All Questions

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Light bodies at high speeds behave like heavy objects when recorded by a high speed camera

This is potentially a very dumb question, but recently I was looking at some slow motion footage of bullets hitting stuff and I realized something interesting. One of the clips showed two metal ...
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A question about Fermi-Dirac Distribution function

It seems more like a mathematical question, about the property of Fermi-Dirac Distribution function $$f=\frac{1}{e^{(E-\mu)/k_BT}+1}$$ where $\mu$ is the chemical potential and $k_B$ is the Boltzmann ...
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Canonical equal time commutation relations in QED

I understand that to quantize the classical electromagnetic field one needs to impose commutation relations and express the field in terms of creation and annihilation operators. I notice that the ...
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Photons traveling backwards in time?

Imagine that two widely separated charged particles $A$ and $B$ exchange a photon. Because they are far apart one can imagine that there is a major contribution to the photon propagator that travels ...
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What is more important in terms of damage in a car crash, momentum or kinetic energy?

Momentum is $mv$, kinetic energy is $1/2 mv^2$ and I have a car run into a brick wall, or maybe an egg thrown against a wall. On one hand you can think about the maximum force exerted on the car or ...
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Simple harmonic oscillator: zero point energy?

Today we had a lecture on the simple harmonic oscillator and its quantum mechanical treatment. My teacher derived the equation for it and finally concluded it has some zero point energy. My ...
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Finding Average Speed [on hold]

Jordan takes his bike out for 5 hours. For the first three hours, he rides his bike at 10 miles per hour, he then stops to rest for one hour and then continues his ride. For the last hour he rides ...
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Is the standard model so full of holes it is time to start again? [closed]

I have read a lot about dark matter and dark energy, the fact that we are spending a small fortune trying to detect their presence, but the only reason they have been postulated it is an effort to ...
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Could Dark Matter form black hole?

Some people speculate that the mysterious dark matter in the universe could be tiny black holes. But on the other side, could dark matter particles attract each other by gravity and finally form a ...

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