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 Dec 23 answered Aspherical lenses Dec 22 answered Can radio waves be formed into a pencil beam? Dec 22 comment Controllable faster-than-light phase velocity @Mark Eichenlaub, I understood the question to be whether you could design a material with any particular phase velocity that you wanted. But see the edit to my answer. Dec 22 revised Controllable faster-than-light phase velocity expanded answer Dec 22 answered Controllable faster-than-light phase velocity Dec 16 comment Reflected and refracted wave sphased A phase conjugated mirror's effect is non-linear, but the Goos-Hänchen effect takes place in linear media. It has to do with the penetration depth of the wave into the medium, if I remember correctly. Dec 16 revised Reflected and refracted wave sphased edited tags Dec 16 answered Reflected and refracted wave sphased Dec 16 awarded Organizer Dec 15 awarded Enlightened Dec 15 awarded Nice Answer Dec 11 awarded Nice Answer Dec 11 awarded Quorum Dec 8 comment Is there a travelling speed of for electric field? If yes, what is it? possible duplicate of Is electricity instantaneous? Dec 8 comment Is there a travelling speed of for electric field? If yes, what is it? Are you sure that photons travel through the wire? If the current is DC, then the frequency of these photons is 0, and so according to $E=\hbar\omega$ they have no energy? I always thought that it was just a disturbance in the electric field. Dec 8 comment Is there a travelling speed of for electric field? If yes, what is it? Huh? So even the one-meter wire would cause the bulb to light 2 hours and 47 minutes after you flip the switch? Dec 7 comment Why does dust stick to rotating fan propeller? Fans can often be found in kitchens, which makes them even more likely to be sticky with oil. Maybe not your fan, but I'm sure this explanation accounts for at least half the dust found on fan blades! Dec 7 comment Theoretical Physics - How to? Looking back on my answer, I see you might have interpreted it as saying that a theorist had to be an excellent experimenter too - I've edited it to say what I really meant, which is just that it's important not to ignore experimenting. Dec 7 revised Theoretical Physics - How to? edited to clarify intent Dec 6 answered Theoretical Physics - How to?