万物简史 第52期:埃文斯牧师的宇宙(16)

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大约46亿年之前，一股直径约为240亿公里、由气体和尘埃组成的巨大涡流，积储在我们现在所在的空间，并开始聚积。实际上，太阳系里的全部物质--99.9％的物质--都被用来形成了太阳。在剩下的飘浮物质当中，两颗微粒飘到很近的地方，被静电吸到一起。

This was the moment of conception for our planet. All over the inchoate⁴ solar system, the same was happening. Colliding dust grains formed larger and larger clumps⁵. Eventually the clumps grew large enough to be called planetesimals. As these endlessly bumped and collided, they fractured or split or recombined in endless random⁶ permutations, but in every encounter there was a winner, and some of the winners grew big enough to dominate the orbit around which they traveled.

这是我们的行星孕育的时刻。在整个初生的太阳系里，同样的情况正在发生。尘粒互相碰撞，构成越来越大的团块。最后，这些团块大到了一定程度，可以被称做微行星。随着这些微行星无休止地碰撞，它们或破裂，或分解，或在无休止而又随意的置换中重新合并，但每次碰撞都有一个赢家，有的赢家越来越大，最后主宰了它们运行的轨道。

It all happened remarkably⁷ quickly. To grow from a tiny cluster of grains to a baby planet some hundreds of miles across is thought to have taken only a few tens of thousands of years. In just 200 million years, possibly less, the Earth was essentially⁸ formed, though still molten and subject to constant bombardment from all the debris⁹ that remained floating about.

这一切都发生得相当快。据认为，从小小的一簇尘粒变成一颗直径为几百公里的幼星，只要花几万年的时间。在不过2亿年的时间里，很可能还不到，地球就基本形成了，虽然仍是灼热的，还经常受到仍在到处飘浮的碎片的撞击。

 

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