The moon landing. The shuttle. The Hubble Space Telescope. When people think of space exploration milestones, they almost always think of NASA. That's understandable - the United States ran a very ...

In this photo provided by NASA, astronaut Ed White performs the United States' first spacewalk on June 3, 1965, during the Gemini 4 mission. James McDivitt / AP The world’s first spacewalker was ...