The Philadelphia Experiment was a claimed event reported by Carl M. Allen, a former merchant mariner, at the United States Navy's Philadelphia Naval Shipyard in Philadelphia, Pennsylvania, around October 28, 1943. Allen described an experiment in which the U.S. Navy supposedly tried to make a destroyer escort, the USS Eldridge, invisible and the strange results that followed.

The story became known in late 1955 when Allen sent a book containing handwritten notes about the experiment to a U.S. Navy research group. Later, he wrote letters to a UFO author with additional claims. Allen’s account of the event is widely considered to be a hoax.

Over the years, many different and sometimes conflicting versions of the experiment have appeared in paranormal books and popular movies. The U.S. Navy states that no such experiment ever took place, that the story’s details conflict with known facts about the USS Eldridge, and that the scientific principles the experiment is said to be based on do not exist.

Origins of the story

In late 1955, Carl M. Allen sent an anonymous package labeled "Happy Easter" to the U.S. Office of Naval Research. Inside was a copy of Morris K. Jessup's book, The Case for the UFO: Unidentified Flying Objects, filled with handwritten notes in three different shades of blue ink. These notes seemed to show a debate among three people, only one of whom was named "Jemi." They discussed Jessup's ideas about flying saucer propulsion, alien life, and expressed worry that Jessup was close to uncovering their technology.

The writers referred to themselves as "Gypsies" and talked about two types of "people" in outer space. Their notes used unusual capitalization and punctuation, and they debated details from Jessup's book. One note mentioned the "Philadelphia Experiment," suggesting someone had highlighted a theory Jessup wrote about.

In January 1956, Allen began writing letters to Jessup, using his name and also "Carlos Miguel Allende." One letter warned Jessup not to study how unidentified flying objects might float. Allen claimed a scientist named Franklin Reno tested theories by Albert Einstein at the Philadelphia Naval Shipyard in October 1943. Allen said he saw this experiment while working on the ship SS Andrew Furuseth. He described a ship becoming invisible, briefly appearing in Norfolk, Virginia, and then returning to Philadelphia. He claimed the crew suffered side effects like confusion, intangibility, and being "frozen." When Jessup asked for proof, Allen referred to a newspaper article he said existed but could not be found.

In 1957, Jessup was shown the annotated book by the Office of Naval Research. He noticed the handwriting matched letters Allen had sent. Twelve years later, Allen admitted he wrote the annotations to scare Jessup.

Two officers at the Office of Naval Research, Captain Sidney Sherby and Commander George W. Hoover, studied the annotations. Hoover said he found no evidence of the invisibility experiment. He discussed the notes with Austin N. Stanton, president of Varo Manufacturing Corporation, who later had Varo produce copies of Jessup's book with the annotations and Allen's letters. These became known as the "Varo edition." The annotations included notes from "Jemi" (in blue-violet ink), "Mr. A" (Allen, in blue ink), and "Mr. B" (in blue-green ink).

Jessup tried to write more books about UFOs but failed. He lost his publisher and faced personal struggles, eventually dying by suicide in 1959. Reporters who tried to contact Allen found him hard to reach. One reporter from his hometown found Allen's family had many documents with his notes. They described him as a "fantastic mind" but also a "drifter" and "master leg-puller."

In 1965, Vincent Gaddis wrote a book titled Invisible Horizons: True Mysteries of the Sea, which included the story from the Varo annotations. In 1978, George E. Simpson and Neal R. Burger wrote a novel, Thin Air, about a naval officer investigating wartime invisibility experiments.

The story gained wide attention in 1979 when Charles Berlitz and William L. Moore published The Philadelphia Experiment: Project Invisibility, claiming it was a true account. The book expanded on claims of strange events, lost Einstein theories, and government coverups, based on Allen's letters to Jessup.

The book also discussed Townsend Brown, a Navy technician who experimented with force fields. Paul LaViolette's 2008 book, Secrets of Antigravity Propulsion, mentioned Brown's work.

The story was made into a 1984 film, The Philadelphia Experiment, directed by Stewart Raffill. The film was loosely based on earlier accounts. In 1989, Alfred Bielek claimed he was on the USS Eldridge during the experiment and said the film matched his experiences.

Some accounts suggest the experiment was based on a "unified field theory," a concept Albert Einstein used to describe how forces like electromagnetism and gravity might be connected. Researchers thought this could allow using electrical generators to bend light around an object, making it invisible. The Navy saw this as valuable and funded the experiment.

Another version claims the experiment involved measuring the seafloor for magnetic and gravitational anomalies, possibly linked to Einstein's gravity research. It also mentions secret Nazi experiments on anti-gravity, led by SS officer Hans Kammler.

Most accounts say the USS Eldridge was equipped with experimental devices at the Philadelphia Naval Shipyard in 1943. Testing began that summer and reportedly had limited success. One test made the ship nearly invisible, with witnesses seeing a "greenish fog" instead. Crew members later reported severe nausea.

When the ship reappeared, some sailors were stuck inside the metal structure, including one who was embedded in the hull. Others reportedly became extremely disoriented. Some accounts say the experiment was altered after this event.

Evidence and research

Historian Mike Dash says that many authors who shared the "Philadelphia Experiment" story after Jessup's version did not do much research themselves. For example, in the late 1970s, Allende/Allen was often described as hard to find, but Goerman found his identity with just a few phone calls.

Some people suggest that many stories about the event focus more on exciting details than real research. Berlitz and Moore wrote a book called The Philadelphia Experiment: Project Invisibility, claiming it included facts like interviews with scientists. However, their work was criticized for copying parts of a novel called Thin Air, which came out a year earlier.

Personnel at the Fourth Naval District say the event might have been a misunderstanding of normal research during World War II at the Philadelphia Naval Shipyard. One idea is that stories about invisibility came from experiments called degaussing, which make ships harder to detect by magnetic mines. Another possible source of stories about levitation or teleportation might be experiments on the USS Timmerman (DD-828), where a generator created electrical sparks, though no crew members reported effects.

Observers say it is not right to believe a strange story from one person without proof. Robert Goerman wrote in Fate magazine in 1980 that "Carlos Allende"/"Carl Allen," who supposedly wrote to Jessup, was Carl Meredith Allen of Pennsylvania. Allen had a history of mental health issues and may have made up parts of the experiment story. Later, Goerman learned Allen was a family friend who liked to share unusual ideas.

The USS Eldridge was not commissioned until August 27, 1943, and stayed in New York City until September 1943. The October experiment supposedly happened during its first trip to the Bahamas, but conspiracy theorists claim the ship's logs might be fake or still secret. They also say the USS Hammann (DE-131) might have been used instead of the USS Eldridge, even though Carl M. Allen's original story started the hoax.

The Office of Naval Research (ONR) said in 1996 that it never studied radar invisibility, either in 1943 or later. It pointed out that the ONR did not exist until 1946 and called the "Philadelphia Experiment" story "science fiction."

Navy veterans who served on the USS Eldridge told a newspaper in 1999 that their ship never went to Philadelphia. More proof comes from the ship's complete World War II action report and its 1943 deck log, which are available on microfilm.

Researcher Jacques Vallée described a process on the USS Engstrom, which was next to the USS Eldridge in 1943. The operation used a strong electromagnetic field to make the ship less detectable by mines. This method was invented by Charles F. Goodeve, a Canadian, and used widely during World War II.

British ships from that time often had degaussing systems built into their decks, and these systems are still visible on ships like HMS Belfast in London. Degaussing is still used today but does not affect visible light or radar. Vallée thinks stories about the USS Engstrom's degaussing might have been mixed up over time and could have influenced the "Philadelphia Experiment" story.

Vallée mentions a veteran who served on the USS Engstrom and says he might have traveled from Philadelphia to Norfolk and back in one day. At that time, only naval ships could use the Chesapeake & Delaware Canal and Chesapeake Bay, which were kept secret to avoid attacks by German submarines.

The same veteran claims to be the person Allende saw "disappear" at a bar. He says a fight broke out, and bar staff helped him leave before the police arrived because he was underage. They lied and said he had vanished.