现在，牛顿理论认为，有一些彗星沿双曲线或抛物线运行，永远不再返回；另外一些彗星沿普通的椭圆轨道运行。

Now according to Newtonian theory, some of them moved in hyperbolas or parabolas never to return; others moved in ordinary ellipses.

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现在，牛顿理论认为，有一些彗星沿双曲线或抛物线运行，永远不再返回；另外一些彗星沿普通的椭圆轨道运行。

Now according to Newtonian theory, some of them moved in hyperbolas or parabolas never to return; others moved in ordinary ellipses.

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