-3
votes
0answers
18 views

Precise timing for a meteor impact [on hold]

Do we have the tech to change a meteors path to use the moon as a shield? We may not be able to steer it away but slow or speed it up to hit the moon instead of the Earth?
-1
votes
1answer
51 views

Key Assumption to derive the Uncertainty Principle — Canonical Conjugate Operators [on hold]

From this related question, Rigorous Mathematical Proof of the Uncertainty Principle from First Principles The key assumption to derive the uncertainty principle seems to be the relationship ...
2
votes
1answer
34 views

Extinction level meteor effects on Earth's crust pending on the surface area upon impact

Would it be possible to have a extinction level meteor hit Earth depending on shape to actually create minimal damage if turned on its thinnest area rather than hitting flat? The meteor would enter ...
2
votes
0answers
19 views

Boundary conditions and density when using smoothed particle hydrodynamics/corrective smoothed particle method for two-temperature models

I am trying to solve the dual-hyperbolic two temperature model (TTM) using a modified smoothed particle hydrodynamics (SPH) scheme known as CSPM (corrective smoothed particle method), as demonstrated ...
2
votes
1answer
21 views

Proving the definition of optical throughput

Optical throughout is defined by SPIE as $$\Gamma = \frac{EP\times EW}{S^2}$$ where $EP$ is pupil area, $EW$ is window area, and $S$ is the separation between $EP$ and $EW$. I have not been able to ...
5
votes
2answers
205 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 ...
3
votes
1answer
47 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 ...
2
votes
2answers
65 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 ...
-6
votes
1answer
59 views

Would this ship travel faster than light [on hold]

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 ...
-3
votes
0answers
36 views

Force and dimension is the same? [on hold]

I read somewhere that maybe we have 10 dimensions. We know that we have four dimensions (3 dimensions of space plus one of time). There are also four forces: gravity, electromagnetism, the strong ...
1
vote
1answer
50 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
53 views

Stress-Energy tensor of a static, spherically symmetric, perfect fluid [on hold]

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
1answer
65 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 ...
-3
votes
0answers
27 views

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

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
46 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 ...
16
votes
2answers
881 views

Does fluid speed affect 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 ...
-2
votes
0answers
30 views

Why does depth and height replace volume in this problem? [on hold]

In the following problem, why does H/𝛿 replace V/V? The two ratios have different units. Is there something I'm missing here?
1
vote
0answers
12 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?
17
votes
3answers
5k views

What on Earth is this drawing of Venus?

The Wikipedia article for Venus's alleged moon Neith has this picture: And a tantalizing remark regarding paramecia (vandalism?). I know the grey ball is supposed to be Neith, the white is Venus, ...
-1
votes
0answers
19 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
2answers
96 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
63 views

How does the wave function change upon a boost? [on hold]

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 ...
-1
votes
1answer
74 views

How fast does matter grow more massive when accelerating? [on hold]

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, ...
1
vote
2answers
51 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
votes
0answers
29 views

What will be the new moment of inertia? [on hold]

Let assume we have a sphere of radius $R$, and we can simply calculate the moment of inertia if we consider the axis is going through the center O. Let's cut a sphere small radius $r$ from the sphere ...
1
vote
0answers
40 views

What is a maximally entangled state? Or better, what really is entanglement entropy?

I was trying to understand the concept of entanglement entropy and for that I was studying the density operator formalism in the context of a bipartite quantum system. In some references, people ...
0
votes
0answers
34 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 ...
-3
votes
0answers
37 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,...
1
vote
0answers
35 views

Are all kinds of energy quantized? [duplicate]

I was reading this answer of David Z about meaning of "Quantum" that this question came in mind: If light is quantized (i.e. is a integer multiples of some unit $\hbar c/k$), are other kinds of ...
-2
votes
0answers
32 views

Coordinate determines the speed and thus coordinate [on hold]

I have a question about configuration space. You say that coordinate and momentum have one-to-one correspondence in Quantum Mechanics. Imagine that coordinate of a particle is known absolutely in ...
-4
votes
0answers
68 views

Why isn't CPU made of cesium 133? [on hold]

If this atom can move there and back 9 bilion times per second, then why are we using so poor CPUs?
2
votes
2answers
66 views

The ability to squint and focus - what is it called and is it used in optics? [duplicate]

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 ...
1
vote
1answer
37 views

Single slit diffraction simulation (mathematica) [on hold]

I'm trying to simulate the Fraunhoffer diffraction at slits(single,double,triple) with Mathematica. In the picture, the red one is analytical result and the green one is numerical result. The ...
-2
votes
0answers
28 views

Relative motion of a Boat [on hold]

An boat goes down a river in a velocity of 5 m/s relative to the river.At t=0 the man in the boat sees a bottle going down the river.If boat turn and start to return at t=30min, After how much time ...
2
votes
1answer
54 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 ...
-6
votes
0answers
28 views

the quantity of matter contained in a body is the ______ of the body [on hold]

I didn't understand this on my test I think it was mass
-4
votes
0answers
15 views

waves motion and sound and organ pipes [on hold]

in an open organ pipe whose one end is at x=0, the pressure is expressed by P=P0cos(3pi/2)sin(300(pi)t) where x is in meter and t in sec.then the organ pipe can be- a)closed at one end ,open at ...
6
votes
3answers
71 views

What is the decay width and why is it given in energy units?

I'm reading Thomson, Modern Particle Physics, and in chapter 16 author says that the decay width of the Z boson is $\Gamma_Z =2.452 \pm 0.0023 \,\mathrm{GeV}$. He also says the total width of the ...
3
votes
1answer
48 views

How to make a double slit electron interference as a home experiment? [on hold]

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?
4
votes
2answers
70 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 ...
6
votes
1answer
57 views

What keeps strings in their proper “shape” despite their enormous inherent tension?

Here is an extract from a great answer by Luboš Motl to this question: Tension in Strings Because the string tension is not far from the Planck tension - one Planck energy per one Planck length 10$...
0
votes
0answers
25 views

Explanation of galaxy rotation curves by space-time drag

I expect, that known effect of rotating body (made of galaxy stellar mass) it too small to explain galaxy rotation curves. By how small is it comparing to required value? What if introduce ...
-4
votes
0answers
113 views

A riddle with a physics related answer [on hold]

This question is from this book which has riddles with answers related to physics. I can't seem to get this one. My origins are humble. I started with a couple of people trying to understand ...
1
vote
2answers
37 views

Formula for discontinuity of electric field across boundary

The formula for the discontinuity of the electric field across a boundary is given by$$\vec{E}_{\text{above}} - \vec{E}_{\text{below}} = \frac{\sigma}{\epsilon_0} \hat{n}.$$ In the derivation of this ...
-4
votes
0answers
20 views

Working of Fourier Transform Spectrometer [on hold]

I was planning on doing an experiment using a device called the Fourier Transform Spectrometer. Now, two micrometers fixed to the mirror mount allow M1 to be tilted horizontally and vertically and a ...
0
votes
1answer
49 views

What is the process of a photon transforming into an electron and positron? [duplicate]

How did they come into existence from a photon? Is it really understood how the process works? Is there even a process or is it just something fundamental?
-1
votes
1answer
42 views

What are our electron production capabilities? [on hold]

What is our capability to produce electron beams now? Eg. is there a portable device that can generate electron beam at a large production rate? In a gas phase.
2
votes
1answer
82 views

A question about Kaluza-Klein mechanism

We know that there is a kind of compactification mechanism named Kaluza-Klein theory which states that the extra dimensions can be compacted dimensions such as $T^n$ or $S^n$ and so on. To make the ...
2
votes
3answers
79 views

Length Contraction in Relativity

Let's suppose we have a one dimensional rod made of elementary point particles, in contact with each other placed along the x-axis.If the rod is moving along x-axis then we know (because of relativity)...
-2
votes
1answer
43 views

Minimum and Maximum Speeds of a Mass [on hold]

I understand that it is impossible for a object with rest mass to travel at $c$ (the speed of light) due to time limitations. I also understand that the speed of an object is calculated using a frame ...

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