Editor's note: The following is the introduction to the February 2015 issue of Scientific American Classics: Conquering Space.

I was eight years old when Neil Armstrong and Buzz Aldrin landed on the moon. As Apollo 11 touched down on that gray, cratered surface, I was already dreaming of following those astronauts into space. The moon missions made me—and millions of others around the world—feel as though we could do anything, go anywhere.

Twenty-five years after that first moon landing, I was flying onboard the space shuttle Columbia on a 15-day mission during which we conducted some 80 experiments in microgravity.

Space travel was unlike anything I could have imagined when I was a boy. It remained fantastic even after two more shuttle flights, a Soyuz flight and six months on the International Space Station (ISS).

I remember taking a space walk on the ISS. There I was, wrench in hand, tightening bolts on a new module. It was such a mundane task. But when I looked in one direction, there was Earth floating in vivid blues and greens. In the other direction, I could see the blackest black conceivable, punctured by unwavering pinpoints of starshine. It was intense and surreal.

You might have heard about a transformation that can occur when someone first sees Earth from space—how it becomes harder to think about “my country” or “my people” and harder not to think about “our planet.”

I can tell you, that transformation is real.

I came home with a different sense of our world. And I would wager that every single one of the 500-plus men and women who have traveled into space came home transformed as well. It is one of the reasons why I continue to believe that we need to keep sending humans into space as well as robots. The results are tangible: I have seen firsthand how projects such as the ISS can foster cooperation among countries and cultures that otherwise might find it easier to be enemies.

In fact, while working with Russian colleagues, I learned that even at the height of the cold war, people in the Soviet Union were as excited as Americans when men first walked on the moon. Despite the political motivations behind the space race, the realization of the dream actually transcended politics.

Humans have not been back to the moon since 1972. With our retreat to low-Earth orbit, I sometimes feel as though we have lost some of the globally galvanizing magic of traveling to space. But I think it is possible—and important—to recapture it. My conviction is not simply about space exploration as a foreign policy tool. It is also about doing valuable science.

It took a lot of science to get people into space—this issue is testament to that. But science does not just drive space travel—space travel also drives science.

I worked on biomedical experiments while on the ISS that are already changing medical scanning and diagnosis back here on Earth. We did ultrasound scans in space, beaming the data back to Earth where specialists could analyze them remotely. Remote diagnosis is handy for astronauts and for the billions of people who live in rural areas, far from the nearest medical expert.

The low-gravity, low-temperature environment helps us unlock new information about phenomena such as superconductivity. We can grow crystals, mix fluids and create alloys that would be impossible on Earth. And of course, we are increasing our understanding of the long-term effects of space travel on the human body.

That is just on a space station. Who knows what we might find by returning to the moon, pushing on to Mars and even beyond?

I am also excited by the emergence of commercial space travel. Even with setbacks such as the recent fatal crash of Virgin Galactic’s SpaceShipTwo, it seems inevitable that tourists and private citizens will join government and military personnel in the journey to space.

Each new advance brings us closer to the day when the rare experience I have been lucky enough to enjoy becomes widely available. And I firmly believe that when thousands or even millions of human beings begin rocketing out of the atmosphere, space will continue to work its transformative magic. And what could be better for the future of the human race than to have a critical mass of people who see the entire planet as a unified home for all of humanity?

>>Buy this Issue: Conquering Space