Edison , Thomas Alva

(1847–1931) American physicist and inventor

Edison was born in Milan, Ohio, and was taught at home by his mother – he had been expelled from school as ‘retarded’, perhaps because of his deafness. From the age of seven he lived in Port Huron, Michigan, and when he was twelve years old began to spend much of his time on the railroad between Port Huron and Detroit, selling candy and newspapers to make money. However, he was also fascinated by the telegraph system, designing his own experiments and training himself in telegraphy. He became a casual worker on telegraphy (1862–68), reading and experimenting as he traveled. At the age of 21 he bought a copy of Faraday's Experimental Researches in Electricity and was inspired to undertake serious systematic experimental work.

While Edison was living in a Wall Street basement (1869) he was called in to carry out an emergency repair on a new telegraphic gold-price indicator in the Gold Exchange. He was so successful that he was taken on as a supervisor. Later he remodeled the equipment and, soon after being commissioned to improve other equipment, his skill became legendary.

For a while Edison had a well-paid job with the Western Union Telegraph Company, but he gave it up to set up a laboratory of his own at Menlo Park, New Jersey. This he furbished with a wide range of scientific equipment, costing $40,000, and an extensive library. He employed 20 technicians and later a mathematical physicist. The laboratory was the first organized research center outside a university and produced many inventions. In 1877 Edison became known internationally after the phonograph was invented. His original instrument used a cylinder coated with tinfoil to record sounds, and was not commercially practical. In 1878, after seeing an exhibition of glaring electric arc lights, he declared that he would invent a milder cheap alternative that could replace the gas lamp. Because of his past successes, he managed to raise the capital to do this and the Edison Electric Light Company was set up. It took 14 months to find a filament material but by October 1879, Edison was able to demonstrate 30 incandescent electric lamps connected in parallel with separate switches. Three years later a power station was opened in New York and this was the start of modern large-scale electricity generation. Edison later merged his electric-light company with that of Joseph Swan who developed the carbon-filament light independently. Also in his work on incandescent filaments, Edison discovered that a current flows in one direction only between the filament and a nearby electrode. The use of thisEdison effect in the thermionic valve was independently achieved by J.A. Fleming. In 1887 Edison's laboratory moved to larger premises in West Orange, now a national monument. In his lifetime he took out over 1000 patents covering a variety of applications, including telephone transmission, cinematography, office machinery, cement manufacture, and storage batteries. No other inventor has been so productive.