Engineers tend to be fairly matter-of-fact about the physics they use. Many use entropy on a daily basis as a computational tool without worrying much about its vague, abstract mathematical definition. Such a practical approach is even more important for quantum mechanics.
Famous quantum mechanics pioneer Niels Bohr had this to say about it:
“For those who are not shocked when they first come across quantum theory cannot possibly have understood it.” [Niels Bohr, quoted in W. Heisenberg (1971) Physics and Beyond. Harper and Row.]
Feynman was a Caltech quantum physicist who received a Nobel Prize for the creation of quantum electrodynamics with Schwinger and Tomonaga. He also pioneered nanotechnology with his famous talk “There's Plenty of Room at the Bottom.” About quantum mechanics, he wrote:
“There was a time when the newspapers said that only twelve men understood the theory of relativity. I do not believe there ever was such a time. There might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper, a lot of people understood the theory of relativity in some way or other, certainly more than twelve. On the other hand, I think I can safely say that nobody understands quantum mechanics.” [Richard P. Feynman (1965) The Character of Physical Law 129. BBC/Penguin.]
Still, saying that quantum mechanics is ununderstandable raises the obvious question: “If we cannot understand it, does it at least seem plausible?” That is the question to be addressed in this chapter. When you read this chapter, you will see that the answer is simple and clear. Quantum mechanics is the most implausible theory ever formulated. Nobody would ever formulate a theory like quantum mechanics in jest, because none would believe it. Physics ended up with quantum mechanics not because it seemed the most logical explanation, but because countless observations made it unavoidable.