Scholars continue to debate whether this discovery was independent, or whether the new technology was spread westward from China through trade or other contact between civilizations. Some speculate that the Chinese may have used lodestones for navigation in voyages to the east coast of India in about 100 B.C. Chinese references to a "south pointer" are found in texts as early as the first century A.D. The south pointer was a spoon carved from lodestone, which was allowed to rotate on a smooth brass plate until its handle pointed south.
Magnets align themselves along the north-south axis because the Earth itself is a huge magnet. The poles of the Earth's magnetic field roughly correspond to the rotational axis of the globe. This means that the north magnetic pole is in the approximate direction of the north geographic pole, or true north. A light magnet that can move freely will align itself in the north-south direction. However, a heavy bar magnet lying on a tabletop will not move because gravity and friction counteract the magnetic force.
Before the magnetic compass, sailors navigated by the position of the stars. They knew, for example, that the North Star, Polaris, remained in a fixed northerly position in the sky while the other stars seemed to move around it.
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