Question about Quantum mechanics

[schrodingasdawg]

Copenhagen, at least in its most literal sense, requires some unknown dynamics that collapses the wavefunction upon a measurement and projects it onto one "world".

This is assuming that the wave-function is a physically real, objective thing. There certainly is some ambiguity in what "Copenhagen" entails but the form I've usually encountered it in (and what I'm advocating here) is that the wave-function is not real, but instead a subjective, completely theoretical construct. In Copenhagen (or at least this flavor of it) the physics is understood in terms of what can in principle be known and observed, and only these things are 'real.' Hence it should be no surprise that the wave-function will 'collapse' when the system is measured---and measurement should of course be understood in this interpretation as any determination of the properties (observables) of the object by the subject (observer)---and this is a consequence of the subjective basis of any physical knowledge rather than physical dynamics that exist in their own right.

This interpretation, of course, relies on an idealist metaphysics, so I'd imagine a realist would be uncomfortable with it. And I can't blame them---collapse as an objective, physical process is extremely troublesome for all the reasons you stated. And for that reason I actually advocated MWI for a while (it is certainly the most parsimonious realist interpretation); it took giving up realism for idealism to change my mind.

Except that the wavefunction is observable - it is reality, so it is all observables.

This was as a counter to the argument that the wave-function is not reality because it is not observable. Whether the wave-function is reality is what is up for dispute; you can't use it as a premise.

 

[randman]

That will not work.
Space-time does not have anything to do with the MW interpretation of QM.

Yes, it does but not sure if I want to explain that here other than to say, obviously, MWI advocates alternative space (other universes).

My point is that the apparent violation of so-called physical laws is based on our idea of what is physical.

 

[sol invictus]

This is assuming that the wave-function is a physically real, objective thing.

No, it isn't.

Look - suppose I want to be able to make predictions for what results a series of experiments will produce. Then I certainly need to know how the wavefunction evolves through a measurement, because I need to know what it is after the first measurement but before the second. That's true irrespective of what sort of "reality" you assign to it - it's true simply because in any interpretation of QM, it's the wavefunction that allows you to make any predictions at all.

Therefore part of Copenhagen (or a more complete version of it) has to be some theory about how the wavefunction reacts to measurements. The simplest version, the one you'll find in at least some textbooks, is that it is projected onto the eigenstate corresponding to the result of the measurement. That process is not only not unitary, it's not even linear - it cannot be described by quantum mechanics, or by any known theory of physics.

My point is that the apparent violation of so-called physical laws is based on our idea of what is physical.

What "violation of physical laws" are you talking about?

 

[Reality Check]

Yes, it does but not sure if I want to explain that here other than to say, obviously, MWI advocates alternative space (other universes).

No MW does not. The MW universe are not different "spaces", they are different universes. All of quantum mecahnics happens in Euclidean spacetimes. All of the MW universes are Euclidean spacetimes.

My point is that the apparent violation of so-called physical laws is based on our idea of what is physical.

The scientific point is that there is no violation of physical laws.
The physical laws are those that match what the universe is observed to do. On small scales they are the laws of quantum mechanics.

Our idea of what is physical is wrong when we try to project those ideas onto quantum scales. The universe acts differently than we expect, just like it acts differently than we expect for large velocities.
This is why we use our brains rather than just eyes to do science.

 

[randman]

No, it isn't.

Look - suppose I want to be able to make predictions for what results a series of experiments will produce. Then I certainly need to know how the wavefunction evolves through a measurement, because I need to know what it is after the first measurement but before the second. That's true irrespective of what sort of "reality" you assign to it - it's true simply because in any interpretation of QM, it's the wavefunction that allows you to make any predictions at all.

Therefore part of Copenhagen (or a more complete version of it) has to be some theory about how the wavefunction reacts to measurements. The simplest version, the one you'll find in at least some textbooks, is that it is projected onto the eigenstate corresponding to the result of the measurement. That process is not only not unitary, it's not even linear - it cannot be described by quantum mechanics, or by any known theory of physics.



What "violation of physical laws" are you talking about?

The same ones you mentioned.

 

[randman]

No MW does not. The MW universe are not different "spaces", they are different universes. All of quantum mecahnics happens in Euclidean spacetimes. All of the MW universes are Euclidean spacetimes.


The scientific point is that there is no violation of physical laws.
The physical laws are those that match what the universe is observed to do. On small scales they are the laws of quantum mechanics.

Our idea of what is physical is wrong when we try to project those ideas onto quantum scales. The universe acts differently than we expect, just like it acts differently than we expect for large velocities.
This is why we use our brains rather than just eyes to do science.

Or what we perceive as physical laws such as objective reality and locality are probabilities applicable within a certain range.

An example of what I am talking of can be seen in entanglement. 2 entangled particles will act as one system regardless of distance and so really regardless of time. You can posit a gazillion different universes where some happen to be so identical that there is interference between the particles or the particles cause a splitting of the multiverse into new universes (all unobserved), or hidden variables, or waves that travel backwards in time, and maybe other things like consciousness interacting with the universe.

Or, we could just look at what we observe on it's face. One particle's position being measured causes the other particle to be in a corresponding state. Einstein thought of it as spooky action at a distance, but that's because the idea of spatial separation; hence action at a distance.

Perhaps though they are not separated informationally in their fundamental state, just spatially separated.

A simpler though somewhat revolutionary concept is the particles are informationally connected outside space and time (regardless of spatial distance), and so are fundamentally immaterial and so then is the universe itself. What we think of as physical is a derived or secondary state. The first and fundamental state is simply a packet or unit of information with probabilities to manifest in discrete form in space and time depending on the information that can be obtained from it.

The particle isn't really in any discrete form necessarily until it's in a state that could confer specific information.

If we move away from thinking of space as fundamental and position in space and time as a requirement for existence, the observed behavior is not so strange.

 

[randman]

Maybe instead of postulating a gazillion alternate universes, the correct path to solving these issues is to rethink our concepts of space and time?

btw for Sol and reality, my comment is that instead of postulating MWI, maybe the correct path is to revise our concepts of space and time and what constitutes the universe.

 

[JoelKatz]

When they say "we are observing it", they mean that it has any detectable effects. They don't mean specifically that conscious humans beings are doing the observing. That something doesn't exist when it has no detectable effects is really just another way of saying that a thing is its detectable effects. The surprising thing is that this has testable consequences. (One would naively think it wouldn't make any difference whether or not something existed the same way when it wasn't observed as when it was, but it turns out it does.)

The best way to put it is that there is no more information in the universe than is needed. One tends to imagine that there's tons of extra -- kind of like when you're playing a video game, you might imagine that the computerized opponents have hearts and lungs. But they don't need them when you're not looking inside them.

 

[Reality Check]

btw for Sol and reality, my comment is that instead of postulating MWI, maybe the correct path is to revise our concepts of space and time and what constitutes the universe.

That is still wrong.
The MWI has a specific definition of space and time (Euclidean space & time).
The MWI has the same definition of universe as other theories (I got it wrong in my previous posts - there is just one). It just contains many "worlds" that are superimosed. In each world the history of the state that constitutes it is different. An any instant we are in one of those worlds.

 

[randman]

That is still wrong.
The MWI has a specific definition of space and time (Euclidean space & time).
The MWI has the same definition of universe as other theories (I got it wrong in my previous posts - there is just one). It just contains many "worlds" that are superimosed. In each world the history of the state that constitutes it is different. An any instant we are in one of those worlds.

MWI may. So what? Read what I initially wrote and you responded to.

INSTEAD of postulating a gazillion alternate universes, maybe we should rather revise our concept of the universe (space and time).

 

[Reality Check]

MWI may. So what? Read what I initially wrote and you responded to.

INSTEAD of postulating a gazillion alternate universes, maybe we should rather revise our concept of the universe (space and time).

Still wrong:

MWI is the only interpretation that postulates " a gazillion alternate universes". So if you are tying to replace that postulate then you are refereeing to MWI.
​

All current quantum theories have a specific definition of space and time (Euclidean space & time).
All current quantum theoriesthe same definition of universe that is usualyy used..

 

[randman]

Still wrong:

MWI is the only interpretation that postulates " a gazillion alternate universes". So if you are tying to replace that postulate then you are refereeing to MWI.
​

All current quantum theories have a specific definition of space and time (Euclidean space & time).
All current quantum theoriesthe same definition of universe that is usualyy used..

Did you read what I wrote?

If you don't want to postulate a gazillion universes, that's another way to say if you do not want to postulate MWI. So no MWI is not refeering as you say.

 

[randman]

When they say "we are observing it", they mean that it has any detectable effects. They don't mean specifically that conscious humans beings are doing the observing. That something doesn't exist when it has no detectable effects is really just another way of saying that a thing is its detectable effects. The surprising thing is that this has testable consequences. (One would naively think it wouldn't make any difference whether or not something existed the same way when it wasn't observed as when it was, but it turns out it does.)

The best way to put it is that there is no more information in the universe than is needed. One tends to imagine that there's tons of extra -- kind of like when you're playing a video game, you might imagine that the computerized opponents have hearts and lungs. But they don't need them when you're not looking inside them.

great post

 

[punshhh]

Or what we perceive as physical laws such as objective reality and locality are probabilities applicable within a certain range.

An example of what I am talking of can be seen in entanglement. 2 entangled particles will act as one system regardless of distance and so really regardless of time. You can posit a gazillion different universes where some happen to be so identical that there is interference between the particles or the particles cause a splitting of the multiverse into new universes (all unobserved), or hidden variables, or waves that travel backwards in time, and maybe other things like consciousness interacting with the universe.

Or, we could just look at what we observe on it's face. One particle's position being measured causes the other particle to be in a corresponding state. Einstein thought of it as spooky action at a distance, but that's because the idea of spatial separation; hence action at a distance.

Perhaps though they are not separated informationally in their fundamental state, just spatially separated.

A simpler though somewhat revolutionary concept is the particles are informationally connected outside space and time (regardless of spatial distance), and so are fundamentally immaterial and so then is the universe itself. What we think of as physical is a derived or secondary state. The first and fundamental state is simply a packet or unit of information with probabilities to manifest in discrete form in space and time depending on the information that can be obtained from it.

The particle isn't really in any discrete form necessarily until it's in a state that could confer specific information.

If we move away from thinking of space as fundamental and position in space and time as a requirement for existence, the observed behavior is not so strange.

Yes this makes perfect sense to me, space and time being a necessary framework through which particles manifest, when in a form conceivable to us, as we operate only in this framework.

These particles may be the tip of an iceberg of potential information or behavior which we can only observe above water. Water representing other than space time and above water representing space time as we know it.

 

[randman]

Yes this makes perfect sense to me, space and time being a necessary framework through which particles manifest, when in a form conceivable to us, as we operate only in this framework.

These particles may be the tip of an iceberg of potential information or behavior which we can only observe above water. Water representing other than space time and above water representing space time as we know it.

Thanks. I appreciate that image and perspective on above or below "water."

 

[Reality Check]

Did you read what I wrote?

If you don't want to postulate a gazillion universes, that's another way to say if you do not want to postulate MWI. So no MWI is not refeering as you say.

I did and restated it so that you could agree or disagree with it. You seem to, i.e. no "gazillion universes" = No MWI


That still leaves the problem that:

• Quantum mechanics has a specific definition of space and time (Euclidean space & time).
• Quantum mechanics has the same definition of universe that is usually used.

If we do whatever you mean by "revise our concepts of space and time" we still have to have Euclidean space & time (and a univserse) for quantum mechanics to work.

A more basic problem is that the "issues" you refer to the basically the collapse of the wavefunction. That is nothing to do with space, time or even the universe. You cannot "fix" it by doing whatever you mean with that vague revising term.

 

[randman]

no "gazillion universes" = No MWI

Correct.

If we do whatever you mean by "revise our concepts of space and time" we still have to have Euclidean space & time (and a univserse) for quantum mechanics to work.

No we do not except we can keep the Euclidean part.

 

[punshhh]

Thanks. I appreciate that image and perspective on above or below "water."

I visualise it as a vertical wall or curtain of water, you look at it and see yourself reflected. You can touch it and feel the ripples.

Beyond the surface (meniscus) there is infinite potential, anything could emerge at any time.

 

[sol invictus]

The same ones you mentioned.

You're not making sense. The problems I mention arise only in the Copenhagen interpretation, but your post referred to the MWI.

 

[randman]

You're not making sense. The problems I mention arise only in the Copenhagen interpretation, but your post referred to the MWI.

No, my original post was about another approach besides MWI. Reality Check was confused and asked about MWI and so I responded to him, but didn't mean to drag you in to thinking I was talking about MWI.

You know I don't agree with MWI and have tried to get a better handle on it. I was saying instead of postulating so many different universes, maybe we should revise our concepts of space and time.