# All Questions

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### what determines the wavelength of waves on the open ocean?

Looking at the picture below, you can totally see that these are tiny boats. The water is practically washing over the hull of these boat models. But the water has boundaries that are very far ...
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### Double double-slit experiment

Suppose I have a double double slit experiment. That is, I have an electron gun in the center, that shoots entangled pairs of electrons in opposite directions, one to each double slit. I tried to ...
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### Work done on a 15 kg mass [on hold]

I am studying a work problem found in Calculating the Amount of Work Done by Forces. According to diagram C, the 15 kg object has a 100 N force applied to it that moves the object upward ...
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### Physical applications of the mathematical curvature

I was studying multivariable calculus last semester and had one of the topics talking about a curvature, but we had no applications on it. So how does it help in physics? E.g. curvature of curve: ...
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### Is there a standard reference where entropy is set equal to zero in property tables?

For practical considerations, it seems that entropy is only meaningful as a difference between states, like $\Delta s$ going from state A to state B. For an ideal gas, for instance, standard formulas ...
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### Correspondence between wave function and state vector

I am confused with connection between state $| \psi \rangle$ of a quantum system and corresponding wave function $\psi(x)$ (at a given time). I have been told that for every state $| \psi \rangle$ we ...
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### ER = EPR and Time Travel

In Maldacena-Susskind paper arXiv:1306.0533, they propose an idea of $$\text{ER = EPR}$$ the relation between the wormhole and the quantum entanglement. which ER means Einstein Rosen (ER) bridges, ...
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### What is the perceived color of a D-illuminant?

I am implementing a software that simulates the color of the sky. To do this, I use a model that takes as input the sun position and returns the Yxy components of a D-illuminant for each point of the ...
35 views

### Does quantum mechanics require classical measurement apparatus?

I am trying to learn quantum mechanics and I have a question. Landau, in his quantum mechanics book says that it is in principle impossible to formulate basic concepts of quantum mechanics without ...
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### Confusion about state of a quantum system

I am confused with the concept of state of a quantum system. First postulate of QM ussualy says that the wave function of the system contains all information about the state of the system. But reading ...
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### How to derive Kepler's equation?

The Internet lacks, so far as I know, a derivation of Kepler's equation $$M = E - e\text{sin}(E)$$ where $M$ is the mean anomaly, $E$ the eccentric anomaly and $e$ the eccentricity. Since there ...
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### AdS3 soliton of WItten - for Hawking-Page transition

Are there explicit AdS$_3$ soliton solution? in the sense of Witten's Anti De Sitter Space And Holography and Hawking-page transition paper, by doing a $$\tau_E, y ,r \to y, \tau_E ,r$$ from ...
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### Was Einsteins work with relativity necessary for successful space travel?

So I know that Einstein and general relativity had huge impacts on the way we view the world, but how crucial were these scientific advancements to the success of our space programs? Would Newtonian ...
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### According to Penrose, Weyl Tensor=0 is the start/end of the Universe. Must it =0?

If I understand Roger Penrose's theory, as the Universe expands and cools, matter is consumed by black holes. Eventually the black holes collide and evaporate so that there is only energy and the Weyl ...
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### Killing vector contractions along isometric curves

Imagine $\xi_{\nu}$ is a Killing vector field on a manifold. Does $\xi_{\nu}\xi^{\nu}$ remain constant along any isometric curve defined by the Killing vector field? My guess is that yes since as ...
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+50

### Effect of linear terms on a QFT

I was always told when first learning QFT that linear terms in the Lagrangian are harmless and we can essentially just ignore them. However, I've recently seen in the linear sigma model, ...
48 views

### What is relation between electrons and photon? [on hold]

What is the relation between electrons and photons? Why do atoms get excited when their electrons come in contact with photons? Why do electrons go from a higher to lower energy level when emitting a ...
42 views

### What's an ideal wire?

I'm not talking about an ideal wire in a circuit (a wire with infinite conductance). I'm talking about an ideal wire in the case of the magnetic field of an infinite current carrying wire. What ...
56 views

### Why electrons get excited? [on hold]

Why and how are electrons get excited and what happen inside an atom when electrons get excited?
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### Why is the independence of orthogonal vector-quantities always implicit in books/lectures?

The "theorem" that I can "just" separately deal with orthogonal quantities (like horizontal and vertical force or velocity, etc), I never found explicitly mentioned, but just implicitly in the ...
54 views

### Do batteries lose charge?

Say I have a charge of +q and -q on the positive and negative terminals of a battery. If I connect wires to each terminal, but don't connect the wires (essentially creating an open circuit), the ...
42 views

### Time Evolution Operator in Interaction Picture (Harmonic Oscillator with Time Dependent Perturbation)

1. The problem statement, all variables and given/known data Consider a time-dependent harmonic oscillator with Hamiltonian $$\hat{H}(t)=\hat{H}_0+\hat{V}(t)$$ \hat{H}_0=\hbar \omega \left( ...
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### Why do noble gases stabilize plasma discharges?

In the plasma literature, noble gases—usually helium or argon—are frequently said to 'stabilize' plasmas. For instance in this patent, the inventor states that the plasma can be stabilized "by adding ...
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### If we hear a noise long enough, is it going to settle as tinnitus? [on hold]

Some equipment sometimes have a high pitch ringing, and I was wondering out of curiosity: can noises (not only drive you crazy but also) settle and become permanent ringing in your ear if you are ...
18 views

### Angular velocity in fluids (Air resistance)

Few days ago I started making physics engine on directx. As it obvious I have encountered one problem. I can't find formula of air resistance for angular velocity. I only able to find drag force, but ...
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### I want to put a solar panel for the battery bank 48V, 300AH for 12 hrs back up. Please suggest me? [on hold]

Please give me clarification about my problem for which I will be highly thankful of you.
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### Function for curved line in log-log-plot

I've done experiments on the thermo-viscoelasticity of liver tissue and the following results ...
72 views

### Are there any serious alternatives to QCD nowadays?

I've read several posts here where people talk about the history of the developement of the theory of strong interactions. And they mention Regge theory, pomerons, S-matrix and so on. I'm confused ...
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### What is the reason behind why a quantum particle cannot be at rest?

So I've seen different reasonings for this; which is correct, or are they both corollaries of each other? 1) For a particle to be at rest, we would know its momentum and therefore by Heisenberg's ...
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### Computer based on particle's spin pointing up/down but without quantum mechanics? [on hold]

Some questions: 1) Is spin pointing up/down of a particle (by microwave pulse at low temperatures) a filed studied by quantum mechanics or by what? 2) As I understand correctly, none can still ...
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when comb is rubbed with hair, and brought near small pieces of papers, small paper pieces gets a towards comb. Here the comb gets negatively charged and when brought near piece of paper where do ...
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### Three blocks and a pulley [on hold]

Consider the three block and pulley problem below, where a force $f$ is applied to $M$ and we want to find the acceleration that $m'$ undergoes. Suppose there is no gravity or friction in the ...
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### Charging one thing with static electricity by using battery

How can I make one thing to get statically charged by using batteries but not friction ? For example charge a rod so it can attract shredding ?
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### How to calculate the force acting on a magnet due to a solenoid

Can I assume both magnet and solenoid as magnetic dipole and use coulombs law to find the force acting the magnet?
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### What is radiation(in simple words)? [on hold]

I am a student who is interested in scientific facts. I want a simple definition for radiation. Neither too scientific, nor too simple.