Nikola Tesla (10 July 1856 – 7 January 1943) was an inventor and a mechanical and electrical engineer. He is frequently cited as one of the most important contributors to the birth of commercial electricity and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries. Tesla's patents and theoretical work formed the basis of modern alternating current (AC) electric power systems, including the polyphase system of electrical distribution and the AC motor, with which he helped usher in the Second Industrial Revolution. Born an ethnic Serb in the village of Smiljan, Croatian Military Frontier, in the territory of today's Croatia, he was a subject of the Austrian Empire by birth and later became an American citizen.[2] After his demonstration of wireless communication through radio in 1894 and after being the victor in the "War of Currents", he was widely respected as one of the greatest electrical engineers who worked in America.[3] Much of his early work pioneered modern electrical engineering and many of his discoveries were of groundbreaking importance. During this period, in the United States, Tesla's fame rivaled that of any other inventor or scientist in history or popular culture,[4] but due to his eccentric personality and his seemingly unbelievable and sometimes bizarre claims about possible scientific and technological developments, Tesla was ultimately ostracized and regarded as a mad scientist.[5][6] Tesla never put much focus on his finances. It is said he died impoverished, at the age of 86.[7] The International System of Units unit measuring magnetic field B (also referred to as the magnetic flux density and magnetic induction), the tesla, was named in his honor (at the Conférence Générale des Poids et Mesures, Paris, 1960), as well as the Tesla effect of wireless energy transfer to wirelessly power electronic devices which Tesla demonstrated on a low scale with incandescent light bulbs) as early as 1893 and aspired to use for the intercontinental transmission of industrial power levels in his unfinished Wardenclyffe Tower project. Aside from his work on electromagnetism and electromechanical engineering, Tesla contributed in varying degrees to the establishment of robotics, remote control, radar and computer science, and to the expansion of ballistics, nuclear physics,[8] and theoretical physics. In 1943, the Supreme Court of the United States credited him as being the inventor of the radio.[9] A few of his achievements have been used, with some controversy, to support various pseudosciences, UFO theories, and early New Age occultism. Tesla was born to Serbian parents in the village of Smiljan, Austrian Empire near the town of Gospić, found in the territory of modern day Croatia. His baptismal certificate reports that he was born on 28 June (N.S. 10 July), 1856, to Father Milutin Tesla, a priest in the Serbian Orthodox Church, Metropolitanate of Sremski Karlovci and Đuka Mandić. His paternal origin is thought to be either of one of the local Serb clans in the Tara valley or from the Herzegovinian noble Pavle Orlović[10] His mother Đuka , daughter of a Serbian Orthodox Church priest came from a family domiciled in Lika and Banija, but with deeper origins to Kosovo. She was talented in making home craft tools and memorized many Serbian epic poems, but never learned to read.[11] Nikola was the fourth of five children, having one older brother (Dane, who was killed in a horse-riding accident when Nikola was five) and three sisters (Milka, Angelina and Marica).[12]:3 His family moved to Gospić in 1862. Tesla went to school in Karlovac. He finished a four year term in the span of three years.[13] Tesla then studied electrical engineering at the Austrian Polytechnic in Graz (1875). While there, he studied the uses of alternating current. Some sources say he received Baccalaureate degrees from the university at Graz.[14][15][16] However, the university claims that he did not receive a degree and did not continue beyond the first semester of his third year, during which he stopped attending lectures.[17][18][19][20] In December 1878 he left Graz and broke all relations with his family. His friends thought that he had drowned in Mura. He went to Maribor, (today's Slovenia), where he was first employed as an assistant engineer for a year. He suffered a nervous breakdown during this time. Tesla was later persuaded by his father to attend the Charles-Ferdinand University in Prague, which he attended for the summer term of 1880. Here, he was influenced by Ernst Mach. However, after his father died, he left the university, having completed only one term.[21] Tesla engaged in reading many works, memorizing complete books, supposedly having a photographic memory.[22] Tesla related in his autobiography that he experienced detailed moments of inspiration. During his early life, Tesla was stricken with illness time and time again. He suffered a peculiar affliction in which blinding flashes of light would appear before his eyes, often accompanied by hallucinations. Much of the time the visions were linked to a word or idea he might have come across; just by hearing the name of an item, he would involuntarily envision it in realistic detail. Modern-day synesthetes report similar symptoms. Tesla would visualise an invention in his brain with extreme precision, including all dimensions, before moving to the construction stage; a technique sometimes known as picture thinking. He typically did not make drawings by hand, instead just conceiving all ideas with his mind. Tesla also often had flashbacks to events that had happened previously in his life; this began to happen during childhood.[22] In 1880, he moved to Budapest to work under Tivadar Puskás in a telegraph company,[23] the National Telephone Company. There, he met Nebojša Petrović, a young, Serbian inventor who lived in Austria. Although their encounter was brief, they did work on a project together using twin turbines to create continual power. On the opening of the telephone exchange in Budapest, 1881, Tesla became the chief electrician to the company, and was later engineer for the country's first telephone system. He also developed a device that, according to some, was a telephone repeater or amplifier, but according to others could have been the first loudspeaker.[24] In 1882 he moved to Paris, France, to work as an engineer for the Continental Edison Company, designing improvements to electric equipment brought overseas from Edison's ideas. In the same year, Tesla conceived the induction motor and began developing various devices that use rotating magnetic fields for which he received patents in 1888. Soon thereafter, Tesla was awakened from a dream in which his mother had died, "And I knew that this was so".[25] After her death, Tesla fell ill. He spent two to three weeks recuperating in Gospić and the village of Tomingaj near Gračac, his mother's birthplace. On 6 June 1884, Tesla first arrived in the US in New York City[26] with little besides a letter of recommendation from Charles Batchelor, a former employer. In the letter of recommendation to Thomas Edison, Batchelor wrote, "I know two great men and you are one of them; the other is this young man." Edison hired Tesla to work for his Edison Machine Works. Tesla's work for Edison began with simple electrical engineering and quickly progressed to solving some of the company's most difficult problems. Tesla was even offered the task of completely redesigning the Edison company's direct current generators.[27] Tesla claims he was offered US$50,000 (~ US$1.1 million in 2007, adjusted for inflation)[28] if he redesigned Edison's inefficient motor and generators, making an improvement in both service and economy.[22]:54–57 Tesla said he worked night and day on the project and gave the Edison Company several profitable new patents in the process. In 1885 when Tesla inquired about the payment for his work, Edison replied, "Tesla, you don't understand our American humor," thus breaking his word.[29][30] Earning a mere US$18 per week, Tesla would have had to work for 53 years to earn the amount he was promised. The offer was equal to the initial capital of the company. Tesla then immediately resigned when he was refused a raise to US$25 per week.[31] Tesla, in need of work, eventually found himself digging ditches for a short period of time for the Edison company. He saw the manual labor as a terrible job, but Tesla used this time to focus on his AC polyphase system.[22] In 1886, Tesla formed his own company, Tesla Electric Light & Manufacturing. The initial financial investors disagreed with Tesla on his plan for an alternating current motor and eventually relieved him of his duties at the company. Tesla worked in New York as a common laborer from 1886 to 1887 to feed himself and raise capital for his next project. In 1887, he constructed the initial brushless alternating current induction motor, which he demonstrated to the American Institute of Electrical Engineers (now IEEE) in 1888. In the same year, he developed the principles of his Tesla coil and began working with George Westinghouse at Westinghouse Electric & Manufacturing Company's Pittsburgh labs. Westinghouse listened to his ideas for polyphase systems which would allow transmission of alternating current electricity over long distances. In April 1887, Tesla began investigating what would later be called X rays using his own single terminal vacuum tubes (similar to his patent #514,170). This device differed from other early X-ray tubes in that it had no target electrode. The modern term for the phenomenon produced by this device is bremsstrahlung (or braking radiation). We now know that this device operated by emitting electrons from the single electrode through a combination of field electron emission and thermionic emission. Once liberated, electrons are strongly repelled by the high electric field near the electrode during negative voltage peaks from the oscillating HV output of the Tesla Coil, generating X rays as they collide with the glass envelope. He also used Geissler tubes. By 1892, Tesla became aware of the skin damage that Wilhelm Röntgen later identified as an effect of X rays.