Why "Nobody Understands Quantum Mechanics"

This is a continuation of recent posts on the present crisis of modern physics. 

The essence of classical physics as a science is that it can be understood as a theory about the real world that makes sense to a human mind asking for logic and rationality. 

In 1900 a shift was initiated by Planck in his study of blackbody radiation followed by Einstein in his 1905 study of the photoelectric effect, which 20 years later was used to motivate a new form of physics named Quantum Mechanics QM, which became the trade mark of modern physics into present time. 

The trouble with QM is that all leading physicists say and have said for 100 years that "nobody understands QM". The result is a crisis of a modern physics based on QM.

But science is about understanding and so the fact that QM is not understandable, asks for an explanation. 

One way of forming a theory qualifying for not being understandable is to take some triviality and in the spirit of Einstein "elevate it to a Postulate" as a very deep truth about the world. The apparent clash between triviality and deep truth will cause confusion coming out as "nobody understands". This is like viewing 1+1=2 to be a deep truth of mathematics (instead of trivial definition), which if believed would express "nobody understands mathematics"? 

Let us see if this is in fact what happened with a QM growing out from Einstein's "heuristic explanation of the photoelectric effect" in 1905. Einstein started with the following observations made long before 1905:

• Light of frequency $\nu$ impinging on a metallic surface generates a current of electrons only if $\nu$ is bigger than a threshold value characteristic of the metal.
• The energy of electrons scales linearly with the frequency above the threshold, with energy identified with a stopping potential.    

It was believed that this could not be explained within the classical understandable wave theory of light by Maxwell, simply because that theory was not viewed to include the interaction between light and matter manifested in the photoelectric effect. 

Something more appeared to be needed and that was what Einstein offered in his "heuristic explanation" of the form "one incoming photon ejects one electron" or "one photon = one electron" or "one person = one vote":

• Energy balance gives "photon energy  = electron energy + electron release energy". 
• Define "photon energy" =$h\nu$ with $h$ a constant. 
• Conclude "$h\nu$ = electron energy + electron release energy" as the Law of Photoelectricity.  

Einstein here introduced the idea of a photon as "quanta of light" with an energy $h\nu$ picked from Planck. The essence was the scaling of energy with frequency $\nu$ and not amplitude of light, which connected to the nature of the threshold as a demand on frequency and not amplitude.

Einstein thus gave a "heuristic explanation" of the already observed Law of Photoelectricity, which gave him the 1921 Nobel Prize in Physics "for his discovery of the Law of Photoelectricity" as a misconception from "not understanding".

What Einstein did was to associate the energy $h\nu$ to something named "photon", which could be anything and still is not identified as to physical reality, but with the definite ability to kick out an electron from a metallic surface with the same energy $h\nu$ minus a release energy. For sure this was a "heuristic explanation" where the physics of "kicking out an electron" was hidden. It was thus a triviality made into a deep truth, and as such causing confusion ultimately leading to "nobody understands QM".

Is it then impossible to explain the Law of Photoelectricity in classical terms? If we look at the ingredients of incoming light and outgoing electrical current and stopping potential everything looks classical. Even the threshold on frequency can be accepted as classical as a form wave length precision required to release an electron tied to an atom. The energy of a classical wave of frequency $\nu$ scales with $\nu^2$ thus setting incoming light energy per unit length and time. The observed scaling with $\nu$ can then be obtained by partitioning incoming energy into wave length pieces each with energy scaling with $\nu$ into a totality of $\nu$ incoming pieces per unit of time. 

It is thus possible to give a "heuristic explanation" of the Law of Photoelectricity within classical wave physics, because it only involves classical concepts, which is as good as Einstein's resorting to discrete chunks of energy $h\nu$. 

Einstein did not get the Nobel Prize for explaining the Law of Photoelectricity, because his explanation convinced nobody, only for discovering a law that was already discovered. 

Computational Blackbody Radiation gives an explanation of blackbody radiation and photoelectricity in terms of classical wave mechanics without mystery, which can be understood by a high-school student. 

Altogether a basic reason that "nobody understands QM" is that it starts from a triviality of "quantisation" presented as a deep truth about reality as being discrete chopped up in little "quanta".  See also RealQM as "quantum mechanics without quanta" as understandable physics.