Comments by "Lepi Doptera" (@lepidoptera9337) on "MIT OpenCourseWare" channel.

  1. Because standing in front of a class is not as easy as you think it is. I only had to do it a couple of times and it was very uncomfortable and made me forget most of what I wanted to say. Some people are better at it than others and that's when you get an exciting lecture without notes. I haven't seen it much, though.
    2
  2.  @ExecuteBrandon  Good for you. Are you teaching physics or something simple, though? ;-)
    2
  3.  @ExecuteBrandon  So you are a bullshit artist. That's what I thought. :-)
    2
  4. There are neither particles nor waves here. There are only quanta of energy. Quanta give rise to a number of phenomena. A large number of quanta of the FREE theory (free as in free of self interaction) can give rise to mean field theories that look a lot like classical waves. Individual charged quanta can undergo annihilation processes but those are NOT part of the free theory. In an annihilation process we have at least two quantum fields (the charged fermionic field and an uncharged bosonic field) that are interacting with each other. Totally different physics.
    2
  5. Interference is not an effect. It's a consequence of the absence of an effect. It only occurs in linear systems that have no self-interaction. We try to teach this in high school using a wave pool or a wave machine. Unfortunately it's a rather subtle learning unit and most students do not understand what it is that we are trying to teach them. Why is quantum mechanics linear? Because individual quantum events are statistically independent. It's baked into Kolmogorov's axioms and it follows from the observation of conditional probabilities, but you would have to develop a solid intuition for probability theory, first, to understand why quantum mechanics follows the same rules and how that leads to linearity of the formalism.
    2
  6. Yes, some people who do not know physics will say nonsense like that. People who do know physics will say the following "A monochromatic electromagnetic wave of frequency 𝜈 exchanges energy with an external system in quanta of energy 𝐸=ℎ𝜈.". No particles needed. Just used the correct definition for "quantum": "Quanta are small amounts of energy.". Yes, the energy of waves is NOT quantized. What is quantized are angular momentum and charges.
    2
  7. No, it is not and gravity does not change any of this.
    1
  8. No.
    1
  9. Some professors were teaching with overhead projectors even 50 years ago. It didn't make the lectures any better. What is important is what you teach, not how.
    1
  10. But it would. You can see quantum mechanics at work in the propagation of light all the way from the other end of the visible universe.
    1
  11. @John-c4r1o It doesn't do that. You get correlation without causation. At a slightly deeper level you can understand quantum mechanics as a direct consequence of special relativity, which means that a classical property of a classical background already carries (almost) all the information about the quantum world in it. The structure of the quantum theory is fully determined by SR, the only remaining degrees of freedom seem to be the choices of effective symmetries at low energies (aka as the QFT and string landscapes).
    1
  12. That, unfortunately, is a misrepresentation of physics. Random variables do not conserve energy, momentum, angular momentum and charge, hence there can be no random variables in nature. What we see is entanglement between local measurements and systems to which we don't have access. That lack of knowledge is not the same as actual randomness.
    1
  13. @ No, we didn't. True randomness means complete independence of everything else. That's an abstract assumption that is simply not true in nature. There are no random properties. There can be no random properties. The real problem isn't that, though. The real problem is that people have been falsely taught to treat randomness as the opposite of determinism. That, however, is a false dichotomy pair.
    1
  14. Yes, with a bit of effort you will be. The problem with QM 101 is not the math. The problem is that you won't have any working physics intuition for what the math really describes. You would have to take atomic physics and nuclear physics in parallel to develop a bit of that.
    1
  15. University is like that. It starts very shallow but then becomes much deeper in no time. You just have to get used to it. You also have to understand that one hour of lecture requires at least eight to ten hours of self-study in addition.
    1
  16. It's just you. ;-)
    1
  17. That explains why people in India are having such a hard time building sewer systems.
    1
  18. He is pointing out that the problem occurred in classical physics and it has nothing to do with quantum field theory. In classical physics we can make repetitive measurements on the same classical body at spacetime points (t0, x0), (t1, x1) etc.. The theory then translates that into a dynamical path variable x(t), even though that is NOT what we are actually observing. In modern physics we have to let go of the x(t) path completely. It simply doesn't exist.
    1
  19. Logic is a commutative algebra. Quantum mechanics follows non-commutative algebras. That follows directly from the unitarity in quantum mechanics. I do agree, though, that programming is NOT a good way to learn physics. Physics is on a totally different and much higher intellectual level than programming. ;-)
    1
  20. We don't have recordings of Feynman's professional lectures for all I know.
    1
  21.  @MegaAvinator  Good guess. K-12 + undergrad equals roughly 15,000 hours of learning. Maybe a little over 20,000 for those who are extremely studious. :-) You know what, though? An AI can be trained to know a hundred times, if not a thousand times more in a month or so. That's just an LLM that can't reason with that knowledge, yet, of course... but just imagine somebody manages to connect that LLM to an actual reasoning model. Now you got a problem. ;-)
    1
  22.  @sheldonrego6121  Yes, it needs undergrad physics, which is two years, three at most.
    1
  23. That's what you said about 1+1=2 in first grade. ;-)
    1
  24. Well, you are scoring high on the troll scale right now. ;-)
    1
  25. Neutrinos are quanta of another field that is closely related to electrons, muons and taus.
    1
  26.  @middlegrounds-was-taken  Quanta are small amounts of energy. That's what quantum mechanics is about.
    1
  27.  @tuckernuts88  Did you pull that turd out of your own rear? Bell simply says that there is a class of classical models for quantum outcomes and that entire class makes different predictions than quantum mechanics does. It doesn't say anything about randomness. Randomness is trivially ruled out by conservation laws.
    1
  28. No, it isn't. You were simply not paying enough attention in special relativity class. ;-)
    1
  29. Depends on how you are reading Planck and Einstein. Conservatively Planck says that thermal emitters can only emit light in quantized energy steps. This is not quite correct and it does not prove field quantization. Conservatively Einstein says that light transfers energy in discrete units to a metal plate in the photoelectric effect. This also does not prove field quantization and it still gets the property that is quantized wrong but it does thicken the plot.
    1