Einstein thoughts on the quantum

[Varon]

To those very familiar with Einstein. Why couldn't he agree with Bohr. Was it because Einstein rejected indeterminism or was it because QM rejected realism?

But I have problem believing in the latter. Einstein 4-dimensional spacetime is just pure mathematic. 4-D objects are stationary.. and observers move along worldline at the speed of light. We couldn't imagine this as actual physical objects but just mathematical construction and modelling. Now. Quantum mechanics with the objects not having positions even in principle unless measured with random outcome. Why did Einstein have trouble with this when his Spacetime is even stranger and out of reality? Was it because Einstein simply didn't want the random and indeterminism of the quantum or was he also criticizing that the quantum rejected reality as in the electron having no position before measurement? If the latter is true. How come Einstein had trouble with it when his Spacetime was equally (or even more) as anti-realistic?

 

[Matterwave]

Einstein didn't have a problem with "realism", in fact, he wanted local realism in his theories. He could not accept that a certain object simply had no definite state before an observation was made. To him, the object HAD a definite state, but it was merely the theory which was incomplete (and could not give us the state).

 

[Varon]

Einstein didn't have a problem with "realism", in fact, he wanted local realism in his theories. He could not accept that a certain object simply had no definite state before an observation was made. To him, the object HAD a definite state, but it was merely the theory which was incomplete (and could not give us the state).

Why? Doesn't this argument that object has no definite state before observation not against "realism"? In other words. An object having no definite state before observation is definitely anti-realism. What's the critical argument why it is not? I think define realism first so we won't have semantics mismatch.

 

[Matterwave]

Yes...the statement "an object was not in a definite state before observation" IS against definite realism. Einstein was AGAINST people who took this viewpoint, making him a realist.

 

[Varon]

Yes...the statement "an object was not in a definite state before observation" IS against definite realism. Einstein was AGAINST people who took this viewpoint, making him a realist.

Now this is what is puzzling. But Einstein Spacetime where it can morph, curves, bend, elongate, etc. is not a realism. How come he could accept his Spacetime as not a realist thing while having trouble with the anti-realism of quantum mechanics? In fact, he should embrace QM because it only shows realism is dead.

 

[Matterwave]

Einstein's theory is deterministic. It describes exactly what's happening with or without observers present. In fact, Einstein required that all physical objects be "generally covariant" with respect to coordinate changes, which means that the physics is independent of the frame of reference or the coordinate system used. I don't see it as being non-realistic. Perhaps if you could elaborate your point.

 

[Varon]

Einstein's theory is deterministic. It describes exactly what's happening with or without observers present. In fact, Einstein required that all physical objects be "generally covariant" with respect to coordinate changes, which means that the physics is independent of the frame of reference or the coordinate system used. I don't see it as being non-realistic. Perhaps if you could elaborate your point.

I think pure QM also obey some symmetry. Why should Einstein's be the standard where Spacetime can morph, curve, bend, elongate, etc. General Covariant produces Spacetime physics. Some symmetry produces Quantum Mechanics. Why should Einstein be biased in Spacetime obeying realism while QM does not? Both are weird. So I wonder if the indeterminism is what bothered Einstein more than realism (which both Spacetime and Quantum Mechanics seem to violate... realism being the Newtonian experience we have on daily life).

 

[Matterwave]

Oh, you're using a different definition of "realism" than the one I'm used to. Ok, if we define "realism" to "normal every day experience" then sure both theories are weird. SR definitely gives rise to paradoxical results as viewed from a "common sense" view point. Why Einstein could accept his "brand" of "weirdness" but could not accept quantum mechanical weirdness should not be surprising. We all hold our prejudices on what "makes sense" and what "doesn't". Einstein just simply did not like the idea that objects don't have a definite state before they are measured, or that the universe was inherently probabilistic in nature. Einstein believed in a totally deterministic set of physical laws.

Another example of when Einstein was unwilling to change his viewpoint was his inclusion of the cosmological constant in his field equations to permit a static universe. Einstein thought that the universe was infinite and static, but his equations seemed to suggest otherwise. He put in an arbitrary cosmological constant in his equations to allow the equations to have a solution for a static universe. He later called this his biggest mistake because later Hubble discovered that the universe was, in fact, dynamic and was not static at all.

So, I don't think there's anything surprising in the idea that Einstein accepted the weirdness in his theories, but did not accept quantum weirdness.

 

[Varon]

Oh, you're using a different definition of "realism" than the one I'm used to. Ok, if we define "realism" to "normal every day experience" then sure both theories are weird. SR definitely gives rise to paradoxical results as viewed from a "common sense" view point. Why Einstein could accept his "brand" of "weirdness" but could not accept quantum mechanical weirdness should not be surprising. We all hold our prejudices on what "makes sense" and what "doesn't". Einstein just simply did not like the idea that objects don't have a definite state before they are measured, or that the universe was inherently probabilistic in nature. Einstein believed in a totally deterministic set of physical laws.

Another example of when Einstein was unwilling to change his viewpoint was his inclusion of the cosmological constant in his field equations to permit a static universe. Einstein thought that the universe was infinite and static, but his equations seemed to suggest otherwise. He put in an arbitrary cosmological constant in his equations to allow the equations to have a solution for a static universe. He later called this his biggest mistake because later Hubble discovered that the universe was, in fact, dynamic and was not static at all.

So, I don't think there's anything surprising in the idea that Einstein accepted the weirdness in his theories, but did not accept quantum weirdness.

Why what's your and physicists definition of "realism"? Whaterver. I think we mustn't say Einstein is a realist. Because his Spacetime is not exactly realist. Instead we should just imagine Einstein didn't like Indeterminism. Also believe Einstein is a localist.. but not anti-realist (because his Spacetime is not exactly realist in the everyday idea of object and daily experience).

 

[Matterwave]

Realist is usually just the viewpoint that objects have a definite state and exist - "are real" - even if you don't observe them. This is the usual viewpoint of "realism". Einstein Podolsky and Rosen made an argument for this view point, you can look up the EPR paradox on wikipedia.

 

[Varon]

Realist is usually just the viewpoint that objects have a definite state and exist - "are real" - even if you don't observe them. This is the usual viewpoint of "realism". Einstein Podolsky and Rosen made an argument for this view point, you can look up the EPR paradox on wikipedia.

Thanks for this. I thought realis or realism is everyday experience so I didn't focus on the definition when I studied EPR a week ago. So there is difference between man on the street realism and physics realism. No wonder man on the street has difficulty understanding Special Relativity.

Anyway. I bought this all up because something bugs me. We know Spacetime is mathematics and we dont' really know how it decompose into Space and Time of man on the street who doesn't move or float along geodesics. Einstein 4-dimensional spacetime is just pure mathematic. 4-D objects are stationary.. and observers move along worldline at the speed of light. We couldn't imagine this as actual physical objects but just mathematical construction and modelling. And we don't know how it correspond to our everyday experienced Space and Time, we just accept it and let philosophers deal with the problem of how to connect the two, agree?

Ok. Now Quantum mechanics. What if it is like Spacetime physics. Meaning QM is just a tool to calculate probabilities just like Spacetime is a tool to calculate gravity (that is, in GR). Implication of this is all Interpretations of Quantum Mechanics may be false. QM is just a mathematical tool to calculate probabilities and there is no ontology inside it just like there is no ontology in Spacetime. Do you think this is possible?

 

[Matterwave]

Quantum Mechanics is, in fact, a mathematical tool for calculating probabilities. In fact, the rules of Quantum Mechanics are quite interesting in that they are very much man-made (made by committee!). It is kind of like a miracle that it works at all!

Special and General Relativity though is more of a physical theory in the sense that they were derived from certain guiding axioms or principles which are experimentally verified (Constancy of the speed of light, general coordinate invariance, and the equivalence principle). It is true that people on the street don't follow geodesics, but that is simply because there are other forces involved (normal force of the ground, for example). However, people DO move through space-time in a certain trajectory (it just happens not to be a geodesic), we merely don't notice this because our perception is localized to one slice in time (the present). We can only experience the present, and as such we experience a 3-D slice of the 4-D space-time. In this way, I would argue that it is not so much that SR and GR are mere mathematical tools, but that we are limited by our perception.

Of course, every physical theory can be viewed as simply a mathematical description of reality. Even Newton's laws, for example, can be viewed as mere definitions of what a "force" means. With that particular mathematical description, we can obtain the equations of motion. But certainly that is not the ONLY mathematical description of classical mechanics. You can check out, for example, Lagrangian mechanics, which does not invoke any notion of "force", and directly obtain the equations of motion from a variational principle.

Whether any of these principles "exist" (the actual ontology of these mathematical models), is a problem for philosophy, and not really for physics.

 

[Varon]

Quantum Mechanics is, in fact, a mathematical tool for calculating probabilities. In fact, the rules of Quantum Mechanics are quite interesting in that they are very much man-made (made by committee!). It is kind of like a miracle that it works at all!

Special and General Relativity though is more of a physical theory in the sense that they were derived from certain guiding axioms or principles which are experimentally verified (Constancy of the speed of light, general coordinate invariance, and the equivalence principle). It is true that people on the street don't follow geodesics, but that is simply because there are other forces involved (normal force of the ground, for example). However, people DO move through space-time in a certain trajectory (it just happens not to be a geodesic), we merely don't notice this because our perception is localized to one slice in time (the present). We can only experience the present, and as such we experience a 3-D slice of the 4-D space-time. In this way, I would argue that it is not so much that SR and GR are mere mathematical tools, but that we are limited by our perception.

Are you saying 4D Spacetime is literal and we just can't view perceive it? What do you think of the following comment. It refutes your hypothesis:

(got this from Bobc2 from an old thread here in this forum)

"Example:

We have a wonderful model of a 4-dimensional universe populated by 4-dimensional objects. At face value special relativity would seem to imply that those 4-D objects are just that--objects frozen in time so to speak--motionless. Yet, we always speak of observers moving along their world lines at the speed of light. If the objects, including 4-D spaghetti-like bundles of neurons extending millions of miles along the 4th dimension, are not actually moving as 4-D objects, then what is doing the moving? And what is the physical significance of the imaginary i that is often attached to the 4th dimension? And where are all of the observers really located at a particular instant of time (they don't share the same simultaneous 3-D cross-sections of the 4-D universe)? Is there some universal synchronized time for all consciousnesses? Or does a consciousness and "NOW" experience exist at all points along the 4-D world lines for every observer?

It's questions such as these that cause physicists (probably most of them) to consider those 4-D objects as mathematical constructs and not real physical 4-D objects."

Of course, every physical theory can be viewed as simply a mathematical description of reality. Even Newton's laws, for example, can be viewed as mere definitions of what a "force" means. With that particular mathematical description, we can obtain the equations of motion. But certainly that is not the ONLY mathematical description of classical mechanics. You can check out, for example, Lagrangian mechanics, which does not invoke any notion of "force", and directly obtain the equations of motion from a variational principle.

Whether any of these principles "exist" (the actual ontology of these mathematical models), is a problem for philosophy, and not really for physics.

 

[ajw1]

Are you saying 4D Spacetime is literal and we just can't view perceive it?

In all circumstances where the maths predicts testable effects of spacetime curvature it has been confirmed so far. From the precession effects on Mecury, corrections necessary in daily used GPRS systems, existence of black holes etc. (http://en.wikipedia.org/wiki/Tests_of_general_relativity).
Recently the gravity probe B also confirmed spacetime curvature and even frame dragging by direct measurement. So how can you argue spacetime is out of reality? All the evidence suggests we really do live in a curved spacetime.

 

[Fredrik]

...his Spacetime was equally (or even more) as anti-realistic?

Not even close. SR and GR can both be thought of as approximate descriptions of what actually happens to a physical system. If you try to think of QM that way, your head will explode. (Not intended to be a factual statement. )

Einstein didn't reject QM. He only rejected the idea that a wavefunction describes all the properties of a single physical system.

That stuff about "moving along the world line at the speed of light" isn't weird at all. The motion of a particle is represented by a curve in spacetime, in SR, GR and pre-relativistic physics. In the latter case, we're talking about Galilean spacetime. So that part of the story hasn't introduced anything weird that wasn't already present in pre-relativistic physics. In SR and GR, the four-velocity is defined as the normalized tangent vector to the world line. "Normalized" means that we choose it to have a "magnitude" corresponding to the speed of light. So the "everything moves through spacetime at the speed of light" silliness is just an immediate consequence of a definition with no physical content. It's not a profound insight about what reality is really like.

 

[Varon]

Not even close. SR and GR can both be thought of as approximate descriptions of what actually happens to a physical system. If you try to think of QM that way, your head will explode. (Not intended to be a factual statement. )

What is your comment about this comment by bob2c that those 4-D objects are just mathematical constructs. How does it tie into what you just said above? Bob2c said
in an old thread here:

"Example:

We have a wonderful model of a 4-dimensional universe populated by 4-dimensional objects. At face value special relativity would seem to imply that those 4-D objects are just that--objects frozen in time so to speak--motionless. Yet, we always speak of observers moving along their world lines at the speed of light. If the objects, including 4-D spaghetti-like bundles of neurons extending millions of miles along the 4th dimension, are not actually moving as 4-D objects, then what is doing the moving? And what is the physical significance of the imaginary i that is often attached to the 4th dimension? And where are all of the observers really located at a particular instant of time (they don't share the same simultaneous 3-D cross-sections of the 4-D universe)? Is there some universal synchronized time for all consciousnesses? Or does a consciousness and "NOW" experience exist at all points along the 4-D world lines for every observer?

It's questions such as these that cause physicists (probably most of them) to consider those 4-D objects as mathematical constructs and not real physical 4-D objects."

Einstein didn't reject QM. He only rejected the idea that a wavefunction describes all the properties of a single physical system.

That stuff about "moving along the world line at the speed of light" isn't weird at all. The motion of a particle is represented by a curve in spacetime, in SR, GR and pre-relativistic physics. In the latter case, we're talking about Galilean spacetime. So that part of the story hasn't introduced anything weird that wasn't already present in pre-relativistic physics. In SR and GR, the four-velocity is defined as the normalized tangent vector to the world line. "Normalized" means that we choose it to have a "magnitude" corresponding to the speed of light. So the "everything moves through spacetime at the speed of light" nonsense is just an immediate consequence of a definition with no physical content. It's not a profound insight about what reality is really like.

 

[Fredrik]

What is your comment about this comment by bob2c that those 4-D objects are just mathematical constructs. How does it tie into what you just said above?

There are only two kinds of answers to questions about reality: Answers given by theories, and bull**** answers. Every single technical term in an answer given by a theory is defined by that theory. This includes e.g. "energy", "particle" and "spacetime". These definitions are always mathematical. So you could say that every single one of those things are "just mathematical constructs".

Most of them do however correspond in a more or less obvious way to something in the real world. The obvious exception to that is "wavefunction". (There are interpretations in which it does correspond to something real, but there's no good reason to think that they are more correct than the minimal statistical interpretation). I would say that spacetime does correspond to something in the real world, since every member of it corresponds to a place in space and time that can (in principle) unambiguously be assigned spatial and temporal coordinates by actual measuring devices.

 

[Matterwave]

Are you saying 4D Spacetime is literal and we just can't view perceive it? What do you think of the following comment. It refutes your hypothesis:

(got this from Bobc2 from an old thread here in this forum)

"Example:

We have a wonderful model of a 4-dimensional universe populated by 4-dimensional objects. At face value special relativity would seem to imply that those 4-D objects are just that--objects frozen in time so to speak--motionless. Yet, we always speak of observers moving along their world lines at the speed of light. If the objects, including 4-D spaghetti-like bundles of neurons extending millions of miles along the 4th dimension, are not actually moving as 4-D objects, then what is doing the moving? And what is the physical significance of the imaginary i that is often attached to the 4th dimension? And where are all of the observers really located at a particular instant of time (they don't share the same simultaneous 3-D cross-sections of the 4-D universe)? Is there some universal synchronized time for all consciousnesses? Or does a consciousness and "NOW" experience exist at all points along the 4-D world lines for every observer?

It's questions such as these that cause physicists (probably most of them) to consider those 4-D objects as mathematical constructs and not real physical 4-D objects."

One can immediately see the limits of human perception when we see discussions on "the speed that we move along our world line", and "objects are frozen in time - space-time". Speed is really a distance/time. I think it's overly confusing to try to talk about "our speed through space-time". As Fredrik said, the fact that the magnitude of the 4-velocity is "c" is just due to the way we choose to parameterize our world lines so as to give them normalization. If one thinks of "c" as no more than some conversion factor between space and time, then it is natural to use units where c=1, and from that we can easily see that choosing u*u=1 (or -1 depending on the signature of the metric) is merely a normalization constraint.

You can see immediately where contradiction occurs in bob's post wherin we are both "moving along our worldlines at c" and "frozen in time-motionless".

Space-time is a 4-D world, and as I said, we are always limited to a 3-D slice of it in our perception of "now". We cannot think of things being "static" without an appeal to some notion of constancy in time. If we include time itself in our formulation, then these notions of "static" that we had are no longer tenable. Our very notion of existence is intimately tied to "now" or some instant in time. It is very hard for us to think outside of that paradigm.

 

[San K]

To those very familiar with Einstein. Why couldn't he agree with Bohr. Was it because Einstein rejected indeterminism or was it because QM rejected realism?

But I have problem believing in the latter. Einstein 4-dimensional spacetime is just pure mathematic. 4-D objects are stationary.. and observers move along worldline at the speed of light. We couldn't imagine this as actual physical objects but just mathematical construction and modelling. Now. Quantum mechanics with the objects not having positions even in principle unless measured with random outcome. Why did Einstein have trouble with this when his Spacetime is even stranger and out of reality? Was it because Einstein simply didn't want the random and indeterminism of the quantum or was he also criticizing that the quantum rejected reality as in the electron having no position before measurement? If the latter is true. How come Einstein had trouble with it when his Spacetime was equally (or even more) as anti-realistic?

The answer might be in human psychology.

Perhaps doing two huge "leaps of faith", back to back, is psychologically not easy.

Two major "discoveries/observations" in fundamental physics happened at same time.

Einstein was able to do solve one with a set of very unconventional assumptions and reasoning for that era.

Once Einstein was successful he might have clung to his theory (time-space-relativity) as being really basic/fundamental. Which it might be however there might be more to it, something even beyond/different/separate from his theories?

It might have been hard for him to accept/realize there was something (additional) even more unconventional and different than he had solved. Something that even his profound theories of time-space-relativity could not provide even a clue. Perhaps Einstein kept solving within his time-space “boundaries/mind-set".

 

[Varon]

There are only two kinds of answers to questions about reality: Answers given by theories, and bull**** answers. Every single technical term in an answer given by a theory is defined by that theory. This includes e.g. "energy", "particle" and "spacetime". These definitions are always mathematical. So you could say that every single one of those things are "just mathematical constructs".

Most of them do however correspond in a more or less obvious way to something in the real world. The obvious exception to that is "wavefunction". (There are interpretations in which it does correspond to something real, but there's no good reason to think that they are more correct than the minimal statistical interpretation). I would say that spacetime does correspond to something in the real world, since every member of it corresponds to a place in space and time that can (in principle) unambiguously be assigned spatial and temporal coordinates by actual measuring devices.

So you admit that spacetime is a mathematical contructs. What I'm trying to understand in this thread is if spacetime is pure math with no obvious correspondence or one to one mapping to reality. Then it is possible quantum mechanics is just a tool to calculate probabilities. I'm trying to explore the Computer Simulation Interpretation of QM in this thread. Here spacetime and quantum mechanics are just programs. Of course it doesn't have to limit to computer like our Intel processors but even exotic matter computer akin to the holographic principle where everything that happens here can originate in a distant boundary somewhere. Now in this Computer Simulation Interpretation of QM and even Relativity. Does it have unique predictions versus the other Interpretations? I can think of one. Wave function is pure progamming codes. Only the outputs in the screen matters. The wave function is not actually in the screen. This means only measurements make sense. Before measurement, there is no output.. nothing on the screen... it's all inside the computer. Here Bohmian mechanics, Many worlds are made null and void because there is no ontology, its all a programming, and Copenhagen is just outward expression of it. The Computer Simulation Interpretation is then more like the causal mechanism of Copenhagen. Now do you have any arguments that make impossible this Computer Simulation Interpretation of Quantum Mechanics? (I think Paul Davies and Brian Greene have mentioned something similar to this in their books.. how come the mainstream doesn't seem to like this? what's the reason? Maybe there is a theorem of some kind that makes it impossible?)

 

[Varon]

Bottomline is. If GR and QM are just programming codes. Suppose you are a programmer creating a SimUniverse (akin to Sim City), does it makes sense to put wave function in the screen or output of the program or is it more internal.. meaning only measurements are outputted in the screen.. Any computer programmers here? Do you need to put wave function in the output as parts of the simulation or it is internal algorithm only inside the program and only measurements make sense? Pls. share insights.

 

[Fredrik]

I think your posts are getting too speculative. I want to discuss scientific theories, not fantasies. (This forum also has rules against overly speculative posts).

So you admit that spacetime is a mathematical contructs.

That comment makes me think you missed the point of what I was saying. Just about everything we talk about is a mathematical construct. That's not a bad thing. It's just how physics works. We make statements about the mathematical constructs first, and then we use the postulated correspondence between mathematics and the real world to translate them to statements about reality.

What I'm trying to understand in this thread is if spacetime is pure math with no obvious correspondence or one to one mapping to reality. Then it is possible quantum mechanics is just a tool to calculate probabilities.

The word "then" usually indicates that the statement after it follows logically from the statement before it.

 

[Varon]

I think your posts are getting too speculative. I want to discuss scientific theories, not fantasies. (This forum also has rules against overly speculative posts).


That comment makes me think you missed the point of what I was saying. Just about everything we talk about is a mathematical construct. That's not a bad thing. It's just how physics works. We make statements about the mathematical constructs first, and then we use the postulated correspondence between mathematics and the real world to translate them to statements about reality.


The word "then" usually indicates that the statement after it follows logically from the statement before it.

But Computer Simulation Interpretation is a valid Intepretation of QM (popularized by physicists like Paul Davies and Brian Greene). It is as valid as entertaining Many worlds or Bohmian Mechanics. We must not reject any possibilities. What if all existing Interpretations are wrong because our universe is just simulation. You may think this is overtly speculative because of the language I use. Instead of saying Computer Simulation Interpretation. I should have said Holographic Principle Boundary Processing Interpretation. Anyway. I'll be more careful of the words next time. Thanks for your thoughts.

 

[Matterwave]

I'm losing your thread of thought here. How does this connect at all with your original premise that SR and GR are somehow "constructed" theories like QM?

 

[Varon]

I'm losing your thread of thought here. How does this connect at all with your original premise that SR and GR are somehow "constructed" theories like QM?

I was entertaining the idea SR, GR, and QM are just programming codes or algorithm or whatever (our computer programmers want to call it). That was why I asked if SR and GR are purely mathematical. Because if so, QM is completely mathematical too. Everything is completely mathematical and we are just part of the output.

But thinking what Fredrik has just said. Yes, the world "simulation" is pretty bad and a turn off. Instead what seems to be happening is that the laws of physics should be point of view invariant. And the universe can do any means to make it that way. The word "simulation" makes it appears as if someone is programming it that way. So instead, let's just assume the universe is a self-made program that can do anything it wants so long as it obeys point of view invariant and certain symmetries. This means we are not in a simulation. We are in a real thing. In a way. The universe is a super computer and we are its outputs but there is no progammer. Here wave function may be real after all as part of the universe. Darn. I just wanted arguments to resist from Many Worlds Interpretation onslaught. But it seems Many Worlds with the Universal Wave function could really be part of the world. Maybe we (or I) have just to get used to Schizophenia at universe scale.

 

[eaglelake]

To those very familiar with Einstein. Why couldn't he agree with Bohr. Was it because Einstein rejected indeterminism or was it because QM rejected realism?

But I have problem believing in the latter. Einstein 4-dimensional spacetime is just pure mathematic. 4-D objects are stationary.. and observers move along worldline at the speed of light. We couldn't imagine this as actual physical objects but just mathematical construction and modelling. Now. Quantum mechanics with the objects not having positions even in principle unless measured with random outcome. Why did Einstein have trouble with this when his Spacetime is even stranger and out of reality? Was it because Einstein simply didn't want the random and indeterminism of the quantum or was he also criticizing that the quantum rejected reality as in the electron having no position before measurement? If the latter is true. How come Einstein had trouble with it when his Spacetime was equally (or even more) as anti-realistic?

A rather extensive answer to your questions is found in, "The Shaky Game-Einstein Realism and the Quantum Theory", by Arthur Fine.

 

[Varon]

A rather extensive answer to your questions is found in, "The Shaky Game-Einstein Realism and the Quantum Theory", by Arthur Fine.

Well. I have this book. But I couldn't comprehend it well when I read about it months ago because I thought Realism meant everyday Newtonian world. So I kept thinking when reading why Einstein wanted to hold to realism when I thought his Spacetime (TM) is not exactly realism. Now I know from this thread that realism means having properties even before measurement, so even the mind boggling world of spacetime physics is realism because it is deterministic and independent of observation so the book makes much sense now and become just a basic and elementary.

 

[Matterwave]

I am not aware of the advances in the Multi-world interpretation of QM, and so I have no reason to think that this interpretation is "taking over" in any sense. As far as I know, standard QM is still the Copenhagen interpretation (of course, with some modifications since it was established near 90 years ago). Do you have sources saying this or something?

 

[Varon]

I am not aware of the advances in the Multi-world interpretation of QM, and so I have no reason to think that this interpretation is "taking over" in any sense. As far as I know, standard QM is still the Copenhagen interpretation (of course, with some modifications since it was established near 90 years ago). Do you have sources saying this or something?

The common sense question is why collapse happens. It is artificial, not a priori, arbitrary, superficial, ad hoc, etc. Hence they just propose the wave never collapse, all the outcomes exist, etc. Anyway. I believe it one day a week, monday Copnehagen, tuesday Many worlds, wednesday Bohmians, thursday Objective Collapse, etc.

 

[Fredrik]

As far as I know, standard QM is still the Copenhagen interpretation (of course, with some modifications since it was established near 90 years ago).

QM is a set of rules that tells us how to calculate probabilities of possible results of experiments. It doesn't need an interpretation. The statements that tell us how to interpret the mathematics as predictions about results of experiments are part of the theory itself, not of the interpretation.

I would prefer to define the CI as just QM with no additional assumptions, but it seems that no one actually defines it that way. Everyone seems to have their own idea about what the CI is, but almost everyone who uses that term seems to think that it includes the assumption that a state vector describes all properties of a single system. So the closest thing to a standard definition of the CI would be to say that the CI is QM with that additional assumption on top.

However, that assumption is unnecessary and unjustified, and it's probably also inconsistent with the actual theory. (It introduces a "measurement problem", which now needs to be "solved").

So I wouldn't say that the CI is standard. At least not the CI that's defined as above.

Of course, we could argue that the additional assumption shouldn't be included in the definition of the CI. If we drop it, what we have left is just QM, which is often called "the statistical interpretation" or "the ensemble interpretation", but it's really just QM, without any additional assumptions.

 

[Matterwave]

I suppose so. Sometimes it's hard to keep the interpretations in check. Each interpretation has had so many different advocates that it's hard to get a nice list of what each interpretation is saying. I wouldn't worry too much about what to call the "standard" QM. Suffice it to say that the Many Worlds interpretation has not become "standard".

 

[Varon]

QM is a set of rules that tells us how to calculate probabilities of possible results of experiments. It doesn't need an interpretation. The statements that tell us how to interpret the mathematics as predictions about results of experiments are part of the theory itself, not of the interpretation.

I would prefer to define the CI as just QM with no additional assumptions, but it seems that no one actually defines it that way. Everyone seems to have their own idea about what the CI is, but almost everyone who uses that term seems to think that it includes the assumption that a state vector describes all properties of a single system. So the closest thing to a standard definition of the CI would be to say that the CI is QM with that additional assumption on top.

However, that assumption is unnecessary and unjustified, and it's probably also inconsistent with the actual theory. (It introduces a "measurement problem", which now needs to be "solved").

So I wouldn't say that the CI is standard. At least not the CI that's defined as above.

Of course, we could argue that the additional assumption shouldn't be included in the definition of the CI. If we drop it, what we have left is just QM, which is often called "the statistical interpretation" or "the ensemble interpretation", but it's really just QM, without any additional assumptions.

The reason your proposal to define CI as just QM with no additional assumptions won't work is because it was Bohr who created CI and there was immediately the Bohr Postulate:

"In the absense of measurement to determine its position, the particle has no position"

This statement alone is enough to open all pandora's box.. so there is no such thing as CI as just QM with no additional assumptions. Defend your proposal.

 

[Fredrik]

The reason your proposal to define CI as just QM with no additional assumptions won't work is because it was Bohr who created CI

I don't know exactly what he said, and I'm not interested enough to find out. I'm guessing that Bohr did assume that a wavefunction describes all the properties of a single system, because what else was the disagreement with Einstein about?

and there was immediately the Bohr Postulate:

"In the absense of measurement to determine its position, the particle has no position"

This statement alone is enough to open all pandora's box..

This is a consequence of QM, not a separate postulate. I wonder if Bohr just said things like this, and his critics just assumed that he was identifying the wavefunction with the particle, i.e. that he was assuming that it represents all the properties of a single particle. It wouldn't surprise me. I have seen critics of the CI make that kind of mistakes before.

so there is no such thing as CI as just QM with no additional assumptions. Defend your proposal.

There's obviously such a thing as QM with no additional assumptions. If it's appropriate to call that "the CI" depends on what exactly Bohr said, and as I already told you, I'm not interested enough to find out. What I do know is that not even Niels Bohr had the right to add an assumption to the theory that makes the whole thing inconsistent, and the additional assumption that everyone seems to think is an essential part of the CI is also what introduces the measurement problem. If this is an actual inconsistency (I can't prove rigorously that it is since there's no formal definition of what it means to identify the wavefunction with the particle), then it doesn't make sense to include it in the definition of the CI.

 

[Varon]

I don't know exactly what he said, and I'm not interested enough to find out. I'm guessing that Bohr did assume that a wavefunction describes all the properties of a single system, because what else was the disagreement with Einstein about?


This is a consequence of QM, not a separate postulate. I wonder if Bohr just said things like this, and his critics just assumed that he was identifying the wavefunction with the particle, i.e. that he was assuming that it represents all the properties of a single particle. It wouldn't surprise me. I have seen critics of the CI make that kind of mistakes before.


There's obviously such a thing as QM with no additional assumptions. If it's appropriate to call that "the CI" depends on what exactly Bohr said, and as I already told you, I'm not interested enough to find out. What I do know is that not even Niels Bohr had the right to add an assumption to the theory that makes the whole thing inconsistent, and the additional assumption that everyone seems to think is an essential part of the CI is also what introduces the measurement problem. If this is an actual inconsistency (I can't prove rigorously that it is since there's no formal definition of what it means to identify the wavefunction with the particle), then it doesn't make sense to include it in the definition of the CI.

Can you explain your position based on the history of the development of QM. Here are what transpired in brief (from memory):

1. Bohr conjectured electrons are positioned in certain orbitals.
2. Einstein conjectured that photons which were thought of as wave were also particles.
3. de Broglie conjectured matter were also waves.
4. Schrodinger created the wave equation and conjecture the wave represenedt the particle either as charge or mass density.
5. Lorentz criticized Schroedinger's by emphasing wave packet spreads and couldn't be particle.
6. Born proposed the amplitude square was the probability of the particle location
7. Einstein proposed the wave function was just for the ensemble but Dirac and Heisenberg complained how it could describe individual system like an electron in the hydrogen atom.
8. von Neumann created the formal Hilbert Space mathematical formulation.

All of this are latter referred to as the Copenhagen Interpretation.

From the above. It is automatic that the wave function or state vector represents the properties of a system.. and the amplitude square is the probability of the particle location.

Now I'm perplexed how you could say CI is just QM without the wave function assumption as this is part of the history of QM. What part of the development of QM do you think the situation got confused and what should have occurred so CI become pure QM without mentioning about the wave function? Pls. elaborate as what you said didn't make much sense.

 

[Fredrik]

1. Bohr conjectured electrons are positioned in certain orbitals.
2. Einstein conjectured that photons which were thought of as wave were also particles.
3. de Broglie conjectured matter were also waves.
4. Schrodinger created the wave equation and conjecture the wave represenedt the particle either as charge or mass density.
5. Lorentz criticized Schroedinger's by emphasing wave packet spreads and couldn't be particle.
6. Born proposed the amplitude square was the probability of the particle location
7. Einstein proposed the wave function was just for the ensemble but Dirac and Heisenberg complained how it could describe individual system like an electron in the hydrogen atom.
8. von Neumann created the formal Hilbert Space mathematical formulation.

All of this are latter referred to as the Copenhagen Interpretation.

From the above. It is automatic that the wave function or state vector represents the properties of a system..

I'm sure that's how people were thinking at the time of (3) and (4), but it's not implied by the theory we ended up with. I'm not sure if that was already clear at step (8), but it certainly is in many modern textbooks. See e.g. this definition of QM. It certainly leaves the door open for an ensemble interpretation.

Now I'm perplexed how you could say CI is just QM without the wave function assumption as this is part of the history of QM. What part of the development of QM do you think the situation got confused and what should have occurred so CI become pure QM without mentioning about the wave function? Pls. elaborate as what you said didn't make much sense.

I don't know how you can say that it didn't make sense, but I can also tell that you read me wrong. You're saying that I said that the CI is QM without the assumption that a wavefunction describes all the properties of a single system. I didn't say that. I've been saying that a) there's no standard definition of the CI, b) everyone seems to include that assumption as a part of their definition of the CI, and c) I would prefer not to, since that assumption is what introduces the measurement problem. If we do include it, the CI is (very likely) logically inconsistent, and I don't see the point of assigning a name to something that's logically inconsistent.

I have to get some sleep, so I won't be answering any more posts for at least 8 hours.