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Quantum Sense and Nonsense
Permeated by the author's delightful humor, this little book explains, with nearly no mathematics, the main conceptual issues associated with quantum The issue of determinism . Does quantum mechanics signify the end of a deterministic word-view? The role of the human subject or of the "observer" in science . Since Copernicus, science has increasingly tended to dethrone Man from his formerly held special position in the Universe. But quantum mechanics, with its emphasis on the notion of observation, may once more have given a central role to the human subject. The issue of locality . Does quantum mechanics imply that instantaneous actions at a distance exist in Nature? In these pages the author offers a variety of views and answers - bad as well as good - to these questions. The reader will be both entertained and enlightened by Jean Bricmont's clear and incisive arguments.
- GenresScienceNonfictionPhysics
298 pages, Paperback
Published November 8, 2017
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March 5, 2018
You wait years for a book on the interpretation of quantum physics, then two come along within a couple of months of each other. However, while both Quantum Sense and Nonsense and Philip Ball's Beyond Weird are aimed at a popular science audience (or popular sience as the back cover unfortunately categorises Jean Bricmont's book), they take a very different line. Without resorting to textbook levels of complexity, Quantum Sense and Nonsense goes into the quantum physics in considerably more depth, though at the cost of losing some readability.
Although Bricmont explains various quantum bits and pieces, such as the wave function, along the way, his focus throughout is on three key issues that need to be dealt with in getting an understanding of what the theory's really doing. These are the role of the observer, whether or not there is determinism (as opposed to true randomness) and whether or not locality holds - the alternative being what Einstein referred to as 'spooky action at a distance.'
This is also effectively a book in three acts. The first gives us background to what the problem with interpretation of quantum physics is, goes through the Copenhagen interpretation, and introduces the oddity of the two slit experiment. This is reasonably readable. There's then a centre section that fills in a lot of detail, which is harder going. Finally, there's the most approachable part in the last two chapters where Bricmont gives us a 'revised history' of quantum physics and considers its cultural impact.
What was particularly refreshing about this book is that it's the first I've ever read for a popular audience that properly explains the de Broglie-Bohm interpretation. It has to do this, as Bricmont is a relative rarity amongst physicists in being fully aware of it and supportive of it. He makes a convincing case that the interpretation was largely ignored because of Bohm's political views (he was effectively forced to leave the US for having communist leanings), and makes more sense than it is usually considered to.
There were a couple of examples where Bricmont seemed to verge on cherry picking to strengthen the pro-Bohm argument. He is very critical of those who try to combine quantum physics with Eastern mystical philosophy, yet plays down the fact that Bohm also did this (which was probably as much why his interpretation was ignored as his politics). More significantly, the book paints a picture of the Copenhagen interpretation in an early form where the role of the observer and measurement is very much about experiments, rather than interaction of quantum objects with the environment. If you are familiar with this aspect of quantum interpretation it seemed significant that the word 'decoherence' only appears once, and that was in a footnote.
Although it's not always the most reader-friendly text, I would recommend this title if you want to get a distinctly different picture of quantum physics and an understanding of why, even after 80-90 years, physicists may be happy with the results of the calculations, but still can't agree on what it all really means.
Although Bricmont explains various quantum bits and pieces, such as the wave function, along the way, his focus throughout is on three key issues that need to be dealt with in getting an understanding of what the theory's really doing. These are the role of the observer, whether or not there is determinism (as opposed to true randomness) and whether or not locality holds - the alternative being what Einstein referred to as 'spooky action at a distance.'
This is also effectively a book in three acts. The first gives us background to what the problem with interpretation of quantum physics is, goes through the Copenhagen interpretation, and introduces the oddity of the two slit experiment. This is reasonably readable. There's then a centre section that fills in a lot of detail, which is harder going. Finally, there's the most approachable part in the last two chapters where Bricmont gives us a 'revised history' of quantum physics and considers its cultural impact.
What was particularly refreshing about this book is that it's the first I've ever read for a popular audience that properly explains the de Broglie-Bohm interpretation. It has to do this, as Bricmont is a relative rarity amongst physicists in being fully aware of it and supportive of it. He makes a convincing case that the interpretation was largely ignored because of Bohm's political views (he was effectively forced to leave the US for having communist leanings), and makes more sense than it is usually considered to.
There were a couple of examples where Bricmont seemed to verge on cherry picking to strengthen the pro-Bohm argument. He is very critical of those who try to combine quantum physics with Eastern mystical philosophy, yet plays down the fact that Bohm also did this (which was probably as much why his interpretation was ignored as his politics). More significantly, the book paints a picture of the Copenhagen interpretation in an early form where the role of the observer and measurement is very much about experiments, rather than interaction of quantum objects with the environment. If you are familiar with this aspect of quantum interpretation it seemed significant that the word 'decoherence' only appears once, and that was in a footnote.
Although it's not always the most reader-friendly text, I would recommend this title if you want to get a distinctly different picture of quantum physics and an understanding of why, even after 80-90 years, physicists may be happy with the results of the calculations, but still can't agree on what it all really means.
June 18, 2024
AN ATTEMPT TO ANSWER MANY ‘MYSTERIES OF QUANTUM MECHANICS’
Jean Bricmont is a theoretical physicist and professor at the Université Cathollique de Louvain. He wrote in the Preface to this 2017 book, “There are many mysteries in contemporary physics, and some of them have been around for almost a century: What does quantum mechanics mean? What does it say about the world and about our place in it? Those mysteries have been used to justify a great deal of mysticism and have been associated with all kinds of religious, pseudo-scientific, philosophical, social, or even political doctrines. The goal of this book is to explain, in the least technical language possible, the reasons for these mysteries and a possible solution to them, as well as to dispel the mysticism that has surrounded quantum mechanics. In order to achieve these goals, we will have also to delve into the history and philosophy of science.”
In the first chapter, he adds, “Although this book belongs to the ‘popular physics’ category, its main purpose is cultural rather than scientific. We shall try to explain to the lay reader the basic principles of quantum theory, and emphasize their paradoxical nature, but our main goal is to unravel the incredible amount of confusion, pseudo-science and bad philosophy that accompanies most popular discussions of quantum mechanics. But this will also plunge us into the deepest questions about our understanding of the world and our place in it.” (Pg. 1)
He outlines, “There are three main conceptual issues associated with quantum mechanics, to which we shall refer below as being the ‘three fundamental questions’: 1. THE ROLE OF THE OBSERVER: … if the human observer has a role in shaping reality, one must ask how reality was shaped before humans existed… 2. THE ISSUE OF DETERMINISM: … quantum mechanical predictions are essentially statistical. This means that… quantum mechanics only assigns various probabilities to what the future state of that system may be. Does that imply that quantum mechanics signifies the end of a deterministic world-view? Does it explain or justify ‘free will’? 3. THE ISSUE OF LOCALITY: … There is nothing in our experience of the world that suggests that one might act instantaneously at a distance. However, in quantum mechanics the non-existence of instantaneous actions at a distance is not so obvious… does that justify beliefs such as telepathy?...
“A first goal of the book will be to explain why quantum mechanics has raised such issues and to give the traditional answers to those questions… On the other hand, the answers that we will try to defend in this book are… 1. THE ROLE OF THE OBSERVER: There is no need whatsoever to give a special role to the observer… to account for the quantum phenomena. 2. THE ISSUE OF DETERMINISM: There is a way to account for the quantum phenomena in a deterministic way, although a very special one… 3. THE ISSUE OF NONLOCALITY: Certain facts discovered thanks to quantum mechanics do imply that there exist in Nature instantaneous actions at a distance.” (Pg. 4-6)
About the ‘Schrödinger’s Cat’ thought experiment, he comments, “Some people think that quantum mechanics has proven that the poor cat is both alive and dead before anybody looks at it, and that looking at the cat ‘collapses’ its wave function… isn’t it reasonable to think that looking does not have any physical effect on the system itself and that by ‘looking’ we simply LEARN something about the state of the system, without changing it?... This… is the common-sensical solution to the cat problem and it is the one that Schrödinger had in mind.” (Pg. 73)
He notes, “there is an enormous literature arguing that the ‘lesson’ of quantum mechanics, or its ‘main innovation’ … is that we must abandon realism. Since we claim that the problems of quantum mechanics lie WITHIN THE PHYSICAL THEORY and are not to be solved by ‘changing’ our philosophy, we must discuss those claims and see what arguments can be given to support them. An important prerequisite to such a discussion is to define precisely what one means by expressions such as ‘realism.’ Indeed, much confusion in philosophy follows from the lack of precise definitions.” (Pg. 87)
He argues, “The fact that certain things are not ‘real’ does not mean that nothing is real. BUT… if one takes ordinary quantum mechanics as the final word about the universe, with the central role played by observations int that theory as being unavoidable, and with observations meaning observations BY US, humans (not by machines), then one can understand why [quantum] physicists … make the statements quoted above. But the most natural reaction would be to say that there is something seriously wrong with quantum mechanics, if one is led to such views. At the very least… the theory is fantastically successful, has lots of applications, but that we really do not understand what it all means.” (Pg. 97-98)
He points out. “nonlocality is there to stay. And refusing to face a problem is the same thing as solving it… nobody has proposed a genuinely local explanation for the perfect (anti-)correlations discussed here, and indeed nobody could do so, since [John] Bell has proven that it is impossible. To conclude, we have shown that some action at a distance does exist in Nature, but we have no idea what this action consists of. And we cannot answer the question without having a theory that goes beyond ordinary quantum mechanics…” (Pg. 121)
He says ‘To summarize: the answer to the question of the tension between relativity and nonlocality is both ‘no,’ if one means that this could allow the sending of messages into one’s own past, and ‘yes’: there is a serious problem if one wants to reconcile both ideas with a ‘causal’ view of the world, where there are causes and effects that where the former precede the latter in a sense that is independent of the state of motion relative to which those causes and effects are described.” (Pg. 131)
He proposes, “In the de Broglie-Bohm theory, particles have positions at all times, and therefore trajectories, and thus also velocities, independently of whether one measures them or not. The positions are, by convention, called the ‘hidden variables’ of the theory, because they are not include in the purely quantum description… In the de Broglie-Bohm theory the COMPLETE PHYSICAL STATE of a particle or a system of particles is given both by its wave function…AND the positions of the particles. They both change in time, in the following way: 1. The wave function evolves according to the usual laws, but NOTHING SPECIAL happens to it during measurements. 2. The motion of the particles is guided by their wave function…the velocity of a particle is a function of its wave function and its position, if we consider a single particle… [or] of the positions of all the other particles... The de Broglie-Bohm theory is sometimes called the ‘pilot wave’ theory, because the wave function tells the particle how to move.” (Pg. 139-140)
He acknowledges, “Reduction or collapse of the wave function in the de Broglie-Bohm theory … is just a practical impossibility, not an ‘in principle’ one… there is no fixed number for which there would be a sharp jump from a non-reduced wave function to a reduced one. So, in some sense, we do ‘collapse’ the wave function when we look at the result of an experiment. But this is only a practical matter… It is simply that one of the terms of the wave function no longer guides the motion of the particle…” (Pg. 155-156)
He summarizes, “By simply assuming that particles have positions … and that their motion is guided by the wave function…we have accounted for the interference phenomena in the double-slit experiment. By doing so, we have completely eliminated the role of the observer and we have done that within a deterministic theory. Could it be that the solution to all the conceptual problems of quantum mechanics is that simple? The answer is again yes and no. If one is interested in … non-relativistic quantum mechanics… then the answer is yes. But there is a part of physics dealing with waves rather than particles, like the electromagnetic waves… Moreover, it is crucial for that part of physics to take into account the theory of relativity. Therefore, a natural question for the de Broglie-Bohm theory … is whether there is an extension of [it] to the quantum theory of the electromagnetic waves… [which] incorporates the theory of relativity… The brief answer is that, yes there is a way… but there is no unique way to do that and it is not clear which extension is the best.” (Pg. 157)
He points out, “The many-worlds interpretation has a sort of charm that can excite our imagination… But these are must dreams: reality is much more complicated. The many-worlds interpretation does not give us any idea whatsoever of how many worlds there are, or what they look like. In principle, ‘all one has to do’ is to take the wave function of the entire Universe and find out how it evolves… this is easier said than done, since we have no idea whatsoever of what the wave function of the entire Universe is.” (P. 177)
He explains, “The root of the difference between Einstein and [Niels] Bohr is that Einstein was arguing at the level of WHAT THERE IS, insisting that a complete description of physical systems MUST go beyond the description given by ordinary quantum mechanics, if the world is local. Bohr, on the other hand, was answering systematically at the level of WHAT WE CAN KNOW. Bohr was not answering Einstein, he was simply not really listening to his objections.” (Pg. 187) Later, he adds, “We think that, in the debate between Bohr and Einstein… Bohr did not adequately answer Einstein’s ideas because he never really grasped the latter’s objections… That is why Bohr did not really refute the EPR paper… The dominant reaction was that Bohr had replied adequately to EPR and their argument was forgotten… the ignorance and misunderstanding of EPR led to the ignorance and misunderstanding of Bell.” (Pg. 206)
He concludes, “we try to argue throughout this book, a rational understanding of quantum mechanics is possible, although it requires a departure from the traditional textbook approaches to the subject… all we have to admit it that particles do follow trajectories, and they do so by following their wave function… But whatever one thinks of this way to solve the conceptual problems of quantum mechanics, own should at a minimum emphasize that quantum mechanics … does not imply anything whatsoever concerning the validity of telepathy, alternative medicines, Eastern philosophies, or the existence of God, and has no consequences whatsoever in regard to human affairs.” (Pg. 239)
This book will be of keen interest to those seeking ‘non-conventional’ approaches to quantum mechanics.
Jean Bricmont is a theoretical physicist and professor at the Université Cathollique de Louvain. He wrote in the Preface to this 2017 book, “There are many mysteries in contemporary physics, and some of them have been around for almost a century: What does quantum mechanics mean? What does it say about the world and about our place in it? Those mysteries have been used to justify a great deal of mysticism and have been associated with all kinds of religious, pseudo-scientific, philosophical, social, or even political doctrines. The goal of this book is to explain, in the least technical language possible, the reasons for these mysteries and a possible solution to them, as well as to dispel the mysticism that has surrounded quantum mechanics. In order to achieve these goals, we will have also to delve into the history and philosophy of science.”
In the first chapter, he adds, “Although this book belongs to the ‘popular physics’ category, its main purpose is cultural rather than scientific. We shall try to explain to the lay reader the basic principles of quantum theory, and emphasize their paradoxical nature, but our main goal is to unravel the incredible amount of confusion, pseudo-science and bad philosophy that accompanies most popular discussions of quantum mechanics. But this will also plunge us into the deepest questions about our understanding of the world and our place in it.” (Pg. 1)
He outlines, “There are three main conceptual issues associated with quantum mechanics, to which we shall refer below as being the ‘three fundamental questions’: 1. THE ROLE OF THE OBSERVER: … if the human observer has a role in shaping reality, one must ask how reality was shaped before humans existed… 2. THE ISSUE OF DETERMINISM: … quantum mechanical predictions are essentially statistical. This means that… quantum mechanics only assigns various probabilities to what the future state of that system may be. Does that imply that quantum mechanics signifies the end of a deterministic world-view? Does it explain or justify ‘free will’? 3. THE ISSUE OF LOCALITY: … There is nothing in our experience of the world that suggests that one might act instantaneously at a distance. However, in quantum mechanics the non-existence of instantaneous actions at a distance is not so obvious… does that justify beliefs such as telepathy?...
“A first goal of the book will be to explain why quantum mechanics has raised such issues and to give the traditional answers to those questions… On the other hand, the answers that we will try to defend in this book are… 1. THE ROLE OF THE OBSERVER: There is no need whatsoever to give a special role to the observer… to account for the quantum phenomena. 2. THE ISSUE OF DETERMINISM: There is a way to account for the quantum phenomena in a deterministic way, although a very special one… 3. THE ISSUE OF NONLOCALITY: Certain facts discovered thanks to quantum mechanics do imply that there exist in Nature instantaneous actions at a distance.” (Pg. 4-6)
About the ‘Schrödinger’s Cat’ thought experiment, he comments, “Some people think that quantum mechanics has proven that the poor cat is both alive and dead before anybody looks at it, and that looking at the cat ‘collapses’ its wave function… isn’t it reasonable to think that looking does not have any physical effect on the system itself and that by ‘looking’ we simply LEARN something about the state of the system, without changing it?... This… is the common-sensical solution to the cat problem and it is the one that Schrödinger had in mind.” (Pg. 73)
He notes, “there is an enormous literature arguing that the ‘lesson’ of quantum mechanics, or its ‘main innovation’ … is that we must abandon realism. Since we claim that the problems of quantum mechanics lie WITHIN THE PHYSICAL THEORY and are not to be solved by ‘changing’ our philosophy, we must discuss those claims and see what arguments can be given to support them. An important prerequisite to such a discussion is to define precisely what one means by expressions such as ‘realism.’ Indeed, much confusion in philosophy follows from the lack of precise definitions.” (Pg. 87)
He argues, “The fact that certain things are not ‘real’ does not mean that nothing is real. BUT… if one takes ordinary quantum mechanics as the final word about the universe, with the central role played by observations int that theory as being unavoidable, and with observations meaning observations BY US, humans (not by machines), then one can understand why [quantum] physicists … make the statements quoted above. But the most natural reaction would be to say that there is something seriously wrong with quantum mechanics, if one is led to such views. At the very least… the theory is fantastically successful, has lots of applications, but that we really do not understand what it all means.” (Pg. 97-98)
He points out. “nonlocality is there to stay. And refusing to face a problem is the same thing as solving it… nobody has proposed a genuinely local explanation for the perfect (anti-)correlations discussed here, and indeed nobody could do so, since [John] Bell has proven that it is impossible. To conclude, we have shown that some action at a distance does exist in Nature, but we have no idea what this action consists of. And we cannot answer the question without having a theory that goes beyond ordinary quantum mechanics…” (Pg. 121)
He says ‘To summarize: the answer to the question of the tension between relativity and nonlocality is both ‘no,’ if one means that this could allow the sending of messages into one’s own past, and ‘yes’: there is a serious problem if one wants to reconcile both ideas with a ‘causal’ view of the world, where there are causes and effects that where the former precede the latter in a sense that is independent of the state of motion relative to which those causes and effects are described.” (Pg. 131)
He proposes, “In the de Broglie-Bohm theory, particles have positions at all times, and therefore trajectories, and thus also velocities, independently of whether one measures them or not. The positions are, by convention, called the ‘hidden variables’ of the theory, because they are not include in the purely quantum description… In the de Broglie-Bohm theory the COMPLETE PHYSICAL STATE of a particle or a system of particles is given both by its wave function…AND the positions of the particles. They both change in time, in the following way: 1. The wave function evolves according to the usual laws, but NOTHING SPECIAL happens to it during measurements. 2. The motion of the particles is guided by their wave function…the velocity of a particle is a function of its wave function and its position, if we consider a single particle… [or] of the positions of all the other particles... The de Broglie-Bohm theory is sometimes called the ‘pilot wave’ theory, because the wave function tells the particle how to move.” (Pg. 139-140)
He acknowledges, “Reduction or collapse of the wave function in the de Broglie-Bohm theory … is just a practical impossibility, not an ‘in principle’ one… there is no fixed number for which there would be a sharp jump from a non-reduced wave function to a reduced one. So, in some sense, we do ‘collapse’ the wave function when we look at the result of an experiment. But this is only a practical matter… It is simply that one of the terms of the wave function no longer guides the motion of the particle…” (Pg. 155-156)
He summarizes, “By simply assuming that particles have positions … and that their motion is guided by the wave function…we have accounted for the interference phenomena in the double-slit experiment. By doing so, we have completely eliminated the role of the observer and we have done that within a deterministic theory. Could it be that the solution to all the conceptual problems of quantum mechanics is that simple? The answer is again yes and no. If one is interested in … non-relativistic quantum mechanics… then the answer is yes. But there is a part of physics dealing with waves rather than particles, like the electromagnetic waves… Moreover, it is crucial for that part of physics to take into account the theory of relativity. Therefore, a natural question for the de Broglie-Bohm theory … is whether there is an extension of [it] to the quantum theory of the electromagnetic waves… [which] incorporates the theory of relativity… The brief answer is that, yes there is a way… but there is no unique way to do that and it is not clear which extension is the best.” (Pg. 157)
He points out, “The many-worlds interpretation has a sort of charm that can excite our imagination… But these are must dreams: reality is much more complicated. The many-worlds interpretation does not give us any idea whatsoever of how many worlds there are, or what they look like. In principle, ‘all one has to do’ is to take the wave function of the entire Universe and find out how it evolves… this is easier said than done, since we have no idea whatsoever of what the wave function of the entire Universe is.” (P. 177)
He explains, “The root of the difference between Einstein and [Niels] Bohr is that Einstein was arguing at the level of WHAT THERE IS, insisting that a complete description of physical systems MUST go beyond the description given by ordinary quantum mechanics, if the world is local. Bohr, on the other hand, was answering systematically at the level of WHAT WE CAN KNOW. Bohr was not answering Einstein, he was simply not really listening to his objections.” (Pg. 187) Later, he adds, “We think that, in the debate between Bohr and Einstein… Bohr did not adequately answer Einstein’s ideas because he never really grasped the latter’s objections… That is why Bohr did not really refute the EPR paper… The dominant reaction was that Bohr had replied adequately to EPR and their argument was forgotten… the ignorance and misunderstanding of EPR led to the ignorance and misunderstanding of Bell.” (Pg. 206)
He concludes, “we try to argue throughout this book, a rational understanding of quantum mechanics is possible, although it requires a departure from the traditional textbook approaches to the subject… all we have to admit it that particles do follow trajectories, and they do so by following their wave function… But whatever one thinks of this way to solve the conceptual problems of quantum mechanics, own should at a minimum emphasize that quantum mechanics … does not imply anything whatsoever concerning the validity of telepathy, alternative medicines, Eastern philosophies, or the existence of God, and has no consequences whatsoever in regard to human affairs.” (Pg. 239)
This book will be of keen interest to those seeking ‘non-conventional’ approaches to quantum mechanics.
October 5, 2020
A simplified version of "Making sense of quantum mechanics" by the same author, which retains all main messages and devotes relatively more space to the philosophical, historical and sociological reasons for the standing condition of the perception of quantum mechanics - irrespective of the results of Bohm and Bell in particular, with whom the author is simpathetic. In his usual, concise, no-nonsense and clear style, Bricmont here gets to the heart of the matter very sharply, with hints of humor (perhaps also inherited by Bell) and constant focus on discerning what a real theory of quantum phenomena should do and should be versus what ordinary quantum mechanics does, it being not a theory as far as explanatory power but rather an algorithm to (shut up and) calculate results of laboratory experiments.
Ample suggested readings and references, and handy summaries of each chapter are also provided, which contribute to make this a great entry point to anyone willing to even only check whether most of the fuzz around "quantum" is legitimate or not (the answer being almost everywhere "not"). That said, this is a little too expensive, and works mostly as a non-technical reminder to "Making sense" for the non-beginner reader.
Ample suggested readings and references, and handy summaries of each chapter are also provided, which contribute to make this a great entry point to anyone willing to even only check whether most of the fuzz around "quantum" is legitimate or not (the answer being almost everywhere "not"). That said, this is a little too expensive, and works mostly as a non-technical reminder to "Making sense" for the non-beginner reader.
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