|~ October 21, 1879 ~|
Thomas Edison didn't invent the light bulb, but he did invent a practical, useful incandescent light system that became the world standard. The light bulb already existed in several forms before Edison, however none of them were as good as Edison's version. In the book Edison's Electric Light: The Art of Invention the authors state that there were many electric lights, and some electric light bulbs, that existed before Edison. Probably the first true electric light bulb was created in 1841, when English inventor Frederick de Moleyns applied for and received the first patent for an incandescent lamp. The design using platinum wires contained within a vacuum bulb. Platinum, because of its extremely high melting point. Platinum also has a very high price so such a bulb would never have been viable commercially.
There were as many as 22 other light bulbs produced before Edison's. What made Edison's special? According to Edison's Electric Light: The Art of Invention:
...he stood alone in his appreciation of the essential requirements, set his goals accordingly, overcame many obstacles that stalled his rivals, and developed not only a practical lamp, but the associated components, such as improved generators and other hardware, that made large-scale lighting possible. And then he built the system.
On New Year's Eve, 1879, Thomas Edison put his carbon filament lamp on display at his laboratory in Menlo Park. It wasn't just a bulb, but a complete lighting system with all components ready to go. He had been working on the project since 1878.
The most common answer to this question is 1879. It is typically said that Edison invented the light bulb on October 21st of that year. However, it is misleading to say this. It is misleading to say that Edison invented the light bulb on October 21, 1879 because the light bulb was not his own original idea and because he did not simply come up with it on that day.
The idea of the light bulb had been around for a long time before 1879. For example, Sir Humphry Davy had experimented with ways of making light from electricity as early as 1802. Thus, we cannot say that Edison simply invented the light bulb on his own. Instead, he was one of many people who were trying to perfect an idea that already existed.
In addition, Edison did not simply come up with the idea on October 21, 1879. He had been working on his light bulb since 1877. He had been trying to come up with a material that could be used as a filament for the light bulb without burning out too quickly. He tried many different substances. It was in October of 1879 that he tried a carbonized cotton filament. On October 19, he tested such a filament and it burned continuously until it burned out on October 21. It is for this reason that October 21, 1879 is typically given as the date that Edison invented the light bulb.
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