In the Arctic summer, the sun shines even at midnight. So it was bright as the airship Italia approached the geographic North Pole, motoring at 3,000 feet above the endless pack ice. Below the ship, a thick bank of fog obscured the frozen Arctic Ocean, but up here the sky was blue, cloudless. A pair of officers used a sextant and the sun to measure the Italia’s position as they covered the final miles, and when they’d reached 90 degrees north, where the planet’s longitude lines converge at the pole, the helmsman began a slow, lazy circle around their goal. General Umberto Nobile, the airship’s commander, gave the order to dive under the fog, and soon the airmen could see the blank ice, fewer than 500 feet below them. They had made it.