-4
votes
1answer
34 views

Would this ship travel faster than light

Im curious about using a geometric thruster system to break the speed of light barrier, Using a system of beams that rotate along alternating axis' from either end of themselves so as to travel a ...
0
votes
0answers
4 views

Boundary conditions and density when using SPH/CSPM for two-temperature models

I am cross posting the question here from SciComp stackexchange with extra pictures since I believe it is on topic for both websites and does not deal with the code itself or optimizing it at all. If ...
-7
votes
0answers
17 views

Can one shed light on the velocity of the photon through the fourth dimension x4 using limits? [duplicate]

THIS QUESTION IS COMPLETELY DIFFERENT!! IT DISCUSSES LIMITS!! To begin with, please study the mathematics from Brian Greene’s book An Elegant Universe. The upshot is that the faster an object moves ...
6
votes
1answer
125 views

Does fluid speed matter in liquid cooling?

If you have a liquid-based cooling system, like the loop in the picture below, does the fluid speed actually matter? I can see how cycling the liquid too slowly would be bad, since the fluid would be ...
0
votes
1answer
115 views

single slit diffraction - $\sin\theta=n(\lambda)/b $ or $\sin\theta = (2n+1)(\lambda)/b$

I'm getting a contradiction as follows and am not sure how to resolve it: logic 1 leads to the conclusion that the higher order minimas of single slit diffraction will be given by $b\sin\theta = n(\...
5
votes
1answer
56 views

Which charge to use in the Dirac quantization condition?

I have a follow-up question to Dirac magnetic monopoles and quark fractional electric charge quantization, regarding whether the "unit of electric charge" in the Dirac quantization condition should be ...
3
votes
1answer
19 views

Alkali metal transparent to UV - is cesium (somewhat) transparent to visible blue light?

Most optics texts will mention that alkali metals can become transparent in the near ultraviolet in the sections on reflections from metals, plasma frequency, and electron density. I remembered this ...
1
vote
2answers
50 views

Gravitational Strength on a theoretical flat planet

Ok, so let me clarify: a planet that overcame all structural problems with being planetary size, I.E. collapsing into a ball. What would be the gravitational strength on a flat planet with the ...
0
votes
0answers
6 views

Optics: Optical Throughput and Entrance Windows

This is a two part question: 1) Optical throughout is defined by SPIE https://spie.org/publications/tt48_27_throughput. I have not been able to geometrically prove this relationship and was looking ...
-3
votes
0answers
31 views

Compensating Parallax problem of a washing machine's drum [on hold]

We would know how it is possible inside a washing machine, when the drum is full with garments, so it is very heavy, to compensate, when the drum is rotating at high speed for the parallax of rotation,...
3
votes
1answer
24 views

Is ergodic hypothesis in contradiction with the notion of equilibrium?

From wikipedia: In physics and thermodynamics, the ergodic hypothesis1 says that, over long periods of time, the time spent by a system in some region of the phase space of microstates with the ...
0
votes
1answer
17 views

Can we exit the event horizon of merging black holes?

I have an intuitive scenario. Consider we have a spaceship just below the event horizon of a BH, which is merging with another black hole. Finally, the singularities merge and we have a single black ...
1
vote
1answer
17 views

Spontaneous symmetry breaking of gauge symmetry in 1+1 dimensions?

The Mermin-Wagner theorem states that continuous global symmetries cannot be broken in two or fewer spacetime dimensions; however, I have not seen this statement applied to gauge theories. Does it ...
5
votes
3answers
575 views

What on Earth is this drawing of Venus?

The Wikipedia article for Venus's alleged moon has this picture: And a tantalizing remark regarding paramecia (vandalism?). I know the grey ball is supposed to be Neith, the white is Venus, the ...
8
votes
3answers
2k views

What is a completely positive map *physically*?

I am sure this question is really stupid, but I could not refrain from asking it in this forum. This can be considered as a continuation of this question. ...
2
votes
1answer
26 views

Chemical Potential of Interacting Particles

I'm interested in studying the diffusion of (classical) particles that have some interaction with each other. More specifically, let the potential energy of any two of particles separated by a ...
2
votes
1answer
141 views

Thermionic emission, delayed emission and predissociation

In molecular photodissociation, the thermionic emission, delayed emission and predissociation are the same? Otherwise, what is the difference between them? My question is not about the solids, but I ...
2
votes
1answer
28 views

Is the use of term Measurement appropriate in quantum physics

It may not sound like a physics question, but I think, it is. When we measure spin of an electron in a certain direction, we are actually, setting it up in that direction. That does not sound like ...
111
votes
3answers
6k views

Why are the harmonics of a piano tone not multiples of the base frequency?

I was trying to figure out which piano keys were being played in an audio recording using spectral analysis, and I noticed that the harmonics are not integer multiple of the base note. What is the ...
-4
votes
0answers
24 views

Force and dimension is the same? [on hold]

I read somewhere that maybe we have 10 dimension The force ? Gravity, electromagnetic, and the other 2 is the same as the dimension in the universe Thanks
0
votes
1answer
39 views

What would be the masses of the elemental particles if the Higgs field had a different value?

Afaik there is some function, for example, for the mass of the electron $m_e(\phi_1, \phi_2, \phi_3, \phi_4)= ...$, and similarly to the other elemental particles. (Here the $\phi_{1..4}$ are the ...
1
vote
2answers
452 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
1
vote
0answers
23 views

Why is black hole entropy not an extensive quantity?

The Bekenstein entropy for a black hole is proportional to the surface area $A$ of the black hole $$ S_{BH} = \frac{k_B}{4 l_P} A $$ with the Planck length $l_P = \sqrt{\frac{\hbar G}{c^3}}$. The ...
0
votes
0answers
20 views

Stress-Energy tensor of a static, spherically symmetric, perfect fluid

I am trying to derive the equation for the interior mass of a spherically symmetric, static, perfect fluid in general relativity, $$\frac{\mathop{dM}}{\mathop{dr}} = 4\pi r^2 \rho(r).$$ This question ...
2
votes
5answers
87 views

Is perfect thermal insulation possible?

Supposing someone says they have a sample of insulanium with the following properties: If you make a thermos out of insulanium, it will keep a drink hot or cold forever. If you put your hand on a ...
0
votes
1answer
18 views

Does the electron energy-deposition profile exhibit a Bragg peak?

The energy deposition profile of an electron beam impacting a material has this characteristic shape ($1~\mathrm{MeV}$ beam in solid Cu):* What physics mechanism would refer to the peak energy ...
2
votes
1answer
133 views

How to calculate impulse force of body hitting water?

I'm calculating the force of a body hitting water from a high height. So far I've figured out the velocity at the time of collisions would be 40 m/s. The body is 78 kg. I seem to need the time it ...
4
votes
2answers
630 views

Can 3 photons be combined to give a spin-0 projection?

Motivation: The neutral pion decays to 2 photons ($\pi^0\to\gamma\gamma$) most of the time. For the decay of the neutral to 3 photons ($\pi^0\to 3\gamma$) we have an upper limit on the branching ...
-2
votes
0answers
19 views

Why was the formula (1/3)mL^2(α) used in this problem?

I can't tell where this equation is from. Is it the moment of inertia for a rod? If so, it doesn't say so in my physics book. Help please?
-2
votes
1answer
34 views

Some perspective on two slits

I am not a physicist but i enjoyed the subject as a hobby and have my formal education in the field of computer science. If any of what follows is a big flaw in my understanding, I hope it will be ...
2
votes
2answers
67 views

Express state as eigenkets

This is very basic but I just suddenly got confused. Any state can be expressed as complete set of eigenkets with discrete eigenvalues: $$|P\rangle = \sum^n c_n |p_n\rangle$$ I understand the above. ...
2
votes
1answer
147 views

What is the metric of a constant electromagnetic (pure electric or pure magnetic) field?

For example, imagine a magnetic field $B_x$ directing in $\hat{x}$ direction filling all the space. What is its associated metric field? I can construct the electromagnetic stress-energy tensor for ...
2
votes
1answer
46 views

Relationship between position and momentum matrix elements

I am going through Faist's Quantum Cascade Lasers book. In the first section of the fourth chapter, he asserts that (in the context of a perturbative analysis of electronic transitions) the ...
-2
votes
0answers
28 views

Why does depth and height replace volume in this problem?

In the following problem, why does H/𝛿 replace V/V? The two ratios have different units. Is there something I'm missing here?
2
votes
2answers
51 views

The ability to squint and focus - what is it called and why is it used in optics?

Most people that wear glasses or contacts can squint to reduce the blurriness of their vision. How can this be explained, and has it ever been used in optics to enhance the focus or clarity of an ...
3
votes
2answers
121 views

Fluorescence and phosphorescence

Fluorescence is where UV light is absorbed then emits visible light right? Is it that you can only see it in the dark whereas phosphorescence is where UV light is absorbed and visible light is ...
-1
votes
1answer
60 views

How fast does matter grow more massive when accelerating?

I am wondering since it is understood that mass of matter increases as its velocity increases, how fast does this process occur if it is a physical process? For instance, if a mass initially at rest, ...
0
votes
2answers
41 views

Use of $g$ for centripetal acceleration

I have attached an image above including the question I'm unsure of (part B) In a nutshell, a satellite is orbiting Earth at the surface. Given is $g$ and the radius of the Earth. For part bi) the ...
1
vote
0answers
6 views

How does the MSSM pseudo-scalar heavy Higgs undergo the decay process A -> Z h?

As A is a pseudo-scalar, Z an axial vector and h being a scalar, it looks like the spins are not balanced on both sides. Is it related to the longitudinal mode of Z boson?
3
votes
1answer
635 views

Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
25
votes
14answers
71k views

I don't understand what we really mean by voltage drop

This post is my best effort to seek assistance on a topic which is quite vague to me, so that I am struggling to formulate my questions. I hope that someone will be able to figure out what it is I'm ...
0
votes
0answers
52 views

What is the expression for a Lorentz invariant wave function?

I was recently thinking about Lorentz invariance description of a particle. In special relativity is based on the invariance of $$ \text{constant} = c^2t^2 - x^2 - y^2 - z^2$$ I was wondering if ...
2
votes
1answer
67 views

What kind of effect would cosmic expansion have on planetary motion or keplerian orbit?

The question is, if two following phenomena are thought to effect to the motion of the planet that orbits a star: Celestial body is pulled by some massive star by ordinary Newtonian gravity: $$ m \...
1
vote
2answers
53 views

Question regarding elastic collisions and the conservation of momentum / energy [on hold]

I've been working on this question for a few hours and I cannot quite convince myself that my answer is correct. I've read the relevant section in my textbook, but I guess the lightbulb just isn't ...
-1
votes
0answers
17 views

Thermal radiation [on hold]

The emissivity of a hemi-sphere varies as: $$ e=E\cos\theta$$ What is the ratio of emissive energy between the given sphere and a normal black body sphere.
3
votes
1answer
45 views

How to make a double slit electron interference as a home experiment?

I want to see electron interference making my own experimental equipments. Do you think it is possible? Especially, double slit, how can I have it?
5
votes
0answers
68 views

Why do these experiments contradict the accepted theory about puddles? (+ my work)

A few months ago, I tried to tackle the problem of finding the shape, the height and other properties of a puddle (whenever a few mL of some liquid are dropped in a "uniform way" so that the puddle ...
0
votes
0answers
33 views

Why can the y and z-components of spin be measured simultaneously? [duplicate]

I have a gut feeling that this is wrong. By the uncertainty principle where $x,y,z$ are the $x,y,z$ components of spin $$ \sigma_{y}\sigma_{z}\geq \frac{\hbar}{2}\langle x \rangle $$ and it can be ...
0
votes
0answers
19 views

Proof of Exponential Decay Behavior of Time Correlation Functions

For a given protein, I know that the NMR Spectroscopy magnet generates a field $\mathrm{B_o}$ and that the interactions with the spins in the local environment generates a much smaller field $\mathrm{...
4
votes
2answers
62 views

If orbital shells are just probability functions, why are quantum numbers only ever integers? [on hold]

Quantum numbers are supposed to denote every individual orbital. But if orbital shells are probability functions, then orbitals can't be definite, solid things. So in that case, there can be variation ...

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