In the art and religion of Ancient Johto, the Sun God was always depicted as an Ampharos which carried the Sun at the end of its tail. It is not hard to see why. The light of an Ampharos' tail may not actually be bright enough to be seen from space (despite legends to the contrary) but it is no less dangerous to stare at than the Sun. Back when rebel leaders were punished by blinding, it was Ampharos who did the job. Indeed, many Ampharos wear tail coverings when not in battle, to avoid injuring their trainers or spectators from prolonged exposure to their light.
Although the Flash hidden machine (later developed into a technical machine) was derived from Ampharos' tail, Ampharos themselves must be taught to use it. When they enter a cave before this training, their light illuminates the cave as though it were daytime, drawing the fury of Golbat and Graveler who vastly prefer their dark homes. Most pokemon must be trained to emit a steady light; training an Ampharos to use Flash, however, is the art of training one to control it.
Ampharos' light, like that of the Sun, can illuminate as easily as it blinds. And while many fear it, sailors are grateful for Ampharos, for their bright tails are what enable lighthouses to guide them gently into harbors.