Officially, Oct. 21, 1879 is the day that Edison invented the light bulb.
Edison did not invent the light bulb. An incandescent light bulb was invented by British inventor Joseph Swan in 1845. The incandescent light worked by using electricity to heat a filament that would then glow with white light. The problem was the filaments would melt or not last long. By the 1870s, arc lighting was being used in lighthouses and as street lighting. In arc lighting, a spark “arcs” across two electrically charged rods. It was not practical for other uses because it gave off too much energy and thus too much light. Edison took on the task of inventing a cheaper, more efficient type of incandescent lighting. At first, he concentrated on a switch that would turn the filament on and off when it got too hot. It was a dead end, so Edison brought in Princeton physicist Frank Upton to reboot. Upton focused on the filament and eventually came up with one that burned for forty hours. It is a myth that Edison discovered this filament by himself in his laboratory and then watched it burn for the forty hours. This was supposedly on October 21, 1879, which became known as “Electric Light Day”. The story was invented by a newspaper reporter. Uncle Lost pp. 101-102
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