The mechanism behind Tesla's death ray is not well understood. It was apparently some sort of particle accelerator. Tesla said it was an outgrowth of his magnifying transformer, which focused its energy output into a thin beam so concentrated it would not scatter, even over huge distances. He promoted the device as a purely defensive weapon, intended to knock down incoming attacks - making the death ray the great-great grandfather of the Strategic Defense Initiative.
It is not certain if Tesla ever used the death ray, or indeed if he even succeeded in building one. But the following is the often-related story of what happened one night in 1908 when Tesla tested the foreboding weapon.
At the time, Robert Peary was making his second attempt to reach the North Pole. Cryptically, Tesla had notified the expedition that he would be trying to contact them somehow. They were to report to him the details of anything unusual they might witness on the open tundra. On the evening of June 30, accompanied by his associate George Scherff atop Wardenclyffe tower, Tesla aimed his death ray across the Atlantic towards the arctic, to a spot which he calculated was west of the Peary expedition.
Tesla switched on the device. At first, it was hard to tell if it was even working. Its extremity emitted a dim light that was barely visible. Then an owl flew from its perch on the tower's pinnacle, soaring into the path of the beam. The bird disintegrated instantly.
That concluded the test. Tesla watched the newspapers and sent telegrams to Peary in hopes of confirming the death ray's effectiveness. Nothing turned up. Tesla was ready to admit failure when news came of a strange event in Siberia.
On June 30, a massive explosion had devastated Tunguska, a remote area in the Siberian wilderness. Five hundred thousand square acres of land had been instantly destroyed. Equivalent to ten to fifteen megatons of TNT, the Tunguska incident is the most powerful explosion to have occurred in human history -- not even subsequent thermonuclear detonations have surpassed it. The explosion was audible from 620 miles away. Scientists believe it was caused by either a meteorite or a fragment of a comet, although no obvious impact site or mineral remnants of such an object were ever found.
Nikola Tesla had a different explanation. It was plain that his death ray had overshot its intended target and destroyed Tunguska. He was thankful beyond measure that the explosion had - miraculously - killed no one. Tesla dismantled the death ray at once, deeming it too dangerous to remain in existence.
