
Originally Posted by
sushy_bhat
I personally disagree on ur 3rd point although it has been assumed by physicists that photon is massless.Photoelectric effect proves the particle nature of photons and a particle widout mass is simply unimaginable.
Maybe for you. Not for scientists. Nature doesn't care about what anyone can imagine or not. Photons ARE massless.

Originally Posted by
Vemedu
Thinking about this a bit more I believe my confusion came from a bad understanding of equality/identity and mass/rest mass.
Energy and mass are not the same thing, but they are equivalent, i.e. mass can be transformed into energy and vice versa.