# All Questions

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### What is the typical strength of the electric field in a particle accelerator?

I am working on a research project involving the closed orbits of hydrogen in the presence of an external electric field and I am curious what a reasonable approximation for the electric field ...
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### Magnetic field between two rings

Two rings are placed parallel atop each other along an axis with a distance $\epsilon$ which is much smaller than the radius of both rings a. Through one of the rings there is a current I and through ...
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### Relativistic Lorentz Force with constant, perpendiuclar, and uniform E and B fields

I am trying to solve the following problem from the Fundamentals of Plasma Physics by Bittencourt (Problem 2.7): Analyze the motion of a relativistic charged particle in the presence of crossed ...
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### Where are real limits of evaporative cooling?

There are many projects focused on utilising evaporative cooling for food preservation or computer cooling purposes. I have other thing in mind, however and that's cooling beer. Once you're outside, ...
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### Present moment in physics

Here is my first "popular science" "vague" question, which I hesitate to keep for myself until it becomes a precise question. Instead of wondering about what time is, I'll just assume it's a parameter ...
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### How close to the wavelength of light have to be to inter-planar spacing for diffraction to occur?

I'm doing past papers for my exam on Wednesday, and I've come to a question I'm stuck on So, you have x rays of lambda = 0.25nm incident on a cubic unit cell with lattice lattice constant a = 0.286 ...
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### How to understand a discretized action in Jan Smit's book?

I am reading Jan Smit's book Introduction to Quantum Fields on the Lattice. How did he get the result of eq.4.80, the discretized action for gauge fields? In eq.4.72, he gave the gauge field action ...
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### How bright would the Earth be at night without the moon?

How bright would the Earth be at night without the moon? Specifically, how much light would reach the surface of the Earth at sea level?
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### Could Bluetooth radio waves be used to pick up UV light

i am a bit of a Physic novice. But i was wondering if someone could answer this and if they might be able to make a possible sugguest. i was wondering if it possible for a bluetooth to be able to ...
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### Do bras and kets have dimensions?

I'm trying to understand more intuitively what bras and kets are, but some aspects of them remain a mystery to me. We usually think of $\psi (x)$ as having dimension of $[1/\sqrt{L}]$ so that ...
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### Clarification on isotropic sources and fields

For an isotropic radiation field the net flux is zero, something I find quoted in a lot of notes and text on radiation. We often think of isolated stars as isotropic sources, but their net flux is ...
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### Is a matter anti-matter collision comparable to Gamma Ray Burst (GRB) energy output?

Is a matter anti-matter collision (please assume two cosmological objects, neutron star sized say), the largest energy release method known? Would it be comparable in order of magnitude to gamma ray ...
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### Why bumble bee cannot fly aerodynamically?

I just saw this pic So I got curious and logged in on physics.stack first time, is it true? I am a math major and usually wander on mathstack but I would like to understand why Bumble bee cannot ...
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### Pumping water from a well

I have water well $h_1=70~m$ below ground level. A cylindrical tube of diameter $e$ joins the well to a tank of height $h_3=10~m$, $h_2=1.5~m$ above the ground. The tank is initially filled with water ...
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### A force in a homogeneous magnetic field

Semi infinite parallel conductors, while on them without friction slides a crossbar . Perpendicular the plane of the conductors is a homogeneous magnetic field. To what extent of force we must act on ...
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### What's outside of the universe?

Assuming you found a way and managed to accelerate above light speed without disintegrating, and went to the edge of the universe, what would happen? Would you instantly explode due to the lack of ...
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### How many observations are needed to determine a comet's orbit?

Based on the following facts: We have Kepler's laws of planetary motion. We have a good knowledge of the positions and orbits of the gravitationally significant objects in the Solar System. We can ...
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### Is there any matter inside an event horison?

Consider a feeding, growing black hole. We never observe any matter to cross the event horizon, because time stops there. All matter would be "stuck" in a sphere around the event horizon, slowly ...
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### Magnetic field at a distance from a metal rod

A massive metal rod of 4 cm has a current of 8000 A running through it and the current density is uniform. What is the magnetic field a distance 1 cm from the rod? Should I use the Biot Savart law and ...
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### Meaning of these terms for stress fields?

I'm from a math & comp sci background and I'm currently looking at facture theory which deals with stress fields. Can someone explain to me what the following terms represent in the context of a ...
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### Action-Reaction pair in case of rocket accelerating in space

I understand Rocket works on Newton's 3rd law. So there has to be action-reaction pair acting on two different bodies. I know rockets accelerate in space, where there is nothing. So now I want to ...
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### Where does this relativistic relation involving the delta function come from?

$$\int\delta(E^2-\mathbf{p}^2-m^2)dE=\frac{1}{2E_\mathbf{p}}$$ Shouldn't integrating the delta function like this just give 1?
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### What is the principle used by mangalyan to place it in mars orbit with 0 fuel consumption?

Recently I came to know from a seminar that where most of the satellites need gallons of fuel to be consumed to get placed in one planet's orbit Mangalyan took 0 fuel and it waited for the 'right ...
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### Sonoluminescence spectrum

During cavitation created by sound in a liquid the collapse of the bubbles can lead to very high temperatures and pressures resulting in the emission of light - sonoluminescence. Can the spectrum of ...