For gravity to affect it, wouldn’t light have to have mass? Or do we attribute the Doppler shift to the bending of space by the immense gravity of the black hole?
Bent space...................
Light has mass and momentum - a photon is basically an electron moving at light speed.
Light is odd in that it behaves as both a particle and a wave.
I personally think all of creation is both particle and wave it is just a matter of spacing, frequency, and wavelength. The problem is that we don’t have the necessary instruments to perceive those that are extremely large or those that are extremely small.