If light photons are massless particles traveling in a vacuum, why is the direction of an angular photon permanently affected by a localized gravitational field as currently described by general relativity (path A on the figure - gravitational lensing). Shouldn't they still follow a 'linear' (not...

I've found the following paradox, and I wonder how to resolve it. Two discs are floating in space, call them A and B. They are at a fixed distance D, coaxial, and rotate at the same speed. Each of them has a hole near the border. The position of the hole in disc B lags behind the position of the ...

Cyan (blue light + green light) + red light = white light, but is the same true for cyan wavelengths ($490-520$ nm) and red wavelengths ($630-700$ nm)?

Given a path integral for a system $$Z(\phi) = \int [D\phi] e^{-S[\phi]},$$ where I am working in the Euclidean signature, necessarily mean that the system described is quantum mechanical? In the equation above, I am looking at $(d+1)$ dimensional field theories, such that $d=0$ Feynman path inte...