万物简史 第375期:进入对流层(16)

 　　Any water molecule¹ that strays beyond the edge of the cloud is immediately zapped by the dry air beyond, allowing the cloud to keep its fine edge. 要是水分子越出该云边缘，外面干燥的空气马上会把它除掉，从而使积云的边缘保持光清。

　　Much higher cirrus clouds are composed of ice, and the zone between the edge of the cloud and the air beyond is not so clearly delineated, 而高得多的卷云由冰和该云的边缘与外面的空气之间的区域组成，

　　which is why they tend to be blurry² at the edges. 故而它的边缘往往是模模糊糊的）

　　For all the heft and fury of the occasional anvil-headed storm cloud, the average cloud is actually a benign³ and surprisingly insubstantial thing. 偶尔出现的砧头状雷雨云尽管气势汹汹，实际上在一般情况下都是温和而不实的东西。

　　A fluffy⁴ summer cumulus several hundred yards to a side may contain no more than twenty-five or thirty gallons of water— "about enough to fill a bathtub," as James Trefil has noted⁵. 夏天一朵绒毛状的积云，虽然每一边都伸展数百米，所含的水分却不足100-150升——“大约够注满一个浴缸”，正如詹姆斯·特雷菲尔说的。

　　You can get some sense of the immaterial quality of clouds by strolling through fog—which is, after all, nothing more than a cloud that lacks the will to fly. 要是你想知道云是一种华而不实的东西，你可以在雾里走一走——雾只不过是一种没有决心远走高飞的云。

　　To quote Trefil again: "If you walk 100 yards through a typical fog, you will come into contact with only about half a cubic inch of water—not enough to give you a decent drink." 我们再引特雷菲尔的话： “要是你在普通的雾里走91米，你只会接触到大约8立方厘米的水——还不够你好好喝一口。”

　　In consequence, clouds are not great reservoirs of water. 因此，云不是大水库。

　　Only about 0.035 percent of the Earth's fresh water is floating around above us at any moment. 在任何时候，地球上只有大约0.035%的淡水飘浮在我们的头顶。

　　Depending on where it falls, the prognosis for a water molecule varies widely. 水分子的结局差别很大，取决于它落在哪里。

　　If it lands in fertile soil it will be soaked up by plants or reevaporated directly within hours or days. 要是它落在肥沃的土壤里，它会被植物吸收，或在数小时或数天内再次直接蒸发。

　　If it finds its way down to the groundwater, however, it may not see sunlight again for many years—thousands if it gets really deep. 然而要是进人了地下水，它也许在好多年里——好几千年里，如果它流到确实很深的地方的话——再也见不着太阳。

1 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

2 blurry   

adj.模糊的；污脏的，污斑的

参考例句：

• My blurry vision makes it hard to drive. 我的视力有点模糊，使得开起车来相当吃力。 来自《简明英汉词典》
• The lines are pretty blurry at this point. 界线在这个时候是很模糊的。 来自《简明英汉词典》

3 benign   

adj.善良的，慈祥的；良性的，无危险的

参考例句：

• The benign weather brought North America a bumper crop.温和的气候给北美带来大丰收。
• Martha is a benign old lady.玛莎是个仁慈的老妇人。

4 fluffy   

adj.有绒毛的，空洞的

参考例句：

• Newly hatched chicks are like fluffy balls.刚孵出的小鸡像绒毛球。
• The steamed bread is very fluffy.馒头很暄。

5 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。