Quantum mechanics

Double slit (water waves).JPG
Double slit (electrons)
The double-slit experiment, according to Richard Feynman (Ѻ), is at the heart of central mystery of quantum mechanics.
In science, quantum mechanics is the study of the mechanics of processes and states of systems or bodies from the perspective that matter and energy can be divided into discrete quantifiable units called energy elements or light quanta.

Overview
The rise of quantum mechanics is summarized well by American physical economist Philip Mirowski, who states that following Max Planck's 1901 quantum hypothesis: [1]

“The quanta then began to show up in other important physical theories: the photon theory of light-quanta (1905); the Bohr model of the atom (1913); the structure of spectroscopy (1916); and then, in 1925/26 the full-fledged quantum mechanics of Heisenberg and Schrodinger.”

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History
In 1901, Max Planck introduced the energy element conception, modeled on the earlier 1870s entropy models of Ludwig Boltzmann, albeit discussed in the context of black bodies.

In 1905, Albert Einstein expanded on the work of Planck to argue that light, or electromagnetic energy, can be divided into discrete quantifiable units called “light quanta”, or “photons” as they came to be called in 1926 by Gilbert Lewis, an argument situated in the context of radiation thermodynamics.

The “quantum mechanics” model was further justified in the years to follow in the logic of the principle of elementary disorder viewed in the context of the third law of thermodynamics or heat theorem as devised in 1907 by Walther Nernst in regards to states of systems at absolute zero.

Into the 1930s, following the formulation of the Schrodinger equation, this change in thinking in physics came to be known as the “quantum revolution”, in the corpus of the various scientific revolutions.

Quotes
The following are related quotes:

Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the "old one." I, at any rate, am convinced that He does not throw dice.”
Albert Einstein (1926), “Letter to Max Born”, Dec 4

“Renormalization is but sweeping the infinities under the rug.”
Paul Dirac (c.1930)

“Quantum theory reminds me a little of the system of delusions of an exceedingly intelligent paranoiac, concocted of incoherent elements of thoughts.”
Albert Einstein (1952), “Letter to D. Lipkin”, Jul 5

“The double slit experiment is at the heart of quantum mechanics and in reality it contains the only mystery about which we cannot explain how it works.”
Richard Feynman (1961), “Quantum Behavior”, Feynman Lectures, Ch. 37, Vol 1

“There was a time when the newspapers said that only twelve men understood the theory of relativity. I do not believe that 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. Do not keep saying to yourself, ‘But how can it be like that?’, because you will get ‘down the drain’, into a blind alley from which nobody has yet escaped.”
— Richard Feynman (1965), The Character of Physical Law (pg. 129)

“Quantum electrodynamics is simply a way to sweep the difficulties under the rug.”
Richard Feynman (1965), Nobel Prize speech

“It seems clear that the present quantum mechanics is not in its final form. Some further changes will be needed, just about as drastic as the changes made in passing from Bohr's orbit theory to quantum mechanics. Some day a new quantum mechanics, a relativistic one, will be discovered, in which we will not have these infinities occurring at all. It might very well be that the new quantum mechanics will have determinism in the way that Einstein wanted.”
Paul Dirac (1979)

“Modern physics is governed by that magnificent and thoroughly confusing discipline called quantum mechanics that has survived all tests, is believed to be flawless, but one that nobody understands.”
Murray Gell-Mann (1990), “Some Truer Method: Reflections on the Heritage of newton (pg. 51)

“The authors of physics textbooks are usually compelled to redo the work of the magicians so that they seem like sages; otherwise no reader would understand the physics. Planck was a magician in inventing his 1900 theory of heat radiation, and Einstein was playing the part of a magician when he proposed the idea of the photon in 1905. It is usually not difficult to understand the papers of the sage-physicists, but papers of magician-physicists are often incomprehensible. In this sense, Heisenberg’s 1925 paper was pure magic.”
Steven Weinberg (1992), Dreams of a Final Theory (pg. 68)

“Probably the best way to agitate a group of jaded but philosophically inclined physicists is to buy them a bottle of wine and mention interpretations of quantum mechanics. It is like opening a Pandora’s box. I have been amused to discover that the number of viewpoints often exceeds the number of participants.”
— Artur Ekert (1995) “Pet Theories of Quantum Mechanics”

“It is daydreaming. What counts is what you see on the screen. Do not ask if the particle did follow some continuous path. We do not know about that. Forget about it.?”
Martinus Veltman (2003), Facts and Mysteries in Elementary Particle Physics (pg. 90)

References
1. Mirowski, Philip. (1989). More Heat than Light: Economics as Social Physics, Physics as Nature’s Economics (pg. 83). Cambridge University Press.

Further reading
● Mehra, Jagdish and Rechenberg, Helmut. (2001). The Historical Development of Quantum Theory: the Quantum Theory of Planck, Einstein, Bohr, and Sommerfeld: its Foundations and the Rise of its Difficulties, 1900-1925. Springer.

Videos
● Turok, Neil. (2012). “The Origin of Quantum Mechanics” (V) , MinutePhysics, Oct 14.

See also
Human quantum mechanics

External links
Quantum mechanics – Wikipedia.

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