Questions tagged [physics]

For questions about the scientific discipline that concerns itself with analyzing the laws of nature in full generality. It is one of the largest branches of natural science. Before applying this tag to a question, please consider using the "theoretical-physics" or "experimental-physics" tags instead, as they are more descriptive.

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7
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142 views

Who first discussed the Lorentz force with respect to special relativity?

The fact that a Lorentz force in a reference frame 1 can become a Coulomb force in another reference frame 2 has always astonished me, especially because the velocities involved are really small. I ...
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134 views

Why is it said that Marie Curie died due to her work but the same isn't said for Fermi?

I learnt in school that Marie Curie died from her work at 66 years. On the other hand, Enrico Fermi, who also handled a lot of radioactive substances died of stomach cancer at the age of just 53. It ...
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90 views

What technology was used to determine the shape of the blackbody spectrum at the 19th century?

The shape of the blackbody radiation spectrum was known in the 19th century from experimental measurements, and before the theoretical discovery of Planck's law. At those times, how did people manage ...
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105 views

What is the origin in the discrepancy between engineers' and physicists' notation of waves?

my question is very simple. Physicists use this notation in order to write a (for example) plane wave: $$ \xi(z) = \xi^+ \mathrm{e}^{+\mathrm{i}kz} + \xi^- \mathrm{e}^{-\mathrm{i}kz}, $$ where $\xi^+$ ...
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152 views

What exactly was Lagrange's "grave mistake" with respect to rotating bodies under hydrostatic equilibrium?

A comment below What would be different about satellite orbits if Earth were prolate? Would we have Sun-synchronous and Molniya orbits? got me reading Wikipedia's Jacobi ellipsoid which begins: ...
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121 views

What's the origin of the claim that a single uranium atom fissioning would release enough energy to visibly move a grain of sand?

There's a fairly widespread claim that the energy released by the fission of a single atom of uranium would release enough energy to make a grain of sand visibly jump. Richard Rhodes's The Making of ...
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136 views

Who introduced the comma notation for partial derivatives?

In general relativity, it is common to use the comma notation for partial derivatives $$\frac{\partial g_{\mu\nu}}{\partial x_\rho} = g_{\mu\nu_,\rho}$$ Where did this notation first appear? Was it ...
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188 views

Origin of the Fourier transform (1878)

I located Joseph Fourier's book, Analytical Theory of Heat (1878), but at first glance it looks like it is all about heat. What did Fourier call the Fourier transform? When did he first use it?
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2k views

Why Doesn't Einstein Get More Credit for Being the Father of Quantum Mechanics?

I'm not simply referring to the notion that Einstein treated the discrete emission and transference of energy (and matter) as "real" physical phenomena, but rather his major continuous role in the ...
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99 views

Physics Curricula of 19th Century French Universities?

What were the physics curricula for 19th century French universities? I am looking for something akin to this distribution of courses at the École Polytechnique, but for other French universities, ...
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566 views

How did Einstein know tensors would be needed in the EFEs?

I'd really never studied tensors until I started studying the Einstein Field Equations. Since then, I have realized they are fairly common tool in physics and pretty basic to understanding many areas. ...
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108 views

Earliest measurement of proton's mass

I was looking for the earliest experiment or the paper which shows the determination of the mass of proton. In NIST CODATA, the mass of proton is listed as "1.672 621 923 69 x 10$^{-27 }$kg"....
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88 views

"Nuclear fusion is 30 years away" since when?

It's a well-known, running joke (or criticism) in the fusion community that Fusion is always 30 years away. refering to the considerable difficulties that harnessing nuclear fusion as an energy ...
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63 views

How did the terms stress and strain come to describe two different things?

In physics, stress essentially captures forces in a body, where as strain captures displacements. Two dimensionally very different concepts. If you look it up in a thesaurus, stress and strain are ...
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147 views

What happened to the undergrad students who attended the Feynman Lecture Series in 1961-63?

Note: This question was originally asked here, but I was wondering if I could get further clarification as this has truly intrigued me. In the academic years of 1962-2 and 1962-3, Richard Feynman ...
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234 views

Identification of scientists in de Gennes book

Petit Point: A Candid Portrait on the Aberrations of Science is a charming book written by the French physicist Pierre-Gilles de Gennes containing short essays on some of the prominent scientists that ...
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118 views

Did Paul Dirac believe in multiple universes?

Prominent physicist Paul Dirac proposed a hypothesis that said that constants and laws of physics would evolve with time into different constants and laws of nature. This hypothesis was used by ...
4
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1answer
203 views

Did old Crookes Radiometers ever have a pair of terminals?

This is a question about old physics lab equipment. This and this question led to the question in SciFi SE Crookes Radiometer at the end of a telescope in old movie scene, something about a comet? ...
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112 views

Who was the first to use the term field in physics?

Faraday, after drawing his lines of force in 19th century, is normally credited as the first to use the term field in physics. But... ... was not the term field used in the context of gravitational ...
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122 views

During the development of QFT was this theory actually used to build any invention like the MRI?

I have always wondered if the equations of quantum field theory were actually ever used in the production of some invention or device other than needed to make predictions about the Standard Model of ...
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170 views

How did Maxwell conclude that $\frac{\partial\bf E}{\partial t}$ was necessary to complete $c^2\nabla \times \bf B= \frac{\bf J}{\epsilon_0}\;?$

As we know $$c^2\text{curl}\;\bf B= \frac{\bf J}{\epsilon_0}$$ is incomplete & in many cases like capacitor give contradictory result against Law of conservation of charge. As Feynman writes; ...
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1answer
286 views

Did Einstein ever refer to the coordinate speed/velocity of light?

In modern parlance we talk about two different speeds of light in general relativity. We distinguish between the local speed of light, which is always $c$, and the coordinate speed of light, which can ...
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110 views

Diffraction pattern of Michelson's echelon

Has anyone used Michelson's echelon (pictured below), a very famous type of diffraction grating in the 1920s? I am wondering how did the diffraction image look like from this type of transmission ...
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27 views

History of experimental verification of the identity of voltaic and static electricity and references

What where the crucial experiments which showed the identity of voltaic and static electricity? How did the experiments work in detail and what are the original references for it? In "A History ...
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54 views

How did the concept of work being the dot product of force and displacement come into existence?

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. ...
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89 views

How much radiation did the Curies get while synthetising Radium?

While Marie Skłodowska's husband, Pierre Curie, died in a traffic accident, she died of cancer. Various sources claim that the radiation she got during their experiments might have contributed ...
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80 views

What was Boltzmann's contribution to the theory of "statistical ensemble"?

In the book "Ludwig Boltzmann, the man who trusted atoms"by C.Cercignani, I read about the thesis according to which it was Boltzmann, not Gibbs who first introduced the concept of "...
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65 views

How did we arrive at the rule of addition of vectors?

I wanted to ask about how they arrived to the rule of addition of vectors. How did they know that if we add the X's and Y's of two vectors they would get a third vector which has exactly the same ...
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71 views

Experimenters regretting throwing away data?

Modern experiments, especially in fields like particle physics, often collect far more data than they can process and save. Similarly, I can imagine that historical experimenters were limited by how ...
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78 views

Different versions of mass during early years of special relativity

My question is basically about four different versions of mass from the early years of special relativity when the concept of relativistic mass was acceptable. I'd appreciate it if you try to keep ...
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60 views

Was the wide use of mercury in experiments in the 19th century related to alchemy?

We know that Newton's hair samples showed high level of mercury and of course he used mercury like crazy in his alchemy experiments (as did many/all alchemists not just in the west but also China) and ...
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65 views

How transparency was explained by corpuscular theory and Young/Fresnel's wave theory

How did the light theories of Newton and Young/Fresnel explain the transparency of materials such as glass, or opacity of materials such as paper and wood? Newton's theory of light was largely based ...
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74 views

Historical accounts of a oft-cited quip by astronomer Walter Baade

I am looking for any documented, historical reference to an oft-cited humorous reply by German astronomer Walter Baade (1893 – 1960). After having asked if other astronomers were familliar with the ...
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225 views

Speed of light in aether

I've been recently reading about the famous Michelson-Morley experimental attempt to detect the Earth motion with respect to the aether. According to Wikipedia, Michelson initially made a mistake ...
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820 views

Why were the Nobel Prize in Physics not awarded in 1916, 1931, 1934, 1940, 1941, and 1942?

I only found the following at the Nobel Prize webpage: Why were the Nobel Prizes not awarded in those years? In the statutes of the Nobel Foundation it says: "If none of the works under ...
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146 views

What was Einstein's contribution to the Einstein-Podolsky-Rosen (EPR) paper?

Do we have any insight or document into theoretical development of the EPR papers both in terms of math, ideas and anything related to actual physical problem. I know that Einstein didn't write the ...
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327 views

What was the need for Lorentz transformation in pre-relativity period?

Why was it necessary for the velocity of light to be invariant between different inertial frames and hence what was the need for Lorentz transformation when it was believed that velocity of light was ...
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70 views

What is the first effect demonstrating the importance (or existence) of quantum coherence?

As far as I know, in the old quantum theory, a system can only reside in a stationary state. There was no Hilbert space, and no linear superposition. Or, a system cannot be simultaneously in two ...
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94 views

Did the concept of the Dirac Sea influence the development of semiconductors like the transistor?

Dirac (1928), (http://rspa.royalsocietypublishing.org/content/royprsa/126/801/360.full.pdf) explained the negative-energy solutions of his equations as holes in a sea of electrons. The concept seems ...
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96 views

Are Brillouin's papers translated into English?

I mean the Brillouin in the WKB method. I want to read his original paper. But it is in French. Is it translated into English? It should be.
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234 views

In which paper did the typical textbook diagrams of the Millikan experiment appear the first time?

There are two typical visualizations for one of the results of the Millikan oil-drop experiment to illustrate that only integer multiples of some elementary charge occur in nature. The first one is ...
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57 views

Who first measured the increase of mass with speed?

Wiki (https://en.wikipedia.org/wiki/Electromagnetic_mass) says that: Thomson (1893) noticed that electromagnetic momentum and energy of charged bodies, and therefore their masses, depend on the speed ...
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90 views

de Broglie's conception of the electron

I've been working on de Broglie's thesis (English PDF, Original French PDF) for a course, and I've found something that's been bothering me. My training is in Physics, and so I'm not particularly ...
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165 views

Around 1904, did the scientific community take the atomic hypothesis seriously?

The time when Thomson discovered electrons, around 1897, what did the scientific community think about the atomic hypothesis? Was there a majoritarian consensus that matter is made of indivisible ...
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56 views

Since when is it commonplace to use conservation of energy for dynamics problems?

If I throw an object, I can derive its trajectory using the forces acted on it. I can also do the same using conservation of energy. Since when is it commonplace to use conservation of energy for ...
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129 views

On the origin of "sandwiches" in quantum mechanics

The term "sandwich" and the verb "to sandwich" appear pretty common but informally in quantum mechanics. Generally when describing some kind of inner product of the form: $$\langle ...
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78 views

Was Becquerel's discovery of radioactivity inspired by his father?

Becquerel was awarded the Nobel prize for his discovery of radioactivity. He was researching phosphoresence and decided one day to place the stuff he used in a drawer to keep it out of the sun. He put ...
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35 views

How did Mach's view on spacetime differ from Einstein's?

We can read in Wikipedia: Mach's principle, in cosmology, hypothesis that the inertial forces experienced by a body in nonuniform motion are determined by the quantity and distribution of matter in ...
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69 views

How was it discovered that the Magnetic force was orthogonal to the B-field and the velocity of the charged particle?

Forces like the gravitational and the electric force are in the direction of the force field. Why is it that the magnetic force is orthogonal to the velocity of the charge and the magnetic field? Was ...
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49 views

Did Newton discuss and/or use the principle of moments?

This question comes from a point of view of a student in current times. The general curriculum for a physics student presents that a static analysis of a simple system requires that the forces in each ...