i at least 7 artificial lights
The contents of this article: 1 Combustion 2 Natural 2.1 Celestial and atmospheric light 2.2 Terrestrial 3 Direct chemical 4 Combustion-based 5 Electric powered 5.1 Electron stimulated 5.2 Incandescent lamps 5.3 Electroluminescent (EL) lamps 5.4 Gas discharge lamps