*August 28, 2024* # The Edison Effect [](https://en.wikipedia.org/wiki/File:Livermore_Centennial_Light_Bulb.jpg) > The [Centenial Light](https://en.wikipedia.org/wiki/Centennial_Light): the oldest continuously running lightbulb I'm reading a book called *The Scientists Behind The Inventors*^[https://www.amazon.com/Scientists-Behind-Inventors-scientists-contributions/dp/B0007EGEZY]. I found it in one of those small library boxes in someone's front yard. It has a lot of really cool anecdotes about the interplay between mechanical invention and the discovery of scientific principles. The opening chapter described a series of events that took place at the Edison Company, and tells a story where noticing something small was integral to several big discoveries and inventions. In the late 1880's The Edison Company was developing the incandescent lightbulb. It was great; they got a device to make light by running current through a filament, enclosed in a glass bulb to create a vacuum. You know what lightbulbs are. Edison and his team noticed that a dark tinge would develop on the inner surface of the bulbs as they were used. This was annoying to Edison, because it blocked light, and made the lightbulb worse. It was an annoyance to eliminate. John Ambrose Flemming, a physicist and consultant at the Edison Company found the effect very interesting. He sensed that there were deeper implications worth investigating. He devised experiments. His apparatus was like a lightbulb filament and a charged piece of metal to capture particles jumping off the filament, enclosed in a vacuum. He found that the particles were negatively charged, because a positive piece of metal would catch them.^[Curiously wikipedia attributes the inquiry and apparatus to Edison himself, while this book says that it was Flemming. I'm sticking with the book's narrative here. ] [](https://en.wikipedia.org/wiki/File:EdisonEffect-side-by-side.svg) > From The [Edison Effect Wikipedia](https://en.wikipedia.org/wiki/Thermionic_emission). Elections jump across the gap from the filament when current is applied, dislodging carbon particles. Flemming wrote: > *It seemed at the time too trifling to notice. But in science it is the trifles that count. The little things of today may develop into the great things of tomorrow.* He continued to investigate the effect after the lightbulb project. At some point, it occurred to him that he had built a *valve* through which only negative signals would pass. If this were hooked up to an alternating current, he realized it would convert it into a direct current. He also realized that it could also interact with radio signals. This train of thought, and JJ Thomson's independent discovery of the electron, led eventually to the the *Flemming valve*, a kind of vacuum tube. It had far reaching implications for future technologies like radio broadcasting and power transmission. In addition the Flemming tube was surely a necessary precursor to the triode vacuum tube used in early computers like [ENIAC](https://en.wikipedia.org/wiki/ENIAC). It was one of those cases where a little detail was the gateway into a new universe of possibility. *Note: if this is in your wheelhouse, I scanned the bibliography for the first section [[scientists behind inventors bibliography.pdf|here]].*