Questions that ask about some aspect of physics research or study which doesn't involve the actual physics. In general, soft questions can be answered without using physical reasoning.

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0
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1answer
37 views

If the axis of rotation is fixed, is it ok to say clockwise torque?

I know that the direction of torque is along the axis of rotation, but would it be acceptable to say, for example considering a vertical thin rod in the x-y plane with a force acting on the bottom end ...
3
votes
2answers
257 views

Where does this term “shell” with prefix “on-/off-” come from?

Is there some historical reasons or is there a specific reason behind it? This question is connected to: Why on-shell vs. off-shell matters?
1
vote
1answer
106 views

Possible error (very minor) in Rovelli's 'Quantum Gravity'?

On page 41 or Rovelli's book, he writes that the Lorentz gauge transformation of the spin co-efficient is: $$w^I_J \to {\lambda}^I_Kw^K_L{\lambda}^L_J + {\lambda}^I_Kd({\lambda}^K_J)$$ Where $w$ is ...
1
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0answers
24 views

Applications of low-dimensional topology to physics [duplicate]

As a mathematics graduate student whose research area lies in low-dimensional topology (more precisely, invariants of 3-dimensional topological manifolds), I heard that there exist multiple ...
2
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1answer
50 views

What is the pressure at the top of a sealed tube being drawn out of water?

Is the atmospheric pressure in a closed container the same as that of the surroundings (1 bar at sea level)? Consider a tube with both ends open with one end dipped into water (like a pipette in ...
0
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0answers
29 views

Can you discern the cause of a time shift? [closed]

Einstein points out that it is impossible ( with out knowing you are on a rocket) to tell whether you are experiencing gravity due to a different position in a gravitational field, or if you are in a ...
0
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1answer
20 views

Concerning Electrogravitics in an inertial frame

Listening to Feynman, He pointed out the fact that if a magnet is in an inertial frame with respect to a coil, there can be no electromotive force and hence no electricity produced. It is only when ...
2
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2answers
86 views

Why “Dark Energy” is called energy instead of force?

The overly simplified explanation I'm giving myself right now is dark energy causes the opposite of what gravity does, that's why the universe is expanding. Now where gravity is a force, why dark ...
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0answers
82 views

What do a theoretical physicist do? What are the “minor” problems of everyday research (the ones you use for PhD thesis)? [closed]

I'm a math lover, and I'm somewhat fascinated by some concepts in physics, but I don't know very much because at school I've studied only classical mechanics (in a rather formulatic way). So the ...
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0answers
17 views

Why have people stopped answering my questions? [migrated]

Why have people stopped answering my questions when I had about 80 reputation (or whatever they called), does your question gets answered depending on how many reputations you have?
0
votes
1answer
22 views

Order of magnitude

When finding out the order of magnitude of quantities, as said in my textbook, we compare the numerical part with $3.2$ (approximately $\sqrt{10}$ or rounded off version of $3.162$) Thus, $9.12 ...
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2answers
134 views

What is the gist of the equations on Alejandro Guijarro's “2/14” “Momentum” blackboard?

The artist Alejandro Guijarro has an exhibit of photographs of a variety of blackboards with physics equations, drawings and text on them, as covered at Quantum Chaos on Display in Top Physicists’ ...
1
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1answer
28 views

How far do atoms move in a wire when whirling it horizontally?

so the question is: I whirl a mass m attached to a wire with length L and diameter d around my head in the horizontal plane. The mass takes t seconds to move around a circle. How far do the ...
1
vote
1answer
47 views

How big was the first transistor?

The first working point-contact transistor made in 1947 by Bell Labs. I'm looking for specific dimensions, all I've been able to find is "Fits in the palm of your hand".
1
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1answer
57 views

How quickly does air return to a vacuum chamber?

I know there are a lot of variables that affect how quickly this would occur. Any information on the topic would be highly appreciated. For sake of argument, lets say 1 square foot chamber, lets say ...
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0answers
36 views

Biographical question on Newton [migrated]

It is said that Isaac Newton, at the age of 23, came home and made his famous discoveries. Who sponsored him? Or did he farm while doing his research?
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0answers
23 views

An easy source to understand classical dynamics — Rigid body Rotation [duplicate]

I've been having an extremely hard time at understanding rigid body rotation. The source that I'm currently studying from has been suggested by 't Hooft on his webpage. It's by Richard Fitzpatrick. ...
0
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0answers
27 views

Good First year physics lecture notes [duplicate]

My course textbook is Halliday fundamental of physics, this book is huge and since each week, they cover a lot of material in lectures (something about 6 chapters of the textbook), I find it hard to ...
3
votes
0answers
91 views

Comparison between Cadabra and other Symbolic Computer Algebra software [closed]

Does anyone has some experience about working with Cadabra and it's (dis)advantage in comparison to other Symbolic Computer Algebra software such as Maple and Mathematica (physics package) in the ...
3
votes
1answer
152 views

Why have $n$, $\ell$, $m_\ell$, $m_s$ been picked as quantum number symbols *in this order*?

I’m learning about electron configurations and don’t quite understand why $n$, $\ell$, $m_\ell$, $m_s$ have been picked as symbols for the quantum numbers. As far as I understand it, the principal ...
2
votes
2answers
106 views

Expectation Value of a Dynamical Variable

In quantum mechanics, we generally take about "expectation values of dynamical variables". However, by the postulates of quantum mechanics, every dynamical variable in quantum theory is represented by ...
2
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0answers
91 views

How did the scientific community receive Einstein's theories when he published them? [closed]

By now, we have had multiple indications through observations and experiments that Einstein's theories on general and special relativity are correct. We recently had our second observation of ...
2
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3answers
63 views

Can a theory be proven by an experiment (or series of) that sustains it?

This is a question that I've always had but it wasn't until the recent news regarding the BICEP2 experiment that I really gave thought about it (please note that the question is general and not ...
0
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1answer
32 views

Looking for a projectile motion experiment tool

Is there a name for the device used in physics experiments when one wants to show that (under certain conditions) if two balls are initially at the same height and one is dropped while the other is ...
0
votes
2answers
48 views

Motorbike with parachute vs normal skydive

Had a strange discussion in the coffeeroom today. The background was a story about a guy that took his motorcycle to transport himself to the airstrip to do a skydive. Since there is no place to put ...
0
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1answer
36 views

All matter made up of energy? [closed]

I keep on hearing that behind all matter is just waves of energy. I even hear that it is made up of small energy tornado-like waves. This is theoretical physics right? If so, how strong is the theory. ...
-2
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2answers
51 views

Studying Physics [closed]

I'm preparing for entry into a Physics degree course, and was planning on a double major in Physics (with a specialization in Quantum Information later) but am now considering a minor in ...
0
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1answer
71 views

What is the role of the speed of light in mass-energy equivalency? [duplicate]

Where does $c$ squared come into play in the equation $E=mc^2$. Multiplication obviously but how does energy equal mass times the speed of light?
0
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2answers
65 views

Should theory be the appropriate term? [duplicate]

Should theory be the appropriate term? I mean, for example, because of the quantum field theory we have been able to find the subatomic particles that it theorized and make the Standard Model. Why ...
12
votes
5answers
322 views

What does periodicity of $e^{-iHt/\hbar}$ mean in physical terms?

The unitary time evolution operator $U(t)=e^{-iHt/\hbar}$ has some distinct flavour of periodicity to it because of $e^{x+2\pi i}=e^x$. Is this periodicity reflected in any way in physical systems? ...
1
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1answer
96 views

Quantum Philosophy a la John Bell

I recently discovered this website http://www.quantumphil.org/ and wondering whether Quantum Philosophy is an actual field, or just an aspect of QM? Apologies if this is in the wrong place.
5
votes
2answers
161 views

What does library number 539 mean in physics books? [closed]

Every book I borrow have have this number in them. Even my library categorizes them with this number. Is it a universal particle physics book number?
1
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1answer
48 views

Info request on studying QIT/QIS or QM with a Computer Science background [closed]

I've been considering a career change for a long time and recently discovered the Two-Slit Experiment, which, to put it frankly, blew my mind. I then started some hefty reading and investigation into ...
0
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1answer
54 views

Pathria's “Statistical Mechanics” first edition [closed]

Does anyone know where I could find and purchase the book "Statistical Mechanics" by R. Pathria, in 1st edition (the 2nd and the 3rd are readily available, but I really need the first). I believe the ...
0
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2answers
61 views

Good ways for learning and cramming formulas? [duplicate]

I got an exam coming up and its numerical based (its pre-university level exam) but really tough. I want to know about various ways and methods to learn formulas. I know how can I derive them but its ...
1
vote
0answers
45 views

Prerequsites for Zee's QFT [duplicate]

What would be a good book or books for a sufficient prerequisite for Zee's book QFT in a nutshell? I have had a course in QM and relativistic QM, but I think there are some gaps that needs to be ...
5
votes
2answers
122 views

What is an effective and efficient way to read research papers? [duplicate]

I will be a grad student in condensed matter theory starting this fall. As an undergrad, I did the basic physics and math courses as well as a few grad classes (qft, analysis, solid state physics ...
0
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0answers
43 views

To all experienced theoretical physicists out there, what is the step by step process in your math education? [duplicate]

I am not doing a physics degree but an engineering degree but i am planning using my free time to self study all the math in preparing myself to self study subjects in theoretical physics. (I've ...
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0answers
19 views

Textbook on Diffusion and Diffusion NMR Spectroscopy

I am looking for textbooks ( Mathematical / Theoretical Physics ) that cover diffusion in general. Although it is not necessary that your recommendation covers it, I am also particularly interested ...
0
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0answers
17 views

Relationship between phase space volume and dynamical entropy

I would like to know if there is any analytical proof or relationship which can show that for a dynamical system in presence of chaos signal, if the phase space volume (PSV) minimization leads to the ...
2
votes
1answer
125 views

Can someone be too late for being a great physicist? [duplicate]

I am a first year physics student, but I am 20 years old (pretty old for my country, average starting age is 18), because I started after leaving med school, which I find extremely jailed in ...
0
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0answers
53 views

How to study physics as a first year student? [duplicate]

I firstly apologise if this question is off the topic. I am a first year undergraduate student and the required textbook for the course Advanced Physics is Fundemental of physics by Halliday. This ...
4
votes
0answers
76 views

Humour: Noble Gases, Music, Feynman diagrams [closed]

Google found these lyrics: I love the morn, to see the first Radon, When the stars Argon, As the night Krypton, And, if it’s cloudy, you won’t Xenon. Years ago, ...
2
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0answers
23 views

Kolmogorov entropy and noise

There are various ways of calculating the Kolmogorov entropy (KE)of dynamical system. According to Pesin's theorum, it is the summation of the lyapunov exponents; frominformation theoretic concet, it ...
-2
votes
2answers
69 views

Unlimited Energy [closed]

My mother recently found a video about "free energy" (something about flying electrons which you can "catch") and was totally fascinated about it. She found that 2 Brazilians invented a machine that ...
6
votes
1answer
136 views

Physical intuition for deformation quantization of Poisson manifolds

First of all, I know almost nothing about physics. I was reading Kontsevich´s paper on Deformation quantization of Poisson manifolds, however I could not figure out what´s the intuition for such ...
2
votes
2answers
103 views

What might be a satisfying criterion to qualify something as having physical existence?

I'm a philosophy undergraduate student who has an interest in, and respect for (as most people do) what physicists know about the world. In philosophy, the traditional criterion of physical ...
2
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0answers
58 views

Quantum Field Theory and Lie Theory [duplicate]

I am reading Vol.1 of "The Quantum Theory Of Fields" by S. Weinberg. However I have come to a halt when connected Lie groups were introduced. I have solid knowledge in elementary group theory and ...
7
votes
4answers
145 views

$1.7\cdot 10^{-24}$ mole apples a day

As the title suggests I was wondering why the International Bureau of Weights and Measures decided a mole to be a standard (SI-)unit. After some research I found I was not alone with this problem. ...
1
vote
2answers
143 views

Does Newton's third law of motion fail anywhere?

Does Newton's third law of motion fail anywhere, including particle physics and other advanced topics?