Sept. 20, 2007 -- When the former Soviet Union launched the world's first satellite into orbit 50 years ago, most people in the United States were filled with shock and dread that their Cold War foe would soon follow up with nuclear-tipped missiles.
But members of the science community were distracted by a more immediate situation: trying to figure out why the little spacecraft's beep varied as it periodically flew overhead.
With its 1 watt of power, Sputnik, which means "companion" in Russian, transmitted radio signals for three weeks after reaching space on Oct. 4, 1957.
While schoolchildren practiced bomb drills, scientists and amateur radio operators studied the signals, which changed as they passed through different parts of Earth's outer atmosphere, the ionosphere, which contains particles ionized by solar radiation.
The early insights into Earth's ionosphere were quickly eclipsed by the discovery of radiation belts surrounding the planet, credited to astrophysicist James Van Allen. The discovery was made by the first U.S. satellite in orbit, Explorer 1.
Though it flew less than four months after Sputnik, the Soviets had already launched its second satellite, Sputnik 2, which held the first living being into space, a dog named Laika.
Today, robotic space probes have visited, or are en route to, every planet in the solar system as well as a few asteroids and other destinations. The earliest satellites have left the solar system entirely and are entering interstellar space.
Closer to home, a space station is under construction, spearheaded by the United States and Russia, which have been sharing living quarters and work in orbit for more than a decade.
"Sputnik was the enabler. It really got people thinking," said Alan Stern, NASA's associate administrator for science. "It sparked the Eisenhower administration, which in turn sparked the Kennedy administration, into a space race which has given us everything from the microelectronics revolution, to the discovery of the ozone hole and global change, to really understanding our place in the universe."
Scientific roots
Though the political ramifications of Sputnik's flight overshadowed its scientific value, the spacecraft's roots actually began at a high-profile international quest for knowledge about Earth.
In 1952, the International Council of Scientific Unions planned a series of coordinated observations and experiments to take place between July 1957 and Dec. 1958, under a program called the International Geophysical Year.
In addition to measurements at the polar caps, atmospheric research, oceanographic studies and solar observations, scientists decided to make use of rocket technology developed after World War II to try to put an artificial object into orbit.
"At the time, the International Geophysical Year was the largest collaborative scientific endeavor in history," said Scott Curtis, head of reference at the Linda Hall Library of Science, Technology and Engineering in Kansas City, Mo.
Few expected the Soviets to be first.
"It was a great political coup that the Soviets took advantage of to propagandize about the superiority of the worker state," said Curtis. "But it also had some scientific value in terms of studying radio signals and the ionosphere."
The real impact of Sputnik took weeks to manifest. Although mathematicians had proven decades earlier that artificial objects could be made to fly around Earth, most people had no understanding of the mechanics involved.
"When Sputnik first went over, Americans were expecting to have it fall from the sky," said Curtis. "It had a very practical impact."
The launch powerfully demonstrated the ability of missiles, which were under development in the United States and the Soviet Union, to carry objects beyond Earth's atmosphere.
"There's no question that (Sputnik) stimulated the urgency" of the U.S. program, the late Ruben Mettler, who spearheaded development of the U.S. ballistic missile program in the mid-1950s, said in an archived NASA Oral History interview.
"Schedules were shortened. I can recall ...one trip that (Air Force Gen. Bernard) Schriever made to Washington at that time. He came back and he said, 'Your schedule is now one year earlier than it was,' and that went through the whole program," he said.
Until Sputnik, the U.S. missile program was focused on low-altitude, air-breathing vehicles. Plans for a long-range intercontinental ballistic missile were not in the national program, according to Mettler.
Sputnik changed everything. The United States immediately began working in earnest to put a man on the moon and created a civilian space agency, NASA, to handle the job. NASA met its goal in 1969 and went on to land five more crews on the lunar surface before the Apollo program was canceled in the early 1970s.
On the 50th anniversary of Sputnik's launch, NASA ironically finds itself with the same goal.
Editor's note: This is the first of a three-part series on the history of Sputnik and its legacy. Part II: Next week — the new space race.
Related Links:
Listen to an audio history of Sputnik.
The Smithsonian National Air and Space Museum's Sputnik page