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What major astronomical phenomenon did Hipparchus of Rhodes discover around 130 BC?
Comparing his own star positions with Alexandrian measurements 150 years older, Hipparchus found that the celestial coordinate system was drifting westward at approximately one degree per century. Precession is the slow gyroscopic wobble of Earth's axis; the full cycle takes ~26,000 years. He was the first observer to detect any systematic motion of the entire celestial sphere.
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The Greek Who Counted the Stars and Found the New One Hipparchus of Rhodes catalogued a thousand stars, invented trigonometry, discovered the precession of the equinoxes, and may have built the original of the Antikythera mechanism. Almost none of his writing survives.
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- Around 130 BC, Hipparchus of Rhodes produced the first comprehensive Greek catalogue of stellar positions. Roughly how many stars did he catalogue?
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