The Philadelphia Experiment was a claimed event said to have been seen by a former merchant mariner named Carl M. Allen 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 tried to make a destroyer escort, the USS Eldridge, disappear and the strange results that happened afterward.

The story became known in late 1955 when Allen sent a book filled with notes written by hand about the experiment to a U.S. Navy research group. Later, he wrote letters to a UFO author with more claims about the event. Allen's description of the event is widely believed to be a hoax.

Over the years, many different—and sometimes conflicting—versions of the story have appeared in paranormal books and movies. The U.S. Navy says no such experiment ever took place, that the details of the story do not match known facts about the USS Eldridge, and that the science the experiment is said to be based on does 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 book titled The Case for the UFO: Unidentified Flying Objects by Morris K. Jessup. The book had handwritten notes in its margins, written in three different shades of blue ink. These notes seemed to show a debate between three people, one of whom was named "Jemi." The notes discussed Jessup’s ideas about how flying saucers might move, talked about alien life, and warned that Jessup was getting too close to learning about their technology.

The people who wrote the notes called each other "Gypsies" and mentioned two types of "people" living in space. Their writing used unusual capitalization and punctuation. They also discussed details from Jessup’s book and made indirect references to the "Philadelphia Experiment." One person said they were reassuring others about a theory Jessup had written about.

In January 1956, Allen began writing letters to Jessup using his name and another name, "Carlos Miguel Allende." One letter warned Jessup not to study how unidentified flying objects might float. Allen claimed this idea came from theories by Albert Einstein, which a scientist named Franklin Reno supposedly tested 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, then briefly appearing in Norfolk, Virginia, before returning to Philadelphia. He claimed the crew suffered strange effects, like losing their minds, becoming untouchable, or being "frozen" in place. When Jessup asked for proof, Allen said he needed to remember more and mentioned a newspaper article that did not exist.

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

Two Navy officers, Captain Sidney Sherby and Commander George W. Hoover, studied the annotations. Hoover said he found no real evidence about the invisibility experiment. He discussed the notes with a man named Austin N. Stanton, who worked for a company called Varo Manufacturing. Stanton became interested and had copies of Jessup’s book with the annotations and Allen’s letters printed. These copies became known as the "Varo edition." The notes included handwriting from "Jemi" (written in blue-violet ink) and two other people: "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 problems. He died by suicide in Florida on April 30, 1959.

People who tried to contact Allen found him hard to reach. A reporter from his hometown found his family, who gave him documents covered in Allen’s notes. They described Allen as a "fantastic mind" but also a "drifter" and "master leg-puller."

In 1965, Vincent Gaddis wrote a book called 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 titled Thin Air, which imagined a Navy officer investigating wartime invisibility experiments.

The story became widely known in 1979 when Charles Berlitz and William L. Moore published The Philadelphia Experiment: Project Invisibility, claiming it was a true account. The book added details about strange events, lost scientific theories, and government secrets. It also mentioned Townsend Brown, a scientist who studied force fields. Paul LaViolette’s 2008 book Secrets of Antigravity Propulsion also discussed Brown’s work.

The story was made into a 1984 movie called The Philadelphia Experiment, directed by Stewart Raffill. The film was loosely based on earlier accounts. In 1989, a man named Alfred Bielek claimed he was on the ship USS Eldridge during the experiment. He later said the movie matched his claims.

Some accounts say the experiment was based on a theory called a "unified field theory," which Albert Einstein tried to develop. This theory aimed to explain how electricity and gravity are connected. Researchers believed such a theory could allow large generators to bend light around an object, making it invisible. The Navy thought this could be useful for military purposes.

Another version of the story says researchers were measuring the ocean floor for magnetic and gravitational clues, possibly linked to Einstein’s work on gravity. It also claims secret experiments in Nazi Germany were trying to find anti-gravity, led by a man named Hans Kammler.

Most accounts say the USS Eldridge was equipped with special tools at the Philadelphia Naval Shipyard in 1943. Testing began in the summer of that year, and some tests reportedly made the ship nearly invisible, with witnesses seeing a "greenish fog" instead. Crew members later said they felt very sick.

Some say the ship reappeared with sailors stuck inside the metal structure, including one who ended up on a lower deck with his hand embedded in the hull. Others claimed sailors became extremely confused. It is also said the experiment was changed after this event, but no reliable sources confirm these details.

Evidence and research

The historian Mike Dash points out that many authors who shared the "Philadelphia Experiment" story after Jessup's version did not do much research themselves. For example, during the late 1970s, Allende/Allen was often described as hard to find, but Goerman discovered Allende/Allen's identity after making just a few phone calls.

Some people suggest that many stories about the event focus more on exciting but untrue details than on real facts. Berlitz and Moore's book, The Philadelphia Experiment: Project Invisibility, claimed to include true information, like interviews with scientists involved. However, their work was criticized for copying parts of a novel called Thin Air, which was published a year earlier.

Officials at the Fourth Naval District say the supposed event might have been a misunderstanding about normal research during World War II at the Philadelphia Naval Shipyard. One idea is that stories about the event began from experiments called degaussing, which made ships hard to detect by magnetic mines. Another possible source of stories about levitation, teleportation, or effects on crew could be experiments with the generator on the destroyer USS Timmerman (DD-828), which created electrical sparks, though no one reported harm from the tests.

Some people argue that unusual stories should not be believed unless there is clear proof. In 1980, Robert Goerman wrote in Fate magazine that "Carlos Allende"/"Carl Allen," who supposedly wrote to Jessup, was actually Carl Meredith Allen of New Kensington, Pennsylvania. Allen had a history of mental health issues, and some believe he made up the story about the experiment because of his condition. Later, Goerman learned that Allen was a family friend and someone who often shared strange ideas.

The USS Eldridge was not commissioned until August 27, 1943, and stayed in New York City until September 1943. The October experiment was said to have happened during the ship's first trip to the Bahamas, but conspiracy theorists claim the ship's records might be fake or still secret. They also suggest the USS Hammann (DE-131) might have been used instead of the USS Eldridge, as it arrived at the shipyard on October 20, 1943. However, this ignores the original story told by Carl M. Allen.

In 1996, the Office of Naval Research (ONR) said it never studied radar invisibility in 1943 or any other time. It also noted that the ONR was not created until 1946, and called the "Philadelphia Experiment" a complete work of fiction.

A group of Navy veterans who served on the USS Eldridge told a newspaper in 1999 that their ship never went to Philadelphia. More proof against the timeline of the "Philadelphia Experiment" comes from the USS Eldridge's full World War II report, including its 1943 deck log, which is available on microfilm.

Researcher Jacques Vallée describes a process on the USS Engstrom, which was next to the USS Eldridge in 1943. The process involved creating a strong electromagnetic field to make the ship undetectable by magnetic mines and torpedoes. This method was developed by Charles F. Goodeve, a Canadian, and used widely by the Royal Navy and others during World War II.

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

Vallée also mentions a veteran who served on the USS Engstrom and claims he was the person Allende saw "disappear" at a bar. He says that during a fight, bar staff helped him leave before the police arrived because he was too young to drink. They then told others he had disappeared to cover for him.