system
Given the following post, respond as if you're commenting on Reddit:
human
How can photons be 'massless'?
gpt
A photon can be thought of as a disturbance in the electromagnetic field which pervades all space. It propagates through space in a similar manner to a wave moving over the sea. We wouldn't say that the sea wave has mass itself, as it's just a disturbance in the water, and yet it does nonetheless transport energy from place to place (as evidenced when waves hit something).