5
votes
1answer
64 views

Capture reflecting image

Suppose you have following installation: ...
1
vote
3answers
230 views

What does the decay constant mean?

In my curriculum, the decay constant is "the probability of decay per unit time" To me, this seems non-sensical, as the decay constant can be greater than one, which would imply that a particle has a ...
5
votes
2answers
138 views

Inexact measurement and wavefunction collapse

As is usually said, measurement of an observable $q$ leads to collapse of wavefunction to an eigenstate of the corresponding operator $\hat q$. That is, now the wavefunction in $q$ representation is ...
0
votes
0answers
63 views

Would a cone shaped Stirling engine work?

A Stirling engine evidently functions by heating and cooling air, thus making the piston move up and down. What if the heated side of the cylinder were shaped as a sort of cone with a gentle slope, ...
0
votes
1answer
404 views

How fast does the water travel down river when the discharge gates of a large dam are opened?

How fast does the water travel down river when the discharge gates of a large dam are opened? Can the discharge-wave travel downstream faster than the water? Is this likely to occur for a real river ...
1
vote
1answer
209 views

Calculate Hamiltonian from Lagrangian for electromagnetic field

I am unable to derive the Hamiltonian for the electromagnetic field, starting out with the Lagrangian $$ \mathcal{L}=-\frac{1}{4}F^{\mu\nu}F_{\mu\nu}-\frac{1}{2}\partial_\nu A^\nu \partial_\mu A^\mu ...
0
votes
3answers
199 views

Why does a wavefunction collapse when observation takes place?

Why does a wavefunction collapse when observation takes place? Can this question be explained in non mathematical terms? I have tried finding the answer but couldn't find a clear explanation.
0
votes
1answer
111 views

Moment of weight of leaning beam

Having trouble with a FBD moment. The problem is: How big can the force couple C (looks like a G in the pic) be in order for the disk to not spin? The disc has mass m and the beam also has mass ...
0
votes
0answers
48 views

General relativity && quantum mechanics “incompatibillity” [duplicate]

Now this may be utterly weird layman-physics-question, but anyways... I have read recently following: "The fundamental universe laws are everywhere the same. It's just that the manifestation (!) of ...
1
vote
3answers
210 views

What makes matter travel along geodesics?

The relativistic explanation of gravity is geometric, the motion of a body in a field of space-time distortion can be described as being at rest and travelling along a geodesic of that field, but why ...
3
votes
1answer
81 views

Where did the energy come from?

Suppose there are two slopes. Imagine its just small slope and can be placed on your floor. One slope is made of a very smooth material and another which provides a lot of friction for example made ...
3
votes
2answers
184 views

Lorentzian and Einstein Manifold

I am studying for my Bachelor thesis (in Mathematics). I and my advisor agreed on the Penrose-Hawking singularity theorems. My question is: 1) Which mathematical background should I focus on ...
0
votes
0answers
23 views

Electromagnet emitting light [duplicate]

We all know that (visible for human) light essentially is an electromagnetic wave with a frequency around 1/((any value between 380 and 760)*pow(10,9)) Hertz. So, if we will build (hypothetically) ...
3
votes
3answers
179 views

Bound States clarification

Our professor hasn't explained what bound states are. Could you give me an idea of what they mean and their importance in quantum-mechanics problems with potential (e.g. a potential described by a ...
0
votes
2answers
142 views

Could the Earth have a dark matter core as well as a disk?

If it is established that the Earth does have a dark matter disk as this recent discovery suggests. ...
0
votes
0answers
60 views

periodicity of diffraction gratings

Imagine we have a diffraction grating consisting of N slits (being N very large) with a separation of "d" from slit to slit. Now, we could regard this grating as a diffraction grating constructed by ...
3
votes
2answers
535 views

Wave function with a delta potential

I have a particle and a potential $V(x)=\frac{\hbar^2}{2m}k\delta(x)$. Where $\delta (x)$ is the Delta function, and I am interested in the solutions of the stationary Schroedinger equation. If ...
0
votes
0answers
34 views

What is highest temperature which is attainable? [duplicate]

We all know that there is a limit to the lowest temperature which can be achieved i.e. $0K$. But I wanted to know if there is a limit to the highest temperature which can be attained. And if there is ...
3
votes
1answer
65 views

What is the need to consider a singular spacetime?

To have a consistent superstring theory (which is to avoid the conformal anomaly on the worldsheet CFT) we are forced to build our theory on the critical dimension $n=10$. However, the Standard ...
2
votes
1answer
68 views

How does a gauge theory probe a spacetime singularity?

Within the framework of string theory, I have read in numerous articles such as the introduction of this this in which it is stated that the gauge theories living on a stack of D-branes can be used to ...
1
vote
1answer
128 views

Why Gauss' law is applied?

Why Gauss' law is applied? Why is there a need of finding electric field by Gauss' law if we can find the electric field through Coulomb's law? or has it got more applications than Coulomb's law?
1
vote
1answer
566 views

Problem with ring-method of du Nouy for calculating surface tension

I need to calculate the surface tension of a liquid with the ring-method of du Nouy and the correct formula to use is: $\gamma = \frac{F}{4\pi R}$ I understand that the surface tension is the ...
1
vote
2answers
77 views

Gravitational lensing image from merging black holes

What kind of image would a transcient toroidial black hole merger produce from it's gravitalional lensing effect? http://arxiv.org/abs/gr-qc/9905039 What does a torus shaped lens actually look like? ...
1
vote
1answer
61 views

Is there a physical system that emulates mathematical cellular automata?

Theoretical cellular automata have been proposed as models for many physical phenomena from music to quantum mechanics. My question concerns the reverse: Is there a simple physical system that ...
3
votes
0answers
134 views

Reducing massive representation of the Poincare group to the massless one

I want to ask about the connection for massive and massless representation of the Poincare group. Sorry for the awkwardness. First I must to represent the formalism for both of cases. Massive ...
0
votes
2answers
72 views

Finding the value of velocity $u$ [closed]

A block of mass $m$ is pushed towards a moveable wedge of mass $\eta m$ and height $h$, with a velocity $u$. All surfaces are smooth. The minimum value of $u$ for which the block will reach the top of ...
2
votes
2answers
186 views

Superconductivity: why can't the resistance reach 0?

When we study electricity in high school we examine the resistance of conductors and its relation with temperature. Diagrams show the relationship at the beginning is pretty much a linear with ...
2
votes
1answer
203 views

Energy and time evolution of a particle in a potential well

Hoping this is not a silly and stupid question let me ask for help in this problem. I have a particle in an infinite square well (the box is from 0 to a), in the state described by the function ...
0
votes
2answers
134 views

What would happen if an incredibly high energy photon passed through a human body?

What would happen if an incredibly high energy photon passed through a human body (or any other material)? When I say incredibly high energy photon, I mean higher than any known energy scales... ...
3
votes
1answer
97 views

What if the kinetic energy of a particle was some other function $f(v)$?

This is a "what if this was how the universe worked" kind of question. I don't know if those belong in Physics StackExchange, and I apologize if they don't. Suppose we have two reference frames ...
2
votes
0answers
116 views

Translational and Rotational Energy in Special Relativity

In non-relativistic classical mechanics: $$\tag{1} \begin{eqnarray} \text{KE}&=&\frac{1}{2}\sum_i m_i v_i^2=\frac{1}{2}\sum_i m_i (\vec{v}_{cm}+\vec{v}_{i,rel})^2 \\ ...
3
votes
2answers
134 views

Most particles that have ever been modeled

Two billiard balls collide. Consider the two balls only, how many particles are in that system? Have particle systems of that size been modeled with each individual particle before? What is the ...
2
votes
1answer
133 views

Where is a closed form also exact?

I'm not very familiar with exterior derivatives. I've some trouble following argument (which is a part of a proof that if the Riemann tensor vanishes, $R^{\,\rho}_{\;\,\sigma \mu \nu}=0$, iff there ...
1
vote
1answer
194 views

Foucault pendulum explanation, rotating earth or rotating universe?

If we start from the assumption that all frames of reference are valid for describing motion, how can a foucault pendulum either prove or disprove that the earth rotates or is stationary? Couldn't ...
0
votes
1answer
495 views

holographic projection in thin air?

from where I come from ,they taught us in high school that it is possible to project holograms in thin air simply by illuminating the hologram with the "correct light" , and having a semi transparent ...
0
votes
2answers
154 views

Paradox Regarding Time Dilation at the Speed of Light

Consider the following scenario: On earth, I pulse a laser focused at a far away mirror such that the time it takes for the light to reflect off the mirror and arrive back at me is at least a few ...
0
votes
1answer
831 views

Photons and phonons

A few months ago I asked about phonons. I got some very good answers but I still have difficulty getting an intuition for phonons, while somehow photons, which in many ways are similar and which I ...
8
votes
3answers
246 views

Do two photons traveling in opposite directions emit gravitational waves?

Do two photons traveling in opposite directions emit gravitational waves? If so, does it mean that any volume filled with photon gas will eventually degrade into graviton gas? In other words, if flat ...
1
vote
3answers
294 views

Why Sun light can reach us if Time is dilating?

I understand that if something is moving with constant speed in respect to an observer, the time of the moving one runs slower, so the more your speed is, the more your time ticks slower. Which ...
3
votes
1answer
211 views

Question about gravity in 1 dimension

Consider 2 pointmasses in 1D space. More specific ; object $A$ with mass $m_a$ and object $B$ with mass $m_b$. $A$ and $B$ are a distance $d$ away from eachother. Let these pointmasses $A,B$ have no ...
0
votes
1answer
42 views

Is there a probability that an electron in an atom change its energy level due to emitting gravitational wave?

Is there a probability that an electron in an atom change its orbital by emitting a quantum of gravitational radiation instead of photon?
0
votes
2answers
117 views

Why doesn't a particle's velocity effect the strength exerted on it by an electric field?

Here is what I know: $F = E q = m a$ so $a = \frac{E q}{ m}$ and we can increase the acceleration ($a$) of a particle in an electric field ($E$) by either decreasing its mass ($m$) or ...
0
votes
1answer
62 views

Spreading heat with water

If water is cycled through a thin pipe by a pump, and a certain spot on that pump is made of thin copper that is being heated by a 1000 C source, will the water, as a whole, attain a heat of 1000 C ...
4
votes
0answers
104 views

One more time about Nordstrom theory

Wikipedia says that Nordstrom theory with equations of motion of the test particle $$\tag{1} \frac{d (\varphi u_{\alpha})}{d \tau} = \partial_{\alpha} \varphi $$ and field equation $$\tag{2} \varphi ...
2
votes
0answers
48 views

What speed should have an alone planet to have a habitable zone due to relic radiation?

What speed should have an alone planet to have a habitable zone due to relic radiation, without any star involvement? How much time the planet will be able to remain in the habitable zone before the ...
1
vote
1answer
293 views

Partially polarized light with jones vectors?

I have read that polarized light is treated by Jones vectors and that to treat partially polarized light you have to use Stokes vectors and mueller matrices. Nonetheless, the optics notes that my ...
0
votes
0answers
108 views

Off-shell corrections to massive vector boson propagator in polarization form

As an exercise for myself, I have been working on rewriting the massive vector boson propagator (unitary gauge). I have run into a problem interpreting some of the terms that stick around when the ...
7
votes
5answers
2k views

Trouble with classical mechanics self-learning (How to avoid going down the Physics rabbit hole?) [duplicate]

I'm a retired police officer trying to learn classical mechanics on my own. I have gone through many links on the Internet including the classical mechanics quick reference textbooks from Physics ...
1
vote
2answers
74 views

Irradiance at surface point due to lighting from point light source

I'm reading through a computer graphics paper and author says that the radiant intensity emitted by an infinitely small surface point $p$ with normal $ n $ into direction $ \omega $ is $$ I_p(\omega) ...
0
votes
0answers
60 views

Torque-free Precession of a Barbell

I'm looking at torque-free precession, occurring when the angular velocity isn't aligned with a principal axis of an object. I've looked at some Euler arguments, some decompositions of $\vec{\omega}$ ...

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