Just for a bit of fun out on your detective hats and try to come up with a reasonable assumption for these happening. Roswell Roswell is perhaps the most famous unexplained event of all. According to the US military, the debris recovered from a crash site near Roswell, New Mexico in 1947 was just the wreckage of a high altitude surveillance balloon. But thousands of people, including military personnel, refuse to accept that explanation. Why? In the days after the incident, the military first said they'd found a 'flying disk' on the site before quickly changing the story to say that it was balloon debris. Other witnesses have even suggested alien autopsies were carried out at Roswell. Aflockalypse now On January 1 2011 the residents of the quiet town of Beebe, Arkansas woke to find their streets strewn with dead birds. Conspiracy theorists were quick to point the finger at Satan, aliens or secret Government experiments. Experts took a more boring view. Some suggested the birds were victims of New Year celebrations, flying low to avoid firework explosions and crashing into telegraph polls and buildings. But other scientists admit the incident is hard to explain. "Science is struggling to explain these things," conceded a spokesman for the UN Environment Program. Buddhist Monks In 1985 a team from Harvard University witnessed a group of Tibetan monks sleeping in the open air. The odd thing was that this was 15,000 feet up in the Himalayas, on a freezing February night - and the monks slept peacefully without huddling or shivering, wearing only thin shawls. How did they do it? We simply don't know. But we do know that the monks practiced a kind of deep meditation called g Tum-mo. Other practitioners have been witnessed raising the temperatures of their fingers by as much as 17 degrees. Bigfoot Lots of people think there's no such thing as Bigfoot, the great hairy human ape-cross that is said to roam the forests of North America. But the sightings just keep coming. And even the most sceptical scientists have trouble dismissing them all as hoaxes (though some clearly are). The Bigfoot Field Researchers Organisation has been set up for exactly that reason. Missing man Plenty of people have disappeared without trace, their bodies never found. But deep mystery surrounds the fate of a man calling himself D.B. Cooper, who in 1971 carried out one of the most daredevil skyjackings in history. After hijacking Northwest Airlines flight 305 with threats of a bomb, Cooper pocketed $200,000 and parachuted into the night somewhere over the Pacific coast. Cooper has never been found - alive or dead - despite a huge manhunt. In 2007, the FBI released sketches of what Cooper might look like today in a futile attempt to finally crack the case. Atlantis The gleaming city of Atlantis is one of the most sought after 'lost cities' of all time. But did it ever exist? Ancient Greek philosopher Plato, for one, mentioned the city in his works. Others believe Atlantis is purely mythological. But that hasn't stopped hundreds of expeditions combing the Earth in an attempt to find it - with a number claiming (unsubstantiated) success. Bermuda Triangle The loss of a large number of planes and ships in a triangle-shaped portion of the western Atlantic Ocean has become an enduring mystery. Notable losses in the include the USS Cyclops, the single largest loss of life in the history of the US Navy in peacetime, and Flight 19, a training flight of aircraft that were all lost without trace in 1945. Stonehenge The giant stone ring near Aylesbury in Wiltshire has been the subject of intense speculation for centuries. We are still not certain how it was made or what it was for. In the past, many authors questioned the ability of ancient Britons to move and erect such enormous stones, leading to speculation about a demonic or extraterrestrial origin. Recent experiments have shown that contemporary human technology made Stonehenge just about viable. But why go to all that trouble? Theories about the purpose of Stonehenge include an astronomical observatory, a religious site and a place of healing. But experts still debate the issue. The 2012 prophesy Lots of people are getting pretty fidgety at the moment, because according to one interpretation of an ancient Mayan calendar the world is due to end in December 2012. And will it? There have been plenty of unfulfilled doomsday prophecies before, so why has this one caught the public imagination? Partly it's because a Mayan calendar does exist, and appears to end this December. But experts say that the Mayans created calendars to track time, not to predict the future. How much of a mystery this prophecy turns out to be....well, we'll find out soon enough. Mary Celeste The Mary Celeste was an American sailing vessel bound for Italy that was discovered abandoned in the Atlantic Ocean in 1872. The crew were never found. Mystery surrounds the doomed ship because the weather was fine, there was no sign of a struggle on board and the crew were all experienced seamen. There seemed no reason to abandon the seaworthy ship, and cargo and valuables were untouched, ruling out pirates. To this day, nobody knows what happened to the crew and passengers of the Mary Celeste. http://extras.uk.msn.com/advertorials/wagon-wheels/10-strangest-unexplained-mysteries.aspx Some of this is pretty difficult to come up with rational explanations for although others are likely to be scams. Feel free to add your own.