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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.

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What was different about Planck's quantization of light compared to Einstein's?

In describing black body radiation Planck assumed that the energy that can be absorbed or emitted by charges is quantized, i.e., they can only absorb or emit certain quantities of energy. But it was ...
Quantum spaghettification's user avatar
13 votes
1 answer
4k views

How did Planck derive the black body radiation formula without using the Bose statistics?

It is so funny that science never develops as in the textbooks. Bose only introduced his statistics in 1924, so Planck could not possibly have used it to derive the radiation formula in 1900. So how ...
John's user avatar
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11 votes
2 answers
791 views

Did wave optics anticipate quantum mechanics?

I heard in wave optics and electromagnetism that Hamilton could have discovered the Schrödinger equation, or that he was the first man who used the expression $$ \Psi(x)= \exp(i S(x)/\hbar)\,. $$ I ...
Jose Javier Garcia's user avatar
9 votes
2 answers
9k views

Why did Einstein oppose quantum uncertainity?

Einstein always believed that everything is certain, and we can calculate everything. That's why he rejected quantum mechanics, due to its factor of uncertainty. But still quantum physics was right. ...
Creepy Creature's user avatar
22 votes
3 answers
16k views

Why were 20th Century German scientists so impressive?

German (and Austrian) scientists of the late 19th - early 20th centuries seem to have been the backbone of most of modern physics - namely quantum theory/mechanics. The following are a few predominant ...
galois's user avatar
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7 votes
1 answer
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What is the original source for Einstein's description of entanglement as "Spooky Action at a Distance"?

Try as I may, I cannot find the original source where Einstein described entanglement as "Spooky Action at the Distance." The work "spooky" is not in the 1935 EPR paper, which was written in English ...
vy32's user avatar
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5 votes
1 answer
319 views

On the naming of quantum chromodynamics

A theory of strong interaction is called quantum chromodynamics (QCD). Particles interacting strongly are supposed to have color charge, for example quarks appear in three "mutations" - red, green and ...
Martin Vesely's user avatar
4 votes
1 answer
86 views

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's user avatar
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17 votes
3 answers
2k views

Did light bulb companies commission Planck to study black body radiation?

Background When introducing Planck's switch to looking at black-body radiation, a number of sources -- like MinutePhysics, the Economist, random online encyclopaedias and even here on HSM.SE (plus ...
Artem Kaznatcheev's user avatar
15 votes
2 answers
2k views

Was Dirac really trying to take the square root of the Klein-Gordon operator?

As a student of physics one will, on several occasions, indubitably hear professors or other physicists (here is an example, from Physics.SE's highest-rep user John Rennie) tell the famous story that ...
Danu's user avatar
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12 votes
1 answer
1k views

How did gyromagnetic ratio come up before quantum mechanics, and who introduced it?

I am really curious about who was the first one to define the gyromagnetic ratio $\gamma$ of a body, i.e. the ratio of its magnetic dipole momento to its angular momentum. It is a very important ...
AccidentalFourierTransform's user avatar
11 votes
1 answer
560 views

Were there serious attempts to model the photoelectric effect classically?

Today we see the photoelectric effect as one of the simplest pieces of empirical evidence that leads to quantum physics. The historical development of the subject, however, seems to have involved much ...
user avatar
10 votes
4 answers
13k views

Who was the first to say "Shut up and calculate!"?

The best thing I could find on the internet was this apparently forgotten article from 2004: N. David Mermin, Could Feynman have said this?, Physics Today 57 (5), 2004.
user 85795's user avatar
8 votes
1 answer
629 views

Who solved the particle-in-a-box model first?

I got curious who invented the particle-in-a-box model first. It is really simple and intuitive. I was googling to find the original author who suggested it but I only get textbook or webpages as ...
Suzanka's user avatar
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7 votes
2 answers
1k views

What was the first journal to have Feynman Diagrams?

I'm writing a paper on the history of Feynman diagrams and am having trouble finding the first paper published by Feynman which features a calculation done with Feynman Diagrams.
TheStrangeQuark's user avatar
5 votes
1 answer
756 views

Who was first to observe or detect photons in the double slit experiment, and how did they do that?

In the early 1800s Thomas Young introduced (a thought-?) experiment also known as the two slit experiment. He discovered the strange way photons created a interference pattern on a screen. There is ...
Marijn 's user avatar
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5 votes
1 answer
523 views

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 ...
Phineas Nicolson's user avatar
4 votes
1 answer
231 views

How did $SU(2)$ came into physics?

It is natural for physicists to consider the group $SO(3)$. Presumably, $SU(2)$ came into physics because of quantum mechanics. How did people realize that when studying rotation of a physical system, ...
John's user avatar
  • 909
4 votes
1 answer
3k views

Original paper for Young's double slit experiments [duplicate]

I'm trying to find the original papers describing Young's double slit experiments including his experimental set-ups and findings. I've tried looking and all I can find is http://www....
TheStrangeQuark's user avatar
4 votes
2 answers
245 views

History of delta barrier in quantum mechanics

I'm interested in finding something out about the history of the problem of the delta potential barrier in quantum mechanics. Which was the first study to propose this problem, and perhaps any ...
Ed Wolf's user avatar
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3 votes
2 answers
316 views

A technical and historical introduction to quantum mechanics

I am curious to understand the history of QM. In particular, how did the physicists conclude that observables can be treated as operators, or the use of complex state spaces, or that Eigenvalues of ...
user2808118's user avatar
3 votes
1 answer
257 views

Bohr-Kramers-Slater (BKS) theory and energy conservation only on statistically basis

I was reading Wikipedia article on Bohr-Kramers-Slater (BKS) theory, https://en.wikipedia.org/wiki/BKS_theory. I encountered two interesting points and need your help to understand the reasons behind ...
PG1995's user avatar
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3 votes
1 answer
315 views

Degenerate States in Quantum Mechanics

In his book on quantum mechanics in the chapter on perturbation theory Dirac says in a footnote: A system with only one stationary state belonging to each energy-level is often called non-...
blackholedynamite's user avatar
2 votes
0 answers
583 views

What did Einstein say about the Dirac equation?

The wiki article on Dirac quotes Einstein as saying of Dirac I have trouble with Dirac. This balancing on the dizzying path between genius and madness is awful. and I don't understand Dirac at all. ...
Adam Herbst's user avatar
2 votes
0 answers
216 views

Who first noted the connection between Heisenberg's uncertainty principle and the Fourier transform?

Who first noted the connection between Heisenberg's uncertainty principle and the Fourier transform?
Marc's user avatar
  • 161
2 votes
1 answer
251 views

Are Wheeler's It from Bit/Participatory Universe and the Multiverse related?

Could I ask you for the relation between Wheeler's ideas and the multiverse? Do you know if these are related? I ask you this because I found this very interesting article written by Kip Thorne with ...
jerard's user avatar
  • 21
2 votes
2 answers
1k views

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 ...
Suzanka's user avatar
  • 105
0 votes
1 answer
149 views

Planck's quantization idea

First of All, I doubt there has ever been any new idea that did not involve intuition. However, most textbooks suggest that the quantization idea was just a mathematical trick, that Planck introduced ...
Karim mohie's user avatar
0 votes
0 answers
111 views

Max Planck and energy quantization idea

Did Planck have an intuition behind the idea of energy quantization of atomic oscillators and radiation, or was it just a mathematical trick to derive his distribution law?
Karim mohie's user avatar