# history's questions - English 1answer

586 history questions.

### 5 From the speed of light being an invariant to being the maximum possible speed

As I understand it, the special theory of relativity is based on two principles - that there is no preferred inertial frame (which is common sensical once we realize that all motion is relative motion)...

### 4 How did Arago find the Arago Spot without a laser?

Famously, Poisson showed that Fresnel's wave model of light would predict a bright spot in the very center of a circular shadow, which he interpreted as an absurd result. But Arago was able to perform ...

### 16 What's the significance of the nickel crystal in the Davisson and Germer experiment?

Davisson and Germer, in 1927, conducted an successful experiment to prove the existence of matter waves. What's the meaning of using the nickel crystal? I mean, why didn't they use any other materials?...

### 4 Where did the concept of field come from?

What made scientists start to think about what was previously 'forces-exerted-by' (Newtonian view) to fields (e.g. electric fields and magnetic fields)?

### 5 Why is equipartition law called a theorem too, in some books? [closed]

In some books, the equipartition law is called a theorem. But a law is an observation, and cannot be proved. On the other hand, a theorem is something established using earlier assertions. So what ...

### 21 Did Hilbert publish general relativity field equation before Einstein?

4 answers, 12.846 views general-relativity history
Did Hilbert publish general relativity field equation before Einstein?

### 1 A sound argument for existence of Americas, along al-Biruni's lines?

1 answers, 58 views history geophysics
In 11-th century, Al-Biruni computed circumference of Earth with high accuracy, and mapped all then-known terrain. He then argued that the unknown part of the globe cannot be all ocean, predicting ...

### What experiment confirmed the presence of the electric force between two charged particles?

What experiment confirmed the presence of the electric force between two charged particles physically placed at some distance from each other? In that experiment, were the two particles were ...

### 24 Why metric system uses kilogram as a basic SI unit?

3 answers, 15.864 views soft-question history units si-units metrology
SI system uses all (that I know) measurement basic units as 1 (single) instance: meter, second, ampere, etc, except the KILOgram. It already defined with 1000 multiplier (kilo). It prevents from ...

### When were each of our “ultimate fate of the universe” theories widely accepted?

2 answers, 53 views cosmology universe history
I'm trying to piece together a sort of timeline for the prevailing "ultimate fate of the universe" theories, specifically from the dawn of the twentieth century through today. I know the Big Bang ...

### 42 What was Feynman's “much better way of presenting the electrodynamics” — which did **not** appear in the Feynman lectures?

6 answers, 3.356 views electromagnetism history maxwell-equations
Does anyone know what Feynman was referring to in this interview which appears at the beginning of The Feynman Tips on Physics? Note that he is referring to something that did not appear in the ...

### 1 How did Dirac come up with the idea of using Pauli matrices?

3 answers, 179 views history dirac-equation dirac-matrices
Dirac equation in natural units is: $$\left(i\gamma^{\mu}\partial_{\mu}-m\right)\psi=0$$ where $\gamma^{0}=\pmatrix{I_{2} & 0\\ 0 & -I_{2}}$ and $\gamma^{n}=\pmatrix{0 & \sigma_{n}\\ -\... ### 6 How was the Ancient Greek theory of vision disproved? Ancient Greeks and ancient Indians believed that the way in which vision works is that a beam goes out of the eye and hits an object. Whereas now we know that light reflects off the objects and then ... ### Quantization and wave-particle dualism of light I'm studying atomic spectras and got puzzled about light-quantization. I'll expose my effort to understand it so far. Blackbody radiation Around the year$1900$Planck explained blackbody radiation ... ### 1 Historic method to produce cophasal illumination before lasers? In a bunch of old papers, written before lasers, the authors often refer to illumination with the same characteristics as a laser: single spatial mode and temporally lockstep. For example in: On the ... ### -2 How to prove Kepler's 3rd law? [duplicate] How to prove Kepler's 3rd law? How did Kepler proved it? Is it possible to prove the third law without applying Newton's universal law of gravitation? ### 2 Where does the proportionality symbol originate from? [closed] 1 answers, 54 views history Does anyone know where the proportionality symbol$ \propto $originates from (historically)? As someone who is eager to learn about the history of physics & mathematics, this question popped ... ### 16 How did we 'discover' dark matter? [closed] I'm an astrophysics student and I've been researching this topic and there is one point that keeps eluding me. How did the scientific community realize that there had to be dark matter in the ... ### 3 Feynman lectures: historical updates? 0 answers, 52 views history I'm reading the Feynman Lectures and wonder if there is an overview over the historical Statements such as 12–6 Nuclear forces [...] no one has ever calculated the force between two nuclei Is ... ### 5 Why did physicists in the 1950s and 1960s suspect the weak and EM interactions were at some level the same interaction? Around the 1950s and 1960s there was a lot of work in particle physics motivated by two issues - finding a workable quantum field model for the weak interaction, and finding a model that unified the ... ### 1 Apparition of scale invariance When did "scale invariance" started to be seen as an important concept in the theory of phase transition? Phase transition and critical points started to be investigated in earnest in the middle of ... ### 1 How did Planck arrive at the idea that energy is quantized? [duplicate] Max Planck, arguably the leading theoretical Physicist of his day, apparently used of experimental data to formulate his equation for black body radiation, which was a major step in the birth of ... ### 2 Original Derivations of Euler Equations or Navier-Stokes Equations I've seen the derivations for both viscous and inviscid momentum balance in fluid flow in courses, but I'm curious as to where the original derivation for the equations now referred to Euler equations ... ### 12 Are the LIGO observations proof of a black hole merger, and what happened to the black holes? Recent reports claim that the gravitational waves detected by LIGO match up with the signal expected from two black holes merging as predicted by general relativity. Additionally, the masses of both ... ### 3 How did this apparatus actually work - discovery of induced nuclear fission? Despite all the ugliness threaded through this story, I'd like to understand the physics of this apparatus of Otto Hahn, Lise Meitner and Fritz Strassmann (in alphabetical order). The system shown ... ### 1 Who first noticed that the radiation pressure formula$p=U/c$agreed with$E=pc$from special relativity? Does anyone know behind stories? As it seems that$p=\frac Uc$was known before the advent of special theory of relativity, (Halliday, Resnick, Walker says that Maxwell derived this.) when$E=pc$was ... ### 40 How did physicists know that there are two kind of charges? Problems The question I am about to make is either too stupid or hasn't bothered anyone because its obvious because I can't really find the answer anywhere. I am currently studying electricity and ... ### Proposal of the Virasoro modes and algebra Hi I am wondering what the first published paper on Virasoro modes was? And what about Virasoro algebra? ### 1 Spinor helicity formalism - original reference? The spinor helicity formalism is a modern technique widely used in scattering amplitude calculations nowadays. However, it is hard to find a reference for who first came up with the formalism. Maybe ... ### Has experimental search for free fractional electric charge elementary particles been put to an end? Since Quantum Chromo-Dynamics theory has been supposed to explain quarks confinement, has experimental search for free fractional electric charge elementary particles been put to an end? If not, what ... ### Why do we use$Q$for heat? Of course letters are of few interest if something at all. But when reading some notes the question just appeared: Why do we use$Q$for heat? Googling it shows many links but none of them seems ... ### Has any of Cantor's ideas survived in modern physics? 0 answers, 75 views history mathematics Cantor's reason for devising set theory, i.e., for his "painstaking and hardly rewarding business of investigating point sets", was its application to reality. "I refer you to what I have found in ... ### 1 Have there been any patented physical models or computational algorithms? [closed] 0 answers, 36 views soft-question history algorithms There was a recent question (linked below) on the Law SE about the potential to patent algorithms. It appears there is a lot of gray area in the subject. Of course natural laws cannot be subject to ... ### 2 What was Planck's motivation for the frequency dependence in$E=nh\nu\$?

Many accounts of the history of quantum physics explain how Planck resorted to quantizing energy in an "act of desperation" while attempting to solve blackbody radiation, only to discover by surprise ...

### 1 How could Eratosthenes know the angle of the sun's rays in Alexandria?

1 answers, 104 views astronomy earth history
The measurement of the Earth's radius by Eratosthenes is famously the first of its kind. As I understand, it relies on the fact that the sun's rays are parallel. At noon, the light falls directly ...

### 1 Textbook on the history of General Relativity?

I have studied General Relativity from various textbooks already, and the subject fascinated me immensely. I was wandering if there is any textbook that deals with the chronological "steps" that ...

### 19 What inspired Schrödinger to derive his equation?

I have almost no background in physics and I had a question related to Schrodinger's Equation. I think, it is not really research level so feel free to close it, but I would request you to kindly ...

### 10 Who invented the term “Coulomb logarithm”?

0 answers, 429 views terminology history plasma-physics
Who is the author of the term "Coulomb logarithm"? In fact, Coulomb logarithm was computed by Langmuir in his paper of 1928 where the term "plasma" was introduced into physics, but the term "Coulomb ...

### 2 Why was the fraction 1/31,556,925.9747, in the 1956-1968 definition of the second in terms of ephemeris time, chosen?

1 answers, 100 views time conventions history si-units metrology
The recent question Why are leap seconds needed so often? pulled up some interesting details about the definition of the second, and I'd like to have some of them confirmed explicitly. I'm ...

### 5 Recent missed opportunities à la Freeman Dyson

There is an excellent paper by Freeman Dyson from 1972 (here) and therein the author cites old talks by Hilbert (here) and Minkowski (chapter 2 here) speaking about similar topics, namely how ...

### 2 Corrections to plasmons theory. (History of Plasmons)

Is it true that around 70's there was a huge change in theory that describes plasmons (SPP, to be precise)? Recently I stumbled upon an interesting (but old) paper about plasmons. Authors of that ...

### 1 What was the implication of Quaternions in modern (21th) physics and usage in electrodynamics in 19th century? [closed]

I'm doing a study about number theory in physics where I put some focus into the usage of Quaternions. See: https://en.wikipedia.org/wiki/Quaternion#Use_in_physics Right now I conclude that the ...

### Enrico Fermi's photo and the wrong fine structure constant

This photo about the Italian supreme physicist Enrico Fermi is rather famous. Yet nobody ever questioned, as far as I know, the wrongness of the fine structure constant written on it. So I ...

### 10 Did Newton know or assume that planetary (extraterrestrial) space was frictionless vacuum-space?

For a correct calculus of the perpetual orbital motion of planets as determined by Newton’s laws of gravitation, frictionless motion through interplanetary vacuum space would have been a prerequisite. ...

### What is the physical basis of Born's interpretations?

Did anyone has any idea how Born came up with the probabilistic interpretation of quantum mechanics. It is by all means very bizarre. And then it leads to the idea of copenhagen interpretation. Also ...

### Clarification in deduction of Ampere's original experiments

I am reading Ampere's original work. Therein he describes an experiment called "equilibrium of opposite current experiment". In this experiment, two immobile straight wires with current flowing in ...

### 5 Any photon colliders in the past?

People have been thinking about a photon-photon collider (see this and this) as an add-on or to supplement the ILC, the next generation linear collider. My question is, have there been any photon-...

### 1 Scattering amplitude of strong interactions, Euler's Beta function and strings

On reading the answer by Ron Maimon to the "Gabriele Veneziano, strong nuclear force and beta-function" I became puzzled: Why the fact of the Beta function implication leads to the idea of a string ...

### 9 Gabriele Veneziano, strong nuclear force and beta-function

1 answers, 5.407 views string-theory mathematical-physics history
Background to the question: From The History of String Theory: Gabriele Veneziano, a research fellow at CERN (a European particle accelerator lab) in 1968, observed a strange coincidence - many ...

### 1 Pauli's first paper about the spin

Wikipedia states, that the spin degree of freedom was first formulated by Pauli in 1924: In 1924 Wolfgang Pauli introduced what he called a "two-valued quantum degree of freedom" associated with ...