The Bermuda Triangle is a patch of the Atlantic Ocean, out at sea between Florida, Puerto Rico and the island of Bermuda. For many years people have told stories and written books about it. The name 'Bermuda Triangle' comes from a 1964 magazine article by a writer named Vincent Gaddis. Gaddis drew the Triangle by joining three points: Florida to Bermuda, Bermuda to Puerto Rico and Puerto Rico back to Florida; most modern maps follow his description. Even so, its edges are loosely defined, and writers draw it a little differently. No official maps mark its boundaries, and the U.S. Board on Geographic Names does not recognize the name or keep an official file on the area.

The legend's trail runs from a 1950 Associated Press story about five missing Navy planes, to a 1952 Fate magazine article called 'Sea Mystery at Our Back Door', to the name 'Bermuda Triangle' in Argosy magazine in February 1964. The first stop was a news story, the second a magazine article, and the third gave the place its name. A 1974 book by Charles Berlitz made the Bermuda Triangle famous. It claimed the lost city of Atlantis was somehow behind the disappearances; it was a best seller, and dozens more followed. A 1974 documentary, 'The Devil's Triangle', and Steven Spielberg's 1977 film 'Close Encounters of the Third Kind' helped spread the story.

Why did the story last? Science Focus says the legend lasted because people are drawn to mystery, so early reports of disappearances attracted wide attention. Once the legend was established, reporters were quick to blame more wrecks on the Triangle; the frenzy has since eased, perhaps because modern technology tracks ocean and air traffic more precisely. The librarian Larry Kusche concluded that a typical writer retold stories from earlier books and added details, so the stories grew like a secret whispered around a circle of friends.

In the 1970s a librarian named Larry Kusche checked the original records behind the Bermuda Triangle stories instead of just retelling them. He used Coast Guard records, weather records, maritime records at Lloyd's of London and newspaper stories from the time instead of hearsay. His book 'The Bermuda Triangle Mystery—Solved' (Harper & Row, 1975) found that many accounts of vanishings were based on inaccurate information or careless research. The method is the point: instead of asking what the stories say, he went to the records they claimed to be based on and asked what the records say.

The records told a different story from the legend in several ways. Kusche found that ships said to be lost in calm weather had actually met storms. He also found that some of the incidents in the stories happened far outside the Bermuda Triangle, and some did not happen at all. For some 'missing' vessels, the wreckage was later found miles away, a fact the stories left out. Records kept by the Aviation Safety Network and the U.S. Coast Guard link many of the reported disappearances to storms or to unsafe conditions on the ships and planes themselves.

One case in the stories is Flight 19. In December 1945 a flight of five Navy training planes, known as Flight 19, lost track of where it was over the Atlantic off Florida; its leader reported that the compasses seemed to be malfunctioning. The Navy's record said the Flight 19 planes were lost for 'causes or reasons unknown'. Kusche concluded that the Flight 19 training flight was lost mainly because the pilots lacked experience; he spent seven years researching it, including interviews and retracing the route. In the 1940s nobody could watch storms from space, since the first weather satellite was launched in 1960.

Skeptical writers add a point about logic. One skeptic compared looking for one cause of every Bermuda Triangle disappearance to looking for one cause of every car accident in Arizona. A skeptical writer notes that losses happen in the Triangle just as they do everywhere else on Earth, and that a similar share of losses worldwide are also unexplained. Many ships and planes travel through the Bermuda Triangle, so it is a busy part of the ocean, and with more ships and planes, the odds that something goes wrong for some of them are greater.

Official bodies have checked, too. NOAA, the U.S. ocean science agency, says there is no evidence that unexplained trouble happens more often in the Bermuda Triangle than in other busy parts of the ocean. The U.S. Navy and U.S. Coast Guard say there are no supernatural explanations for disasters at sea, and that nature and human mistakes together explain them. A skeptical writer says the U.S. Coast Guard does not treat the Bermuda Triangle as an area of special danger. Lloyd's of London, the ship insurance company, is reported not to see it as an especially dangerous place, and the Coast Guard has said that a review of many aircraft and vessel losses in the area found nothing that indicated anything other than physical causes.

Another check is to compare the Triangle with other waters. A 2013 WWF study of the most accident-prone waters for shipping did not list the Bermuda Triangle. It named the South China Sea and East Indies, the east Mediterranean and Black Sea, and the North Sea and British Isles as the hotspots for shipping accidents. WWF also reported in 2013 that the number of vessels on the world's oceans rose 20 percent in 15 years, from about 85,000 to 105,000, and that general cargo vessels account for 40 percent of ships lost at sea and fishing boats for nearly a quarter. Foundering, where a boat sinks because of rough weather, leaks or breaking in two, causes about half of all shipping accidents, according to WWF in 2013.

Checking the ocean is hard because the ocean is large and keeps moving. Earth's seas cover about 70 percent of the planet and average about 12,100 feet (3,700 meters) deep, so a lost boat or plane can leave little to find. The swiftly flowing Gulf Stream would quickly spread out any wreckage from an accident, making evidence hard to find. Observation has changed over time. NASA launched TIROS-1, the world's first successful weather satellite, on April 1, 1960, and NOAA's Satellite and Information Service chief said that before TIROS-1 'we were very local in our understanding' of weather, because satellites gave a view of clouds around the globe.

Weather deserves a look of its own. According to NOAA, most Atlantic tropical storms and hurricanes pass through the Bermuda Triangle area, and NOAA says the Gulf Stream can cause rapid, sometimes violent changes in weather. Brief, violent thunderstorms called meso-meteorological storms can spring up at sea without warning, disrupting ship communications and stirring up enormous waves, says Howard Rosenberg, a reporter and Navy veteran who wrote for the Naval History and Heritage Command. Before weather forecasts got better, ships in the area had less warning about storms than ships have today.

Some explanations were proposed and tested. Gas hydrate is an ice-like solid made of water and gas, such as methane, that can form in the sediments under the sea floor. A 2003 American Journal of Physics study found that a large bubble released under a model ship could make it lose buoyancy and sink, at least in principle. There are two scientific caveats about a methane explanation: the model experiment worked, but there is no evidence it ever actually happened. Studies by the U.S. Geological Survey record no significant methane releases in the Bermuda Triangle area in the past 15,000 years, and Earth scientist Benjamin Phrampus calls the idea 'an interesting theory and nothing more'.

Rogue waves are unusually large waves that appear among smaller ones: more than twice the height of the surrounding waves, often from an unexpected direction. Scientists often call a wave a rogue if it is 2.2 times as tall as the significant wave height, which is the average height of the tallest third of the waves in that patch of ocean. Rogue waves can appear even in calm seas; one 20-meter wave was met in 1986 by the ship SS Spray in the Atlantic's Gulf Stream. Scientists do not have many detailed shipboard measurements of rogue waves, because they tend to appear without warning and bobbing ships make poor observation platforms. Science Focus reports that laboratory simulations confirmed that giant waves would have ship-sinking power, but there is no evidence such waves actually occur in the Bermuda Triangle.

Compasses have their own history. Christopher Columbus wrote in 1492 that his compass readings were odd while he sailed through this part of the Atlantic. Some writers say true north and magnetic north lined up in part of the Bermuda Triangle long ago, which could have thrown off sailors' and pilots' navigation. NOAA says there is some evidence that in the Bermuda Triangle a magnetic compass sometimes points toward true north instead of magnetic north. Magnetic declination is the angle between magnetic north, where a compass points, and true north, the direction of the North Pole. In the 1940s, navigators relied on dead reckoning (working out position from direction and speed), celestial navigation, and then direction finders and radio range stations; over oceans, dead-reckoning errors were large. Navigators could aim deliberately to one side of a destination, so that when the island did not appear they knew which way to turn, to make up for large dead-reckoning errors.

A skeptical writer notes that unexplained does not mean unexplainable: it means that not enough evidence remained to learn what happened, which is common with losses at sea. A story that cannot be explained may be a story whose records are thin, and the way to tell is to go back to the records, as Kusche did.

Words to know

• hearsay: passed-on talk
• skeptic: careful doubter
• foundering: sinking
• buoyancy: ability to float
• caveats: warnings