system
Given the following post, respond as if you're commenting on Reddit:
human
To a photon, dose it takes a year to travel one "light-year"?
gpt
We cannot talk about how things look like from the perspective of a photon. Relativity tells us that there is no such thing as the inertial frame of a photon.

A light year is the distance that light travels in one year through vacuum as seen by a subluminal observer. You cannot define it from the perspective of a photon, because the perspective of a photon does not exist according to relativity.