Why Is Quantum Mechanics So Difficult to Understand?

[y.moghadamnia]

I don't really get the part that we shouldn't "imagine" quantum mechanics .I mean, I know what eigenvectors are in three dim for a known operator and I know what's the meaning of uncertainty that u can't know the place of any particle unless u look, and when u look, means u have to hit it by photons so u change its place and so on. why can we never understand quantum mechanics as feynman says, and why do I always have a funnt feeling when I am studying quantum mec, a feeling I never get in special relativity or Newtonian mechanics?
l

 

[ConradDJ]

I don't really get the part that we shouldn't "imagine" quantum mechanics... why can we never understand quantum mechanics as feynman says...?

The reason students are told this is so they’ll focus on the physics and not get caught up in misconceptions. And the reason for the inevitable misconceptions about QM is that we’re still operating within a conceptual framework that assumes physical systems are whatever they are, independent of the interactions through which information about them gets communicated to the rest of the world.

There’s tons of evidence that at the quantum level, the “state” of a system is not determinate except in a context where it’s “measured” – and even then, only the specific aspects of its state that are measured get “determined”, and only to the extent of the accuracy of the measurement.

I’m sure that we’ll be able to imagine and understand QM, once we figure out what these simple facts mean. But so long as our basic way of imagining the world is as a collection of things that have definite characteristics “in themselves”, we can’t. We’re stuck with describing the world in a classical language, fixed up with paradoxical fudges like “superposition” that are bound to cause misunderstanding.

 

[Galap]

Ahh: the old 'shut up and calculate'...

Well, what I have to say is that while the point that was trying to be made was that eventually our current understanding reaches an end. There is a place where our theories are no longer adequate explanations to the things we find. You go deeper and deeper, surrendering intentionally a bit of your understanding each step of the way, until you get to a mad place beyond which you cannot go. Where nothing has explanation or meaning.

But we should never stop 'imagining' things. Someday we will push the frontier further. With QM maybe it will be a clever experiment, or maybe just ingenious 'imagining' that will eventually make QM "make sense" and allow us to pass to the next level.

That being said, some of the current interpretations (or 'imaginings') are quite clever and do make it seem a lot more sensible.

 

[the_house]

I don't really get the part that we shouldn't "imagine" quantum mechanics .
l

I personally wouldn't say you should never "imagine" quantum mechanics at all, just that you shouldn't imagine a quantum system as if it were a classical system that you are used to (e.g., electrons as little balls that travel in particular orbits around the nucleus).

If you try to do this it will give you absolutely no insight into the physics and you will come to many wrong conclusions that are contradicted by experiment.

You definitely can develop intuition about quantum mechanics, but you have to actually develop this intuition from studying quantum mechanics. You can't just substitute your intuition from everyday experience or from Newtonian physics.

I believe that's what people usually mean when they tell you not to hold a particular picture in your head, or to "imagine" it.

 

[y.moghadamnia]

to "the house" ;
I guess that's exactly what I was looking for, not to imagine "the wrong thing", not not to imagine at all.
but how are we going to find the right image?

 

[the_house]

to "the house" ;
I guess that's exactly what I was looking for, not to imagine "the wrong thing", not not to imagine at all.
but how are we going to find the right image?

That's the trick, isn't it? I don't know of any easy shortcuts, so I don't think I can help you there. It just takes time and effort to study the theory (and the observations that support it). Also, it requires the ability to progressively let go of previously built-up intuition as your understanding of the quantum world gets better.