Extending the scope of the theory of knowledge

The invention of the light bulb is without any doubt one of the major inventions of the nineteenth century. It changed life profoundly in that it made human activities independent of the natural light circumstances on a hitherto unknown scale. The idea of electric light goes back to Humphrey Davy. He discovered that an electric arc between two poles could produce light. This phenomenon, however, was rather unpractical for home applications and could not be an alternative to existing gas light. New ideas were explored on the basis of the theoretical work on heat production in resistant conductors. An electric current could heat a conductor to such an extent that it would glow white-hot. Joseph Wilson Swan was the first to construct an electric light bulb on these physical principles. It contained a thin strip of material (filament) in an oxygen-free environment to prevent the strip from burning. An electric current heated the strip. He had, however, serious trouble maintaining the vacuum in the light bulb. Thomas Edison was able to solve this problem and at the same time to construct stable enough carbon wire that could function as filament. On October 21, 1879, he illuminated an electric lamp that glowed continuously for 40 h. That was an enormous achievement in those days.