Redditor Pidgey_OP explains: "What he means by "to scale" is that the distance the light moves in a given amount of time in the gif multiplied by the ratio of this gif to the real world, is an accurate representation of the distance the light moves in the real world at 1:1 scale. Any size can be "to scale" but once you begin adding the element of time and distance traveled, things get more complicated."