History of Science and Math Stack Exchange
History of Science and Math Stack Exchange

Questions tagged [quantum-mechanics]

The branch of physics that relates to the behavior of objects, typically particles, on small scales. Probability is very important in quantum mechanics.

Quantum theory was born in 1900, when Max Planck came up with the idea of treating light as tiny bundles, or "quanta". It entered its golden age within a few decades, and formed the basis for what became known as quantum field theory, which is the modern description of particle physics. It has thus far not been possible to formulate a quantum theory that describes gravity; it is thought that a theory of quantum gravity could lead to a theory of everything.

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How did Born come up with the Canonical Commutation relation ($\hat X \hat P-\hat P\hat X=i\hbar$)?

All answers to questions like this dodge the question by saying it's a postulate of Matrix Mechanics, so let me rephrase it. Instead of how to derive the CCR, how does it follow from Heisenberg's matrices: $$\hat…
Phineas Nicolson
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What came first? The Schrödinger equation or commutation relation between $p$ and $x$

Some books like Griffith's begin quantum mechanics with the Schrödinger equation as a postulate while some other text books derive it and state $[x,p]=i \hbar$ as an axiom. I'm not sure which one came first as the operator $\hat{p}$ can be derived…
Weezy
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How did quantum mechanics become well known by (non)-scientific community.

Today it is well known even by the non-scientific community that there is a part of physics that deals with the very small called quantum physics. My question is how this became "common knowledge". I don't imagine there was a headline in a newspaper…
AngusTheMan
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How was the value of the electron's spin ($\pm \frac{\hbar}{2}$) first determined?

The value of the electron's spin is $\pm \frac{\hbar}{2}$. In the paper where Pauli introduces his Pauli matrices he already knows the value of spin. I'd imagine it was through the Ster-Gerlach experiment or through spectral line-splitting, but…
Phineas Nicolson
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Why did Schrödinger choose a cat for his thought experiment?

While Schrödinger's cat thought experiment serves a greater purpose than animal cruelty enjoyment, one of the possible results is a dead cat. Gruesome or not is one's appreciation, but you will always find someone joking about "oh boy this guy must…
Jenayah
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Photon interpretation of G.I. Taylor's diffraction of feeble light

In 1909, Cambridge undergraduate G.I. Taylor published a letter describing his observation of diffraction using light of an extremely low intensity. For years, I've been teaching my students the interpretation of this experiment as demonstrating…
user466
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When was the quantization of spin discovered?

When was the fact that a spin could only have values $S = n/2$? I cannot find any source that says when.
The Bosco
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Do other branches of modern science have interpretations like Quantum Mechanics does?

As a layperson, when one learns about Quantum Mechanics, one also learns about the various interpretations of QM-- Many Worlds, Collapse, Pilot Wave theory, etc. However, as far as I can tell (from google searches), other modern domains of…
user151841
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How did Pauli come to the Pauli exclusion principle?

I would like to understand what are the ideas (or data) on which the famous scientist has based himself to arrive at such a fundamental principle for quantum mechanics.
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Stern-Gerlach: oven, or filament?

I've seen conflicting statements about whether the Stern-Gerlach experiment involved an oven to evaporate a sample of silver or a filament, perhaps a filament made of silver. Is it possible that the latter is the truth, but the former is discussed…
user466
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What did Sommerfeld mean by Bohr's magic wand?

Background From wikipedia: "Bohr's correspondence principle demands that classical physics and quantum physics give the same answer when the systems become large.[5] A. Sommerfeld (1924) referred to the principle as "Bohrs Zauberstab" (Bohr's magic…
More Anonymous
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Why did Schrödinger write a letter to Einstein “apologizing profusely for his duplicity”?

I’m reading “What is Real” by Adam Becker and this is mentioned without any more details. Here is the excerpt. (It’s very possible that it refers to something that was mentioned earlier, which I missed - but I couldn’t find anything.)
Gal
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Who solved the quantum harmonic oscillator?

In continuation of this question, Who introduced the creation and annihilation operators for the harmonic oscillator?, I got curious who came up with the quantum harmonic oscillator originally. I am aware that the simple classical harmonic…
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The history of the equation $\boldsymbol {Et}-\boldsymbol {tE}=\frac{h}{2\pi i}$

Heisenberg already in 1927 quotes this equation as a "known equation".1 Then what is the origin of it? And what is its further history of it, ending in its death? 1 Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik,…
mma
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Who was the scientist who first showed that helium has a bound state, and was he a nazi?

I remember from my quantum course that the first person (I believe in 1927) to show that helium has a bound state, using the variational principle, was a nazi. It was remarked by my professors that he was essentially blotted out the history books,…
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