The Philadelphia Experiment is an alleged military experiment supposed to have been carried out by the U.S. Navy at the Philadelphia Naval Shipyard in Philadelphia, Pennsylvania, United States, sometime around October 28, 1943. The U.S. Navy destroyer escort USS Eldridge was claimed to have been rendered invisible (or “cloaked”) to enemy devices.
The story first appeared in 1955, in letters of unknown origin sent to UFO writer Morris K. Jessup. It is widely understood to be a hoax; the U.S. Navy maintains that no such experiment was ever conducted, that the details of the story contradict well-established facts about USS Eldridge, and that the alleged claims do not conform to known physical laws.
The experiment was allegedly based on an aspect of some unified field theory, a term coined by Albert Einstein to describe a class of potential theories; such theories would aim to describe — mathematically and physically — the interrelated nature of the forces of electromagnetism and gravity, in other words, uniting their respective fields into a single field.
According to some accounts, unspecified “researchers” thought that some version of this field would enable using large electrical generators to bend light around an object via refraction, so that the object became completely invisible. The Navy regarded this as of military value and it sponsored the experiment.
Another unattributed version of the story proposes that researchers were preparing magnetic and gravitational measurements of the seafloor to detect anomalies, supposedly based on Einstein’s attempts to understand gravity. In this version, there were also related secret experiments in Nazi Germany to find anti-gravity, allegedly led by SS-Obergruppenführer Hans Kammler.
There are no reliable, attributable accounts, but in most accounts of the supposed experiment, USS Eldridge was fitted with the required equipment at the Philadelphia Naval Shipyard. Testing began in the summer of 1943, and it was supposedly successful to a limited extent. One test resulted in Eldridge being rendered nearly invisible, with some witnesses reporting a “greenish fog” appearing in its place. Crew members complained of severe nausea afterwards. Also, reportedly, when the ship reappeared, some sailors were embedded in the metal structures of the ship, including one sailor who ended up on a deck level below than where he began and had his hand embedded in the steel hull of the ship, as well as some sailors who went “completely bananas.” There is also a claim the experiment was altered after that point at the request of the Navy, limiting it to creating a stealth technology that would render USS Eldridge invisible to radar. None of these allegations have been independently substantiated.
The conjecture then claims that the equipment was not properly re-calibrated, but that in spite of this, the experiment was repeated on October 28, 1943. This time, Eldridge not only became invisible, but it disappeared from the area in a flash of blue light and teleported to Norfolk, Virginia, over 200 miles (320 km) away. It is claimed that Eldridge sat for some time in view of men aboard the ship SS Andrew Furuseth, whereupon Eldridge vanished and then reappeared in Philadelphia at the site it had originally occupied. It was also said that the warship went approximately ten minutes back in time.
Many versions of the tale include descriptions of serious side effects for the crew. Some crew members were said to have been physically fused to bulkheads while others suffered from mental disorders, some re-materialized inside out, and still others vanished. It is also claimed that the ship’s crew may have been subjected to brainwashing, to maintain the secrecy of the experiment.