Theories of Quantum Physics, do they exist?

  • #1
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Every time I watch another YouTube video about the "spooky" stuff or multiple slit experiments they never have a proposed explanation of how they work. It would seem to me that if you had a proposed idea then people could think of experiments to prove or disprove the idea. But with no ideas it limits progress. Where are the ideas?
 

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  • #2
Orodruin
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What you need is a good textbook on what quantum physics actually is, not YouTube videos.
 
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  • #3
Lord Jestocost
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.....or multiple slit experiments they never have a proposed explanation of how they work.
Regarding explanations how it works, that's what Richard Feynman has to say:

"Because atomic behavior is so unlike ordinary experience, it is very difficult to get used to, and it appears peculiar and mysterious to everyone—both to the novice and to the experienced physicist. Even the experts do not understand it the way they would like to, and it is perfectly reasonable that they should not, because all of direct, human experience and of human intuition applies to large objects. We know how large objects will act, but things on a small scale just do not act that way. So we have to learn about them in a sort of abstract or imaginative fashion and not by connection with our direct experience.

In this chapter we shall tackle immediately the basic element of the mysterious behavior in its most strange form. We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery. We cannot make the mystery go away by “explaining” how it works. We will just tell you how it works. In telling you how it works we will have told you about the basic peculiarities of all quantum mechanics."

(The Feynman Lectures on Physics, Volume III, the italics are in the original)
 
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  • #4
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It would not take a textbook to propose how "spooky action" works. I am looking for the ideas people have so I can think about what they say and propose my own ideas. Those multiple slit experiments or those with the polarizing filters, they bemone the fact they can not explain but always fail to propose any ideas what is happening.
 
  • #5
Nugatory
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Every time I watch another YouTube video about the "spooky" stuff or multiple slit experiments they never have a proposed explanation of how they work. It would seem to me that if you had a proposed idea then people could think of experiments to prove or disprove the idea. But with no ideas it limits progress. Where are the ideas?
You've just made an excellent case for not trying to learn QM from YouTube videos. With a few exceptions (the Feynman lectures are the only one that I can think of offhand) they generally range from hopelessly awful and just plain wrong to merely inadequate, incomplete, and misleading.

But to answer the question in the title of this thread: Quantum mechanics IS a theory, with as many experiments demonstrating the correctness of its predictions as any other theory in physics - it's probably tied with classical mechanics and electrodynamics for first place. Every time you power up an electronic device you're running another experiment demonstrating the correctness of QM.

What QM does not have is a natural intuitive picture of "how they work" underneath. But that's true of all physical theories if you think about it. Consider Newton's law of gravitation, ##F=Gm_1m_2/r^2##. Like QM, it is supported by massive amounts of experimental and observational data. But it says nothing about why objects are attracted to one another (why isn't the force ever repulsive? Why should there be a force at all?) and nothing about why the force works the way it does (why is it ##r^2## instead of for example ##r^3##? Why the product of the masses instead of the sum?). What we have is a demonstrably correct mathematical theory about the behavior of macroscopic objects but no explanation of what's behind that theory - and that's exactly the situation with regard to microscopic objects and QM. The difference is that QM is offensive to our intuition and classical gravitation is not - "Dropped objects fall" doesn't bother us as much as "single-particle interference patterns form". But that's a problem with our intuition, not the theories.
 
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  • #6
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It would not take a textbook to propose how "spooky action" works. I am looking for the ideas people have so I can think about what they say and propose my own ideas.
You cannot understand serious ideas people have, let alone propose one, without reading a textbook first.
 
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  • #7
You've just made an excellent case for not trying to learn QM from YouTube videos. With a few exceptions (the Feynman lectures are the only one that I can think of offhand) they generally range from hopelessly awful and just plain wrong to merely inadequate, incomplete, and misleading.

But to answer the question in the title of this thread: Quantum mechanics IS a theory, with as many experiments demonstrating the correctness of its predictions as any other theory in physics - it's probably tied with classical mechanics and electrodynamics for first place. Every time you power up an electronic device you're running another experiment demonstrating the correctness of QM.

What QM does not have is a natural intuitive picture of "how they work" underneath. But that's true of all physical theories if you think about it. Consider Newton's law of gravitation, ##F=Gm_1m_2/r^2##. Like QM, it is supported by massive amounts of experimental and observational data. But it says nothing about why objects are attracted to one another (why isn't the force ever repulsive? Why should there be a force at all?) and nothing about why the force works the way it does (why is it ##r^2## instead of for example ##r^3##? Why the product of the masses instead of the sum?). What we have is a demonstrably correct mathematical theory about the behavior of macroscopic objects but no explanation of what's behind that theory - and that's exactly the situation with regard to microscopic objects and QM.
To be fair, Stanford and Yale have entire lectures on QM on YouTube.
 
  • #8
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To be fair, Stanford and Yale have entire lectures on QM on YouTube.
Links? We need more good resources.... And maybe I'll be able to think of them offhand next time :)
 
  • #9
It would not take a textbook to propose how "spooky action" works. I am looking for the ideas people have so I can think about what they say and propose my own ideas. Those multiple slit experiments or those with the polarizing filters, they bemone the fact they can not explain but always fail to propose any ideas what is happening.
QM is a theory which very accurately describes a multitude of phenomena. The actual interpretation of the theory and it’s implications are still to this day not really understood( no real consensus). That being said, you need to get a quality textbook on QM before trying to formulate your own opinions on certain aspects of the theory which are counter intuitive.
 
  • #10
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Regarding explanations how it works, that's what Richard Feynman has to say:

"Because atomic behavior is so unlike ordinary experience, it is very difficult to get used to, and it appears peculiar and mysterious to everyone—both to the novice and to the experienced physicist. Even the experts do not understand it the way they would like to, and it is perfectly reasonable that they should not, because all of direct, human experience and of human intuition applies to large objects. We know how large objects will act, but things on a small scale just do not act that way. So we have to learn about them in a sort of abstract or imaginative fashion and not by connection with our direct experience.

In this chapter we shall tackle immediately the basic element of the mysterious behavior in its most strange form. We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery. We cannot make the mystery go away by “explaining” how it works. We will just tell you how it works. In telling you how it works we will have told you about the basic peculiarities of all quantum mechanics."

(The Feynman Lectures on Physics, Volume III, the italics are in the original)
Watching this now:

 
  • #11
atyy
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Regarding explanations how it works, that's what Richard Feynman has to say:

"Because atomic behavior is so unlike ordinary experience, it is very difficult to get used to, and it appears peculiar and mysterious to everyone—both to the novice and to the experienced physicist. Even the experts do not understand it the way they would like to, and it is perfectly reasonable that they should not, because all of direct, human experience and of human intuition applies to large objects. We know how large objects will act, but things on a small scale just do not act that way. So we have to learn about them in a sort of abstract or imaginative fashion and not by connection with our direct experience.

In this chapter we shall tackle immediately the basic element of the mysterious behavior in its most strange form. We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery. We cannot make the mystery go away by “explaining” how it works. We will just tell you how it works. In telling you how it works we will have told you about the basic peculiarities of all quantum mechanics."

(The Feynman Lectures on Physics, Volume III, the italics are in the original)
I love the Feynman lectures, but this is actually one part which may not be correct. See the very interesting discussion about this passage in the Feynman lectures that opens https://arxiv.org/abs/1301.3274v1.
 
  • #12
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It would not take a textbook to propose how "spooky action" works
[Public service announcement: Everyone is expected to be mindful of the Physics Forums rules about personal theories]

That's right, it does not. However, it does take an accurate understanding of what the theory actually is, and you won't get that from YouTube videos.
.
 
  • #13
PeterDonis
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I am looking for the ideas people have so I can think about what they say and propose my own ideas.
Textbooks and peer-reviewed papers are what tell you about the ideas other people have that have been made into quantitative models that make predictions which are borne out by experimental results.

The qualifier is crucial. It's not enough to have an idea. You have to make your idea precise enough and rigorous enough that it can be put into a model that makes quantitative predictions, and then you have to test those predictions by experiment, and your model has to pass the tests. If you think you are going to learn how to do all that by watching YouTube videos, you are seriously mistaken.
 
  • #14
PeterDonis
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Where are the ideas?
The title of this thread doesn't say "ideas". It says "theories" and asks whether they exist. The answer to that question is simple: yes. If you read the textbooks and peer-reviewed papers that describe those theories, you will learn what they say, and how they have been confirmed to many decimal places by experiments, which is why physicists believe them.
 
  • #15
atyy
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Every time I watch another YouTube video about the "spooky" stuff or multiple slit experiments they never have a proposed explanation of how they work. It would seem to me that if you had a proposed idea then people could think of experiments to prove or disprove the idea. But with no ideas it limits progress. Where are the ideas?
There are ideas such as Bohmian Mechanics, eg. http://scienceblogs.com/principles/2011/06/03/watching-photons-interfere-obs/.

While Bohmian Mechanics can explain some quantum phenomena, it is not clear whether it can explain all quantum phenomena. Bell's theorem guarantees (subject to some assumptions) that any explanation that exists must be nonlocal.
 
  • #16
Links? We need more good resources.... And maybe I'll be able to think of them offhand next time :)


[emoji106]
 
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  • #17
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Watching this now:

Well, I watched, very interesting. But he did not try to make a guess of the why, perhaps involving the fabric of space and some topsy-turvy time travel thing. All he said was we can't explain it. That is a cop-out. If people give an idea of the why then other people can test for that "why". I am also disappointed that we have not made some tool that uses the dbl slit to accomplish something or at least a toy in the Burger King toys that demonstrates it. xD
 
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  • #18
Orodruin
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That is a cop-out.
No it is not. If you think so then you have a misconception about science. The point of science is to figure out how, not a deeper "why". A scientific theory is successful if it is self-consistent and manages to correctly make experimental predictions that are verified. The "weird behaviour" is exactly the behaviour predicted by quantum mechanics. You consider it "weird" just because it goes against your intuition, which we know (from experiments!) does not apply at the quantum level. The "why" you seem to be looking for goes no deeper than "quantum mechanics predicts this".

With that being said, we can of course continue to ponder about if there is some deeper theory that is applicable in some regime where quantum mechanics is not, but for the double slit experiment itself it really goes no deeper than "QM works like this" and any additional stuff is just philosophical musings.
 
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  • #19
atyy
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Well, I watched, very interesting. But he did not try to make a guess of the why, perhaps involving the fabric of space and some topsy-turvy time travel thing. All he said was we can't explain it. That is a cop-out. If people give an idea of the why then other people can test for that "why".
Feynman's lecture is in error in his discussion around 47 - 53 minutes in which he says that the double slit is not due to a lack of detailed knowledge.

I am also disappointed that we have not made some tool that uses the dbl slit to accomplish something or at least a toy in the Burger King toys that demonstrates it. xD
Quantum theory that gives that quantitative predictions for the double slit experiment also explains the electrical properties of conductors, insulators and semiconductors, which are part of the devices you used to type your posts. For a Burger King toy (well, it was a serious invention, but it is not used because there are better technologies also based on quantum mechanics) using a famous quantum effect called "tunneling", you can try https://en.wikipedia.org/wiki/Tunnel_diode.

People are also working on quantum computers which if realized will be able to break the widely-used RSA encryption. However, I think this is way beyond our technical capabilities for the moment and the foreseeable future. Smaller quantum computers are likely to come about in the next 5-10 years which can do things classical computers cannot do in reasonable amounts of time, but these tasks will likely be too specialized to be widely useful.
 
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  • #20
PeterDonis
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The OP question has been addressed. Thread closed.
 

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