Who really invented the light bulb?

Many people had a hand in the light bulb, and the answer you get depends on whether you mean first, first to work, or first to work for a whole city.

Long before Edison, Humphry Davy made light by heating platinum in 1802, a feat that was not practical but became the precedent for scores of experimenters over the next 75 years. In 1841 Frederick de Moleyns was granted the first patent for an incandescent lamp. In Britain Joseph Swan could demonstrate a working bulb by 1860, but without a good vacuum it did not last. When he repeated a lecture on 17 January 1879 with his lamp working, he had a vacuum lamp that functioned. In 1881 the Savoy Theatre in London was lit entirely by Swan bulbs, the first public building in the world to be lit entirely by electricity.

Edison's first successful test, on 22 October 1879, lasted 13.5 hours. Two influential historical accounts point less to the lamp than to the system around it. Friedel and Israel list four factors that let his version outstrip the others: an effective material, a better vacuum, a high resistance that made central power distribution economical, and the parts of a large-scale lighting system. Thomas Hughes put it more bluntly: Edison's business success came from developing an entire, integrated system of electric lighting.

The credit was fought over in courtrooms. In 1883 the US patent office ruled one of Edison's patents invalid because it rested on William Sawyer's earlier work, and in Britain the rivals simply merged into a company called Ediswan. Canada, for its part, still maintains that two of its own inventors, Henry Woodward and Mathew Evans, invented the bulb.