When a light bulb appears above someone’s head in a cartoon, that’s the visual shorthand for inspiration. How nice, then, to find out that the actual story of its invention is as extraordinary as it appears to be on the surface. In the course of only four years Edison and his talented crew developed everything about electrical power: the lamp itself, the vacuum pumps to build it, improved generators, switches, fuses, sockets, insulation, even the proper topology of power distribution. For someone who thought that invention was only 1% inspiration, he sure had a lot of it.
Others had also invented lamps, most notably Joseph Swan in Britain, but it was Edison who solved the key problems of bulb longevity and economical power distribution, and it was he who actually got the systems working.
The book can be found here. Its historian authors, Robert Friedel of U. Maryland and Paul Israel of Rutgers, have gone through the original lab notebooks to reconstruct the timeline of the whole venture. It looks about like this:
- Sep 1878 – Start. He has a vision of how to build a durable incandescent bulb by regulating the current to keep the filament from melting. He tells a reporter, files patents, and starts rounding up funding. He is only 31, but has already invented multiplex telegraphy, the carbon microphone, and the phonograph, any one of which would have made his reputation. The investors in gas lighting companies are terrified of him, and quickly put together a company to back him and control him. They also provide a cost target – he has to beat the cost of gas.
- Dec 1878 – Abandons the regulator idea; it was a mistake. Works instead on understanding the thermal properties of platinum, since it has a high melting point and doesn’t oxidize, and also on improving generators. Changing magnetic fields induce eddy currents in the iron plates that guide the fields and lose too much power. In a casual side note he invents the circuit breaker.
- February 1879 – A key insight – they need better vacuums than they get from existing pumps. They invent their own. An even more important insight is that light bulbs have to have high resistance, like 100 ohms, and have to be put in parallel. Everyone else was working with low resistance like 1 ohm, and high currents. That means the wires leading to the bulb have to be thick and/or short to avoid losses in the wires. That kills the cost. Parallel connections mean that one bulb can fail without bringing down the system. Christmas tree lights are connected in series, and they do in fact fail when one bulb loses its filament.
- May 1879 – first bulbs with platinum filaments are working. They tried lots of other metals, but platinum is best. They start assaying minerals from various sites around the global looking for cheap supplies.
- Oct 1879 – A long-lived bulb is made with a high-resistance piece of carbonized cotton thread in a high vacuum. Those were all the key elements, and it was achieved in only 13 months. Platinum was another mistake – it would never have been cheap enough.
- Dec 1879 – A demo for the public on New Year’s Eve. Hundreds of people braved the cold in rural New Jersey to see it. Strings of lights are run around the lab in Menlo Park and inside the house. Edison dunks a bulb underwater to show that it keeps burning. It’s a sensation, and is reported around the world.
- April 1880 – The first sale happens after only 20 months – a lighting system is installed on the steamship Columbia, the property of a railroad tycoon. It’s a perfect test bed, since it already has a power plant and wires can be easily strung throughout the ship. It’s also the first income for all this expensive research. And it’s a floating billboard for incandescent lighting! The crew devises sockets to hold bulbs securely, switches in the sockets, and fuses in case of shorts.
- July 1880 – The discovery of bamboo for the lamp filament. They tried carbonizing a zillion different materials, but bamboo threads kept stable after carbonizing and were nicely uniform.
- Sep 1880 – Production. The lab becomes a factory for making the key components.
- Dec 1880 – Permits. The streets of New York are going to have to be dug up to install all these cables, and the city council will have to approve it.
- 1881 to summer 1882 – 80,000 feet of cables are installed in the streets of lower Manhattan. No one knows how to make insulation that will last underground, so they invent one. The world’s first permanent power station is built at 255 Pearl Street. Edison has another key insight – a tree topology of wires from the station to each light bulb won’t work. That is, having a main trunk that splits off into smaller and smaller wires until it reaches the bulbs will need a huge amount of copper in the main trunk coming out of the station to avoid resistive losses. Instead he devises a “feeder and main” system, where the sub-trunks are all connected together in rings. That lets there be multiple paths to each bulb, saving huge amounts of wire.
- Sep 1882 – Pearl Street is turned on. Manhattan starts to glow, and hasn’t stopped since.
So that’s 4 years from concept to public rollout of one of the most significant inventions ever. It was done with one CTO/CEO, about five engineers, and 20 technicians. Here they are in 1879, with Edison the grim one holding a hat in the center of the third row:
Now, it didn’t take long for the rest of the inventing world to jump into this same field. Everyone started tinkering with lights and power and motors. One of them was a black inventor (and also Civil War Union Navy lieutenant and poet) named Lewis Latimer, who increased the lifetime of filaments by putting a coating on them. Ultimately Edison was left behind in the further innovations, as everyone must be eventually. He didn’t contribute much to later lighting efforts, and lost the famous Battle of the Currents when Westinghouse’s AC beat out his DC power distribution. Even so, there were DC power stations in New York up until 2007, since they were good for elevators. His initial choice of 110V for his lightbulbs persists to this day.
So why was it Edison who got the light bulb when so many others tried? I’m afraid that in looking over this history, the answer is quite dull – he was smarter than anyone else. Because he already had a string of brilliant inventions, he was able to attract the staff needed to do an entire system design and was able to attract the financial backing to support it. Because he was a master of both mechanics and electrics, he could develop new machines like vacuum pumps, and new techniques like feeder-and-mains when hitting the inevitable roadblocks. Because he knew how the newspapers worked, he staged demos and fed stories to reporters to keep interest high and financing flowing, and that ultimately let him steam-roll the New York City Council into letting him tear up half their streets. His success wasn’t due to luck or ruthlessness or charm – it was straight-up ingenuity. He wasn’t a particularly nice guy, but he could really get it done.