If the sky overhead is clear, you can determine the direction of the sun by determining the direction of polarization of the sky directly overhead. If the sun is just below the horizon in the west, for instance, the sky overhead will be polarized along the north-south direction. Light scattered by air molecules is polarized, and the direction of the polarization is at right angles to a line to the sun. The solution to your problem is the sky compass - the functional equivalent of the Viking sunstone.īoth the sky compass and the sunstone work by determining the direction of polarization of the sky overhead. In fact, the problem has become worse, both because you are now traveling over the pole, where twilight can last for a week or more, and because the airplane is moving so fast that even an hour or two of flight without directional control can bring disaster. Celestial navigation when the sun is just below the horizon is still impossible. The magnetic compass is no longer a vague rumor, but its problems at high latitudes are real, although not caused by ice. Nine centuries of technological development have done little to assist in the solution of your Viking ancestors' problem. Now you are a navigator for Scandinavian Airlines, pioneering commercial flight across the North Pole. Jump forward in time, to the middle of the twentieth century. If only yours had not been stolen when you stopped for supplies in Iceland! You've heard vague rumors of a strange black rock that points to the north, but you've also heard that ice somehow disturbs its workings. Even in the daytime, the sun is often hidden by fog. It's getting late in the sailing season, and during the long polar twilight, with neither sun nor stars visible, directions are impossible to determine. You are sailing westward to Greenland - you hope.

The noun project compass