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Reaching for the StarsApril 12 marks two huge milestones in the history of human spaceflight. On that date in 1961, the Soviet Union's Yuri Gagarin became the first person in history to reach outer space. And exactly 20 years later, NASA launched the first space shuttle mission, debuting the workhorse vehicle that would carry astronauts to and from low-Earth orbit for the next three decades.
There have been a lot of other "firsts" in the 50 years of human spaceflight. Here's a look at some of the top milestones, from Gagarin's historic flight to humanity's first steps on the moon to the birth of space tourism.
The First Human in SpaceSlide 2 of 31
The First Human in SpaceOn April 12, 1961, humanity slipped Earth's surly bonds for the first time in our species' history. Cosmonaut Yuri Gagarin launched into space inside a spherical Vostok 1 capsule, orbited Earth once during a 108-minute flight, then landed safely in a Russian field.
The flight was a major milestone for humanity, and another victory for the Soviet Union in its escalating Cold War space race with the United States. In October 1957, the Soviets had stunned the U.S. by placing the first artificial satellite, Sputnik 1, in orbit around Earth.
Gagarin became a global celebrity after his return to terra firma. But he didn't live to see some of the other human spaceflight achievements his mission helped set in motion, such as humanity's first steps on the surface of the moon. Gagarin's plane crashed during a military training flight in March 1968, killing the cosmonaut at the age of 34.Slide 3 of 31
An American in SpaceSlide 4 of 31
An American in SpaceLess than a month after the Soviet Union's Yuri Gagarin became the first person in space, the United States countered with a manned mission of its own. On May 5, 1961, NASA astronaut Alan Shepard launched aboard the Freedom 7 vehicle, becoming the second human being in space.
Shepard's suborbital flight lasted only 15 minutes, carrying him to an altitude of 115 miles (185 km). He splashed down in the Atlantic Ocean just 302 miles (486 km) downrange of the Florida launch site. But the short trip marked the U.S.'s human spaceflight debut, laying the foundation for longer, more ambitious jaunts down the road.
The flight also showed that humans can pilot a vehicle during weightlessness and the rigors of re-entry. Shepard controlled many of the Freedom 7's movements, while Gagarin's flight was more automated.Slide 5 of 31
The First Woman in SpaceSlide 6 of 31
The First Woman in SpaceSpace travel started out as an exclusively male endeavor, but it didn't stay that way for long. On June 16, 1963, the Soviet Union's Valentina Tereshkova became the first woman in space.
The 26-year-old Tereshkova piloted the Vostok 6 vehicle, completing 48 orbits of Earth and staying in space for nearly three days. Upon landing, she became a national hero, like her countryman Yuri Gagarin.
The first American woman didn't reach space until two decades later, when Sally Ride flew aboard the space shuttle Challenger in 1983.Slide 7 of 31
The First SpacewalkSlide 8 of 31