# All Questions

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### Quantum physics and object location

If I understand correctly, according to quantum physics, subatomic particles can "leap" from one location to another (for example, from a location on earth to a location on the "other side" of the ...
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### Special Relativity Theory on human aging [on hold]

Ok, people that know me would say I don't think in terms termed "normal" so here is a strange question to consider. Please don't get stuck on grammar and numbers, and try to understand the intent. ...
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### High Young's Modulus and Tensile Strength of Carbon Nanotubes

I was recently reading about Carbon Nanotubes having extremely high Young's moduli, as well as high Tensile Strength, making them very interesting fibers. However, when I read this I wondered what was ...
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### Separation of variables in various PDEs, physical meaning

The method of separation of variables produces an undetermined separation constant and a family of solutions indexed by the values of this constant. For instance, in the case of an infinitely long ...
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### How is the probability of intersystem crossing influenced by small differences in energy levels?

Say I have some dye molecule in some low level triplet state, e.g. $T_1$, and it's decaying slowly to the ground state via phosphorescence. However, there are also events where the dye in the $T_1$ ...
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### Determinstic implementation Sphere of Influence change using Patched conic approximation

wasn't 100% sure which StackExchange to ask this on, as it could be related to Gamedev (as it's for a game), maths (as it's a approximation model rather than a physical description) or StackOverflow ...
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### shear and normal stresses

When we talk about shear stresses in a fluid, we find that the shear stress is given by $$\tau_{xy} = \mu(\partial_y u + \partial_x v) = \tau_{yx}$$ This relation we get when only looking at one side ...
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### What is “number degrees of freedom for frequency ν”. Frequency is 1D right?

The book QM Demystified states this about black body radiation spectrum: An attempt to explain these results using classical theory was codified in the Rayleigh-Jeans formula, which is an ...
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### Does radio use virtual photons?

In radio communication each accelerated electron in the transmitter antenna interacts with an electron in the receiver antenna by exchanging a photon. Is that photon always a virtual photon as ...
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### What are some important equations in mechanics that can only be solved numerically? [on hold]

I got introduced to a few equations where classical techniques of finding solutions failed to apply. Out of curiosity, I would like to know what are some of the most important yet unsolvable equations ...
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### Understanding Wikipedia's “Semiconductor Band Structure” diagram where the bandgap appears to increase with increasing density of states

I'm having a bit of trouble understanding the semiconductor band gap diagram on Wikipedia: (from Band gap article). Why is the size of the band gap increasing with the Density of States (DOS) in the ...
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### Car moves with non-uniform acceleration with decreasing mass [on hold]

Can someone answer this question : The car is in rest position With mass 200 kg (including 180 kg of fuel, i.e dry mass of car is only 20 kg). If the engine provides a force/thrust of 200 N ...
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### What other ways are there to achieve levitating cars other than conventional propulsion systems? [on hold]

The main challenge to flying cars is gravity. The conventional response is to use conventional propulsion systems such as engines that create thrust, or magnetic levitation. Are there other ways that ...
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### Gravity on the International Space Station - General Relativity perspective

My question is an extension to this one: Gravity on the International Space Station. If all the outside views of the ISS was sealed, then the crew inside would not be able to tell whether they were ...
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### At what frequency does the medium of air change from acoustic to light?

I'm calculating the max doppler frequency of a fading channel in an in-room environment and looking at different carrier frequencies. Calculated as follows: F = vf/c Where F -> max doppler shift v ...
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### What gives an object its colour?

My understanding of colour is that atoms in a particular object will absorb certain wavelengths of electromagnetic radiation, and the scattered wavelengths give the object its colour. The absorbed ...
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### Nuclear Spin of Sodium 23

I am actually calculating the nuclear spin of Sodium 23. Here we have 11 protons and 12 neutrons. Now both the nuclei are short of the magic numbers. When I use the shell model for protons and ...
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### Calculating Forces via Feynman diagrams?

How would one go about calculating forces that test objects feel using Feynman diagram methods? For example, say we have a massive object in GR so that the metric takes on the standard ...
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### Lenz's Law and Eddy Currents

You can determine the direction of eddy currents according to Lenz's law. E.g. If a metal sheet is losing flux into the page, it will experience induced eddy currents in a clockwise direction to ...
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### Does pressure drop across pipe affect flow rate?

Let's say there is a main pipe containing $100\: \mathrm{m^3/hr}$ a fluid of density $750\: \mathrm{kg/m^3}$ and it's gonna be branched into 2 pipes (Pipe A and Pipe B) of the same diameter. If Pipe A ...