Thomas Edison

Thomas Alva Edison is considered one of the greatest inventors in history. He was born in Milan, Ohio on February 11, 1847 and died in 1931. During his life he patented 1,093 inventions. Many of these inventions are in use today and changed the world forever. Some of his inventions include telegraphy, phonography, electric lighting and photography. His most famous inventions were the phonograph and the incandescent light bulb.

Edison did some of his greatest work at Menlo Park. While experimenting on an underwater cable for the automatic telegraph, he found that the electrical resistance and conductivity of carbon varied accordingly to the pressure it was under. This was a major theoretical discovery, which enabled Edison to invent a "pressure relay" using carbon rather than magnets, which was the usual way to vary and balance electrical currents. In February of 1877 Edison began experiments designed to produce a pressure relay that would amplify and improve the audibility of the telephone, a device that Edison and others had studied but which Alexander Graham Bell was the first to patent, in 1876. By the end of 1877 Edison had developed the carbon-button transmitter that is still used today in telephone speakers and microphones.

Many of Thomas Edison?s inventions including the carbon transmitter were in response to demands for new products and improvements. In 1877, he achieved his most unique discovery, the phonograph. During the summer of 1877 Edison was attempting to devise for the automatic telegraph a machine that would transcribe a signals as they were received into a form of the human voice so that they could then be delivered as telegraph messages. Some researchers had theorized that each sound, if it could be graphically recorded, would produce a distinct shape resembling short hand, or phonography, as it was known then. Edison hoped to make this concept real by employing a stylus-tipped carbon transmitter to make impressions on a strip of paraffined paper. To his amazement, the barley visible indentations generated a vague sound when the paper was pulled back beneath the stylus.

In December 1877 Edison unveiled the tinfoil phonograph, which replaced the strip of paper wrapped in tinfoil. Many people would not believe what they were hearing including a leading French scientist who declared it to be a trick device of a ventriloquist. The public?s amazement was quickly followed by universal approval. Edison became famous all around the world and was dubbed the Wizard of Menlo Park, although ten years passed before the phonograph was transformed form a laboratory curiosity into a commercial product.

His most famous and most commonly used invention is the incandescent light bulb. American scientists including Samuel Langley needed a highly sensitive instrument that could be used to measure minute temperature changes in heat emitted from the Sun?s corona during a solar eclipse along the rocky mountains on July 29,1878. To please those needs Edison invented a "microtasimeter" employing a carbon button. This was a time when great advances were being made in arc lights so that electricity could be used for lighting in the same fashion as with small, individual gas "burners". The basic problem seemed to be to keep the burner, or the bulb, from being consumed by preventing it from overheating. Edison thought he would be able to solve this by coming up with a microtasimeter-like device to control the current. He proclaimed that he would invent a safe, mild, and inexpensive electric light that would replace the gaslight.

Inventors had been attempting to devise the incandescent light bulb for fifty years, but Edison?s reputation and past achievements commanded respect for his bold prediction. As a result, a group of leading financiers, including J.P. Morgan and the Vanderbilts, established the Edison Electric Light Company, and advanced him $30,000 for his research and development. Edison?s idea was to connect his lights in a parallel circuit by subdividing the current so that the failure of one light bulb would not cause the whole circuit to fail. Some well-known scientists predicted that such a circuit could never be possible, but their findings were based on systems of lamps with low resistance (the only successful type of electrical light at the time). Edison, however, determined that a bulb with high resistance would serve his purpose, and he began his search for a suitable one.

By the summer of 1879 Edison and Francis Upton had made enough progress