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 Jun 20 comment Human max speed in open space @Rodolphe What then? I thought we were talking Newtonian. But if you see curved spacetime, then it's because there's an interaction with something producing that curvature. Jun 16 comment Why is the Baryon Acoustic Oscillations (BAO) calculated like this? @ChrisWhite I know, I was really surprised. I rephrased the question to make it independent of that wikipedia page. Jun 4 comment Can we assume black hole is just two big stars revolving around each other? Downvote why? Nothing I said was wrong, it was a completion to the answers. Jun 4 comment Turning points of particle @RafaFafa You're welcome! May 15 comment What is the length dimension in critical phenomena? Hm, I had $\xi$ defined as $$\xi^2=\frac{\int_0^\infty r^2G(r)}{\int_0^\infty G(r)}$$ But anyway, I know the expression of the correlation function in the three regimes, I just fail to see why I should expect values that don't depend on the size of the system for dimensionless variables. Thank you for answering May 15 comment What is the length dimension in critical phenomena? @MengCheng I think it's the word length that confused me, sorry. For example the Binder cumulant as defined in the previous question ($\langle m^4\rangle/\langle m^2\rangle^2$) is dimensionless, why should it be better that $\xi/L$ to find the critical point? May 15 comment What is the length dimension in critical phenomena? @Danu Well, I know what a dimesionless variable is. I just don't know how that applies. If a quantity is dimensionless, then in a scale invariant system, it should not depend on size. Is that it? Why? And if so, should any dimensionless quantity I could build behave that way? For example, if the susceptibility goes like $\chi\sim L^{\gamma/\nu}$, then $\chi/L^{\gamma/\nu}$ behaves that way although it has dimensions. May 15 comment How to interpret a null critical exponent? @MengCheng Ok, thank you May 15 comment How to interpret a null critical exponent? And is there any deeper reason for it instead of being just because the $\log$ function diverges slower than any power? Feb 4 comment How the torque/moment-of-force can be mathematically defined? Yes it is, they are not being added, they are being multiplied. Do you have any trouble multiplying distance with the inverse of time to get a speed? This is the same thing. Feb 4 comment How the torque/moment-of-force can be mathematically defined? Well... you are not adding position and force which wouldn't make sense. You're multiplying them, which produces a new unit Newton*meter. Mathematically, they both belong to $\mathbb R^3$, so they belong to the same space and that product is perfetly well defined. Jan 29 comment Why does choosing a time break covariance? Some simple example would be greatly appreciated, I think that would trigger my understanding. Thank you for your answer by the way. Jan 29 comment Why does choosing a time break covariance? That is exactly my question, in which point of defining canonical momentum or legendre transforming the lagrangian do you fix a time? Couldn't you just define the momentum to be $\partial\mathcal L/\partial\dot\phi$, with the dot representing any parametrization of time in minkowsky space? Jan 24 comment Electric dipolar moment of a half wave antenna @Georg never mind, the name is irrelevant. It's a wire with that current. Jan 24 comment Electric dipolar moment of a half wave antenna @Georg Sorry, half wave Dec 9 comment Constant quantity associated to symmetry @bechira I am uncomfortable with stating that as some kind of theorem. I'd expect some kind of relevant content, plus I know how Noether conserved charges come out from symmetries, and I was expecting to see a connection. Jul 8 comment Light dispersion in water So if I incide light not normally in a big amount of water, will I see dispersion? Shouldn't then I see dispersion by looking at the sun (when it's NOT on top of the sky) from behind the water, for example in the sea? Jun 16 comment Decomposition of this wave function in eigenfunctions Thank you for your help. That's what I initially thought, but he made some reasoning before calculating, and doing that in the case when the highest value for $\ell$ is, let's say, $10$, doesn't seem very efficient. Jun 16 comment Decomposition of this wave function in eigenfunctions Thank you very much. I give you the correct answer for completeness. Jun 13 comment Calculation of magnetic force magnitude from a parmenant magnet What's vertical pull? What units do they give you for that? Can you link the website?