Manned space flight's 50th anniversary

The late Soviet cosmonaut Yuri Gagarin is being honoured around the world Tuesday on the 50th anniversary of his pioneering flight in space.

"He is a human who made the first-ever step into outer space, which became a milestone for humankind at large," saidcosmonaut Dmitry Kondratyev, commander of the current mission at the International Space Station, from orbit.

He and thefive other astronauts aboard the space station held a news conference with space agencies around the worldTuesday as part of their celebrations.

Gagarintook off aboard a Soviet Vostok capsule on April 12, 1961, and completed nearly a full orbit of the Earth over 108 minutes.

The achievement, during the height of the Cold War, stunned people around the world, said Canadian astronaut Chris Hadfield.

"It was a revelation to know that you could look up and people were leaving our planet only very briefly and only very experimentally but still, we'd figured out a way to do it for the first time," Hadfield said.

American Alan Shepard became the second man in space, 23 days after Gagarin's flight.

Four years earlier, the Soviet Union had beaten the U.S. by launching Sputnik 1, the first artificial satellite to orbit the Earth, but that didn't have the same impact.

"Sputnik was a 'thing' in space, but Gagarin was another human being, and a wide-smiling, looks-like-anybody's-country boy," Hadfield said. "It suddenly made it real for people."

Gagarin's photo is the only astronaut portrait on the wall in the central section of the space station, said Hadfield: "Because we recognize that he is the one who opened the door for all of us."

Since Gagarin's voyage, more than 500 astronauts from countries around the world have left the Earth. Some have walked on the moon. Many, including Hadfield, have lived and walked in space.

Piers Bizony, co-author of the bookStarman: The Truth Behind the Legend of Yuri Gagarin, said Gagarin was a military pilot posted north of the Arctic Circle in 1959 when a recruiting team came by looking for candidates to fly "what they called a new kind of machine."

Gagarin said it sounded interesting and signed up despite the dearth of details offered.

Proof that humans could survive space

He went through very rigorous training involving many psychological and medical tests because, at the time, no one was sure what space flight would do to the human body. Gagarin's flight answered a lot of questions.

"He proved that human beings could survive weightlessness," Bizony told CBC's Quirks & Quarks. "He proved that they could survive the experience in space without going crazy."

Hadfield said he was most impressed by Gagarin's return through the atmosphere, back to Earth.

"He came hurtling in, they opened a small parachute on his capsule, and then he actually ejected from that several thousand metres above the ground while his capsule buried itself in the ground," Hadfield recalled Tuesday.

"He was a very brave man. But he had to be in order to take that first big step."

Cosmonaut Boris Volynov, who trained with Gagarin, remembers him as a man who was always smiling and very generous. Once, Volynov told CBC News in a recent interview, "Yuri noticed I was downso to cheer me up, he collected money from everyone and bought me a fridge. It was a rare commodity at the time."

Following Gagarin's return to Earth, he spent years being paraded around by Soviet authorities as an example of what could be achieved in the Soviet communist system.

Finally, he was allowed to return to his work, but died when his plane crashed during a training flight in 1968. Classified documents released by Russia on Friday indicate that the crash was likely linked to a manoeuvre to avoid a weather balloon, Agence France-Presse reported.

Though his career as a cosmonaut was short, he left a lasting legacy, Bizony said.

"He was and for as long as human beings still have the words to utter the phrase always will be the first man in space."