萬物簡史 第41期:埃文斯牧師的宇宙(10)

About 4.6 billion years ago, a great swirl of gas anddust some 15 billion miles across accumulated inspace where we are now and began to aggregate.Virtually all of it—99.9 percent of the mass of thesolar system—went to make the Sun. Out of thefloating material that was left over, two microscopicgrains floated close enough together to be joined byelectrostatic forces.

大約46億年之前，一股直徑約為240億公里、由氣體和塵埃組成的巨大渦流，積儲在我們現(xiàn)在所在的空間，并開始聚積。實際上，太陽系里的全部物質(zhì)--99.9%的物質(zhì)--都被用來形成了太陽。在剩下的飄浮物質(zhì)當中，兩顆微粒飄到很近的地方，被靜電吸到一起。

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

這是我們的行星孕育的時刻。在整個初生的太陽系里，同樣的情況正在發(fā)生。塵?；ハ嗯鲎?，構(gòu)成越來越大的團塊。最后，這些團塊大到了一定程度，可以被稱做微行星。隨著這些微行星無休止地碰撞，它們或破裂，或分解，或在無休止而又隨意的置換中重新合并，但每次碰撞都有一個贏家，有的贏家越來越大，最后主宰了它們運行的軌道。

It all happened remarkably quickly. To grow from a tiny cluster of grains to a baby planet somehundreds of miles across is thought to have taken only a few tens of thousands of years. In just200 million years, possibly less, the Earth was essentially formed, though still molten andsubject to constant bombardment from all the debris that remained floating about.

這一切都發(fā)生得相當快。據(jù)認為，從小小的一簇塵粒變成一顆直徑為幾百公里的幼星，只要花幾萬年的時間。在不過2億年的時間里，很可能還不到，地球就基本形成了，雖然仍是灼熱的，還經(jīng)常受到仍在到處飄浮的碎片的撞擊。