Last week New York City’s Con Edison brought to a conclusion one of the most bitterly fought technological debates of all time when it announced it would disconnect the last five customers in New York City receiving direct current electricity.
“They’re mostly small users,” said Robert McGhee, a spokesman for Con Edison, “nobody you ever heard of. One of them is a residence. They may have to provide their own power if they want to keep using direct current. But for us it wasn’t worth the expense.”
Thomas Edison, whose name the company bears, lost this battle long ago to Nikola Tesla, the Serbian immigrant who invented a motor that utilized the rival system, alternating current. Edison was not a gracious loser but his reputation survives pretty much intact. Meanwhile, Tesla has sunk into obscurity — although he did make a cameo appearance in the 2006 movie The Prestige (played by David Bowie). A $75,000 electric sports car recently marketed by Silicon Valley entrepreneur Martin Eberhard has been christened the Tesla Roadster. Still, the great electrical genius of the early 20th century remains largely forgotten — even though he pioneered the technology that is creating our “wireless world.”
The electric battery — the “Voltaic Pile — had been invented by Allessandro Volta in 1800. For the next 80 years it remained the only source of electric current and most new devices — the electric light, for example — were designed to take advantage of it. In 1882, Edison opened the Pearl Street Station in Lower Manhattan and started generating a few thousand kilowatts. The station employed a coal-driven steam engine, which fired the reciprocal motion of a piston engine. This back-and-forth movement produced something different, however — alternating current, in which the electrons are constantly shifting back and forth at a periodic frequency rather than moving all in one direction.
Alternating current did not seem useful, especially for driving the rotary motion of an electric motor. So Edison had to “rectify” the current by converting it to DC. This was done with a set of “brushes,” which bracketed the rotating shaft and only picked up the half of the current that was moving in the right direction. These metallic brushes were constantly arcing sparks, however, and wore out at a phenomenal rate.
Direct current also had other shortcomings. In particular, its voltage was used up in resistance from the transmission wires over very short distances. It could not be transmitted for more than a mile. This meant a city would have to be dotted with coal plants. The prospects for clean air were not very bright.
All this challenged the 26-year-old Tesla as he pursued a degree in electrical engineering in Budapest. Tesla noted the clumsy inefficiency of the brushes and asked his professors if it wasn’t possible to build a rotary engine that ran on alternating current. They told him it couldn’t be done — it would be akin to perpetual motion. But Tesla pursued the subject in his fertile brain. One day as he walked in the park in Budapest in 1882 the answer came to him in a vision. He said later the engine that appeared before him was as tangible as if it had been made from real metal.
The problem could be solved, he realized, by dispatching two currents in phases 90 degrees apart. (We now use three currents.) The wires would magnetize four metal terminals surrounding a magnetized shaft. When the magnet at 12 o’clock was positive, it would start the positive pole of the shaft rotating in a clockwise direction. At 3 o’clock the second phased current would create a north pole, pushing the shaft another quarter turn. When the north pole reached 6 o’clock, however, the first current would have reversed and this pole would also be magnetized north. At 9 o’clock, the second current would also reverse and be north again. Thus, two alternating currents, fluctuating back and forth at a regular rate (we use 60 cycles per second) would create the rotary action of an electric motor. After that, everything became easy.
Tesla worked for Edison’s fledgling electric company in Paris and excelled enough to be invited to New York, where he presented his ideas for an alternating current engine to the master. The rough-and-ready Edison didn’t much enjoy the well-mannered ways of the European immigrant, however, and they had a falling out over a bonus that Edison had promised Tesla but then didn’t deliver. Tesla was cast into the streets. He worked as a laborer, carrying his engine entirely in his head, until a few chance meetings put him in touch with George Westinghouse, the other electrical pioneer, who bought his patents. Westinghouse used alternating current to harness Niagara Falls and transmit the power to nearby cities — something that couldn’t be done with direct current. He also won a contract to illuminate the “City of Light” at the 1893 Chicago Columbian Exposition. Edison took up the challenge and the “War of the Currents” was on.
Edison played dirty at best, trying to terrify the public into believing AC was uniquely dangerous. (In fact, AC and DC are about equal.) His supporters electrocuted dogs at weekly press conferences and arranged for the first electrocution of a condemned murderer at Sing Sing. In 1903 Edison executed Topsy the Elephant at Coney Island’s Luna Park and made a motion picture of the event, distributing “Electrocuting an Elephant” as one of the first films to appear in theaters. (Coney Island belatedly erected a memorial to Topsy in 2003.)
Alternating current’s advantages proved far too great, however, and by the 1920s had clearly won out. Electrical generation was centralized at larger and larger power stations that could be cited in remote locations. Hydropower from distant dams could be transmitted across hundreds of miles. Only a few direct current operations remained in Manhattan.
Edison’s fame survived intact. He remained a national hero, dying in 1929 just after helping open Henry Ford’s Greenfield Village only a week before the stock market crashed. Tesla, on the other hand, became completely absorbed in the phenomenon of electromagnetic radiation. As early as 1890 he realized that the earth itself is a huge magnet and its electrostatic atmosphere can be used to transmit information and even electrical power. With the help of J.P. Morgan, he built an 18-story tower on Long Island designed to broadcast both radio signals and electrical energy across the globe. Unfortunately, no one was equipped to receive his signals. When Guglielmo Marconi demonstrated the first point-to-point broadcasts on a much more practical level a decade later, he received credit for inventing radio.
Tesla became lost in dreams of a world brought together by instant communications. He envisioned a world in which telephone calls, stock quotes, daily news stories, photographs and information of every kind could be instantly transmitted. By 1900 he had created remote-controlled vehicles that are the precursors of today’s guided missiles and Hasbro toys. He believed these weapons could be made so powerful they would put an end to war. He also believed a world brought together by instant information would learn to live in peace. Yet he never mastered Edison’s talent for commercializing his ideas. He lived in a series of New York hotels, rarely paying his bills and constantly pursued by creditors. Every year he would hold a press conference in which he would unveil his latest wonders, but reporters became more and more cynical. He died in poverty in 1943.
McGee, of Con Edison, says the utility is planning a ceremony when the last direct current customer is disconnected before the end of the year. “We’ve selected a 51-year-veteran employee to snip the wires,” he says. “It’s about as close to Thomas Edison as we’re going to get.”
Tesla, on the other hand, will not be represented.