One of the most fascinating experiences that our technological civilization has left behind is the sensation of darkness. When humanity lived around a fire, the feeling of abandonment, of fear of what moves in the dark, was in the deepest part of the culture. With the arrival of gas lighting and, above all, electric lighting, we humans lost the meaning of darkness. Only rarely do we realize the meaning of twilight, the end of the day.
One of the main architects of this death was the brilliant Thomas Alva Edison, a choleric man, greedy for money , prone to stealing ideas and pitiful father and husband . Gas lighting did not provide enough light to break the darkness and the danger of fire and explosion was always present. Scientists knew that when electric current circulated through a conductive thread, it heated up. Could you take it to incandescence and make it glow? During the first half of the 19th century some thirty inventors tried and failed .
The bulbs did come on, but not long enough. Among those who tried it was the British physicist Joseph Swan , who built one made from carbonized paper filaments in a vacuum glass bulb in 1860, but failing to draw a good vacuum and the poor quality of the electrical supply caused the bulb to fail. had a very short shelf life .
He kept working on it, and on December 18, 1878, he showed his lamp, which used a very thin carbon rod, at a meeting of the Newcastle Chemical Society. Swan continued to do research to improve the light bulb and make it commercially viable and in 1880 his house was the first in the world to be lit by a light bulb . In 1881 he installed his light bulbs in the Savoy Theater in Westminster, the first public building in the world to be lit entirely by electricity. From there to jumping into the street there was only one step: the first street lit with an incandescent light bulb was Mosley Street in Newcastle Upon Tyne on February 3, 1879.
But the race was not over. The challenge was not to invent a light bulb, but to develop a commercially viable one. And this is where Thomas Alva Edison appeared.
In 1878 Edison was 31 years old and considered the greatest and greatest inventor of modern times. When he announced to the world that year his intention to solve the problem of the incandescent light bulb, the whole world rejoiced. They had so much faith in him that shares of gas lighting companies fell on the New York and London stock exchanges.
There is no doubt that Edison was a genius, although genius, as he said, is 1% inspiration and 99% perspiration. Inventing required hard and steady work. The development of the electric light bulb demanded a lot from Edison : he had underestimated the difficulties. For a while it looked like it was going to fail. Hell-bent on using platinum threads, it took him a year and $50,000 to realize his mistake. Hundreds of experiments later, he found a thread that glowed without melting or breaking .
Paradoxically, it was not a metal, but a fragile filament of burned cotton, or what is the same, a fine carbon thread, just like Swan did. The first success was on October 22, 1879: the light bulb was on for 13 and a half hours. Edison continued to improve on this design, and on November 4, 1879, applied for a patent for an electric lamp that used “a coiled and connected carbon filament or strip.” Although the text described various ways of creating such a filament, which included the use of ” cotton and linen thread, wooden slats, papers rolled in various ways”, Edison later discovered that the best was a carbonized bamboo filament: the light bulb could shine for more than 1,200 hours.
The joy in Menlo Park, the small Californian town where Edison had set up his ‘invention factory’, was indescribable. On New Year’s Eve, Edison unleashed the final fireworks: on the last night of the year 1879, the main street of Menlo Park was illuminated with electric current . Journalists from all over the world joined the inhabitants of that little town and sang wonders about the greatest inventor in all of history.
Curiously, behind the invention of the light bulb we find another very little known but striking discovery by Edison: being an eminently practical man, he made a theoretical discovery that, curiously, in the future was going to have a great technological implication.
It all started when Edison decided to improve the efficiency of his light bulb. In particular, he wanted to find a filament that would last longer before breaking. As usual, he tried everything he could think of, including an apparently silly idea of attaching a metal wire to the bulb where he had drawn the vacuum . Now, this cable was placed close to the filament, but without actually touching it.
Edison turned on the bulb to see if the presence of the metal wire somehow preserved the filament from breaking. It did not, but he did observe something very curious: a weak electric current flowed from the filament to the wire through the vacuum .
Of all Edison’s vast practical knowledge of electricity there was nothing that could explain such an extraordinary discovery. The brilliant inventor wrote it down in his notebook and in 1884 Edison’s entrepreneurial mind told him to patent it. The phenomenon is called the Edison effect .
Unfortunately, the genius of Menlo Park forgot about this curious phenomenon. Today we know that this current is the product of a weak flow of electrons between the filament of the light bulb and the metal one. Some time later, when we were able to modify and amplify this shower of electrons in a vacuum and, incidentally, control the behavior of the electric current with much greater precision, the apparently useless Edison effect opened the door to the development of the first vacuum tube . With it, the era of electronics began .