The world’s first artificial satellite took to the sky at 1928 hours GMT on the evening of 4 October 1957. It circled the globe in less than 2 hours. When news of the first spaceflight was broadcast by Radio Moscow shortly afterward, the Earth had become a smaller planet overnight. The first orbit of Sputnik 1 was a shot heard around the world. It changed everything in its path; and like all revolutionary acts, its consequences were profound.

Worldwide, the reaction from the public was astounding. The news media went into paroxysms of speculation. Governments convened emergency sessions. Military services went on high alert. To the nations of the Western Bloc at the height of the Cold War, the 83.6-kilogram metal ball was a shock to the system. Globally, the balance of power had tilted perceptibly. No one knew what would happen next.

There was one group that awoke on 5 October 1957 and had a very different reaction to the news on the radio: rocket scientists. In a quirk of history, on the day Sputnik took off, experts in the nascent field of spaceflight were assembling in Barcelona, Spain, at the annual meeting of the International Astronautical Federation. Just as they were unpacking their bags, they were jolted by word that their theories had become reality. To this assembly, there was only one response that seemed fitting: celebration. Despite the tension of the Cold War mounting all around them, hearing that a satellite was in orbit enthralled the gathered delegates to the 1957 Barcelona conference, no matter which nation they represented. The Space Age had begun for all.

Fifty years later, we can all look back and smile at some people’s overreaction to Sputnik. The “space race” it created would end in 1969 with Apollo 11’s successful mission to the moon. No nuclear-tipped missiles based on the rockets that propelled satellites would ever be used in anger. The Cold War would be resolved peacefully. Humans would come to consider living beyond Earth’s boundaries routine. And we would all become so accustomed to the new technologies the original demands of space put in place that we would take their creation for granted. But what was it like before moon shots and the International Space Station, before serious talk of a manned mission to Mars and a moon base? What was it like 50 years ago, the day Sputnik changed the world?

To get a feeling for what thoughts Sputnik evoked in the minds of those who were most keenly acquainted with the prospects of spaceflight in 1957, we asked a trio of legendary conceptualists to offer their recollections of the event: Arthur C. Clarke, the famous British author and futurist; Frederick C. Durant III, a gifted engineer, a test pilot, and a shepherd of the American space program; and Ernst Stuhlinger, a German-born American who came to the United States to help launch the first U.S. spaceflights. Fittingly, on 4 October 1957, they were all preparing to meet at the IAF convention in Barcelona. They offer three insightful perspectives from shared experiences.

To see all of Spectrum's special report Remembering Sputnik, 50 Years Later, go to http://spectrum.ieee.org/sputnik.