Most of the industrialized world is lit by electric lights
, which are used both at night and to provide additional light during the daytime. These lights are normally powered by the electric grid
, but some run on local generators, and emergency generators serve as backups in hospitals and other locations where a loss of power could be catastrophic. Battery
-powered lights, usually called "flashlights" or "torches", are used for portability and as backups when the main lights fail.
Types of electric lighting include:
- incandescent light bulbs
- arc lamps
- gas-discharge tubes, e.g., fluorescent lights, neon lamps, modern photographic flashes
- LEDss, including OLEDs
The total amount of artificial light is sufficient for cities to be easily visible at night from the air, and from space. This wasted light should not be confused with the light pollution
that burdens astronomers
and others, although it is the source of it.