When a Polynesian voyaging canoe called the Hokulea embarked on its first trips in Hawaii in the mid-1970s, its crew was trying to prove in part that travel without modern instruments or techniques was possible.
That early crew set out for Tahiti, an island 28 miles wide from more than 2,700 miles away, on a trip that's roughly like leaving Maine and hitting a bull's-eye the size of San Diego, without any roads or landmarks to show the way.
In an era of global positioning satellites, this can seem a relatively mundane feat.
Now, the Hokulea is set to embark on a more challenging voyage: a three-year, 47,000-mile odyssey that will take it to 85 ports in 26 countries. Among its goals is to impart the ancient style of navigation to a new generation of ocean farers.
Here's how they plan to do it:
COMPLEX ART, SIMPLE GOAL
Polynesian-style voyaging is a rugged art — a feat of mental math, applied astronomy, intuition, physical endurance, mental fortitude and keen observation.
"One degree off 2,000 miles away will take you to Antarctica," said Lehua Kamalu, 27, an apprentice navigator who was charmed by the Hokulea when she was a mechanical engineering student at the University of Hawaii.
The complexity also highlights the vastness of the Pacific Ocean, which occupies 46 percent of the world's surface (the contiguous 48 U.S. states would fit inside it 20 times) and the difficulty of hitting a tiny speck in it.
Pulling an island out of the sea, as navigators say, requires, among other things, a navigator to be alert 20 hours a day, with 20-minute sips of sleep as her only respite.
The rotation of the earth guides the sun and stars across the sky in a predictable east-to-west fashion. The prevailing wind and waves also scoot in from the east.
Navigators, therefore, can tell direction and latitude from star positions and the feel of the waves.
Longitude is trickier. To tell how far north and south they are, navigators must rely on dead reckoning — figuring speed, and multiplying that by days and hours on the open water.
On the Hokulea, apprentice navigators track bubbles on the water's surface. Watch a bubble at the front of the boat, count the seconds before the boat passes it, and divide that number into 25 to get the boat's speed in knots.
The best navigators run these figures constantly, balancing their decisions against their own calculations and the best estimations of their crew. "You've got to stick it all in your head and hope it stays there," Kamalu said.
Maintaining heading is vital, and can be tricky through storms, under clouds and during the midday hours, when the sun sits centrally in the sky and points to nowhere. The heavens are helpful only about one-fifth of the time.
ARRIVING AT LAND
Floating plants or other debris on the surface will whisper when land is near. But it's only an approximation, without direction.
Sea birds will point the way there. In the Pacific, the Grey Noddy tern, which fishes during the day and heads home to its nest at night, will lead a crew toward land.
"You make a thousand observations of nature a day and you make two decisions a day," said Jenna Ishii, 29, an apprentice navigator. "Even the masters, they don't ever call themselves 'master navigators.' They continually call themselves students."
Sam Eifling can be reached on Twitter at http://twitter.com/sameifling
Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.