0
votes
4answers
2k views

Why do high current conductors heat up a lot more than high voltage conductors?

120 volts x 20 amps = 2,400 Watts However, if I increased the voltage and lowered the current, you can also use a smaller wire size (more inexpensive), also have less heat and achieve the same watt ...
1
vote
1answer
506 views

Spin eigenvalues and eigenvectors problem. Is this the correct way to solve it?

An electron is described by the Hamiltonian $ H=\frac{e}{mc}\bar{S}\cdot\bar{B} $ where $\bar{S} =(S_x,S_y,S_z)$ is the spin operator and $\bar{B}$ the magnetic field. For $t>0$ ...
0
votes
2answers
409 views

Do photons see shorter distances due to space contraction?

I may be wrong, but this is just what I've heard. People often talk about what would happen if we, humans, were able to make a spaceship travel at the speed of light. If I'm not mistaken, then we ...
1
vote
0answers
98 views

While falling into a black hole, what color would the flashlight have?

If, hypothetically, me and my rocket powered flashlight were falling straight toward the center of a black hole. The flashlight is a few kilometers behind me in our travels toward the center of the ...
1
vote
0answers
56 views

How does the Planck length hold true? [duplicate]

If there is a length which no object can breach in terms of the smallest of size, how can that length hold true? Our earth is undoubtedly considered the Planck length to some monolithic planet out ...
2
votes
0answers
756 views

What is the minimum physical distance between two electrons?

If electrons repel, then it seems to me that energy is required to decrease the distance between two electrons. Since energy and mass are equivalent, adding energy to a system also adds some mass. ...
10
votes
2answers
224 views

How strong is electron degeneracy pressure?

I'm trying to get some specific numbers for electron degeneracy that I can understand, using a concrete example. Take for example this portion of carbon crystal: Exactly how much energy would be ...
2
votes
3answers
292 views

How can the Lorentz transformation cause two objects' masses to both increase?

Suppose there are two people A and B. A is standing on the earth and B is on a rocket in space. Now B passes by the earth at a speed of 0.9c and A sees him. According to A, B's mass would have ...
10
votes
2answers
579 views

Would the horizon of a black hole be different for a tachyon than for subluminal matter or photons?

One of the most useful black hole analogies I've seen imagines that space is "flowing" like a river into a black hole, and the point at which it flows in faster than c is the horizon. This analogy ...
19
votes
3answers
626 views

How to optically rotate images in small increments (for eyeglasses)?

As the result of an accident, one or more nerves that control the rotation of my left eye were damaged. The result is that my left eye views the world rotated clockwise several degrees, compared to my ...
2
votes
1answer
511 views

Equation for Hubble Value as a function of time

I am trying to write the equation for the situation where the Hubble parameter $H$ would be changing over time. In other words, it would represent an accelerated expansion of the Universe. That is, ...
1
vote
1answer
446 views

Why do we need hard steel balls to produce an unusual ‘chirping’ sound?

When two hard steel balls, or similar, are brought gently into contact with each other, an unusual ‘chirping’ sound may be produced.why do we need this material or shape to produce that sound?
5
votes
1answer
105 views

Has anyone tried to do Galileo's tower of Pisa experiment at a molecular or atomic scale

Galileo is reputed to have demonstrated that unequal masses fall at an equal rate by dropping them off the tower of Pisa and observing that they hit the ground simultaneously. Has anyone tried to push ...
7
votes
1answer
414 views

Wightman axioms and gauge symmetries

I have a basic understanding of the Wightman axioms for QFT. I was reading the about the Mass Gap problem for simple compact gauge groups and was wondering how the gauge group is supposed to be ...
0
votes
0answers
48 views

Resonance force with multiple emitters

Will I get a stronger resonance if I put multiple frequency generators around the same object? example image
3
votes
1answer
351 views

Why has a gravitational wave spin 2? (Group theoretically?)

How can I see, using group theoretic arguments, that a the quantum of a gravitational wave has spin 2? How can one show that it is described by a 5 dimensional representation of $SO(3)$? I know the ...
3
votes
5answers
7k views

Why does the moon not revolve around the sun directly?

The sun pulls on the moon with a force that is more than twice the magnitude of the force with which the earth attracts the moon. Why, then, doesn’t the sun take the moon away from the earth?
0
votes
2answers
52 views

What is the name of this principle?

What is the name of this principle? If the speed of the centre of mass $\vec{v}_{CM}$ of a solid is constant ($cte$), then the sum of the exterior forces that exerts into this solid ...
0
votes
1answer
179 views

Can't understand the principle of least action [closed]

I tried many hours to understand the principle of least action, and those hours become days... and I still didn't understand that principle/ and how it relates to Newtonian mechanics? Could someone ...
5
votes
1answer
268 views

Heat engines and “Angular momentum” engines?

We know that the theory of heat engines is that, if you accept the second law of thermodynamics, $\Delta S > 0$ then you can define temperature using $\frac{1}{T} = \frac{\partial S}{\partial E}$ ...
0
votes
0answers
14 views

Form factor and Guinier regime [duplicate]

sorry for reposting. I dont get why it is such a good idea to plot the logarithm of the form factor vs $Q^2$ in Guinier plots. It seems arbitrary to me.
0
votes
1answer
207 views

Guinier regime for form factor

Why is it such a good idea to plot the logarithm of the form factor vs $Q^2$ in Guinier plots. It seems arbitrary to me.
4
votes
2answers
179 views

Without apparatus can we say that the system is measured(decohered) by the environment?

"Einselection" and "tridecompositional uniqueness theorem" seem to resolve the preferred basis problem. But the premise is that there are three parts in discussion.(system, apparatus, environment) ...
2
votes
1answer
2k views

Can a macroscopic body have wavelength as that of electron? [duplicate]

Einstein has suggested that light can behave as a wave as well as like a particle i.e, it has dual character. In 1924, de-Broglie suggested that just as light exhibits wave and particle properties, ...
2
votes
0answers
133 views

How can the pre-measurement be fulfilled?

In the decoherence program, the pre-measurement refers to the evolution in which the system and apparatus form a Schmidt state. In Maximilian Schlosshauer's review article(2005), I read "the linearity ...
2
votes
2answers
323 views

Moving between degenerate vacua?

In spontaneous symmetry breaking, moving round the circular valley of Mexican hat potential doesn’t cost energy. These angular excitations are called Goldstone bosons. But doesn't the angular ...
4
votes
1answer
190 views

Why 1 Month LHC Magnet Cooling Times

An often quoted figure is that the LHC magnets take a month to completely cool and a month to warm. There is never an explanation as to why that is. I can conjure any number of reasons (slow changes ...
5
votes
2answers
419 views

Does diamond dust conduct heat as well as diamond?

Diamond is one of the best thermal conductors you can get. If the diamond is crushed into dust and spread out over a flat surface, but still held fairly compact (for instance in a small petri dish), ...
0
votes
3answers
2k views

Is tension always constant throughout a rope of mass in equilibrium?

Let's say we have a meter stick with a single rope attached to it. One end of the rope is attached to one end of the meter stick, the other end of the rope is attached to the opposite end of the meter ...
5
votes
0answers
182 views

does a rocking kettle cause the water to boil more slowly?

When I boil water in the kettle on my electric stove, sometimes it rocks back and forth making an annoying sound at a frequency of about 6Hz. When that happens, I move the kettle slightly to make it ...
0
votes
2answers
196 views

What electromagnetic wave produces the strongest electrical current when making contact with an element?

More specifically, what electromagnetic waves can we utilize to generate electrical power and out of those waves, which one would produce the most power? Additionally, which one would be the most ...
1
vote
1answer
114 views

Is it possible to calculate the half-life of a nucleus?

Is it possible to calculate theoretically the half life of a nucleus (how?) or they are all known through measurements? As an example how do you calculate the half life of Carbon-14?
0
votes
0answers
503 views

Relativistic elastic head-on collision: The momentum just reverses direction

Consider a relativistic elastic head-on collision between a projectile, with mass $m_a$ and velocity $\mathbf{v}_a$, and a stationary target of mass $m_b$. Here "head-on" means that the two particles ...
5
votes
3answers
362 views

Evaluating commutator of $[\operatorname{sign}(X),\, \operatorname{sign}(P)]$

I wish to evaluate the following commutator: $[\operatorname{sign}(X),\, \operatorname{sign}(P)]$. Is there a general method for evaluating $[\operatorname{f}(X), \operatorname{f}(P)]$? I thought of a ...
31
votes
5answers
2k views

What exactly is regularization in QFT?

The question. Does there exist a mathematicaly precise, commonly accepted definition of the term "regularization procedure" in perturbative quantum field theory? If so, what is it? Motivation and ...
4
votes
2answers
466 views

Canonical momentum density vs. energy-momentum tensor

Suppose we have a scalar field $\varphi$ with Lagrangian $$ \mathcal{L} = \frac{1}{2} \kappa \left( \frac{\partial \varphi}{\partial x} \right)^2 + \frac{1}{2} \rho \left( \frac{\partial ...
0
votes
1answer
99 views

Infinite mass in a coupled oscillator

Can someone help me with this? Imagine we have a system composed of three spheres 1, 2 and 3. 1 is connected to a wall on its left side with a spring and to sphere 2 with another spring, the sphere ...
3
votes
1answer
191 views

Schwarzschild geodesics

I've found on Wikipedia that energy $E$ and angular momentum $L$ of a particle are conserved quantities in Schwarzschild metric. It's written: $$L=mr^2 \frac {d\phi} {d\tau},$$ ...
0
votes
1answer
261 views

Is An Exploding Beer Bottle An Accurate Simulation Of A “Frost Quake”?

A Frost Quake or Cryoseism is similar to an earthquake except it is triggered by ice expansion instead of tectonic activity. A Cryoseism may also refer to the sudden movement of a glacier, but I am ...
0
votes
2answers
199 views

Calculating states of entangled and disentangled qubits

I'm writing a quantum computer simulator (about 8 qubits) and I know most of the basics (i.e. how to calculate the effect of a quantum gate on a qubit). But I have hit a wall. Is it possible, with ...
1
vote
3answers
224 views

Collision between a photon and a massive particle

Just a small question regarding collisions. Imagine a head-on collision between a photon and a particle with mass that moves with a non-relativistic speed, the particle was on its ground state, ...
3
votes
3answers
122 views

At what point is the spin determined in a Stern-Gerlach Apparatus

Consider a particle with spin that travels through a Stern Gerlach box (SGB), which projects the particle’s spin onto one of the eigenstates in the $z$-direction. The SGB defines separate trajectories ...
1
vote
1answer
589 views

2 Time Dimensions [duplicate]

Our universe has 4 dimensions, 3 spacial and 1 temporal. We can add another spacial dimension and use math to explore it. I cannot think of any reason why we cannot add add another temporal ...
1
vote
3answers
1k views

Why do I still get static shocks when hands are wet?

Quite a few times now I have washed my hands, and while my hands are still wet I will touch something metal and get a static shock. I thought static electricity doesn't really build up when there's a ...
2
votes
1answer
204 views

Can two spools shield you effectively against radiation

a friend of mine thinks that by buying a product called rayguard he can effectively shield against electrosmog. On the website, there are multiple evidences that this might work. However the product ...
0
votes
0answers
56 views

Does the spinning of a nucleus alter its charge distribution?

I put a nucleus in a magnetic field. It spins. Does the electric charge distribution remain homogeneous or does the charge redistribute? Can this be measured? Will accept reference as answer.
1
vote
3answers
1k views

Deriving the law of moments

Recall the Law of Moments for a one dimensional rod: "When an object is in equilibrium the sum of the clockwise moments is equal to the sum of the anticlockwise moments." I understand that we ...
2
votes
1answer
579 views

The curl of a special cross product

When given two vectors $\mathbf{A}$ and $\mathbf{B}$, the curl of the cross product of these two is given by ...
1
vote
1answer
203 views

Questions about Statistical Mechanics

For grand partition ensemble, is it true that the introduction of chemical potential allows us to have the sum of number of the particles in each state to be the total number of particles ("On ...
2
votes
2answers
857 views

Behaviour of duvet covers in washing machines

When you put a duvet cover in a washing machine without buttoning it up any other items of bedding (e.g. pillow cases) inevitably end up inside it. Instinctively, I would think that the opposite would ...

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