Nikola Tesla (Serbian Cyrillic: Никола Тесла; 10 July 1856 – 7 January 1943) was a Serbian American[3][4][5][6] inventor, electrical engineer, mechanical engineer, physicist, and futurist best known for his contributions to the design of the modern alternating current (AC) electricity supply system.[7] Tesla gained experience in telephony and electrical engineering before emigrating to the United States in 1884 to work for Thomas Edison in New York City. He soon struck out on his own with financial backers, setting up laboratories and companies to develop a range of electrical devices. His patented AC induction motor and transformer were licensed by George Westinghouse, who also hired Tesla for a short time as a consultant. His work in the formative years of electric power development was involved in a corporate alternating current/direct current “War of Currents” as well as various patent battles. Tesla went on to pursue his ideas of wireless lighting and electricity distribution in his high-voltage, high-frequency power experiments in New York and Colorado Springs, and made early (1893) pronouncements on the possibility of wireless communication with his devices. He tried to put these ideas to practical use in his ill-fated attempt at intercontinental wireless transmission, which was his unfinished Wardenclyffe Tower project.[8] In his lab he also conducted a range of experiments with mechanical oscillators/generators, electrical discharge tubes, and early X-ray imaging. He also built a wireless controlled boat, one of the first ever exhibited. Tesla was renowned for his achievements and showmanship, eventually earning him a reputation in popular culture as an archetypal “mad scientist”.[9] His patents earned him a considerable amount of money, much of which was used to finance his own projects with varying degrees of success.[10]:121,154 He lived most of his life in a series of New York hotels, through his retirement. He died on 7 January 1943.[11] His work fell into relative obscurity after his death, but in 1960 the General Conference on Weights and Measures named the SI unit of magnetic flux density the tesla in his honor.[12] There has been a resurgence in interest in Tesla in popular culture since the 1990s.[13]

AC and the induction motor Drawing from U.S. Patent 381,968, illustrating principle of Tesla’s alternating current induction motor In late 1886 Tesla met Alfred S. Brown, a Western Union superintendent, and New York attorney Charles F. Peck. The two men were experienced in setting up companies and promoting inventions and patents for financial gain.[49] Based on Tesla’s patents and other ideas they agreed to back him financially and handle his patents. Together in April 1887 they formed the Tesla Electric Company with an agreement that profits from generated patents would go 1/3 to Tesla, 1/3 to Peck and Brown, and 1/3 to fund development.[49] They set up a laboratory for Tesla at 89 Liberty Street in Manhattan where he worked on improving and developing new types of electric motors, generators and other devices. One of the things Tesla developed at that laboratory in 1887 was an induction motor that ran on alternating current, a power system format that was starting to be built in Europe and the US because of its advantages in long distance high voltage transmission. The motor used polyphase current which generated a rotating magnetic field to turn the motor (a principle Tesla claimed to have conceived of in 1882).[50][51][52] This innovative electric motor, patented in May 1888, was a simple self-starting design that did not need a commutator, thus avoiding sparking and the high maintenance of constantly servicing and replacing mechanical brushes.[53][54] In 1888, the editor of Electrical World magazine, Thomas Commerford Martin (a friend and publicist), arranged for Tesla to demonstrate his alternating current system, including his induction motor, at the American Institute of Electrical Engineers (now IEEE).[55] Engineers working for the Westinghouse Electric & Manufacturing Company reported to George Westinghouse that Tesla had a viable AC motor and related power system—something to which Westinghouse had been trying to secure patents. Westinghouse looked into getting a patent on a similar commutatorless rotating magnetic field based induction motor presented in a paper in March 1888 by the Italian physicist Galileo Ferraris but decided Tesla’s patent would probably control the market.[56][57] Nikola Tesla’s AC dynamo-electric machine (AC Electric generator) in an 1888 U.S. Patent 390,721 In July 1888, Brown and Peck negotiated a licensing deal with George Westinghouse for Tesla’s polyphase induction motor and transformer designs for $60,000 in cash and stock and a royalty of $2.50 per AC horsepower produced by each motor. Westinghouse also hired Tesla for one year for the large fee of $2,000 ($52,700 in today’s dollars[58]) per month to be a consultant at the Westinghouse Electric & Manufacturing Company’s Pittsburgh labs.[59] During that year, Tesla worked in Pittsburgh, helping to create an alternating current system to power the city’s streetcars. He found the time there frustrating because of conflicts between him and the other Westinghouse engineers over how best to implement AC power. Between them, they settled on a 60-cycle AC current system Tesla proposed (to match the working frequency of Tesla’s motor), although they soon found that, since Tesla’s induction motor could only run at a constant speed, it would not work for street cars. They ended up using a DC traction motor instead.[60][61] War of Currents Tesla’s demonstration of his induction motor and Westinghouse’s subsequent licensing of the patent, both in 1888, put Tesla firmly on the “AC” side of the so-called “War of Currents,”[62] an electrical distribution battle being waged between Thomas Edison and George Westinghouse that had been simmering since Westinghouse’s first AC system in 1886 and had reached the point of all out warfare by 1888.[63][64][65] This started out as a competition between rival lighting systems with Edison holding all the patents for DC and the incandescent light and Westinghouse using his own patented AC system to power arc lights as well as incandescent lamps of a slightly different design to get around the Edison patent.[66] The acquisition of a feasible AC motor gave Westinghouse a key patent in building a completely integrated AC system, but the financial strain of buying up patents and hiring the engineers needed to build it meant development of Tesla’s motor had to be put on hold for a while.[67] The competition resulted in Edison Machine Works pursuing AC development in 1890 and by 1892 Thomas Edison was no longer in control of his own company, which was consolidated into the conglomerate General Electric and converting to an AC delivery system at that point. “Tesla Polyphase System” A Westinghouse display of the “Tesla Polyphase System” at Chicago’s 1893 Columbian Exposition At the beginning of 1893 Westinghouse engineer Benjamin Lamme had made great progress developing an efficient version of Tesla’s induction motor and Westinghouse Electric started branding their complete polyphase phase AC system as the “Tesla Polyphase System”, noting how they believed Tesla’s patents gave them patent priority over other AC systems.[68] In 1893, George Westinghouse won the bid to light the 1893 World’s Columbian Exposition in Chicago with alternating current, beating out a General Electric bid by one million dollars.[69] This World’s Fair devoted a building to electrical exhibits. It was a key event in the history of AC power, as Westinghouse demonstrated the safety, reliability, and efficiency of a fully integrated alternating current system to the American public.[70][71] At the Columbian Exposition, under a banner announcing the “Tesla Polyphase System”, Tesla demonstrated a series of electrical effects previously performed throughout America and Europe,[10]:76 included using high-voltage, high-frequency alternating current to light a wireless gas-discharge lamp.[10]:79 An observer noted: Within the room was suspended two hard-rubber plates covered with tin foil. These were about fifteen feet apart, and served as terminals of the wires leading from the transformers. When the current was turned on, the lamps or tubes, which had no wires connected to them, but lay on a table between the suspended plates, or which might be held in the hand in almost any part of the room, were made luminous. These were the same experiments and the same apparatus shown by Tesla in London about two years previous, “where they produced so much wonder and astonishment”.[72] Tesla also explained the principles of the rotating magnetic field in an induction motor by demonstrating how to make a copper egg stand on end using a device he constructed known as the Egg of Columbus.[73] Niagara and patents In 1893 Richard Dean Adams, who headed up the Niagara Falls Cataract Construction Company sought Tesla’s opinion on what system would be best to transmit power generated at the falls. Over several years there had been an off again – on again series of proposals and open competitions on how best to utilize power generated by the falls with many systems being proposed by several US and European companies including two phase and three phase AC, high voltage DC, and even compressed air. Adams pumped Tesla for information about the current state of all the competing systems. Tesla advised Adams that a two phased system would be the most reliable, and that there was a Westinghouse system to light incandescent bulbs using two phase alternating current. Based on Tesla’s advice and Westinghouse’s demonstration that they could build a complete AC system at the Colombian Exposition, a contract for building a two phase AC generating system at the Niagara Falls was awarded to Westinghouse Electric. A further contract to build the AC distribution system was awarded to General Electric.[74] The mid 1890s saw the conglomerate General Electric, backed by financier J. P. Morgan, involved in take over attempts and patent battles with Westinghouse Electric. Although a patent sharing agreement was signed between the two companies in 1896[75] Westinghouse was still cash strapped from the financial warfare. To secure further loans Westinghouse was forced to revisit Tesla’s AC patent, which bankers considered a financial strain on the company[76][77] (at that point Westinghouse had paid out an estimated $200,000 in licenses and royalties to Tesla, Brown, and Peck[78]). In 1897, Westinghouse explained his financial difficulties to Tesla in stark terms, saying that if things continue the way they were he would no longer be in control of Westinghouse Electric and Tesla would have to “deal with the bankers” to try to collect future royalties. Westinghouse convinced Tesla to release his company from the licensing agreement over Tesla’s AC patents in exchange for Westinghouse Electric purchasing the patents for a lump sum payment of $216,000;[79] this provided Westinghouse a break from what, due to alternating current’s rapid gain in popularity, had turned out to be an overly generous $2.50 per AC horsepower royalty.[59] American citizenship On 30 July 1891, at the age of 35, Tesla became a naturalized citizen of the United States,[80] and established his South Fifth Avenue laboratory, and later another at 46 E. Houston Street, in New York. He lit electric lamps wirelessly at both locations, demonstrating the potential of wireless power transmission.[81] In the same year, he patented the Tesla coil.[82] Tesla served as vice president of the American Institute of Electrical Engineers, the forerunner (along with the Institute of Radio Engineers) of the modern-day IEEE, from 1892 to 1894.[83] X-ray experimentation X-ray of a hand, taken by Tesla Starting in 1894, Tesla began investigating what he referred to as radiant energy of “invisible” kinds after he had noticed damaged film in his laboratory in previous experiments[84][85] (later identified as “Roentgen rays” or “X-Rays”). His early experiments were with Crookes tubes, a cold cathode electrical discharge tube. Soon after, much of Tesla’s early research—hundreds of invention models, plans, notes, laboratory data, tools, photographs, valued at $50,000—was lost in the 5th Avenue laboratory fire of March 1895. Tesla is quoted by The New York Times as saying, “I am in too much grief to talk. What can I say?”[86] Tesla may have inadvertently captured an X-ray image (predating Wilhelm Röntgen’s December 1895 announcement of the discovery of x-rays by a few weeks) when he tried to photograph Mark Twain illuminated by a Geissler tube, an earlier type of gas discharge tube. The only thing captured in the image was the metal locking screw on the camera lens.[10]:134 In March 1896, after hearing of Wilhelm Röntgen’s discovery of X-ray and X-ray imaging (radiography),[87] Tesla proceeded to do his own experiments in X-ray imaging, developing a high energy single terminal vacuum tube of his own design that had no target electrode and that worked from the output of the Tesla Coil (the modern term for the phenomenon produced by this device is bremsstrahlung or braking radiation). In his research, Tesla devised several experimental setups to produce X-rays. Tesla held that, with his circuits, the “instrument will … enable one to generate Roentgen rays of much greater power than obtainable with ordinary apparatus.”[88] Tesla noted the hazards of working with his circuit and single-node X-ray-producing devices. In his many notes on the early investigation of this phenomenon, he attributed the skin damage to various causes. He believed early on that damage to the skin was not caused by the Roentgen rays, but by the ozone generated in contact with the skin, and to a lesser extent, by nitrous acid. Tesla incorrectly believed that X-rays were longitudinal waves, such as those produced in waves in plasma. These plasma waves can occur in force-free magnetic fields.[89][90] On 11 July 1934, the New York Herald Tribune published an article on Tesla, in which he recalled an event that would occasionally take place while experimenting with his single-electrode vacuum tubes; a minute particle would break off the cathode, pass out of the tube, and physically strike him. “Tesla said he could feel a sharp stinging pain where it entered his body, and again at the place where it passed out.” In comparing these particles with the bits of metal projected by his “electric gun,” Tesla said, “The particles in the beam of force … will travel much faster than such particles … and they will travel in concentrations.”[91] Radio Wireless transmission of power and energy demonstration during his 1891 lecture on high frequency and potential Tesla’s theories on the possibility of the transmission by radio waves go back as far as lectures and demonstrations in 1893 in St. Louis, Missouri, the Franklin Institute in Philadelphia, Pennsylvania, and the National Electric Light Association.[92] Tesla’s demonstrations and principles were written about widely through various media outlets.[93] Many devices such as the Tesla Coil were used in the further development of radio.[94] In 1898, Tesla demonstrated a radio-controlled boat (U.S. Patent 613,809 —Method of an Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles). Tesla’s radio wave experiments in 1896 were conducted in Gerlach Hotel (later renamed The Radio Wave building), where he resided.[95] In 1898, Tesla demonstrated a radio-controlled boat—which he dubbed “teleautomaton”—to the public during an electrical exhibition at Madison Square Garden.[46] The crowd that witnessed the demonstration made outrageous claims about the workings of the boat, such as magic, telepathy, and being piloted by a trained monkey hidden inside.[96] Tesla tried to sell his idea to the U.S. military as a type of radio-controlled torpedo, but they showed little interest.[97] Remote radio control remained a novelty until World War I and afterward, when a number of countries used it in military programs.[98] Tesla took the opportunity to further demonstrate “Teleautomatics” in an address to a meeting of the Commercial Club in Chicago, while he was travelling to Colorado Springs, on 13 May 1899.[24] In 1900, Tesla was granted patents for a “system of transmitting electrical energy” and “an electrical transmitter.” When Guglielmo Marconi made his famous first-ever transatlantic radio transmission in 1901, Tesla quipped that it was done with 17 Tesla patents, though there is little to support this claim.[99] This was the beginning of years of patent battles over radio with Tesla’s patents being upheld in 1903, followed by a reverse decision in favor of Marconi in 1904. In 1943, a Supreme Court of the United States decision restored the prior patents of Tesla, Oliver Lodge, and John Stone.[100] The court declared that their decision had no bearing on Marconi’s claim as the first to achieve radio transmission, just that since Marconi’s claim to certain patents were questionable, he could not claim infringement on those same patents[101] (there are claims the high court was trying to nullify a World War I claim against the U.S. government by the Marconi Company via simply restoring Tesla’s prior patent).[100] Colorado Springs See also: Magnifying transmitter and Colorado Springs Notes, 1899–1900 A multiple exposure picture (one of 68 Colorado Springs images created by of Century Magazine photographer Dickenson Alley) of Tesla sitting in his laboratory with his “Magnifying transmitter” generating millions of volts. The 7-metre (23 ft) long arcs were not part of the normal operation and were produced for effect by rapidly cycling the power switch[102] Another Alley photograph at Colorado Springs documenting 3 lights receiving power by means of electrodynamic induction from an oscillator 60 feet (18 m) from the bulbs (placed on the ground outside the building to demonstrate they had no connection to the power source)[102] On 17 May 1899, Tesla moved to Colorado Springs, where he would have room for his high-voltage, high-frequency experiments;[24] his lab was located near Foote Ave. and Kiowa St.[103] He chose this location because the polyphase alternating current power distribution system had been introduced there and he had associates who were willing to give him all the power he needed without charging for it.[104] Upon his arrival, he told reporters that he was conducting wireless telegraphy experiments, transmitting signals from Pikes Peak to Paris.[citation needed] The 1978 book Colorado Springs Notes, 1899–1900 contains descriptions of Tesla’s experiments. On 15 June 1899, Tesla performed his first experiments at his Colorado Springs lab; he recorded his initial spark length at five inches long, but very thick and noisy.[24] Tesla investigated atmospheric electricity, observing lightning signals via his receivers. Tesla stated that he observed stationary waves during this time.[105] The great distances and the nature of what Tesla was detecting from lightning storms confirmed his belief that the earth had a resonant frequency.[106][107] He produced artificial lightning (with discharges consisting of millions of volts and up to 135 feet long).[108] Thunder from the released energy was heard 15 miles away in Cripple Creek, Colorado. People walking along the street observed sparks jumping between their feet and the ground. Sparks sprang from water line taps when touched. Light bulbs within 100 feet of the lab glowed even when turned off. Horses in a livery stable bolted from their stalls after receiving shocks through their metal shoes. Butterflies were electrified, swirling in circles with blue halos of St. Elmo’s fire around their wings.[109] While experimenting, Tesla inadvertently faulted a power station generator, causing a power outage. In August 1917, Tesla explained what had happened in The Electrical Experimenter: “As an example of what has been done with several hundred kilowatts of high frequency energy liberated, it was found that the dynamos in a power house six miles away were repeatedly burned out, due to the powerful high frequency currents set up in them, and which caused heavy sparks to jump through the windings and destroy the insulation!”[110] An Alley Colorado Springs photo of a grounded tuned coil in resonance with a transmitter illuminates a light near the bottom of the picture.[111] Tesla did not disclose how far away the transmitter was.[102][111] During his time at his lab, Tesla observed unusual signals from his receiver which he concluded may be communications from another planet. He mentioned them in a letter to reporter Julian Hawthorne at the Philadelphia North American on 8 December 1899[112] and in a December 1900 letter about possible discoveries in the new century to the Red Cross Society where he referred to messages “from another world” that read “1… 2… 3…”.[113][114] Reporters treated it as a sensational story and jumped to the conclusion Tesla was hearing signals from Mars.[113] He expanded on the signals he heard in a 9 February 1901 Collier’s Weekly article “Talking With Planets” where he said it had not been immediately apparent to him that he was hearing “intelligently controlled signals” and that the signals could come from Mars, Venus, or other planets.[115] It has been hypothesized that he may have intercepted Marconi’s European experiments in July 1899—Marconi may have transmitted the letter S (dot/dot/dot) in a naval demonstration, the same three impulses that Tesla hinted at hearing in Colorado[116]—or signals from another experimenter in wireless transmission.[117] In 1899, John Jacob Astor IV invested $100,000 for Tesla to further develop and produce a new lighting system. Instead, Tesla used the money to fund his Colorado Springs experiments.[118] On 7 January 1900, Tesla left Colorado Springs.[citation needed] His lab was torn down in 1904, and its contents were sold two years later to satisfy a debt.[119][120] The Colorado experiments had prepared Tesla for the establishment of the trans-Atlantic wireless telecommunications facility known as Wardenclyffe near Shoreham, Long Island.[121] Wardenclyffe years (1900–1917) Main article: Wardenclyffe Tower Tesla Ready for Business – 7 August 1901 New-York tribune article The Tesla coil wireless transmitter U.S. Patent 1,119,732 Tesla’s Wardenclyffe plant on Long Island in 1904. From this facility, Tesla hoped to demonstrate wireless transmission of electrical energy across the Atlantic. In 1900, with $150,000 ($4,266,600 in today’s dollars[58]; 51% from J. Pierpont Morgan), Tesla began planning the Wardenclyffe Tower facility.[122] Tesla later approached Morgan to ask for more funds to build a more powerful transmitter. When asked where all the money had gone, Tesla responded by saying that he was affected by the Panic of 1901, which he (Morgan) had caused. Morgan was shocked by the reminder of his part in the stock market crash and by Tesla’s breach of contract by asking for more funds. Tesla wrote another plea to Morgan, but it was also fruitless. Morgan still owed Tesla money on the original agreement, and Tesla had been facing foreclosure even before construction of the tower began.[117] In December 1901, Marconi successfully transmitted the letter S from England to Newfoundland, terminating Tesla’s relationship with Morgan.[improper synthesis?] Over the next five years, Tesla wrote over 50 letters to Morgan, pleading for and demanding additional funding to complete the construction of Wardenclyffe. Tesla continued the project for another nine months. The tower was erected to its full 187 feet (57 m).[117] In July 1903, Tesla wrote to Morgan that in addition to wireless communication, Wardenclyffe would be capable of wireless transmission of electric power.[122] On 14 October 1904, Morgan finally replied through his secretary, stating, “It will be impossible for [me] to do anything in the matter,” after Tesla had written to Morgan when the financier was meeting with the Archbishop of Canterbury in an attempt to appeal to his Christian spirit.[117] In June 1902, Tesla’s lab operations were moved to Wardenclyffe from Houston Street.[122] On his 50th birthday in 1906, Tesla demonstrated his 200 horsepower (150 kilowatts) 16,000 rpm bladeless turbine. During 1910–1911 at the Waterside Power Station in New York, several of his bladeless turbine engines were tested at 100–5,000 hp.[123] Tesla invented a steam-powered mechanical oscillator—Tesla’s oscillator. While experimenting with mechanical oscillators at his Houston Street lab, Tesla allegedly generated a resonance of several buildings. As the speed grew, it is said that the machine oscillated at the resonance frequency of his own building and, belatedly realizing the danger, he was forced to use a sledge hammer to terminate the experiment, just as the police arrived.[16]:162–164 In February 1912, an article—”Nikola Tesla, Dreamer” by Allan L. Benson—was published in World Today, in which an artist’s illustration appears showing the entire earth cracking in half with the caption, “Tesla claims that in a few weeks he could set the earth’s crust into such a state of vibration that it would rise and fall hundreds of feet and practically destroy civilization. A continuation of this process would, he says, eventually split the earth in two.”[91] Tesla theorized that the application of electricity to the brain enhanced intelligence. In 1912, he crafted “a plan to make dull students bright by saturating them unconsciously with electricity,” wiring the walls of a schoolroom and, “saturating [the schoolroom] with infinitesimal electric waves vibrating at high frequency. The whole room will thus, Mr. Tesla claims, be converted into a health-giving and stimulating electromagnetic field or ‘bath.'”[124] The plan was, at least provisionally approved by then superintendent of New York City schools, William H. Maxwell.[124] Before World War I, Tesla sought overseas investors. After the war started, Tesla lost the funding he was receiving from his patents in European countries. Eventually, he sold Wardenclyffe for $20,000 ($472,500 in today’s dollars[58]).[122] In 1917, around the time that the Wardenclyffe Tower was demolished by Boldt to make the land a more viable real estate asset, Tesla received AIEE’s highest honor, the Edison Medal.[125] In the August 1917 edition of the magazine Electrical Experimenter Tesla postulated that electricity could be used to locate submarines via using the reflection of an “electric ray” of “tremendous frequency,” with the signal being viewed on a fluorescent screen (a system that has been noted to have a superficial resemblance to modern radar).[126] Tesla was incorrect in his assumption that high frequency radio waves would penetrate water[127] but Émile Girardeau, who helped develop France’s first radar system in the 1930s, noted in 1953 that Tesla’s general speculation that a very strong high frequency signal would be needed was correct stating “(Tesla) was prophesying or dreaming, since he had at his disposal no means of carrying them out, but one must add that if he was dreaming, at least he was dreaming correctly.”[10]:266[128]