5 ms·

What I don't get is why people are more concerned with how Qauntum Mechanics works than they are with the way in which, for example, electro magenetic waves tra

by dools 4y ago

What I don't get is why people are more concerned with how Qauntum Mechanics works than they are with the way in which, for example, electro magenetic waves travel in a vacuum. Like we can "physically" understand how sound travels, and we can "visualise" that as a "mechanism" right? But we have no similar way of "physicalising" the way in which light travels, but no-one seems to have any trouble accepting that. Quantum states seem to be no different: they're just a way things work, that we don't have a good "macro physical" analogy for.

sampo 4y ago
Quantum mechanics has wave function collapse, which is both essential in applying the theory to explain any physical situation, and at the same time not described by the theory. Other than "and then it collapses". Classical theories don't have this problem.
- _0w8t 4y ago
  And then the whole notion of the collapse is not really compatible with relativity.
- astrange 4y ago
  It’s also difficult to understand how chaotic systems are explained by quantum mechanics, although they must be. And of course what gravity has to do with it.
- dools 4y ago
  The whole “wave function collapse” thing as far as I understand is simply the result of any measurement involving entanglement. When you measure something by any means you create an entanglement that cancels out the term in the equation that produces “wave like” behaviour.
krastanov 4y ago
For many people the statement "electromagnetic fields exist as a (fundamental) building block of Nature" is just as reasonable as "atoms exist as a (fundamental) building block of Nature". The word "fundamental" is not particularly important, I am keeping it for historical reasons. You are perfectly comfortable with the existence of atoms (given your comments about understanding sound waves), presumably because you know of experiments that have demonstrated their existence. We have experiments that have demonstrated the existence of EM waves. So the questions is, what in your personal aesthetic tastes is making atoms more palatable? The question of interpreting quantum mechanics is quite different. We do not have a popular mathematical framework that clearly explains why we perceive a classical world while being "inside" of a quantum wavefunction. There is plenty of vagueness and oversimplification in that last statement, but the difference is "we have an abstraction that explains mostly-perfectly EM waves and we do not care about whether people are comfortable with the abstraction" vs "we do not even have a mathematical abstraction explaining why we perceive a classical world inside of a quantum universe".
- dools 4y ago
  > what in your personal aesthetic tastes is making atoms more palatable? It’s pretty easy for me to imagine things bumping into each other because I see that happening all around me
  - consilient 4y ago
    Atoms aren't anything like that though. There are no little billiard balls, probability densities don't "bump", electrons don't actually orbit, and so on. Atoms just are what they are, and what they are does not admit a good "macrophysical analogy".
    - TedDoesntTalk 4y ago
      > There are no little billiard balls … electrons don't actually orbit Wait, what? What do they do then? My physical science education ended in high school.
      - consilient 4y ago
        The next useful falsehood on the ladder is that electrons in an atom exist as probability densities around the nucleus. Fire a photon here, and knock an electron off with this probability; fire it there, and get that probability instead. But before they interact with something, electrons aren't anywhere in particular. https://en.wikipedia.org/wiki/Atomic_orbital https://en.wikipedia.org/wiki/Atomic_orbital The real answer is that constituent parts of bound states like atoms don't really exist as separate things. An atom is a particular very complicated field configuration, and if you want anything deeper than that you're going to have to learn QFT.
        tux3 4y ago
        If constituent parts of bound states like atoms don't really exist as separate things, how come electrons in metals can move around readily? Is it that they're not really bound, or is it just that they 'attach' and 'detach' easily? When I think of chemistry, it seems like even if there's some sense in which the bound atom is one big writhing mass of fields, the whole atom doesn't interract in a uniform way with the outside, right? The electrons interract with the outside a lot, the nucleus is harder to get to? Is it wrong to say the layer of my onion exist as separate entities, when they seem to interract largely independently from the core of the onion, like they do in metals and chemistry? (I guess the answer is still "you're going to have to learn QFT" :) But the next falsehood down seems fun to ask about too!)

by dools 4y ago

sampo 4y ago

Quantum mechanics has wave function collapse, which is both essential in applying the theory to explain any physical situation, and at the same time not described by the theory. Other than "and then it collapses". Classical theories don't have this problem.

_0w8t 4y ago
And then the whole notion of the collapse is not really compatible with relativity.
astrange 4y ago
It’s also difficult to understand how chaotic systems are explained by quantum mechanics, although they must be. And of course what gravity has to do with it.
dools 4y ago
The whole “wave function collapse” thing as far as I understand is simply the result of any measurement involving entanglement. When you measure something by any means you create an entanglement that cancels out the term in the equation that produces “wave like” behaviour.

krastanov 4y ago

For many people the statement "electromagnetic fields exist as a (fundamental) building block of Nature" is just as reasonable as "atoms exist as a (fundamental) building block of Nature". The word "fundamental" is not particularly important, I am keeping it for historical reasons. You are perfectly comfortable with the existence of atoms (given your comments about understanding sound waves), presumably because you know of experiments that have demonstrated their existence. We have experiments that have demonstrated the existence of EM waves. So the questions is, what in your personal aesthetic tastes is making atoms more palatable? The question of interpreting quantum mechanics is quite different. We do not have a popular mathematical framework that clearly explains why we perceive a classical world while being "inside" of a quantum wavefunction. There is plenty of vagueness and oversimplification in that last statement, but the difference is "we have an abstraction that explains mostly-perfectly EM waves and we do not care about whether people are comfortable with the abstraction" vs "we do not even have a mathematical abstraction explaining why we perceive a classical world inside of a quantum universe".

dools 4y ago
> what in your personal aesthetic tastes is making atoms more palatable? It’s pretty easy for me to imagine things bumping into each other because I see that happening all around me
- consilient 4y ago
  Atoms aren't anything like that though. There are no little billiard balls, probability densities don't "bump", electrons don't actually orbit, and so on. Atoms just are what they are, and what they are does not admit a good "macrophysical analogy".
  - TedDoesntTalk 4y ago
    > There are no little billiard balls … electrons don't actually orbit Wait, what? What do they do then? My physical science education ended in high school.
    - consilient 4y ago
      The next useful falsehood on the ladder is that electrons in an atom exist as probability densities around the nucleus. Fire a photon here, and knock an electron off with this probability; fire it there, and get that probability instead. But before they interact with something, electrons aren't anywhere in particular. https://en.wikipedia.org/wiki/Atomic_orbital https://en.wikipedia.org/wiki/Atomic_orbital The real answer is that constituent parts of bound states like atoms don't really exist as separate things. An atom is a particular very complicated field configuration, and if you want anything deeper than that you're going to have to learn QFT.
      - tux3 4y ago
        If constituent parts of bound states like atoms don't really exist as separate things, how come electrons in metals can move around readily? Is it that they're not really bound, or is it just that they 'attach' and 'detach' easily? When I think of chemistry, it seems like even if there's some sense in which the bound atom is one big writhing mass of fields, the whole atom doesn't interract in a uniform way with the outside, right? The electrons interract with the outside a lot, the nucleus is harder to get to? Is it wrong to say the layer of my onion exist as separate entities, when they seem to interract largely independently from the core of the onion, like they do in metals and chemistry? (I guess the answer is still "you're going to have to learn QFT" :) But the next falsehood down seems fun to ask about too!)