4 ms·

I'm not a physicist but how much of modern physics is real and not just math?

bowsamic 4y ago
I'm a postdoc in theoretical quantum optics. The answer is: both all of it and a none of it. All of it is real in the sense that Quantum Mechanics has been aggressively and extensively tested against measured observations of reality and has not yet found a discrepancy with it. None of it is real in the sense that it is all a mathematical model that is supposed to make predictions about reality.
- michaelwww 4y ago
  Interesting. So there are mathematical systems that describe reality extremely well and this is testable. There's beauty in that, like the sun flower and Fibonacci. I was looking for something to rekindle my interest in math and this might be it.
- orlp 4y ago
  > Quantum Mechanics has been aggressively and extensively tested against measured observations of reality and has not yet found a discrepancy with it That isn't true. Here's a discrepancy: the universe appears to be following the laws of general relativity, but quantum mechanics does not account for this and returns wrong answers. Here's another discrepancy: quantum field theory predicts an energy density of the vacuum off by 120 orders of magnitude of the observed value. "All models are wrong, but some are useful." But it's disingenuous to claim we haven't even found any discrepancies and that it appears to be a perfect model.
  - bowsamic 4y ago
    Sorry, I meant only non-relativistic quantum mechanics and quantum optics. I don't know anything about QFT or GR
- solarist 4y ago
  Quantum mechanics has been already falsified. Good explanation here: http://backreaction.blogspot.com/2022/05/chaos-real-problem-with-quantum.html http://backreaction.blogspot.com/2022/05/chaos-real-problem-...
  - bowsamic 4y ago
    This is a good point, but that is more of a consequence of the fact that we do not yet know how to recover classical mechanics from quantum mechanics
gus_massa 4y ago
Note that weird stuff is overrepresented in press articles. This is a cutting edge theory, nobody is sure if it's correct or it's a silly speculation. But it has some weird angles that make clicky press articles. Most physics is boring and technical. In particular there are a lot of applications of Quantum Mechanics to Chemistry and Solid State Physics (for example transistors). Even weird stuff like superposition change the properties of small molecules that are easy to test in the lab and simulate in computers. And there are even more weird stuff that mix Quantum Mechanics and Special Relativity, and has effects in Chemistry that are easy to test and Particle Colliders that are also heavily tested. The problem is trying to mix Quantum Mechanics and Special Relativity. We don't know how to do that, but (un)luckily in (almost) all experiments you can choose to use the QM+SR approximation or the SR+GR approximation.

I'm a postdoc in theoretical quantum optics. The answer is: both all of it and a none of it. All of it is real in the sense that Quantum Mechanics has been aggressively and extensively tested against measured observations of reality and has not yet found a discrepancy with it. None of it is real in the sense that it is all a mathematical model that is supposed to make predictions about reality.

michaelwww 4y ago
Interesting. So there are mathematical systems that describe reality extremely well and this is testable. There's beauty in that, like the sun flower and Fibonacci. I was looking for something to rekindle my interest in math and this might be it.
orlp 4y ago
> Quantum Mechanics has been aggressively and extensively tested against measured observations of reality and has not yet found a discrepancy with it That isn't true. Here's a discrepancy: the universe appears to be following the laws of general relativity, but quantum mechanics does not account for this and returns wrong answers. Here's another discrepancy: quantum field theory predicts an energy density of the vacuum off by 120 orders of magnitude of the observed value. "All models are wrong, but some are useful." But it's disingenuous to claim we haven't even found any discrepancies and that it appears to be a perfect model.
- bowsamic 4y ago
  Sorry, I meant only non-relativistic quantum mechanics and quantum optics. I don't know anything about QFT or GR
solarist 4y ago
Quantum mechanics has been already falsified. Good explanation here: http://backreaction.blogspot.com/2022/05/chaos-real-problem-with-quantum.html http://backreaction.blogspot.com/2022/05/chaos-real-problem-...
- bowsamic 4y ago
  This is a good point, but that is more of a consequence of the fact that we do not yet know how to recover classical mechanics from quantum mechanics

gus_massa 4y ago

Note that weird stuff is overrepresented in press articles. This is a cutting edge theory, nobody is sure if it's correct or it's a silly speculation. But it has some weird angles that make clicky press articles. Most physics is boring and technical. In particular there are a lot of applications of Quantum Mechanics to Chemistry and Solid State Physics (for example transistors). Even weird stuff like superposition change the properties of small molecules that are easy to test in the lab and simulate in computers. And there are even more weird stuff that mix Quantum Mechanics and Special Relativity, and has effects in Chemistry that are easy to test and Particle Colliders that are also heavily tested. The problem is trying to mix Quantum Mechanics and Special Relativity. We don't know how to do that, but (un)luckily in (almost) all experiments you can choose to use the QM+SR approximation or the SR+GR approximation.