You can see Feynman explaining mirrors this way in recorded lectures [1]. There's also a recent Veritaseum video explaining why the shortest paths dominate [2].

1: https://youtu.be/SsMYBWpsQu0?si=o1eAEvESwjroTke3&t=2251

2: https://www.youtube.com/watch?v=Q10_srZ-pbs

That sentence brought to my mind all those “How does the mirror know what’s behind the paper?” videos.

We use quantum principles to build things all the time. What are you talking about?

https://en.wikipedia.org/wiki/Quantum_sensor#Research_and_ap... is just a few examples.

Yet so far it failed to do any useful work, correct? As I understand it, even the recent "quantum supremacy" results were about performing a humongous number of useless computations.

Quantum tunneling is key to many devices as well.

Then of course there's the reality that the mere existence of everything we see around us - the stability of atoms themselves - requires quantum mechanics.

Oh wow. So the particle and wave are like a planet and its gravity (in a sort of loosely analogous way)?

But the particle does not generate the wave. There is one wave function governing the whole universe. It is a function on the 3n-dimensional configuration space of all of the particle positions. To find the velocity of a given particle at a given time, one needs to put in the position of all of the particles of the universe. Practically speaking, in an experimental setup, the macro state of the environment is sufficient to create an effective wave function of the particle which is how we can effectively use quantum mechanics on a subsystem of the universe. The collapse of the wave function in measurements is a reflection that once the little system interacts enough with the environment, then the separate environmental configurations have separated out the behavior of the wave relative to the one particle so that an effective collapse wave function can be used.

This plugging in the configuration of all the particles is a gross violation of a relativistic outlook (what is the universal now?). Bell after seeing Bohm's theory immediately grasped the implications and wanted to know if that nonlocality could be removed. His work, along with EPR, was to demonstrate that there was no theory of any kind that could avoid the non locality if results of experiments actually happen when we think they do.

The double slit experiment is perfectly explained by the approximate wave function of the 1 particle system going through both slits and interfering with itself while the particle is guided by that wave which is why there is an interference pattern that builds up out of particular particle dots. There is nothing other than practical difficulties to make the wave separation happen later but have outcomes as if it didn't; it is all about what the wave function is doing as the particle is most likely to be where |psi|^2 dictates it to be. That is what the law of motion assures. One could theoretically simulate the paths conforming to make this happen though the paths themselves could have quite unexpected behavior.

There are various extensions to Bohmian mechanics to deal with particle creation, annihiliation, quantum field theory, and relativistic versions. None are as complete as non-relativistic quantum mechanics in having a mathematically proven existence, but a large part of that is quantum field theory being unsound; the Bohmian part is not a problem. There are avenues being pursued to solve the quantum field theory infinite divergences using Bohmian insights (basically use wave functions that respect probability flowing along with particle creation and annihilation). The work is promising but difficult.

For the relativistic versions, it is easy enough to create a foliation of space-time to create a "now". There are even versions where the foliation is created out of what is already existing structure. Mathematically it seems fine as far as I know. But philosophically, it is weird to have an invisible fundamental structure existing that seemingly contradicts the main lesson of relativity.

If you’ve ever looked into the theory of Orch-OR I’m sure you’d understand what I’m talking about. The minute you think of the quantum being different from the classical is where the problems begin.

Classical physics is the only process we have to understand quantum physics. Our brains are quantum computers that collapse wave functions so we can navigate the universe. And by collapsing the wave function I just mean we make a probability the best certainty we can.

Light as a wave is a probability. Light as a particle is a certainty.

Edit: the Bell experiment is something else. It's like a wave can exist as an entity outside of time and space and only comes back to reality when it interacts. Perhaps it would make sense for electromagnetic waves if the distance and local time elapsed contracts to zero per relativity when travelling at the speed of light.

Or statistical independence fails, no? The CHSH derivation, for example, requires commuting expectation value with conjunction and similar for other Bell-like's that I'm aware of.

This always gets pooh-poohed away with with vague appeals to absurdism, "Alice and Bob's free will blah blah", but I don't really know of a priori reasons why the global state space needs to be Hilbert instead of a more complicated manifold with some Bell-induced metric. If you know of prior art here, I'd love some pointers.

I think we're just seeing decoherence in action here. If the photon interacts with the atom, it becomes entangled with the environment (the atom). Giving the atom a higher temperature results in it having a higher probability of it interacting with the photon, and decohering.

And I think the individual photon doesn't have a mixture of a certain % of wave or particle like nature. It's just that there is a certain probability that it will decohere (interact with the atom), so if you turn up the temperature of the atoms, you'll just see a greater % of the photons decohering when they interact with those atoms.

That's just my amateur understanding of the situation, so I'm happy to be corrected by someone who knows better. Also, I don't have access to the paper itself (https://journals.aps.org/prl/abstract/10.1103/zwhd-1k2t) as it's paywalled and not on scihub.

Quantum mechanics is fascinating!