Edison's incandescent lamp lit the world, but did he really invent it? (Copyright Lee Krystek, 2002.) Surprising Science: Who Invented the Lightbulb?

It was Thomas Edison in 1879, wasn't it? That's what many people think and were taught in school. Like most stories, however, there is a lot more behind the creation of this important and ubiquitous object than just Mr. Edison..

The story of the lightbulb really starts almost seventy years earlier. In 1806 Humphrey Davy, an Englishman, demonstrated a powerful electric lamp to the Royal Society. Davy's lamp produced its illumination by creating a blinding electric spark between two charcoal rods. This device, known as an "arc lamp," was impractical for most uses. The light, similar to that of a welding torch, was simply too bright to be used in residences and most businesses. The device also needed a tremendous source of power and the batteries which powered Davy's demonstration model were quickly drained.

As time went on, electric generators were invented that could feed the arc lamp's need for power. It found its way into applications where a brilliant source of light was needed. Lighthouses and public assembly areas were obvious uses. Later arc lamps were used in war to power huge searchlights used to spot enemy planes. Today you can see such searchlights lighting up the sky near movie theaters or at the opening of a new stores.

The Incandescant Light

Some 19th century inventors wanted to find a way to "subdivide" the light from Davy's arc lamp so that it could be used in the home and office. Other scientists thought that a completely new technique for making electric light held more promise. This method of generating light was known as "incandescence."

Scientists knew that if you took some materials and passed enough electricity through them, they would heat up. They also knew that if the material got hot enough, it would start to glow. The problem with this method of making light was that before long either the material would burst into flame or melt into a puddle. If incandescent light was to be made practical, these twin problems would have to be solved.

It occurred to inventors that one way to keep their incandescent "burners" from catching fire was to not let them come into contact with oxygen. Oxygen is a necessary ingredient in the combustion process. Since oxygen is in the atmosphere, the only way to keep it away from the burners was to enclose the burner in a glass container, or "bulb," and pump out the air. In 1841 a British inventor named Frederick DeMoleyns patented a bulb using just this technique in combination with burners made of platinum and carbon. An American named J. W. Starr also received a patent in 1845 for a bulb using vacuum in conjunction with a carbon burner. Many others, including an English chemist named Joseph Swan, improved and patented versions of bulbs using a vacuum with burners of various materials and shapes. None, however, proved practical for everyday use. Swan's lamp, for example, used carbonized paper that would quickly crumble after being lit a short time.

The brash, young inventor Thomas Alva Edison.

Edison Joins the Fray

It was obvious, though, that incandescent lighting would be a huge financial success if it could be perfected, so many inventors continued to work on finding a solution. It was into this environment that the brash, young, inventor Thomas Alva Edison entered the race to make-a-better-bulb in 1878. Edison was already world famous for having created and commercialized several items, including a better stock market ticker and the phonograph. In October of that year, after working on the project for only a few months, he declared to the newspapers "I have just solved the problem of the subdivision of the electric light." This rash pronouncement was enough to drive the stocks of the gas companies (whose lamps supplied the current form of lighting) down into the ground.

As it turned out, Edison's announcement was premature. He had an idea of how to solve the problems of the electric incandescent light, but had not yet perfected it. His idea was to enclose a platinum burner in a vacuum. When other inventors had done this the platinum melted, but Edison thought he had solved that problem by building a temperature-sensitive switch into the bulb that would cut off the current when the temperature got too high. This was a great idea, but unfortunately it didn't work. To keep the bulbs cool enough, the switches had to cut the current off very quickly. This resulted in a constant flickering which made the bulbs unusable (this same switching principle is currently used in Christmas tree bulbs to make them blink on and off).

It was soon obvious to everyone working on the incandescent light at Edison's Menlo Park laboratory that another approach was needed. Edison decided to hire a young physicist named

Francis Upton from Princeton University to work on the project. Up to this point Edison's staff had been trying idea after idea to get the bulb to work. Under Upton's guidance, they started looking at existing patents and research to try and avoid repeating other people's mistakes. The staff also started doing basic research on the properties of the materials they had been working with.

An Edison builb from 1879 that was used to light his Menlo Park laboratory. (Photo by Alkivar licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.)

One of the results of testing the properties of the materials was the realization that any burner chosen would have to have a high electrical resistance. All materials have an amount of electrical "friction" that resists electricity moving through it. This is known as the material's electrical resistance. Materials with high resistance more easily get hot when electricity passes through them. Edison soon realized that any good burner would have to have a high electrical resistance, otherwise too much electricity would be needed to warm the material to the point where it would give off light. This revelation meant that Edison's staff need only to test high-resistance materials to find the one they wanted.

This information also started Edison thinking about the electric lights not only as an end to themselves, but how they fit as part of a whole electrical system. How big would the generator need to be to light a neighborhood? What voltage should be delivered to a house?

By October of 1879 Edison's workers began to see some results. On the 22nd of that month a thin, cotton "carbonized" thread burned for some 13 hours during an experiment. Longer times were achieved by modifying the vacuum pumps and creating a better vacuum inside the bulb (less oxygen inside the bulb slowed the burning process). More carbonized organic materials were tested and Japanese bamboo proved to be the best. By the end of 1880 Edison's carbonized bamboo burners, now called filaments because they were fashioned into a long, thin thread, were burning in bulbs as long as 600 hours. The "filament" proved to be the best shape to increase the materials electrical resistance and physical strength.

The carbonized bamboo had a high resistance and fit well into Edison's scheme for building a whole electrical power system to provide lighting. By 1882 he had established the Edison Electrical Light Company which had a generating station located on Perl Street, providing New York City with electrical lighting. In 1883 Macy's in New York City became the first store to install the new incandescent lamps.

Edison Vs. Swan

Meanwhile over in England, Joseph Swan had again gotten involved in working on the lightbulb after he saw that new pumps made it possible to produce a better vacuum. Swan made a lamp which worked well for demonstrations, but was impractical in actual use. Swan's burner was made of a thick carbon rod that gave off gases that soon covered the inside of the bulb in soot. Also, the low resistance of the rod meant that the bulb used up too much power. After seeing the success of a high resistance, thin filament in Edison's lamps, Swan incorporated this improvement into his own bulbs. After founding his own company in England, Swan found himself sued by Edison for patent infringement. Eventually the two inventors decided to stop fighting and join forces. The company they formed, Edison-Swan United, became one of the world's largest manufacturer of lightbulbs.

An early Edison power generation plant.

So did Edison invent the lightbulb? Not really. Others had produced an incandescent light before him. He did, however, create the first practical lightbulb along with an electrical system to support it, certainly a significant achievements in their own right.

Of all the inventions Edison was involved in - the stock ticker, the phonograph, the telegraph and the mimeograph - only the incandescent lightbulb remains in general use today. It is a testament to how great a job Edison and his workers at Menlo Park did in taking this invention out of the laboratory and putting it into the home.

A Partial Bibliography

They All Laughed by Ira Flatow, HarperCollins Publishers, 1992.

Lamp Inventors 1880-1940: Carbon Filament Incandescent , National Museum of American History, Smithsonian Institution, C:\My Documents\unmuseum\lightbulb\Lighting A Revolution Joseph W_ Swan.htm, 2002.