Photo: The Apollo 11 command module over the lunar surface. Credit: Space Frontiers/Hulton Archive/Getty Images

Nearly four decades have passed since humans last walked on the moon. Sure, we've talked about going back ever since, but we're still waiting for someone to step up to the plate and repeat that “one giant leap for mankind."

Why did we travel to the moon to begin with? To answer that question, I talked to Roger D. Launius, senior curator of the Smithsonian's National Air and Space Museum.

“The driving reason was Cold War competition with the Soviet Union," Launius said. “Without that, it wouldn't have happened."

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The 1960s were largely defined by global friction between the world's leading superpowers. While not engaged in direct armed conflict, the Soviet Union and the United States were each building an argument for supremacy. Each side made its case through technological advancement, political expansion and proxy wars such as the Vietnam War.

So when President John F. Kennedy announced on May 25, 1961, America's intention to go to the moon, it was more about showing up terrestrial enemies than exploring an extraterrestrial world.

“It was designed to solve a political problem, that's really what it was about," Launius said. “It was a Cold War competitive measure in response to a couple of major foreign policy setbacks in the spring in 1961."

For starters, cosmonaut Yuri Gagarin became the first human in space on April 12, 1961. Then, on top of this huge scientific and engineering accomplishment, that same month saw the failed Bay of Pigs invasion. Cuban forces crushed a CIA-backed, paramilitary force of Cuban exiles.

In other words, Americans felt like their communist adversaries had them on the ropes. They needed to land the mother of all punches. If they couldn't be the first in space, they could try to beat the Russians to the moon.

“So we decided to engage in this major scientific and technological endeavor and prove to the world that we were second to none," Launius said.

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Many historians also connect America's quest for the moon with humanity's natural inclination to explore and expand. And certainly, the moon had been tempting humanity since the dawn of time. Even at the time, however, scientists didn't agree that the moon was worth visiting.

“Most scientists were not focused on the moon, and a lot of scientists thought it was a waste of time and energy and never really did get onboard," Launius said.

Driven by political competition, the U.S. and Soviet space agencies both set their sights on the moon — ultimately resulting in one of humanity's true landmark achievements. But did the average citizen realize the Cold War forces driving the space race?

“In the back of most people's mind, they recognized there was a space race going on," Launius said. “And clearly if you read the newspapers, you got that sense. There were a lot of cover stories on the moon race or the space race in magazines like Time and Newsweek. But it probably didn't dominate most people's thinking."

When future generations look back on the events of the 20th century, however, Launius insists that the race to the moon will stand out like a diamond in the rough.

“There will be probably just a few things that almost everybody will be taught in school about the 20th century: the atomic bomb, Nazis, the two World Wars and the moon landing," Launius said. “I don't think there's any doubt that the moon landings will be among those. It's also, by the way, the only positive one."