Tesla lived for nearly four more decades after Wardenclyffe. They were years of continued invention, financial struggle, growing eccentricity and occasional fame. He remained a public figure, but increasingly as a source of startling predictions rather than working technology.

Inventions and patents

Tesla kept working. He patented a bladeless turbine in 1913, which used smooth, closely spaced discs instead of blades, and he worked on measuring instruments, lighting devices and ideas for vertical takeoff aircraft. Over his lifetime he received around three hundred patents in many countries. But none of his later inventions achieved commercial success on the scale of his AC system. Investors were wary after Wardenclyffe, and Tesla was poor at managing money and business partnerships.

Honors and rumors

In 1915, newspapers reported that Tesla and Edison would share the Nobel Prize in Physics. The report was false; the prize went to William Henry Bragg and his son. Neither Tesla nor Edison ever won a Nobel Prize. In 1917, Tesla received the Edison Medal, the highest honor of the American Institute of Electrical Engineers, named, ironically, after his old rival. He accepted it after some persuasion. In 1919 he published his autobiographical series My Inventions in the magazine Electrical Experimenter.

Life in hotels

Tesla never married. He said he believed marriage would distract an inventor from his work. He lived for decades in a series of New York hotels, often leaving unpaid bills behind when he moved, as at the Waldorf Astoria, the St. Regis and the Hotel Pennsylvania. His last home, from 1933, was room 3327 of the Hotel New Yorker. For some years, Westinghouse quietly paid him a modest monthly consulting fee and covered his hotel rent.

Habits and eccentricities

Tesla's personal habits became famous. He was intensely concerned with cleanliness and germs, using many napkins at meals to polish his silverware. He reported counting steps and calculating the volume of food on his plate, and he disliked jewelry, especially pearls. He walked for miles daily. In later life he devoted much of his time and money to feeding pigeons in New York's parks and caring for injured birds in his hotel room. He described a deep attachment to one white pigeon, saying he loved her as a man loves a woman, and that when she died he knew his work was finished.

Some writers have speculated about diagnoses to explain such behavior. It is wiser not to diagnose a person who died long ago from secondhand accounts. What can be said is that Tesla was a deeply unusual and often lonely man.

Ties to his homeland

Tesla never lost his connection to the lands of his birth. In 1892, after his European lectures, he visited Belgrade, where he was received as a national hero and met the young Serbian king. He kept up a correspondence with relatives and Serbian friends, and in his final years the government of Yugoslavia granted him a modest pension. During the Second World War, when Yugoslavia was invaded and torn by ethnic violence, the elderly Tesla issued appeals for unity among the South Slav peoples, Serbs and Croats alike.

Birthday predictions and the death ray

From the early 1930s, Tesla held press conferences on his birthday, where reporters came to hear his latest claims. He predicted pocket-sized devices for wireless communication worldwide, a forecast that sounds like the modern smartphone. He also announced inventions that he never demonstrated. In 1934 he claimed to have invented a particle-beam weapon, which newspapers called a “death ray” and he called “teleforce,” able to destroy aircraft hundreds of miles away. He presented it as a defensive weapon that would make nations invulnerable and so end war. He sought funding from governments, but no working device was ever shown.

Views on society

Tesla held ideals of progress and peace, believing technology could end poverty and war. He also held views that are troubling today. In a magazine interview published in 1935, he endorsed eugenics, the idea, then widespread among educated people in America and Europe, that society should prevent those considered unfit from having children. Eugenics led to forced sterilizations in the United States and, in Nazi Germany, to mass murder. Remembering this is part of an honest account: admiration for an inventor's genius need not mean accepting all his opinions.

Worked example: telling prediction from promise

Tesla's later claims mix remarkable foresight with promises that never came true. Sort them.

• Pocket wireless devices. He described communicating with anyone in the world through a small device. Fulfilled, decades later, by mobile phones, though built on technologies developed by many others.
• Remote-controlled machines. His 1898 boat foreshadowed drones and robots. Fulfilled.
• Worldwide wireless power. Not achieved, and most engineers think it impractical.
• The death ray. Never demonstrated. No evidence it worked.
• Machines ending war. Remote-controlled weapons now exist, but they have not ended war.

The pattern suggests a way to judge any visionary. Ask whether a claim was demonstrated, published in enough detail for others to check, or only announced. Tesla's lasting achievements are the ones he built and patented and others could reproduce. His announcements show a powerful imagination, but imagination alone is not invention.