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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1answer
105 views

Why can Perrin's study of Brownian motion demonstrate the existence of atoms

I really cannot see why the Brownian motion is linked with the being of atoms. Cannot it be explained without atoms? You just need some fluctuations.
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1answer
277 views

Was Rutherford's atomic model questioned at the time?

Thomson's atomic model is a static model. Rutherfold's model is a dynamic one. This poses an apparent problem, i.e., the electrons orbiting the nucleus will radiate and fall into the nucleus. ...
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1answer
57 views

Was the pre-special relativity discussion a hot topic in the late nineteenth and early twentieth century?

We know that low-dimensional materials and topological materials are some of the current hot topics in Physics. Did this happen with the pre-special relativity discussions in the late nineteenth and ...
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1answer
26k views

Why did Tesla disagree with Einstein?

Both Tesla and Einstein were brilliant scientists. Tesla said the following on the theory of relativity in a 1935 New York Times interview: "The theory, wraps all these errors and fallacies and ...
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1answer
202 views

Who is the Westphal behind the Mohr-Westphal specific gravity balance? And how exactly did he improve on Mohr?

I'm a Spanish Physics undergrad, and I was writing a report on an experiment we did on the lab, in which we had to measure a solid's density using the so-called Westphal balance (aka Mohr balance, and ...
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3answers
165 views

Biographies on 20th Century physicists

I've recently finished reading Helge Kragh's Quantum Generations and am looking for what to something to read next. I am hoping to find biographies or more information about certain physicists such as ...
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1answer
127 views

Why not proton volt instead of $eV$?

Why is eV used instead of proton V even if they would give the same value? I have this view: from electrochemistry's Faraday's law, scientists first calculated the charge of an electron. Then, they ...
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1answer
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Why did Einstein oppose quantum uncertainity?

Einstein always believed that everything is certain, and we can calculate everything. That's why he rejected quantum mechanics, due to its factor of uncertainty. But still quantum physics was right. ...
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1answer
421 views

Why do we write $E=mc^2$ and not $E=c^2 m$?

My question goes from Phys.SE where people advised me to ask my question here. I always learn in maths and physics when something is a constant in an equation we have to put it before which varies. ...
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1answer
3k views

Old square bracket notation for units

As discussed in this answer https://physics.stackexchange.com/a/77691/667 there are several common conventions for the notation $[q]$ of a physical quantity $q$. However, I often see people to put ...
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1answer
104 views

who was the first to discover the Hamilton principle of classical physics?

Who, besides Hamilton, was instrumental in discovering at least part of the so-called Hamilton principle? $$\delta \int_{a}^{b}L(q,\dot q ,t )dt$$ where $ L=T-V$, the Lagrangian. What exactly, was ...
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0answers
91 views

First appearance of the timelike cylinder spacetime

Spacetimes with causality violations go back a bit of a way (at least as far back as Herman Weyl's "Space, Time and Matter" in 1922, followed by the Gödel spacetime in 1949), but one of the simplest ...
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1answer
499 views

How did the publication feat of Einstein's four 1905 Annus Mirabilis papers get through peer review?

Einstein's early career is well-known for the lack of success he had applying for assistant lecturer positions with universities; he could not get a position, and he ended up working in a Bern patent ...
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2answers
770 views

Who is the philosopher Feynman cites as saying that existence of science requires the same conditions to produce the same results?

In part 6 of his lecture series "Character of Physical Law", Richard Feynman remarks: A philosopher once said, "It is necessary for the very existence of science that the same conditions always ...
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1answer
237 views

Why was the question of the nature of light limited to the wave theory or the particle one ?

The question is in the title. I'm obviously refering to the 17/18 th century somewhere around this era.
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2answers
102 views

When did the British science take off?

The first few big scientists like Copernicus, Tycho Brahe, Kepler, Galileo are not British. Then comes Newton. And since then it seems that the British start dominating science. What was the social ...
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2answers
315 views

How Einstein got the first idea for special relativity?

I am reading Big Bang by Simon Singh. Here is the short story (as I understood it): Einstein gets a contradiction by assuming that 1- The speed of light $c$ is constant with respect the ether. 2- ...
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1answer
237 views

What did Millikan expect to find when he tried to disprove the photoelectric effect, but proved it instead?

We know that Millikan ended up proving Einstein's photoelectric equation instead of disproving it. Since he aimed at disproving it, what did he have in mind? In other words, what did he expect to see?
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1answer
100 views

How did people describe the frequency of a wave before Hertz? [duplicate]

It is actually quite strange that the unit of frequency was defined so later. How did people like Newton, Lagrange describe the frequency of a harmonic oscillator?
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0answers
86 views

Who first noticed violation of aufbau principle of elements like Cr, Cu, Pd, Au, and how?

It is often referred to as 'anomalous electron configurations' or 'unusual order of filling of orbitals' of a few elements e.g. Cr, Cu, Nb, Mo, Ru, Rh, Pd, Au etc.
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3answers
2k views

When was it first discovered (or comprehended) that air has weight?

When was it first discovered (or comprehended) that air has weight? Did the ancients know of this, or did they think that air is weightless?
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1answer
138 views

Why did Einstein get a better hearing in Goettingen than Berlin?

Jeremy Gray in his 2008 book writes matter-of-factly that Albert Einstein "found he got a better hearing from Hilbert and Klein in Goettingen than he did from his colleagues in Berlin" (page 326). ...
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0answers
92 views

Taking less than a minute to solve a problem within 10% which was stated in less than 10 seconds?

I believe there is a story about a 20th century sciencist (either Neumann or Feynmann I think) who, at some dinner or some sort of gathering, made the following claim to his fellow colleagues: He ...
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2answers
273 views

Did Kepler arrive at his planetary laws based on Mars's orbit alone?

Kepler apparently arrived at his first two laws based on the Tycho's data for Mars. But Mars has the largest eccentricity except for Mercury, so it is easier to tell the difference between a circle ...
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1answer
135 views

Old textbooks on statistical mechanics

I am going to teach history of physics next semester. Can anyone name some old textbooks on statistical mechanics? By old, I mean written around 1930 or earlier. I would like to compare the old books ...
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1answer
194 views

What were the most important discoveries of Galileo about mechanics?

Galileo was besides an astronomer also a real phycisist or mathemathecian. But what were his contibutions about mechanics like throw and fall and collision? Did he perhaps already knew Newtons first ...
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6answers
2k views

Famous scientists in the Nazi party

Can anyone give a list of famous scientists in the Nazi Party? Is there a complete list?
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1answer
287 views

Who introduced the partition function?

Is it by Gibbs? Or Boltzmann? I do not expect Maxwell. The point is, how was the textbook introduction of partition function today developed.
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4answers
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Why are canonical coordinates canonical?

Canonical coordinates are coordinates $q_i$ and $p_i$ in phase space that are used in the Hamiltonian formalism. The canonical coordinates satisfy the fundamental Poisson bracket relations: \...
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0answers
224 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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2answers
2k views

How did Newton come up with his formula?

In high school students are taught the formula that describes the universal gravitational force $F=G\frac{m_1 m_2}{r^2}$. However it is not taught how and why Newton came up with it. Does Newton give ...
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3answers
709 views

“Cycles” to “Hertz”: Why the shift circa 1970?

Before circa 1970, it was more common to say "kilocycles" than "kilohertz" (and analogously for "mega-," "giga-," etc.). What contributed to "Hertz" becoming more common than "cycles"? cf. the Google ...
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1answer
47 views

looking for specific book about renaissance physics

I read a book a while ago about the history of physics in the renaissance, which treated it as an alternation between physical-causal descriptions (eg. inertia obtains because air molecules are pushed ...
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2answers
312 views

What is Galileo's opinion of Kepler's work?

They are contemporaries. Keper lives from 1571 to 1630, and Galileo lives from 1564 to 1642. The former's life span is contained in that of the latter. So, did Galileo hear of Kepler's work and give ...
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1answer
69 views

Is reference cited by Rene Descarte available?

In 1634 Descarte wrote to Mersenne : let me tell you about an experiment that was published not long ago in Leurechon’s Mathematical Games. It involves a large cannon placed on flat ground, ...
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1answer
244 views

When did people notice the special shapes of snowflakes, and when did they start to study them?

What was the first written account about snowflake shapes and when did physicists start to study the reasons why the form appears and how snowflakes form in the air? Is there any old book that ...
3
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1answer
277 views

How did Kepler make his discovery?

It is often said that he used Tycho's data. But the apparent motion of a planet is chaotic, right? The reason is simply that we are living on and observing from the earth, but not the sun. So, how ...
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1answer
105 views

When was the quantization of spin discovered? [duplicate]

When was the fact that a spin could only have values S = n/2 derived? I cannot find any source that says when.
5
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1answer
195 views

Who discovered the normal mode decomposition of coupled oscillators?

Coupled oscillators can be broken down into a superposition of normal mode oscillations. Who was the first person to solve for this system in this way?
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1answer
159 views

Poincare Quote Regarding Instability

Poincare wrote (english translation of the french) in 1903: ``A very small cause that escapes our notice determines a considerable effect that we cannot fail to see, and then we say that the effect is ...
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3answers
991 views

Did light bulb companies commission Planck to study black body radiation?

Background When introducing Planck's switch to looking at black-body radiation, a number of sources -- like MinutePhysics, the Economist, random online encyclopaedias and even here on HSM.SE (plus ...
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3answers
2k views

Why does Newton claim : “Plato is my friend — Aristotle is my friend — but my greatest friend is truth.”?

Basically, why did Newton write : "Plato is my friend — Aristotle is my friend — but my greatest friend is truth." ? What were the influences of these two on him ?
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2answers
261 views

Did Bruns establish that the 3 body problem has no non-trivial conservation laws?

I'm reading Colin Pask's book Magnificent Principia and in 16.7.2 he states that the difficulty of the 3 body problem is in part tied to the lack of additional conservation laws at our disposal. In ...
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1answer
100 views

When was the electronvolt first introduced?

When was the unit "electronvolt" (eV) first introduced, and by whom? The definition of the eV requires the knowledge of the electron charge $e$, so it must have been introduced after 1909, the date ...
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3answers
418 views

Galileo's Discussion of Uniform Motion

Can someone help me here? the language is archaic. This is (translation of) Galileo If two particles carried at a uniform rate, the ratio of their speeds will be the product of the ratio of the ...
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0answers
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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1answer
68 views

Who first wrote down the spin-orbit coupling term in the atom?

Who first wrote down the spin-orbit coupling term in the atom? Was it Dirac himself? The term should be derived from the Dirac equation.
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2answers
708 views

Why couldn't Huygens explain diffraction using his principle?

Huygens' principle seemed quite complete in this description if applied correctly. I noticed that Fresnel was credited in the Huygens-Fresnel principle, as well. I think it is because he was able to ...
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1answer
539 views

Different sign conventions in thermodynamics different for physics and chemistry

Why are the sign conventions of work done in thermodynamics different for physics and chemistry?
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2answers
752 views

Why the thermoelectric figure of merit is denoted “ZT”?

Why the thermoelectric figure of merit is denoted ZT? Does ZT come from the abbreviation of words in some language? Update: So far T has been figured out --- it is the temperature to make the whole ...