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22m
comment Relativity gedanken experiment
@MFH: That is completely false, SR can handle accelerated motion perfectly well.
10h
comment How much energy does it take to simply run forward?
@innisfree: Air resistance may not be the biggest factor but it definitely is one. When you're riding on a bike and there's wind you can definitely feel it gets harder to move.
22h
comment Fermions, different species and (anti-)commutation rules
@AccidentalFourierTransform: But that can be if not justified at least motivated: we use anticommutators because quantizing with commutators breaks Lorentz invariance (I think), or because that way we get the Pauli exclusion principle. Do these reasons still work for two different particles?
1d
comment Fermions, different species and (anti-)commutation rules
@AccidentalFourierTransform but how do you know the Poisson bracket has to be replaced by an anticommutator when there are two different fermionic particles?
1d
comment Fermions, different species and (anti-)commutation rules
But why is it like this? How would I figure out which one is right, either from first principles or from experimental evidence?
1d
comment How do I remove the negative sign from this derivation?
@BillN: Your alternative is mathematically valid but not physically valid, since $\alpha$ is the fine structure constant (at least in this context).
1d
comment How do I remove the negative sign from this derivation?
I can't imagine any situation in which it would be useful to have an imaginary fine structure constant. Most likely someone didn't want to bother writing all the signs.
2d
comment How do we acquire c-coefficients (“weights”, “probabilities”), when dealing with superposition of stationary states?
If you only know the average energy, you can't find out the coefficients, so the problem you propose cannot be answered without further information. This is not particular to QM; you could just as well ask "given that a ball is somewhere on Earth, what is its velocity?" and I wouldn't have an answer either.
Feb
10
comment Proof of Ampère's law from the Biot-Savart law for tridimensional current distributions
If physical insight was what you wanted you probably wouldn't be asking this question. And most mathematicians probably have heard about Maxwell's equations, especially the ones who know how to answer your question.
Feb
10
comment Proof of Ampère's law from the Biot-Savart law for tridimensional current distributions
Is there any particular reason you've asked this question here instead of at Math.SE? I feel like you would get a better answer there.
Feb
9
comment If quarks are fundamental, and mass is a form of energy, then can quarks/leptons be pure energy?
See this question: physics.stackexchange.com/questions/15122/…
Feb
9
comment Identifying Lorentz Covariant Equations
It would help if you explained a little what your understanding of Lorentz covariance is, and why you chose the answers you did.
Feb
6
comment Decoherence and interpretations
In this context I'd take collapse to mean that while decoherence reduces an entangled pure state to a mixed one, we still don't know why only one possiblity is chosen, or how. It's possible that the question has no answer.
Feb
6
comment Light is/produces a electromagnetic wave, but is the opposite also true?
Light is an electromagnetic wave. They're precisely the same thing, unless you mean "visible light", which means "EM waves with wavelengths between 400 and 700 nm".
Feb
5
comment How has the world remained in balance?
I didn't downvote, but personally I feel your answer is lacking because it doesn't address OP's misconception (like I tried to do with my answer).
Feb
4
comment Will the CMB eventually recede outside our observable universe?
@EmilioPisanty: I explain this in my answer: the CMB will get more and more redshifted as time goes on. As long as the expansion of the universe continues the frequency of the radiation (or, if you prefer, the energies of the photons) will get arbitrarily small.
Feb
4
awarded  Nice Answer
Feb
4
comment Will the CMB eventually recede outside our observable universe?
@EmilioPisanty: I'm not sure what you mean. If the expansion is accelerating won't the redshift just get faster?
Feb
3
answered Will the CMB eventually recede outside our observable universe?
Feb
3
comment How does the Physics work for the Quantum Suicide thought experiment?
I think "the observer will hear click with 100% certainty" applies only to the subset of worlds where the observer is still alive, since a dead experimenter won't be able to hear clicks. This sounds like either semantics nitpicking, or an interpretation where the observer is required to be a conscious person, or a misuse of MWI, I'm not sure.