There are key moments in spaceflight's history that, in retrospect, defined the subsequent course of events. Take Yuri Gagarin's orbital flight in 1961, for example.
When Gagarin became the first man in space, America responded with the manned lunar landing challenge, which led to the Apollo program. But what if Gagarin hadn't been first? What if American astronaut Al Shepard became history's first man in space? It's an interesting question, one that conjures an alternate reality where we may not have gone to the moon at all.
PHOTOS: The Gemini Missions: Paving the Path for Apollo
The Space Age, and the Space Race, was in its infancy in 1959. And the two major players were more or less on par. Both the United States and the Soviet Union had launched satellites, were actively training astronauts and cosmonauts respectively, and neither was quite ready to launch a manned mission.
With little reason to suspect the pace of space exploration would soon go into overdrive, NASA was looking forward to a measured and deliberate plan to extend man's reach into the cosmic ocean.