A few years after Bolshevik assassins herded Czar Nicholas II and his wife and five children into a cellar and opened fire upon them in July 1918, a woman who called herself Anna Anderson surfaced in Europe, claiming to be the czar’s youngest daughter, Anastasia. She said that she had been carried from the execution site by mysterious benefactors [source: Hogue].

Though rejected by Romanov relatives, her saga was sufficiently intriguing that Hollywood made it into a 1956 movie starring Ingrid Bergman. Rumors persisted that the young heiress to the throne had somehow escaped death. But in 1991, the mystery took another turn, when it was revealed that the bodies of most of the Romanovs and their servants lay in a mass grave in Yekaterinberg, Russia, but the bodies of a male and female child were missing [source: Maugh].

That faint hope that Anastasia had escaped was crushed in 2007, when archaeologists discovered a second grave containing two more youthful sets of bones. Like the first set, the new bones were matched with a sample of Nicholas II’s DNA, which had been extracted from bloodstains on a shirt worn during an 1891 assassination attempt. With all the Romanovs accounted for, it’s now clear that Anastasia died with her family [source: Maugh].

Unless you’ve never been near a drugstore paperback rack and don’t surf cable channels late at night, you’ve undoubtedly heard of the Bermuda Triangle, aka the Devil’s Triangle. It’s an area of water between Florida, Puerto Rico and Bermuda that, according to pop mythology, contains some sort of malevolent force that causes ships, planes and people to disappear, never to be seen again.

Some have put the blame on extraterrestrial invaders capturing humans for study, on inter-dimensional vortices and even on oceanic flatulence (methane gas erupting from ocean sediments) [source: NOAA].

But the real mystery of the Bermuda Triangle is why people are still so eager to believe in it. Back in 1975, librarian and pilot Lawrence David Kusche published his investigation of the phenomena. When he actually reviewed the official reports on ships that paranormal authors had depicted as vanishing inexplicably, he found that they usually sank in bad weather or suffered explainable accidents, and that wreckage sometimes was recovered [source: Nickell].

Similarly, the U.S. Coast Guard’s website notes that the service “does not recognize the existence of the so-called Bermuda Triangle as a geographic area of specific hazard to ships or planes,” and says that after reviewing accidents there, nothing has been found that couldn’t be explained.

For a long time, people have puzzled about one of the freakiest societal collapses in human history. Why did the Maya people abandon dozens of cities they’d built in the Yucatan peninsula in the 700s or 800s C.E., and allow what had been a highly developed civilization to turn into ruins?

Some have theorized that the Maya were probably defeated in battle by rival peoples or that the ruling class was overthrown in a peasant revolt. Others have advanced more outlandish explanations, such as an invasion by UFOs [source: Stromberg].

But in a study published in 2012, Arizona State University researchers, who analyzed archaeological data with an eye to figuring out environmental conditions in the Mayan heyday, found evidence to substantiate a theory first advocated by historian Jared Diamond in his 2005 book “Collapse.” The Maya, the researchers discovered, had burned and chopped down so much of the forests that they had altered the land’s ability to absorb solar radiation, which in turn made clouds and rainfall scarce. That exacerbated a naturally occurring drought, and caused erosion and soil depletion, which caused agriculture to fail. With less food available, workers were forced to leave the lowland cities to avoid starvation, and everything collapsed as a result [source: Stromberg].

One of the weirdest enigmas of the 1963 assassination of President John F. Kennedy in Dallas was the presence of “umbrella man.” This blurry figure is seen in photographs raising a black umbrella along the presidential route, even though the sky was clear. Some saw him as proof of a conspiracy — an advance man who was signaling the sniper. Others suspected that he might actually be an assassin himself, firing a poison dart gun concealed in his parasol [source: Jonsson].

But when the U.S. House of Representatives reopened the JFK investigation in the late 1970s, a 53-year-old Dallas warehouse manager named Louie Steven Witt came forward and testified that he was “umbrella man.” Granted, his explanation was a bit bizarre: Witt disliked JFK’s father, former U.S. ambassador to the United Kingdom Joseph P. Kennedy, whom he faulted for supporting British Prime Minister Neville Chamberlain’s appeasement policies toward Hitler. Chamberlain’s trademark was his ever-present umbrella, and Witt chose that day to brandish a big, conspicuous one in an effort to needle the president. He brought along a visual aid to the hearing — a battered black umbrella that he claimed was the one he’d used that day. A committee staffer popped it open, to reveal that it didn’t contain a weapon [source: Jonsson].

Witt added, “If the Guinness Book of World Records had a category for people doing the wrong thing at the wrong time in the wrong place, I would be No. 1” [source: Jonsson].

One of the biggest enigmas about Stonehenge, the massive prehistoric stone circle that was erected in England between 3000 and 1520 B.C.E., is the origin of the massive sarsen stones that are arranged in a post-and-lintel formation [sources: Pearson, Hershberger]. Where did the 23-foot (7-meter)- tall, 22-ton (20-metric ton) pieces of silcrete, a sedimentary rock made up mostly of quartz, come from? Scientists had been trying to solve this mystery for 400 years. It was believed that the stones came from somewhere in north Wiltshire, a county in southwest England, but they couldn’t pin down a precise location.

Then, in 2019, researchers had a stroke of luck when a man who had worked on a restoration project at Stonehenge in 1958 provided them a 42.5-inch (108-centimeter) long, roughly 1-inch (25-millimeter) thick core that had been extracted from one of the sarsens, which he had taken back to the U.S. with him. Scientists were able to do tests on the sample and create a geochemical fingerprint of the sarsens. Then, after analyzing similar stones from 20 different sites across southern England and comparing the chemistry, they narrowed down the source to West Woods in Wiltshire, today a popular recreational destination for hikers, dog walkers and mountain bikers. But how exactly the builders transported the stones to the site of Stonehenge, 15 miles (24 kilometers) to the south, remains a mystery [sources: Morris, Morris].

English explorer Sir John Franklin sailed to Canada in 1845 with two centrally heated ships, a crew of 128 and a three-year supply of food, hoping to find an Arctic route connecting the Atlantic and Pacific oceans (what we now refer to as the Northwest Passage). Instead, Franklin and his crew vanished. More than 30 expeditions looked for them — so many that the death toll for searchers actually exceeded the lost Franklin crew [source: RMG].

Finally, in 1859, skeletal remains were found, along with a log that stopped in April 1848. After Franklin’s ships had become stuck in the ice, the crew spent nearly two years trying to get them free, but after Franklin and 23 members died, the remainder set out on a doomed march across the Canadian tundra. Some resorted to cannibalism [sources: Gillis and Sorensen, RMG].

So, what went wrong? In the 1980s, a study by Canadian anthropologist Owen Beattie concluded that the explorers succumbed not to starvation or cold, but to diseases such as tuberculosis, after being weakened by poisoning from food cans with high lead content [source: Bayliss].

A subsequent 2013 study dissented in part, arguing that the high lead content in the bones probably came from lifelong exposure in cluelessly toxic mid-1800s England, not just from the cans. A 2018 study reached the same conclusion. These researchers reasoned that if the lead in food cans was the cause of death, then the ones who survived longest should have had the highest levels of lead. Also, the members of the expedition should have had higher levels of lead than a similar sample of British sailors living in Antigua at the same time. Neither was found to be true [source: Solly].

Researchers from the 2013 study attributed the crew’s demise to the consequences of two winters trapped on the ice and running short of food. “The surviving men had no option but to desert the ships and trek south to the mainland. But they were ill-equipped, and probably in poor health, so escape was beyond them. Their plight was desperate and all died in the attempt,” researcher Keith Millar told the Guardian.

Another part of the mystery was resolved in 2014, when a Canadian robotic submarine located the wreckage of one of Franklin’s ships under the Arctic ice [source: Gillis and Sorensen]. Divers are still excavating that ship every summer.

Since the 1940s, people have been scratching their heads about the apparently strange goings-on in a dry lakebed in Death Valley called the Racetrack Playa. There, every 10 years or so, stones as big as 700 pounds (318 kilograms) mysteriously seem to move around on their own, leaving long tracks behind them in the parched desert surface [source: Starr]. Over the years, various explanations— from dust devils to films of slippery algae — have been proposed, but none of them seemed too convincing.

Finally, though, in 2011, researchers from Scripps Institution of Oceanography at the University of California-San Diego decided to solve the enigma. Since the National Parks Service wouldn’t allow them to attach GPS devices to the rocks themselves, they brought in 15 similarly sized pieces of stone and monitored them. It took two years, but they finally got the answer. In wintertime, the playa sometimes fills up with a thin layer of water from rainfall, which freezes overnight and forms thin sheets of ice. When the sun comes out the next day, the ice melts and cracks into panels that light winds then blow across the ice, carrying the rocks with them. But the stones typically slide at a speed of only a few inches per second, slowly enough that visitors can’t really see the movement from a distance [source: Starr].

On June 30, 1908, a fireball streaked through the Siberian sky, followed by an enormous explosion that leveled 830 square miles (2,150 square kilometers) of remote forest. Scientists later calculated that the Tunguska event, named after a nearby river, released an amount of energy 1,000 times greater than the atomic bomb dropped on Hiroshima in 1945 and enough to kill 80 million trees. Weirdly, no crater was ever found [source: Anderson and Whitt].

It took researchers until 1927 to reach the remote site, and the inability to find a clear-cut impact crater or pieces of a meteor led to some fantastic theories, including scenarios involving antimatter and UFOs. Others suspected that Earth had been struck by a comet — since a comet is basically a ball of ice, it wouldn’t have left a trace. But in 2007, a team of Italian researchers used acoustic imaging to identify the crater, which turned out to be in a lake 5 miles (8 kilometers) north of the spot originally identified by scientists [source: Valsecchi].

Ukrainian researchers then proved that Tunguska was, in fact, caused by a meteor, according to a 2013 article in Planetary and Space Science. They analyzed samples of peat dating from that summer, and found it contained fragments of minerals found in meteorites, as well as lonsdaleite, a substance known to form from shock waves following an explosion. Just as significant, the combination of all these elements was nearly identical to a meteor impact site in Arizona [source: Redfern].

The English monarch Richard III, whom Shakespeare portrayed as a megalomaniacal, malevolent hunchback, is one of the most famous villains in history. But while we’ve long known that Richard met defeat and apparently suffered his demise at the Battle of Bosworth Field in 1485, it remained a mystery exactly how he died [source: Blaszczak-Boxe]. Was he killed in battle? And if so, what happened to his body, which was never found and identified?

After more than 500 years, those questions were finally answered. In 2012, an old grave was discovered under a parking lot in Leicester, England, and five months later, DNA tests confirmed that the bones buried there belonged to Richard III. Additionally, in a 2014 study published in the Lancet, researchers revealed that forensic evidence showed that Richard had suffered 11 wounds, including nine blows to the skull. The lack of defensive wounds on his arms or hands led researchers to conclude that he had lost his helmet or removed it during the fighting, and then was killed either in sustained combat with an opponent, or else had been set upon by multiple attackers. They also found that while Richard had a spinal deformity (scoliosis), he did not have a withered arm or a limp, as Shakespeare depicted him [source: Blaszczak-Boxe].

Back in the late 1960s and early 1970s, proponents of the hypothesis that human civilization had been jump-started by extraterrestrial visitors pointed to the Egyptian pyramids as persuasive evidence. The ancient Egyptians could not have moved those massive multi-ton stone blocks with just muscle power, they argued, and suggested that alien anti-gravity technology was a more, uh, plausible explanation [source: Shermer].

Fortunately, in 2014, University of Amsterdam physicists materialized to rescue us from paperback pseudoscience. By analyzing an ancient tomb drawing, they figured out that a large team of workers could have hauled the giant stone blocks on a sled, and poured water on the sand in their path to reduce the friction and make it possible to drag the blocks to the pyramid. A small amount of water would cause the sand to become glued together and create a sort of paved road. Other researchers also have suggested that the Egyptians used clay as a lubricant, and it may be that they used more than one method [sources: Chowdury, Fall et al.].