By Matt Blitz - Via Popular Mechanics April 2016 From Popular Mechanics On April 12, 1961-55 years ago today-Russian cosmonaut Yuri Gagarin launched into the great beyond, becoming the first human in space. When he came back to Earth, Gagarin was looked upon as not just a hero, but the very embodiment of the Soviet Union's power. Streets were named after him. Monuments were erected. Khrushchev called him the Russian Christopher Columbus. And then he was gone. Less than seven years after his history-making mission, Gagarin died in a plane crash at only 38 years old. The cosmonaut and his flight instructor Vladimir Seryogin were flying a routine training exercise when they were lost, and the mysterious circumstances of the wreck have inspired a half-century of wild speculation. With little more than Soviet-sponsored reports, KGB investigations, and long withheld testimony as explanations, conspiracy theories sprung up to explain why a plane piloted by two experienced Russian airmen