天体物理学家约翰·马特斯和丹尼尔·惠特米尔分析了太阳系内部的彗星运转，发现许多彗星的运行轨道都非常奇特。
Astrophysicists John Matese and Daniel Whitmire analyzed comets passing through the inner solar system, discovering many of them had strange orbits.
很久以前人们就注意到这些天体在空中按一定的轨道运转着，一种叫引力的力使它们保持在它们的轨道上。
People noticed long ago that these travelling bodies moved around in the sky in definite paths. It is a force called gravity that holds them in their paths.
很久以前人们就注意到这些天体在空中按一定的轨道运转着，一种叫引力的力使它们保持在它们的轨道上。
People noticed long ago that these travelling bodies moved around in the sky in definite paths. It is a force called gravity that holds them in their paths.
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