我们取一大块物质，称它为一千克。

We will take a chunk of some material and we will call it a kilogram.

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最糟糕的轰炸——包括将大块物质撞击得脱离地球形成月球巨大碰撞——已经结束了。

The worst of the bombardment—including the colossal impact that knocked loose the chunk that became our moon—was over.

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此外，撞击留下的大块物质会在主火山口周围形成二级火山口。

Also, large blocks thrown aside by the impact would form secondary craters surrounding the main crater.

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