alt Hacker NewsI Don't Understand Quantum Physics (2018)
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Saying I don't understand Quantum Mechanics is like saying, "I don't understand how attention/transformers explain the human brain."
It doesn't. It's model. All models are wrong (including quantum mechanics and attention) but some are useful. You understand the domain of the model, the problems it can solve, the math behind the models and use the model to make predictions. If you are competent at linear algebra and functional analysis, you can do quantum mechanics.
If you make the error of believing that quantum mechanics is ontological god's honest truth of nature, you will end up with blunders like using it to explain consciousness like Prof Penrose. His math was impeccable, but he was making a category error.
Somewhat related: a book that really helped me is Picturing Quantum Processes by Bob Coecke. It's a visual representation of quantum processes, which really helped me understand the concept
This piece looks great, adding to my ever-growing "to read" collection on Zotero.
If anyone is interested in self-studying quantum physics, QFT for the Gifted Amateur [1] is very well regarded.
I started to read from "3.1 The Ultraviolet Catastrophe" and this sentence
"The number of different wavelengths of electromagnetic radiation, N(λ)dλ, with wavelengths in a small interval between λ and λ + dλ, (dλ means a small interval in wavelength) can be shown to be proportional to 1/λ⁴."
doesn't make sense. It should not talk about a number of wavelengths, but the number of allowed standing-wave modes (number of eigenmodes that a mathematical solution to the electric field in the relevant situation has) in the small wavelength interval.
That pre-determined value idea is exactly local hidden variables, and Bell's inequality rules it out, Aspect's 1982 CHSH experiment measured the violation.
In a podcast, Alain Aspect (Nobel Prize winner) explained that he does use the power of visualization and his imagination to generate new ideas, but that he always needs to check them with actual calculations because no mental picture can be an accurate representation of quantum physics.
How strange to see a familiar name here! I wasn't his PhD student but worked in the same department as Douglas Ross, and can only say that he was warm, extremely intelligent, with a very strong natural intuition about high energy physics, enjoyed puzzles, and wouldn't shy away from quizzing people giving talks. I remember he had a back and forth with a visiting speaker for about 20 minutes on some minutia!
I don't have much to add on the article itself except that it's almost certainly worth reading.
I take issue with "understand". I agree QM can not be understood in terms of everyday experience. One must build experience, language and proper metaphor for the understanding. For example, in the intro Ross uses the example of explaining a waterfall to someone who never saw it. He says that can be done but he relies on implicitly the listener knowing what people on Earth may take for granted. That understanding of a waterfall can only happen if the listener already has some understanding of fluid flow and gravity. We do, but say a newly found alien friend from a dry environment that had never experienced fluid flow would not have the mental building blocks to understand it. Feynman gave a famous interview where he said, essentially, "no, I can't explain it to you because you are too ignorant" (he said it more politely). Going the other direction, Physics steeped enough in quantum theory do understand QM enough to have meaningful discussions free (at times) of rigorous math. They do this because they have a shared language, vocabulary, metaphor. Sure, they must rely on math and experiment to ground that understanding in truth but I guarantee they do not communicate understanding (solely) in math and measurement data.
"I think I can safely say that nobody understands quantum mechanics."
- Richard Feynman
I loved the book QED: The Strange Theory of Light and Matter by Feynman as a child. Funny enough I always saw QM from a path integral PoV, a decade before I got to learn the formalism
We understand quantum mechanics well enough to build machines that depend almost entirely on quantum principles.
It sounds all superior and mysterious to quote Feynman here, but the fact is many people absolutely do understand quantum mechanics.
"IS QUANTUM PHYSICS CORRECT AND COMPLETE?" is reductive, there are more quantum denominations: Copenhagen, QBism, RQM, consistent histories, Many-worlds, Bohmian mechanics, and various spontaneous collapse people. I might've missed a few.
2 things to understand about science:
It's useful, not metaphysically real. (Hot take btw) This is called Instrumentalism. The belief that it's real is called Scientific Realism. However over and over again, science can't cover edge cases, and we find better fitting models. The Copernician revolution is a good example of this dichotomy.
2. Academia basically forces you to believe the doctrine or you fail the class. From philosophy to physics to sociology. If you read the philosopher survey, you will find trendy things being quite high. It's a religion in itself.
Bonus 3: Philosophical Pragmatism and Instrumentalism generally solves this, but is intellectually a dead end. There is a reason analytic philosophy continues despite gaping holes in linguistics (late Wittgenstein) that ruin it. But at the same time, best fits might be missing a new paradigm. I wish I could tell people to ask AI to explain Hegel to understand, but I think people need to read it themselves.
Tl;dr: quantum mechanics is the best we have. It's definitely wrong, but it's the most useful we have.
Unpopular opinion I think, but I still believe the physics world was wrong to chase the Copenhagen interpretation.
The math does indeed work, and many experiments and practical uses seem to show that there is something to quantum broadly. But to throw determinism out the window and believe that quantum is fundamentally probabilistic, and that one can never really run scientific experiments because observing state collapses superposition, has always seemed asinine to me.
I could be completely wrong, but it's always seemed obvious to me that the need for probabilities in quantum is a clear indicator that something is missing in the theory. I'm never surprised when a person can't understand quantum as its described today.
me neither! How does the Einstein Rosen Podosky Paradox work? can the unknown that's being collapsed not be a pre-determined value that therefore is not traveling faster than the speed of light?
So do the rest of us.
2018 ragebait?
This deserves a [pdf] in the title.
Author: Prof. Douglas Ross of Southampton University - https://www.southampton.ac.uk/~doug/
When I learned about causal sets program and algebraic quantum field theory, I finally (somewhat) understood quantum physics.
Tl;dr spacetime does not exist as a global background where things are "placed", it is not ontic. "Things" are first, and spacetime is derived from interaction statistics of "things". This eliminates nearly all naive paradoxes like double slit etc. Now, these "things" are somewhat complicated and non-intuitive (e.g. there are no individual "particles", they are a limit of discrete distributions), but that's a good start.
The key aspects of quantum physics can be explained very simply. The issue is going in depth without those basics. I often find if someone doesn't get Quantum Physics, it's that source or you need the steps explaining more in-depth. Often sources assume your base knowledge and that is where many fall flat.
My question is, if I just refuse to believe in quantum physics, that makes it go away and/or be inapplicable to me, right?
Uh oh, some people have no sense of humor =\
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"This rather fanciful interpretation of Quantum Physics has now become accepted by many theoretical physicists as being more satisfactory than the Copenhagen interpretation, despite the fact that the mechanism which causes the splitting of the Universe is not explained in any more detail than wavefunction collapse. As you can probably tell, I am in the minority of physicists who finds the Many Worlds interpretation dificult to accept, and not particularly illuminating."
I think these lectures are a good intro to QM. This statement feels very emotional though. Many-worlds just states there is no such thing as wave function collapse. The many worlds are a logical conclusion following. Copenhagen simply refuses to elaborate to when wave-function collapse happens, which to me is not a complete theory.
You could have some critique of many-worlds in relation to statistics, although I think many people have given quite satisfactory explanations.
Many worlds is just bare bones QM.. If any other theory is proposed, it should be falsifiable (like pilot wave theory for example). Doesn't mean it won't be difficult to measure.