Caption: To-scale animation of a light pulse propagating from the Earth to the Moon.

Credit/Permission: © User:Cantus, before or circa 2007 (uploaded to Wikipedia by User:Itsmine, 2007) / Creative Commons CC BY-SA 3.0.
Animation link: Wikipedia.
File: Relativity file: light_speed_earth_moon.html.
Full caption: light_speed_earth_moon_short.html.