AS America debates whether to celebrate or condemn the upcoming 500th anniversary of the voyage of Columbus, I often hear people complain that there is nothing left to discover. The entire world has been charted, they moan; there is nothing new under the sun.Contrary to these naysayers, I believe the spirit of exploration is alive and well. As a journalist, I have been fortunate to meet a few of our greatest contemporary explorers. These people - unlike the conquering "heroes" of centuries past - are approaching discovery with the noble goal of increasing human knowledge. Last May I sailed for a few days down the coast of Norway with Ragnar Thorseth and a crew of 25 in a fleet of three replica Viking ships bound for America. Thorseth has a penchant for adventure - including rowing across the North Sea alone in a dinghy and circling the globe in a "knarr," or Viking trading ship. He possesses an insatiable curiosity about the seafaring skills of his forebears. Thorseth's latest expedition, dubbed "Vinland Revisited," has traced one possible route of Leif Ericsson. This Norseman reached the New World in about the year 1000 - five centuries before Columbus. Sailing from Norway via Iceland and Greenland, Thorseth braved treacherous ice and North Atlantic winds to arrive at L'Anse-aux-Meadows, Newfoundland - supported by archaeological evidence as the "Vinland" where Ericsson landed. Thorseth admits that Leif Ericsson didn't discover anything - he came to a place inhabited by Indians. The modern sailor launched Vinland Revisited to call attention to the boatbuilding and navigational skills of the Vikings - whose role in history is often limited to their widely publicized raping and pillaging. Thorseth wanted to test the Viking craft and to make people aware that 500 years before Columbus, Scandinavians had developed the technology and the expertise to confront the Atlantic. Thorseth's countryman Thor Heyerdahl has dedicated his life to studying early navigation and its role in prehistoric global migration. According to Heyerdahl's controversial theories, the world was settled from East to West. In order to prove that was possible, he sailed the Sumerian-style raft Tigris from Iraq to northern Africa, crossed the Atlantic on the papyrus Ra I and II, and voyaged from Peru to Polynesia on the balsa raft Kon Tiki. In 1988, while working as a correspondent in Sweden, I spent a long weekend with Heyerdahl as he edited "The Kon-Tiki Man" series at a local film studio. Taking my meals alone with him, a notebook balanced on my lap, I could hardly manage a bite as I devoured his firsthand accounts of exploits I'd read of in books. It was then I learned of his latest quest - which he called "probably ... the greatest and most exciting work I've ever done." Heyerdahl had just moved to Peru to excavate a field of 26 pyramids that had remained untouched for thousands of years. He believes they could conceal the missing link in his migration theories and possibly even shed light on the amazing blossoming of culture in the Old World around 3000 BC. Since my rendezvous with Heyerdahl in Sweden, I have visited his remote dig in northern Peru twice, eager for an update on the latest finds. Together with a team of Peruvian and Scandinavian archaeologists, he is busy compiling data for a scientific volume. After Ragnar Thorseth and his Viking fleet completed their mission to Newfoundland last fall, they sailed down the Eastern seaboard making stops at cities along the way. Their voyage ended in Washington, D.C., on October 9, proclaimed Leif Ericsson Day by Congress in 1964. I went to the capital, had the good fortune to cruise into port with the fleet and met another explorer who played a key role in the Vinland story. Historian Helge Ingstad dazzled me and an auditorium packed with members of the Smithsonian Institution's Resident Associate Program as he recounted his dramatic quest to locate Vinland. In Leif Ericsson's time, the settlement had been abandoned and eventually forgotten. Ingstad described his years of detective-like scholarship and his painstaking physical search of 4,000 miles of North American coastline. Finally, in the 1960s, Ingstad pinpointed remains at L'Anse-aux Meadows on the tip of Newfoundland. Anne Stine Ingstad, his archaeologist wife, excavated Viking artifacts dating to around the year 1000. Their discovery has been internationally recognized. Washington in October was the setting for an extraordinary convergence of explorers, including Heyerdahl, who had come to greet Thorseth's fleet. Heyerdahl was also in town to speak at a round table at the Smithsonian Air and Space Museum titled "From Vinland to Mars - 1,000 Years of Exploration." Michael Collins, the Apollo 11 astronaut, was at the same event. Collins linked the earthbound voyages of discovery with the explorations of space by observing, "They're all journeys of the mind. People have this kind of impatience, this itch - this cosmic itch. People want to know, go and see." That may be so, but few have the courage and conviction to blast into the cosmos or sail across storm-tossed seas in an open boat. Shortly after Ragnar Thorseth completed his five-month, 5,000-mile odyssey, I asked what drives him. "It must be some sort of malfunction," he said with a grin. "A lot of people think I'm crazy. But I like challenges." There's something about a daredevil like Thorseth that brings out the dreamer in us. I have felt the almost tangible longing of the throngs on the docks at Norway and Washington when I climbed into the Norwegian's proud Viking ships. I have witnessed Heyerdahl's appeal and seen how he inspires people - whether they agree with his notions or not. I have watched crowds become electrified by Helge Ingstad and wait in line for hours to shake the hand of Michael Collins - the hand that has reached out to spac e. Every generation has produced people like these - mavericks fueled by a sense of wonder about the mysteries of the world. But the differences between our modern-day discoverers and those of Columbus's time are vast. Today's explorers often have a clear idea of what they might find or at least where to look. They seldom delude themselves by claiming "new" finds, but instead seem to delve into known territory in a more creative, critical, or introspective style than others might. "In a way you can say that everything here on planet Earth is discovered," Thorseth told me, "and that is partly true. Everything is mapped - there have been people all over the place. But it's still possible for me and you to discover a place in our own way .... The world is changing constantly. My kids - if they were to retrace my routes in 10 or 15 years - would find everything different." Having always been restless, I often pondered whether it is human nature to stay home and tend one's garden, or to roam. For Thorseth there is no question. "We are hunters," he said. "I don't think we ever sit down and get satisfied. There will be people looking for new horizons. That is part of our minds. It always has been and always will be. The day that we stop that, we are finished." When it comes to discovery, let's not waste energy arguing over the heroes of the past, but instead put a little more faith in the solution-minded explorers of today. We need their wisdom and their resourcefulness now more than ever.