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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69 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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Dirac and proton-electron annihilation

Wikipedia says: Robert Oppenheimer argued strongly against the proton being the negative-energy electron solution to Dirac's equation. He asserted that if it were, the hydrogen atom would rapidly ...
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1answer
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What is the explanation of rope's strength in Galileo's Two New Sciences?

I'm reading Galileo's Two New Sciences. But as other Scientific Book it is hard. I am having trouble in First day, where SIMPLICO asks this question(Page 7): "But how can one make a rope one ...
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What did Hans Bethe think of von Neumann's quantum logic?

Nobel laureate Hans Bethe was a friend of mathematician-physicist John von Neumann, and he once said: "I have sometimes wondered whether a brain like von Neumann's does not indicate a species ...
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What is the history behind defining temperature as measure of hotness?

I know that when two bodies of different temperature are kept in contact "heat" flows from hotter body to colder. But how did anyone know that it is the "hotness" that flows, one could have said that ...
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1answer
52 views

When was spin of subatomic particles other than the electron discovered?

The idea of a spin angular momentum was first proposed in a 1925 publication by George Uhlenbeck and Samuel Goudsmit to explain hyperfine splitting in atomic spectra. At what time was it measured ...
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1answer
113 views

Einstein praising Sophus Lie

p. 153 of Raúl M. Falcón Ganfornina and Juan Núñez Valdés, “Mathematical Foundations of Santilli Isotopies,” trans. Alan Aversa, Algebras, Groups, and Geometries 32 (2015): 135–308. quotes (but does ...
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64 views

How does the concept of centre of mass came to existence?

I am wondering as how does the concept of centre of mass came into being. Considering the usefulness of the concept how were the physicist able to define such a quantity. I mean was it just trial and ...
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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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1answer
166 views

What is the origin of the concept of reduced mass?

I am looking for the origin of the concept of reduced mass as used in vibrational spectroscopy e.g. vibration of a diatomic molecule. Most of the texts simply define reduced mass as the sum of the ...
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3answers
175 views

Did anyone mention the possibility of antimatter before 1928?

In 1932 positron and annihilation were discovered, but in 1928 Dirac had provided a formula allowing for the positron Did anyone between that date and the discovery of electron ever imagine or ...
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1answer
55 views

What is Leroy Grumman Medal won by theoretical physicist Kenneth G. Wilson?

I happened to find that one of the most important inventors of the renormalization group, Kenneth G. Wilson, won the Leroy Randle Grumman Award Medal in 1986, 4 years after his Nobel prize. Details in ...
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128 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, ...
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113 views

What is the ancient cosmic canon of proportion and its role in the history of science?

Who had direct inside knowledge of the canon through the alleged secret oral tradition? Some possible examples that have been alluded to include Pythagoras, Plato, Euclid, Copernicus, Galileo, Kepler, ...
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1answer
77 views

How was (non-instantaneous) electric current first discovered?

How was (non-instantaneous) electric current first discovered and what were some of the main first thoughts on it?
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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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1answer
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Why do many names of technical and scientific subjects end with “ics”?

The names of many technical and scientific subjects, like mathematics, physics, statistics, etc., etc., end with letters "ics". What is meant by this, if anything? Was there any logic behind it or is ...
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86 views

When did the use of Sine and Cosine as functions become mainstream?

In the work of early physicists like Newton, everything is explained in terms of cumbersome (in today's standards) geometry. They don't talk about "cosines" of certain angle, but about proportions ...
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1answer
83 views

Are these Newton's quotes apocryphal?

I have stumbled upon the following alleged Newton's quotes, but I could not find them in any of their works. No great discovery was ever made without a bold guess. No sciences are better ...
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Who discovered the covering homomorphism between SU(2) and SO(3)?

Who discovered this? It is quite nontrivial and very important in quantum mechanics.
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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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Theory criteria from Misner-Thorne-Wheeler

In chapter 39.1 of Gravitation, by Misner, Thorne and Wheeler, it is asserted, quite reasonably, that a theory of gravitation (and, I assume, quite generally) must satisfy the three following criteria ...
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538 views

What is the origin of the $\hbar$ symbol?

Equations involving Planck's constant, $h ,$ are often simplified by instead writing them in terms of the reduced Planck's constant, $\hbar \equiv \frac{h}{2 \pi}.$ But where did the symbol for the ...
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125 views

Does Einstein's original derivation of $E=mc^2$ exist and what is it?

I read an article published by Scientific American stating that Einstein did not prove the equation within the context of Special Relativity but I am skeptical. I was hoping someone could point me in ...
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1answer
421 views

Why are 'speed' and 'velocity' not given the same name?

Position is a vector. Distance/length is a name of its magnitude. Velocity is a vector. Speed is a name of its magnitude. Acceleration is a name of a vector and its magnitude. Force is a name of a ...
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100 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 ...
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Feynman's statement about the importance of basic science

I remember reading in the line that Feynman saying if the best technicians were tasked to build a radio they would make longer and thicker cables and transfer message but it took a physicist to ...
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Did Werner Heisenberg ever agree or propose the existence of some kind of multiverse?

I was watching a video (https://www.youtube.com/watch?v=muJYTeQlvC4) where the director of a videogame company speaks about one of its most successful games. This game is set in a floating city which ...
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4answers
352 views

Where did the false “equal transit-time” explanation of lift originate from?

It's supposedly a "widely circulated" false claim that wings generate lift because of their asymmetric shape, forcing air above to travel faster so that they meet up on the trailing edge at the same ...
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1answer
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Reference for history of physics with description of mathematical models

I am interested in some reference text, for example, textbook that would describe going from old times (say, Greece) till modern times: 1) definitions of units and measurements 2) describing ...
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85 views

What did people mean by the term Force in earlier times?

Initially I used to believe that before Newton gave his Laws of Motion, people thought that Force was something that caused motion. It was Newton who first said that Force is something that causes ...
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Did Wheeler ever propose the existence of a multiverse containing parallel simultaneous universes?

It is known that the physicist John Archibald Wheeler proposed the existence of a multiverse in the form of a set of cycles of Big Bangs and Big Crunches (Cyclic/Oscillatory Multiverse Model). But I ...
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1answer
122 views

Did physicist David Bohm ever propose the existence of a multiverse?

Did physicist David Bohm ever propose the existence of any kind of multiverse?
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Does Heliocentrism predate Copernicus?

I have seen this mentioned on the interwebs a few times. people have mentioned that some Greek thinkers and Islamic astronomers came up with heliocentrism before Copernicus and that Copernicus copied ...
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How did Gibbs discover Gibbs entropy?

I have read and I think that I agree with the idea that if we have to choose probability distribution for an unknown system then it is a good idea to choose a distribution that has the least bias. I ...
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1answer
107 views

What was this experiment tainted by the observer effect?

I once heard a cautionary tale about the dangers of the observer-expectancy effect. It was at least presented as a true example from the history of science, but I'm having trouble identifying the ...
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122 views

Who discovered Maxwell-Faraday equation, $\nabla\times E=-\frac{\partial B}{\partial t}$? Was it Maxwell or Neumann?

I have been trying to find out who discovered Maxwell-Faraday equation, $\nabla\times E=-\frac{\partial B}{\partial t}$. Was it Maxwell himself, or was it Franz Ernst Neumann who derived it? The ...
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Did Ludwig Boltzmann ever go to Copenhagen or any other part of Denmark?

Did Ludwig Boltzmann ever go to Copenhagen or any other part of Denmark? I also read that he was appointed "Honorary Doctor" by the university of Oslo. Does this mean that he went to Norway? https://...
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1answer
99 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 ...
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1answer
214 views

When and how did the notion/idea of physical constant emerge?

Physical constants (e.g. c, h, G, alpha and so on) play a central role in our scientific theories and they have yet drawn much of controversial flavor into questions concerning the foundational status ...
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1answer
243 views

How were negative numbers first used in physics?

The use of negative numbers in most of today's calculations is natural. But how did the use of negative numbers began in physics? What physical quantity required the introduction of negative numbers ...
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1answer
95 views

Did John von Neumann ever go to any Nordic Country? Did Eugene Paul Wigner ever go to any other Nordic Country apart from Sweden?

I'm researching about the presence of important scientists in Nordic Countries (Iceland, Norway, Denmark, Sweden and Finland). I was hoping that someone could help me since I've not been able to find ...
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Which physicist is this quote attributed to?

There is a quote from a 19-20th century scientist that goes (and I am paraphrasing): New scientific theories are never accepted until old scientist die. Who is this cynical quote attributed to, ...
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133 views

What are the great works of Richard Phillips Feynman? [closed]

What are the prerequisites to read his book? Why Richard Phillips Feynman is so famous? What are great works of Richard Phillips Feynman?
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178 views

How did Henry Cavendish deduce the inverse square law in electrostatics from his experiment in 1772?

An elegant experiment in 1772 by Henry Cavendish. Cavendish charged a spherical conducting shell that contained within it, and temporarily connected to it, a smaller sphere. The outer shell was then ...
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2answers
168 views

What animals or plants were used to illustrate ideas of physics?

This crossed my mind today... There is Schrödinger's cat and Newton's apple. Are there any other famous animals/plants featured in physics in a similar way?
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1answer
74 views

What was Isaac Newton's contribution to optics?

What was Isaac Newton's contribution to optics? I know that he believed in the corpuscular theory of light. Did he know about the laws of reflection ad refraction?
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1answer
140 views

Refraction in Newton's Corpuscular Theory of Light [duplicate]

Newton's theory of light stated that a light travelled in a straight line as small particles. When these particles travelled in a medium, they experienced an attractive force with the particles of the ...
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87 views

Were notable physicists great at math or computing? [closed]

Were famous or popular physicists like Galileo, Newton, Einstein, Feynman predominantly mathematicians or scientists (computing, experimenting, engineering, etc.)? I am curious if people like the ...
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1answer
147 views

How did philosophers and scientists in the 18th century view mathematical explanation?

The 18th century saw a rise in the use of mathematical formalisms to account for natural phenomena. Works of Lagrange, Euler, d'Alembert, etc., were groundbreaking in the history of mechanics and ...