The German clockmaker Johann Heinrich Goebel invented the incandescent lamp in 1854. Thomas Edison developed the concept and turned it into a useable product in 1879. For many years artificial light hung by a delicate carbon thread, now replaced by a stronger metal filament. Lamps have undergone a process of continual improvement; new ways of generating light have been invented and new materials have been used.
The light from an incandescent lamp is produced with the aid of an electrical current that causes the metal filament to glow. Around five percent of the electrical energy is converted into light, the rest is given off to the environment as heat.