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.

196 thoughts on “The evidence crisis

  1. 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.


  2. 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.


  3. > 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.


  4. “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.


  5. 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.


  6. 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.


  7. 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.


  8. 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.


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


  10. 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 …


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

    Click to access 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.



  12. 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.


  13. 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.


  14. 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.


  15. 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.


  16. 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.


  17. 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.”


  18. “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.


  19. 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.


  20. 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.


  21. 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.

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


  22. 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.


  23. 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.


  24. 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 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 ). 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’.


  25. [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.


    “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:

    “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.


    “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.


  26. 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.


  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.


  28. 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.


  29. 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;


  30. 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.


  31. 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.


  32. 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.


  33. 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…


  34. 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.


  35. 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.


  36. 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.


  37. 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.


  38. 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.


  39. 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.


  40. 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,


  41. 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…


  42. 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.


  43. 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.


  44. 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…


  45. 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.


  46. 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.


  47. 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.)


  48. 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.


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