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Nikola Tesla adjusted his silk cravat and stepped onto the wooden dais inside the vast machinery hall of the Columbian Exposition . Below him , twelve massive Westinghouse alternators hummed like a subterranean hive , their copper armatures casting long , spinning shadows across the concrete floor . Across the partition stood Mr . Sterling , the chief consulting engineer representing Edison's direct current syndicate , holding a stopwatch in one hand and a leather ledger in the other . " The opening procession begins tomorrow evening , Mr . Tesla , yet your polyphase dynamos have not completed a continuous two - hour load test , " Sterling shouted above the dynamos . " If you cannot do so before midnight , the exposition committee will disconnect your transmission lines . Edison advised us to cancel the contract , and so did several members of our board . " " Edison believed direct current was the only practical medium , but he was mistaken , " Tesla replied calmly . He reached for a heavy brass lever , paused , and waited for the frequency gauges to align before doing so . " Direct current requires a generating station every mile ; alternating current does not . His system produces low - voltage heat , ours brilliant light . " Sterling walked toward the central distribution switchboard , inspecting the ceramic insulators with deep suspicion . " High - voltage transmission is inherently chaotic . Look at the vibration in the third circuit . One transformer runs cool , but the other ones radiate excessive heat . Something in the magnetic winding has drifted , though your mechanics cannot explain why . " " They cannot explain the variation because they are looking at mechanical friction , whereas the cause is electrical induction , " Tesla said . He signaled his chief technician to adjust the primary field coils , and the young man did so without hesitation . The shrill hum smoothed into a deep , velvety resonance . " Edison feared mysterious phenomena , but Westinghouse never did , nor should any true man of science . When an anomaly appears , one must investigate its root ; to refuse to do so is mere prejudice . " Tesla retrieved a solid copper egg from a velvet - lined case and set it down upon a flat circular table wound with copper coils . He closed an auxiliary knife switch . As the rotating magnetic field sprang to life , the metal egg trembled , began to spin on its side , and then slowly rose onto its pointed tip , revolving at incredible speed without any physical axle touching it . Sterling leaned forward , his stopwatch forgotten . He blinked at the spinning metal , unable to reconcile the spectacle with his conventional formulas . " How does the rotating field generate such torque ? " " Through phase displacement , " Tesla answered . " One current peaks as the other falls ; one coil pushes while the other pulls . Such is the simplicity of nature when mathematically mastered . Edison claimed that polyphase power was dangerous , but he could not prove it , nor could his engineers . Nature obeys harmonic laws , and so must we . " The copper egg continued to spin upon its slender apex , perfectly poised beneath the incandescent bulbs . Sterling closed his ledger , slipped the stopwatch into his waistcoat pocket , and stepped back from the platform without another objection .
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