The Philadelphia Experiment

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 some time around October 28, 1943. The U.S. Navy destroyer escort USS Eldridge (DE-173) was claimed to have been rendered invisible (or "cloaked") to enemy devices.

The story 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 the 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 that comprise electromagnetic radiation and gravity, in other words, uniting the fields of electromagnetism and gravity 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 of military value and, by the same accounts, 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.

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