Questions tagged [history]

History questions are welcome on this site whenever they have any bearing on our modern understanding of physics. However, if a question has only minimal or null bearing on our current understanding, or it specifically requires a historian's skills, toolset, and mindset to answer, then it should be migrated to the History of Science and Maths site. See the FAQ on Meta for more information.

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Was Eratosthenes justified in his belief the earth was round? [closed]

Because I see two flaws with it, firstly he assumes the distance of the sun won't affect the angle at which light hits the pole. If the sun were far closer and far smaller, there would be a change in ...
Shannon T's user avatar
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Practical details on Fizeau cogwheel experiment

Fizeau measured the speed of light using the so-called Fizeau-Foucault apparatus. It consists, if I understood correctly, in sending light to a long distance (in the historical experiment, more than 8 ...
Plop's user avatar
  • 527
11 votes
1 answer
2k views

Was Einstein's version of differential geometry close to the modern version?

The title pretty much gets the whole question across. In particular, did Einstein work with the modern definition of smooth manifolds, or was that formalized later? Did he know about/use the ...
WillG's user avatar
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0 votes
2 answers
193 views

Why $\rm kg$ in daily life but not $\rm kg~m/s^2$? [duplicate]

I had a question regarding weight so here I begin W=mg (where w=weight,m=mass,g=gravitational acceleration) w= kg*m/s^2(kg is the si unit for mass and weight , m/s^2 is the si unit of gravitation) w= ...
Prannav Dwivedi's user avatar
7 votes
4 answers
568 views

Had scientists ever fired single protons/electrons/particles before Einstein's work on the photoelectric effect?

Had scientists ever managed to fire/detect single, individual particles, photons/electrons/etc., before the photoelectric effect was discovered and Einstein's work on it saying that light also acted ...
Tristan's user avatar
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1 answer
89 views

Lagrangian function $L = T- U$ & Lagrange's book "Mécanique analytique" [duplicate]

Lagrangian is function of generalized co-ordinates, generalized velocities and time: $$L=L(q,\dot{q},t)$$ Why the specific form $L=T-U$ is used as a definition of Lagrangian function? Here as usual $T,...
atom's user avatar
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1 vote
1 answer
90 views

Newton's Principia Naturalis: question on Corollary III?

I'm reading Newton's Principia Naturalis and have a question on Corollary III p86: The quantity of motion, which is collected by taking the sum of the motions directed towards the same parts, and ...
Nick's user avatar
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1 answer
205 views

Who created concepts of force, mass and acceleration, and how did Newton discover that force, mass and acceleration are proportional to each other?

I'm trying to better my understanding of Newton's second law. Who created the concepts of force, mass and acceleration, and how did Newton discover that force, mass and acceleration are proportional ...
watchy's user avatar
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3 votes
1 answer
772 views

Why did Rutherford's atomic model predict a continuous emission spectrum for hydrogen?

When researching the flaws of Rutherford's atomic model, I get that one of them is that it predicts the electrons would spiral and collapse into the nucleus. However, I don't understand the second ...
physicsphil's user avatar
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341 views

How did Rutherford conclude that the electrons orbited the nucleus in his planetary model? And another way to explain the mass was mostly in nucleus?

In the Geiger-Marsden Experiment, I get how he knew that the nucleus was positively charged, and I'm assuming he knew it was small because the scattering through large angles only happened every 8000 ...
physicsphil's user avatar
5 votes
3 answers
1k views

When and how was it 'concluded' that there is no air in space?

When was it confirmed/concluded that there is definitely not air in space? And how was the conclusion reached? We see the discussion of 'ether' before Special Theory Of Relativity and there it seems ...
CoolCoder's user avatar
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How was Planck able to measure / determine the such small number of $h$?

Planck constant is equal to $h = 6.62607015\times10^{-34}\ \text{J}⋅\text{Hz}^{−1}$. I read a little bit about the experiment setup about confining radiation into a black body and 'measuring' the ...
Xfce4's user avatar
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9 votes
2 answers
3k views

Is general relativity required from quantum mechanics?

One of the paradoxes against quantum mechanics was claimed by Einstein during one of the Solvay conferences: a paradox called the Einstein box also explained in this question. The solution proposed by ...
Pipe's user avatar
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2 votes
3 answers
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How did astronomers at Edwin Hubble time decide the size of the Milky Way Galaxy and settled the Great Debate?

I have been reading some books about Great Debate that whether the Milky Way Galaxy was the entire universe and Edwin Hubble settled the debate by identifying some Cepheid variable star (V1) in ...
Qiulang 邱朗's user avatar
18 votes
4 answers
6k views

How is Newton's first law of motion different from Galileo's law of inertia? If the two are the same, then why is the first law named after Newton?

Galileo's law of inertia (at least what I've learned) is "A body moving with constant velocity will continue to move in this path in the absence of external forces". And Newton's first law ...
Vedant Rana's user avatar
1 vote
0 answers
103 views

Explaining Quantum Mechanics to Newton [closed]

Imagine travelling back to the turn of the 18th century and having a conversation with Newton, armed with your knowledge of modern physics, in particular, quantum theory. You try to "explain"...
Lili FN's user avatar
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5 votes
1 answer
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In what paper did Einstein posit the cosmological constant?

Einstein's seminal papers On the Electrodynamics of Moving Bodies and Explanation of the perihelion movement of Mercury from general relativity were fundamental in the descriptions of Special and ...
Jim421616's user avatar
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1 vote
5 answers
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Why didn't we change the conventional direction of current after discovering electrons? [closed]

The direction of current is taken to be opposite to that of the flow of electrons, due to the established convention that current is in the direction of the flow of positive charges. My question is ...
Shudhesh Velusamy's user avatar
1 vote
0 answers
75 views

How is the magnetization $M$ of a material measured?

In a linear material under the influence of an external field $H$, magnetization $M$ is given by \begin{align} {\bf M} = \chi {\bf H}, \end{align} so that the total field inside the material is ${\bf ...
Lucas Baldo's user avatar
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21 votes
6 answers
7k views

Why was the neutrino thought to be massless?

Wolfgang Pauli once said (regarding the neutrino): I have done a terrible thing. I have postulated a particle that cannot be detected. Why did he figure it couldn't be detected? Was this because he ...
David Callanan's user avatar
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2 answers
968 views

Why does the metric system use the Celsius scale rather than the Fahrenheit scale?

Part of why I ask this is because the Fahrenheit scale has a higher degree of precision than the Celsius scale. And the Kelvin scale could just as easily been adapted to be an extension of the ...
Mr X's user avatar
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4 votes
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Graviton-graviton scattering in tree level. Based on a talk by Bryce DeWitt

In this talk given by Bryce DeWitt, at page 6 he mentions a problem he gave to one of his PhD students. The problem is to compute the graviton-graviton scattering amplitude in tree level approximation....
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143 views

Is it true that Schrödinger wrote his Schrödinger Wave Equation from his mind? [duplicate]

My physics teachers told me that there is no derivation of the Schrödinger Wave Equation and that Schrödinger actually wrote this equation from nothing. He wrote it from his mind. Even in my book ...
RIPAN BARUAH's user avatar
2 votes
0 answers
60 views

What is the proof of Bohr's quantisation rule? [duplicate]

In his atomic model, Niels Bohr proposed that electrons can be present only in those orbits where their angular momenta is an integral multiple of $\frac{h}{2π}$. That is $mvr=\frac{nh}{2π}$, where $n=...
RIPAN BARUAH's user avatar
0 votes
1 answer
131 views

What is the exact definition of the Universal Gas Constant $R$? One that gives the reason for every formula that has the idea of this constant

We find that $R$ can be derived in many different ways through various relations. Its born out of the concept of an Ideal Gas. However what definition can clearly justify all of the relations based on ...
Lumbini A Tambat's user avatar
4 votes
2 answers
766 views

Which paper introduced the concept of the "Bloch sphere"?

Everyone loves Bloch sphere, but which paper of Bloch was it introduced? The Wikipedia article on Bloch sphere (here), as of 17/May/2021 links to this paper of Bloch “Nuclear Induction” but it doesn’t ...
Yuji's user avatar
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-5 votes
1 answer
186 views

The pioneer anomaly [closed]

The RTG's powering the electronics had to reject hundreds of watts of black body radiation to space. The RTG’s reflected a portion of their radiation onto the backside of the main paraboidal antenna, ...
barry's user avatar
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0 answers
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Slang: "finite value" meaning non-vanishing. Historical reasons behind this [duplicate]

Is any way to sort out the disciplines of physics where one understands under "finite value" a value that cannot be zero? Is any historical justification for this contradictory terminology?
c.p.'s user avatar
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2 votes
1 answer
168 views

Positron discovery

I was reading about Carl David Anderson's discovery of the positron and I have a question. I understand why it was classified as positive electron (due to its curvature direction and amount of the ...
imbAF's user avatar
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2 votes
2 answers
268 views

Lagrange equation 1788, and Hamilton principle 1834

Lagrange's equation and Lagrangian and derived in 1788. It is different from Newtonian mechanics view because Newton emphasizes the external force acts on the body. But the Lagrange's. view is that ...
ann marie cœur's user avatar
5 votes
3 answers
308 views

Problem of infinities in QED

Other than Renormalization what were the other approaches taken to solve the problem (by physicists of that period)? Why were they not as successful as Renormalization?
user avatar
1 vote
1 answer
93 views

Were Kepler's Laws of Planetary Motion the first formal definition of an ellipse?

It seems to me that Kepler's Laws necessitate some definition of an ellipse in terms of a coordinate system. I am wondering whether Kepler's Laws mathematically defined what an ellipse is, or if he ...
Clark Merala's user avatar
1 vote
0 answers
20 views

What are the basic principles of experimental electromagnetism? [closed]

I want to learn about experimental physics in the context of electrodynamics and electrostatics. Basically I'd like to know how we are able to measure different quantities in this field (electric ...
Omer Paz's user avatar
8 votes
3 answers
2k views

Why is thermodynamics beyond doubt? [duplicate]

Eddington once gave the following quote: The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the ...
Larsa se eidaklaxtarsa's user avatar
2 votes
1 answer
494 views

How did Chadwick determine the speed of protons?

Chadwick, or perhaps one of the previous scientists who were working with the neutron experiment were able to determine the velocity of the protons ejected from the Paraffin wax. I thought that the ...
John Hon's user avatar
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5 votes
3 answers
339 views

What motivated Einstein to formulate general relativity?

I never really fully understood what motivated general relativity or why the Newtonian concept of gravity was considered problematic. One thing I always hear is that it is because it doesn't address ...
Justin James's user avatar
2 votes
2 answers
105 views

How did the concept of work come into existence? [closed]

Well this is really a silly question. However I am curious to know about this topic. Concept of each of the quantities discussed in physics have come into existence based on some basic human thoughts. ...
MSKB's user avatar
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1 vote
1 answer
607 views

Bohr's model of atom

In our textbook, under developments that lead to Bohr's atomic model, it is stated Dual nature of electromagnetic radiation. atomic spectra which could be explained only by assuming quantized ...
Qwerty's user avatar
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2 votes
1 answer
337 views

Why was the AC Stark effect only discovered after the laser was invented?

I was reading a paper about the theory of the AC Stark effect, and I was struck by the following assertion: For instance, the first observation of the AC Stark effect initiated by the laser radiation ...
Emilio Pisanty's user avatar
4 votes
1 answer
569 views

How was the superconducting order parameter discovered?

Just wondering if anyone knows the history behind this discovery? The BCS mean field theory suggests a breaking of our $U(1)$ symmetry; hence, a complex order parameter makes sense in that regard. How ...
scruby's user avatar
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2 votes
2 answers
257 views

Which were the standard undergraduate electromagnetism textbooks before Griffiths?

I am curious about the books that were the standard undergraduate electromagnetism textbooks in the 1950s and 1960s before Griffiths took over in the 80s. Any resource recommendation would be welcome, ...
0 votes
0 answers
69 views

Reference for Galileo's Law of Motion

It is stated in some places that one of Galileo's laws of motion is that two objects in free fall in a local gravitational field with different densities will hit the ground at the same time in a ...
Tom's user avatar
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4 votes
2 answers
175 views

How were the RGB Color Matching Functions established from 380 to 436 nm?

I have been reviewing how RGB color matching functions were formed, and I seem to be missing an aspect. The three primary monochrome lights used to generate a color like the target color are roughly ...
Tim's user avatar
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5 votes
0 answers
125 views

A mathematical step done by Schrödinger in his solution to the hydrogen atom I need clarification on [duplicate]

in his paper "Quantisierung als Eigenwertproblem" he begins by introducing the Hamilton-Jacobi equation: $$H\left (q,\frac{\partial{S}}{\partial{q}} \right)=E\tag{1}$$ such that $S$ is ...
Tomka's user avatar
  • 411
2 votes
1 answer
260 views

What is Newton's original definition of mass?

What is Newton's original definition of mass. The following is from the English translation of Newton's Principia by Andrew Motte. "The quantity of matter is the measure of the same, arising ...
itsme's user avatar
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0 votes
1 answer
176 views

The history of Ampère's circuital law and Ampère's force law

How I know and read in the Internet that Ampere realized that two current-carrying wires can exert force on each other. Ampere's force law is: $$d^2\vec{F_{21}}=-\frac{\mu_0}{4\pi}i_1i_2\frac{\hat{r}}{...
stdscience's user avatar
16 votes
2 answers
643 views

Why was Einstein wrong about black holes?

In 1939, Albert Einstein published a paper entitled "On a Stationary System with Spherical Symmetry Consisting of Many Gravitating Masses." In it, he considers the problem of whether it is ...
Thorondor's user avatar
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0 votes
2 answers
146 views

The light of speed and 24 hours

The notions of meter and second had been created much earlier than the speed of light was calculated. The speed of light is $299792458 ~ \text{m/s}$, i.e. it is really close to $300 ~000$ km/s. Also, ...
iou's user avatar
  • 103
0 votes
1 answer
77 views

Book on historic experiments

I am looking for a book which describes in a detailed way the most important experiments in the history of physics. I was googling for it but could not find a satisfactory result. Either the books are ...
1 vote
0 answers
144 views

Why did the scientific community stop using hydrogen as the main measure for the atomic mass unit?

The only thing I could find is that the community switched form one hydrogen atom to 1/16 of Oxygen-16 (which they thought to be the only isotope that exists at time because they had no concept of ...
m_cht's user avatar
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