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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40
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2answers
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When exactly (and why) did matrices become a part of the undergraduate curriculum?

Let me tell what I know about this. It is well-known that Heisenberg invented matrix multiplication himself, in his great paper that is considered part of the foundation of quantum mechanics. This was ...
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Whose shoulders did Newton stand on?

In a letter to Robert Hooke in 1676, Newton wrote: If I have seen further it is by standing on the shoulders of giants. Do we know which giants Newton was referring to? And was he referring to a ...
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Writing Mathematical Symbols in 20th century

As I was reading some papers written by Schrödinger and Heisenberg back in 1920s, I noticed that the symbols they use such as the integral or summation sign or calligraphic letters are as if printed ...
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Did physicists around 1900 really believe they were close to “figuring it all out”?

I've encountered the claim that around the end of the 19th century, physicists believed that their understanding of the physical world was close to being complete. One example of this claim can be ...
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1answer
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What were the dominant non-atomic theories of matter in the 19th century?

From what I have read, the atomic theory of matter was cemented by a 1905 paper by Einstein in which he explained the erratic motion of a bit of pollen suspended in water using the assumption that ...
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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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314 views

How soon after or before the development of nuclear applications was waste disposal considered?

Nuclear applications—be it in the form of electricity production, weapon creation, etc.—inevitably involves radioactive waste. When was it realized that there might be a need for a specialized waste ...
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677 views

When did physics texts start to teach Kepler's $3/2$'s power law as a result of Newton's $1/r^2$ law of gravitation, rather than the other way around?

In modern physics textbooks, we teach Newton's laws of motion, then Newton's law of Universal Gravitation, and then Kepler's laws of planetary motion. Specifically, from the $1/r^2$ form of the ...
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7answers
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In ancient times, how did people conclude that the shape of Earth is a sphere?

This is more of a philosophical question, but I want a mathematical explanation. During ancient times, it was well accepted that the surface of Earth was spherical. People first observed this when ...
23
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880 views

Did ancient/medieval non-European cultures have a concept of energy? If so, what are the similarities and differences to the modern concept?

For example, do we find something related to the modern energy concept in Ancient China, Ancient India, or the Islamic Golden Age? Among "similarities and differences", conservation is obviously ...
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What attracted Einstein to the anomalous precession of Mercury?

The story is usually told starting with Einstein's 1915 paper Explanation of the Perihelion Motion of Mercury from General Relativity Theory, or at least its drafts from 1913-14. It was the first ...
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Is Millikan's famous oil drop experiment a fraud?

I read in my mechanics textbook written by Goodstein that Robert Millikan cherry-picked his data in his famous oil drop experiment, and now I'm left wondering about the scientific value of his results....
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What was the vis viva controversy, including its philosophical aspects?

Leibniz's concept of vis visa (literally translated as living force) was a precursor to our modern concept of kinetic energy. His formula for it was close to the modern non-relativistic one: $mv^2$, ...
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Why is there no named unit for momentum but there is one for energy?

Momentum and energy play very similar roles in mechanics, each being changed by the application of force over a interval. For energy the interval is in space and for momentum it is in time. Both have ...
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1answer
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How was Einstein led to make a contact with Differential Geometry for his theory of General Relativity?

General Relativity was developed with Differential Geometry as the tool. How was Einstein led to make a contact with Differential Geometry for his theory of General Relativity? Who suggested him to ...
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1answer
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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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How did scientists plot complicated graphs in the 19th century?

I am wondering how did Maxwell in the 19th century draw such figures as the one shown? What tools or procedures did he need? Is it all compass and ruler drawing?
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Conflict between physics and philosophy

In the old days. stars of physicists like Einstein$^{[1]}$, Poincare, Heisenberg, Pauli, $^{[2]}$ Bohr and so on are quite philosophical mind, and like philosophy. $^{[3]}$ But now, it seems to me a ...
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1answer
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What cipher(s) did Isaac Newton use?

A number of sources including this one assert that Isaac Newton used encrypted messages to communicate some of his scientific discoveries, and as a way of establishing priority. What cipher(s) did he ...
17
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1answer
218 views

Did the Digges Telescope actually exist?

There are many claimants for the first telescope. Amongst these are the claims placed at the doors of Bacon and Digges. The Bacon claim is very sketchy, boiling down to one sentence and is easy to ...
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3answers
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Is this Einstein rejection letter fake?

So I found this on the internet the other day- Is this fake? Are there any ways to prove that it's fake? Does there, if any, exist any real copy of such a rejection letter?(Was Einstein ever ...
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768 views

What became of the Boltzmann-Zermelo debate about the second law of thermodynamics?

At the end of 19th century there was a lively discussion about the nature of the second law of thermodynamics, and its relation to Hamiltonian dynamics. Boltzmann developed a position that the second ...
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4answers
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What led to the rise of Göttingen?

this is a counter part to my other question: What led to the fall of Göttingen?. Göttingen was a major university in which many famous physicists and mathematicians lived. It was located in ...
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3answers
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Why don't we learn Buridan's laws of motion?

My question is why has Jean Buridan faded into obscurity while Newton is venerated as a God by scientists? Here is a description of Buridan's impetus theory: The concept of inertia was alien to the ...
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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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What was different about Planck's quantization of light compared to Einstein's?

In describing black body radiation Planck assumed that the energy that can be absorbed or emitted by charges is quantized, i.e. they can only absorb or emit certain quantities of energy. But it was ...
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951 views

How did we come up with the name “atomic bomb”?

At first, my initiate question was: What is the difference between an atomic and a nuclear bomb?: Nuclear bombs are of two types — those that depend on fission, like atomic bombs, and those that ...
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How did Galileo know that objects rolling down a ramp was an accurate model for free fall?

Galileo used balls rolling down ramps to study the relationship between time and distance traveled. However, without any knowledge of physics, it doesn't seem immediately obvious that the time-...
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1answer
565 views

Hidden agenda of the Galileo trial?

Redondi argued that Galileo's trial on heliocentrism was merely a show trial concealing the real objection against Galileo among the catholic establishment, which was his atomism thought to be at ...
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4answers
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Why Feynman's integral is not taught today more widely and earlier in the academic physics curriculum?

If anyone who has studied path integral of Feynman, you will know that it makes quantum mechanics more like classical mechanics. A student who has learned about the lagrangian will easily understand ...
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758 views

What is the story behind various uses of the word “spectrum”?

Here are five distinct uses of the word spectrum in physics and mathematics: Spectrum (optics): The range of colors in the rainbow Spectrum (particle physics): The range of electromagnetic ...
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2answers
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Who was the first to postulate that space was a vacuum?

The fact that space is a vacuum and that the Earth's atmosphere only extends a short way above the surface is accepted as obvious. However, there is nothing a priori obvious about it: you first have ...
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1answer
551 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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1answer
806 views

When was the vector notation in physics and other sciences first introduced?

The vector notation in physics is a very compact and easy way to write things down, and according to Feynman it also saves print. When exactly did scientists realize that they were summarizing things ...
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3answers
663 views

Why and when did some areas separate themselves from philosophy and some not?

When the Greeks invented science and mathematics in around 600 BC, it was considered as a part of philosophy. Thales of Miletus was a mathematician and philosopher. Aristotle was a philosopher, ...
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2answers
471 views

How did quantum mechanics operators come into being?

Now I am starting to learn Quantum Mechanics. In the class I am taught about operators, postulates and all other basic stuff. I understand operators to be +, -, /, etc; but quantum mechanical ...
12
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1answer
932 views

Why did Einstein stop publishing so many papers in Annalen der Physik?

In his early years (actually, straight through the early 1910s), Albert Einstein published a lot of papers in Annalen der Phyisk, a very old and prominent German scientific journal. However, this ...
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5answers
497 views

Has science fiction ever caused scientists to do real research?

Has science fiction ever caused scientists to do real research? Science fiction here means fiction that tries to explain things in the world rather than speculate about the future or unexplorable ...
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2answers
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Why is kg the standard unit for mass and not g in SI?

Why is $\mathrm{kg}$ the standard unit for mass and not $\mathrm{g}$? I know that there is the kilogramme des Archives which is a kilogram and not a gram. But originally on April 7, 1795 the gram was ...
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1answer
266 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 ...
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When was the cogwheel gear invented?

Can someone tell me what year was the cogwheel gear invented? I tried searching it up but the answers were too complicated.
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Did Richard Feynman ever meet Stephen Hawking or comment on Hawking radiation?

I was just curious what Richard Feynman thought of Stephen Hawking's Hawking Radiation. Feynman was one of the developers of quantum field theory and Hawking's work would have been cutting edge on the ...
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3answers
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Why did Einstein develop General Relativity?

I know that ultimately GR was validated by experiment. I'd like to know however, if there was any experimental discrepancy at the time that pointed to a conclusive flaw in Newtonian gravity, and which ...
10
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1answer
517 views

Why didn't Lorentz conclude that no object can go faster than light?

Based on Lorentz factor $\gamma = \frac{1}{\sqrt {1-\frac{v^2}{c^2}}}$ it is easy to see $v < c$ since otherwise $\gamma$ would be either undefined or a complex number, which is non-physical. Also, ...
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What were Newton's six laws of motion?

In The Norton History of the Mathematical sciences, Ivor Grattan-Guinness writes of Newton's Principia, Indeed, in working drafts for the book Newton considered up to six laws, and this trio are ...
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1answer
521 views

How did gyromagnetic ratio come up before quantum mechanics, and who introduced it?

I am really curious about who was the first one to define the gyromagnetic ratio $\gamma$ of a body, i.e. the ratio of its magnetic dipole momento to its angular momentum. It is a very important ...
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166 views

What explanations are there for this strong spike in the use of 'angular momentum' in the 1960s?

A recent comment called my attention to the Google Ngram for 'angular momentum', which shows a very strong and rather sharp peak in the usage of the phrase shortly after 1960, followed by a steady ...
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1answer
320 views

Cavendish Laboratories Photo, 1939

So this photo of the Cavendish Laboratory is from 1939, and I was wondering if anyone knew any more about who was in the photo. (Click to enlarge) From notes I've been given, I believe the front row ...
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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
759 views

When and how was UV radiation found to be dangerous to human skin?

It is pretty common knowledge nowadays that prolonged exposure to solar ultraviolet radiation is dangerous to human skin, potentially resulting in cancers such as melanoma and photoaging. A bit of ...