# All Questions

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### Very precise calculation of the heliocentric position coords (X, Y, Z) the point of coordinates (N/S, W/E degrees) on Earth

I need a very precise calculation of the heliocentric position coords (X, Y, Z) the point of coordinates (N/S, W/E degrees) on Earth. Currently, thanks to the algorithm which generates the position ...
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### Books for students [duplicate]

Can any one please suggest me books for physics. I need a book for good theory and concept . And a book for practice , it should contain some solved questions. The both the books should contain ...
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### What is exactly the difference between an active and passive frequency standard?

In the case of passive atomic frequency standard, we take an atomic reference which has a resonant frequency response centered at certain particular frequency. Then we take a local oscillator and tune ...
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### What to do when the fields are arranged in a matrix

I am dealing with a Lagrangian in which the fields are arranged in an $N\times N$ matrix and i have to find the minima of the potential. Usually i would write the Lagrangian in components and then ...
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### Mathematical formula for maximum sound pressure level

I googled a math equation for calculating Maximum Sound Pressure Level but couldn't help myself. What is it?
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### Scattering in Schrödinger picture

If we look at a scattering process in the Schrödinger picture for a Hamiltonian $H = H_0(t) + V(t)$ where $H$ is independent of time (because we examine a theoretical situation after accelerating ...
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### Are pure Dirac fermions (electrons, quarks, …) allowed to have effective Majorana mass?

Charged particles such as electrons and quarks are not allowed to have a hard Majorana mass (see here). With 'hard' I mean an explicit mass term in the Lagrangian which would break the corresponding ...
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### Why does LIGO do blind data injections but not the LHC?

The LIGO group has a team that periodically produces fake data indicating a possible gravitational wave without informing the analysts. A friend of mine who works on LHC data analysis told me that ...
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### Noether current for a transformation for the Klein-Gordon Lagrangian

I have this Lagrangian density $$\mathcal{L} = \frac{1}{2}(g^{\mu\nu}\partial_\mu\phi\partial_\nu\phi^* - \mu_0^2\phi^*\phi)$$ with $g_{\mu\nu} = g_{\mu\nu}(x^\alpha)$ and I need to get the Noether ...
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### Eigenvalue equation with position operator

I have done a little run through of a basic QM eigenvalue equation for a particle on a 2D plane from bra-ket notation in the spirit of a complex position operator, although I have solved the SE, ...
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### How to find electric potential from electric field?

How to find potential difference when electric field is given ?
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### does changing air velocity change the frequency of sound coming out of a whistle?

If I use an air compressor and vary the velocity of the air coming out, does the frequency of the whistle change too?
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### Thawing of permafrost causes positive feedback loop in greenhouse effect?

This is claimed in my climate change class, which is admittedly pretty sparse in rigorous climate physics. The reason is that there are pretty large carbon deposits in glaciers which will further the ...
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### World's Largest Radio Telesope : How accurately does it need to be figured?

In Guizhou Province, China, the worlds largest radio telescope is almost complete, measuring 500 metres across. I am aware that todays largest optical telescope require very accurate figuring and ...
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### Is the magnetic field caused by the lenght contraction, as seen by us, in the frame of a fast moving charged particle?

If for example an electron moves very fast relative to us, then the length contraction as seen by us, causes the electric field lines to compress themselves in the direction of motion. Is this the ...
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### Is the change in viscocity of water at 1C vs 99C discernable visually?

Waters viscosity varies from 1.7 at 0C to .3 at 100C. Is this visually confirmable?
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### Can a Van de Graaff Generator be used to put plasma at high potential?

Lets say hypothetically, we use a sphere of plasma (ofcourse lab-plasma, stabilized somehow) instead of a sphere of metal in a van de graaff generator. Now can we use it to put a large amount of ...
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### High School Physics What to Do [duplicate]

I am an aspiring physicist in high school and I would like to know ways to get involved. Of course, it would look great for potential physics colleges, but I really want to understand physics better. ...
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### Why is Wick contraction a c-number

It is mentioned in Fetter's Quantum Theory of Many-Particle Systems (in contraction part of section 8 Wick's Theorem), that: contractions are c numbers in the occupation-number Hilbert space, not ...
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### Does closing the shades at night make the room brighter?

Does closing the shades at night make the room brighter? Is the light kept in, or is the dark kept out?
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### Why does the centrifugal term involve a vector originating from the center of Earth?

Why in every mechanics/dynamics book I look the centrifugal force due to Earth's rotation is measured from "the center of Earth"? For example in Marion's dynamics, the fixed inertial axes are placed ...
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### Hot Water fountain experiment with mohr pipette

Why does water shoot out the tip of a Mohr pipette when half filled with hot water and turned upside down?
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### Schrödinger-Pauli Equation Solutions

The Schrödinger-Pauli equation is the non-relativistic limit of the Dirac equation, and therefore describes spin-1/2 particles in an external electromagnetic field. It is given by: ...
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### What is the gravitational/electric/inverse-square field inside a cylinder?

I've read from the shell theorem that an inverse-square potential has zero field inside a spherical shell. What about the field inside a cylinder? Are objects inside a long cylinder attracted to the ...