Things have happened fast. And yet, we're way behind schedule.

Look at how quickly progress has come in the world of computers. Forty years ago, you needed a room-sized machine to do what can be done today on a battery-powered laptop. Today, computing power doubles every 18 months while its cost spirals down. And the result is a tangible transformation of everyday life. Just one example: Americans now send more e-mail messages on a daily basis than letters sent through the U.S. Mail.

Forty years after humans first flew in space, though, things aren't nearly as far along. People havent been to the moon since the Apollo missions ended in 1972, and there are no firm plans to send them there, or on to Mars. Spaceflights for average citizens, like the Pan Am shuttle envisioned in the movie "2001: A Space Odyssey," dont exist. There is exactly one space tourist, California millionaire Dennis Tito, who plans to visit the International Space Station later this month. To most people, space is still a distant and mysterious frontier.

What went wrong? Is it a matter of money? Sending people into space is still so costly that only governments can afford to do it. When the Space Shuttle made its maiden voyage, 20 years ago today, NASA hoped it would lower the cost of getting into Earth orbit. But today, after more than 100 missions, the shuttle is just as expensive to fly as the giant, throwaway boosters it was supposed to replace -- about $400 million per launch.

Is it the danger? So far, a dozen astronauts, including the seven-member crew of the Space Shuttle Challenger, have died in the act of exploring space. The shuttle is safer and more reliable now than it's ever been. But riding a rocket the size of a grain silo will never be without deadly risk.

Or is it that exploring space isnt important enough to us? With the demise of the Soviet Union and Russias subsequent economic decline, the United States is the worlds premier spacefaring nation. But we dont act like it. In the last election neither George W. Bush nor Al Gore said more than a few words about space. In the last decade NASA has had to do more with less money, until now, faced with cost overruns on the space station, the agency is forced to choose between completing the orbiting complex or planning for tomorrows explorations.

So far, the promise of spaceflight -- as an uplifting experience available to average people, as a means of transforming life on Earth, and redefining our place in the universe -- is mostly unrealized. And it must not remain so. In this century, the same kind of hard work, ingenuity, and persistence that got us to the moon should be applied to building a civilization in space. We should go back to the moon, to decode its precious secrets on the origin of the solar system. We should go to Mars to search for signs that life may have existed there -- or may still. And we should explore the asteroids, which may offer a bounty of raw materials for our activities in space and even here on Earth. And after we have done all these things, our descendants will be thinking about even farther journeys, to other stars.

The flight of Yuri Gagarin was just the first step on a journey that has no end. It is a journey we human beings are compelled to make. To understand why, look up into a starry sky some night and remind yourself that the atoms in your body were formed out there, in those celestial fires. To journey into space is to return to the place where it all started.

So, let's go.