The Philadelphia Experiment was an alleged attempt by the United States government to hide a warship (the USS Eldridge) from visual and radar detection.
The Story of the Experiment
Like many accounts of alleged cover-ups, there is no one consistent version of the Philadelphia experiment story. However, the story invariably centers on the USS Eldridge, a Cannon-class destroyer escort in service of the United States Navy. It was launched in July of 1943.
Supposedly, in the summer of 1943, the USS Eldridge was outfitted with equipment designed to "cloak" the warship from visual and radar detection at the Philadelphia Naval Yards. According to someone who claimed to witness the installation, the equipment consisted of four immense generators, Tesla coils, and endless amounts of thick wire. According to the legend, this equipment was designed to employ a Unified Field Theory in an attempt to make inanimate objects invisible.
Testing began that summer, and supposedly several tests were initially successful. Some witnesses reported that the Eldridge became invisible and was replaced by a greenish fog. Several crew members experienced nausea, so the Navy altered their experiment to only pursue radar invisibility.
On October 28th 1943, during one of the tests, the Eldridge allegedly disappeared in a flash of blue light. Allegedly, the Eldridge reappeared at the US naval base in Norfolk, Virginia. Several people saw the Eldridge offshore before it disappeared again, returning to its original point in Philadelphia.
The accidental teleportation had even worse side effects for the crew: some exhibited signs of mental illness (including schizophrenia), some disappeared and never were recovered, and some were found fused into the bulkheads of the ship. At this point, the Navy cancelled the experiment.
The official response
The Navy denies that such an experiment ever occurred. There are some inconsistencies within the conspiracy theory; at the time when the Eldridge was supposedly at the Philadelphia Naval Yards, it was on a shakedown cruise in the Bahamas. Theorists claim, however, that the Navy falsified the records to hide the experiment's existence.