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Jan
7
answered Limitations of 2D point-mass Dynamics of the solar system
Jan
4
comment Why is Standard Model + Loop Quantum Gravity usually not listed as a theory of everything
Exactly, your statement is a much more precise formulation of what I said. At low energies, one may write down marginal and relevant operators that violate the Lorentz symmetry, and if the UV starting point (theory) fundamentally violates the Lorentz symmetry, the coefficients of these relevant and marginal IR terms are pretty much guaranteed to be nonzero. This breaking of the Lorentz symmetry remains the same (marginal) or gets even stronger (relevant) at long distances.
Dec
31
comment What would be the implications for current theories if gravitational waves are not detected?
Dear UTF-8, it's little bit like asking how the universe would work if 1+1 were 3. It wouldn't work too well. Even when physicists see something unexpected, they're still trying to find the most conservative explanation - one that is most natural, least artificial, and compatible with other things. So if the rumor goes away and LIGO doesn't announce the discovery in a month or two, people will try to look for mistakes in their theories of binary stars, in the LIGO itself, and so on. Theorists had enough time to find gravitational waves rejecting theories but no one has found good candidates.
Dec
30
comment Why do dark objects emit more than lighter ones?
Kevin Ye's or a basically equivalent argument is really the only sensible answer one can get. One could discuss what is happening microscopically. But one would still need to translate the concepts of "black" and "white" to properties of the microscopic building blocks which is rather complicated. And at the end, what one really wants to deduce are just statistical properties referring to absorption and emission of large amounts of light quanta. So one has to use overall thermodynamic properties like the temperature of both bodies, emissivity, absorptivity etc. somewhere in the explanation
Dec
30
comment Why do dark objects emit more than lighter ones?
Dear @Dave, so you don't mean a "proof vs physical explanation". You mean an "argument using overall macroscopic quantities" vs "argument using microscopic, constructive concepts". You can't really do the latter too well here because "black" and "white" are concepts describing the overall macroscopic appearance of an object, not its microscopic composition, so one must unavoidably use some of the macroscopic arguments that, in your logic, turn an explanation into a "proof".
Dec
30
comment Why does the symbol have an arrow?
Well, a kid may play with the hand on the voltmeter or ampermeter, too, can't she? ;-) The position of the hand will be a variable dictated by the user which decides about some physical consequences - e.g. about whether or not a gadget gets broken. I think that your interpretation of the arrow as a "user variable" is a self-inflicted injury. You just decide about a prejudce that the arrow can't mean the hand on a voltmeter, so then it can't mean the hand on the voltmeter. But if you "define" the arrow to represent any mechanically movable part, which is common sense, you will have no problem.
Dec
30
revised Why is $|\Lambda^0_0| \ge 1$ for a Lorentz transformation?
added 552 characters in body
Dec
30
answered Why is $|\Lambda^0_0| \ge 1$ for a Lorentz transformation?
Dec
30
comment Why does the symbol have an arrow?
All these gadgets, voltmeter, ampermeter, and potentiometer, have the symbol with the same diagonal arrow (aside from other symbols without it) because all these gadgets contain the very same thing: a component that is mechanically moving, a little hand that may point to different directions (therefore symbolized by the arrow). This is no mistake or a "collision" in notation. It's like saying that $\vec E$ and $\vec B$ are in collision because both letters have arrows above them. But that is how things should be - both quantities are vectors and that's what the arrow means in this context.
Dec
30
comment Why do dark objects emit more than lighter ones?
Dave, what is the difference between your "proof" and a "physical explanation"? And if there is a difference, isn't a proof always the "better, safer thing" to have than just a "physical explanation"?
Dec
30
comment Does Earth rotation effect planes?
If you claim the discovery that the Earth cannot be spinning, with planes as a proof, be ready to share the Nobel prize with a Saudi cleric. english.alarabiya.net/en/variety/2015/02/16/… english.alarabiya.net/en/webtv/reports/2015/02/16/…
Dec
30
comment conformal, Weyl transformations, apparent discrepancies and confusions
Apologies, I believe that I have already answered exactly these questions as clearly as I could so I would only repeat myself. But if you want. Conformal transformations are a subset of coordinate transformations defined by the requirement that the metric tensor at each point may change only by an overall (Weyl) scaling. That's why the non-Weyl part of the change of the metric tensor may be omitted - there's none. Conformal invariance is the invariance of the action under the conformal transformations - or, equivalently, under the Weyl part of it (because there is no other part).
Dec
29
awarded  Good Answer
Dec
29
comment Lagrangian description of Brownian motion?
That's a very interesting proposal.
Dec
29
comment Why is quantum entanglement considered to be an active link between particles?
Dear @GetFree, it doesn't matter whether "it" represented "quantum mechanics" or "quantum entanglement". The latter is just an unavoidable omnipresent feature of the former. Almost all states in the Hilbert space are entangled; almost all predictions for pairs of quantities in almost all "composite" QM problems show entg.-like correlations. The word entanglement hasn't been coined up to 1935 but the predictions of quantum mechanics we categorize as "implications of entanglement" today have been known since 1927 if not 25. The EPR+Schrödinger's 1935 contributions were just in terminology.
Dec
28
revised Why don't they use springs as an energy source for cell phones?
added 420 characters in body
Dec
28
awarded  Enlightened
Dec
27
comment Why don't they use springs as an energy source for cell phones?
Dear Bob, it's entertaining but if taken seriously, one can't improve the energy density by more than an order of magnitude or so. The metallic pieces start to break when one tries much higher tension. The old clockmakers have tried to take it to the limit. One can't really reach the chemical energy density by realistic tension because the chemical energy means that the electrons in each atom are already strongly, qualitatively rearranged. A wound up spring means that they're just "moderately" displaced - a smaller change of each atom.
Dec
27
awarded  Good Answer
Dec
27
awarded  Nice Answer