The Strangest Unexplained Phenomena in History

Mary Celeste ship

Everyone loves a good mystery, especially when it’s real. Of the countless happenings that have confounded us through the years, decades, and centuries, some mysteries have endured longer than others. Here are four unexplained phenomena throughout history that we may never fully understand, but will always be fascinated by.

Medieval Dancing Plagues

There have been several outbreaks of choreomania, the technical term for dancing mania, none of which has ever been conclusively explained. Among the most famous is the one that took place in Strasbourg, then part of the Holy Roman Empire and now part of France, where a “dancing plague” lasted for weeks in 1518. First on the dance floor (read: city square) was one Frau Troffea, who danced until she collapsed from exhaustion one extremely hot day in July; after recovering her strength, she resumed her rug-cutting. She and the 30 or so others who joined in over the next week in a variety of public locations seemed unable to stop, as though their movements were involuntary. The “plague” lasted until early September, by which time at least 400 people had joined in. Many were injured, and some didn’t live to tell the tale.

This wasn’t the only dance plague to occur in medieval and early modern Europe. Similar events took place throughout the Holy Roman Empire as well as in Germany, Switzerland, and France, though none were documented as thoroughly as the one in Strasbourg — it even inspired a recent novel. No one is sure, all these centuries later, why any of this happened in the first place. Many contemporary explanations were religious and/or superstitious in nature, whereas more modern theories suggest that a mold called ergot might have been responsible. As with many phenomena from ages past, we may never know the full story.

Photo credit: Keystone/ Hulton Archive via Getty Images

Australia’s Missing Prime Minister

We may not know the full circumstances surrounding the assassination of John F. Kennedy, but at least we know that he was assassinated. Australians have received no such closure in the matter of Harold Holt, who served as the country’s 17th prime minister from 1966 until his disappearance and presumed death the following year — presumed, not confirmed, because no one has ever been able to definitively say what happened to him. Holt, an avid outdoorsman, swimmer, and spearfisher, went swimming in the sea near Portsea, Victoria, shortly after noon on December 17, 1967, and disappeared shortly thereafter. According to a witness named Marjorie Gillespie, with whom Holt happened to be having an affair, the rough waves took him “like a leaf being taken out… so quick and final.”

While the simplest and most likely explanation is that Holt drowned, his body was never recovered despite extensive search-and-rescue efforts. The enormity of a world leader disappearing in this fashion is difficult to overstate, and a number of theories had already emerged by the time his funeral was held days later. Some of these were relatively plausible, such as the possibility that Holt had either taken his own life or faked his death, while others were less so — some thought he had been assassinated by either the CIA or North Vietnamese, and in 1983 a British journalist named Anthony Grey even accused Holt of being a lifelong spy for China in his book The Prime Minister Was a Spy. Said tome was widely discredited, but that doesn’t mean no one believed it.

The “Wow!” Signal

People have speculated about intelligent life elsewhere in the universe for thousands of years. That interest reached new heights in the 20th century, when emerging technologies gave rise to the space race, science fiction movies, and radio telescopes designed to detect signals from cosmic sources. On August 15, 1977, one of them picked up something so strong it made Jerry R. Ehman of SETI (Search for Extraterrestrial Intelligence) simply write, “Wow!” on the computer printout when he saw it a few days later.

Detected by the Big Ear radio telescope at Ohio State University, the signal sequence lasted a full 72 seconds and had all the signs of emanating from extraterrestrial sources — including the fact that it appeared to originate from the Sagittarius constellation. It was by far the most powerful signal Big Ear ever received in its 35-year existence, but it was also a one-off. Subsequent attempts to detect it again were all unsuccessful, as were efforts to determine what exactly caused it. According to Seth Shostak of the SETI Institute, “Nobody has ever found another explanation for what that might have been. It’s like you hear chains rattling in your attic and you think, ‘My god, ghosts are real.’ But then you never hear them again, so what do you think?”

The Mary Celeste

On November 7, 1872, the Mary Celeste set sail from New York en route to Genoa with 10 souls onboard: Captain Benjamin Spooner Briggs, his wife Sarah Elizabeth Cobb, their 2-year-old daughter Sophia, and seven crewmen. Less than a month later, on December 4, the ship was discovered adrift near the Azores Islands with no one on it. This, despite the fact that the Mary Celeste was still seaworthy with its cargo intact and its inhabitants’ belongings undisturbed. The lifeboat was missing, and neither Briggs nor anyone else who left on that fateful voyage was ever seen again.

A hearing held to determine whether the crew of Dei Gratia, the brigantine that discovered Mary Celeste, were entitled to a salvage reward ultimately ruled out such nefarious possibilities as mutiny and piracy. There are countless other theories as to what happened aboard the ship (are you sensing a trend here?), some more natural than others: Suggestions include a waterspout, earthquake, or other event that caused Briggs to fear that the alcohol his ship was carrying would explode. (As ever, some attribute the situation to a giant squid, kraken, or other sea beast.) Though it’s unlikely we’ll ever know what happened, the sea’s status as a cruel mistress remains unquestioned.