万物简史 第222期:把铅撵出去(11)

 　　For seven years, first at the University of Chicago and then at the California Institute of Technology (where he moved in 1952), he worked in a sterile¹ lab, making very precise measurements of the lead/uranium ratios in carefully selected samples of old rock.

　　有7年时间，先是在芝加哥大学，后在加州理工学院（他于1952年迁往那里），他在无菌实验室里埋头苦干，仔细选择古老岩石的样品，精密测定里面铅/铀的比例。

　　The problem with measuring the age of the Earth was that you needed rocks that were extremely ancient, containing lead- and uranium-bearing crystals that were about as old as the planet itself—anything much younger would obviously give you misleadingly youthful dates—but really ancient rocks are only rarely found on Earth. In the late 1940s no one altogether understood why this should be. Indeed, and rather extraordinarily², we would be well into the space age before anyone could plausibly³ account for where all the Earth's old rocks went. (The answer was plate tectonics, which we shall of course get to.) Patterson, meantime, was left to try to make sense of things with very limited materials. Eventually, and ingeniously, it occurred to him that he could circumvent⁴ the rock shortage by using rocks from beyond Earth. He turned to meteorites⁵.

　　测定地球年龄的问题在于，你需要有极其古老的岩石，内有含铅和铀的晶体，其古老程度几乎与这颗行星一样──要是岩石年轻得多，测出的年代显然会比较年轻，从而得出错误的结论，而真正古老的岩石在地球上是很难找得着的。到20世纪40年代末，谁也不知道这是什么原因。实际上，要等到太空时代，才可能有人貌似有理地说明地球上古老岩石的去向，这真是不可思议的。（答案在于板块构造，我们当然将谈到这个问题。）与此同时，彼得森只能在材料非常有限的情况下把这一切搞清楚。最后，他突然聪明地想到，他可以利用地球之外的岩石，从而绕开缺少岩石的问题。他把注意力转向陨石。

　　地球爷爷

　　The assumption he made—rather a large one, but correct as it turned out—was that many meteorites are essentially⁶ leftover⁷ building materials from the early days of the solar system, and thus have managed to preserve a more or less pristine⁸ interior chemistry. Measure the age of these wandering rocks and you would have the age also (near enough) of the Earth.

　　他提出了一个假设──一个很有远见的假设，结果证明非常正确，即，许多陨石实际上是太阳系早期留下来的建筑材料，因此多少保留着原始的内部化学结构。测定了这些四处游荡的岩石的年代，你也就（接近于）测定了地球的年龄。

1 sterile   

adj.不毛的，不孕的，无菌的，枯燥的，贫瘠的

参考例句：

• This top fits over the bottle and keeps the teat sterile.这个盖子严实地盖在奶瓶上，保持奶嘴无菌。
• The farmers turned the sterile land into high fields.农民们把不毛之地变成了高产田。

2 extraordinarily   

adv.格外地；极端地

参考例句：

• She is an extraordinarily beautiful girl.她是个美丽非凡的姑娘。
• The sea was extraordinarily calm that morning.那天清晨，大海出奇地宁静。

3 plausibly   

似真地

参考例句：

• The case was presented very plausibly. 案情的申述似很可信。
• He argued very plausibly for its acceptance. 他为使之认可辩解得头头是道。

4 circumvent   

vt.环绕，包围；对…用计取胜，智胜

参考例句：

• Military planners tried to circumvent the treaty.军事策略家们企图绕开这一条约。
• Any action I took to circumvent his scheme was justified.我为斗赢他的如意算盘而采取的任何行动都是正当的。

5 meteorites   

n.陨星( meteorite的名词复数 )

参考例句：

• Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
• One theory about the existence of extraterrestrial life rests on the presence of carbon compounds in meteorites. 地球外存在生命的理论是基于陨星上存在碳化合物质这一事实的。 来自《简明英汉词典》

6 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。

7 leftover   

n.剩货，残留物，剩饭；adj.残余的

参考例句：

• These narrow roads are a leftover from the days of horse-drawn carriages.这些小道是从马车时代沿用下来的。
• Wonder if that bakery lets us take leftover home.不知道那家糕饼店会不会让我们把卖剩的带回家。

8 pristine   

adj.原来的，古时的，原始的，纯净的，无垢的

参考例句：

• He wiped his fingers on his pristine handkerchief.他用他那块洁净的手帕擦手指。
• He wasn't about to blemish that pristine record.他本不想去玷污那清白的过去。