3
votes
1answer
64 views

Are temperature increases discrete? [duplicate]

Are temperature increases ever discrete in nature, or is it a continuous variable? If a discrete case exists, is there any material that exhibits particularly strange behavior?
1
vote
1answer
30 views

Total multiplicity and entropy of Einstein solids

This is really a question to get a little more insight about a homework exercise. 1. In my text book, the sum of multiplicities for all possible macrostates is given to be: $$\sum ...
0
votes
2answers
106 views

Drift Speed and Current in Two Different Inertial Frames

We have a long, cylindrical wire carrying a constant current I in an inertial frame. At a distance of R from the center of the wire, the magnitude of magnetic field is $μI/2πR$. What is the magnitude ...
1
vote
1answer
58 views

Feynman Lectures: Trigonometry Error in Rotational Dynamics?

I'm reading through Vol. 1 Chaper 18, and Feynman says that in the system: (See here for a higher resolution copy - can't embed SVGs), the length of $PQ$ is equal to $r\Delta\theta$: If $OP$ is ...
15
votes
3answers
2k views

Explanation for this type of (magic-trick) suspension? [on hold]

Well let's start off with that I'm not a physicist but I'd like some thoughts on something I came across in my hometown. This guy: Is it possible that due to the electrical charge of magnets this ...
1
vote
1answer
32 views

Pushing a crate on a friction floor [on hold]

A man is pushing a crate at a constant velocity. there is a friction between the floor and the crate of $$\mu =0.41.$$ The pushing force is directed downward at an angle $\theta $ below the ...
1
vote
1answer
52 views

Choice of sign of exponential argument affecting tractability of wave reflection at a boundary

It is possible to show that functions of the form $f_{1}(kx-\omega t)$, $g_{1}(kx+\omega t)$, $f_{2}(\omega t-kx)$ and $g_{2}(\omega t+kx)$ are all solutions of the wave equation ...
39
votes
5answers
4k views

How literally should you take “The Higgs boson gives other particles mass”?

A standard phrase in popular discussions of the Higgs boson is that "it gives particles mass". To what extent is this a reasonable, pop-science, level of description of the Higgs boson and it's ...
1
vote
3answers
106 views
+50

Extracting heat energy without a heat engine

Is it possible to extract the molecular kinetic energy from a system directly (without the use of a heat engine / temperature gradient) and convert that to another form of energy, such as electricity, ...
0
votes
1answer
364 views

Distinguish between instantaneous speed and instantaneous velocity

I encountered a line in my text book of physics that: Average speed over a finite interval of time is greater or equal to the magnitude of the average velocity. But instantaneous speed at an ...
2
votes
1answer
103 views

about field gradient

I read the term field gradient in most of the article about magnetic field. I search it online but most of the explanation is about the math. I wonder in physics, what the gradient field really mean? ...
2
votes
1answer
366 views

Theoretical power limit of nuclear bomb

Is there any limits of power or power to mass (or any other) limits for nuclear bombs? I found this wiki article: Nuclear weapon yield: Yield limits. Is the information provided is correct? If yes, ...
11
votes
2answers
1k views

How fast would a spaceship have to go to reach Alpha Centauri within a person's lifetime?

Given the recent news about the discovery of an "Earthlike" planet orbiting Alpha Centauri (our nearest stellar neighbour) it got me wondering just how fast would spaceship have to travel to be able ...
0
votes
4answers
374 views

Mass-Energy relation

Einstein mass- energy relation states $E=mc^2$. It means if energy of a paricle increases then mass also increases or vice-versa. My question is that what is the actual meaning of the statement ...
2
votes
1answer
85 views

How exactly and WHY does matter affect space-time? [on hold]

According to general relativity, inertial mass and gravitational mass are the same, and all accelerated reference frames (such as a uniformly rotating reference frame with its proper time dilation) ...
0
votes
4answers
114 views

Visualisation of formation of electromagnetic waves [duplicate]

Recently I am studying electromagnetic waves, and I am wondering why it is formed by acceleration of electric charges? Can the EM waves be formed by other movements of electric charges, such as at a ...
0
votes
2answers
19 views

Extract particular ions from an ionized gas

Is it possible to extract any particular ion ( either positive or negative ) from ionized gas ( or plasma ) without spending any ...
3
votes
0answers
37 views

How can one explain gravitational time dilation in non-rotating bodies? [on hold]

A clock on the surface of the Earth (assuming it does not rotate) will accumulate around 0.0219 seconds less than a distant observer over a period of one year (assuming the observer is using ...
1
vote
1answer
116 views

Question about supercooling

During the cooling of a liquid, if no impurity of site of nuclearation, an appreciable solidification will begin only after the temperature has been lowered to below the equilibrium solidification (or ...
55
votes
6answers
5k views

Which way does the scale tip?

I found the problem described in the attached picture on the internet. In the comment sections there were two opposing solutions. So it made me wonder which of those would be the actual solution. So ...
1
vote
1answer
289 views

If we have a current $I$ flowing down a wire, why must the net bound current be zero?

Say we are dealing with a wire that has a current $I$ flowing through it, i.e. $I$ is the free current. Why must it then hold that the net bound current, that is, the bound volume current, $J_b$, and ...
0
votes
1answer
54 views

How can I boost the FM reception of a smartphone? [on hold]

How can I improve the FM reception on my Nokia smartphone? I have tried by removing the insulation on earphone wires and connecting the earphone wires to another wire placed high on roof but it has ...
1
vote
2answers
39 views

Quantum Eraser thought experiment with light photons of distinct color

I tried to recreate the Quantum Eraser experiment into a thought experiment with a few changes. It left me a little perplexed as to what outcomes I should expect. Any help would be appreciated. Lets ...
0
votes
1answer
25 views

Polarization selection rules

So, I am just reviewing some of my physics stuff, and I have read something about polarization selection rules in inter-band-transitions in quantum wells. If I calculate them, I get a strength of 1/2 ...
3
votes
2answers
58 views

Alcubierre drive and inertia.

What is the inertia or velocity of a vehicle upon exiting or shutting down an Alcubierre bubble? Would the vehicle maintain the velocity it had in the bubble? I'm not sure I asked the question in a ...
14
votes
2answers
1k views

How does one experimentally determine chirality, helicity, spin and angular momentum?

If I've got an instance of a fundamental particle, how can I separate out the measurements of these three concepts? (I think) I understand the theory behind them, and why the particles in the ...
0
votes
0answers
26 views

How can a paper battery behave like a capacitor?

I was trying to understand how paper batteries work and came across some explanations saying that the paper battery can also behave like a supercapacitor on account of its ability to discharge and to ...
0
votes
2answers
66 views

How damaging is light?

On Surely You're Joking Mr Feynman, when talking about the Trinity test, the author states: the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet ...
2
votes
0answers
26 views

How do gauginos and scalars gain masses after gauge-mediated symmetry breaking?

In the minimal-GMSB model, the messenger fields transform under the MSSM gauge group and connect a so-called hidden sector to the visible sector. These meesenger fields (left-handed chiral ...
1
vote
0answers
40 views

The states of the adjoint representation correspond to the generators

I understand the definition of the adjoint representation. It uses structure constants as matrix components of generators, but I can't understand meaning of the states $|X_{a}\rangle$. What does ...
5
votes
1answer
154 views

Real World measurements related to phonon dispersion

I hope no one objects to the style of this question. Let me explain my motives in asking the question first. Condensed matter physics is one of the most beautiful subjects around. But those who are ...
13
votes
4answers
1k views

Are voltages discrete when we zoom in enough

Voltages are often thought of as continuous physical quantities. I was wondering whether by zooming in a lot, they are discrete. Can all voltages (potential differences) that exist in reality be ...
2
votes
1answer
442 views

How to solve bound states of 2D finite rectangular square well?

I want to solve bound states (in fact only base state is needed) of time-independent Schrodinger equation with a 2D finite rectangular square well \begin{equation}V(x,y)=\cases{0,&$ |x|\le a ...
0
votes
1answer
30 views

Drawing Ray diagrams

When drawing ray diagrams for concave mirrors, I was advised to : draw a ray that is parallel to the principle axis, the reflected ray will pass through the focus Draw a ray through the center (C), ...
1
vote
4answers
93 views

Can you explain Fermat's Principle to me?

The textbook(F.A.Jenkins and H.E.White Fundamentals of Optics) states that the Fermat's principle is that the path taken by a light ray in going from one point to another through any set of media ...
0
votes
1answer
27 views

How to understand “the speed of propagation of the condition of constant phase”?

I still can't understand that the phase can be a constant until now. If the phase is constant, from the $$y(x,t) = a \times \sin(phase)$$ the shape of wave will be a line parallel to x-axis.But I ...
1
vote
1answer
34 views

Blazars and nuclear physics!

How are studies on blazars related to the field of nuclear physics? Should these not purely belong to Astrophysics? Just inquisitive.
0
votes
0answers
13 views

Longitudinal and transverse direction for a T-Section? [on hold]

Normally, we say that the direction perpendicular to the working direction is the transverse direction and the direction along the length of the material is the longitudinal direction. What is the ...
2
votes
2answers
110 views

Is time nothing but the speed of light (or the light itself)?

With regard to relativistic effects on time, all the examples and explanations revolve around light and its speed. Especially in explanatory situations that explain this using photon clock, it seems ...
0
votes
2answers
65 views

Physical interpretation of initial conditions for damped mass-spring system

I have background in pure mathematics so my question is about physical meaning. If we consider equation for damped mass-spring system, it is linear ordinary second order differential equation. So to ...
0
votes
0answers
19 views

Determine particle velocity from density function

I'm modeling a 1D system which consists of a large number of discrete particles distributed on a line. As a continuous approximation, I'm defining $c(x,t)$ to be the space density function of these ...
11
votes
3answers
730 views

Is “now” or “the present moment” properly defined in GR?

My question is about the extent to which "now" is defined in GR. In Minkowski spacetime, it's possible to define a "now" for an inertial observer by finding a spacelike 3-plane such that, in the ...
0
votes
1answer
27 views

Is something beyond the material needed to solve the Von Neumann Chain?

A problem has been presented that goes like this: Particles normally exist as several mathematical possibilities rather than one actual object. It is said that in the absence of observation, ...
0
votes
1answer
383 views

Proof of equality of the integral and differential form of Maxwell's equation

Just curious, can anyone show how the integral and differential form of Maxwell's equation is equivalent? (While it is conceptually obvious, I am thinking rigorous mathematical proof may be useful in ...
2
votes
4answers
359 views

Are Lagrangians and Hamiltonians used by Engineers?

Analytical Mechanics (Lagrangian and Hamiltonian) are useful in Physics (e.g. in Quantum Mechanics) but are they also used in application, by engineers? For example, are they used in designing bridges ...
2
votes
2answers
3k views

What happens when you cut a biconvex lens in half?

Specifically, does the focal length change? How can this be rationalized?
1
vote
1answer
92 views

Is carrier charge density and carrier mobility constant in a given material?

If we assume the semi-conductor is doped by a variable amount, is there some way I can look up carrier charge density for the material in a reference somewhere? What about carrier mobility?
3
votes
1answer
28 views

Bondi-Metzner-Sachs (BMS) symmetry of asymptotically flat space-times

I started studying the BMS symmetry in connection with the paper: http://arxiv.org/abs/1312.2229 and there are a few strange things I noticed. First of all, from reading the original papers by Bondi, ...
1
vote
3answers
101 views

Do photons interact only with single particles or can a single photon be absorbed by 2 or more particles simultaneously?

Say I have 100 particles in a vacuum that are spread out such that their movement caused by a time variant electromagnetic field does not have an effect on each other. That is the particles can not ...
0
votes
0answers
35 views

A very confusing question about retaining light and using it as propulsion… [on hold]

I'm gonna get things wrong, probably... but I have a question. If I encapsulate an aerogel with a powerful photophor without photons escaping or dissipating, (here is where it gets confusing.) Will I ...

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