I am not a physicist, and not sure whether I want the adjective, or the noun, observable here. Example 1) If we view the mass and velocity of a classical particle as observables, we calculate the kinetic energy. Is that observable? an observable? Example 2) In electrodynamics I read that charge a...

Wikipedia defines Lenz's law as that the magnetic field created by the induced current opposes changes in the initial magnetic field, "Lenz's law states that the direction of the electric current induced in a conductor by a changing magnetic field is such that the magnetic field created by the i...

Let's say I have a hydrogen atom in the lab. "Normally", we would say its electron is delocalized across the ground state orbital. Because electrons have mass, we expect it to exert a gravitational force. However, the location of the electron is uncertain (since it is delocalized). Does this mean...

I am trying to understand the photon propagator renormalization procedure, followed in M. Srednicki's book Quantum Field Theory. Specifically, I am reading Chapter 62, titled "Loop Corrections in Spinor Electrodynamics" and I am focused on the renormalization of the photon propagator at the loop ...

I understand the standard theory of angular momentum and the reps. of SU(2). I found there are some zero elements in CG coefficient table. I can derive them by using the recurrence relations between CG coefficients.But I am wondering is there any physical picture rather than mathematical derivati...

If we have a metal ball, why does it follow the law of reflection after it hits a wall? My point is that if it applies a force on the wall at an angle say 30deg below the horizontal (the wall is the vertical itself), shouldn't the wall apply a force back which is completely opposite to the origin...