Passage II

Polaris: Not Always the North Star

Polaris, the star now almost directly over the North Pole, has played a significant role in many mythologies and in the history of navigation. For centuries, sailors and leaders of desert caravans used the North Star to chart their courses. Polaris has been called the Lodestar, the Steering Star, and Stella Maris (the Star of the Sea). (17) Finally, people in ancient India believed it was the Golden Peg that held the universe together. In Scandinavian mythology, Polaris was thought to be the jeweled head of the World Spike—an enormous nail the Norse gods had hammered into the sky so the stars could revolve around it. (19)

[1] However, as the Greek astronomer Hipparchus discovered around 129 BC, the North Star, or polestar, is not eternally fixed over the North Pole, as the mythmakers had supposed. [2] In the process of compiling an astronomical catalog, Hipparchus noticed that the stars had seemingly shifted from positions noted in Babylonian records from many centuries earlier. [3] He concluded that it was not the stars that were moving but rather the position from which they were being observed that varied. [4] Precession, in turn, is caused by the gravitational pull of the Sun and the Moon on the bulge at Earth’s equator. [5] A wobbling in Earth’s axis of rotation, called precession, cause this variation in position. (23)

As Earth rotates round and round and round like a spinning top, its axis traces a huge circle that takes 26,000 years to complete. As a result, the North Pole’s position in relation to the stars change. Astronomers now, know, that, around 3000 BC, Thuban, a star in the tail of the constellation Draco (the Dragon), was directly above the pole. Three thousand years from now, Alderamin, in the constellation Cepheus, is the polestar. Over the 26,000-year cycle, numerous stars will take its’ turn as the North Star for a few thousand years each. But the Babylonian records should not be discarded.(30)