On January 7, 1943, Nikola Tesla, 86, died alone in Room 3327 of the New Yorker Hotel. On January 9th, after learning of Tesla’s death, the FBI ordered the Alien Property Custodian to seize all of Tesla’s belongings, even though Tesla was an American citizen. Tesla’s entire estate from the Hotel New Yorker and other New York City hotels was transported to the Manhattan Storage and Warehouse Company under OAP seal.
The Philadelphia Experiment was a naval military experiment alleged to have been carried out at the Philadelphia Naval Shipyard in Philadelphia, Pennsylvania, USA sometime around October 28, 1943. The U.S. Navy destroyer escort USS Eldridge was claimed to be rendered invisible (or “cloaked”) to enemy devices.
Did secret papers seized from Nikola Tesla upon his death in January 1943 play a role in the October 1943 Philadelphia Experiment? And what role might The Ether have played in the rumored experiment?
“The generally accepted contention that the famous Michelson-Morley experiment dealt the coup de grâce to the ether conception had been challenged as early as December 1911″ by William Magpie in an address to the American Physics Society. “Without an aether how do we account for the interference phenomena which made that [Michelson-Morley] experiment possible?” asked Magpie. 
Results from the Michelson-Morley experiment were wrongly interpreted and Albert Einstein puffed his pipe and proclaimed, “The Ether is not necessary.” (Background: Our Friend, The Ether (Part 6). Ersjdamoo’s Blog entry of October 19, 2013.)
Einstein himself admitted, in 1951, “This word ether has changed its meaning many times in the development of science.” For Plato and Aristotle, The Ether was a “supermundane” fifth element, the quinta essentia. For the stoic philosophers, The Ether was the pneuma, an ancient Greek word for breath and connected with the soul. Isaac Newton thought of The Ether as an important part of the mechanical philosophy. Sir Oliver Lodge went so far as to think The Ether to be the medium involved in telepathy and ESP. Furthermore, Albert Einstein was not consistent throughout his life as to his opinion of The Ether: At first, Einstein accepted it. Later, the Nobel Prize-winning physicist abandoned The Ether during the years 1905-1916. But then, between 1916 and 1924, Einstein introduced a concept of the “new ether.” 
Abandoned in “absolute space,” The Ether retorts, “I am in no hurry. I’m not going anywhere. The ‘scientists’ are the ones who are in ‘relative motion.’ As for me, I can sit and wait.” (Background: Ether Abandoned! Ersjdamoo’s Blog entry of September 30, 2013.)
Nikola Tesla’s view of The Ether aligned itself with that of the Theosophists:
“Long ago [I] recognised that all perceptible matter comes from a primary substance, of a tenuity beyond conception and filling all space – the Akasa or luminiferous ether – which is acted upon by the life-giving Prana or creative force, calling into existence, in never ending cycles, all things and phenomena.”
“The primary substance, thrown into infinitesimal whirls of prodigious velocity, becomes gross matter; the force subsiding, the motion ceases and matter disappears, reverting to the primary substance.” 
Nikola Tesla obviously had not abandoned The Ether.
The Ether is associated with electro-magnetism. The two pillars of this electromagnetic ether are Benjamin Franklin (electricity) and Anton Mesmer (magnetism).  The Ether is also associated with the force of gravity. These etheric forces, electro-magnetism and gravity, are said to have been key to the Philadelphia Experiment.
Testing allegedly began in the summer of 1943. This would have been about six months after Nikola Tesla’s papers had been seized by the U.S. government, then at war with Nazi Germany. One test is said to have resulted in the USS Eldridge being rendered almost completely invisible, with some witnesses reporting a “greenish fog” appearing in its place. When the ship reappeared, some sailors were embedded in the metal structures of the ship! 
The experiment was repeated on October 28, 1943. This time, the USS Eldridge not only became invisible, but she physically vanished from the area in a flash of blue light and teleported to Norfolk, Virginia, over 200 miles away! It is claimed that the Eldridge sat for some time in full view of men aboard the ship SS Andrew Furuseth, whereupon the Eldridge vanished from their sight, and then reappeared in Philadelphia at the site it had originally occupied. It was also said that the warship went approximately 10 seconds back in time. 
——- Sources ——-
 Einstein and the Ether, by Ludwik Kostro. Montreal: Apeiron, 2000
 “Tesla vs. Einstein: The Ether & the Birth of the New Physics”,
May 11, 2012. By Marc J. Seifer. http://www.newdawnmagazine.com/articles/tesla-vs-einstein-the-ether-the-birth-of-the-new-physics
 Ether: The Nothing That Connects Everything, by Joe Milutis. University of Minnesota Press, 2006. (Also available as a Kindle e-book.)
 “Philadelphia Experiment”, Wikipedia, October 24, 2013.