It's been mentioned elsewhere on this site that one cannot define a position operator for the one-photon sector of the quantized electromagnetic field, if one requires the position operator have certain formal properties. This is a theorem that holds only for massless particles of helicity $|\lam...

Where is the "extra help" coming from when rolling the object on wheels?

My point is that there is no superposition of dead and alive. The cat will cause the probability function to collapse long before we open the box. What am I missing here? Isn't the cat capable of collapsing the probability function? If not, why?

Faraday's Law of induction states that the work done per unit charge by the (induced) electric force along a loop of wire, or the emf, is minus the rate of change of magnetic flux through the loop/surface and is given by the equation $$\mathcal{E}_{Ind.}=\oint \vec E_{Ind.}d\vec l=-\frac{d\P...

I've been studying kinematics just for a while, and the question that bothers me the most is the difference between those two. I think that there is a difference, such as uniform velocity implies constant speed (but does not imply constant direction) and constant velocity implies constant speed ...

Can two waves (like sound or electromagnetic waves) interfere head on? If yes, and suppose they are out of phase with each other and thus interfere destructively, where does the energy of the waves go?