Nikola Tesla was one of the most important engineers of his time. Although he never received a university degree, he was one of the pioneers of radio, took some of the first X-ray photographs, constructed the first radio-controlled robots, and built the first AC power system. And yet, for all this, why is Tesla not remembered as a great engineer like his contemporaries Edison and Marconi? Why has Tesla's name become associated with pseudo-science, his work the province of bizarre cults and conspiracy theories¹? Why has Tesla's contribution to science been marginalised by orthodox history? This entry will attempt to answer some of these questions.

The Early Years

Nikola Tesla was born a Serb in the Croatian village of Smiljan on the stroke of midnight between 9 and 10 July, 1856. His father, Milutin Tesla was an Orthodox Christian priest. He taught his son how to strengthen his mind by rigorous memory and reasoning exercises. In later life Nikola would always claim that his talents came from his mother Djocetia. Although she had no education and was in fact illiterate, she created numerous inventions for household tasks. This ability - to create inventions without written plans - may have some bearing on Nikola's ability to visualize the complete plans for his inventions without ever having to put pen to paper.

Nikola had a brother, Dane, seven years his senior. Dane was considered to have the superior intellect in the family. His death when aged 12 seems to have affected Nikola deeply, although the story of his death seems to vary with each telling and has become a central part of the Tesla myth. In one version, Dane was thrown from a horse, which was panicked by Nikola firing a peashooter at it². In another version Dane claimed, on his deathbed, that he had been pushed downstairs by Nikola - a claim he strenuously denied³. The only first hand version of the story we possess (in Tesla's autobiography) merely states that Dane died from a fall from a horse. Whatever the cause of death, the incident affected Nikola profoundly. His parents' memories of Dane's educational brilliance and their conviction that he would have been a great man made Nikola deeply insecure about his own achievements.

The recollection of his [Dane's] educational attainments made every effort of mine seem dull by comparison. Anything that I did merely caused my parents to feel the loss more keenly.
Nikola Tesla, My Inventions

His parents' conviction of Dane's superiority spurred Tesla on to out-perform his brother's memory. This may explain his ferocious work rate. In adult life he would spend days working in his laboratory without eating or sleeping. Nikola's childhood seems to have been plagued by ill health. He suffered a strange affliction in which blinding flashes of light would appear before his eyes, often accompanied by hallucinations. A word or idea he came across triggered the visions. Just by hearing the name of an object he would experience it in great detail. This caused him great distress but by the time he had reached his teens he had taught himself to repress them and they did not occur except in times of great stress. This is the first sign we see of Tesla's gift for visualisation, although it started as a curse rather than a blessing⁴.

During his later years at high school Tesla became increasingly fascinated with the science of electricity. He expressed his desire to become an electrical engineer to his parents. Milutin forbade this, insisting that Nikola had a much better future following the family tradition and becoming a clergyman. However, Nikola contracted a very powerful form of cholera shortly after graduating from high school. He was bedridden for nine months and at one point his parents did not believe he would survive. Nikola's recovery did not begin until he pleaded with his father 'Perhaps I will recover if you let me be an electrical engineer.' Milutin relented in his opposition and granted what he thought was Nikola's final request⁵.

The Beginnings of AC Power

Tesla began his college education at the Graz Polytechnic Institute, pursuing study of the topic that fascinated him above all others: electricity. Tesla's desire to impress his parents (and, no doubt, to exorcise Dane's ghost) meant that he studied from 3am to 11pm every single day. It was while he was studying at Graz that he first began thinking about AC (alternating current, where the direction of current changes many times a second) power. Tesla saw that DC (direct current, where the direction of current stays the same) was inefficient and incapable of transmitting power over long distances. There are two reasons why this is so.

• With DC, there is a progressive loss of power the further one gets from the source. This is because of electrical resistance. Electrons travelling in a conductor do not travel in straight lines as they collide with the atoms in the conductor. This creates resistance, and the electrical energy is dissipated as heat. Therefore, the longer the conductor, the more electrical energy would be dissipated as heat. As such, DC power stations had a useful range of only one or two miles.

• DC current could not be modified once it had left the power station. This is important because for electricity to be used efficiently it needs to be generated with low voltage and high current (to prevent sparking), transmitted at high voltage and low current (so there is little heating loss) and converted back to low voltage for use in the home (to prevent electrocution).

AC solves these problems in the following manner:

• The fact that the direction of AC changes many times a second creates a fascinating side effect known as the 'skin effect'. This means that the current only flows through the surface of the wire. As such, losses due to resistance are greatly reduced and AC power stations have a much greater range.

• AC can have its voltage and current stepped up or down by means of a device known as a transformer. This is a pair of coils, usually wrapped around an iron ring. The current to be stepped up (or down) is passed through one coil and the stepped current is picked up by the other by means of electromagnetic induction. The amount by which this happens is determined by the number of turns on each coil, and this cannot be done with DC.

Unfortunately, Tesla's professors poured scorn on the idea of AC as a practical system, pointing out that no one had ever made it work. The main problem was that the constant switching of the direction of current produced violent vibrations which affected the efficiency. This did not discourage Tesla, who continued to think about the problem throughout his time at Graz⁶.

Tesla's sophomore year at Graz was interrupted by his father's stroke. Nikola returned to Smiljan and his father died soon after. Lacking funds for tuition, he had to abandon his study at the Polytechnic Institute. Instead, Tesla was intrigued by the news that the government was planning to install a telephone system in Budapest. Tesla travelled to the capital in the hope of securing a position. Unfortunately, he discovered that the telephone exchange was still very much in the planning stage, so he had to resign himself to taking a very poorly paid job at the government telegraph office. By this point the stresses of his life seem to have brought on a complete nervous collapse. This manifested itself in the form of extreme hypersensitivity. The ticking of a watch three rooms away was painfully deafening. Rubber cushions had to be inserted underneath the legs of his bed to dampen vibrations because the footsteps of passers-by seemed like earthquakes to him. Exposure to light was painful not only to his eyes but to his skin as well⁷. Only what Tesla referred to as 'a powerful desire to live and continue the work [on AC]'⁸ permitted his recovery.

Although he recovered, this collapse left Tesla with odd behavioural traits that would last the rest of his life. His behaviour manifested symptoms of obsessive-compulsive disorder. For instance, he required that any repeated action in his life (eg the number of steps in a walk) to be exactly divisible by three. He also felt compelled to measure his food and calculate its exact volume before eating it⁹. Saltine crackers were apparently a particular favourite because of their uniformity of volume. He also used to demand 12 fresh towels to clean his hands at each meal. From this point on, there is no record of Tesla ever having a romantic relationship.

As part of his convalescence Tesla took to walking in Budapest Park with an assistant of his called Szigeti. A extract from Goethe's Faust about the sunset came to mind and Tesla began to recite:

The sun shudders and shimmers, having survived the day, and moves on to stir new life, Oh, that no wings there to lift me from the ground to reach, to follow. But, as a beautiful dream, it's gone. Oh, the spirit wings fade, and no wings of flesh come to take their place
¹⁰.

The solution to the problem of AC came to him in a sustained flash of inspiration. His solution was two coils positioned at right angles and supplied with alternating currents 90° out of phase with each other could make a magnetic field rotate. This in turn could make the rotor of a motor rotate. It is best here to consider the analogy of a car engine. With one cylinder, the oscillating motion would produce vibrations. However, if two cylinders out of step with each other are used, the vibrations cancel each other out as they reach the top and bottom of their strokes in a synchronised manner. The propensity for turning ideas into concrete visualisations, which had tormented Tesla in his youth, was now turned to his advantage. This discovery led to a prolonged surge of inspiration, which Tesla described in his autobiography as:

A mental state of happiness about as complete as I have ever known in my life. Ideas came in an uninterrupted stream and the only difficulty I had was to hold them fast... In less than two months I evolved virtually all the types of motors and modifications of the systems which now identified with my name.
Tesla, 1985.

Unfortunately, no one in Budapest was interested in his new power system. However, Szigeti was acquainted with a firm in Paris, which was looking for electrical engineers and wrote Tesla a letter of introduction. This was the Continental Edison Company, a French company, which manufactured and sold motors, dynamos and lighting systems under licence from Thomas Edison. The company had great faith in Tesla's ability as an engineer. He was employed as the company trouble-shooter, tackling the company's most difficult problems. One of the most difficult problems he was given was to fix the lighting system and powerhouse of Strasbourg railway station. It was during the months of work at the railway station (extended not by Tesla's lack of engineering abilities - for he was highly competent - but by local bureaucratic incompetence) that Tesla built his first AC motor and dynamo. The system worked first time, without Tesla ever having to make a single engineering drawing. After his work at the railway station was completed, Tesla returned to Paris and attempted to collect the bonus that was due to him for fixing the problem. He spent the next few weeks being referred from one company director to another until he realised that no bonus would be forthcoming. Attempts to raise capital having also come to nothing, Tesla decided, under the advice of Continental Edison's chairman, to travel to America and work for Thomas Edison.

Edison and The War of the Currents

It was 1884 and Tesla used all his savings to buy himself a ticket to New York and left on the first available boat. On arrival, he immediately began working for Edison. Although he had little confidence in AC, regarding it as a pipe dream, Edison was quickly impressed at Tesla's skill at trouble-shooting and his ferocious work-rate. Tesla, as usual, started at 10.30am and finished at 5.30am the following morning. Tesla's attitude towards Edison at the beginning of their working relationship seems to have been little short of hero worship, which, given Edison's well known egotism, could only have helped him warm towards Tesla. Eventually Tesla was presented with a challenge. If he could increase the efficiency of the DC dynamos by 25% Edison would present him with a bonus of $50,000. A two-month deadline was imposed and Tesla kept to it, improving the efficiency of some dynamos by up to 50%.

Unfortunately, Tesla hadn't reckoned on Edison's notoriously tight-fisted nature. He reneged on the deal and refused to hand over the money. Tesla, infuriated at being betrayed by his idol, quit in disgust¹¹. It was at this point that he was approached by a group of investors interested in developing an arc light that he had invented. He went into partnership with them as the Tesla Arc Light Company. The arc lights sold well and Tesla expected to have enough money to develop his AC system. But, in the first of a series of business errors that were to plague his life, he found out that his 50% share did not entitle him to a 50% voting share and he was voted out of his own company. One of the finest engineers in the world was reduced to digging ditches for a dollar a day¹².

Fortunately, AK Brown of the Western Union Telegraph Company saved Tesla from destitution. Brown furnished Tesla with a lab and instructions to produce a working AC dynamo. Tesla demonstrated his invention at a famous lecture to the American Institute of Electrical Engineers in May 1888. In New York an engineer called George Westinghouse heard about Tesla's lecture and wrote to the AIEE asking for a copy. Westinghouse Electric Company was one of the few electric companies to avoid being swallowed up by Edison, so when Tesla received a telegram from Westinghouse, he invited him to his laboratory in Pittsburgh. A deal was struck whereby Tesla sold all his rights to his 40 patents. Over the years Tesla made about $100,000 from this sale. This may seem like an excellent deal but, in another catastrophic business error Tesla allowed Westinghouse to back out of a $2.50/watt clause in the contract that would have set him up for the rest of his life¹³.

Tesla began working on the problem of large-scale production of AC power for commercial use. One problem he came across was that the Westinghouse engineers had decided that 133 Hertz was the optimum frequency with regards to transformation. However, Tesla's system was based around 60 Hertz. The practical difficulties of this problem plagued him until he invented a device, which still bears his name. The Tesla transformer, more commonly known as the Tesla coil, is now an integral part of every TV and radio¹⁴. Once Tesla had solved this problem, he had paved the way for the generation of electricity at Niagara Falls in 1895. AC power provided electricity to Buffalo, 22 miles away. This sterling success did not stop Edison's attempts to push DC power. In an attempt to stress the dangers of AC power, Edison sponsored a minor electrical engineer called Harold Brown to travel the country electrocuting animals with both DC and AC. The frequency of AC confuses the heart, so AC electrocuted animals died but DC victims were stunned but lived. Edison used these sideshow 'experiments' to contrast the danger of AC compared with the relative safety of DC. He continued his campaign by a typically devious piece of subterfuge.

The state of New York had recently decided upon electrocution as a 'humanitarian' alternative to hanging. The Medico-Legal Society of New York consulted Brown about the best method of execution, and he succeeded in convincing them to recommend AC to the New York State Penitentiary. A Westinghouse AC generator (secretly acquired by Edison) was used to electrocute a murderer called William Kemmler. The execution was bungled in a gruesome and undignified manner and Kemmler was literally cooked by the current. Tesla and Westinghouse (who had secretly funded an appeal to stop the execution on the grounds of cruel and unusual punishment) were horrified¹⁵. However, these attempts to discredit AC failed and the new system had begun to assert its supremacy. Even before the triumph of Niagara, AC had been chosen to light the Chicago Exposition of 1893, which featured hundreds of thousands of light bulbs. In five years Tesla had gone from being a ditch digger to one of the greatest engineers in the world. He lived in the finest hotels and hobnobbed with celebrities, counting the great writer Mark Twain as one of his closest friends. Nikola Tesla would never see such heights again.

Tesla and the Invention of Radio.

The invention of radio is a complex subject. The system that we know today was developed piecemeal by a number of different researchers and inventors. Tesla's adherents have always claimed a place in this company for him, claiming he was the true inventor of radio, but in this context it is probably more accurate to speak of the invention of radio rather than the inventor of radio.

The story of radio begins in 1867, with the Scottish physicist James Clerk Maxwell's discovery of the electro-magnetic field equations. These equations were used to demonstrate that light is an electro-magnetic wave and it followed logically from this that there would be electro-magnetic waves of frequencies higher and lower than that of light¹⁶. Although there were faltering attempts at using electro-magnetic waves as a means of communication, Heinrich Hertz took the first true steps in 1888.

Hertz, a student of Maxwell's theories, invented the first spark gap transmitter and receiver, thus becoming the first person to successfully utilise radio waves. Hertz's apparatus consisted of a Leyden jar (a primitive type of capacitor) and a coil of wire, the ends of which were left open so that a small gap was formed. The receiver was a similar coil at the other end of the room. When the jar was charged with electricity, sparks flew across the gap and similar sparks were registered at the coil at the other end of the room. Hertz then measured the velocity of the waves and found that they travelled at 300,000 km/hour, the same as light¹⁷. Maxwell's theories had been vindicated. It is important to note that at this point radio waves (or Hertzian waves, as they came to be known) were yet to be seen as a method of communication. Hertz himself believed that the waves had no practical use.

Tesla's interest in the field started in 1890. With Westinghouse's money for the AC system in his pocket, Tesla began developing his interest in high frequency currents. This led him to experiment with their application to Hertzian waves. The major modification he made to Hertz's system was the invention of the Tesla coil, which removed the magnetic ring of the transformer and replaced it with an air core, and used an unusually large gauge spiral inductor in the primary of the final step up transformer. In other words, the first coil of the circuit (known as the primary) is tuned so that the current vibrates at the same frequency as the natural frequency of the second coil. (This is the frequency that produces the largest vibrations.) Also, the coil does not have an iron core, which would tend to dampen the vibrations. This allowed the generation of high frequency currents with corresponding large electro-magnetic fields and is the basis of the tuning circuit He also developed a series of high frequency alternators, which produced frequencies of up to 33,000 Hz.

Although these were the forerunners of modern radio alternators, and the Tesla coil is an integral part of every TV and radio, it is important to avoid falling into the trap of identifying Tesla as the founding genius of radio. As we shall see, there is more to radio than these two inventions and, crucially, Tesla's ideas for their use in communication applications were very different to what we use today. Tesla's discovery of the tuning circuit allowed him to adjust 100 different circuits until only one responded to radio waves. He also hit upon the idea of using radio waves to transmit power to light bulbs. It is important to note that at this point Tesla had not considered radio waves as a form of communication, at least not as we know it.

In 1893 Tesla patented his radio apparatus. Two years later, on the eve of an experiment to demonstrate radio on a boat on the Hudson River, his researches were interrupted by a fire at his New York laboratory¹⁸. It would take him two years to build a new laboratory, during which other researchers would steal a march on him. In 1895 an enterprising young researcher called Guglielmo Marconi demonstrated a device in London which could transmit radio waves over a mile and a quarter. This system was almost exactly the same as Tesla's. Marconi insisted that he had not read any of Tesla's papers, even though they had been translated into many languages¹⁹. Undeterred by this open plagiarism, Tesla continued work. He had a new laboratory at Colorado Springs, funded by a grant from the banker Edward Adams and, by 1897, he had patented a radio communication device (US Patent Number 645576). Tesla's problem throughout this period was that he refused to involve investors in his system until he was absolutely sure that it would work. Meanwhile, Marconi was enthusiastically forging alliances with the business community, attracting investors to his Marconi Wireless Telegraph Company²⁰.

By this time Tesla had changed tack, and invested his time and money in developing a radio-controlled boat, that was designed to carry six torpedoes and no crew. Tesla demonstrated his effort in a water tank at Madison Square Garden on New York. Although the demonstration was impressive, he scared off potential investors by claiming that he was controlling the boat with his mind²¹.

By 1899 Marconi had succeeded in transmitting signals over 74 miles. He then adapted Sir Oliver Lodge's recent tuning circuit patent (based upon variable inductors) perfecting it and obtaining a patent in 1900²². Important work in this area was also undertaken by John Stone Stone. This is a clear example of Marconi's opportunism. Although not a great individual thinker like Tesla or Hertz, his talent lay in recognizing the worth of the work of others and adapting it for his own ends.

The World System

During this time, Tesla was focusing on using radio waves for power transmission. At Colorado Springs he built a huge magnifying power transmitter, based around a massive Tesla coil and an antenna that was 200 feet tall. It was capable of generating voltages of 100,000,000 volts. Tesla used this apparatus to light banks of light bulbs over 20 miles away. However, the power of radio waves from an antenna falls off at the rate of 1/r². (Where r = distance.) Quite by accident, Tesla found a fascinating, unorthodox solution to this problem²³. As his antenna also functioned as a receiver, he had taken to tracking the progress of lightning storms across the sky. He noticed a fading pattern as the storms moved over the horizon and deduced the presence of a standing wave effect between the sky and the ground. From these observations he deduced the existence of what he claimed were global resonances of 6, 18 and 30 Hz. This effect reduced the fall off in power to only 1/r, and so effectively the space between sky and ground was acting as a 2-D waveguide. The area between the ionosphere and the ground that allows the transmission of standing waves is now known as the Schumann cavity, and the Schumann resonances (discovered in 1952) are multiples of 7.5 Hz²⁴. However, as Tesla did not know this, and the prediction of the ionosphere by Heaviside was still two years away, he became convinced that Maxwell's equations were wrong. This was the first clear example of his lack of theoretical rigour leading him astray.

He continued with his power transmission experiments, but did not realise that this idea was impractical. For a large scale system of this type, as the author of The Amazing Nikola Teslapoints out:

Each receiver antenna would tend to interfere with its neighbours unless the total power was large relative to that tapped by each receiver. Large field intensities, however, would likely cause the same sparks and shocks he saw in his experiments at Colorado.
(Anonymous, 2000).

Meanwhile, Marconi was working on a practical type of 2-D waveguide. In December 1900 Tesla signed a deal with JP Morgan, one of America's richest men and a colleague of Adams. In return for $150,000 he gave Morgan a 51% stake in any future wireless patents he might develop. The following year he used the money to construct a new laboratory in Wardenclyffe, Long Island. It was here that he began the construction of his most audacious project to date. His plan this time was to exploit natural resonance he had found in the Earth itself. Tesla claimed that by exploiting these resonances he could use the Earth as a giant conductor and transmit power and communication to any point on the globe by using a magnifying transmitter even larger than the one he had built at Colorado Springs. Tesla's mistake in proposing this system stemmed partly from his failure to understand the concept of resonance. He seemed to think that resonance was a property that allowed more energy to be taken out of a system than could be put in - for instance, he once proposed to 'split the Earth like an apple' with resonance. He also did not realise that the Earth does not have the high conductivity required to store electric charge while it was not being used. Finally, although there is resonance at the 925 Hz frequency Tesla used, the Earth does not have the high Q factor needed for consistent power transmission at this frequency ²⁵.

Even if this was a valid project, he did not have the business acumen of an inventor like Edison or Marconi that was necessary to understand the economics of the matter. JP Morgan had believed he was investing in a communications project. An industry that had just spent a great deal of money on adopting the AC system was not about to scrap it for yet another new system. While he was consuming valuable time with this system, in 1901 Marconi sent his first transatlantic signal. An inventor called H Otis Pond told Tesla 'Looks like Marconi's got the jump on you', Tesla replied, 'Marconi is a fine fellow, let him continue. He is using 17 of my patents'²⁶. What Tesla did not realise was that it would take years of litigation to prove this. The Supreme Court would finally rule in Tesla's favour in October 1943. The Court considered as false Marconi's claim that he had never read Tesla's patents and stated that there was nothing in Marconi's work that had not already been discovered by Tesla. Unfortunately, by this point Nikola Tesla had been dead for nine months.

There are other figures in this story, notably Reginald Fessenden, who developed the first high power alternators that could be use in voice broadcasting and Edward Branly, who invented the coherer, but lack of space prevents their discussion in any detail²⁷. Suffice to say that although Tesla is not the undisputed inventor of radio, he is one of its founding fathers.

The Break with Morgan

Tesla's contract with Morgan was not as attractive as he had hoped. In 1903, needing more money to complete the Wardenclyffe tower, Tesla asked Morgan for a further grant. Morgan felt that as he had already spent $150,000 for no apparent result, there was no point in throwing good money after bad, so Tesla's request was turned down flat. Tesla tried to find power for the Wardenclyffe tower by approaching the Canadian government. He gave them a promise to build a power transmission station at Niagara to power rural Canada if they gave him 10,000 horsepower a year for 20 years. This proposal fell through, largely because Morgan had publicised his refusal of funding, and this led to Tesla being seen as unreliable. In later life Tesla always spoke well of Morgan, describing him as decent and generous. His private correspondence with Morgan, preserved in the US Library of Congress, tells a very different story.

We start on a proposition financially frail. You engage in impossible operations, you make me wait ten months for machinery. On top of this you produce a panic. When, after putting all I could scrape together, I come to show you that I have done the best that could be done you fire me out like an office boy and roar so that you are heard six blocks away; not a cent. It is spread all over town, I am discredited, the laughing stock of my enemies.
Letter from Tesla to JP Morgan, 14 January 1904, US Library of Congress. Quoted in Lomas, 1999.

By this point, Tesla had sold all of his own assets to keep the Wardenclyffe project afloat. In order to raise money, he had to take out an advert in the press offering his services as an electrical engineer. There were no takers. Morgan had blackened Tesla's name to the extent that the electrical industry perceived him as a crank. Some have seen this campaign of vilification as proof of a capitalist conspiracy to suppress the wireless power system, lest everybody receive free energy²⁸. The truth is probably more prosaic; Morgan no longer had much faith in Tesla, but he was not going to have a major investment working for anybody else. Tesla's attempt to salvage the Wardenclyffe project staggered on for a few more years, until he finally ran out of money in 1911 and the mortgage on the land was foreclosed on. The rest of Tesla's life is a frustrating blend of wild statements, the occasional good idea and a sad decline into poverty.

Tesla's Turbine

One of the few later inventions that actually seemed possible was the bladeless turbine. Tesla knew that all turbine blades suffer from bending stresses. Inspired by the remembrance of a toothless water wheel he built as a child, he decided to attempt to build a turbine without blades. His design was based upon a stack of shaft mounted heat resistant disks placed within a cylindrical casing. Gas was introduced into the casing at a tangent to the disks. The viscosity of the gas efficiently transferred energy to the disks and so to the shaft²⁹. By 1910 he had built a 12-inch (30-cm) diameter turbine capable of delivering 100 horsepower of power. He attempted to sell his design to an engineering firm called Allis Chambers of Milwaukee. According to Lomas, (1999), Tesla made the fundamental mistake of ignoring the company engineers and going straight to the company chairman with his proposal. Their sensibilities insulted, the engineers deliberately gave the turbine a poor report, saying that the discs warped under pressure. Rather than stay and fight his corner, Tesla walked out, disgusted. No more work was done on Tesla turbines until the 1980s, when a company called the Tesla Engine Builder's Association began building them. There is now an emerging interest in Tesla's turbine and, in 1986, Texaco began using pumps invented by Tesla, based on a similar design to the turbine. They claim to save $68,000 dollars per pump per year using this design³⁰.

The Decline

Although he made a little money from an electro-therapeutic device³¹, the turbine was Tesla's last serious, large-scale commercial project. He was awarded the Edison Medal, the highest honour the American Institution of Electrical Engineers could bestow (the irony could not have escaped him) in 1917, but from there his life went into a slow decline. He went from living in luxury to staying in cheap rooming houses. There is evidence of a dramatic decline in his mental health. He expressed a belief in his autobiography that he was actually an alien avatar born to 'Earth parents'³². His living became dependent on writing articles for magazines, in which he made increasingly bizarre statements, one of the most famous being his claim to have invented a death ray, which he claimed could destroy ships 200 miles away. The descriptions of this device are vague and general, but Tesla seems to have been talking about some form of particle beam accelerator. References to its use apparently date back to 1908, when, during a test of the ray, Tesla is alleged to have accidentally caused the Tunguska incident in Siberia³³. He returned to this alleged invention time after time throughout his life, offering it to the US government on the country's entry into World War Two in 1942. Like most of Tesla's later work, the ray appears to be an attempt to prop up interest in his fading talent. Examined on its practicalities, the device would not have had the power that Tesla claimed. A high velocity rifle bullet has 3 or 4,000 Joules of energy. A beam from a particle accelerator has, at most, a few hundred³⁴.

However, Tesla earned his keep with such claims and every couple of years he would make grand claims for a new invention that would never materialise. This paid his rent (magazine editors obviously preferring wild statements to dry academia), but inevitably cemented his reputation as a crackpot. He had few friends and was frequently evicted by hotel managers because of his habit of keeping pigeons in his room. Nikola Tesla died of heart failure in his room at the Hotel New York, in New York City on 7 January, 1943.

Conclusion

Tesla's decline into obscurity was, at least partly, of his own doing. The lack of a strong theoretical background and, later in life, the need for publicity, led him into making wild and unprovable statements. Nevertheless, the major reason why few people, even in his field, have heard of Nikola Tesla today is the fact that he was consistently out manoeuvred by his business rivals, principally Edison and Marconi. It is sadly inevitable that for those inventors who attempt to forge a career outside the security of an academic environment, the ability to co-operate with big business is more important than scientific insight.

Today, in the Hall of Electricity³⁵ in the Smithsonian Institute in Washington DC, stands a model of Tesla's first AC dynamo. Next to it stands a bust of Thomas Alva Edison. All attempts to replace this with a bust of Tesla have been rebuffed and nowhere in the exhibition is he even mentioned³⁶. Most radio textbooks credit Marconi with the major role in its invention, some not deigning to even mention Tesla. Tesla was once questioned on the willingness of others to claim his discoveries, and he replied:

Let the future tell the truth, and evaluate each one according to his work and accomplishments. The present is theirs; the future, for which I have really worked, is mine.
Quoted in Lange, 1998

Fifty-seven years after his death, Tesla is still being denied the future he worked for.

Acknowledgements

The author would like to extend his thanks to the researcher and academic Jurgen Heinzerling, who proof-read the first draft and offered some very useful advice.