BERLIN -- It was here that the Society for Space Travel was founded in 1927, by a trio of enthusiastic kids and a visionary professor interested in the possibilities of liquid fuels.

As  Otto Friedrich tells it in Before The Deluge, "They gathered in an abandoned arsenal in the northern suburb of Reinickendorf, named its three-hundred-acre field the 'Rocket Airport,' and fired their miniature missiles at the moon."

Among the most enthusiastic members was an 18-year-old engineering student named Wernher von Braun. His imagination had been fired by a magazine article about an imaginary trip to the moon.

"It filled me with a romantic urge," von Braun told Friedrich. "Interplanetary travel! Here was a task worth dedicating one's life to! Not just to stare through a telescope at the moon and planets but to soar through the heavens and actually explore the mysterious universe! I knew how Columbus had felt."

All that is history now. The story, for example, of how Germany Army recruited von Braun and the others because partly rockets hadn't been prohibited by the agreement that ended World War I.

Of how the world first learned of "guided missiles" when V-1 "buzz bombs" and V2 rockets began landing on London during World War II, launched from sites in Holland and France.

Of how near the end of the war the Americans spirited von Braun and much of the rest of his team away from the advancing Russians to Huntsville, Alabama (and quietly swept under the rug the story of the slave labor on which German rocket science had relied).

Of how inter-continental ballistic missiles quickly became dominating technology of the Cold War, driving the Space Race and the Apollo missions to the moon.

Of the revolution in computer technology that the Cold War produced, and the whole new toolbox of planning techniques that rocket science has furnished to the worlds of business and economics.

"We were interested solely in exploring outer space," von Braun told Friedrich. "It was simply a question with us of how the golden cow would be milked most successfully."

About the same time that von Braun began experimenting with rockets in Berlin, James Van Allen was taking apart and reassembling a $50 Model T Ford with his brother in Mount Pleasant, Iowa.

Twenty-five years later, it was Van Allen who devised the American response to Sputnik -- the package of instruments in its Explorer satellite a few months after the Soviet surprise. One of its first discoveries was that of radiation belts surrounding the earth.

For a little while, it was thought that these layers of ionized gas might bar humans from going beyond their boundaries into space. A little further work demonstrated they would pose no problem. The discovery of the previously unknown "Van Allen Belts" put the University of Iowa scientist on the cover of Time magazine. That was nearly half a century ago.

Earlier this month, in a poignant letter to Science magazine, Van Allen sought to pronounce a benediction on von Braun's vision of manned "interplanetary travel." The leap into space had truly revolutionized our understanding of the physical universe, he noted.

But almost all of the space program's important advances in human knowledge and in civil and military applications have been accomplished by hundreds of robotic spacecraft. It was time to ask, he wrote, "Is human space flight now obsolete?"

True, Van Allen acknowledged, the subsequent repair and service of the Hubble Space Telescope by skilled crews was an example of the utility of humans in space. And about the raging debate in military and political circles about various approaches to missile defense, he had nothing to say. But the space shuttle's contribution to science had been modest, he wrote, and, to technology, negligible.

And for the rest -- the plans envisaged by President Bush in January for a return to the moon and for manned missions to Mars -- "the only surviving motivation for continuing human spaceflight is the ideology of adventure," he continued.

Only a tiny fraction of the earth's 6 billion inhabitants are involved. For everybody else, it is like watching a science fiction movie -- and, he might have added, an increasingly outdated one at that.

Van Allen supplied a useful parallel. "In the 1930s, there were glowing expectations for high-altitude, manned balloon flights, but it soon became clear that such endeavors had little scientific merit. Unmanned high-altitude balloons continue to provide valuable services to science, but manned ballooning has survived only as an adventurous sport."

It is in this context that the flurry of recent news about the "X Prize" should be understood. At least twenty teams are competing for $10 million prize for the first private vehicle that, within a period of two weeks, twice flies three people to a sub-orbital height of 62 miles (100 kilometers) on consecutive flights.

This is no new chapter in the history of "privatization." A handful of St. Louis aerospace entrepreneurs and a credit card firm are behind the X Prize Foundation. "Space tourism" is their goal.

The debate about how and when to replace the expensive and dangerous "space shuttle" will continue. But it has almost nothing to do with going to Mars. The next step in manned space flight is the hobby-ization of an outmoded technology, like ballooning and solo sailing around the world.

Meanwhile, ideology of adventure has pretty well shifted to the research being done on climate change, often in remote locations around the world. The discovery of global warming is one of the great stories of the last fifty years.

It was in that same exciting year that saw the launch of Sputnik that the Scripps Institution of Oceanography hired Charles Keeling to measure carbon dioxide in the earth's atmosphere at the Mauna Loa Observatory in Hawaii.

The Keeling curve, showing a 15.2 percent increase is CO2 in the middle of the Pacific Ocean between 1959 and 1997, is now as central to humankind's story in the 21th century as were the first demonstrations of the atom bomb or the landing on the moon in the last one hundred years.

Ahead are undertakings every bit as challenging as the Manhattan Project and the Apollo Program. There is plenty of adventure here for anyone who wants to dream big dreams.