The UnMuseum - Who Invented the Lightbulb?
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.
Copyright Lee Krystek                    2002. All Rights Reserved.