The aurora display was not caused by the continuing magnetic blasts from Planet X, as auroras are caused by fluctuations in Earth gravity field.

极光的出现并不是来自于X星的持续的磁场轰炸引起的，因为极光是由地球重力场的波动引起的。

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Arrows would continue to fly forward forever in a straight line were it not for gravity, which brings them down to earth.

要不是重力使箭掉落地上，它将会一直沿直线往前飞行。

《柯林斯英汉双解大词典》

Otherwise gravity will pull you back down to the Earth.

否则，地心引力会把你拉回地球。

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Newton proved his idea by measuring how much gravity force would be needed to keep the moon orbiting the Earth.

VOA: special.2011.06.01

But gravity has a remarkable property that the pull of the Earth is itself proportional to the inertia of the object.

重力有一个显著特征,即地球的引力,与物体的质量成比例

耶鲁公开课 - 基础物理课程节选

The poet, after all, is subject to gravity in Frost, to the force of the earth.

这个诗人，弗罗斯特，终究还是受制于地心引力，受制于地球的力量。

耶鲁公开课 - 现代诗歌课程节选

Even here on Earth, gravity has a greater pull in some spots than in others.

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The returning Alpha crewmembers, meanwhile, are doubling up on exercise sessions to prepare for their return to Earth's gravity.

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Lifting heavy spacecraft and fuel out of the Earth's gravity is expensive.

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