By Olivia B. Waxman
October 25, 2019

One irony of history is that while Thomas Edison invented the first practical and affordable light bulb, he didn’t invent a practical and affordable system for keeping those lights on nationwide. The distinction for developing the system for transporting electricity that way goes jointly to George Westinghouse, the inventor of the railroad air brake, and to Nikola Tesla, a visionary engineer from the Austrian empire.

In the 1880s, the three went to battle over who had the superior technology for electrical transmission. The three-way rivalry between the inventors is the premise of The Current War (a movie that has its own dramatic back story), starring Benedict Cumberbatch as Edison, Nicholas Hoult as Tesla and Michael Shannon as Westinghouse. Edison was promoting direct current (DC), while Westinghouse was promoting alternating current (AC). As the U.S. Department of Energy explains, direct current “runs continually in a single direction, like in a battery or a fuel cell,” while “alternating current reverses direction a certain number of times per second — 60 in the U.S. — and can be converted to different voltages relatively easily using a transformer.”

But the differences between the two went beyond their definitions.

“If we were living in Edison’s world, we’d have a large coal-operated generating plant every mile or two, because DC couldn’t travel any distance,” says Jill Jonnes, author of Empires of Light: Edison, Tesla, Westinghouse, and the Race to Electrify the World. (Jonnes was not involved in the film.) “The brilliance of AC was that you could send it long distances, bring the voltage down via another transformer station, and distribute it as needed out into the surroundings.”

On the other hand, DC systems were ahead of AC systems in terms of developing a motor. There was huge business potential for nailing the design of electric motors, in terms of the future of powering machines, factories and appliances. Tesla wanted to develop an AC-power motor, and had tried to get Edison on board when he worked for Edison in New York City in 1884; Tesla left after six months when it was clear that Edison wasn’t interested in that idea.

Edison wanted to keep proving his DC system was better, despite its drawbacks, so he zeroed in on the fact that alternating current operated at much higher voltages than direct current. Therefore, he reasoned, it must be more dangerous. As he wrote in 1886, “Westinghouse will kill a customer within six months after he puts in a system of any size.”

The following year, an opportunity was presented to show just how dangerous it was.

In 1887, Alfred Southwick, a member of a commission established by the New York State legislature to explore capital-punishment alternatives after a series of hangings gone awry, wrote to Edison asking if he had any thoughts. Edison was initially reluctant to respond because he had always opposed the death penalty, but saw an opportunity to discredit Westinghouse. He recommended alternating currents “manufactured principally” by Westinghouse as the “best appliance” for killing someone “instantaneously” with “the least amount of suffering.”

As TIME reported in a 2010 special issue about Edison’s work, Edison teamed up with fellow Westinghouse opponent Harold Brown, whose experiments at Edison’s laboratory in West Orange, N.J., determined that a dog could survive 1,000 volts of DC but would be killed by just under 300 volts of AC. During a press conference, Brown electrocuted a 76-lb. dog named Dash. Brown designed the first electric chair, and Edison helped him secure AC generators through a secondhand dealer.

At 6:40 a.m. on Aug. 6, 1890, in the Auburn State Prison in upstate New York, William Kemmler, who was convicted of murdering his common-law wife, was zapped with a 17-second jolt of 1,300 volts of electricity via AC, but didn’t die. Kemmler, visibly struggling to breathe, was given a charge of 2,000 volts. Four minutes later, the body caught on fire, and he was declared dead.

Despite Edison’s efforts, the incident was not enough to keep his opponent down.

After Tesla demonstrated his AC motor in 1888, Westinghouse bought up Tesla’s AC patents and hired him so he could commercialize the motor.

“Once Tesla solved the problem of creating a motor that could operate using AC, then it was clearly the superior tech,” says Jonnes.

Westinghouse’s company won the bid to electrify the Chicago World’s Fair in 1893. That dazzling spectacle ended the “War of the Currents.” That same year, Westinghouse’s company signed a contract to install AC generators at Niagara Falls, and in 1895, the first hydro-electric power plant launched there.

But Edison’s career as an inventor was far from over. His moving-picture camera and Kinetoscope viewer helped establish him as one of the inventors of movies.

And Edison did win out in terms of being the most remembered of the three in terms of household name recognition — at least until recently, when the introduction of Elon Musk’s Tesla electric cars gave him some competition. The cars, Jonnes adds, would be right up the real Tesla’s alley, as he loved the finer things in life. But ultimately, inventing things that are used every day proved key to Edison’s fame.

“The thing I always say about Edison, about why he is the most famous inventor,” she says, “is we all understand his inventions and we all get enormous pleasure out of them.”

Write to Olivia B. Waxman at olivia.waxman@time.com.

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