the side, especially when we’re talking about a population of intelligent, dedicated and motivated physicists and not one individual stuck in a dead end. There are already many, many people trying to find viable, testable alternatives to string theory, and until they succeed it and other untestable ideas such as loop quantum gravity will remain the only game in town.

      • I know of one way: it would free faculty lines, postdoc and graduate student positions, as well as research grants, to explore other options. During the debate Greene was extremely disingenuous when he painted an idyllic picture of the research community, in which individual scientists are completely free to choose what to work on, without any constraint whatsoever. Please.

      • We also don’t automatically get new ideas or progress by throwing all of our eggs into a basket that has not produced anything for decades now. I think you also are underestimating how much the current popular theory can influence young researchers into thinking this is the only viable way to go about the problem. That to me indicates that they are not pushing themselves as hard to think about alternatives because they are more convinced that string theory will lead the way. It’s possible but it’s certainly not as likely as say 30 years ago, when I would have been far more optimistic about string theory.

        • I’m not sure all our eggs are really in one basket, but I accept that I may be underestimating the influence of string theory on young researchers.

          • Check out Smolin’s Trouble with Physics, it includes a sociological analysis of funding and hiring in fundamental physics.

          • Hi Massimo,

            Check out Smolin’s Trouble with Physics, it includes a sociological analysis of funding and hiring in fundamental physics.

            You are right that there is an issue here, but it is also the case that fashions change. The people deciding on academic appointments and grant awards are actually pretty sensible in the end.

          • Coel, I’ve served on NSF panels (different field though), and while it is certainly the case that I’ve largely seen good faith efforts by smart people to fund the best science, it was also pretty obvious to me how fashions, sociological factors, and even individual psychologies clearly affected the outcome.

          • Hi Massimo,
            I agree (seen it myself also), but the “fashions, sociological factors, and even individual psychologies” tend to change over time rather than be permanent fixtures, so in the end the problem is got round.

            The process is of course far from perfect, but then everyone involved is human.

          • Of course. Does that mean we aren’t justified in level critiques to improve it? (I know, that’s not what you are saying, but you are coming close, in my reading.)

          • I agree that the critiques do a valuable service (similar to, for example, the role of MOND in comparing to dark matter models).

            What I would disagree with is the suggestion in the article that “There is simply no way back to empirical reality from here”. If string theory continues to be unproductive then fashions will change and physics will move to other ideas.

          • I think the author meant “no way back to reality” from this way of doing science. Remember that a number of string theorists are actually advocating radically rethinking how we do science and what we consider “evidence.”

  6. Interesting to compare this with the recent posts by Coel Hellier, and the comparison suggests to me two possible ways of rescuing current theoretical physics from the charge of physical meaninglessness. (1) It may be that the number of possible coherent theories that are compatible with known physics turns out to be very small, so that the laws and minimum set of parameters needed to specify our Universe are shown to be less than completely arbitrary; I think we would all agree that this would count as progress in our understanding of reality (this, I think, was at one time the hope with string theory); (2) It may turn out that some current theory will later be found to have testable consequences, just as the Big Bang theory turned out (as Hellier describes) to be testable in ways that Lemaitre could not have envisaged.

    I leave it to those more knowledgeable than me to evaluate these suggestions.

  7. Re getting young academics to work on alternatives: in every field I know much about, the most arcane, non-intuitive, complex the theory, the more specialized and unreadable the journals that publish the stuff, the more jobs. Also, never underestimate the role of faculty, who will after all review and approve the degree, in “guiding” students toward their own perspective, even if privately the faculty may acknowledge little or no results other than jobs. No idea how to break this pattern.

    JG

  8. Although I’m very sympathetic with the author’s main point, I don’t think he has a very adequate discussion of what constitutes “evidence.” All me to play Devil’s advocate. In what sense, exactly, does our current empirical data not serve as (perhaps inconclusive) “evidence” for these metaphysical theories? It’s not as if these superstring theorists are making stuff up COMPLETELY out of whole-cloth – they’re trying to find the most plausible explanation of our currently available empirical data.

    Now, I suspect Jim (if I may) might say something like this: “Ah, but our currently available empirical data is compatible with a number of different theories. Perhaps M-theory is a reasonable explanation for our currently available data, but there might be other possible explanations. Until we have more evidence, we have no reason to think that M-theory is a better explanation of the data than some alternative, empirically-equivalent theory.”

    But the obvious response here is to point out that theories are ALWAYS underdetermined by empirical data. Take, for example, what Jim writes about the Higgs boson: “There could in principle have been other possible explanations for the masses of the W and Z particles….In 2012, establishing a correspondence between the empirical data produced at CERN and theoretical predictions for the behavior of the Higgs boson gave us grounds to believe that the Higgs field really does exist and that the standard model is ‘true’ within its domain of applicability.” True, the realization of a prediction gives us grounds to believe that the Higgs field really exists, but you can *still* say “there could in principle have been other possible explanations” for the new experimental results. There are *always* infinitely many incompatible theories that have the same empirical predictions. Even when Einstein’s empirical predictions for relativity were realized, you could say “there could in principle have been other possible explanations.”

    Of course, one might reply that some explanations are more reasonable or plausible than others, even if they have empirically equivalent predictions. But now you’re playing right into the hands of the string theorists. They would probably argue that, although there could “in principle” be alternative explanations for our current empirical data, they are giving the most plausible or reasonable explanation. So they would say string theory is supported by “evidence” in the same way that the existence of the Higgs field is supported by “evidence.” The main difference between the two is just the *order of discovery* – in one case, the theory came first and predicted new empirical evidence, whereas in the other case the evidence came first and the theory was produced afterwards.

    To be clear, I agree with Jim that a theory’s ability to predict *novel* empirical results (instead of simply being consistent with current empirical results) is extremely important. But it’s not at all obvious to me *why* it should be important (as far as evidence is concerned). Whether an empirical result is discovered before or after the proposal of a theory seems to hang too much on contingent historical and psychological factors.

    Sorry to be so pedantic: this is all a rehash of basic issues in philosophy of science. But that’s kind of my point. As much as I want to agree with the author’s position, it seems to me that he hasn’t even begun to address the oldest and most basic objections.

    • Hi C Lqrvy,

      a theory’s ability to predict *novel* empirical results (instead of simply being consistent with current empirical results) is extremely important. But it’s not at all obvious to me *why* it should be important …

      As you say, given any set of facts, one can invent an infinite set of models that are compatible with those facts. Just on probability grounds, however, it is very unlikely that any random one of those models then explains novel facts that it wasn’t designed to explain, since there are vastly more ways of being wrong than right.

      Thus if such a model does explain a fact that it wasn’t designed to explain, then that is a strong indication that the model resembles the truth, since only the truth will explain any and all novel facts.

      Colloquially summed up as “Oh, what a tangled web we weave: When first we practise to deceive!”.

    • > But now you’re playing right into the hands of the string theorists. They would probably argue that, although there could “in principle” be alternative explanations for our current empirical data, they are giving the most plausible or reasonable explanation. So they would say string theory is supported by “evidence” in the same way that the existence of the Higgs field is supported by “evidence.”

      I think the way concepts like “evidence” and “underdetermined by empirical data” are used here, misses the (physical) point. There’s no way one can use these expressions to compare the standard model and string theory in any (physical) meaningful manner. The standard model is extremely succesful and supported by a huge number of experiments. Sure, it’s underdetermined, but if a better theory comes along it will have to reproduce all there relevant results and aspects of the standard model (the symmetry groups etc.). Just like special relativity reduces to classical mechanics if v << c. The standard model will have to be a limiting case of this better theory.

      Afaik, even string theorists admit that there's no comparable evidence for string theory. There may be some evidence or some tantalising hints, but this evidence for string theory lacks the depth of the evidence for the standard model (or for QFT). Calling them both "evidence" misses the point. It's like comparing a rough sketch with a Rembrandt. The sketch may show some promise and the Rembrandt is underdetermined (it doesn't show the underwear). But there's an important difference that's disappears when the the sketch and the Rembrandt are both described as "drawings".

      I know that philosophy is about "concepts" etc. like evidence and underdetermination, but the proces of abstraction is taken a step too far here.

  9. Isn’t the real crises in science that we continue to collect bunches of data from observations (e.g., associated with hypothetical things like so-called dark matter, dark energy, …) and for which there is no single, coherent theory, no theory at all, or insufficient, half-baked theories to account for them?

  10. Mr. Baggott, thank you and Massimo for this contribution.to Sciencia Salon. I’ve read a couple of your books and appreciate the clarity of your style. It is reflected again in this well-written and well-organized piece. I want to focus on a few sentences in the section entitled “In the end”:

    “I believe that contemporary theoretical physics has lost its way. It has retreated into its own small, self-referential world. . . . . We’re in crisis, and we need a time-out.”

    In your opinion, what practical measures might the community of theoretical physicists take to refind its way since it seems that many do not agree with your conclusion? Or is Massimo’s statement “free faculty lines, postdoc and graduate student positions, as well as research grants, to explore other options” a necessary first step?

  11. I fully agree with Jim Baggott as he says that many of contemporary theoretical physics has lost its way. But no matter how they have retreated into its own small, self-referential world, the fact is that they have a deep impact on millions of people that are interested in physics. These people can’t understand the difference between physics and metaphysics, so they are helpless. The tendency of some physicist to raise their thesis as religious issues seems a psychological trait which is deep rooted in the subconscious mind. I don’t know if the weak version of the anthropic cosmological principle is a question of faith and allows a non-religious study, but seems obvious that the emotional aspects of some scientific thesis and ideas sprout from a sort of religious or cuasi-religious landscape. At the end scientists are ordinary people with different beliefs and disbeliefs and to deal with is not easy, although it would be desirable to set up an epistemological scheme to clarify the question. As the classics said, virtue is in the middle ground

    • Some nice points Mario. I would agree that it is a major problem that people cannot tell the difference between physics and metaphysics. I think the solution would be for physicists to learn the difference and then to explain it properly in their popular books. But as long as they dismiss metaphysics as not worth thinking about the situation is not likely to improve. Rather, we regularly see an astonishing philosophical naivety. I say bring back the days of the quantum pioneers, many of whom had sensible things to say about metaphysics, and who would probably have assumed that a decent education in it would remain forever a minimum condition for a theoretical physicist. Something went wrong somewhere.

      • Hi guymax

        The problem is that the concept of metaphysics is used in at least two senses as well as a dialectical weapon to counter the rivals in the debate. The concept of metaphysics in the way that was used by Hegel and Kant leads to an open and non-dogmatic discussion that has got room in the philosophy of science. But we have to consider that metaphysics is a borderline scenario that should conform to the framework of scientific method and to the elementary principles of logic. The chain of metaphysical reasons that is related to science should not be a fairy tale, the philosophers of science that aims to defend theorems and theories have to fit to the popperian criterion that tell us how to refute the scientific theories partially or totally. The second meaning of the concept refers to what is known as pseudoscience and is used to discredit those who defend arguments that don’t conform to the scientific method or show a disproportionate fantasy.

        Not all quantum pioneers were sensible about metaphysics and philosophy, only few catered to gain a philosophical background, Einstein was one of them and also L. Boltzmann. There is an anecdote about Einstein in this regard. In 1913 was nominated member of the prestigious Academy of Science in Berlin; who nominated him praised for their brilliance but also noted that he could have missed the target with their speculations implicit in his quantum theory of light that describes the quantum of action or photon. It seems to me that it was a polite way of saying that his photonic theory belonged to the domain of metaphysics and was out of reality. At that time, the trendy aspect of the Einstein´s physics was considered radical, a word that remember a sort of displeasure before a phenomenon considered para-scientific, pre-scientific, ambiguous, metaphysic and even freak.

        Planck himself was embarrassed for these entities and struggled hard throughout his life to understand them. I think is difficult for the cutting edge physicists to devote part of their time to study philosophy or spending years to discern the subtlety that zoom in and out the physics respect of metaphysics. Some of them would think that it is a waste of energy or even an insane project. And vice versa, others would see some aspects of the string theory and the M-theory fanciful and unreal. I wonder if the problematic inquiries of theoretical physics are the sample of a great intellectual work or the hint of a delusion. The belief in the geocentric model was a big delusion but it proved to be fertile for the advancement of science and the collection of empirical data. The same happens with some contemporary scientific conjectures, there is no problem in holding a skeptical position about them, no matter if the issue is the big bang theory, the string theory or the value obtained for the radius of the proton.

        What exceeds my knowledge is the role played by the emotional aspect of the scientist’s mind as glides across the waters of metaphysics and fantasy, the label that the emotion prints in the birth and development of certain scientific conjectures is evident. In this sense it would be nice to set up an epistemic framework that tell us, as far as possible, which are the points of contact and no contact between physics and metaphysics, reality and fantasy, and how understand the emotions from the perspective of the philosophy of science. If, as you say, something went wrong in the past, it´s our responsibility to review the situation in this present. I agree with Jim Baggott when he writes down that physics needs a time-out, though I see his idea as a metaphorical picture that somehow portrays the ideological and sociological aspects of science.

        Of course, many physicists have strong convictions about their work, quite often they shield to criticism, the critical discourse inherent in the philosophy of science is not welcome all along.

        • This all seems reasonable to me Mario. The different opinions on what metaphysics actually is does seem to be the problem, although I would characterize it as a failure of scholarship rather than a confusion over the meaning of words. .

          Philosophy of science is not my interest, and to be honest it does not seem an important area of philosophy to me. My interest is in fundamental theories,. thus in metaphysics,.

          Erwin Schrodinger is always my leading example of a physicist with important things to say about philosophy. Now there was a thinker. Far ahead of Einstein as a philosopher. Eddington I find interesting, and Heisenberg also, and a few others from around that time. But yes, it certainly was not all of them. Feynman is hopeless.

  12. Jim Baggott has described the problem with luminous clarity. Massimo has written also about the demarcation problem. It seems to me there are two demarcation problems. One is the boundary between good science and pseudo science. The other is the boundary between good science and speculative science.

    Pseudo science is a carbuncle that grows on good science, infecting society. It is always harmful. Speculative science, by contrast, is a necessary and healthy substrate to good science. But it is a dangerous thing. Unrestrained it becomes an invasive cancer undermining good science. Until now there has been a simple discipline that has kept speculation in check, preventing it from invading good science. That discipline was the insistence on anchoring conclusions in reality, by using empirical verification or falsification. This was the immune system that kept speculative science in check.

    For a variety of reasons that discipline is being loosened. One of the reasons is that science is coming up against the really hard problems. The hard problems are frustrating, they don’t admit to easy, quick or cheap solutions. In a world starved of grants and impatient for more spectacular breakthroughs it becomes tempting to do an end-run around the problem. This is what Sean Carroll is doing when he proposes that the falsifiability criterion should be relaxed.

    Then there is a deeper problem, an ethical problem. The metaphysical anchor of science was a bone deep belief in the value of truth. We were not just pursuing the ‘reality of things-in-themselves’, we were also pursuing an ideal of ‘truth’. This ethical ideal shaped the way we conducted science. It dictated care, honesty, completeness, thoroughness, fairness and transparency. This, as much as empiricism, gave us confidence in science.

    Sadly, the ethical landscape has changed in the last 60 years. Today the dominant ethical ethos is a kind of de facto moral consequentialism. Now the act is no longer wrong, only the consequences are wrong. This subtle change is unmooring science, disconnecting it from the hard principles of empiricism and truth, leaving it adrift in a sea of moral relativity. One of the results of this is the proclamation of wishful thinking as good science.

  13. An excellent piece, Jim. You quote Steven Weinberg as saying that we have to go with string theory “because it is the only game in town.” The metaphysical assumption here is that there IS a game in town: that is, the supposition is that there is a unified theory of all four fundamental forces. But there may not be any such theory.
    indeed Einstein/s general theory of relativity shows gravity is *not* like any other force – more than that, it’s not even a force, it is an artefact arising from spacetime curvature. It is therefore perfectly possible there is no unified theory of all the forces, because gravity is quite different from the rest. In that case string theory/M theory goes out the window, as do all aspects of the multiverse hypothesis that use the idea of string theory to justify physics being different in different universe domains in a multiverse. Hence the anthropic justification for all this untestable stuff can be called into question as well: it’s missing a link to experimentally established physics. Rather it’s all based in untestable metaphysical assumptions and self-referential theory, as Jim points out.
    Note I’m not referring here to inflation per se, which has proved a very productive and remarkable theory in terms of observational predictions. It’s firstly the *chaotic* version of inflation that is not proven either directly or by being based in known and tested physics, and secondly the further assumption that physics is different in different inflationary bubbles (if they do occur).

    • the supposition is that there is a unified theory of all four fundamental forces. But there may not be any such theory.

      Given that physical theories are models of nature, surely the only way in which there cannot be a unified model of all aspects of nature is if nature itself is not internally consistent, which seems a rather weird concept.

      • Coel, I don’t think so. Scientific theories could be empirically adequate models, but not necessarily approximating truth (the anti-realist position). Even if they do approximate truth, there is no guarantee at all that limited epistemic agents like us could in fact manage to produce one unified theory, as opposed to a bunch of more or less disconnected ones. Which, of course, is plainly the case at the moment, unless you can provide us with a quantum theory of economics, or evolutionary biology, or whatever.

        • Hi Massimo,

          Scientific theories could be empirically adequate models, but not necessarily approximating truth (the anti-realist position).

          It which suggestion I put on my scientismists hat and declare that the idea of “truth” and “reality” that is not approximated by complete empirical adequacy is rather bizarre, and that anything that is causally disconnected from our empirical world is not “real” (or is at best some meta-reality).

          Even if they do approximate truth, there is no guarantee at all that limited epistemic agents like us could in fact manage to produce one unified theory, as opposed to a bunch of more or less disconnected ones.

          I agree with you there, though humans being unable to find a unified theory is different from no such theory being possible.

          • Not sure why you bring in causal disconnectivity here, and I’m not an anti-realist either. I was just pointing out that it is a perfectly reasonable position to take about scientific theories. Indeed, anyone working in quantum mechanics who refers to himself as belonging to the “shut up and calculate” group is, for all effective purposes, an instrumentalist.

            There is a difference btw human inability of arriving at a unified theory and the claim of an intrinsic availability of such theory. But: a) in practice that difference may not matter, after all we are talking about science as practiced by human epistemic agents; and b) I’m not sure what a unified theory actually would look like, so I’m not so sure that one can assert its theoretical feasibility without further argument.

          • Coel, bizarre and weird are properties of the human mind. Nature is indifferent.
            But my main point is that the belief in the necessary unity of nature is a theological one, originating in the belief that a single, logical, rational causal agent is the source of nature. If you discard that belief(and I know you do) you have no way of knowing that there is a necessary unity in nature. It is a useful assumption but it may not be a true one. That kind of belief may just be an artefact of the way our mind can only comprehend the world through overly simplified models of reality.

          • Hi labnut,

            If one were to assert that nature were not a unified entity but were internally inconsistent, one would land oneself with all sorts of issues about how nature managed to cope at the joins.

          • Coel,
            how nature managed to cope at the joins.
            Yes, that is a valid objection.
            Valid in this case depends on whether my mind can make that assessment.

            My rather intelligent dogs are a powerful lesson in humility. For all their biddability, trainability, alertness and responsiveness, there are concepts and categories, necessary for a fuller understanding of their world, which are forever hidden from their minds. And they are completely unaware of this larger, deeper intellectual world that is hidden from them. They don’t know what they don’t know.

            If that is true of my dogs, is it not also possible that we are similarly limited in quite fundamental ways? We would also be unaware of our limitations and they might be profound limitations. It is our arrogance to suppose we have risen above all limitations. I know that my bumptious Jack Russell terrier is just as arrogant.

          • Which humans think that we have risen above all limitations? I, for one, just tried flapping my arms, and I didn’t fly.

        • On producing “one unified theory, as opposed to a bunch of more or less disconnected ones”: One proposal is that the end product could be a paraconsistent patchwork of theories.

          This idea comes up in software engineering: Paraconsistent logic has been proposed for making large software systems combining inconsistent codebases work.

        • I do not quite understand what “limited epistemic agents like us” means.

          Without referring to the theory of quantum mechanics or incompleteness/undecidability theorems, what is a reason for accepting this as a given? What, exactly, is absolutely given to exist and be beyond this limit.

          I might put it this way: “We do not know if there is data that is beyond the detection of any instrument we may ever build.”

          • Philip, it very simply means that we do not have unmediated access to reality. It means we have to rely on our evolved senses, limited reasoning ability and so forth. To deny that we are not limited (as opposed to omniscient) epistemic agents seems to me very strange.

          • Massimo – I don’t want to discuss this in any detail in your comment section since the system is rather confusing. I would just want to note that for some of us it would be incorrect to say that we do not have unmediated contact with reality. It is the entire claim of mysticism. We can assume otherwise, but we cannot rigorously state that the world is otherwise. We would need to prove it. If I have misread you my apologies. Just registering another view.

          • Hi Philip, Massimo,

            You’re both right.

            Massimo’s right. We are not omniscient. There may be much that will be forever beyond our grasp.

            Philip’s right. We have no evidence that the universe will ultimately prove to be incomprehensible to us.

            So you don’t actually disagree with each other. It seems to me that the appropriate attitude with respect to the comprehensibility of the cosmos to humans is agnosticism.

  14. Reblogged this on SelfAwarePatterns and commented:
    I reviewed Jim Baggott’s book a while back, saying that I thought he had made many crucial points that I hoped the theoretical physics community would heed. Science, by getting away from evidence, risks entering a kind of Neoplatonic phase. I still say speculation is fine, as long as it’s clearly labeled, but when the speculation starts to be called “discoveries”, there is a problem. In this post at Scientia, Baggott covers many of the same points.

  15. “Given that physical theories are models of nature, surely the only way in which there cannot be a unified model of all aspects of nature is if nature itself is not internally consistent, which seems a rather weird concept.”
    Well we’ve already got unified theories at the fundamental level in the sense that they can all be described by Lagrangians (or Hamiltonians). That’s internally consistent and furthermore it’s well tested. It’s not the same as a unified theory of all forces as envisaged by string theorists.
    An example of what might be: a Grand Unified Theory of strong, weak, and electromagnetic forces (which we don’t yet have) on the one hand, and Loop Quantum Gravity on the other for gravity. It’s not a unified theory in the sense aimed for by string theorists. But it might be the way things are.

    • In that case there would be no theoretical basis for the unproven and probably observationally unproveable claim that constants of nature would be different in different universe bubbles – if indeed they exist, which is also observationally untestable except in a small subset of multiverse models. Not seeing those bubbles (vide the Plank data) will of course not be accepted by multiverse advocates as proof that a multiverse does not exist.- and they will be right, it isn’t a disproof because such collisions don’t occur in many (most??) multiverses. It’s a theory that is immune to observational testing.

  16. For medicine could there be the 21st century equivalent of the popular culture around Astronomy? Is there any way a dispersed band of dedicated observers could offer co-ordinated feedback and observation to improve the work of the specialists? I don’t mean contributing to alt-med discussion boards or the rumour culture of the internet. But … something …

  17. I have a completely different take on the issue here:

    http://www.med.wayne.edu/degracialab/metaphysics/WIS_DeGracia.pdf

    The essential problem is one of intellectual scope. The demarcation problem represents arbitrary boundaries. There is something much deeper going on here than our surface ideas in Western science, in physics, and in metaphysics.

    Don

  18. “… we have no data that provides meaningful clues about how our theories might be improved.” Milgrom, Kroupa, McGaugh, and Pawlowski have such data.
    MILGROM DENIAL HYPOTHESIS: The main problem with string theory is that string theorists fail to realize that Milgrom is the Kepler of contemporary cosmology.
    http://www.astro.umd.edu/~ssm/mond/moti_bullet.html The Bullet Cluster (Milgrom)
    the dark matter crisis

  19. The standard test for the value an article is to re-read it a day later and on re-reading this one, it impresses even more. It is timely, pertinent, important and well thought out. It is interesting that no one has managed a sustained criticism of the substance of Jim Baggott’s argument, there has only been sniping from the sidelines.

    The problem seems to be a kind of evidential sleight of hand. We start with a genuinely puzzling problem that has two properties. it is hard to solve and it addresses existential issues. This seems to be a toxic combination that motivates people to fudge their arguments.

    The manner in which they fudge their arguments was nicely illustrated in the previous post. We start with puzzling data. We invent a hypothesis to explain the data. Now the magic comes in, we claim the hypothesis is verified by the same data we used to invent the hypothesis. The circularity of this reasoning is disguised in much obfuscation.

    When we start to question this we are confronted by another phenomenon, and that is an apparent ideological fervour. The tenuous new ideas are advocated with an over eagerness that is only matched by the determined tenacity with which they are defended from criticism. Why should this be?

    It was not always like this. When Fr. Georges Lemaitre first proposed his primeval atom hypothesis, Einstein famously remarked ‘no, not this, this is the creation’ and ‘your mathematics may be good but your physics is abominable’. Lemaitre’s ideas were slow to gain traction and they were only generally accepted nearly 40 years later when the hard CMB evidence came in. This is how sceptical science works, it entertains new ideas but only welcomes them once there is good, independent empirical evidence.

    Contrast this with the speculative multiverse hypothesis. This tenuous idea has been quickly embraced in a fraction of the time with an eagerness that defies rationality. Why has there been this dramatic change in behaviour? Why has there been a headlong rush to abandon the sceptical principles that have served science so well?

    I think Baggott touches on the answer when he says:
    This kind of escapist physics, also cultivated by authors like Wheeler, Sagan and Dyson, appeals to the religious instinct of man in a scientific age.“. The ideological predilections of the activist proponents of the multiverse theory are well known. What we are seeing is the toxic combination of existential issues with vacuous ideas dressed up as science (yes, that was an intentional pun).

    It is time to return to the clear thinking honesty of Jim Baggott’s arguments.

    • The manner in which they fudge their arguments was nicely illustrated in the previous post. We start with puzzling data. We invent a hypothesis to explain the data. Now the magic comes in, we claim the hypothesis is verified by the same data we used to invent the hypothesis.

      I assume you’re talking about the use of inflation as an explanation for certain observed features of the universe (such as its homogeneity and flatness). There is in fact no circularity in this example. These observed features of the universe are not the only evidence for cosmic inflation. The strongest evidence for the theory comes from precision measurements of anisotropies in the cosmic microwave background. These measurements agree remarkably well with theoretical predictions and were not available when the theory was first proposed.

      Contrast this with the speculative multiverse hypothesis. This tenuous idea has been quickly embraced in a fraction of the time with an eagerness that defies rationality. Why has there been this dramatic change in behaviour? Why has there been a headlong rush to abandon the sceptical principles that have served science so well?

      Many scientists are taking seriously the idea of an inflationary multiverse because there have been such impressive tests of inflation. I don’t think the role of data in fundamental physics has changed.

  20. Oftentimes, when there is a problem, simply adding more patches only further confuses the issue. Possibly there needs to be a bottom up review and everything has to be reconsidered.
    I think one of the fundamental issues is how we perceive time.
    We experience change as a linear sequence of events and so think of time as the point of the present moving from past to future, which physics then distills to measures of duration between events, to use in models and experiments. This being the basis of the geometry of spacetime, given clockrates vary in different conditions.
    The basic reality though, is that the changing configuration of what is, turns future into past. To wit, tomorrow becomes yesterday because the earth turns, rather than it traveling a meta-dimension from yesterday to tomorrow.
    This makes time an effect of action. Which makes it much more like temperature, than space.
    Basically time is to temperature, what frequency is to amplitude. It is just that with temperature, we experience the cumulative effect of lots of individual velocities/amplitudes and so think of it as an effect, while with time, we personally experience the individual sequence and assume there must be a universal rate, yet only experience the cumulative effect. Just like temperature is a cumulative effect.
    A faster clock only burns quicker and so falls into the past faster. The hare is long dead, yet the tortoise plods along.
    For much of human history we directly observed the sun moving overhead and concocted lots of theories to explain it, yet it was only when we realized the ground under our feet was moving, that we solved the issue. Epicycles were mathematically accurate, but that didn’t mean there were giant cosmic gearwheels. Possibly then, we are making a similar mistake with time itself.
    As for the Big Bang Theory, which is based on the premise of spacetime, there is the assumption those distant galaxies will eventually disappear, but that assumes a constant speed of light across this expanding dimension. So if the space being measured by the speed of light remains constant, as the distance it covers increases, then the space measured by lightspeed is the denominator, which makes the expanded dimension the numerator and so this is not expanding space, but an increased amount of stable distance.

  21. Reblogged this on NotNoughtScience and commented:
    I must say, the thoughts expressed in this post are worth serious consideration for all those who work in the field of science as well as all those of us who tend to follow the field’s activities. Well, the article is a very well written piece on the current “trends” in physics.
    Here is a line from the post (quoting a scientist); “The status of a merely theoretically confirmed theory will always differ from the status of an empirically well-tested one. However, in the light of the arguments presented, this difference in status should not be seen as a wide rigid chasm, but rather as a gap of variable and reducible width depending on the quality of the web of theoretical arguments.”
    Now, not to be too crude, but that above statement can very well be an exposition on how criminal lawyers, at times, get acquittal for their clients.

  22. Dear All,
    Thinking about this post it seems to me that there are three fairly distinct issues:

    (1) M-theory/String theory has not made predictions that can be tested. One can regard it as sound *mathematics*, but whether it relates to the physics of the world is seculative and unproven. Response: This is a true and fair point.

    (2) Given (1), too much time and effort is being spent on string theory. Let’s recall that theoretical physics is only one part of physics (experimental physics is much larger) and that particle physics and string theory are only one part of theoretical physics, and that paying a few theorists to sit around drinking coffee and scheming up string theory is in any case cheap compared to building the LHC and similar things.

    In any case, the effort is being put towards string theory largely because no-one has yet proposed any better ideas. If some bright young theorist schemes up a better idea then other theorists will flock to it. So, Response: I’m not convinced that there are known alternatives where the time and effort of particle theorists would be better spent, and anyhow they are likely the best ones to judge that.

    (3) The collective of theoretical physicists have complete lost their heads over this and are no longer able to distinguish mathematics from physics (or, less charitably phrased, metaphysical speculation from physics). Thus: “we risk completely disconnecting from any sense of real scientific progress” and now have “lost generations” of theorists for whom there is “no way back”.

    Response: I’m not convinced there is a real problem here and it seems to me that the theorists do have their heads properly screwed on. One has to realize that theoretical physicists are pretty much mathematicians and like the maths for its own sake. Anyone not liking maths would not become a theoretical physicist.

    So if this gaggle of theorists have gone off and are just pursing the maths because they like it then that is not too big a problem (especially since much of their time will be spent teaching maths to undergrads anyhow). There are plenty of precedents in history for maths being productive in the end. Which past maths has not been well worth a few salaries?

    I posted up-thread some recent remarks from Brian Greene that suggests he is fully aware of the lack of verification. Here are some similar remarks from Matt Strassler on his blog:

    “We’re not talking about the real world here. We’re talking about what a theory (which may *not* be the real world) would predict for the possibly-imaginary world that it describes. [...]”

    “The motivation for superstring theory is simple; it’s the best candidate around for a theory that combines quantum field theory [...] Should you “believe” in it? I thought the whole point of modern science was that we didn’t go around “believing” things that we hadn’t checked experimentally. It’s a candidate to be taken seriously; it’s not a religion that you should have faith in.”

    • The problem with the “string theorists are just doing mathematics and that’s fine” point of view is that on the whole it’s not true. There was a time when much of string theory research was quite mathematical and there was a lot of interaction with mathematicians, but that time is long gone. String theory mathematical research is an active subject, being pursued in some math departments, in a few physics departments, and in places like the Simons Center, but most string theory research taking place in physics departments has little mathematical content. For many years string theorists have been emphasizing the non-mathematical side of the subject, trying to as much as possible connect it to other parts of physics, not to mathematics (string cosmology, string phenomenology, AdS/CFT, AdS/CMT, application to heavy ion physics, etc.)

      If you want to evaluate what most string theorists are doing, you need to evaluate it as physics, and can’t just say “oh, they’re doing math, so should be evaluated as mathematicians”. For the great majority, no, they’re not doing math.

      • Hi Peter,
        So they’ve created a load of maths and are trying their best to apply it to physics. Even if they are not succeeding that well it is hard to blame them for trying.

        It seems to me that the basic problem here is the absence of better ideas. String theory is getting the flack for the fact that so far no-one has come up with a better way of unifying QM and gravity.

      • String theorists are not doing math in the same sense that mathematicians are doing math, but it’s something very similar. You can call it “formal theory” or “correspondence truths” to use Baggott’s terminology. They’re discovering logical relationships between various mathematically interesting models of physics. As Coel says, there is absolutely nothing wrong with this, and it is even desirable for theorists to continue with this sort of work in the absence of any strong hints from experiments.

        I also disagree with Peter Woit’s comments about mathematics. There is still quite a lot of interesting work being done at the interface of string theory and mathematics. There’s been a ton of recent work on Mathieu moonshine, wall crossing, mirror symmetry, super Reimann surfaces, Khovanov homology, the AGT correspondence, 6D superconformal field theories, and many other topics…

        • MathPhysPhD,
          Nowhere did I write that there is not interesting work at the interface of string theory and mathematics. As I wrote here (and often write about on my blog), this is an active and interesting subject (although the connections to string theory as opposed to QFT are often overhyped by those with an agenda).

          The point of my comment was just that most string theorists working in physics departments are not working on the topics you mentioned (I’m having trouble thinking of more than a couple physicists working on some of the topics you mention), They’re working on the topics I explicitly listed (to repeat: string cosmology, string phenomenology, AdS/CFT, AdS/CMT, application to heavy ion physics, etc) and these are not topics involving anything deep in the way of relationships between different kinds of mathematics,

          • Yes, most string theory research nowadays does not focus on the mathematical aspects, but it is still mostly “formal” in the sense that I described above.

            I can think of a lot more than just a couple of physicists working on the string theory/math topics that I mentioned. If you also count mathematicians who work on string theory, you’d have at least a few hundred people…

    • Coel,
      and that paying a few theorists to sit around drinking coffee and scheming up string theory is in any case cheap compared to building the LHC and similar things.

      You seem to be misstating the problem. Jim Baggott said “Assuming that on average an active theorist publishes 3-4 papers per year, we get 2500 to 3000 theorists.“.
      That is hardly a few theorists. Why try and minimize the problem by calling it ‘a few theorists’?

      If I was you I would not make that dismissive comparison with the LHC.
      The LHC represents the true empirical spirit of science, hypothesize, predict, verify. This is why society is prepared to spend so much money on it. This is a lesson the speculative, multiverse hypothesizers should bear in mind.

      In any case, the effort is being put towards string theory largely because no-one has yet proposed any better ideas.
      When there is a strong bandwagon effect there is a severe disincentive to doing anything else.

      I’m not convinced there is a real problem here
      There is a real problem when science starts to become disconnected from its empirical foundation. The best illustration of that problem is when a well known cosmologist(Sean Carroll), argues that the falsification criterion should be relaxed. That opens the door to fairy-tale physics. We can tell fairy tales at Christmas time but in science departments we should concentrate on hard, demonstrable truths.

      it seems to me that the theorists do have their heads properly screwed on
      We will know that when we have useful, testable predictions that survive scientific scrutiny. Until then your statement looks like wishful thinking.

      • Hi labnut,

        You seem to be misstating the problem. Jim Baggott said [...] we get 2500 to 3000 theorists.“. [...] Why try and minimize the problem by calling it ‘a few theorists’?

        Jim Baggott’s analysis assumes that everything on hep-th and hep-ph is string theory. I’ve just looked and it isn’t. Lots of stuff on hep-ph is about stuff currently observable with the LHC and is indeed about areas where physicists are directly comparing theory and data. So I’d say that Jim’s number is way out.

        If I was you I would not make that dismissive comparison with the LHC.
        The LHC represents the true empirical spirit of science, hypothesize, predict, verify.

        There was nothing “dismissive” about my comparison with the LHC (you really do come up with the most bizarre interpretations of what I write), I simply noted that it is *vastly* more expensive that all the money ever spent on string theory. And you’re right about the true spirit of science, but please note the 50-year gap between the prediction of the Higgs Boson and the discovery of it. Science has to be allowed to develop theories where the testability of those theories is unclear.

        When there is a strong bandwagon effect there is a severe disincentive to doing anything else.

        Most string theorists do indeed work on other things besides string theory, and it is contradictory to suppose there is a both a strong bandwagon effect and that string theory is getting nowhere.

        The best illustration of that problem is when a well known cosmologist(Sean Carroll), argues that the falsification criterion should be relaxed. That opens the door to fairy-tale physics.

        No it does not. Sean Carroll is entirely sensible on these issues. It’s just that your interpretation of empiricism and falsification is too narrow.

        We will know that when we have useful, testable predictions that survive scientific scrutiny. Until then your statement looks like wishful thinking.

        No, if it is the case that there are no testable predictions, *and* the case that they are well aware that there are no testable predictions and thus that the relevance to physics and the real world is speculative, then their heads are indeed properly screwed on.

        • Coel,
          It’s just that your interpretation of empiricism and falsification is too narrow.
          Instead of making broad accusations you should make concrete arguments, anything else is not useful(we’ve been over this ground before). So to help you along, let’s clarify the question.

          Tell us what is the correct interpretation of empiricism and falsification, so that we can compare it with my putative interpretation. I presume you have an authoritative source and that it is not merely your opinion?
          Then show how that differs from my interpretation, presuming you do actually know what my interpretation is. Please quote my exact words and stick to my clear intent so that there can be no misunderstanding or misrepresentation.

          No it does not. Sean Carroll is entirely sensible on these issues.
          Calling for falsification to be retired is sensible? Would you care to make a persuasive argument instead of a bald, unsubstantiated assertion?

          Your last sentence baffles me. Surely the ultimate test of scientific endeavour is that it delivers “useful, testable predictions that survive scientific scrutiny“. Is that not a reasonable position to take? If a whole field fails to deliver on this promise we should closely questions its utility.

          Science has to be allowed to develop theories where the testability of those theories is unclear.
          Yes, and if you look through my comments you will see I have consistently argued for the necessity of speculative hypotheses as a prelude to good science. You would than also see that I argue we should clearly label them as speculative and unproven until we have empirical validation.

          This is the very heart of the debate. We should be clearly and unambiguously labelling speculative and unproven hypotheses as being just that. We should not be promoting these hypotheses in high profile books because that creates the clear implication that it is good science when it is hardly more than fairy-tale physics.

          Have you read Jim Baggott’s book? I urge you to get it.

          • Or Lee Smolin’s The Trouble with Physics; or Peter Woit’s Not Even Wrong.

          • Hi labnut,

            Tell us what is the correct interpretation of empiricism and falsification, …

            I have done this extensively and repeatedly on the previous two threads. But since you ask again:

            In science, evidence validates *theories* about how things work (rather than entities). If a theory predicts A, B, C and D, and if we validate the theory by empirically verifying A, B and C then we have good evidence (indirect evidence but still good evidence) for accepting D. It doesn’t matter whether D can be falsified so long as A, B and C can be,

            Specific case 1: Suppose we use models of planetary motion to predict solar eclipses, and validate these models to a high standard using empirical data. A solar eclipse within human history could be recorded on folk memory or cave paintings or written records, but a solar eclipse before humans existed would leave no possible trace today. A prediction of such an eclipse is thus unfalsifiable and not empirically verifiable. However, it is still scientific by the above principle, and if the model is validated sufficiently then we can regard the statement “There was an eclipse at such a time and place” as factual, even lacking empirical evidence for that particular eclipse, and lacking any way of directly falsifying the statement (though one could falsify the model that predicted it).

            Specific case 2: Given the finite speed at which information can be transmitted, there is an observable horizon from beyond which we cannot obtain information. Yet, if we can validate models of how cosmology works sufficiently well, using empirical data from within the observable horizon, then we can have sufficient evidence to accept statements about beyond the observable horizon as both scientific and factual, just as in the above case of the past eclipse. (Please note that I have not stated that any particular model is so verified.) This holds despite the impossibility of obtaining information from those regions.

            Then show how that differs from my interpretation. …

            My disagreement is with anyone who takes an over-simplistic attitude of “we cannot obtain information from beyond the observable horizon and therefore any statement about any such region is unfalsifiable and not scientific”.

            Calling for falsification to be retired is sensible?

            Carroll did not call for the concept to be entirely rejected, just to be interpreted better than *some* people do. To quote him: “The falsifiability criterion gestures toward something true and important about science, but it is a blunt instrument in a situation that calls for subtlety and precision.” As I read Carroll his Edge piece is in line with my stance above.

            We should not be promoting these hypotheses in high profile books because that creates the clear implication that it is good science when it is hardly more than fairy-tale physics.

            Question for you: In the 50-yr gap between the prediction of the Higgs Boson and its discovery, would you have regarded it as wrong to discuss the Higgs and its role in the standard model in high-profile popular books? Would you have regarded it as “hardly more than fairy-tale physics” that the public should not be told about? (By the way, I do agree with you that all such expositions should be clear about what has and has not been proven, but that’s not what my question is about.)

          • Hi Coel,

            You say,

            In science, evidence validates *theories* about how things work (rather than entities). If a theory predicts A, B, C and D, and if we validate the theory by empirically verifying A, B and C then we have good evidence (indirect evidence but still good evidence) for accepting D. It doesn’t matter whether D can be falsified so long as A, B and C can be,

            I take strong exception to the claim in the last sentence. If your theory predicts A, B, C and D but we have evidence only for A, B, and C, the strength of the evidence for D is entirely dependent on how unique your theory is in predicting A, B and C. There may be a multitude of other theories that account for A, B and C but predict E (or F or …) instead of D; if none of E,F,… have been observed, then A, B and C provide no empirical evidence at all for D — D remains an unsupported conjecture. (Of course, you could claim that your theory is more “beautiful” than alternatives that predict E,F,…, but beauty is in the eye of the beholder, to use a trite phrase, and the purported beauty may even be based on a false premise.)

            My understanding is that you are looking at inflation as being highly successful in quantitatively predicting A, B and C, and it seems to be the “only game in town” that does so. Thus, we should not only take seriously its implications of “eternal-ness” (prediction “D”), we should regard A, B and C as (indirect) evidence for it and its multiverse offspring. While I agree we should take eternal inflation seriously as a consequence of the inflation idea, I disagree that A, B and C provide evidence that eternal inflation is actually “true,” for the above reasons. And I really wish you would stop suggesting otherwise.

            We have no evidence at all that the standard inflation scenario is the unique explanation for the large-scale homogeneity, isotropy, nearly-scale-invariant CMB power spectrum, etc. (By “standard inflation scenario” I mean a large vacuum energy due to a scalar field rolling down a potential, which according to general relativity drives spacetime to expand exponentially for a long enough time to do the job it was invented to do.) In no sense does the current lack of alternatives to inflation imply that no successful alternative will be developed in the future, and I expect you will agree. In fact, inflation has serious conceptual problems of which you may be well aware. Steinhardt has given a popular account of some of these (see “The Inflation Debate: Is the theory at the heart of modern cosmology deeply flawed?” in Scientific American, April 2011). Roger Penrose has given a compelling argument that inflation is extremely improbable, that it is far more likely that the observable universe with its homogeneity and isotropy is the result of a random assembly of particles than something due to inflation (see, e.g. “Difficulties with inflationary cosmology,” Annals of the NY Academy of Science, 1989: v.571, p.249). The existence of serious conceptual problems with the foundations of inflationary theory should give us pause — there is very possibly an alternative picture which could, for example, also be “inflation like” in important respects (exponential expansion of spacetime at very early times, etc.) that doesn’t rely on a scalar field potential to drive the expansion. If one drops the assumption of a preexistent spacetime manifold and requires that it and the metric emerge during cosmogenesis, the problems outlined by Penrose and Steinhardt go away. (In fact, I worked on the foundations of such a scenario for my thesis work.)

          • Hi Marty,

            There may be a multitude of other theories that account for A, B and C but predict E (or F or …) instead of D; if none of E,F,… have been observed, then A, B and C provide no empirical evidence at all for D

            I agree. I had stated that in my original exposition (last thread) but forgot to include it in my summary to labnut. The evidence for D holds only if we can not otherwise account for A, B and C.

            In no sense does the current lack of alternatives to inflation imply that no successful alternative will be developed in the future, and I expect you will agree.

            Yes, I agree. Two points: I don’t regard inflation as proven, but I do think there is good empirical evidence for it (my argument is that inflation and an eternal-inflation multiverse are sensible and scientific concepts, but I don’t regard them as proven). Second point, science is always the best we can do, rather than giving absolute truth. Given that, I do think that my basic argument above about falsification is sound and that indeed it is a necessary part of the scientific method. One can never directly verify things in a model-independent way.

        • This comment relates to this thread but actually refers to the ongoing discussion about the 50-year period that has elapsed between the ‘invention’ of the Higgs field and the discovery of the Higgs boson (Coel’s comment below). It really helps here to be mindful of the history. Yes, this has taken 50 years, but it’s quite wrong to think that there was no progress in this time. Here’s a rough outline of what actually happened (apologies to any working science historians reading this).

          The idea of the Higgs field was introduced in a series of papers published in 1964 by Higgs, Brout and Englert and Hagen, Guralnik and Kibble.
          The ‘Higgs mechanism’ (it wasn’t called that then) was used by Weinberg and Salam in 1967 as a device to break the electro-weak symmetry. Weinberg used the mechanism to predict the masses of the W and Z bosons. Note the word ‘predict’…
          This was largely ignored because it wasn’t clear that the resulting Higgs-modified quantum field theory could be renormalized. ‘t-Hooft and Veltman showed that it could be renormalized in 1971.
          Perhaps rather astonishingly, Weinberg, Salam and Glashow were awarded the 1979 Nobel prize in physics for their work on electro-weak unification, even though the theory at this stage couldn’t be considered to be proven.
          The W and Z bosons were eventually discovered at CERN in 1983, with masses very close to Weinberg’s original 1967 prediction.
          It’s fair to say (as I do in my article) that the only unambiguous evidence for the existence of the Higgs field is its tell-tale field particle, the Higgs boson. I honestly doubt that the SSC project would have gotten off the ground at all if physicists hadn’t been pretty confident that they would find it (or, at least, find something). If the project hadn’t been cancelled in 1993 we would have discovered the Higgs boson a lot sooner.

          So, it was certainly *not* wrong to talk about the Higgs in high-profile books published since the early 1980s (and many great popular science books did just this). There was nothing ‘fairy-tale’ about this. It was as a truly ‘progressive’ development and, although the relationship between theory and experiment was a bit creaky in the late 1960s, the 1970s and 1980s are considered by many to be a ‘golden age’ in high-energy particle physics.

          This is science as it should be done.

          • Jim,
            thanks, you have clarified that nicely.

            For Coel’s benefit I want to make an additional point.
            Verification of the Higgs boson field always lain within the domain of the observable. We believed it was possible to observe it and so were ready to spend a great deal of treasure on the search. So when people wrote about it they did so in a responsible way, keenly aware of the possibility of being shown to be wrong.

            Verification of the multiverse does not lie within the domain of the observable. This makes it a safe domain for elaborate and fanciful speculation. After all, no one can show you to be wrong. But does this mean it is responsible to speculate? It is the essential spirit of science to make careful claims capable of being verified. When we do not do this we enable others in the counter-knowledge movement to do the same. If we, in science, can make elaborate, fanciful claims that defy validation then why should the counter-knowledge movement not do the same? How can we dismantle their arguments when we are just as guilty?

            It is no use saying that Hawkings, Greene, Vilenkin and others qualify their claims in the small print. They have very publicly lent their name to the concept and that automatically creates the implication that it is well founded. The kindest thing I can say about them is that they are guilty of a grave deception. They have betrayed the spirit of science which has guided science for the last 400 years.

          • Hi Labnut,

            The kindest thing I can say about them is that they are guilty of a grave deception. They have betrayed the spirit of science which has guided science for the last 400 years.

            I really think it ought to be possible to point out the problems you see with the status quo without making accusations like that. I have no major problem with Jim, but I think you should perhaps moderate your tone a little.

          • DM,
            I really think it ought to be possible to point out the problems you see with the status quo without making accusations like that. I have no major problem with Jim, but I think you should perhaps moderate your tone a little.

            The fact that you can call beliefs about the multiverse the ‘status quo‘ illustrates just how serious the problem is, and that demands strong words.

            Let me remind you what Peter Woit said:
            Then there’s the “multiverse”, which I think is just a major intellectual scandal and looming disaster threatening the subject and its credibility with the public.

            Those are strong words and they come from a major expert in the field. Therefore we should pay close attention.

            I stand by my words and see no need to moderate them. Major scientific figures have published substantial books about a subject that is unproven and in all probability will never be proven. They have created a clear implication which is false. That was an irresponsible act and it should be strongly criticised. Prominent figures have a correspondingly greater duty than you or I to act responsibly.

  23. “But reality is curiously schizophrenic.” I must confess I’m a little surprised something so provocative yet failed to provoke. Unlike others, until there is even a sketch of how reality could be inconsistent, I will not take seriously any proposal that it is or even that it could be. My understanding is inconsistent but everything else about me is inconsistent, however imperfectly.

    Of course, not all provocations are intended seriously. “We would perhaps not hesitate to declare that lying beneath this empirical reality must be an independent reality of things-in-themselves, a reality of things as they really are. But such an independent reality is entirely metaphysical. Kind of by definition, we cannot observe or measure a reality that exists independently of observation or measurement. We can only speculate about what it might be like. As Werner Heisenberg once said: ‘We have to remember that what we observe is not nature in itself, but nature exposed to our method of questioning.’”

    I’m afraid that “nature-in-itself” is awfully close to a vague imagining of what a God’-eye view or Divine intuition would be, I myself tend to think that some “nature-in-itself” conceived as something ineffable is simply religion in the guise of philosophical idealism. Aspects of nature that must be observed or measured indirectly have been studied. In a way you might say science is necessary precisely because a direct knowledge of “nature-in-itself” is impossible, and simple common sense is not enough. I think instead it would be vastly more prudent to believe that reality is not the religious notion but instead consists of the observable and measurable changes effected and undergone. That it is not the eternal and unchanging but the vicissitudes of ephemeral existence that are the hallmark of reality. If this is Hegelian (albeit not Hegel himself,) so be it. I am not ashamed of having my atomism partially identified with Democritus and Lucretius either.

    The thing for me is, the anti-realist school, Copenhagen department, necessarily relies on common sense. But maybe we should call it a fideism of the mundane? The notion that the first law of motion may be different for intelligent beings on some nondescript planet beyond view of our telescopes, proving that reality truly is schizophrenic by this doctrine is perfectly logical. I believe it is nonetheless nonsense. We’ve found it to be true in an inertial reference frame here.
    I do not think there is any nature in itself where we can find it not to be true.

    The notion of schizophrenic reality where there is a mystical nature-in-itself is I think enjoyed largely because it can hide whatever the proponent wants. Whether it’s Cartesian demons, Thetans, God, the Lutheran Church or simply Carlsberg Beer, simply dubbing them all metaphysics only works if common sense is arbitrarily privileged. It guides everyday life and data “guides” the science and never the twain shall meet.The scientist, like everyone else, can then pick and choose metaphysics or religion by whatever standard they wish. Reserving science to lab reports means all the other ways of knowing have their own sphere. The scientist secure in his certainty that common sense reigns measures things in his laboratory, indifferent to the benighted who have the wrong notions of nature-in-itself. Science is the all the brass monkeys, who not only see no evil, speak no evil, do no evil, but think no evil either. If you have no taste for evil metaphysics, then live by your common sense.

    I don’t think common sense is either as common or as sensible as complacency allows. If common sense were all we needed, there’d be no need for science in the first place. I also wonder why anyone should pay for science that doesn’t describe reality.

    But I suppose many would exclaim that they too are realists, so that this is all beating dead horses without even getting any glue for my pains. My apologies.

    However, I must point out one thing, which is that superstring theorists really do count the empirical validation of quantum mechanics in general, quantum field theory in particular and general relativity as evidence for superstring theory. They do so on the ground that superstring theory can generate both as outcomes of the fundamental formalism. Therefore, the empirical evidence for them is also acquired. The question of superstrings’ existence is no more relevant than the putative existence of a state vector or a probability wave. And difficulties in M-theory and its production of common sense reality are no more obstacles to its acceptance than the mysteries of measurement or collapse of the wave function are to acceptance of quantum mechanics. Perhaps Lubos Motl should do a guest post to explain the point?

    It is true that because of the many parameters in superstring theory it is currently impossible to generate specific predictions in the way that QM or GR could, being simpler. The thing here is that predicitivism and falsificationism just don’t work as demarcation. I’m quite sure that all cosmological theories would benefit from knowing the actual mass/energy of the whole universe, but this parameter is experimentally unobservable. That doesn’t mean they aren’t science. It is not possible in principle to decide which parameters are ad hoc supplementary assumptions.

    Lastly, and maybe least in a way, but perhaps most significantly: Helge Kragh can lump together Barrow, Tipler, Wheeler, Sagan and Dyson but if he thinks they are doing the same thing? He’s got a lot of explaining to do.

    • Steven, there’s a decent discussion of noumenon and Kant’s notion of the unknowable noumenon here. I don’t know if I’d call it a religious viewpoint, though it is linked to a form of idealism, I suppose. http://en.wikipedia.org/wiki/Noumenon

      I’m not sure what your point is or that Baggott would disagree if you’re saying it’s just metaphysics.

      • It is certainly metaphysics, and pretty straightforward at then, not religion.

      • I’m sorry my point isn’t clear. I find the thesis that the problem with modern physics is its realism, something to be solved with the old time Copenhagenism unconvincing.

        First, the notion that there is a noumenal realm, nature-in-itself, is unconvincing. There is not even a hint of how reality could be inconsistent. The unknown exists, but that doesn’t make unknowability a real principle. There is no distinction that can separate the unknowable, noumenal nature-in-itself from things unknown for the most mundane of reasons. Comte was the last person to venture to identify an unknowable, and we all know how that turned out. What’s even sadder than making the same mistake but imagining you can cover yourself by cunningly omitting any specifics? Your link prominently features Bishop Berkeley for good reason, I think.

        Second, the uncritical acceptance of common sense in the anti-realist view is undesirable in itself. Correspondence to reality is not your concept of truth when you deny that reality is knowable. Agreement between predictions and laboratory data reduces to the same coherence concept of truth used by philosophy when you limit science to measurements in a laboratory, dismissing all questions of what they mean and how they describe reality by philosophical fiat. And just as commitment to logical validity instead of correspondence to reality has hopelessly mired philosophy, so too does it mire science in laboratories. You may demand that we accept reality at face value as an act of will. But I reject such militant proselytization of fideism as not just ineffective but unkind. Besides, even more importantly, the standards for unkowability don’t just deny concepts of causality without reconstructing science. Without the bland resort to “common sense” to carefully redefine the allowable questions, events or processes that surely exist cannot be presumed to exist. I think that contradicts experience, and is a kind of inconsistency too.

        Third, superstring theorists really do (strictly speaking, as near as I can tell,) believe that progress in physics demands incorporating in some form QM (broadly speaking) and GR and that superstring theory is the only thing that does this. The evidence for QM and GR are thus evidence for superstring theory. The fact that superstring theory is not formulated with parameters derived from experiment is irrelevant. I suppose you could argue against superstring theory on grounds of elegance or some version of Occam’s Razor but that kind of heuristic I think is bad metaphysics.

        • Steven, I’m going to address only your first point. The idea that there is a difference btw the way the world is and how we perceive it – which is obligatorily indirect – seems to me at this point to be an obvious consequence of our condition as limited epistemic agents. No need to bring in Copenhagen and all that.

        • Just to be clear – my argument is concerned with empirical fact, not realism per se. I don’t care whether you adopt a realist or anti-realist position in your approach to interpreting what science is telling us. Most working scientists are by nature scientific realists – they think that what they discover has meaning in relation to some underlying independent reality. That’s perfectly fine, but there can be no scientific justification for this. One of my favourite Einstein quotes is: ‘I have no better expression that the term ‘religious’ for this trust in the rational character of reality and in its being accessible, to some extent, to human reason.’

          I don’t argue against superstring theory on the grounds of elegance or some version of Occam’s razor. I argue against it because it seems to me to have no prospects for connecting with empirical fact, and ‘progress’ within the community each year appears to take us further away.

          • I actually agree that we don’t seem to be making progress, but I rather thought it was because physicists are hampered by the limits of their instruments and experimental techniques. I think many of the theorists are having trouble finding their way back to experiments because currents experiments are not yet powerful enough to provide new data. Black hole event horizons will not provoke the same kind of theoretical controversies when we can do experiments with artificial black holes. If science is stalled by a failure of technique, that is depressing but not the fault of a wrong conception of reality. (Confession: I have been strongly influenced by J.D. Bernal’s emphasis on the role of new scientific technology in the progress of science.) Further, although I don’t think you can deem theories with a bunch of parameters lacking extensive experimental measurements as intrinsically unscientific on grounds of falsifiability, simple pragmatic utility seems to offer all the grounds for criticism you might otherwise wish.

            “I believe that the root of the problem lies in the way we seek to interpret the word ‘reality.” I believe the relevance of the your anti-realism is the way it provides a touchstone for what counts as empirical evidence. (References to Copenhagen incidentally are to the shared philosophical program. Also, they came naturally in this context to a reader of The Meaning of Quantum Theory. I agree that there’s no need to revisit the Copenhagen interpretation itself.) This approach forbids asking questions that are not narrowly experimental, even to the point where model-building is disallowed. I find it doubtful that it can be reconciled with science in general. I’m not convinced that Mario Bunge’s hypothetico-deductive interpretation of science is the final word, but it is far more compelling than the half-assed Popperism that (depressingly) seems always to be the sub-text, when it isn’t the plain text.

            “There is an ‘empirical reality’ of things as we observe or measure them. This is the reality that scientists try to address. The purpose of science is to seek rational explanations and ultimately an understanding of empirical reality by establishing a correspondence between the predictions of scientific theories and the results of observations and measurements. Such a correspondence gives us grounds for believing that the theory may be ‘true.’” I believe your anti-realist approach, coupled with the predictivism, requires basically that any acceptable theory has to formulated pretty much as laboratory experiments. Just as the Copenhagenists forbade asking how classically-acting measuring instruments could interact with quantum phenomena (not even how they came into existence,) the anti-realist approach forbids asking how timeless point particles could interact the Einsteinian spacetime of everyday life. The thing I’m not agreeing with is that you can simply define away mundane reality as proper empirical evidence.

            “Now, philosophers are not scientists. They don’t need evidence to establish a correspondence between their interpretation of an independent reality and our empirical world of observation and measurement. They’re more than satisfied if their interpretation is rationally and logically structured and coherent. There is truth here, but of a subtly different kind.” Personally, I don’t think it helps to call the philosopher’s notions of truth, truth. (I think they could incorporate a correspondence notion of truth and still do philosophy, although it would be very, very different from what it is now.) But we also disagree that the superstring theorists et al. aren’t using a correspondence theory of truth as well. They just use a different concept of what counts as correspondence. (No, I’m not an official spokesman, but this is what I really do believe they say between the lines.) Although swamped in a mass of parameters currently unamenable to experimental confirmation, all these theorists so far as I can tell, attempt to correspond to reality by incorporating QM and GR into their models. And if they don’t, I believe they deem the models as illustrative or heuristic simplifications, not genuine theories aimed at corresponding to reality.
            I do believe that if technology progresses to provide more empirical data their work will change, and refuted propositions will more or less be summarily dropped (even if only when the creators drop dead.)

            I’m still not sure how an anti-realist can have a coherent notion of truth as correspondence to anti-reality. By the way, the remarks on mathematics are very confusing. And the difficulties in scientific medicine do not seem to me to have any logical relationship to the difficulties in physics. I think they’re a different set of problems entirely.

  24. This article is as nicely-written as it is biased to the point of defeatism. So much so in fact, that its main lines of thought (“It’s all gone to math”; “Ah, the math with it!”; “Math rises!”; “Heaven v. Math”, etc.) can be dismantled using a single quote by the very guy the article glorifies for his ability to come back after crossing into the “metaphysics realm”: Albert Einstein and his famous “A mathematical equation stands forever”.

    A piece of advice for a physicist not versed in classical philosophy: never attempt a philosophical treatise on just one premise, as any philosopher can (and at least one will) shoot down your entire wannabe-treatise with a single sentence. Novice philosophers have lost their careers thus; one even became a florist after having been ridiculed over his insisting that philosophy must take physics as its ideal: “one notion per paper”. Such amateur philosophers are better off if sticking to physics of our universe and leaving meta-thinking to philosophers.

  25. Jim Baggott: “Some are already talking of these theorists as ‘lost generations’, … I believe that contemporary theoretical physics has lost its way.”

    Amen! Agree 100%. Yet, this fact points out that they are the winners, that is, they will stay on the winner’s stand for a long while still. I must give you my total respect on your courage of fighting a losing battle. But, with introspection, I think that we are making a deadly tactical error.

    However powerful a steamboat is, it will be useless on the ‘land’. Science (with the falsifiability principle) was a truly great steamboat. All ‘approximated’ truth can be falsified. But, the true truth by definition must not and cannot be falsified. Now, the issues are in the new ‘land’, about the ‘true truth’, not approximated truth anymore. Thus, keeping using the ‘falsifiability’ (the old school) as a weapon to fight the war on this new ‘land’, we will definitely be on the losing side. However, we will definitely win the war sooner or later if they are wrong. But, we must get new understanding of what ‘evidence’ should be in this new battlefield. Let me use one recently discussed issue as an example.

    The ‘eternal-inflation-multiverse model’ has two vital points.
    One, quantum fluctuation gave rise to an inflation (big bang) of this universe. Then, it can logically give rise to ‘another’ universe (even with different nature constants or laws).
    Two, as there is an ‘event horizon’ of this universe, then those ‘other’ universes can sit happily outside of the event horizon of this universe.

    The two points above are logically sound. When they are presented as two ‘statements’ (not hypotheses), they are not subject to the authority of the falsifiability principle, let alone to say that ‘we’ are unable to get any evidence beyond the event horizon, by definition. Thus, the way to ‘falsify’ these two statements is by showing their logic fallacy, such as logically proving that ‘everything’ beyond the event horizon of this universe is still parts of this universe. I will show this with two steps.

    First, showing that ‘quantum principle’ is the ‘consequence’ of this universe, not the creator. I have showed that quantum principle can be derived from the ‘space-time force’ of this universe.
    F (space-time force) = K ħ/ (delta S x delta T)
    K (coupling constant, dimensionless); ħ (Planck constant); S (space); T (time).
    Then, delta P x delta S = > ħ

    Second, clearly define the ‘event horizon’ in terms of physics laws, not just a ‘verbiage’.
    The {delta P x delta S = ħ} is a ‘rectangle’ with a ‘fixed’ size defined with ħ. It actually forms a ‘viewing window’ for every event (see http://www.prequark.org/Constant.htm#II for details). Thus, the largest viewing ‘window’ is (ħ c), c as light speed. The largest ‘area’ can be viewed in this universe is {(ħ c) T}, T is the life-time of this universe, and this ‘area’ defines the ‘event horizon’.

    Then, (ħ c) ^ (1/2) = e (electric ‘charge’). Thus, (ħ c) = e ^ 2 (which produces photons). So, the ‘event horizon’ of this universe is defined by e (electric charge) and photons. That is, the CMB is indeed one ‘edge’ of this universe.

    Now, ‘event horizon’ is clearly defined with ‘quantum principle’, the viewing window. But, what is ‘beyond’ the event horizon? Can it also be defined with ‘quantum principle”? Logically, the answer is ‘No’, and I have showed that the space-time force has bigger ‘scope’ than the quantum principle. Now, we can summarize the above as below.
    a. Event horizon is defined with quantum principle.
    b. The quantum principle is derived with ‘space-time’ force.
    c. The space-time force of this universe is not bubble-dependent, and it arises from the dark energy (see http://prebabel.blogspot.com/2013/11/why-does-dark-energy-make-universe.html ). And, this dark energy mechanism defines the region where is beyond the ‘event horizon’.

    This dark energy mechanism can be verified empirically with some telescoping steps eventually. Yet, the above logic is the first step to refute any speculation which is beyond the immediate empirical verifiable ‘evidence’.

  26. [This is from Jim Baggott, who doesn't seem to be able to post directly on the forum.]

    Firstly, apologies for the radio silence. I’ve been travelling and playing catch-up, which is why I haven’t been able to respond to comments in real time. As I feel I’m at risk of writing a comment longer than my original article (which I’m sure nobody wants) I’m going to restrict myself to a select few remarks.

    Coel:

    “Do string theorists actually use the word “discovered” in this way? Aren’t physicists well aware that before string theory can be regarded as confirmed it needs some good empirical evidence and predictive success?”

    Yes they do. It’s not my intention to tar an entire community of theorists with the brush of one individual, but take a look at the debate between myself and British string theorist Mike Duff which was published in the Guardian newspaper last year: http://www.theguardian.com/science/2013/jun/16/has-physics-gone-too-far

    “But isn’t everyone well aware that in the end it needs empirical verification?”
    “We need to be careful not to misrepresent string theorists such as Brian Greene.”

    There are several posted comments along these lines (and thanks, imzasirf, for responding on the question of Greene’s tendency to be not very clear about the status of string theory). As we were setting up for the discussion on 30 May, I was treated to a sequence of TV film clips of Brian responding to this question, repeatedly declaring that he doesn’t believe string theory because it has not yet been experimentally verified. I’m not sure if this sequence was screened for my benefit (in case I had any ideas of confronting Brian on this issue). But in any case I was already aware of his well-publicised position. In the event, the sequence was not shown during the discussion.
    There are two things that worry me. The first is that, despite what Brian might say publicly, his (rightly) well-received popular books only serve to reinforce the mistaken view that these contemporary physical theories have the same or similar status to the quantum field theories used in the standard model of particle physics. Brian (and other authors) are quite adept at mixing a chapter on the bizarre (but experimentally verified) behaviours of quantum particles with a chapter on hidden dimensions in the Calabi-Yau spaces demanded by superstring theory. A reader has to be really quite familiar with these developments to know that a line has been crossed between two such chapters, from what in my book Farewell to Reality I call the ‘authorized version’ to speculative metaphysics. I myself was quite confused about the status of string theory until I read Peter Woit’s excellent book Not Even Wrong.

    The second worry is the growing tendency of string theorists and multiverse theorists to dismiss or at least downplay the importance of empirical verification (or falsification), captured in the quotes from Richard Dawid I included in my article.

    Disagreeable Me:

    “3) We may be blurring the line between physics and metaphysics, but unless you want to charge metaphysics with pointlessness this is not necessarily a bad thing as long as we make it clear what we are doing.”

    Totally agree. But those writing and talking about string theory are not making it clear what they’re doing. I don’t want to position myself as some kind of noble defender of the general popular science readership – even those within the scientific community responsible for making funding decisions are not clear what the string theorists are doing. I was invited to participate in the discussion by one such scientist (who will remain nameless) who does sit on funding committees, one who had read my debate with Duff and had gone on to read my book. He loved the book but criticised it for lacking in any real guidance for those making funding decisions (not actually my target audience, but still).

    C Lqrvy

    “Although I’m very sympathetic with the author’s main point, I don’t think he has a very adequate discussion of what constitutes “evidence.” All[ow] me to play Devil’s advocate. In what sense, exactly, does our current empirical data not serve as (perhaps inconclusive) “evidence” for these metaphysical theories?”

    I hadn’t wanted to get drawn into a detailed debate about the nature of empirical evidence, other than in terms of its broadly accepted, face-value meaning as a correspondence between theoretical predictions and accepted and established scientific facts (however arrived at). I’m well aware of all the pitfalls here, and do attempt to treat them in the opening chapter of my book.
    Here’s the situation, as I understand it. The standard model is a collection of quantum field theories which address three of the four fundamental forces – electromagnetism and the weak and strong nuclear forces. The force that is ‘missing’ is gravity. There is now no standard model prediction that has not been verified empirically. But the theory is very unsatisfactory, in that it requires about 20 parameters to be inserted ‘by hand’, their values determined by experiment. Among these parameters are the elementary particle masses.

    To make real progress I don’t need a new theory to make any novel predictions at all (by which I mean predict new phenomena a la Lakatos). I’ll settle for a new theory that predicts some (better still, all) the parameters that cannot currently be derived from within the standard model structure.
    Now, in its current form string theory takes us backwards. To make any physical sense, the strings have to possess a property called supersymmetry, and the simplest version of the standard model that incorporates supersymmetry requires an additional 105 free parameters in addition to the 20 we were already struggling with. Not surprisingly, with so much freedom the theory fails to make any hard-and-fast predictions. For sure, if nature is supersymmetric, then we should see a veritable cornucopia of new particles, supersymmetric ‘partners’ of all the particles in the standard model. Observing these would no doubt help pin down many of the free parameters, but theorists were predicting that these new particles lay ‘just around the corner’ already in 2000 and so far they still haven’t been seen. All is nevertheless well, the theorists claim, as they adjust the theory to predict supersymmetric particles that remain out of reach of the Large Hadron Collider.

    All the other developments in contemporary physical theory – M-theory, hidden dimensions, multiverse theory, and so on – simply stack more cards on top of a creaking structure, taking us further and further away from contact with empirical evidence of any kind.

    In no sense do current empirical data serve as any kind of ‘evidence’ (inconclusive or otherwise) for these metaphysical theories.

    Thomas Jones:

    “In your opinion, what practical measures might the community of theoretical physicists take to refind its way since it seems that many do not agree with your conclusion? Or is Massimo’s statement “free faculty lines, postdoc and graduate student positions, as well as research grants, to explore other options” a necessary first step?”

    Thanks for your kind remarks. This kind of question puts me in a rather awkward position, as I quit academia about 25 years ago and have only recently started receiving invitations to academic conferences and other events by virtue of my writing. However, at the end of the article I called for a time-out, and it’s reasonable to challenge me on what I mean by this. Here are a couple of thoughts:

    I’d like to counter the current drive towards ‘theoretically-confirmed-theory’ by introducing some philosophy of science classes early in the educational careers of science students. It has never ceased to amaze me how science students are supposed to pick up the essentials of whatever passes for the prevailing ‘scientific method’ within their chosen discipline by osmosis. In know this is complicated, and no two philosophers will agree on what constitutes a scientific method (or even if it exists), but an awareness and even partial understanding of the issues may make it much easier for students to differentiate more clearly between science and metaphysics.

    I’m pretty sure nothing whatsoever would be gained by it, but it might be an idea to try to clear the air through some kind of international conference or series of conferences to debate these issues. If there’s a consensus that we’re in ‘crisis’ (and I’m not sure there is), then small, perfectly-formed conferences have historical precedent as a potential solution. (I’m thinking of the post-war Shelter Island conference, which helped accelerate the development of quantum electrodynamics.) It seems to me that the ‘Evidence in the Natural Sciences’ symposium was a small step in this direction, but it involved experts sharing their perspectives rather than a concerted ‘workshop’ to acknowledge the nature of the crisis and evolve a new direction.

    And yes, those responsible for allocating funds and appointing new tenure-track academic staff aren’t lightweights. They should be monitoring these developments, coming to decisions about the viability of these research programmes and judging for themselves what the future holds. I’m just not close enough to this to have a feeling for how quickly change can happen.

    labnut:

    “Then there is a deeper problem, an ethical problem. The metaphysical anchor of science was a bone deep belief in the value of truth. We were not just pursuing the ‘reality of things-in-themselves’, we were also pursuing an ideal of ‘truth’. This ethical ideal shaped the way we conducted science. It dictated care, honesty, completeness, thoroughness, fairness and transparency. This, as much as empiricism, gave us confidence in science.”

    Amen. For truth, I read ‘correspondence truth’, a fundamental commitment to develop theories about nature that correspond to empirical facts we can discover about it. But, make no mistake, efforts to provide answers to the ‘big questions’ of human existence sell (they have always sold well). They sell to a broad readership, a TV audience, university faculty, funding agencies and even politicians. I think Danish historian Helge Kragh got it exactly right in his 1987 review of Barrow and Tipler’s The Anthropic Cosmological Principle, which I quoted. The ethical ideal is being sacrificed – consciously or unconsciously – in the interests of sales.
    I think that’s enough for now.

    • Mr. Baggott,

      I am afraid you are misrepresenting what string theory is all about. You claim that string theory makes no predictions and is untestable, but you don’t seem to understand that these claims require a huge amount of qualification to even make sense.

      A priori, string theory has nothing to do with the real world. It describes the behavior of strings in ten or eleven dimensions with unphysical supersymmetries. If you want to talk about whether string theory is “right” or “wrong” or “testable” or “untestable”, you first have to do a lot of work to develop a realistic model of our world. Otherwise your statements are so broad that they end up being completely meaningless.

      There are many different proposals about how string theory might be related to the real world. There are some models of physics based on string theory that been successful in explaining observed phenomena (here I’m thinking of models of the quark-gluon plasma and certain condensed matter systems). There are other models that currently being tested (for example models of axion monodromy inflation may receive a boost from the BICEP2 result), and there are many models that have already been ruled out (for example models involving large extra dimensions).

      Once you specify a particular phenomenological model, it makes sense to ask whether string theory is “right” or “wrong”. If you’re talking about string theory in general, it’s best to think of it as a formalism or framework that theorists can use to develop realistic models of physics. As far as I can tell, your claim that string theory is untestable or unscientific is based on an incorrect understanding of what the subject is all about.

      • MathPhys, no need to say things like “you don’t understand,” I almost blocked this comment because of it. Just focus on the actual points. Besides, I think Jim understands perfectly well, you just disagree on the implications.

      • Massimo’s right – I do understand. String theory’s historical roots lie in phenomenology (Veneziano amplitudes in meson-meson scattering). Of course there are string phenomenologists who are working to connect the structure with empirical reality. But I fear that the structure is inherently incapable of reconnecting in a way that doesn’t involve so many ad hoc auxiliary assumptions as to render any prediction meaningless.

        I can’t comment on quark-gluon plasma physics, but I’m wary of claims that string theory can be applied successfully in heavy ion and condensed matter physics. This, it seems, is not a view that is embraced by those scientists who have developed their careers in these subjects.

        • Mr. Baggott,

          I don’t think you’ve responded to any of my main points here. In your original post, you were claiming that string theory makes no predictions and is untestable. I pointed out that such statements are meaningless because the term “string theory” is too broad. It doesn’t refer to a specific model of fundamental physics but a vast theoretical framework.

          Do you disagree with this statement? If string theory is not a specific model of fundamental physics, then how are we to understand your claim that it is untestable? What does it mean to test string theory?

          I also pointed out that a particular model of string phenomenology may be perfectly predictive and falsifiable. Indeed, there are lots of stringy models of particle physics and cosmology that have either been supported or ruled out by experiments.

          Do you disagree? You say that “the structure is inherently incapable of reconnecting in a way that doesn’t involve so many ad hoc auxiliary assumptions as to render any prediction meaningless.” I’m not sure what you mean here. Can you give me an example of a string theory model that makes too many ad hoc assumptions to produce meaningful predictions?

          Finally, I pointed out that string theory has already been used to understand observed phenomena. You say this is not a view that is embraced by experts in heavy ion and condensed matter physics, but I can think of some very high profile scientists in these fields (such as Dam Son and Subir Sachdev) who have become strong advocates for the use of string theory in these areas. Do you disagree with any of the actual results in this subject?

          • MathPhysPhD,
            Perhaps one reason Jim hasn’t responded to your “QFT just as bad as string theory” argument is that you already made it at the top of this comment section, and I responded with the argument against it. Again:
            http://www.math.columbia.edu/~woit/wordpress/?wp_super_faq=isnt-string-theory-just-as-predictive-as-quantum-field-theory
            You just completely ignored this.

            As far as string theory and heavy-ion physics goes, perhaps you recall that one expert called for a “Pinocchio award” to Brian Greene when he claimed string theory as a good way to understand heavy ion physics. As far as I can tell, after an immense amount of hype, that idea is now pretty much dead: I don’t see anyone analyzing LHC heavy ion data using string theory based models. AdS/CMT is more promising, since there’s an infinity of condensed matter systems and thus more likely to be some where duality arguments are useful. I doubt you’re any more an expert about these than I am though, so no more able to evaluate this. I am an expert in string theory hype though, and these latest claims are often made by exactly the same people, in exactly the same way, as past ones (eg. heavy ions) that didn’t work out. Oh, and of course this has nothing at all to do with what Jim is discussing, speculative theories of everything based on string theory, not the application of qft dualities to condensed matter systems.

          • Mr. Woit,

            I have now posted a response to your comment at the top of the page.

            If you have any specific comments about the actual science involved in applications of AdS/CFT, I would be happy to discuss with you. Saying that these results don’t look useful doesn’t change the fact that they are applications of string theory to observable phenomena.

          • You can call me Jim (and, by the way, I also have a PhD).
            Confession. I don’t know what you mean by ‘stringy models of particle physics and cosmology’. Are these phenomenological models based on string theory that predict all the things that the standard model predicts? Better still, do they predict things that the standard model doesn’t predict? Apologies if I seem sceptical, because if they do I honestly believe I would have heard about these (the whole world would have heard about them) and we wouldn’t be having this debate.

          • Jim,

            String phenomenology is the subfield of string theory that attempts to create realistic models of fundamental physics using string theory. If you want to learn more about this subject, take a look at the following webpage, which includes a number of links to survey articles:

            http://ncatlab.org/nlab/show/string+phenomenology

            The basic idea here is to specify a shape for the extra dimensions so as to recover the standard model of particle physics coupled to gravity. Traditionally, this is accomplished by considering heterotic string theory with the six extra dimensions shaped like a six-dimensional Calabi-Yau manifold — but that’s not the only way of doing it, and there probably lots of ways that we haven’t even thought of yet.

            Are these phenomenological models based on string theory that predict all the things that the standard model predicts? Better still, do they predict things that the standard model doesn’t predict? Apologies if I seem sceptical, because if they do I honestly believe I would have heard about these

            The theories that you get by compactifying string theory on a Calabi-Yau manifold reproduce the general features of the standard model (its particle content, gauge symmetries, etc.) and consistently include gravity. The fact that string theory can do this is precisely why you’ve heard of it, and it’s why there was such a surge of interest in string theory back in the 1980s. In addition to the general features of the standard model, string compactifications give theorists the freedom to incorporate new features into their models, like supersymmetry, dark matter particles, and dark energy.

            In this way, theorists have developed lots of different models of cosmology and particle physics. These models are testable in principle, though in practice it may be impossible to test some of them because of the extremely high energies associated with quantum gravity. To give just one example of how these theories can be tested, let me point out that if the BICEP2 result is true, it will wipe out a whole swath of inflationary models based on string theory, while possibly supporting certain other models. And how could this possibly happen if string theory is a completely non-predictive idea as you suggest?

            The point is that predictions of string theory are model-dependent, and it makes no sense to ask about the predictions of string theory without specifying a particular phenomenological model. I should also point out that most string theorists don’t even work on phenomenology; string theory has tons of other applications to quantum field theory, quantum gravity, and pure mathematics. This means that you have to be even more careful when talking about predictions or testability of string theory as some of it’s applications have nothing to do with developing a theory of everything.

    • Hi Jim,

      Yes they do [use the word "discovered" in that way] … take a look at the debate between myself and British string theorist Mike Duff which was published in the Guardian newspaper last year:

      I’ve read it, and it seems to me that Duff does a good job of rebutting your arguments. As I read it he does *not* use the word “discovered” in the way that you suggest — namely that predictions of string theory are “discoveries” about nature, as in your phrase: “… they ‘discovered’ that elementary particles are strings or membranes”.

      What he does do is use the word “discovery” in the sense of “we discover that string theory predicts …”. That is not the same as implying “and thus we know that that is how nature is”. That implication is not there.

      E.g. this quote: “Similarly, string theorists did not assume supersymmetry, extra dimensions, the dualities of M-theory or the myriad possible universes; they discovered them to be consequences of a theory that …”.

      That is *not* saying that these things have been discovered about nature. It is simply explaining how theorists arrive at ideas like extra dimensions. From my reading of that discussion, Duff is well aware of the need for string theory to be empirically verified. What he is saying is that the time lag between the construction of theoretical models and empirical verification of those models can be long and uncertain.

      • I don’t claim that string theorists declare discoveries about nature. I charge them with a tendency to use the word ‘discovery’ rather loosely, in circumstances where ‘found’ or ‘implied’ might be more appropriate. The problem with the discovery word is that it is so easily misinterpreted to mean a discovery about nature.
        Read through Duff’s comment again and ask yourself how an average Guardian reader, with no formal training in science or philosophy, is likely to interpret it.

        • Hi Jim,

          Read through Duff’s comment again and ask yourself how an average Guardian reader, with no formal training in science or philosophy, is likely to interpret it.

          There seem to be two distinct issues here: (1) whether theoretical physicsts themselves have lost their heads over empirical verification and falsification, and (2) whether the wider public is confused or arriving at wrong interpretations. I’m not convinced on the former, though the latter may be the case in some instances (though of course at least half the public are going to assume that anything labelled a “theory” is speculative and unproven anyhow).

          • Yes, there are two issues here, but (1) makes it possible to position untested (and possibly untestable) theories as ‘progressive’ and (2) is the consequence.

  27. Hi Jim,

    The second worry is the growing tendency of string theorists and multiverse theorists to dismiss or at least downplay the importance of empirical verification (or falsification), captured in the quotes from Richard Dawid I included in my article.

    The quotes from Dawid are from a current philosopher of science (though former scientist) commenting on other people. So far no-one has quoted clear statements from current string theorists saying that they dismiss the need for empirical verification, or quotes that are problematic along these lines.

    I’ve given quotes from Brian Greene and Matt Strassler that indicate the opposite, that they are well aware of the need for empirical verification. At the moment I am not convinced that there is any problem in this regard. To me the theoretical physicists seem level-headed and sensible enough on the issue. I’m willing to change my mind, though, given actual quotes from a substantial fraction of current and prominent string theorists.

    • I can give you quotes from Greene’s ‘The Hidden Reality’ and Susskind’s ‘The Cosmic Landscape’ which hint in this direction (and these quotes are given in my book). Susskind in particular rails against the ‘Popperazi’, those in the community (and specifically Smolin) who hurl Popper’s principle of falsifiability and declare that string theory isn’t science. I prefer to quote Dawid as he is one of the few who clearly state the nature of the strategy being deployed here.

      Frankly, I doubt that you’ll find any working string theorist prepared to say openly that they don’t care about experimental verification, because this is simply not in their best interests. This doesn’t change the simple fact that it’s a lot easier to publish papers, attend conferences and build careers exploring the string theory landscape without worrying overmuch about whether any of this connects with empirical reality. This approach is justified using the familiar excuse, that this is the ‘only game in town’, combined with a seemingly inexhaustible optimism that ‘well, it still might be true’.

      Okay, there’ll be no Nobel prizes for this stuff, but if it can be established that ‘progress’ has been made through the establishment of what I call new ‘coherence truths’, such as the AdS/CFT duality, then there’s always the $3 million Milner prize…

  28. On behalf of those who appreciate a little logical consistency to go along with the speculation, I would like to raise a few points;
    According to both theory and observation, overall space appears close to flat. This means that what is expanding intergalactically is balanced by what is collapsing intragalactically. Now try as I might, no one has managed to explain to me why these two effects still result in an overall expanding universe.
    It seems quite logical to assume these are two sides of a larger cycle of expanding radiation, balanced by collapsing mass, which then appears to radiate it back out. Yes, the light from very distant sources is redshifted, but it necessarily only travels those intergalactic areas which would be expanded. It would be as if we put the rubber sheet and a ball analogy of gravity over water, so that when the ball pushes down in one area, the water pushes back up by an equal amount in other areas.
    This would fit rather effectively with Einstein’s cosmological constant, which was introduced for the very purpose of balancing the contraction of gravity.
    Light apparently does travel as a wave, not particles and so do we really fully understand how it is affected, stretched, distorted over intergalactic distances?
    I raised another issue in an above post, that the expansion is proposed as the expansion of space itself, rather than simply an expansion in space, to explain why we appear at the center of this expansion. Yet the argument then goes that these distant galaxies will eventually disappear, as they recede faster then the speed of light. This effectively proposes two concepts of space; That measured by a stable speed of light and that which is expanding, as measured by the redshift of this very light! Now the realm of quantum math may not have much respect for basic mathematical principles, but if you are using a stable unit to define a variable quantity, then the stable unit is your denominator and the true measure of the substance in question. It would seem there is some underlaying dimension of space, as defined by lightspeed, which is simply taken for granted.
    Now if expansion and gravity are opposite effects and gravity lenses light, this does not actually move the source of this light, but only warps its passage, so possibly the same is true for expansion; That this is an optical effect and that would very effectively explain why we appear at the center of this expansion, since we are at the center of our view of the universe.
    I realize I’m being a bit of a party pooper here, but this might be an interesting article for those willing to go against the rush to multiverses;
    http://www.americanscientist.org/issues/pub/2007/9/modern-cosmology-science-or-folktale

    • According to both theory and observation, overall space appears close to flat. This means that what is expanding intergalactically is balanced by what is collapsing intragalactically.

      Sorry, but no it does not mean that.

      • Coel,
        I would be more than happy to hear what it does mean. In the basic world I live in, 1+(-1)=0.
        As far back as reading Hawking’s A Brief History of Time, when it came out in ’89, that is what was described, that gravity and universal expansion are inversely proportional.
        Yes, everyone continues to see the overall universe as expanding, yet Einstein did describe gravity as the contraction/inward curvature of space and proposed a cosmological constant to balance it. Then is is discovered the space between galaxies expands.
        So it seemed to me that if what expands between galaxies is equal to what falls into them, then there would be no extra expansion.
        Sorry to be so simple minded, but I’m just not seeing how it is these two effects are not canceling each other out.
        If redshift is an optical effect, it would logically compound and so there would be that curve upward, with distance. Big Bang theory seemed to assume the cooling from the singularity was even and so was surprised to find it dropped off, then flattened out to a residual expansion, which has now been attributed to dark matter. Now this has been called similar to a cosmological constant.
        It’s not like I make my living at this, but I like to try and make sense of the reality I inhabit and with multiverses, it seems like the train must have left the station awhile back.
        Regards,
        John

  29. Jim,
    For truth, I read ‘correspondence truth’, a fundamental commitment to develop theories about nature that correspond to empirical facts we can discover about it.
    Yes, that is what I mean.
    But I also mean truth as a virtue, as in truthfulness, veracity, honesty. There is a dualism in the word. On the one hand we have correspondence truth and the other hand we have virtuous truth. Virtuous truth describes the manner of the truth seeker’s conduct. I maintain that the two are closely linked. We cannot reliably seek correspondence truth without a prior commitment to virtuous truth.

  30. Why the hyper-focus of philosophers with the most extreme and speculative physics and cosmology? There is so much other evidence-based knowledge and “science” to engage with. Extreme physics and cosmology has zero practical application and usefulness.

  31. To me the concept of being clear is crucial. For example this quote:

    In fact, many universes exist with many different sets of physical laws. Some people make a great mystery of this idea, sometimes called the multiverse concept, but these are just different expressions of the Feynman sum over histories.

    The Grand Design – Stephen Hawking, Leonard Mlodinov

    appears to be stating this as scientific fact whereas it is really a fringe version of an untested theory piggy backing on a well tested approach to quantum physics.

    The book ends with the statement about M Theory “… if it is confirmed by observation …” but it is never made clear how much of what is stated in the book has this status.

    This seems to be quite common, to state conjectures or untested theories as scientific fact, or almost-confirmed scientific fact.

    For the layperson it is difficult to know where the confirmed science ends and the conjecture begins.

    For me it makes most new statements by physicists all but useless.

    • Hi Robin,

      That quote from the Grand Design is taken out of context. The paragraph you quote from actually starts with the disclaimer “In this view”. I would interpret them as explaining one particular view of universe creation, not asserting it as truth.

    • Hi Robin,

      This seems to be quite common, to state conjectures or untested theories as scientific fact, or almost-confirmed scientific fact.

      I really don’t think this is fair, and so far no-one has produced solid examples of this. For example, your above Hawking quote has “In this view …” earlier in the paragraph in a way that clearly applies to the succeeding sentences.

      When one is writing readable prose one cannot put all the caveats and presumptions in every sentence, one needs to be able to expound on a speculative scenario. Particular quote-mined sentences can then be out of that context.

      • Hi Coel and DM,

        You accuse me of quote mining but it is not quote mining if that is how I understood it.

        I had already considered and rejected the idea that “In this view” was meant as a disclosure that this was speculative, I rejected the idea from the context of it.

        I have read it again and it still doesn’t read that to me, He does not appear to be saying that “this view” is highly speculative, on the contrary and in the context of all else they say about the “sum over histories” approach it sounds like they are saying that this “this view” is the correct “view”.

        This is reinforced by the use of the words “In fact”. It would not detract from the readability if they had said something like “If this were the case then there would be many universes with many sets of physical laws”, On the contrary it would have clarified their meaning, if that was their meaning.

        Moreover he says in the next sentence that “this idea” (ie “many universes exist with many different sets of physical laws”) is just a different expression of the Feynman sum over histories.

        He has spent a lot of time pointing out the solidity of the “sum over histories” approach.

        Now I am not sure how you break on the idea that many universes with many different sets of laws is an expression of Feynman’s sum over histories.

        But to say that something is “just an expression of” solid science, sounds as though they are implying that it is also solid science.

        • Hi Robin,

          Moreover he says in the next sentence that “this idea” … is just a different expression of the Feynman sum over histories. [...] But to say that something is “just an expression of” solid science, sounds as though they are implying that it is also solid science.

          But while that Feynman sum-over-integrals is solid science in some applications, whether it has any validity as applied to the origin of the universe is hugely speculative. Vast swathes of that book are highly speculative, and one couldn’t keep repeatedly including lots of caveats and cautions about this without it being unreadable prose.

          One could of course say that someone of Hawking’s statute should not speculate in public like this, because the public cannot tell what is and is not speculation, and that is a fair point and criticism to make. But is it really a problem? Should we hide cutting-edge speculation from people even though they are interested in it? It’s not as if it is about the efficacy and safety of a novel drug, or about the science of global warming, where things have serious consequences for society.

          • That’s right, one could state that public intellectuals like Hawking, Greene, etc ought (morally) to be careful about what they present to the public and how. It is a question of integrity, as well as of the reputation of science itself, already fairly battered in the United States.

          • That comment may explain some of the difference in opinion, since on this side of the Atlantic we don’t have the anti-science “religious right” of the US (at least, not nearly to the same extent). The public here seem pretty ok with reading about speculative cutting-edge science and I don’t see that as a problem.

            I can see why things like creationism and climate-change are contentious, but I’m unclear on why string theory would be a political issue. In the UK the reputation of particle physics is currently pretty high, owing to Higgs and Brian Cox, and there isn’t really a popular issue over string theory.

          • Coel, you may be underestimating the anti-science crowd in Europe (think anti-GMO, low levels of acceptance of the idea of climate change, etc.). Moreover, I think a scientist who engages in public intellectualism has an ethical duty to explain things clearly and honestly regardless of where he happens to live on the planet.

          • Hi Massimo,
            I don’t think that the UK has the anti-science attitude of the US. On GMOs, most of the public accept the science but are dubious about the risk/benefit equation. On climate change, most in the UK accept the science but are fatalistic about what can be done about it. Overall, promotion of cutting-edge physics (even when gee-whizz speculative) is very much on the plus side for the public standing of science.

          • Coel, I think you may be underestimating the problem, especially in the UK. Newspaper articles and surveys I’ve read over the last few months put acceptance of climate change, for instance, at almost US levels (not a good thing). As for GMO, not accepting that the science pretty clearly says there are little or no health risks is, well, not accepting the science! (On a side note, I’m critical of GMO usage for other reasons, that have more to do with the politics of farming.)

          • Yes, there is a deep, pervasive and increasing distrust/fear of any evidence-based knowledge (“science”) which challenges existing power structures and cultural norms and beliefs in the US. All good “science” challenges existing beliefs and myths, of course.

            This has increased as reactionary forces/money now control all public dialogs and media. ANY mention of “science” is now readily attacked, including in Congress, where the goal is to silence knowledge exchange. And it has worked – climate denial, vaccines, anti-evolution, etc.

            In addition, 80% of Americans believe: Satan is a living being and in ghosts, guardian angels. miracles and that the government is hiding evidence of alien visitations.

          • Coel,
            I don’t think that the UK has the anti-science attitude of the US.

            Then you should read Damian Thompson’s book Counterknowledge(http://amzn.to/1n7KATU). The problem is much bigger than ‘anti-science’ and is far more pervasive than you seem to understand. I earnestly urge you to read this book so that you understand why we should not feed this dangerous counterknowledge movement by indulging in unfounded speculation.

            By the way, have you read Jim Baggott’s book? I asked this in an earlier comment and got no reply. If you want to seriously engage with his ideas you should read his book, otherwise your objections will be ill informed. It really is worth reading.

          • Coel,
            (even when gee-whizz speculative) is very much on the plus side for the public standing of science

            No it is not, it is very damaging. To understand why you should read the final chapter of Damian Thompson’s book, Counterknowledge, where he make a profound analysis of what is going wrong.

          • Hi labnut,

            No it is not, it is very damaging.

            Can you give actual documented examples of damage done by “promotion of cutting-edge physics (even when gee-whizz speculative)”?

            My comment was specifically about the UK, but I’d be interested in examples from elsewhere also.

          • Coel,
            once again, my advice stands. Read Damian Thompsons’s book. And while you are about it you really should read Jim Baggott’s book. Naturally, you should augment that reading, as Massimo advises, with the books by Lee Smolin and Peter Woit.

          • Coel, when you ask about “documented” damage, do you actually want empirical studies to prove the point? If so, it seems to me you are raising the bar a bit too high for a discussion in a forum like this one. The hinted damage is at the credibility of the scientific enterprise: “oh, those scientists, one day it’s multiverse, another it’s climate change. They really can’t be trusted with solid truths.” There certainly are plenty of examples of this sort of attitude in the media and the public at large. How widespread it is and how damaging (in terms of what? Money? Reputation?) it is remains an open empirical question. Got any student who would like to pursue it as a PhD project?

          • Hi Massimo,

            The hinted damage is at the credibility of the scientific enterprise: “oh, those scientists, one day it’s multiverse, another it’s climate change. They really can’t be trusted with solid truths.”

            Yes, examples of that sort of comment in mainstream or semi-mainstream media would answer my question. From the perspective of the UK (which I made my comment about), I don’t recognise that sort of comment about *physics*.

            Climate change, yes. Medical stuff (e.g. whether wine is beneficial) , yes. GMO, yes. Autism/vaccinations, yes, though largely died out now.

            But physics, or specifically string theory, the multiverse, Hawking’s books, any of that stuff, well, no, I’m not aware of anything such. If you mention any of this stuff in the UK these days they think Higgs, LHC, British Nobel Prize, and Brian Cox, all of which they generally regard positively.

            That’s in the UK. If this is a negative issue in the US then that’s interesting.

          • I see the issue. I wasn’t saying that people in the UK (or the US) see fundamental physics the way they see climate science. I was saying that enough damage has been done/suffered to/by science in general that we don’t need to add more sloppy sensationalism in yet another scientific field to the mix. And there is the (separate) question of the ethics of public intellectualism, regardless of consequences.

          • Coel,
            to add to what Massimo says(much more clearly than I could!).
            Naomi Oreskes, in her book, Merchants of Doubt, makes the strong point that certain industries manipulate compliant scientists to advocate alternative narratives. They then publicise these alternative narratives widely. The intent is to create doubt in the public’s mind and thus delay, minimise or prevent adverse legislation. This is damaging in its own right. But there is a knock on effect where the image of science itself suffers. When prominent figures in science start to lend their names to dubious hypotheses they tend to weaken the image of science still further. This plays right into the hands of the merchants of doubt. And that causes very real damage.

            You asked for references and I have given you two substantial references, Counterknowledge and Merchants of Doubt.

          • Hi labnut,

            You’re entirely right about some industries. Those related to medical science (drugs), the food industry (sugar in food etc), and smoking, are all examples. All of these have immediate implications for the public.

            I’m not sure that theoretical physics is at all in the same boat, simply because none of this has actual consequences for society.

            By the way, I wouldn’t trust Damien Thompson an inch given various other stuff of his that I’ve read, and it’s highly ironic that he talks about a “pandemic of credulous thinking” given his strong Catholic beliefs.

          • Coel,
            By the way, I wouldn’t trust Damien Thompson an inch … it’s highly ironic that he talks about a “pandemic of credulous thinking” given his strong Catholic beliefs.

            To smear somebody because they hold religious beliefs is a very poor tactic. It is nothing but blatant prejudice in an age when we should be discarding prejudices. His arguments should be examined on their own merit and nothing else. I am truly surprised that you should prejudge him in this way. As a matter of fact he never once brings his religious beliefs into the book, but you will never know that since you have prejudged him.

            I am a devout Catholic. If that makes my arguments untrustworthy then I invite you to stop interacting with me.

          • Guys, I’d say keep religion out of it. Speaking of which, signing off to see the World Cup opener…

          • Hi labnut,
            As my comment stated, I had read other things by Thompson, and that is how I formed my opinion of him.

            The comment about his religious beliefs was about the irony of him excusing them from being part of the “pandemic of credulous thinking”, which he does in his book.

            Anyhow, his book is a run though of all the usual pseudoscientific stuff, which is worthy but not all that novel.

            I am a devout Catholic.

            I had guessed! By the way, are you objecting to scientists discussing speculative stuff in public at all, or are you just complaining that the disclaimers labelling it as speculative are not prominent enough?

          • Coel,
            The comment about his religious beliefs
            this is plainly irrelevant and you had no business dragging it into the conversation.

            all the usual pseudoscientific stuff, which is worthy but not all that novel.

            Usual or not, novel or not, that is simply beside the point. What is important is that he documents a dangerous process that is infecting society. He does it in a clear, insightful way and you should carefully consider its implications.

            If you read the final chapter and understood his thesis about the underlying cause you would see that it is far from usual.In fact it is a very insightful explanation that we should be carefully considering.

            Massimo has explained the issue clearly. What he has said is transparently obvious and I have no more to add to that.

          • Hi labnut,

            this is plainly irrelevant and you had no business dragging it into the conversation.

            The author’s credulous thinking is relevant to a book about a “pandemic of credulous thinking”.

            … his thesis about the underlying cause …

            So what is his thesis? And, is this sort of pseudoscience actually getting worse, or is it much as it always has been?

          • Coel,
            The author’s credulous thinking is relevant to a book about a “pandemic of credulous thinking”.
            No!
            A book should considered on its own merits. If you refuse to consider a book on its own, intrinsic merits then you are giving away to blatant prejudice.
            That is your choice but if you give way to prejudice you won’t see much of the world besides a narrow, blinkered view.

            Yes, the counter-knowledge movement is getting worse. But don’t take my word for it, read the book.

          • Guys, I think this needs to be toned down a bit, or I’ll start filtering stuff… Cheers!

        • To be clear, Robin, I wasn’t accusing you of quote mining. I only meant to say that the interpretation of that paragraph could be taken quite differently if you included “In this view”, and indeed my interpretation is quite different from yours.

  32. Rather than evidence for inflationary cosmology, could the cosmic background radiation be simply a base quantum state and its smooth temperature of 3.7k would be a phase transition of some sort?
    It does seem to be a very basic data point, for which there has been minimal effort to explain, other than as residue of the Big Bang, which then needed inflation to explain its other properties.
    This does go to the other debate here, how our conceptual limitations/definitions and prior models become the filter though which all succeeding evidence must pass. The term ‘shoehorn’ comes to mind.

    • could the cosmic background radiation be simply a base quantum state and its smooth temperature of 3.7k would be a phase transition of some sort?

      The Big Bang origin of the CMB has oodles of evidence going for it. The existence of the CMB and its temperature were early predictions of Big Bang cosmology. It ties in very well with lots of other aspects of Big Bang cosmology that are also strongly supported by evidence (e.g. Big Bang nucleosynthesis). The cosmological origin of the CMB also meshes with other aspects of astrophysics, such as the Sunyaev–Zel’dovich effect.

      By all means try to overturn the Big Bang model, and produce an entirely different explanation of the CMB, if you wish, but there are a large number of strong observational findings that you then need to account for at least as well as Big Bang cosmology does.

      And then you have to show that your model explains the spectrum of fluctuations in the CMB at least as well as inflationary BB does.

      (By the way, some anti-Big-Bang astronomers such has Narlikar and Hoyle did try to explain the CMB in other ways, but the general opinion is that they got nowhere.)

      • Coel,
        I realize a lot of these pieces seem to fit together quite neatly, but there are some large gaps which seem to get swept under the rug after a few decades and then everyone assumes the problem is solved and moves on. Specifically I’m referring back to my original point about time. To restate it; “We experience change as a linear sequence of events and so think of time as the point of the present moving from past to future, which physics then distills to measures of duration between events, to use in models and experiments. This being the basis of the geometry of spacetime, given clockrates vary in different conditions.
        The basic reality though, is that the changing configuration of what is, turns future into past. To wit, tomorrow becomes yesterday because the earth turns, rather than it traveling a meta-dimension from yesterday to tomorrow.
        This makes time an effect of action. Which makes it much more like temperature, than space.
        Basically time is to temperature, what frequency is to amplitude. It is just that with temperature, we experience the cumulative effect of lots of individual velocities/amplitudes and so think of it as an effect, while with time, we personally experience the individual sequence and assume there must be a universal rate, yet only experience the cumulative effect. Just like temperature is a cumulative effect.
        A faster clock only burns quicker and so falls into the past faster. The hare is long dead, yet the tortoise plods along.”
        As it is, the current inclusion of time into this four dimensional geometry of spacetime not only creates large issues, such as blocktime and not being able to explain why it is asymmetric, but it is another factor where it disagrees with QM, which uses a single external clock.
        If we simply view time as a measure of action, ie, frequency and not as some meta-dimension, then there is no blocktime. Its passage is asymmetric due to simple inertia, ie. the planet is not going to stop spinning and go the other direction. The future is not deterministic, nor does the past remain probabilistic ie. multiworlds, since probability precedes actuality. To wit, there are ten potential winners before a race and one actual winner after it.
        Above all, it makes time the dynamic effect of creation and dissolution we all experience, not a static dimension of events.
        The problem for cosmology is that this means spacetime is only a mathematical model, like epicycles and the ‘fabric of spacetime’ is no more physically real than those giant cosmic gear wheels.
        So it leaves no conceptual basis for an expanding universe. Space is simply the void. That vacuum across which light travels at C. Which gets to another point I made, that no one addressed; “the expansion is proposed as the expansion of space itself, rather than simply an expansion in space, to explain why we appear at the center of this expansion. Yet the argument then goes that these distant galaxies will eventually disappear, as they recede faster then the speed of light. This effectively proposes two concepts of space; That measured by a stable speed of light and that which is expanding, as measured by the redshift of this very light! Now the realm of quantum math may not have much respect for basic mathematical principles, but if you are using a stable unit to define a variable quantity, then the stable unit is your denominator and the true measure of the substance in question. It would seem there is some underlaying dimension of space, as defined by lightspeed, which is simply taken for granted.”
        So why, if space is expanding, wouldn’t the speed of light increase proportionally, in order for it to remain constant to this expanded space? Of course, if this was so, we wouldn’t be able to detect that expansion, as the increased rate of propagation would cancel the redshift.
        Now it’s easy to just tell me it isn’t so and leave it at that, but eventually people are not going to keep buying these patches need to sustain the current model.
        Regards,
        John

  33. This article is as nicely-written as it is biased to the point of defeatism. So much so in fact, that its main lines of thought (“It’s all gone to math”; “Ah, the math with it!”; “Math rises!”; “Heaven v. Math”, etc.) can be dismantled using a single quote by the very guy the article glorifies for his ability to come back after crossing into the “metaphysics realm”: Albert Einstein and his famous “A mathematical equation stands forever”.

  34. My last comment seems to have gotten eaten by WordPress, so here goes again.

    From the standpoint of someone in this field, there seem to me to be two incompletely addressed issues at play here.

    (1) Experiment has slowed to a crawl.

    We are only just now — decades after it was proposed — confirming the existence of a Higgs-like particle at the LHC. And so far it appears to be a vanilla Higgs doublet, with no hint or evidence of exotic physics whatsoever. No signatures of dark matter. No hint about neutrino masses. No signs of supersymmetry, or extra dimensions, or low-energy effects from quantum gravity.
    This isn’t just Nature being stingy, by the way. We should have seen the Higgs twenty years ago — a whole general of physicists ago — had the SSC not been canceled. The SSC would have been more powerful than the LHC and maybe seen exotic physics beyond the Higgs, but, in so small part due to public infighting between high-energy and low-energy physicists over funding dollars, the project was cancelled by Congress in the early 1990s. Starving high-energy physics of data badly damaged a whole generation of high-energy physicists, and it wasn’t their fault or the fault of hiring committees or of fads or of psychological or sociological factors.
    What do you do when there’s no reliable data coming in for so many years?
    The fact is that there are lots of young, bright people who are interested in high-enegy theory. What do you recommend that they do? Become condensed-matter physicists? Please tell me, concretely, what you would suggest they do.
    It’s easy for people outside the field to say that they should just go back to the drawing board and come up with new ideas that could lead to alternative tests that bypass big accelerators, but you try doing it!
    A big part of the difficulty is…

    (2) The field has calcified due to a minefield of known constraints, previous empirical results and data, no-go theorems, and other experimental and mathematical obstructions.

    There’s a popular image that high-energy theorists just come up with whatever they want and it becomes a new fad. That’s not quite right. From years of gathering data and probing the deep structure of the models and frameworks we know and trust — quantum mechanics, quantum field theory, general relativity, semiclassical quantum gravity, cosmology — we already have a huge number of constraints on what one can propose. Almost any idea one could propose gets cut down almost instantly because it runs into one of these obstructions. (It’s often fun watching this happen in seminars, for example.)
    So telling young physicists just to go home and come up with new ideas from scratch sounds great in words, but it’s a fatal suggestion, and not because of a cabal of tenured professors who will kill their career. It’s because you’ll never get anywhere with that approach. It just doesn’t work. Years will go by with nothing to show for it.
    Lots of people in the field spend part of their time working with alternative ideas on the side, and they never go anywhere, because they can’t make it through that minefield of constraints. They violate something — flavor-violation constaints, gauge invariance, locality, Lorentz invariance, unitarity, renormalizability, cancellation of gauge anomalies, black-hole physics, big-bang nucleosynthesis, accommodating chiral gauge groups, the litany of no-go theorems like Coleman-Mandula — and that’s just the tip of the iceberg!
    What’s amazing is that we have any ideas at all that have managed to slip past all these constraints, and basically the only one is string theory and ideas that have been spun out of string theory. String theory is the one model we have in which physics is self-consistent all the way to the Planck scale, and incorporates gravity into a quantum theory in a consistent way without violating all the many constraints we know about.
    I know lots of people in the community, and nobody says string theory is an accurate description of the world in the absence of some kind of experimental data. And lots of people are looking for lucky accidents that might make it into an experimental science. Indeed, Einstein was very lucky that our solar system has two very helpful features — a moon whose apparent diameter in the sky is the same as the sun (which made that Eddington eclipse experiment possible) and the planet Mercury (which was close enough to the sun that we can detect its orbital anomalies). Without those lucky accidents, general relativity might not have been an experimental science for decades. It would have been beautiful mathematics, but little else.
    So what string theorists are hoping for is a lucky accident. Maybe some signature in the CMB, for example. If the BICEP2 results hold up (an uncertain prospect at this point), then that would at least get in the ballpark of where quantum gravity should become noticeable.
    In the meantime, a lot of people use string theory like a crystal ball or a “theory-generating function” that spins off other ideas that, due to their origin in string theory, likewise survive all those constraints. Supersymmetric models, extra-dimensional models, various dark-matter models, etc., own much of their origins to string theory, but are conceptually independent of string theory and could be true even if string theory turns out not to be.
    And there are lots of formal techniques that came out of string theory — holographic techniques for studying quark-gluon physics or condensed-matter systems, scattering-amplitude methods for computing cross sections to study LHC data — that have been useful as well.
    That’s why people have stuck with string theory, looking for new ideas to spin off or studying dualities and the internal structure of the theory in the meantime. It’s not primarily because it’s a fad or because of sociology, but because string theory is the only thing we have that can generate this stuff without running into that minefield of constraints. People continue to try (and fail) to find alternatives, but it hasn’t been done yet, and might end up being impossible. (For example, if you think loop quantum gravity hasn’t gotten a fair shake, then you really need to study those constraints better.)
    So I ask you — what do you expect high-energy theory people to do? Please tell me concretely. Perhaps some of the armchair-physicist bloggers would be willing to put down their blogs for a few months and try it out for themselves rather than yelling criticisms from the sidelines.
    I agree that this discussion might mean that high-energy physics has a serious problem. I would just be more careful about pointing the blame at the people themselves.

    • ns12345,
      I mostly agree with your diagnosis of the situation: we have no experimental guidance, and no good ideas about how to go beyond the SM, as well as a lot of experience with ideas that don’t work and the general principles why.

      This is a very tough situation for the field to be in. I think you’re ignoring though the argument that some leaders of the field have chosen to deal with this not by acknowledging the situation, but by trying to make the problem go away by abandoning the conventional constraints of science. It’s easy to find prominent theorists going on publicly about how these are wonderful times, great progress is being made, the anthropic string theory landscape explains it all, etc. Someone should be providing a reality-check to this nonsense, and I don’t think you should be complaining when they do it unless you’re someone who has done your part publicly yourself.

      I also disagree with the idea that the string theory TOE idea is the one left that hasn’t hit a no-go theorem, so that’s a reason to keep doing it. The string theory landscape shows that this idea has failed, just like others, and there is no more reason to pursue it than other failed ideas. Yes, if you keep at an idea despite it not seeming to work, you may someday find a way around the problem, and in an environment of only ideas that don’t work, you’re stuck doing this. The problem is string theory TOE is the one failed idea that you can make a successful professional career pursuing, with lots of people to work together with. It’s the one that has a get out of jail free card, and we’d be better off if that was revoked.

      As a more positive comment, I think we do have some experimental guidance: the SM is a lot better than anyone ever thought. The discovery and properties of the Higgs seem to indicate it’s a valid theory up to absurdly high scales. It would seem to me that highest priority should go to trying to understand those aspects of it that we don’t now really understand. A couple examples are confinement and the non-perturbative behavior of the electroweak sector. Yes these are extremely hard problems, but we need to find ways to make it professionally legitimate for young theorists to work on them (and not just by themselves, in their spare time, but as their full-time research, with a sizable group to work with).

      • You write: “This is a very tough situation for the field to be in.” I agree.

        You also write: “I think you’re ignoring though the argument that some leaders of the field have chosen to deal with this not by acknowledging the situation, but by trying to make the problem go away by abandoning the conventional constraints of science. It’s easy to find prominent theorists going on publicly about how these are wonderful times, great progress is being made, the anthropic string theory landscape explains it all, etc.”

        I agree with this, but what I don’t agree with is the often implicit conclusion that the way to “fix” the problems in the field is to prevent leaders from behaving this way. It is true that people shouldn’t be pretending everything is just great and selling tall tales, but even if we get them all to stop (and it’s actually not the majority of them — most people are really low key), that doesn’t change the “tough situation” at all. And it’s sometimes frustrating when it seems like critics think that if we can just keep people from being bombastic then we’ve made real progress. That’s treating a symptom, but not the cause.

        Again, however annoying some people in the field may or may not be, that’s not the ultimate cause of these problems. That’s why I am dismayed when I hear the blame get placed on the human beings here, as if they’re responsible for the *real* problems in the field today.

        I don’t agree with your next statement: “I also disagree with the idea that the string theory TOE idea is the one left that hasn’t hit a no-go theorem, so that’s a reason to keep doing it. The string theory landscape shows that this idea has failed, just like others, and there is no more reason to pursue it than other failed ideas.”

        There is absolutely no no-go theorem (no^2-theorem?) that prevents us from finding a vacuum whose low-energy physics matches on to the Standard Model. Indeed, lots of people are currently looking for one! It’s just a hard problem to find such a vacuum, because the landscape is so huge.

        That means string theory has a huge leg up on every other idea that we’ve tried. The others clearly break. That’s one reason people use string theory as a “theory-generating function,” because the ideas it spits out don’t crash fatally into no-go theorems and all the other constraints. Like I said, starting from scratch and trying to navigate around the minefield of constraints is unimaginably hard, and hasn’t led to any progress in many decades, despite the fact that many people have certainly been trying them. Indeed, in the few cases where it looked like there might be progress (e.g., 11d supergravity), the result turned out to be a part of the string theory landscape!

        You write: “It’s the one that has a get out of jail free card, and we’d be better off if that was revoked.” I disagree. Without string theory and ideas it has generated (and other related ideas that you don’t like), we have essentially nothing to go on for physics beyond the standard model. Years of trying other approaches has yielded nothing that survives all the constraints. That’s why so many people try to spin ideas out of string theory, because at the very least we know we’ll avoid running into all those constraints.

        Like I said, it’s easy to declare that people should just start from scratch, but then what do we actually do, concretely? I get so bothered especially when I hear this from people totally outside of high-energy physics, as if they have any idea what they’re talking about. (Try it yourself!, I always say.)

        You write: “The discovery and properties of the Higgs seem to indicate it’s a valid theory up to absurdly high scales. It would seem to me that highest priority should go to trying to understand those aspects of it that we don’t now really understand. A couple examples are confinement and the non-perturbative behavior of the electroweak sector.”

        Those are indeed valid areas of inquiry. It’s just that people have looked at them both for many years and they haven’t borne much fruit. They haven’t pointed the way, or revealed anything about clear questions like dark matter or neutrino masses, let alone more exotic questions. Maybe we need to work on them more! Or maybe they’re dead ends. What’s interesting to note is that supersymmetry has been the most promising road to a lot of this stuff: N=2 SYM has taught us a lot qualitatively about confinement, for example.

        • Ah, the ‘you’re not qualified to hold an opinion’ argument. So the only people qualified to criticise a discipline are its own practitioners? Sorry, I don’t buy it. Especially when there’s a growing sense that some of these same practitioners are trying to bend the rules to lend validity to what they’re doing.
          I think the point Peter is making is absolutely right. When the LHC comes back on stream next year with a collision energy of 13 TeV we’ll hopefully have an opportunity to explore the Higgs sector in great detail. Perhaps this is also an opportunity to calm our over-eagerness and rein in our ambitions. Let’s see what we can learn by sharpening the theoretical underpinnings of our understanding of physics at this energy, and forget for a while about dark matter, dark energy and quantum gravity. I suspect that this would be a lot more productive in the short run although, of course, it wouldn’t make quite such spectacular headlines.

          • You write: “So the only people qualified to criticise a discipline are its own practitioners? Sorry, I don’t buy it.” My apologies, but you haven’t constructed an argument here. Saying you don’t buy it isn’t an actual argument.
            Look, it would be nice if people without expertise in a field were always capable of providing helpful criticism. But it is a plain fact that some subjects simply require a lot of technical knowledge and expertise in order to understand why the practitioners are doing the things they are doing and why they’re stuck.
            Some of your criticisms of the field sound fine — the lack of experimental data being a huge issue, for example — but other of your criticisms speak to a lack of awareness of what is actually going on right now in theoretical physics and what people internal to the field are actually talking about and what their motivations and difficulties are.
            I can speak to this from personal experience, as someone who entered the field not a very long time ago. My own impressions changed a lot between not really knowing the tools of the trade (but reading a lot of things written by folks such as yourself) and then later learning those tools and getting to hear what was actually going on among the people working in the field.
            So when you also write “Especially when there’s a growing sense that some of these same practitioners are trying to bend the rules to lend validity to what they’re doing.”, again, the reason this sounds like a comment from someone who doesn’t really understand what’s going on in the community of high-energy theorists is that while it’s definitely a *symptom* of a deeper problem, it’s simply not the *cause* — see points (1) and (2) of my earlier post.
            Getting people to keep quiet with all the flamboyant rhetoric, while making everyone’s lives less annoying and giving news reporters less exciting stuff to write about, will do absolutely nothing to fix either points (1) or (2), whereas if (1) and (2) were solved, then the flamboyant rhetoric wouldn’t be an issue anymore.
            Now, if you or anyone else inside or outside the high-energy community has concrete proposals that would truly solve either of these two fundamental problems — (1) the crushing lack of experimental data and the slow rate of experiments, and (2) creating new ideas that can successfully navigate the maze of known constraints to go beyond what we already know in the Standard Model and perhaps explain many of the remaining mysteries and even suggest new experiments to be performed — then people will be all ears. But just telling some of the louder members of the community to keep quiet isn’t going to be very well-received by folks in high-energy, and for good reason, because it doesn’t actually solve the basic problems.
            You also write: “When the LHC comes back on stream next year with a collision energy of 13 TeV we’ll hopefully have an opportunity to explore the Higgs sector in great detail.” Hope springs eternal! Nothing would make people in the high-energy community more excited than new data that points a clear path to physics beyond the Standard Model. If we do, then that would partially solve problem (1) all by itself, bombastic rhetoric or not.
            But so far we’ve found nothing of this kind, and there’s a fair chance that we won’t even after the LHC goes up in energy. So then (1) stays unresolved, and what do high-energy physicists do? Perhaps your answer is along the lines of your other comments: “Perhaps this is also an opportunity to calm our over-eagerness and rein in our ambitions. Let’s see what we can learn by sharpening the theoretical underpinnings of our understanding of physics at this energy, and forget for a while about dark matter, dark energy and quantum gravity. I suspect that this would be a lot more productive in the short run although, of course, it wouldn’t make quite such spectacular headlines.” Actually, this is already going on. People are working on non-exotic physics. And they are learning some stuff. There are a lot of people working on jets, collider physics, soft-collinear effective theory, etc. But so far it’s not providing any clear signals of physics beyond the Standard Model.
            If the answer is just for high-energy physicists to give up and permanently lower their ambitions, well, you know that isn’t going to work. Human beings want to work on interesting problems that point to truly new phenomena, and if your answer to them is to rein in their ambitions, then you clearly don’t understand why a lot of people become physicists, or even scientists more generally. And it’s easy for you to tell them to do that, seeing as you’re not the one who has a job doing physics all day.
            Again, this is one reason why criticism by people outside the field is often taken less seriously — it’s not your day’s work we’re talking about here.
            And your comment “I suspect that this would be a lot more productive in the short run” is also hard to take very seriously. How would surgeons or aeronautical engineers or mathematicians feel if someone who wasn’t familiar with the tools of their field told them that? How do you know what would make the field more productive? This is a serious question here — I don’t mean this as a rhetorical jab. What expertise allows you to predict that “lowering ambitions” would make the field more productive?
            And what does “lowering ambitions” mean concretely? String theory is out, presumably. What about supersymmetry? Dark matter? Neutrino masses? Early-universe cosmology? CMB observations? Who gets to draw that line?
            But like I said, paper and ink are cheap. If you have concrete proposals for addressing the actual problems of the field, like (1) or (2), please have at it! Write it up! (And this goes for everyone inside the field as well as outside.)

          • ns, this comment almost didn’t make it through moderation, as I find its tone to be borderline acceptable. However, in the end it comes down to what one means by “outside the field.” Jim has qualifications in physics; Peter is clearly within the field; and so certainly is Lee Smolin. A number of philosophers of physics also known enough about the actual physics to contribute to the discussion. Sure, a layperson with no training in physics has little interesting to say about this issue, but that’s not who’s contributing here.

            As for the question of what’s the alternative, I’m always puzzled by this “it’s the only game in town” type of argument. Start hiring people who work on different approaches, or make available grants that specifically call for novel theorizing about fundamental physics, and I’m sure you’ll get lots of applicants.

          • As an obviously simple minded observer, may I ask a simple question?
            Doesn’t the field vs. string conflict go back to the wave vs. particle duality, as to whether reality is fundamentally holographic, or atomized and that both sides have tunneled into this complex to enormous extremes, yet encounter feedback issues that pose ever more dimensions?
            If so, then isn’t there a basic philosophic issue here, as to the inherently duality of nature?

          • Massimo,

            I really don’t mean any offense here. When I wrote about people outside the field, I didn’t mean that in a pejorative or judgmental sense at all. What I’m trying to do is explain at a descriptive level why people in the high-energy community don’t take some criticisms from people on the outside very seriously. Maybe they’re right to do that, and maybe they’re wrong. But it’s important to understand what their reasoning is if your goal is to change minds and get them to listen. People are more willing to listen if they feel that their motivations are properly understood.

            Indeed, nothing gets a person listening better than showing them that you fully understand and appreciate what their arguments and motivations are.

            I can also be more specific about what I mean when I talk about people outside the field. I mean that if a person hasn’t computed a one-loop scattering amplitude, and hasn’t computed a path integral, and hasn’t computed an effective potential or a gauge anomaly or used a sum rule, and certainly if a person hasn’t tried to construct a new model that goes beyond Standard-Model physics that attempts to navigate the many constraints at issue here and run that idea by people to see if it really does get around those constraints, then one doesn’t truly understand what people are up against. (I’m sure Peter has done some of these things, for example, but I don’t know how much time he has personally spent on the last one. Perhaps he could correct me there!)

            Training in physical chemistry or philosophy of science, while wonderful and very much worth everyone’s general respect, isn’t enough to be an expert in this required sense. But although this knowledge barrier is a difficult problem (http://abstrusegoose.com/272), it’s an eminently fixable problem! Pick up some textbooks, learn the tools, do some of the hard calculations, go to seminars and workshops for a couple of years, and talk to lots of the “ordinary” people in the field about what they’re working on and why, not merely the flashy people with big names who give the news interviews. Throw your own constructive ideas and proposal at them and see how they respond. I guarantee you’ll get a different picture of what’s going on and why, and maybe some humility about how easy it really is to solve the problems that are ultimately at issue.

            Supersymmetry, string theory, etc., all sound pretty crazy in the abstract, especially when one’s knowledge comes from reading popular accounts. (10 or 11 dimensions? NS5-branes? Are they just saying anything that pops into their heads?) But when you look carefully at the constraints that you have to navigate and start piecing together what you need to get around them, you keep coming back to these sorts of ideas. It’s hard to explain unless you look carefully at those constraints.

            This doesn’t mean the ideas are correct, but it gives a reason why in the absence of experimental data, people are working on them (and using them to generate spin-off ideas that are independent of them) other than because the ideas are just part of a fad or because they’re the imposition of a regime of old tenured professors. It also gives a reason people haven’t succeeded by other approaches.

            Let me address your other comment, which is an important one. You write: “Start hiring people who work on different approaches, or make available grants that specifically call for novel theorizing about fundamental physics, and I’m sure you’ll get lots of applicants.”

            In the abstract, that sounds like a great idea. But none of the approaches to going beyond the Standard Model that currently exist and haven’t been dashed by constraints pass muster with critics, apparently. (Supersymmetry, string theory, etc.) So you’d have to look for someone working on something that’s not (a) one of these ideas that are not acceptable, nor (b) an idea that clearly doesn’t work or that has been definitely ruled out.

            So what’s left? As someone in the field, I don’t know the answer, but I’d love to know it.

            So if we can’t find someone working on a promising idea that either is (a) acceptable (not string theory, for example) or (b) that isn’t clearly inconsistent with known constraints, then our alternative is to go with (i.e., hire or give a grant to) someone who simply promises to do something new that doesn’t run into violations of constraints once they’re hired or get the grant. Say, we set aside a small amount of funding for a small population of people who are just told to go do something different, but nobody knows what that is, because all the ideas so far fall into categories (a) or (b).

            So how do we pick these people? Who’s a candidate? How does the hiring/grant process work? How is the candidate to be evaluated as a likely prospect for success, if we can’t use the person’s previous research, which apparently falls into (a) or (b)? Again, these are not rhetorical questions — this could be a very constructive dialogue, and people in the field could clearly benefit from some concrete suggestions beyond merely telling them to just do it somehow, because it’s not obvious.

          • No offense taken (at the least, not by me), but it does seem a strange position you are depicting. So we (meaning society at large) give millions, no, billions of dollars to the fundamental physics community, and the inner circle of such community cannot be bothered to engage competent outside critics in a public arena? But I’m a bit more optimistic, actually. Greene has engaged his critics, and as a matter of fact has retreated significantly from his boisterous attitude of a few years ago. Indeed, I get the impression that the entire string theory community is very much on the defensive these days, and that more and more young people are jumping ship looking for something else to do, something that yields actual (empirical) results. So the criticism, internal and external, is actually doing its job.

          • ns12345,
            I can’t speak for Jim, but my own goal has never been to quiet the bombasts of the HEP community. That’s hopeless and you’re right, not a solution to the problems of the field. To me what’s at issue are not people, but ideas that deserve to be challenged, whether they’re promulgated loudly by bombasts, or quietly by thoughtful people. For example, Witten is the opposite of a bombast, as well as much more talented and harder working than me, and much more deeply knowledgeable about most topics. I’ve learned a lot from his work and what he has to say, and it wouldn’t occur to me to tell him to shut up about string theory. At the same time, I don’t think he’s always right about everything and some of what he has to say deserves to be challenged.

            It seems to me very much worth challenging the constellation of speculative ideas (strings, susy, guts) that have dominated the field for many years. The public deserves a more honest account of what is going on than they’re getting, and people in the field seem to need to be reminded of what is solid and what is flimsy conjecture. The “why are you doing this, it would be better if you did something positive” argument is a serious one, but it’s just a fact that a counter-weight of solid argument is needed to push back against some of the highly dubious ideas getting a lot of attention and being pushed hard by some with an agenda. There’s a public marketplace of ideas here, and it deserves to have all sides representedtt.

            Then there’s the “multiverse”, which I think is just a major intellectual scandal and looming disaster threatening the subject and its credibility with the public. I don’t see how anyone can think that the problem there is complaints about this rather than the behavior being complaining about.

          • Hi Massimo,

            As for the question of what’s the alternative, I’m always puzzled by this “it’s the only game in town” type of argument. Start hiring people who work on different approaches, or make available grants that specifically call for novel theorizing about fundamental physics, and I’m sure you’ll get lots of applicants.

            Sure you will, if you offer people jobs and money they will take them. But whether you then get worthwhile results is a whole other issue. It’s easy to ask for areas or avenues of research that simply will not make progress. So the question is really, who is in the best position to judge which are the best routes to progress? I think you’re underestimating ns’s comments about the difficulties of starting with a blank sheet of paper and the likelihood of getting anywhere given the vast array of physics that the novel idea needs to be compatible with. Most string theorists do indeed spend a lot of time thinking about other alternatives also. If they could see promising avenues they would take them. And grant-awarding bodies would want to support them.

          • Peter– These are all very thoughtful comments, and I agree with a lot of it.

            I’m a little concerned with a few things. You write, for example: “The public deserves a more honest account of what is going on than they’re getting, and people in the field seem to need to be reminded of what is solid and what is flimsy conjecture.” Are you sure about this? I know there are some people in the field (often the loudest people) who seem to confuse what is solid and what is flimsy, but most of the people I encounter will gladly tell you the difference if you ask them. Nobody in the field thinks string theory or supersymmetry or brane worlds etc. are on the same footing as W and Z bosons, or, since 2012, the Higgs, for example. Just because a lot of effort is being spent on these speculative ideas doesn’t mean that most people working on them think they’re as solid as Standard Model physics. As I said, there are other reasons people work on this stuff, in part because people hope one day that they might become solid and experimentally verified or because they might spin off such ideas.

            Supersymmetry is a great case in point. It is true that there are many possible SUSY models. But if the LHC switches back on at higher energy and starts seeing superpartners, SUSY will go from speculation to experimental science. Would criticisms today of SUSY as unscientific then retroactively be incorrect? If SUSY changes from bad science that people shouldn’t be spending their time on to good, real science if it is detected experimentally, then was it really bad science to begin with? (The same goes for if we found missing energy that was consistent with extra-dimensional models, or if, heaven be kind, we see a giant stretched string fossilized on the CMB that got blown up during inflation. Why would people be studying such possible experimental signatures if they didn’t think experimental verification were important?)

            One reason for working on SUSY, string theory, holography/AdS/CFT, etc., that I didn’t mention, other than consistent theory-generation, is that some of these ideas have provided powerful tools for analyzing good old quantum field theory and general relativity, which many critics say would be a good way to spend one’s time. As everyone knows, QFT, in particular, is a very, very hard subject, and there are precious few calculations that can be done to learn what’s going on even at a qualitative level. If you think that more time needs to be spent trying to understand QFTs like the Standard Model, or general relativity, then a lot of people who use SUSY or string theory or conformal field theory or holography/AdS/CFT would fully agree with you, because that’s part of the work they’re doing. (Some examples are the work being done on strongly coupled gauge theories or condensed-matter systems using holography, or N=2 SYM to understand confinement better, or work on scattering amplitudes, or holographic methods to study rapidly spinning Kerr black holes in our plain old 3+1 dimensional universe.) People are attracted to these techniques because there are very few techniques that work, and, again, this is hard to get across sometimes to people who don’t use these sorts of techniques.

            Another thing about new ideas: If someone does come up with something new that is both consistent with all the many constraints and can connect better with experiment — and a lot of people even doing string theory are trying this all the time — then the community will absolutely take notice. When AdS/CFT was proposed, and seemed to provide a nonperturbative definition of quantum gravity in asymptotically AdS spacetimes in terms of a 3+1 dimensional quantum field theory, people noticed and a lot of people began working on these sorts of ideas pretty much full time.

            So, again, I don’t think the problem is fads or a regime of tenured faculty, because people would switch (and have switched) to new ideas if those ideas could be found and actually navigated all the constraints. And starting with a blank sheet of paper has never, ever worked. As Coel points out, “I think you’re underestimating ns’s comments about the difficulties of starting with a blank sheet of paper and the likelihood of getting anywhere given the vast array of physics that the novel idea needs to be compatible with. Most string theorists do indeed spend a lot of time thinking about other alternatives also. If they could see promising avenues they would take them. And grant-awarding bodies would want to support them.”

            The real trouble with (high-energy) physics is points (1) (lack of experimental data) and (2) (minefield of constraints) that I’ve made before. Solving these problems will take miracles from the LHC or from the CMB or some other experiment, or the good fortune of stumbling on a new idea in an already very mature field that is riddled with roadblocks. Telling people to drop everything and start from scratch with a blank piece of paper is a career ender, not because it would mean going against a fad or would upset old professors, but because in physics it’s a recipe for making no progress at all.

            The area on which I (and many others in the high-energy community) would partially agree with many critics and partially disagree with Coel is about the multiverse. There are still a lot of people both big and small in the field, both string theorists and not, who either think the multiverse is bad science (one can always solve any problem by proposing a multiverse, just like one can solve any problem by citing divine intervention, and the multiverse, unlike string theory, is so vague that it has never had to navigate the minefield of constraints), or who accept it as a possibility only very unwillingly because it’s a generic prediction of most models of inflation and because of Weinberg’s successful prediction of the value of the cosmological constant. There is not the sort of excitement around the multiverse that there was earlier on with string theory, for example. The otherwise-amazing new movie “Particle Fever,” which painted a marvelous picture of the experimental side of high-energy physics (many of whom wanted to see superpartners, by the way!), really offended a lot of people I know in high-energy theory because all the theorists in the film were saying repeatedly and quite definitively that it’s “either” SUSY (if the Higgs is light) or the multiverse (if the Higgs is heavy). That’s it! SUSY or multiverse! I was pleased that everyone I’ve spoken to in the high-energy theory community found that patently ridiculous, and it’s a shame that it gave the public that erroneous impression.

            Again, I agree that some people in the community are saying things that are unacceptable, but, again, that’s not the source of the basic troubles that face the field today.

          • Massimo,

            I apologize for missing your earlier post.

            You write: “No offense taken (at the least, not by me)…” I appreciate that, because I assure you that none was ever meant!

            Then: “…but it does seem a strange position you are depicting. So we (meaning society at large) give millions, no, billions of dollars to the fundamental physics community, and the inner circle of such community cannot be bothered to engage competent outside critics in a public arena?”

            I think it’s important to be careful not to conflate the two sides of high energy here. The experimental side is the one getting “billions of dollars,” and there is wide agreement that they are doing real science. The LHC has won well-deserved plaudits from all sides. What they have built is truly a testament to the powers of the human spirit and ingenuity.

            The main focus of critics is on the theorists, but theory funding is a totally different ball game. I don’t know as well how things work in other fields like, say, biology or chemistry, but in theoretical physics, most grad students, for example, do not have consistent funding at all, and the population of theorists is much smaller than the population of experimentalists. And a lot of the funding that does exist comes from foundations and private sources. This isn’t to say that less money from taxpayers means that criticism from the outside is less legitimate, but one cannot point to billions of taxpayer dollars as something that high-energy theorists somehow need to answer for.

            But, hey, give them billions of dollars, and I can assure you people in the high-energy theory community would be happy to engage in more criticism!

            You also write: “Indeed, I get the impression that the entire string theory community is very much on the defensive these days, and that more and more young people are jumping ship looking for something else to do, something that yields actual (empirical) results. So the criticism, internal and external, is actually doing its job.” There are a lot of assumptions here.

            First, it is true that string theory is less exciting nowadays, but if you talk to lots of people deep on the inside, many of whom don’t pay much attention to non-specialist critics, it’s precisely because of the lack of contact with experiment and the long period of time that has gone by without major progress. That’s how things are supposed to work in science! There is no hard evidence that it’s because *external* criticism “is actually doing its job.” But we can be scientific about this — I’d be happy to see some sort of good data that I’m incorrect.

            Second, as to your suggestion that “more and more young people are jumping ship looking for something else to do,” that’s both true and false. It’s false in the sense that the supply of young people trying to get into string theory, supersymmetry, etc. is just as high as ever, at least if PhD admissions data are to be believed. But it’s true in the sense that there are fewer job openings for them, and lots more are leaving for finance. (There are some who might wonder if society would be better served if they stayed in string theory.)

            What doesn’t appear to be the case is that any significant number of them are leaving these areas of high-energy theory and heading into other areas of physics, which is presumably what many external critics are hoping for.

          • ns, quickly: it was actually Brian Greene who admitted during his debate with Jim that string theory is loosing bright students and young practitioners, but of course I don’t know the numbers.

          • What an interesting discussion! I’ve missed the opportunity to participate ‘live’ because I’ve been working with a client in London all day, but then perhaps there are some advantages in postponing a contribution…
            ns12345 – you’re clearly very passionate about this and I totally respect your position.
            So, let’s try to bring this discussion to a close.
            The simple truth is, I’m a symptom, I’m not the cause. You can attempt to undermine my arguments by claiming that I don’t what I’m talking about (and – honestly – I don’t mind). I confess I don’t have the time or the inclination to compute a one-loop scattering amplitude, but this is not really the point, I think. It’s naïve to suggest that only those who have experienced the trials and tribulations of theoretical physics’ front line can be sufficiently qualified to judge its merits.
            Here’s what you should be really worried about. That a science writer supposedly unqualified to hold an opinion about these things can be invited by high-profile private foundations to participate in a discussion on this subject. Read the runes, here. These are foundations that are involved in supporting a lot of contemporary theoretical physics. It’s only right that they should seek to clarify the scientific basis of the work they’re funding, and promoting healthy debates in this area is right and proper.
            You say that lowering ambitions isn’t going to work. Maybe. But if the string theory community can’t come together and find a research programme that enables somebody to predict *something*, then I can tell you that patience will eventually run out (I just can’t tell you when). I sincerely don’t think this needs to be a prediction related to ‘new physics’, involving energy regimes that are in any case likely to be forever out of reach of terrestrial colliders. And I’d avoid predicting subtle manifestations of string physics in the CMB as these may be really hard to prove, given the inevitable assumptions and approximations required to implement current (accepted) theories.
            If you’re convinced that nature is essentially ‘stringy’, then a prediction of an already known physical property, of a kind that yields genuine insights into the nature of this stringy reality, will be more than enough. We might gain no new empirical knowledge, but such a prediction would nonetheless be regarded as progressive if it promises the prospect of a deeper understanding of reality that *could* lead eventually to new physics.
            Remember that when Feynman first published his ‘sum-over-histories’ approach to quantum mechanics, this was dismissed as just another mathematical structure that offered nothing that couldn’t already be predicted by existing structures. But the simple truth was that Feynman’s approach offered a whole new way of understanding quantum processes that yielded genuine, progressive, advances.
            Of course, if the answer is as Peter has outlined in his responses to MathPhysPhd, above, and it remains all to difficult to provide predictions without putting in more information than you get out, then I fear the problem is real and we rest our case.

          • Jim– I appreciate your note and your engagement on this.

            You write: “The simple truth is, I’m a symptom, I’m not the cause.” I assume by this that you mean that your writing and public involvement on these issues is not the cause of the underlying troubles with high-energy theory these days, but is simply a reflection of problems that are present. On this, and with full respect, I agree.

            I think our disagreement is more about identifying the source of those problems. There’s a tremendous amount of public blaming being placed on the physicists themselves here, in part because a small number of prominent individuals have been saying irresponsible things in public. High-energy theorists are being condemned in some quarters not just for ruining physics, but for debasing science as a whole.

            What I have argued here is that while there are serious challenges confronting the field, the problems aren’t primarily due to bad behavior or hyping by certain personalities, but due to deeper and less flashy problems with experimental progress and with the calcification of the subject by its sheer maturity, manifested in the dense snarl of constraints that (correctly) doom the vast majority of attempts to find genuinely new directions. (Some of these problems are growing issues for the scientific enterprise as a whole, and I believe they are deeply connected with the gradual disappearance of low-hanging fruit.)

            And I think it’s absolutely crucial to make clear what the primary source of the trouble is, because if the source is identified incorrectly, then people will go after the wrong solutions that will only alienate members of the community who are dealing with these problems head on.

            This is the reason I keep pointing to the issue of expertise. It’s not simply to discredit critics. It’s because the lack of expertise and inside knowledge by many critics is the reason why so much of the criticism these days misses the mark and alienates rather than helps. It’s because when I read so much of the criticism, what I and many others see is a failure to understand the field well enough to pinpoint and help deal with the real problems facing it.

            I said critics had to know what a 1-loop amplitude calculation looks like — or, better, how ideas like supersymmetry and string theory are technically motivated, or what is actually involved in trying to create a new direction that navigates all the constraints — not simply because they need credibility or are otherwise unqualified, but because without that knowledge, they’re unlikely to be able to see up close what the real problems are and give helpful advice. And given a lot of the criticism I hear, that’s a well-founded judgment. Criticism would be better and more helpful if it were coming from people who better understood the challenges of the field today — and, indeed, there is a lot of internal criticism of just this sort by practitioners. But criticism is not the same thing as constructive suggestions, which are in short supply precisely because the challenges facing the field are very, very hard to overcome.

            I hope I’m correct in thinking that everyone involved here wants what’s best for science. So why should so many high-energy theorists despise what all these “well-meaning” critics are doing? If the advice is intended to be helpful, why would the practitioners ignore it and even get angry about it?

            Because it’s not enough to be well-meaning. Criticism and advice has to be well-informed and reflective of the actual problems on the ground and furthermore be constructive, and instead a lot of the criticism amounts to public character attacks on the people doing the actual work and on the value of the work itself, or calls for practitioners to halt their work and “do something better,” whatever that is. For me, the difference between reading a lot of this criticism before joining the community and seeing what things were actually like inside was like night and day.

            You write: “You say that lowering ambitions isn’t going to work. Maybe. But if the string theory community can’t come together and find a research programme that enables somebody to predict *something*, then I can tell you that patience will eventually run out (I just can’t tell you when).”

            I should begin by saying that there is no unified string community. People have always worked on lots of different things (including non-stringy physics — I can tell you from personal knowledge that “even” string theorists are hard at work trying to improve our understanding of “mainstream” questions in quantum field theory), precisely because there is no overarching cabal. One hope is that working on many directions simultaneously will be more likely to make progress, but the truth is that people just have different interests, and interests are what make people into scientists in the first place.

            As for the “patience” question, whose patience are we talking about here? The people funding the research? That’s certainly a problem, but, again, it doesn’t suggest an obvious solution. It’s all well and good to point out that funding will dry up unless the impasse facing high-energy theory is overcome — this is an ongoing concern among people in the field — but how precisely does one bell the cat? That’s the whole question here. It’s a very hard problem.

            You suggest that a more reasonable ambition would be just to try to use string theory to explain something new about physics in regimes we already know about. Well, string theory (and ideas like supersymmetry) have taught us a great deal about quantum field theories that would have been difficult to guess otherwise. And although AdS/QCD isn’t string theory in its original quantum-gravity sense, it has provided calculational tools for studying and making predictions about various properties like viscosities. There have also been advanced in computing scattering amplitudes in collider calculations.

            Is that close enough to Feynman’s sum-over-paths formulation being helpful for better understanding quantum theory? The trouble is that quantum gravity is associated with the Planck scale, which is so far removed from everyday experience that the first quantum corrections to gravity in the solar system are 10^-70 effects. (A fun exercise: Compute the “Bohr level” of the Earth moving in the Sun’s 1/r Coulomb-like potential. The number is mind-blowing.) So unless there’s a miracle, like amplified quantum-gravity effects in the CMB, seeing a signature is going to be very, very hard, regardless of which model of quantum gravity one is using. Again, this is Nature’s fault, not the fault of physicists.

            You conclude by writing “I fear the problem is real and we rest our case.” I agree with the first part of this sentence but not the second part. I’ve never argued that there weren’t real problems. What I’ve argued is that the case often being made by many critics is the wrong one, and hasn’t been very helpful to anyone. It is in everyone’s best interest that the case be improved.

            In particular, it would be helpful if this whole discussion changed from its current confrontational posture (“Not even wrong!!!”) in favor of a more cooperative one.

          • ns12345,
            ” It’s because the lack of expertise and inside knowledge by many critics is the reason why so much of the criticism these days misses the mark and alienates rather than helps. It’s because when I read so much of the criticism, what I and many others see is a failure to understand the field well enough to pinpoint and help deal with the real problems facing it.”

            What is your actual, specific, scientific proof that no one outside the field can possibly offer any useful criticism?
            For those of us who are not completely brainless and do have to function in that pedestrian everyday world, there are two ways to address a problem; One is to step forward and examine it in detail and identify where the gaps are and how best to fill them. The other is to step back and try to put the issue in some larger context to see if some big picture factor is being overlooked.
            Physicists are the epitome of the first method, but not to put it too bluntly, really suck at the second method, as this is mere philosophy to the shut up and calculate crowd and will invariably step on some sacred/no go territory.
            Why is that? For those of us who don’t have the time to examine every infinitely small detail and can’t spend our lives focused on a particular detail of the very small, very large, or very abstract, there is a lot of fuzzy math inherent in understanding the big picture. The connections matter more than the details. There really is no clear line where the chicken ends and the fox begins. It is all entangled. From the top down, it’s all about the network and the nodes are dispensable, as you are likely all too aware, from your own personal life and as we all know, those in management suck at understanding all the details.
            Now most any twelve year old science geek probably finds the idea of multiple universes and all those extra dimensions really cool, as they play video games based on some alternate reality. Yet your average forty five year old CPA understands all too well what can be done with the math, when, like any good magician, you get everyone hyper-focused on favored details and completely ignore the others. They can readily understand what people like Greene and Tegmark are selling, but in the grand scheme of things, where large numbers of peoples lives are being shredded, it really is small potatoes.
            So while you might be really, really clever, you are still looking at only one side of a fundamentally dualistic reality. For example, further up this thread, I raised the point that time is better understood as the process by which future becomes past, rather than a measure from prior events to succeeding ones. To give a basic analogy of this duality, consider a product and production line; The product goes from initiation to completion, while the process, the production line, points the other direction, as it consumes raw material and expels finished product. So the product, going start to finish, goes from beginning to end, while the process points to the future as it creates and expels these units, which fall away into the past.
            Now cosmology has modeled the entire universe as only one side of this relationship, that of the universe as a single entity, forming and fading, because it models time as nothing more than that narrative arc, from beginning to end.
            Now you are likely to ignore this, as it doesn’t fall within your particular model, but I can safely say that at the end of your model, “The physics breaks down.” And you are never going to quite understand why.
            Regards,
            JBM

          • brodix,

            The other is to step back and try to put the issue in some larger context to see if some big picture factor is being overlooked. Physicists are the epitome of the first method, but not to put it too bluntly, really suck at the second method, [...] I can safely say that at the end of your model, “The physics breaks down.” And you are never going to quite understand why.

            Sorry, but physicists see this sort of thing as well as or better than anyone. It is complete conceit that physicists are limited in this way and that others are much better at it.

          • Coel,
            It’s not that others are better at it. We all have our biases and points of view. It is just that groups of people can create negative feedback loops as easily as they create positive feedback loops and so re-enforce assumptions.
            If you really want to refute my argument, why not directly dispute my point about time, that physics has simply reduced the narrative function to particular measures of duration, because of the past to future sequencing of individual perspective is fundamental to the thought process, rather than actually considering how the dynamic of changing configuration creates this effect and that measures of time are basically distinct frequencies. Making time an effect of action, like temperature, not some dimensional basis for it.
            Yes, spacetime is clever geometry, but we could use ideal gas laws to relate volume to temperature, but we don’t, because we understand temperature is an emergent effect of a multitude of amplitudes.

      • Higgs’s theory too was confirmed “in theory”, meaning you can call it confirmed if you like, but then you don’t have to. Theories are normally confirmed neither “in theory” nor using synthetic data alone. The Higgs fable is far more ridiculous than strings and multiverse theories could ever be. Why? As we all remember it vividly (or you think we all suffered amnesia?), at first the official story went in the direction of “Higgs boson that gave mass to everything”. But then, when the community (and finally the general public, which means you’re really busted!) started asking The Question: “- What then gave mass to Higgs boson?”, the High Committee of Wizards of Oz took a few months break and came back with the Directive that it’s actually “Higgs’s field that gave mass to everything”. Oh boy, what a U-turn: a particle that’s one of the rarest things in the known universe could actually form a field?! And then, this field could actually give mass to anything, let alone everything?? Please, give us more fables of the SM format; how about some involving “soups” and other tools from Kitchen where a stove isn’t a a stove and a temperature isn’t a temperature, and there’s about ten million parameters to tune at will so that in the end everyone gets lost in the Wonderland of Confusion. So believe whatever you want, but stop confusing people into disbelieving everything. If you’re so unsure of something, grab a book or borrow a thought from those who knew far more than you do. How about this for starters: “A mathematical equation stands forever” – A.Einstein. And to it related: http://www.mynewsdesk.com/ba/pressreleases/as-big-bang-gets-downgraded-to-a-bang-the-first-scientific-proof-of-the-multiverse-claimed-975493

      • I must salute to both you (Woit) and Haggott about your courage to fight against the huge established institutions. But, I do disagree with your comment, “Woit: … and no good ideas about how to go beyond the SM, as well as a lot of experience with ideas that don’t work and the general principles why.”

        This is in fact the sayings of the other side, “…that this [M-theory and multiverse hypothesis] is the ‘only game in town’, combined with a seemingly inexhaustible optimism that ‘well, it still might be true’.”

        At ‘this’ Webzine, we did discuss a few points on these ‘going beyond the SM and the refuting the multiverse” issues.
        One, ‘string-unification’, see http://scientiasalon.wordpress.com/2014/05/22/my-philosophy-so-far-part-ii/comment-page-1/#comment-2432

        Two, the multiverse-hypothesis can be refuted with three points
        1. Showing that ‘this’ universe is not bubble dependent: everything (nature constants and laws) in this universe arose in this universe.
        2. Showing that ‘multiverse hypothesis’ cannot give rise to anything (nature constants and laws) of ‘this’ universe.
        3. Showing that the region where is beyond the event horizon of this universe is still a part of this universe.
        See, http://scientiasalon.wordpress.com/2014/06/05/the-multiverse-as-a-scientific-concept-part-ii/comment-page-1/#comment-3158

    • That’s a very sensible and insightful comment. One thing to add is that the data-starvation is almost inevitable as physics “completes” its account of the everyday world and progresses to the extremes. In Faraday’s time one guy could do this stuff in his garden shed, but now it takes many leading nations to band together to build the LHC. So you’re right that perhaps the real problem here is not string theory but that limit on experimental access to high energies. No science has ever got far without lots of guidance from nature.

    • I’m never sure how to take this sort of argument about a lack of data to challenge the SM. There are huge gaps between the standard beliefs about what the SM predicts about protons and what is experimentally observed. Either the purported derivations of what should be observed are wrong, in which case fixing them would seem like Job 0 for theorists, or the theory itself has a flaw, which would seem (to a layman) like a big hint from nature about Job 1. Maybe protons seem too “composite” and so not fundamental enough to be interesting, but the relegation of these issues to the sidelines of discussions seems peculiar from the outside.

  35. “I believe that contemporary theoretical physics has lost its way” Can some care be put into making statements like this? What is being criticised in this article is a relatively small subset of all of theoretical physics yet the criticism sounds like it is being applied more widely than that without justification.

    Putting in Frank “Omega Point” Tipler’s book into the same camp as string theory also seems to be unfair, particularly considering that the Final anthropic principle is presumably what is being referred to (I can’t access the original quote for context), which Tipler uses to justify a strange variant of Christianity. To paraphrase Asimov: “But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.””

    • Cathal,
      You’re right. This is a relatively small group of theorists but it’s one that has a disproportionate impact on the wider perception of science because they tend to deal with the ‘big questions’. It’s certainly not my intention to criticise all theoretical physicists and I’d hope the context is clear from the main body of my article (and my book).
      I’d included Helge Krage’s comments because I felt they were particularly relevant. I wouldn’t otherwise have mentioned Barrow and Tipler’s book, which is actually a very comprehensive (but quite uncritical) review of all forms of anthropic argument, including varieties of weak and strong principles.

  36. Coel,

    A while back you said “In science, evidence validates *theories* about how things work (rather than entities). If a theory predicts A, B, C and D, and if we validate the theory by empirically verifying A, B and C then we have good evidence (indirect evidence but still good evidence) for accepting D. It doesn’t matter whether D can be falsified so long as A, B and C can be.”
    But that’s theory T1. if another theory T2 predicts A, B, C but *not* D, that “proof” does not work.

    So let T1 = string theory/M theory, T2 = a GUT theory plus loop quantum gravity. Both predict all of standard physics plus the standard hot big bang, inflation, etc. Then T1 with a further ad hoc addition (a mechanism to realise different vacua in different inflationary bubbles) sometimes (i.e. in those inflationary models that are chaotic) predicts a multiverse that will have different constants in different bubbles, and so (if there is indeed a string theory vacuum that gives the standard model of particle physics: yet another unproven hypothesis).T1 can potentially solve the anthropic issue But T2 won’t do so: physics is the same in all bubbles in that case.

    The deduction fails unless you can prove in a testable way that T1 holds rather than T2.

    • Hi gfrellis,

      But that’s theory T1. if another theory T2 predicts A, B, C but *not* D, that “proof” does not work.

      You are right. I included that point in my original discussion of this in my previous article, but not in the summary on this thread (though perhaps I should have done).

      T1 can potentially solve the anthropic issue But T2 won’t do so: physics is the same in all bubbles in that case.

      Personally I don’t think that there is an “anthropic issue” that actually needs solving. It may indeed be the case that all multiverse bubbles have exactly the same physics — I don’t see anything wrong with that suggestion at all (though asking the question of whether they do is also worthwhile).

  37. Interesting story;
    http://phys.org/news/2014-06-universe-dwarf-galaxies-dont-standard.html
    “Pawlowski and 13 co-authors from six different countries examined three recent papers by different international teams that concluded the planar distributions of galaxies fit the standard model.
    “When we compared simulations using their data to what is observed by astronomers, we found a very substantial mismatch,” Pawlowski said.
    With computers, the researchers simulated mock observations of thousands of Milky Ways using the same data as the three previous papers. They found just one of a few thousand simulations matched what astronomers actually observe around the Milky Way.
    “But we also have Andromeda,” Pawlowski said. “The chance to have two galaxies with such huge disks of satellite galaxies is less than one in 100,000.”
    When the researchers corrected for flaws they say they found in the three studies, they could not reproduce the findings made in the respective papers.”

    At some point, they are going to have to go back and review a lot of what is currently considered settled.

    • At some point, they are going to have to go back and review a lot of what is currently considered settled.

      Researchers do that routinely. The paper you point to discusses structure formation and the how galaxies form in a Lambda-CMD cosmological model, and a lot of work is indeed being done on those topics, but this sort of cosmology is also supported by a lot of hard evidence (and is vastly different from string theory in that regard). Thus there is no real reason why anyone is “going to have to go back and review a lot of what is currently considered settled” other than the usual discussion of this that is normal and continual in science at the cutting edge.

      • Coel,
        Thank you for taking the time to reply. I suppose I’m not getting any interest in my original observation about time, or in asking how there remains a constant speed of light against which to measure the very expansion of space, so raising current headlines about divergences between theories and observation, especially when the conversation has been largely about problem in HEP, rather than cosmology, seems a futile effort.
        I would say though, that “hard evidence” and its interpretation are two different things. As you say to gfrellis, inflation is an observation driven theory. To which I would point out, so was epicycles, since we very clearly observe the sun moving overhead. As such, it is a patch between what we think and what we observe.
        Regards,
        John

  38. There are also two significant issues as regards the inflationary theory that is supposed to underlie the multiverse, in addition to the probability issues highlighted by Penrose and Steinhardt, which are related to the fact that there is no satisfactory measure that determines probabilities for the theory.

    First, no one knows what the inflaton field is – in virtually all the hundred or so versions of inflationary theory, an arbitrary potential function is written down with no solid link to established physics. The one and only exception is if the inflaton is a non-minimally coupled Higgs particle – which might possibly be the case. If so, the version of inflation that occurs is not chaotic.

    Second, the success of the theory depends on the supposed initial quantum fluctuations of the theory somehow becoming classical. There is no adequate theory of how this happens – a huge lacuna in the theory. Some claim that decoherence will solve this, but it does not – one needs a theory of how individual classical events occur, not just an ensemble.

    These issues do not show that inflation is wrong – but they do demonstrate that it’s theoretical foundations are rickety. It’s not a cut and dried theory. And occurrence of inflation is not dependent on string theory/M theory – the great success of jnflation in explaining cosmological observations does not validate that version of quantum gravity. They are often sold as unified package – but that is not necessarily the case.

    • Hi gfrellis,

      You are right that we should be careful to keep inflation (and a possible eternal-inflation multiverse) distinct from string theory. Cosmological inflation is largely an observationally driven idea, with little or no understanding of the underlying physics. String theory is the opposite, an attempt at the underlying physics with little or no link to observation.

  39. I know its a little late to put this in, but I think the following question is the key:

    * What potential experimental or observational evidence is there that would persuade you that the theory you are proposing is wrong?

    If there is none, then in my view it is not a scientific theory, it’s philosophy – and of course there is nothing wrong with philosophy! – it just should not be confused with science..

    If there is such evidence, please clarify what it is, and we’ll be on our way to look for it. You’ll have made clear what makes the multiverse science – provided you will indeed give up the theory if the evidence comes out negative! That will be the test of devotion to real science, as opposed to hanging on to a dogma.

    By the way this has been an excellent discussion, thanks for hosting it, Massimo.

Follow

Get every new post delivered to your Inbox.

Join 1,344 other followers

%d bloggers like this: