-1
votes
1answer
41 views

Why can an electric field escape from a black hole?

I know this is a duplicate question but the other answers didn't explain clearly my problem. The talkes about no hair theory for explaining the communication and information problem of matter inside ...
0
votes
0answers
9 views

Flux through a face of a cube for an arbitrary position of a charge

Consider an imaginary cube with edge length a in space. A charge q is placed at the centre of one of the faces of the cube. So, what is the electric flux through the face opposite to the charge? ...
52
votes
5answers
4k views

Why is the detection of gravitational waves so significant?

Since there is to be an announcement by LIGO about this today (11 Feb. 2016), I was wondering why the detection of gravitational waves was so significant? I know it is another confirmation of ...
0
votes
1answer
10 views

electric potential and other potentials

We know that without potential difference no electric current can flow.If two conductors carrying positive and negative charge respectively then the first one will have positive and the rest one will ...
0
votes
1answer
22 views

Relation of conformal symmetry and traceless energy momentum tensor

In usual string theory, or conformal field theory textbook, they states traceless energy momentum tensor $T_{a}^{\phantom{a}a}=0$ implies (Here energy momentum tensor is usual one which is symmetric ...
1
vote
1answer
26 views

Deriving Boyle's law from only the Gay-Lussac laws

My physics professor during a lecture presumably mathematically derived Boyle's law from the two Gay-Lussac laws for ideal gasses. What he said is also printed in his own textbook. He states that, ...
0
votes
1answer
20 views

Polka dot beamsplitter. Is it good for gaussian beams

I am doing pump probe and I am looking for beam-splitter which will not affect beam polarization too much, as I intend to measure polarization dependencies. I have heard of polka-dot beam-splitters ...
0
votes
0answers
9 views

Energy, Power, normalized time-series [on hold]

Given the following (productino of an energy-plant): Total energy production for a year (in Wh) Normalized hourly production ( 0 - 100%): For every hour a value: 100% means full production; 0 % ...
3
votes
0answers
31 views

Why do we assert Hulse–Taylor binary system's orbital decay to gravitational waves and not radiation?

From https://en.wikipedia.org/wiki/PSR_B1913%2B16#Star_system The Hulse–Taylor system's orbit has decayed since the binary system was initially discovered, in precise agreement with the loss of ...
-2
votes
1answer
57 views

Is Lorentz Invariance necessary for Maxwell Equations?

An example shows that Maxwell Equations do not need Galilean invariance, therefore Lorentz Invariance is not needed for Maxwell Equations. The example: In a train moving at a constant speed relative ...
0
votes
0answers
13 views

Heat and mass transfer modes inside rapidly rotating cylinder

My question is about simultaneous heat and mass transfer in rotating cylinder system. System can be detailed as: A rotating cylinder contains wet porous substance in a lump shape. Air stream enters ...
0
votes
0answers
28 views

When is the spin of an electron changing?

An electron can have a half spin up or down. The up spin can become a down spin to lose his weak charge. But when are electrons changing their spin?
0
votes
1answer
24 views

Basic question about valence/conduction bands

In most introductions to solid state physics that I've read, they explain the origin, basically, of the band gap as follows: By doing a superposition of the standing waves inside a BZ, one can find ...
-1
votes
0answers
23 views

Understanding the CSV data for hysteresis curve

I have performed an experiment to evaluate the slope between H and B. In order to do that, I did the hysteresis experiment in oscilloscope. In the oscilloscope I found a curve like this After I ...
0
votes
0answers
49 views

Why the quantization of things is “forbidden” by classical physics?

I would like to know why we say that what gave the idea of Quantum Physics was the fact that things appeared to be quantized Why is it impossible to quantize things in classical physics? Why ...
5
votes
2answers
539 views

How to understand that Higgs does not imply circular reasoning?

From what I understand about Higgs (boson/field) it gives mass to subatomic particles. When it interacts a lot with the fields it gets a great mass (like a top quark) and when it interacts a little it ...
0
votes
0answers
13 views

Neutron scattering off molecules

From neutron scattering off molecules it is possible to get information about molecules' geometry. Given the size of a particular molecule, what are the criteria for choosing the wavelengh of the ...
0
votes
0answers
51 views

Can black holes with the same mass evaporate with different speeds?

I am curious about the following observations: (1) For a normal Schwarzschild black hole, it evaporates according to $dm/dt=-1/m^2$; (2) We have eternal black holes which do not evaporate (though ...
0
votes
1answer
51 views

Meaning of $R=0$, $R_{ab}=0$. $R_{abcd}=0$.

First let me state some definition The Einstein tensor is given by \begin{align} G_{\mu\nu} = R_{\mu\nu} - \frac{1}{2} g_{\mu\nu} R \end{align} and note that \begin{align} G^{\mu}_{\phantom{\mu} ...
-2
votes
0answers
18 views

Electromagnetic field tensor [on hold]

How will we derive the component of electromagnetic field tensor by using the electromagnetic field tensor formula; what is the procedure? Can anyone tell me about how I would derive $F_{00}, ...
4
votes
4answers
112 views

How do they find the energy of a photon?

Is the actual energy of a photon ever measured? How is it done? I read that a photon is usually identified by diffraction, that means its wavelength is measured, is that right? In this way we ...
-2
votes
0answers
15 views

What is the mass defect of stable nucleus? [on hold]

What is mass defect of stable nucleus? A-positive B-zero C-negative D-less than unstable nucleus
1
vote
0answers
20 views

Converting a Bell state to a less entangled state by LOCC [on hold]

How can I convert a maximally entangled state, $ \frac {1} {\sqrt2} (|00\rangle +|11\rangle) $, to a less entangled state like, $$ cos(\theta)|u_0 v_0\rangle + sin(\theta)|u_1 v_1\rangle $$, by using ...
-1
votes
2answers
111 views

A classical explanation of why there is a speed limit in the universe

The question is - is there any flaw in this explanation, or it is the right explanation in general language? Let me break the explanation into two parts - (1) Why there is a certain speed of ...
0
votes
2answers
28 views

Confusion in understanding the derivation of wave speed from Newton's Second Law

In the book 'Principles of Physics' by Resnick,Halliday and Jearl Walker,the opening para of derivation of wave speed from Newton's Second Law is such: Let us consider a symmetrical pulse moving ...
0
votes
2answers
16 views

How to determine the friction constants

We know that the friction is formulated in this form $$F=av+bv^2+Nμ$$ I'm working with an object and surface and I want to find $ a, b, μ $ for them. Can you please give me an experimental method ?
-2
votes
0answers
47 views

Why do you believe in [on hold]

Is it possible that gravity doesn't exist?
0
votes
0answers
63 views

What can be the way of the light [on hold]

All we know that from the Sun to the Earth is comming light. But what can be the motion of the one particle of the light? Its have the source of the light Sun and opened eye on the finish of this ...
0
votes
1answer
23 views

Wave optics physics

When does monochromatic beam of light incident on a reflective surface get completely transmitted.according to the question what exactly the word transmitted means? I'm little bit confused .could you ...
0
votes
0answers
10 views

circular motion pf hc verma [on hold]

a particle of mass m rotates with a uniform angular speed 'w' . It is viewed from a frame rotating about the Z-axis with a uniform angular speed 'z' the centrifugal force on the particle is
0
votes
1answer
19 views

How to apply torque impulse

In the below question, can we apply conservation of Angular Momentum? If not, why? Moreover how do we apply Torque impulse to the system ? The contact force between the cylinders will be normal to ...
-1
votes
0answers
11 views

damage a size D tourch battery will do when thrown forward out a moving vehilce doing 80 kmh

What damage would a size D tourch battery do when thrown hard in a forward direction out a moving vehilce doing 80 km at another vehicle in front of it doing the same speed and would the battery ...
-1
votes
1answer
39 views

Physical Nature of the electric field of the current in a circuit [on hold]

As most of us know that the electric current in a conductor is due to free electrons moving in the conduction band of metallic conductors. What makes them move ? An electric field of course. Today my ...
3
votes
2answers
79 views

Successor to Copenhagen Interpretation as Orthodox Interpreation of Quantum Mechanics

First, I read the questions FAQ for this and I hope this does not violate the rules. I am not asking for personal opinion, but for observations of hard evidence of trends on this subject. When I ...
2
votes
1answer
24 views

Question about the Blandford–Znajek process

I've been trying to understand the Blandford–Znajek process which explains how Gamma Ray Bursts form, but it's still not clear to me how it works. In this article, several theories about the formation ...
1
vote
2answers
55 views

What is the Benefit of Plotting a Log of Net Force vs. Log of Acceleration Graph?

In preparation for a quiz, I've been going over a set of sample questions. One question in particular asks that if I am to graph the logarithm of the horizontal net force of a system vs the logarithm ...
0
votes
0answers
14 views

event horizon vs apparent horizon ramifications

If the event horizon doesn’t exist in the 2-dimension or 3-dimension time-space - and it doesn’t exist if it can’t be measured or observed - then an apparent horizon would be necessary to reconstruct ...
1
vote
1answer
21 views

How do buoyancy control devices (BCD) work?

I get that having more air decreases density and increases buoyancy. However, we can take the diver-BCD-oxygen-tank to be a single system. How can the pumping of air from the tank into a vest around ...
0
votes
3answers
38 views

How do we determine the pressure at the surface of a star?

Is there any means to do so? I know there are some means to determine the surface temperature.
0
votes
2answers
31 views

Free falling object with air resistance, what's the velocity as a function of time?

So, I'm looking into how velocity can be represented as a function of time when the air resistance is also function of velocity. The force of drag is $$ F_d = C||\vec{v}||\vec{v} $$ where $C$ is an ...
4
votes
0answers
59 views

Are there any open questions in physics that a layman can analyze? [on hold]

In math, there are questions like "What is the minimum number of crosses that this knot has?" which can't fundamentally be solved and simply take a lot of trial and error for an answer. This means ...
0
votes
1answer
24 views

Can we determine the surface temperature of stars other than the sun by using the black body radiation theory?

It is well known that the surface temperature of the sun can be determined by fitting the solar spectrum to the black body radiation spectrum. Is this scheme feasible for other stars? Possibly the ...
1
vote
1answer
26 views

Why does a dynamical gauge field accompany fractionalisation?

I'm trying to understand fractionalisation, of which spin-charge separation is an example. I've read that this is accomplished by introducing a Lagrange multiplier field, which becomes a dynamical ...
0
votes
1answer
27 views

Calculating stopping distance of a car on a slope

I'm having trouble setting up a homework problem properly. We are given the following: A given car can brake to a stop from a speed of 60.0 mi/h in a distance of 123 ft on a level roadway. What ...
2
votes
1answer
80 views

Can a particle have an imaginary mass?

Now, I'm not very involved in the physical sciences, beyond some high-school classes - though I did listen to some college lectures for physics. I was reading "Do Tachyons Exist?" by John Baez, which ...
1
vote
0answers
24 views

Scattering in Black Holes

Let's take your favorite Black Hole and consider the scattering problem for a scalar field around it. Suppose that the Klein-Gordon equation can be separated in the radial and the angular part. Which ...
0
votes
1answer
26 views

Degenerate perturbation theory

I don't understand the part about turning off the perturbation. What is meant by or what is he referring to when he says "upper" and "lower" states. Why must the "upper" state reduce to a ...
0
votes
1answer
20 views

What do I need to calculate UV intensity?

I have a mineralogical UV lamp that I want to use for some research, I only know it's wavelengths. To calculate the µJ/cm3, what else is needed? Distance, time, wattage? Is the value I'm looking for, ...
0
votes
1answer
92 views

Which non-Copenhagen interpretations of Quantum Mechanics have actually produced something useful?

The question has most of it in the name. "Useful" may be interpreted as: measurably different from Copenhagen interpretation and true potentially measurably different and potentially true (i.e. not ...
0
votes
1answer
16 views

Dependance of diffusion coefficient on size?

What's the dependance of the diffusion coefficient on size? More explicitly, suppose I have a particles of characteristic length $l$, dissolved in a liquid. How does $D$, the diffusion coefficient of ...

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