Questions tagged [physics]
For questions about the scientific discipline that concerns itself with analysing the laws of nature in full generality
196
questions with no upvoted or accepted answers
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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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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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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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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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When were arrows first used to visualise vectors?
I guess the use of arrows to visualise vectors came before the general notion of vectors, so a more precise question is: when where arrows first used to visualise physical (or mathematical) quantities ...
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Who was the first to estimate the vacuum energy discrepancy by 120 orders of magnitude?
Apparently, this discrepancy is one of the "worst predictions" in the history of science. Clearly the vacuum energy calculation depends on many approximations and it is not clear how it ...
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On Bryce Seligman DeWitt's Name Change
Weinberg, in his memoir on Bryce Seligman DeWitt (available at https://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/dewitt-bryce.pdf) states that
In 1950 two major but totally ...
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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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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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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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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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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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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 as ...
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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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Who found the formula for sequential Stern-Gerlach experiments and when?
Today we know that if you make sequential Stern-Gerlach experiments, where the magnetic fields are at an angle $\alpha$, then the formula for the ratio how the beam splits is
$$p_{1}=\cos^2 \bigg(\...
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What are some outdated concepts in general relativity?
Inspired by outdated concepts in special relativity such as When and why did the concept of relativistic mass become outdated? and Special relativity and imaginary coefficient of the time coordinate, ...
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Did quantum mechanics solve any open problems related to the optical properties of solids?
It is clear that the understanding that matter is made of atoms allows us to refine our calculations and go beyond the usual optics. Quantum mechanics solved many issues like the black body radiation, ...
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In which work was Boltzmann's entropy originally introduced?
I get an impression from this enyclopedia entry
that the primary source of the Boltzmann entropy equation $S = k \log W$ might be
1866, Über die Mechanische Bedeutung des Zweiten Hauptsatzes der ...
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Einstein's overdetermination theory
In 1923 [1], Einstein proposed an idea for a classical theory that would explain some features of quantum mechanics, via the overdetermination of the EoM, so that only certain configurations would be ...
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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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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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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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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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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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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 ...
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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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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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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;
...
user1709
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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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Why did systems theory never gain popularity?
Briefly from wikipedia,
Systems theory is the interdisciplinary study of systems, i.e. cohesive groups of interrelated, interdependent components that can be natural or human-made. Every system has ...
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What's the early history of the "inner quantum number"?
Pais, in his "Inward Bound", describes the early history of spin. He tells us that Goudsmit and Uhlenbeck interpreted Pauli's "doubled valuedness" as spin, while in turn Pauli re-...
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References for Laplace's question regarding Newtonian Gravity
In this lecture by Prof. Frederic Schuller @ 17:49 , it is said that Laplace asked a question if force could be seen equally as curvature of the underlying space which the particle moves in. However, ...
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How did they explain the radiation from hot objects at different wavelengths before the concept of atom was widely accepted?
I was reading about blackbody radiation and came across the following quote.
Planck did not believe in atoms, nor did he think the second law of
thermodynamics should be statistical because ...
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Did Maxwell discuss charge quantization?
I once read in Wikipedia that James Clerk Maxwell included the possibility that charge could be both quantified and continuous. Since the electron hadn't been discovered in 1873, does Maxwell discuss ...
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Upon which incorrect equation of Euler did Sophie Germain rely in her work that won a prix extraordinaire from the Paris Academy of Sciences?
Wikipedia's Sophie Germain; Work in elasticity; Subsequent attempts for the Prize says:
Germain had derived the correct differential equation (a special case of the Kirchhoff–Love equation),31 but ...
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Bardeen's missing talk
Back in 1968, James M. Bardeen gave a talk at the GR5 (5th international conference on gravitation and the theory of relativity), in which he presented a slight modification of the Schwarzschild ...
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What motivated formulation of the Hamilton-Jacobi equation?
I'm late to the Hamilton-Jacobi equation party and would like to know more about the historical context of its origin. What motivated its construction/discovery? What were its affordances over other ...
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How did Rutherford detect the deflected alpha particles?
All I know is that detecting the deflecting alpha particles was a very tedious process, so much so that that was probably one reason why he asked Hans Geiger and Ernest Marsden to do the experiment. ...
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Why is the magnetic force on a current-carrying wire sometimes called the Laplace force?
Educated in the UK, I've been used to calling the force on a current-carrying wire in a magnetic field 'the motor effect force'. But I'm increasingly aware of another (less clumsy?) name for it: 'the ...
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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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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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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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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 "...
user13853
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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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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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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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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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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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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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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 ...
Kirill