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Quantum Non-Locality and Relativity: Metaphysical Intimations of Modern Physics, Second Edition
Modern physics was born from two great revolutions: relativity and quantum theory. Relativity imposed a locality constraint on physical theories: since nothing can go faster than light, very distant events cannot influence one another. Only in the last few decades has it become clear that quantum theory violates this constraint. The work of J. S. Bell has demonstrated that no local theory can return the predictions of quantum theory. Thus it would seem that the central pillars of modern physics are contradictory. Quantum Non-Locality and Relativity examines the nature and possible resolution of this conflict. Beginning with accurate but non-technical presentations of Bell's work and of Special Relativity, there follows a close examination of different interpretations of relativity and of the sort of locality each demands. The story continues with a brief discussion of the General Theory of Relativity. This second edition also includes a new author's preface and an additional appendix. The book introduces philosophers to the relevant physics and demonstrates how philosophical analysis can help to resolve some of the problems. All of the physics is presented from first principles, and as much as possible is presented pictorially.
296 pages, Paperback
First published January 1, 1994
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October 3, 2015
So. I have a bone or two to pick with this book. Yes I gave it four stars (tbh I wanted to give it 3.5 stars but I'm choosing to round up) because it improved towards the end and, for all the rage I felt when reading chapters 3 & 4, this book still has value. But I swear to God there were times (particularly in the middle of the book) where I wanted to scream at Maudlin. I kept returning to the (glowing) reviews on the Goodreads page, praising how accessible this book is and I kept muttering to myself, are all these people really reading the same book that I am? Did these reviewers actually bother reading through the book properly or did they just skim the surface of Maudlin's exposition and go, "Oh! Quantum Physics and relativity has, like, consistency issues because of the quantum correlations that violate Bell's Inequalities and it's suuuuuper hard to derive a coherent interpretation. This is like super deep stuff, man."
Well, to paraphrase what Hilary Putnam told a philosophy professor of mine: Any understanding of the world that can be put in a nutshell deserves to be put in one.
So what drove me up the wall? I've found that I absolutely cannot tolerate it when a writer introduces new terminology without properly defining what the hell they are. The first two chapters are fine - I remember feeling very happy with what I was reading, and pleased that the mathematics regarding polarizers and Lorentz transformations were simple enough to handle; but by the time I got to chapters 3 and 4, the reading experience just became incredibly tiresome and frustrating when I would have to wade through terminologies and new concepts like "Godel's Universe", "commutators" etc., stuff which was just thrown into the discussion in a very ad hoc manner, and this was incredibly offputting because as a reader who only has a rather general understanding of physics (I have some mathematical background and I did the PHYS 130s sequence in UChicago), I was already having to put in a decent amount of effort into trying to (1) follow Maudlin's arguments, and (2) keep the bigger picture in mind.
Now if this was a book intended for the specialist, then I'd be less angry and acknowledge that perhaps I needed some foundational knowledge in order to properly appreciate the merits of this book. Except that Maudlin writes this in the introduction:
Yes, Monsieur, the Key-word is "non-specialist". So, suffice it to say, I did not appreciate it when I would be repeatedly ambushed by statements like:
Especially since "isotropy" was not defined earlier.
Maudlin also writes that:
I appreciate the difficulty that Maudlin that faces, and it is this balancing act that leads to the occasionally annoying situation where a bunch of mathematics are strewn together without much of an explanation (e.g. in the technical interlude on pages 78-9, why would the change in the Hamiltonian operator A with respect to parameter b be defined as a commutator?). I can sympathise with this, however there were other times where Maudlin's exposition suffered from some unclarity that had nothing to do with this. For instance, in Chapter 3, Maudlin explains why particles cannot accelerate beyond the speed of light by the following:
He later then goes on to introduce Tachyons, or superluminal particles:
Now, intuitively, given his earlier explanation about why particles cannot travel beyond the so-called light barrier (e.g. it would require infinite amounts of energy to offset the infinite increase in mass), wouldn't Tachyons face the same problem as well? Why does it require infinite amounts of energy to accelerate subluminal particles near light speed but Tachyons are able to travel at superluminal velocities just fine?
After 5 mins worth of googling, I realised that the answer had to do with the equation m*[(1− v^2/c^2)^(-0.5)] (where m describes the object's rest mass, v its velocity and c the speed of light), which Maudlin had quoted before on numerous occasions. The reason why light's velocity acts a constraint to both subluminal and superluminal particles is because the closer some given particle's velocity gets to the speed of light, the whole equation approaches a singularity. Maudlin didn't state anything wrong in these pages, but he should have made the equation much more central to his explanation of what was going on. Perhaps he could have discussed the relevant constraints on particle velocity with regards to light's velocity the same way he discussed the probabilities of a photon passing or getting absorbed by a polarizer, i.e. by drawing a graph, illustrating the equation.
Sidenote: I did, however, appreciate the generalised version of Bell's Theorem presented in Chapter 4 and I thought that the proof was clever. I want to point out a tiny lemma which Maudlin uses to create the bounds of the generalised form of Bell's inequalities:
Maudlin's proof of this lemma appeals to how the given equation is a linear function of its four variables and how it takes its extreme values at the extreme ends of its domain. I think there's a more intuitive and straightforward way of proving this. Here's my proof of the Lemma:
So what did I like about this book? I think, for all its sins, it's a book that has moments of clarity and does a lot of useful conceptual housekeeping, particularly when it comes to taking stock of the physicists' attempts to design a relativistic theory that accommodates the violations of Bell's Inequalities (e.g. John Cramer's backward-and-forward hypothesis, many-minds ontology, relativistic flashy GRW etc.), and always making sure to identify what epistemic price we pay by opting for one interpretation of the results over another. Further, if Maudlin has not strawmanned the arguments put forward by the various noted physicists on this issue, then I think I feel safer in Maudlin's hands than in these physicists since some of their ideas seem very wishy-washy and dissatisfyingly speculative to me.
The structure of this book is also sensible, which is certainly a plus; these chapters build upon each other and explore different nooks and crannies in trying to weld together a coherent interpretation of the physical universe given the presentation of the problem in Chapter 1. Within the chapters themselves, Maudlin usually provides a good motivation for the important issues at hand, he asks sensible questions about their implications whilst also building up enough machinery for detailed analysis.
I also think that the new Chapter 10 is very good, and its addition to the 3rd edition of this book is a welcome one. It certainly gives a very helpful bird's eye view on where modern physics is at the moment. (Also, for some reason, I found Maudlin a little less stingy when it comes to providing the general reader with intuition in this chapter - perhaps it might've been because I already went through the fire of the earlier chapters, so I found the material less frustrating, but I think that Maudlin did make a conscientious effort to reduce the opacity of his exposition. Thumbs up for that, Maudlin.)
As a final note, I did finish this book wishing for more information about the "metaphysical intimations" of modern physics, beyond just examining the ontology presupposed by the various relativistic theories (e.g. the matter density ontology, the flash ontology etc.), but I think Maudlin addresses this in a later book, titled "The Metaphysics within Physics". I look forward to reading that.
Well, to paraphrase what Hilary Putnam told a philosophy professor of mine: Any understanding of the world that can be put in a nutshell deserves to be put in one.
So what drove me up the wall? I've found that I absolutely cannot tolerate it when a writer introduces new terminology without properly defining what the hell they are. The first two chapters are fine - I remember feeling very happy with what I was reading, and pleased that the mathematics regarding polarizers and Lorentz transformations were simple enough to handle; but by the time I got to chapters 3 and 4, the reading experience just became incredibly tiresome and frustrating when I would have to wade through terminologies and new concepts like "Godel's Universe", "commutators" etc., stuff which was just thrown into the discussion in a very ad hoc manner, and this was incredibly offputting because as a reader who only has a rather general understanding of physics (I have some mathematical background and I did the PHYS 130s sequence in UChicago), I was already having to put in a decent amount of effort into trying to (1) follow Maudlin's arguments, and (2) keep the bigger picture in mind.
Now if this was a book intended for the specialist, then I'd be less angry and acknowledge that perhaps I needed some foundational knowledge in order to properly appreciate the merits of this book. Except that Maudlin writes this in the introduction:
My foremost goal in composing the book has been to make it comprehensible to the non-specialist. [...] Unfortunately, much of the work done by philosophers presupposes a considerable amount of familiarity with the physics. This is particularly sad since the physics is not, in most cases, very complicated. (Maudlin, vii)
Yes, Monsieur, the Key-word is "non-specialist". So, suffice it to say, I did not appreciate it when I would be repeatedly ambushed by statements like:
It is true that the signal propagation may be isotropic only in the rest frame of the emitter, but so too are water waves isotropic only in the rest frame of the water. The laws of nature do not pick out any particular frame, only the distribution of matter does. (Maudlin, 94)
Especially since "isotropy" was not defined earlier.
Maudlin also writes that:
"I fear that many readers may be frightened off from the topic by unnecessary formalization, so I have tried to keep the mathematical complexity of the discussion to a minimum. But on the other hand, I have not wished to drop to the level of vague metaphor which sometime infects popularizations. Every compromise between rigor and simplicity is a bargain with the devil. (Maudlin, vii)
I appreciate the difficulty that Maudlin that faces, and it is this balancing act that leads to the occasionally annoying situation where a bunch of mathematics are strewn together without much of an explanation (e.g. in the technical interlude on pages 78-9, why would the change in the Hamiltonian operator A with respect to parameter b be defined as a commutator?). I can sympathise with this, however there were other times where Maudlin's exposition suffered from some unclarity that had nothing to do with this. For instance, in Chapter 3, Maudlin explains why particles cannot accelerate beyond the speed of light by the following:
"Furthermore, as the velocity approaches the speed of light, the mass approaches infinity, and hence it requires unbounded amounts of energy to get the particle to go faster. Given that only finite amounts of energy are available, it would follow that no particle which travels below the speed of light can ever be accelerated to, or beyond, that speed. So the speed of light does serve as a limit on the velocities of particles which start out traveling at sublight speeds". (Maudlin, pg. 63)
He later then goes on to introduce Tachyons, or superluminal particles:
"The Lorentz transformations and the relativistic mass increase do not per se rule out superluminal particles (tachyons), but only prohibit the acceleration of particles through the light barrier. Tachyons must be born traveling faster than light and (as we will see) cannot be slowed to sublight speeds." (Maudlin, pg. 65)
Now, intuitively, given his earlier explanation about why particles cannot travel beyond the so-called light barrier (e.g. it would require infinite amounts of energy to offset the infinite increase in mass), wouldn't Tachyons face the same problem as well? Why does it require infinite amounts of energy to accelerate subluminal particles near light speed but Tachyons are able to travel at superluminal velocities just fine?
After 5 mins worth of googling, I realised that the answer had to do with the equation m*[(1− v^2/c^2)^(-0.5)] (where m describes the object's rest mass, v its velocity and c the speed of light), which Maudlin had quoted before on numerous occasions. The reason why light's velocity acts a constraint to both subluminal and superluminal particles is because the closer some given particle's velocity gets to the speed of light, the whole equation approaches a singularity. Maudlin didn't state anything wrong in these pages, but he should have made the equation much more central to his explanation of what was going on. Perhaps he could have discussed the relevant constraints on particle velocity with regards to light's velocity the same way he discussed the probabilities of a photon passing or getting absorbed by a polarizer, i.e. by drawing a graph, illustrating the equation.
Sidenote: I did, however, appreciate the generalised version of Bell's Theorem presented in Chapter 4 and I thought that the proof was clever. I want to point out a tiny lemma which Maudlin uses to create the bounds of the generalised form of Bell's inequalities:
"If x′, x′′, y′ and y′′ are all numbers that lie between -1 and 1 (inclusive), then the quantity x′y′ + x′y′′ + x′′y′ - x′′y′′ lies between -2 and 2 (inclusive)"
Maudlin's proof of this lemma appeals to how the given equation is a linear function of its four variables and how it takes its extreme values at the extreme ends of its domain. I think there's a more intuitive and straightforward way of proving this. Here's my proof of the Lemma:
Case 1: y' > y''
(i) x'y' + x'y'' + x''y' - x''y''
= x'*(y' + y'') + x''*(y'-y'')
≤ y' + y'' + y' - y''
≤ y' + y' = 2y' ≤ 2
(ii)
x'y' + x'y'' + x''y' - x''y''
= x'*(y' + y'') + x''*(y'-y'')
≥ -(y' + y'') - (y'-y'')
= - y' - y' = -2y' ≥ -2
By (i) and (ii), -2 ≤ x'y' + x'y'' + x''y' - x''y''≤ 2 if y' > y''.
Case 2: y' = y''
Then: x'y' + x'y'' + x''y' - x''y'' = x'(2y')
= 2(x'y'), which is obviously bounded by -2 and 2.
Case 3: y' < y''
(i) x'y' + x'y'' + x''y' - x''y''
= x'*(y' + y'') + x''*(y'-y'')
≤ y' + y'' + y' - y''
≤ y' + y' = 2y' ≤ 2
(ii)
x'y' + x'y'' + x''y' - x''y''
= x'*(y' + y'') + x''*(y'-y'')
≥ -(y' + y'') + (y'-y'')
= - y'' - y'' = -2y'' ≥ -2
By Cases 1 - 3, we prove the stated lemma as above.
So what did I like about this book? I think, for all its sins, it's a book that has moments of clarity and does a lot of useful conceptual housekeeping, particularly when it comes to taking stock of the physicists' attempts to design a relativistic theory that accommodates the violations of Bell's Inequalities (e.g. John Cramer's backward-and-forward hypothesis, many-minds ontology, relativistic flashy GRW etc.), and always making sure to identify what epistemic price we pay by opting for one interpretation of the results over another. Further, if Maudlin has not strawmanned the arguments put forward by the various noted physicists on this issue, then I think I feel safer in Maudlin's hands than in these physicists since some of their ideas seem very wishy-washy and dissatisfyingly speculative to me.
The structure of this book is also sensible, which is certainly a plus; these chapters build upon each other and explore different nooks and crannies in trying to weld together a coherent interpretation of the physical universe given the presentation of the problem in Chapter 1. Within the chapters themselves, Maudlin usually provides a good motivation for the important issues at hand, he asks sensible questions about their implications whilst also building up enough machinery for detailed analysis.
I also think that the new Chapter 10 is very good, and its addition to the 3rd edition of this book is a welcome one. It certainly gives a very helpful bird's eye view on where modern physics is at the moment. (Also, for some reason, I found Maudlin a little less stingy when it comes to providing the general reader with intuition in this chapter - perhaps it might've been because I already went through the fire of the earlier chapters, so I found the material less frustrating, but I think that Maudlin did make a conscientious effort to reduce the opacity of his exposition. Thumbs up for that, Maudlin.)
As a final note, I did finish this book wishing for more information about the "metaphysical intimations" of modern physics, beyond just examining the ontology presupposed by the various relativistic theories (e.g. the matter density ontology, the flash ontology etc.), but I think Maudlin addresses this in a later book, titled "The Metaphysics within Physics". I look forward to reading that.
February 17, 2018
A thorough examination of the apparent conflict between the Lorentz invariance of special relativity and the Bell inequality violation of quantum mechanics. Maudlin shows that Lorentz invariance by itself isn't enough to rule out superluminal transmission of matter, energy, signals, information, or causal influences; that Bell inequality violation doesn't require superluminal transmission of matter, energy, or signals, but does require superluminal information transfer and causal influence. As pointed out in Chapter 3, tachyons (superluminal particles) are consistent with Lorentz invariance but turn out to be inadequate for mediating the superluminal causal influences in quantum systems. In particular, despite the possibility of Lorentz invariant superluminal behavior, any description of Bell inequality violation (illustrated throughout mostly by polarization measurements of a pair of photons entangled in a singlet state) seems to require some spacetime structure beyond the Minkowski metric, which violates Lorentz invariance.
In the end, we're left with a number of options: we can reconcile this conflict by rejecting counterfactual definiteness (and embracing a many-worlds or many-minds interpretation, although Maudlin regards the former as incoherent), positing some form of retrocausation, a scheme called "hyperplane dependence", or simply rejecting Lorentz invariance as a fundamental fact about spacetime (which requires that we explain why spacetime appears Lorentz invariant most of the time). The last chapter also describes a recent discovery: the "flash ontology" for GRW theory (a stochastic dynamical collapse quantum theory) seems to provide a Lorentz invariant description of Bell inequality violation. Maudlin seems to think "flashy GRW" is sufficiently counterintutive that we should not necessarily consider it more appealing than the above options.
In the end, we're left with a number of options: we can reconcile this conflict by rejecting counterfactual definiteness (and embracing a many-worlds or many-minds interpretation, although Maudlin regards the former as incoherent), positing some form of retrocausation, a scheme called "hyperplane dependence", or simply rejecting Lorentz invariance as a fundamental fact about spacetime (which requires that we explain why spacetime appears Lorentz invariant most of the time). The last chapter also describes a recent discovery: the "flash ontology" for GRW theory (a stochastic dynamical collapse quantum theory) seems to provide a Lorentz invariant description of Bell inequality violation. Maudlin seems to think "flashy GRW" is sufficiently counterintutive that we should not necessarily consider it more appealing than the above options.
March 30, 2016
For those, like me, who have been troubled over the decades by violations of Bell inequality, then this is a must read. This is true even if the competence you bring to the book is limited.
Requisites:
For a full critical understanding--which I did not obtain--you should understand calculus to the point of partial derivatives and should also know probability notation. Without this, the gist of arguments can be understood by anyone who does not shy away from symbolic presentations and logic (assuming a very minimal numeracy).
Appendix B, an introduction to quantum mechanics, will give one a sufficient understanding of vector states, and some generalities about classes of operators that affect their evolution (without going into unneeded detail about Hamiltonian operators). For those whose education (but not aptitude) was less numerate, one read won't suffice; I flipped back and re-read selected passages. (It is not however a reference and is never intended to be one.)
The author is a philosophy professor but he avoids having the field's terminology obscure his presentation. If one isn't already familiar with evaluating causation through counterfactuals, one can pick it up contextually. More sophisticated understanding of this and a few other issues are only needed if one wishes to follow the defensive arguments the author mounts against potential attacks from his peers.
Substance:
The author shows quite convincingly that the violations of Bell inequality (and the broader issue that was tersely represented by Bell) create deep problems (although a few claimed problems are dismissed with equal authority). He shows too, illustrated with Bohm's heretical mechanics, that the deep problems plague determinate theories as much as stochastic ones. (Bohm's physics is well presented in a chapter appendix.) Attempts to reconcile the empirical results with special relativity are shown to spin off into wildness, only to be made worse by extension to general relativity. No attempt is made to choose among the purported solutions; rather the author indicates that they lack clear criteria for preference, and hints at the possible inadequacy of the attempted reconciliation.
In the end:
It will not cure one's distress about entanglement operating between space-like-separated events, but one will have a more mature appreciation of the dilemma; this is the best that can be offered today.
Requisites:
For a full critical understanding--which I did not obtain--you should understand calculus to the point of partial derivatives and should also know probability notation. Without this, the gist of arguments can be understood by anyone who does not shy away from symbolic presentations and logic (assuming a very minimal numeracy).
Appendix B, an introduction to quantum mechanics, will give one a sufficient understanding of vector states, and some generalities about classes of operators that affect their evolution (without going into unneeded detail about Hamiltonian operators). For those whose education (but not aptitude) was less numerate, one read won't suffice; I flipped back and re-read selected passages. (It is not however a reference and is never intended to be one.)
The author is a philosophy professor but he avoids having the field's terminology obscure his presentation. If one isn't already familiar with evaluating causation through counterfactuals, one can pick it up contextually. More sophisticated understanding of this and a few other issues are only needed if one wishes to follow the defensive arguments the author mounts against potential attacks from his peers.
Substance:
The author shows quite convincingly that the violations of Bell inequality (and the broader issue that was tersely represented by Bell) create deep problems (although a few claimed problems are dismissed with equal authority). He shows too, illustrated with Bohm's heretical mechanics, that the deep problems plague determinate theories as much as stochastic ones. (Bohm's physics is well presented in a chapter appendix.) Attempts to reconcile the empirical results with special relativity are shown to spin off into wildness, only to be made worse by extension to general relativity. No attempt is made to choose among the purported solutions; rather the author indicates that they lack clear criteria for preference, and hints at the possible inadequacy of the attempted reconciliation.
In the end:
It will not cure one's distress about entanglement operating between space-like-separated events, but one will have a more mature appreciation of the dilemma; this is the best that can be offered today.
December 30, 2013
Maudlin is quite detailed and aware of the importance in a process of accumulating prior information from the previous chapters which makes the apprehension of both quantum mechanics and of special relativity a fairly easy task. The mathematical tools are simple linear equations and Lorentz transformations. Perhaps the greatest part of the book is that it delves into questions that usually physicists tend to either brush off or be completely ignorant about, that is to say the nature and compatibility of both theories in physics. This book certainly has a very concise and well-argued for thesis regarding the conceptual foundations of each theories and allows us to reflect more on the implications of modern physics rather than having the attitude of some physicists which is to just "shut up and calculate". It is primarily a work in the philosophy of physics.
November 13, 2014
I really liked this book. For almost a month this book has been my daily reading on my way to and back from work. The book offers a very good introduction to the Bell inequality and the incompatibility of quantum mechanics and relativity. I think the author succeeds in his aim: To give an accessible introduction that avoids the trap of falling into too many technical details that obscure the big picture. This does not mean that the book is not demanding, it definitely is for those with no prior knowledge about quantum mechanics and relativity! But with some effort it is quite accessible, and definitely enjoyable and intriguing.
August 19, 2020
Posted at: https://bartsdotblog.wordpress.com/20...
In order to properly review Quantum Non-Locality and Relativity: Metaphysical Intimations of Modern Physics by Tim Maudlin, I need to introduce you to a concept called nonlocality.
Nonlocality is one of the three most mind-blowing concepts I have ever contemplated. It frequently keeps me up at night, wondering what it really means.
In a previous discussion about the theory of relativity, I noted how difficult it would be for a group of intelligent snails living in a jungle to understand centrifugal force, which is the force we feel as we slide sideways in our seats when we take curved highway exits at high speeds.
At the slow speeds that snails walk, they simply cannot generate enough momentum to experience centrifugal force. And thus it would be very difficult for them to consider such a force “real.”
Snail, Shell, Mollusk, Probe, Mucus, Crawl, Slowly
Humans face a similar problem when it comes to the concepts of relativity and nonlocality, which manifest themselves only incredibly fast speeds (relativity) and tiny microscopic levels (nonlocality).
Just like snails are too slow to experience centrifugal force, we are too big to experience nonlocality in ways that are readily noticeable.
A good way to explain nonlocality is to draw a contrast with its mirror opposite. The concept of locality means that everything we interact with has a cause and effect that involves a force transmitted through physical space according to the known laws of nature.
In other words, when locality is at work, any cause you can think of must be physically connected to whatever it affects, be that by physical particle or electromagnetic wave.
For example, if you roll a bowling ball and it hits some pins we can clearly trace the causal chain of events: You used your muscles and your hand to propel a ball that rolled along the floor until it hit the pins. If your bowling alley was one mile long and sloped slightly downhill it would take your ball a few minutes to roll all the way there. But so long as you rolled the ball straight enough to avoid the gutters, it would eventually knock over the pins.
In such a situation your bowling ball cannot physically cause the pins to fall over until the ball arrives and touches the pins. The force that knocks over the pins takes the form of the momentum that is carried by the ball from you to the pins. There needs to be physical contact between the ball and the pins to transfer that force. (We calculate the force using your old friend, the formula of force = mass x acceleration.)
Bowling, Bowler, Pins, Ball, Alley, Sport, Fun
So, how could we possibly explain what happened if you rolled the ball and then half a second later the pins fell over — several minutes before the rolling ball arrived? What if the pins fell down while the ball was still rolling? The answer would surely have to be that some other force acted locally on the pins, such as a gust of wind or vibrations in the floor.
Perhaps the pins were precariously balanced and it was the hard bang of the ball hitting the floor that caused a vibration wave to propagate through the wood and knock the pins over. Whatever explanation we come up with must include some type of force or particle traveling through space. All of this is another way of saying that everything we have ever observed in our lives has obeyed the principle of locality.
If we shift to using beams of light in a thought experiment, the same principle applies. If we shine an unimaginably powerful laser from Earth onto the surface of the Moon it would take 2.54 seconds for the laser light to reach the Moon, and bounce back into our eyeballs. We are causing a spot on the moon to illuminate via the mechanism of light physically traveling from here to there.
But, how could we possibly explain what happened if a red dot appears on the moon less than a half a second after we shined our laser, instead of more than two seconds? By definition light cannot travel faster than the speed of light.
Illustration of Moon Showing during Sunset
The answer is that we would hunt for alternative explanations.
A possibility could be that someone is playing a trick on us by shining their own powerful laser at the same spot right before we turn on ours. But there would be ways to test whether that is happening. For example, we could turn our laser on at random intervals, which would be hard for a trickster to anticipate. Or we could modulate our laser to send short pulses of light that could be translated into the dots and dashes of Morse Code.
But what if our message seemed to reflect back from the Moon’s surface faster than allowed by the speed of light?
At that point we should probably not assume that we had somehow violated the speed of light which is a known constant, scientifically validated over and over and over. The speed of light is the well known C in the famous equation E=MC2 that makes possible our understanding of nuclear power and weapons and the structure of space-time itself.
As we searched for explanations we might suspect that a trickster guessed the Morse Code message we would send, and he would send it first. Perhaps he hacked our computer so that as soon as we put in our message, the computer would transmit our message to him first which would allow him to transmit two seconds before we did.
If any of these explanations were true they would be called locality-based explanations because they all expose how the trickster found a way to send his message first.
At some point, however, if we eliminated every possible explanation we would need to start considering seemingly impossible explanations. Maybe our trickster built a tiny satellite that looked exactly like the Moon, and was in orbit only 1,200 miles above the Earth as opposed to 240,000 miles away? That could partially explain things.
But even if we can’t figure out how it is happening, we continue to be confident that there has to be some reasonable explanation. Because there is just no way that we could be violating the speed of light.
Right?
This image has an empty alt attribute; its file name is road-4088226_1280.jpg
Well. This is where we get to the idea of nonlocality.
Scientists have discovered that if we take a pair of tiny particles, such as photons, and we entangle them by shining them through a certain type of crystal, those two particles can develop a connection that transcends space and time in ways that allows the particules to communicate instantaneously no matter how far apart they are.
When I say instantaneously, I mean instantaneously in ways that are clearly in conflict with the speed of light, and are unexplainable by classical physics. For the first time, we seemed to have evidence of truly nonlocal behavior in which cause and effect were not connected by a known force traveling through known space.
When this concept first came to light, Albert Einstein could not accept that quantum physics could involve nonlocality. Einstein derisively called this phenomenon “spooky action at a distance” and set out to prove that there must be some yet-undiscovered local explanation for a seemingly nonlocal phenomenon.
Albert Einstein, Portrait, Theoretician Physician
For example, if you and I are criminal collaborators who get get separated, we could agree in advance to stick to a certain story such that if we were concurrently interrogated by different detectives we would give the same answers.
in 1935, Einstein and two of his peers (Podolsky and Rosen) published a thought experiment titled “Can Quantum-Mechanical Description of Physical Reality be Considered Complete?” In this famous paper they argued that the claim by quantum physicists of nonlocality being a real thing . . . . must be incomplete. Einstein and his pals used numerous fancy words but their point was unmistakably simple: We may not know what is missing, but you people are definitely missing something important. Your nonlocality theory is bananas.
For decades, physicists and philosophers argued about what the quantum physicists could possibly be missing. Nobody could think of anything. Many physicists felt in their gut that Einstein was right, even as experimental evidence mounted that he was wrong.
After all, nothing travels faster than light, and it takes at least three minutes for light to travel from Earth to Mars. So, it can’t possibly be true that if you do push a button on Earth it could cause anything to happen instantaneously on Mars. Because there is no known physical mechanism known that would allow for the transmission of that signal.
In 1964, John Stewart Bell wrote a famous paper that addressed these issues with more rigor than anyone before. He set out to investigate whether there was any way to solve the nonlocality problem by finding hidden variables such as particles somehow “agreeing” in advance to show certain behaviors under questioning by scientist detectives in laboratories distant from each other.
Bell showed that it was possible to create situations in which no possible “hidden variables” could resolve the paradox. The explanation is technical but Bell’s logic was airtight: Nonlocality is somehow real, even if it makes us uncomfortable and we do not understand how it works.
Cube, Escher, Gradient, Mc Escher, Optical Illusion
Over the following decades physicists and philosophers have continued to ask themselves what the hell is going on and how can we possibly understand it? They have performed thousands of experiments with increasingly powerful and sophisticated equipment. They have discussed and debated and hypothesized. And still they are not sure what the hell is going on, though they are getting closer.
In Quantum Non-Locality and Relativity: Metaphysical Intimations of Modern Physics, author Tim Maudlin takes us through an investigation that is unbelievably rigorous. He takes us through an incredibly careful re-telling of history, re-explaining relativity, the structure of space-time, Euclidian space, invariant quantities, Newtonian Space-time, Galilean Space-time, special relativity, and the fascinating concept of Lorentz Transformations that explain how objects physically change shape as they approach the speed of light.
Maudlin then spends chapter after chapter exploring in great detail every possible mechanism that could explain away nonlocality. Superliminal matter transport? Tachyons? Secret messages? Lorentz Invariant Collapse Theories? Preferred sets of hyperplanes? Non-Minkowski Space-time? Check, check, check, check, check, check, and no, no, no, no, no no.
Interestingly, Maudlin is not a physicist, but rather a philosopher. His book is exceedingly difficult and there is plenty of math. But you needn’t actually understand vector spaces, eigenvalues, and orthnormal bases in order to follow most of his reasoning.
Quantum Non-Locality and Relativity: Metaphysical ...
Across his chapters Maudlin presents one theory after another and discusses the strengths and weaknesses of each theory. One thing that he makes clear, however, is that you cannot have your cake and eat it too. He explores both determinate theories and stochastic theories that each appear to have something going for them — and also appear to have fatal flaws. He leaves it up to you to decide which fundamental truths you will cling to, while making it clear that at least one thing you believe is almost certainly completely wrong. He just does not know which one.
Reading this book made me realize that at least one of several mind-blowing possibilities is highly like to be true:
First, some microscopic particles may be able to move briefly backwards in time via “closed timelike curves” that allow them to interfere with themselves. If this is true it could beautifully explain the mysterious wave-particle duality experiments in which particles appear to interfere with themselves to create interference patterns.
Second, spacetime could be far more complex than it appears. There may be additional physical dimensions that we have yet to discover, and it may be possible that particles that seem physically distant from each other are in fact “touching” via a dimension that we cannot yet see or understand.
Third, the “many-worlds interpretation” may be correct. I hate this idea so much that I will not even describe it.
Fourth, we could be living in a simulation, and the concept of nonlocality could be programmed into our operating system.
Fifth, the “flashy GRW” theory described near the end of the book could be correct. Unfortunately I do not understand it well enough to summarize it here.
Wave, Particles, Physics, Abstract
As Maudlin says at the end of his book:
We are in a methodological quandary. It is hard to imagine a neutral methodological principle that could militate in favor of retaining a pre-existing theory of space-time at all costs, while allowing for the abandonment of an equally entrenched pre-existing theory of space-time at all costs, while allowing for the abandonment of an equally entrenched pre-existing account of the local distribution of matter at the scale which we think is probed by microscopes. The microscopic distribution of matter is not open to our direct inspection, but neither is the structure of space-time at any scale. And if you accept a many-worlds picture, then even the local macroscopic distribution of matter is not open to immediate inspection: most of the matter in any given region is invisible to us. So all of our options — adding a foliation, flashy GRW, many-worlds interpretation that denies unique outcomes — one way or another postulates a physical world that shields itself from our view. Each one asserts that the natural conclusions of what seem to be straightforward scientific investigations somehow go radically awry. One way or another, the world is not at all what it appears to be.
Overall, this book is as difficult as it is interesting. The concepts it discusses are fascinatingly thought-provoking. I expect to read it several more times and still not understand parts. Until then I will hope that Maudlin eventually writes a fourth edition that includes new chapters to describe what our theoretical and experimental physicists are learning right now.
Until then, I will not rest easy, because I am burning with desire to understand how it can be that a particle on Mars can communicate instantly with a particle on Earth.
Bart Epstein, June 2020
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Published by bart315
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June 14, 2020
Quantum Mechanics
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3 thoughts on “What is Quantum Non-Locality?”ADD YOURS
Eilon Poem
June 17, 2020 at 1:48
In order to properly review Quantum Non-Locality and Relativity: Metaphysical Intimations of Modern Physics by Tim Maudlin, I need to introduce you to a concept called nonlocality.
Nonlocality is one of the three most mind-blowing concepts I have ever contemplated. It frequently keeps me up at night, wondering what it really means.
In a previous discussion about the theory of relativity, I noted how difficult it would be for a group of intelligent snails living in a jungle to understand centrifugal force, which is the force we feel as we slide sideways in our seats when we take curved highway exits at high speeds.
At the slow speeds that snails walk, they simply cannot generate enough momentum to experience centrifugal force. And thus it would be very difficult for them to consider such a force “real.”
Snail, Shell, Mollusk, Probe, Mucus, Crawl, Slowly
Humans face a similar problem when it comes to the concepts of relativity and nonlocality, which manifest themselves only incredibly fast speeds (relativity) and tiny microscopic levels (nonlocality).
Just like snails are too slow to experience centrifugal force, we are too big to experience nonlocality in ways that are readily noticeable.
A good way to explain nonlocality is to draw a contrast with its mirror opposite. The concept of locality means that everything we interact with has a cause and effect that involves a force transmitted through physical space according to the known laws of nature.
In other words, when locality is at work, any cause you can think of must be physically connected to whatever it affects, be that by physical particle or electromagnetic wave.
For example, if you roll a bowling ball and it hits some pins we can clearly trace the causal chain of events: You used your muscles and your hand to propel a ball that rolled along the floor until it hit the pins. If your bowling alley was one mile long and sloped slightly downhill it would take your ball a few minutes to roll all the way there. But so long as you rolled the ball straight enough to avoid the gutters, it would eventually knock over the pins.
In such a situation your bowling ball cannot physically cause the pins to fall over until the ball arrives and touches the pins. The force that knocks over the pins takes the form of the momentum that is carried by the ball from you to the pins. There needs to be physical contact between the ball and the pins to transfer that force. (We calculate the force using your old friend, the formula of force = mass x acceleration.)
Bowling, Bowler, Pins, Ball, Alley, Sport, Fun
So, how could we possibly explain what happened if you rolled the ball and then half a second later the pins fell over — several minutes before the rolling ball arrived? What if the pins fell down while the ball was still rolling? The answer would surely have to be that some other force acted locally on the pins, such as a gust of wind or vibrations in the floor.
Perhaps the pins were precariously balanced and it was the hard bang of the ball hitting the floor that caused a vibration wave to propagate through the wood and knock the pins over. Whatever explanation we come up with must include some type of force or particle traveling through space. All of this is another way of saying that everything we have ever observed in our lives has obeyed the principle of locality.
If we shift to using beams of light in a thought experiment, the same principle applies. If we shine an unimaginably powerful laser from Earth onto the surface of the Moon it would take 2.54 seconds for the laser light to reach the Moon, and bounce back into our eyeballs. We are causing a spot on the moon to illuminate via the mechanism of light physically traveling from here to there.
But, how could we possibly explain what happened if a red dot appears on the moon less than a half a second after we shined our laser, instead of more than two seconds? By definition light cannot travel faster than the speed of light.
Illustration of Moon Showing during Sunset
The answer is that we would hunt for alternative explanations.
A possibility could be that someone is playing a trick on us by shining their own powerful laser at the same spot right before we turn on ours. But there would be ways to test whether that is happening. For example, we could turn our laser on at random intervals, which would be hard for a trickster to anticipate. Or we could modulate our laser to send short pulses of light that could be translated into the dots and dashes of Morse Code.
But what if our message seemed to reflect back from the Moon’s surface faster than allowed by the speed of light?
At that point we should probably not assume that we had somehow violated the speed of light which is a known constant, scientifically validated over and over and over. The speed of light is the well known C in the famous equation E=MC2 that makes possible our understanding of nuclear power and weapons and the structure of space-time itself.
As we searched for explanations we might suspect that a trickster guessed the Morse Code message we would send, and he would send it first. Perhaps he hacked our computer so that as soon as we put in our message, the computer would transmit our message to him first which would allow him to transmit two seconds before we did.
If any of these explanations were true they would be called locality-based explanations because they all expose how the trickster found a way to send his message first.
At some point, however, if we eliminated every possible explanation we would need to start considering seemingly impossible explanations. Maybe our trickster built a tiny satellite that looked exactly like the Moon, and was in orbit only 1,200 miles above the Earth as opposed to 240,000 miles away? That could partially explain things.
But even if we can’t figure out how it is happening, we continue to be confident that there has to be some reasonable explanation. Because there is just no way that we could be violating the speed of light.
Right?
This image has an empty alt attribute; its file name is road-4088226_1280.jpg
Well. This is where we get to the idea of nonlocality.
Scientists have discovered that if we take a pair of tiny particles, such as photons, and we entangle them by shining them through a certain type of crystal, those two particles can develop a connection that transcends space and time in ways that allows the particules to communicate instantaneously no matter how far apart they are.
When I say instantaneously, I mean instantaneously in ways that are clearly in conflict with the speed of light, and are unexplainable by classical physics. For the first time, we seemed to have evidence of truly nonlocal behavior in which cause and effect were not connected by a known force traveling through known space.
When this concept first came to light, Albert Einstein could not accept that quantum physics could involve nonlocality. Einstein derisively called this phenomenon “spooky action at a distance” and set out to prove that there must be some yet-undiscovered local explanation for a seemingly nonlocal phenomenon.
Albert Einstein, Portrait, Theoretician Physician
For example, if you and I are criminal collaborators who get get separated, we could agree in advance to stick to a certain story such that if we were concurrently interrogated by different detectives we would give the same answers.
in 1935, Einstein and two of his peers (Podolsky and Rosen) published a thought experiment titled “Can Quantum-Mechanical Description of Physical Reality be Considered Complete?” In this famous paper they argued that the claim by quantum physicists of nonlocality being a real thing . . . . must be incomplete. Einstein and his pals used numerous fancy words but their point was unmistakably simple: We may not know what is missing, but you people are definitely missing something important. Your nonlocality theory is bananas.
For decades, physicists and philosophers argued about what the quantum physicists could possibly be missing. Nobody could think of anything. Many physicists felt in their gut that Einstein was right, even as experimental evidence mounted that he was wrong.
After all, nothing travels faster than light, and it takes at least three minutes for light to travel from Earth to Mars. So, it can’t possibly be true that if you do push a button on Earth it could cause anything to happen instantaneously on Mars. Because there is no known physical mechanism known that would allow for the transmission of that signal.
In 1964, John Stewart Bell wrote a famous paper that addressed these issues with more rigor than anyone before. He set out to investigate whether there was any way to solve the nonlocality problem by finding hidden variables such as particles somehow “agreeing” in advance to show certain behaviors under questioning by scientist detectives in laboratories distant from each other.
Bell showed that it was possible to create situations in which no possible “hidden variables” could resolve the paradox. The explanation is technical but Bell’s logic was airtight: Nonlocality is somehow real, even if it makes us uncomfortable and we do not understand how it works.
Cube, Escher, Gradient, Mc Escher, Optical Illusion
Over the following decades physicists and philosophers have continued to ask themselves what the hell is going on and how can we possibly understand it? They have performed thousands of experiments with increasingly powerful and sophisticated equipment. They have discussed and debated and hypothesized. And still they are not sure what the hell is going on, though they are getting closer.
In Quantum Non-Locality and Relativity: Metaphysical Intimations of Modern Physics, author Tim Maudlin takes us through an investigation that is unbelievably rigorous. He takes us through an incredibly careful re-telling of history, re-explaining relativity, the structure of space-time, Euclidian space, invariant quantities, Newtonian Space-time, Galilean Space-time, special relativity, and the fascinating concept of Lorentz Transformations that explain how objects physically change shape as they approach the speed of light.
Maudlin then spends chapter after chapter exploring in great detail every possible mechanism that could explain away nonlocality. Superliminal matter transport? Tachyons? Secret messages? Lorentz Invariant Collapse Theories? Preferred sets of hyperplanes? Non-Minkowski Space-time? Check, check, check, check, check, check, and no, no, no, no, no no.
Interestingly, Maudlin is not a physicist, but rather a philosopher. His book is exceedingly difficult and there is plenty of math. But you needn’t actually understand vector spaces, eigenvalues, and orthnormal bases in order to follow most of his reasoning.
Quantum Non-Locality and Relativity: Metaphysical ...
Across his chapters Maudlin presents one theory after another and discusses the strengths and weaknesses of each theory. One thing that he makes clear, however, is that you cannot have your cake and eat it too. He explores both determinate theories and stochastic theories that each appear to have something going for them — and also appear to have fatal flaws. He leaves it up to you to decide which fundamental truths you will cling to, while making it clear that at least one thing you believe is almost certainly completely wrong. He just does not know which one.
Reading this book made me realize that at least one of several mind-blowing possibilities is highly like to be true:
First, some microscopic particles may be able to move briefly backwards in time via “closed timelike curves” that allow them to interfere with themselves. If this is true it could beautifully explain the mysterious wave-particle duality experiments in which particles appear to interfere with themselves to create interference patterns.
Second, spacetime could be far more complex than it appears. There may be additional physical dimensions that we have yet to discover, and it may be possible that particles that seem physically distant from each other are in fact “touching” via a dimension that we cannot yet see or understand.
Third, the “many-worlds interpretation” may be correct. I hate this idea so much that I will not even describe it.
Fourth, we could be living in a simulation, and the concept of nonlocality could be programmed into our operating system.
Fifth, the “flashy GRW” theory described near the end of the book could be correct. Unfortunately I do not understand it well enough to summarize it here.
Wave, Particles, Physics, Abstract
As Maudlin says at the end of his book:
We are in a methodological quandary. It is hard to imagine a neutral methodological principle that could militate in favor of retaining a pre-existing theory of space-time at all costs, while allowing for the abandonment of an equally entrenched pre-existing theory of space-time at all costs, while allowing for the abandonment of an equally entrenched pre-existing account of the local distribution of matter at the scale which we think is probed by microscopes. The microscopic distribution of matter is not open to our direct inspection, but neither is the structure of space-time at any scale. And if you accept a many-worlds picture, then even the local macroscopic distribution of matter is not open to immediate inspection: most of the matter in any given region is invisible to us. So all of our options — adding a foliation, flashy GRW, many-worlds interpretation that denies unique outcomes — one way or another postulates a physical world that shields itself from our view. Each one asserts that the natural conclusions of what seem to be straightforward scientific investigations somehow go radically awry. One way or another, the world is not at all what it appears to be.
Overall, this book is as difficult as it is interesting. The concepts it discusses are fascinatingly thought-provoking. I expect to read it several more times and still not understand parts. Until then I will hope that Maudlin eventually writes a fourth edition that includes new chapters to describe what our theoretical and experimental physicists are learning right now.
Until then, I will not rest easy, because I am burning with desire to understand how it can be that a particle on Mars can communicate instantly with a particle on Earth.
Bart Epstein, June 2020
SHARE THIS:
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Published by bart315
View all posts by bart315
June 14, 2020
Quantum Mechanics
Post navigation
Might China Allow (or Order) Women To Have Multiple Husbands?
Book Club Blog Post: Simply Einstein, Relativity Demystified
3 thoughts on “What is Quantum Non-Locality?”ADD YOURS
Eilon Poem
June 17, 2020 at 1:48
July 10, 2022
it’s all very confusing
A fairly detailed look at the implications of Bell’s Inequality and how it brings sharply into focus the already uneasy relationship between relativity and quantum theory. Lorentz invariance, non locality, measurement, entanglement … you could go crazy trying to figure out all this stuff. Contra Einstein nature is not just subtle but mischievous as the author points out. Or perhaps just outright malicious. Nothing is at all as it seems, there are untold hidden depths. Maybe forever beyond the ken of our vainglorious little monkey brains … and maybe not. Anyway this great book will contribute some understanding and leave your brain buzzing. What else could you possibly ask for.
A fairly detailed look at the implications of Bell’s Inequality and how it brings sharply into focus the already uneasy relationship between relativity and quantum theory. Lorentz invariance, non locality, measurement, entanglement … you could go crazy trying to figure out all this stuff. Contra Einstein nature is not just subtle but mischievous as the author points out. Or perhaps just outright malicious. Nothing is at all as it seems, there are untold hidden depths. Maybe forever beyond the ken of our vainglorious little monkey brains … and maybe not. Anyway this great book will contribute some understanding and leave your brain buzzing. What else could you possibly ask for.
May 8, 2021
A very interesting read for those interested in the peculiar results of quantum mechanics.
The book is at some times quite hard to follow, and it is not always easy to separate the key arguments from the occasional obscure dives into very specific concepts.
I would recommend looking up in more detail the diverse interpretations of quantum mechanics (wikipedia is great for that), as it helped me a lot following some of the arguments.
The book is at some times quite hard to follow, and it is not always easy to separate the key arguments from the occasional obscure dives into very specific concepts.
I would recommend looking up in more detail the diverse interpretations of quantum mechanics (wikipedia is great for that), as it helped me a lot following some of the arguments.
August 6, 2008
can be difficult at times.
January 21, 2009
maudlin can be a little demanding, but this is a great overview of the problems in marrying quantum mechanics with relativity theory.
Displaying 1 - 10 of 10 reviews