Comets, Predicting - Research Article from Macmillan Science Library: Mathematics

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What Are Comets?

Aristotle thought that comets were atmospheric phenomena, since they changed appearance. Aristotle's cosmology divided the universe into various spheres. The spheres below the Moon (Aristotle's sublunary spheres) were the only spheres that could change. The unchangeable heavens included the Moon and everything beyond. However, Tycho Brahe demonstrated that comets must be farther from Earth than the Moon. If the Moon is observed from different places on Earth, its position in the sky will change slightly due to parallax. By measuring the angular change in the position of the Moon and knowing the distance between the observing locations on Earth, the distance to the Moon can be measured. The distance between the observing positions is the base of an isosceles triangle with the vertex on the Moon. The appearance of the Great Comet of 1577 (which is now known as Halley's comet) gave astronomers the opportunity to...

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This section contains 1,770 words
(approx. 6 pages at 300 words per page)
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Macmillan Science Library: Mathematics
Comets, Predicting from Macmillan Science Library: Mathematics. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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