Is my understanding of the answers given correct?

  • #1
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Summary:
From all the answers I have received it seems that there is nothing amazing about QM. there is no need for many worlds etc.
I posted a question on Ask A physicist and he replied, "If the uncertainty principle is correctly stated, it is a correct physical principle which indicates the degree to how well you can possibly know something.
So its just that we cannot know simultaneously what a particle's position and momentum is. It is not that they lack a position and momentum. That seems very mundane. It doesn't tell us anything about matter it tells us only that we will always be uninformed about either the position or the momentum. There is no need for such extravagant explanations as "That is, as it [the particle] moves from its starting point A to some endpoint B, it doesn’t take one definite path, but rather simultaneously takes every possible path connecting the two points."
Hawking the grand design
Since my question was, is the uncertainty intrinsic ( that the particle has no position and/or momentum ) or is the uncertainty merely a measure of what we can know and the answer was ( see bold font ) it seems that there is nothing remarkable here. Why do physicists keep saying that QM violates common sense etc?
 

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  • #2
Demystifier
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Nobody knows which of the two interpretations is right. If the second one (that uncertainty is just our inability to know things which are objectively there) is true, then one naturally asks why exactly we cannot know them. And when you try to make an elaborated answer, it turns out that each possible answer violates common sense one way or another.
 
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Summary:: From all the answers I have received it seems that there is nothing amazing about QM. there is no need for many worlds etc.

I posted a question on Ask A physicist and he replied, "If the uncertainty principle is correctly stated, it is a correct physical principle which indicates the degree to how well you can possibly know something.
So its just that we cannot know simultaneously what a particle's position and momentum is. It is not that they lack a position and momentum. That seems very mundane. It doesn't tell us anything about matter it tells us only that we will always be uninformed about either the position or the momentum. There is no need for such extravagant explanations as "That is, as it [the particle] moves from its starting point A to some endpoint B, it doesn’t take one definite path, but rather simultaneously takes every possible path connecting the two points."
Hawking the grand design
Since my question was, is the uncertainty intrinsic ( that the particle has no position and/or momentum ) or is the uncertainty merely a measure of what we can know and the answer was ( see bold font ) it seems that there is nothing remarkable here. Why do physicists keep saying that QM violates common sense etc?
It's impossible to work out from that when you are quoting some anonymous physicist, when you are quoting Hawking and when you are making your own claims about QM.

This thread is another example of the dangers of this sub-forum where the impression is given that quantum particles, ultimately, have well-defined trajectories. And, that classical physics is thereby restored, if only peppered with an ounce or two of experimental uncertainty.

Well-defined (realist) trajectories may be restored in Bohmian Mechanics, but only at the price of other distinctly non-classical assumptions.

In most QM interpretations, particles do not have well-defined trajectories - and, indeed, that is seen by many physicists as a cornerstone of quantum theory. And not just some experimental quirk.
 
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  • #4
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It's impossible to work out from that when you are quoting some anonymous physicist, when you are quoting Hawking and when you are making your own claims about QM.

This thread is another example of the dangers of this sub-forum where the impression is given that quantum particles, ultimately, have well-defined trajectories. And, that classical physics is thereby restored, if only peppered with an ounce or two of experimental uncertainty.

Well-defined (realist) trajectories may be restored in Bohmian Mechanics, but only at the price of other distinctly non-classical assumptions.

In most QM interpretations, particles do not have well-defined trajectories - and, indeed, that is seen by many physicists as a cornerstone of quantum theory. And not just some experimental quirk.
Some anonymous physicist ? Stephen Hawking is not well known? I also gave the source, his book , " The Grand Design."
 
  • #5
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Some anonymous physicist ? Stephen Hawking is not well known? I also gave the source, his book , " The Grand Design."
You've constructed the dubious proposition that Hawking either did not believe in QM or believed in some realist interpretation (such as Bohmian mechanics). That proposition is false. You have taken a quotation from Hawking's popular science book out of context.

In any case, this is yet another thread where the fundamentally non-classical nature of QM is called into question, under the pretext of discussing "interpretations".
 
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  • #6
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Nobody knows which of the two interpretations is right. If the second one (that uncertainty is just our inability to know things which are objectively there) is true, then one naturally asks why exactly we cannot know them. And when you try to make an elaborated answer, it turns out that each possible answer violates common sense one way or another.
Suppose there is a dark room that I cannot see into. I send basketballs into it. They ricochet out of the room. I will not be able to tell both the position and momentum of the objects that they ricocheted off of. That seems analogous to me of firing particles in the 2 slit experiment. There is nothing mysterious going on. I do not have to propose multiple universes etc.
 
  • #7
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You've constructed the dubious proposition that Hawking either did not believe in QM or believed in some realist interpretation (such as Bohmian mechanics). That proposition is false. You have taken a quotation from Hawking's popular science book out of context.

In any case, this is yet another thread where the fundamentally non-classical nature of QM is called into question, under the pretext of discussing "interpretations".
I am confused. So Hawking was not claiming that the particle is in all places?
 
  • #8
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I am confused. So Hawking was not claiming that the particle is in all places?
Yes, I am questioning QM. Is it bad to try to understand it? My basic question is, is QM actually almost classical except that our influence on the results of an experiment are unavoidable.
 
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  • #9
martinbn
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The question is labled 'A', which means grad school level. The question itself seems to be based on popular expositions of physics. It should be 'B'.
 
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  • #10
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Summary:: From all the answers I have received it seems that there is nothing amazing about QM. there is no need for many worlds etc.

I posted a question on Ask A physicist and he replied, "If the uncertainty principle is correctly stated, it is a correct physical principle which indicates the degree to how well you can possibly know something.
So its just that we cannot know simultaneously what a particle's position and momentum is. It is not that they lack a position and momentum. That seems very mundane. It doesn't tell us anything about matter it tells us only that we will always be uninformed about either the position or the momentum. There is no need for such extravagant explanations as "That is, as it [the particle] moves from its starting point A to some endpoint B, it doesn’t take one definite path, but rather simultaneously takes every possible path connecting the two points."
Hawking the grand design
Since my question was, is the uncertainty intrinsic ( that the particle has no position and/or momentum ) or is the uncertainty merely a measure of what we can know and the answer was ( see bold font ) it seems that there is nothing remarkable here. Why do physicists keep saying that QM violates common sense etc?
I posed my question without clarity previously. I will try to be clearer;

Yes, I am questioning QM. Is it bad to try to understand it? My basic question is, is QM actually almost classical except that our influence on the results of an experiment is unavoidable.

Suppose there is a dark room that I cannot see into. I send basketballs into it. They ricochet out of the room. I will not be able to tell both the position and momentum of the objects that they ricocheted off of. That seems analogous to me firing particles in the 2-slit experiment. There is nothing mysterious going on. I do not have to propose multiple universes etc. Why is any extraordinary explanation needed?

I apologize for not making my question clear.
 
  • #11
PeroK
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Yes, I am questioning QM. Is it bad to try to understand it? My basic question is, is QM actually almost classical except that our influence on the results of an experiment are unavoidable.
Which is totally and utterly wrong.

I am confused. So Hawking was not claiming that the particle is in all places?
It's a popular science source. That's why such sources are not acceptable here.
 
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  • #12
martinbn
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I posed my question without clarity previously. I will try to be clearer;

Yes, I am questioning QM. Is it bad to try to understand it? My basic question is, is QM actually almost classical except that our influence on the results of an experiment is unavoidable.
What do you mean by questioning QM? If you believe that it s wrong, you are in the wrong place. You need to go to crackpotforums.com.
 
  • #13
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Which is totally and utterly wrong.


It's a popular science source. That's why such sources are not acceptable here.
So we should ignore Hawking's books? Was he lying?
 
  • #14
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What do you mean by questioning QM? If you believe that it s wrong, you are in the wrong place. You need to go to crackpotforums.com.
So no questions about QM allowed! WOW! All I asked was why such extraordinary explanations are needed.
 
  • #15
martinbn
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So we should ignore Hawking's books? Was he lying?
You, yourself, should ignore them, they are obviously confusing you. No, Hawking is not lying, he is oversimplifying.
 
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  • #16
martinbn
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So no questions about QM allowed! WOW! All I asked was why such extraordinary explanations are needed.
If you label the question as 'A' level, you should be familiar with graduat leve QM. Are you?
 
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  • #17
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Which is totally and utterly wrong.


It's a popular science source. That's why such sources are not acceptable here.
I posed my question without clarity previously. I will try to be clearer;

Yes, I am questioning QM. Is it bad to try to understand it? My basic question is, is QM actually almost classical except that our influence on the results of an experiment is unavoidable.

Suppose there is a dark room that I cannot see into. I send basketballs into it. They ricochet out of the room. I will not be able to tell both the position and momentum of the objects that they ricocheted off of. That seems analogous to me firing particles in the 2-slit experiment. There is nothing mysterious going on. I do not have to propose multiple universes etc. Why is any extraordinary explanation needed?

I apologize for not making my question clear.
 
  • #18
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5
I posed my question without clarity previously. I will try to be clearer;

Yes, I am questioning QM. Is it bad to try to understand it? My basic question is, is QM actually almost classical except that our influence on the results of an experiment is unavoidable.

Suppose there is a dark room that I cannot see into. I send basketballs into it. They ricochet out of the room. I will not be able to tell both the position and momentum of the objects that they ricocheted off of. That seems analogous to me firing particles in the 2-slit experiment. There is nothing mysterious going on. I do not have to propose multiple universes etc. Why is any extraordinary explanation needed?

I apologize for not making my question clear.
Note that I am not saying that QM is classical and that the uncertainty principle is only because it is unavoidable to influence the experiment. I am asking a question.
 
  • #19
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Note that I am not saying that QM is classical and that the uncertainty principle is only because it is unavoidable to influence the experiment. I am asking a question.
Of course some will say that I am ignorant and have no right to ask such questions. I disagree.
 
  • #20
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So no questions about QM allowed!

I think you should check what "questioning" means. And it does not mean "asking questions".
 
  • #21
PeroK
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So no questions about QM allowed! WOW! All I asked was why such extraordinary explanations are needed.
We've had this argument before - so many times on this forum. QM was not invented out of the blue. It was developed to explain extraordinary experimental results that could not be explained classically.

This is what it means for physics to be an empirical science. It's not philosophy. It's not just something that you make up out of pure thought. It has to match experiment. The experimental results are non-classical and so any theory that successfully explains them must be non-classical. If you want to replace "non-classical" with "extraordinary", then go ahead.

QM is all based on experimental evidence (over 100 years of it now).
 
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  • #22
PeroK
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My basic question is, is QM actually almost classical except that our influence on the results of an experiment is unavoidable.
No, this is wrong. Any undergraduate textbook will tell you that.
 
  • #23
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I think you should check what "questioning" means. And it does not mean "asking questions".
??? I am asking questions. BTW if I have faith in QM or not has nothing to do with the validity of my questions. Where did I say that QM was wrong? I am sure that there is an explanation as to why physicists say that QM needs extraordinary explanations. I just want to hear them. BTW please lets not make this discussion personal. All I want is an answer to my question. There is no reason to be so defensive.
 
  • #24
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Where did I say that QM was wrong?

Again - check in the dictionary what does "questioning" mean. Then you'll know why people interpreted you posts that way.
 
  • #25
PeroK
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Of course some will say that I am ignorant and have no right to ask such questions. I disagree.
QM is not politics. It is not democratic. If you refuse to learn QM even at undergraduate level, then you have no equal rights to be taken seriously. It's the same as any scientific discipline: medicine, engineering, cell biology etc. The first step is to learn the subject.
 

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