One problem with the collision hypothesis is the question of how a satellite formed in this way could have settled into the nearly circular orbit that the Moon has today.

碰撞假说的一个问题是，以这种方式形成的卫星是如何在月球现在的近乎圆形的轨道上运行的。

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A lot of people think of earth's orbit around the sun as being perfectly circular, as smooth and as regular as, say, the way that hands move on a well-made watch, but it just doesn't work that way.

很多人认为地球绕太阳的轨道是完美的圆形，就像手在一块制作精良的手表上移动那样平滑、有规则，但事实并非如此。

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There might be a distant object in a more stable, more circular orbit that has gone unnoticed so far.

也许有这么一个遥远的天体具有一个更加稳定的更加圆润的轨道而至今未被我们发现。

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You've got negative charge in motion, and it's in a circular orbit.

负电荷在运动，它们处在一个环形的轨道中。

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Let's imagine it's a circular orbit.

想象一下,有个圆轨道

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The intervening weeks will be spent in a manoeuvre called aerobraking, which involves using the air-resistance of the thin Martian atmosphere to change the elliptical initial orbit into a circular one from which the planet's surface can be examined in detail.

ECONOMIST: Mars Odyssey