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The Trouble with Physics
The rise of string theory, the fall of a science and what comes next.
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Published February 28, 2008
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About the author
Lee Smolin
13 books437 followersLee Smolin is a theoretical physicist who has made influential contributions to the search for a unification of physics. He is a founding faculty member of the Perimeter Institute for Theoretical Physics. His previous books include The Trouble with Physics, The Life of the Cosmos and Three Roads to Quantum Gravity.
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June 24, 2024
ARE STRING THEORISTS ENGAGED IN “GROUPTHINK”?
Lee Smolin (born 1955) is an American theoretical physicist, a faculty member at the Perimeter Institute for Theoretical Physics, an adjunct professor of physics at the University of Waterloo and a member of the graduate faculty of the philosophy department at the University of Toronto.
He wrote in the Introduction to this 2006 book, “This is a story of a quest to understand nature at its deepest level. Its protagonists are the scientists who are laboring to extend our knowledge of the basic laws of physics. The period of time I will address---roughly since 1975… may also be the strangest and most frustrating period in the history of physics since Kepler and Galileo began the practice of our craft four hundred years ago. The story I will tell would be read by some as a tragedy. To put it bluntly… we have failed. We inherited a science, physics, that… was often taken as the model for how other kinds of science should be done… But today, despite our best efforts, what we know for certain about these laws is no more than what we knew back in the 1970s. How unusual is it for three decades to pass without major progress in fundamental physics?” (Pg. viii)
He continues, “When I meet old friends from college and graduate school, we sometimes ask each other, ‘What have we discovered that our generation can be proud of?’ If we mean new fundamental discoveries … the answer, we have to admit, is ‘Nothing!’” (Pg. xi) He goes on, “To be fair, we’ve made two experimental discoveries in the past few decades: that neutrinos have mass and that the universe is dominated by a mysterious dark energy that seems to be accelerating its expansion… But when it comes to extending our knowledge of the laws of nature, we have made no real headway… Why is physics in trouble? And what can we do about it? These are the central questions of my book.” (Pg. xii) He concludes, “I am writing this book not to attack string theory or those who believe in it but … as an expression of faith in the physics scientific community.” (Pg. xviii)
He observes, “string theory… purports to correctly describe … both gravity and the elementary particles… and to do so, it … posits that the world contains as yet unseen dimensions and many more particles than are presently known. At the same time, it proposes that all the elementary particles arise from the vibrations of a single entity---a string--- that obeys simple and beautiful laws. It claims to be the one theory that unifies ALL the particles and ALL the forces in nature… Much effort has been put into string theory in the last twenty years, but we still do not know whether it is true… Those string theories we know how to study are known to be wrong. Those we cannot study are thought to exist in such vast numbers that no conceivable experiment could ever disagree with all of them… String theory rests on several key conjectures, for which there is some evidence but no proof. Even worse, after all the scientific labor expended in its study, we still do not know whether there is a complete and coherent theory that can even go by the name ‘string theory.’” (Pg. xiii-xiv) He adds, “Despite the absence of experimental support and precise formulation, the theory is believed by some of its adherents with a certainty that seems emotional rather than rational.” (Pg. xx)
He acknowledges, “I should admit that I am a realist. I side with Einstein and the others who believe that quantum mechanics is an incomplete description of reality. Where, then, should we look for what is missing in quantum mechanics? It has always seemed to me that the solution will require more than a deeper understanding of quantum physics itself… the problem of quantum mechanics … will probably emerge as we make progress on the greater effort to unify physics.” (Pg. 9-10) Later, he admits about supergravity, “It seemed to me that if you understood a theory, it shouldn’t take weeks of calculations on an art pad to check its basic properties… To this day, I don’t think anyone really understands what supersymmetry means, what it says fundamentally about nature---it its true.” (Pg. 96)
He suggests of the original string theory, “it was found that string theory … would be consistent with special relativity and quantum theory only if several conditions were satisfied. First, the world had to have twenty-five dimensions of space. Second, there had to be a tachyon—a particle that goes faster than light. Third, there had to be particles that could not be brought to rest… The world does not appear to have twenty-five dimensions of space. Why it is that the theory was not just abandoned then and there is one of the great mysteries of science.” (Pg. 104-105) Later, he adds, “There was no option for a theory that works in a three-dimensional space… you had to take the option with six extra dimensions… there had to be a way to hide the extra dimensions. There appeared to be no choice but to curl them up so that they were too small to be perceived.” (Pg. 119)
He argues, “Despite the reasons for discouragement, many string theorists could not let go of the idea that string theory constituted the future of physics… For many of them, string theory was simply the only game in town… The unfortunate result was that the split between believers and skeptics deepened. Each side became more entrenched, and each seemed to have good justification for its position.” (Pg. 128)
He observes, “If M-theory is right, our world has seven wrapped dimensions… we still don’t know whether it leads to a completely consistent quantum theory if the matrix becomes infinite. Unfortunately, M-theory remains a tantalizing conjecture. It’s tempting to believe it. At the same time, in the absence of a real formulation, it is not really a theory---it is a conjecture about a theory we would love to believe in.” (Pg. 147)
He explains, “The idea that string theory gave us not one theory but a landscape consisting of many possible theories had been proposed in the late 1980s… the vast landscape of theories finally came to be seen not as a freak result to be ignored but as a means of saving string theory from being falsified. Another reason the landscape idea took hold was, quite simply, that theorists were discouraged. They had spent a long time searching for a principle that would select a unique string theory, but no such principle had been discovered. Following the second revolution, string theory was now much better understood… The question … [was now] how to do physics with such a huge collection of theories. One response is to say that it’s impossible… If an attempt to construct a unique theory of nature leads instead to 10(to the 50th power), that approach has been reduced to absurdity. This is painful for many who have invented years and even decades of their working lives working in string theory… Still, even if it hurts like h_ll, acknowledging the reduction ad absurdum seems a rational and honest response to the situation… But it is not one that most string theorists choose.” (Pg. 158-159)
He summarizes, “On the basis of current results, we cannot confidently assert that string theory solves the problem of quantum gravity. The evidence is mixed… What we CAN say is that within these limitations there is some evidence that string theory points to the existence of a consistent unification of gravity and quantum theory. But is string theory itself that consistent unification? … it seems unlikely.” (Pg. 191) He adds, “string theory is certainly among the directions that deserve more investigation. But should it continue to be regarded as the dominant paradigm of theoretical physics? … I think the answer… must be no. String theory has not been successful enough on any level to justify putting nearly all our eggs in its basket… Some string theorists have advocated supporting string theory because it is ‘the only game in town.’ … In face there ARE other approaches…” (Pg. 199)
He argues, “There is good evidence that the progress of string theory itself has been slowed by a sociology that restricts the set of questions investigated and excludes the kind of imaginative and independent-minded scientists that progress requires.” (Pg. 268) He continues, “sociologists have no problem recognizing this phenomenon… which is called GROUPTHINK.” (Pg. 286)
He concludes, “We are indeed in a revolutionary period, but we are trying to get out of it by using the inadequate tools and organization of normal science… We are horribly stuck, and we need real seers… it has been a long time since seers were needed.” (Pg. 311) Later, he adds, “the real question is not why we have expended so much energy on string theory but why we haven’t expended nearly enough on alternative approaches.” (Pg. 349)
This book will be of great interest to those seeking critiques of string theory.
Lee Smolin (born 1955) is an American theoretical physicist, a faculty member at the Perimeter Institute for Theoretical Physics, an adjunct professor of physics at the University of Waterloo and a member of the graduate faculty of the philosophy department at the University of Toronto.
He wrote in the Introduction to this 2006 book, “This is a story of a quest to understand nature at its deepest level. Its protagonists are the scientists who are laboring to extend our knowledge of the basic laws of physics. The period of time I will address---roughly since 1975… may also be the strangest and most frustrating period in the history of physics since Kepler and Galileo began the practice of our craft four hundred years ago. The story I will tell would be read by some as a tragedy. To put it bluntly… we have failed. We inherited a science, physics, that… was often taken as the model for how other kinds of science should be done… But today, despite our best efforts, what we know for certain about these laws is no more than what we knew back in the 1970s. How unusual is it for three decades to pass without major progress in fundamental physics?” (Pg. viii)
He continues, “When I meet old friends from college and graduate school, we sometimes ask each other, ‘What have we discovered that our generation can be proud of?’ If we mean new fundamental discoveries … the answer, we have to admit, is ‘Nothing!’” (Pg. xi) He goes on, “To be fair, we’ve made two experimental discoveries in the past few decades: that neutrinos have mass and that the universe is dominated by a mysterious dark energy that seems to be accelerating its expansion… But when it comes to extending our knowledge of the laws of nature, we have made no real headway… Why is physics in trouble? And what can we do about it? These are the central questions of my book.” (Pg. xii) He concludes, “I am writing this book not to attack string theory or those who believe in it but … as an expression of faith in the physics scientific community.” (Pg. xviii)
He observes, “string theory… purports to correctly describe … both gravity and the elementary particles… and to do so, it … posits that the world contains as yet unseen dimensions and many more particles than are presently known. At the same time, it proposes that all the elementary particles arise from the vibrations of a single entity---a string--- that obeys simple and beautiful laws. It claims to be the one theory that unifies ALL the particles and ALL the forces in nature… Much effort has been put into string theory in the last twenty years, but we still do not know whether it is true… Those string theories we know how to study are known to be wrong. Those we cannot study are thought to exist in such vast numbers that no conceivable experiment could ever disagree with all of them… String theory rests on several key conjectures, for which there is some evidence but no proof. Even worse, after all the scientific labor expended in its study, we still do not know whether there is a complete and coherent theory that can even go by the name ‘string theory.’” (Pg. xiii-xiv) He adds, “Despite the absence of experimental support and precise formulation, the theory is believed by some of its adherents with a certainty that seems emotional rather than rational.” (Pg. xx)
He acknowledges, “I should admit that I am a realist. I side with Einstein and the others who believe that quantum mechanics is an incomplete description of reality. Where, then, should we look for what is missing in quantum mechanics? It has always seemed to me that the solution will require more than a deeper understanding of quantum physics itself… the problem of quantum mechanics … will probably emerge as we make progress on the greater effort to unify physics.” (Pg. 9-10) Later, he admits about supergravity, “It seemed to me that if you understood a theory, it shouldn’t take weeks of calculations on an art pad to check its basic properties… To this day, I don’t think anyone really understands what supersymmetry means, what it says fundamentally about nature---it its true.” (Pg. 96)
He suggests of the original string theory, “it was found that string theory … would be consistent with special relativity and quantum theory only if several conditions were satisfied. First, the world had to have twenty-five dimensions of space. Second, there had to be a tachyon—a particle that goes faster than light. Third, there had to be particles that could not be brought to rest… The world does not appear to have twenty-five dimensions of space. Why it is that the theory was not just abandoned then and there is one of the great mysteries of science.” (Pg. 104-105) Later, he adds, “There was no option for a theory that works in a three-dimensional space… you had to take the option with six extra dimensions… there had to be a way to hide the extra dimensions. There appeared to be no choice but to curl them up so that they were too small to be perceived.” (Pg. 119)
He argues, “Despite the reasons for discouragement, many string theorists could not let go of the idea that string theory constituted the future of physics… For many of them, string theory was simply the only game in town… The unfortunate result was that the split between believers and skeptics deepened. Each side became more entrenched, and each seemed to have good justification for its position.” (Pg. 128)
He observes, “If M-theory is right, our world has seven wrapped dimensions… we still don’t know whether it leads to a completely consistent quantum theory if the matrix becomes infinite. Unfortunately, M-theory remains a tantalizing conjecture. It’s tempting to believe it. At the same time, in the absence of a real formulation, it is not really a theory---it is a conjecture about a theory we would love to believe in.” (Pg. 147)
He explains, “The idea that string theory gave us not one theory but a landscape consisting of many possible theories had been proposed in the late 1980s… the vast landscape of theories finally came to be seen not as a freak result to be ignored but as a means of saving string theory from being falsified. Another reason the landscape idea took hold was, quite simply, that theorists were discouraged. They had spent a long time searching for a principle that would select a unique string theory, but no such principle had been discovered. Following the second revolution, string theory was now much better understood… The question … [was now] how to do physics with such a huge collection of theories. One response is to say that it’s impossible… If an attempt to construct a unique theory of nature leads instead to 10(to the 50th power), that approach has been reduced to absurdity. This is painful for many who have invented years and even decades of their working lives working in string theory… Still, even if it hurts like h_ll, acknowledging the reduction ad absurdum seems a rational and honest response to the situation… But it is not one that most string theorists choose.” (Pg. 158-159)
He summarizes, “On the basis of current results, we cannot confidently assert that string theory solves the problem of quantum gravity. The evidence is mixed… What we CAN say is that within these limitations there is some evidence that string theory points to the existence of a consistent unification of gravity and quantum theory. But is string theory itself that consistent unification? … it seems unlikely.” (Pg. 191) He adds, “string theory is certainly among the directions that deserve more investigation. But should it continue to be regarded as the dominant paradigm of theoretical physics? … I think the answer… must be no. String theory has not been successful enough on any level to justify putting nearly all our eggs in its basket… Some string theorists have advocated supporting string theory because it is ‘the only game in town.’ … In face there ARE other approaches…” (Pg. 199)
He argues, “There is good evidence that the progress of string theory itself has been slowed by a sociology that restricts the set of questions investigated and excludes the kind of imaginative and independent-minded scientists that progress requires.” (Pg. 268) He continues, “sociologists have no problem recognizing this phenomenon… which is called GROUPTHINK.” (Pg. 286)
He concludes, “We are indeed in a revolutionary period, but we are trying to get out of it by using the inadequate tools and organization of normal science… We are horribly stuck, and we need real seers… it has been a long time since seers were needed.” (Pg. 311) Later, he adds, “the real question is not why we have expended so much energy on string theory but why we haven’t expended nearly enough on alternative approaches.” (Pg. 349)
This book will be of great interest to those seeking critiques of string theory.
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