Olbers, Heinrich Wilhelm Matthäus [key], 1758–1840, German astronomer and physician. He originated (1797) the first satisfactory method for calculating the orbits of comets, but despite the fame it brought him, he remained an amateur astronomer and became a physician. However, he continued his research on comets and discovered several. He was the first to detect the comet of 1815 (Comet Olbers, period 72.7 years). He also discovered two asteroids, Pallas (1802) and Vesta (1807). Considering their orbits and those of the other asteroids then known, Olbers concluded that they are fragments of a disrupted planet that had formerly revolved around the sun.
He is best remembered for Olbers' paradox: “Why is the sky dark at night?” Assuming that space is infinite and filled with stars, he suggested, the entire sky should be as bright as the surface of the sun. The question had originally been raised by Kepler. Others offered one of several incorrect resolutions to the paradox, suggesting that absorbing clouds obscured our view of the distant stars. The correct explanation is that our universe is finite both in time and place, and the total amount of matter and energy is far too small to light up the night sky.
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