It was pioneer science fiction writer Jules Verne who forecast it. In the century since, humankind has been both circumnavigating the globe and its segments, and cutting straight to the heart of things.
Verne's journeys were fanciful: ''Around the World in 80 Days'' (1873), by balloon. And ''Journey to the Center of the Earth'' (1864). But they touched the common lodestone of imagination and determination that has inspired less fanciful trips, from Ferdinand Magellan on.
In 1519 Magellan became the first person to circumnavigate the world, but it had taken him two half trips to do it. Nowadays the accouterments are more modern than Magellan's leaky boats, with their primitive wooden pumps. But the challenges are equally rugged for today's explorers, all of whom are ultimately testing themselves en route to the exultation of victory.
They're people like Stacy Chanin, who this week became the first person to swim three times around Manhattan Island. She completed the 84 miles in 33 1/2 hours.
And Gary Aramini, who this week finished a straighter-if-longer trip, San Francisco to New Hampshire. His run took four months. The first transcontinental trip by solar car, just ended, was faster: 45 days.
For two months this summer Norwegian explorer Ragnar Thorseth and his crew retraced the Viking route from Scandinavia to Newfoundland. It was the first time in a thousand years anyone had sailed that route in a knarr - the oceangoing boat the Vikings used.
Last year France's Philippe Jeantot won the first round-the-world solo sailing race in 159 days, a time Magellan would have found incomprehensible.
So-called barriers of physical handicap and age are being surmounted. Two years ago three paraplegics made their way to the top of a mountain 8,750 feet high in Texas.Three years before, a 12-year-old British boy had become the youngest person to swim the English Channel.
People the world over are becoming increasingly expert at the skills these explorations require - hiking, swimming, and even ballooning. This weekend in St. Niklaas, Belgium, they're holding the 37th annual test of balloonists' precision flying skills.
Even the imaginative Jules Verne would have found it difficult to foresee that.