Pacific: The Ocean of the Future. Simon Winchester

       Here from this mountain shore, headland beyond stormy headland plunging like dolphins through the blue sea-smoke

       Into pale sea—look west at the hill of water: it is half the planet . . .

       arched over to Asia, Australia and white Antarctica: those are the eyelids that never close; this is the staring unsleeping

       Eye of the earth; and what it watches is not our wars.

      —ROBINSON JEFFERS, FROM “THE EYE,” 1965

      United Airlines Flight 154 leaves Honolulu International Airport just after dawn three times a week, bound ultimately for the city of Hagåtña, the capital of the island republic of Guam. If the northeast trades are blowing at their usual steady twelve knots, the jet will take off to the east, into the low morning sun over Waikiki, and those passengers on the aircraft’s left side will see the wall of skyscraper hotels along the beachfront and be able to glimpse down at Doris Duke’s great seaside mansion, Shangri-La. Once the plane is two miles high above the crater of the dormant Diamond Head volcano, it will begin to make a long and lazy turn to the right.

      If the morning haze is light, passengers on the right side now can sometimes glimpse the bombers and heavy transport planes lined up on the flight line of Hickam Field, and maybe a flotilla of sleek gray warships will be gliding slowly through the lochs of Pearl Harbor. There will be some suburbs clustered between the shore and the slopes; there will be a skein of rush-hour traffic crawling along on H-1, the main thruway into Honolulu; and behind these urban images will rise ranges of mountains, razor-sharp aiguilles dotted in places with white radar domes.

      With every one of its seats invariably filled, the plane will then clear its throat and tilt its nose ever higher, and once at five miles high, it will set its autopilot to a southwesterly course, heading out initially over two thousand miles of clear blue, unpeopled ocean. As the climb flattens out, and the aircraft passes through a final stratum of small puffballs of cloud, in a blink the island behind fades, is suddenly gone from view, and all below is just sea, endless empty sea, with many hours of emptiness ahead.

      The ocean beneath is almost unimaginably vast, and illimitably various. It is the oldest of the world’s seas, the relic of the once all-encompassing Panthalassic Ocean that opened up seven hundred fifty million years ago. It is by far the world’s biggest body of water—all the continents could be contained within its borders, and there would be ample room to spare. It is the most biologically diverse, the most seismically active; it sports the planet’s greatest mountains and deepest trenches; its chemistry influences the world; and the planetary weather systems are born within its boundaries.

      Most see this great body of sea only in parts—a beach here, an atoll there, a long expanse of deep water in between. Just a few, mariners mostly, have the good fortune to confront the ocean in its entirety—and by doing so, to win some understanding of the immense spectrum of happenings and behaviors and people and geographies and biologies that are to be found within and on the fringes of its sixty-four million square miles. For those who do, the experience can be profoundly humbling.

      Captain Cook wrote that by exploring the Pacific he had gone “as far as I think it is possible for man to go.” To traverse it today, two and a half centuries later—to set a course from Kamchatka