The often rumored Philadelphia Experiment where they made a ship disappear is becoming reality.
Per Wiki:
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, sometime 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 first appeared in 1955, in letters of unknown origin sent to a writer and astronomer, Morris K. Jessup. It is widely understood to be a hoax;[1][2][3] the U.S. Navy maintains that no such experiment was ever conducted, that the alleged details of the story contradict well-established facts about USS Eldridge, and that the claims do not conform to known physical laws.[4]
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 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.
Diffused lighting camouflage was a form of active camouflage using counter-illumination to enable a ship to match its background, the night sky, prototyped by the Royal Canadian Navy on corvettes during World War II. The principle was discovered by a Canadian professor, Edmund Godfrey Burr, in 1940. It attracted interest because it could help to hide ships from submarines in the ongoing Battle of the Atlantic, and the research project began early in 1941. The Royal Navy and the US Navy carried out further equipment development and trials between 1941 and 1943.
The concept behind diffused lighting camouflage was to project light on to the sides of a ship so as to make its brightness match its background. For this purpose, projectors were mounted on temporary supports attached to the hull. The prototype was developed to include automatic control of brightness using a photocell. The prototyped concept was never put into production, though the Canadian prototypes did briefly see active service. The Canadian ideas were, however, adapted by the US Air Force in its Yehudi lights project.