万物简史 第362期:进入对流层(3)

 　　The temperature six miles up can be -70 degrees Fahrenheit¹, and you would need, or at least very much appreciate, supplementary² oxygen. 10公里高空的温度会降至零下57摄氏度，你需要补充氧气，至少很希望这么做。

　　After you have left the troposphere the temperature soon warms up again, 离开对流层以后，由于臭氧层的吸收作用

　　to about 40 degrees Fahrenheit, thanks to the absorptive effects of ozone³ (something else de Bort discovered on his daring 1902 ascent). （这是博尔特在1902年那次勇敢的攀升中的又一发现），温度很快又会上升到大约4摄氏度。

　　It then plunges⁴ to as low as -130 degrees Fahrenheit in the mesosphere 到了中间层，温度又聚降到零下90摄氏度，

　　before skyrocketing to 2,700 degrees Fahrenheit or more in the aptly named but very erratic⁵ thermosphere, 然后到了那个顾名思义的热层又一下子上升到1500摄氏度以上，

　　where temperatures can vary by a thousand degrees from day to night—though it must be said that "temperature" at such a height becomes a somewhat notional concept. 而且热层的日夜温差可达500摄氏度以上——必须指出。在这样高度的温度多少已经成了个理论概念。

　　Temperature is really just a measure of the activity of molecules⁷. 温度其实只是盘度分子活动程度的一个标准。

　　At sea level, air molecules are so thick that one molecule⁶ can move only the tiniest distance, 在海平面高度，空气分子密度很大，一个分子只要运动极小的距离，

　　about three-millionths of an inch, to be precise—before banging into another. 说得确切一点，大约百万分之一厘米一就会砰地撞上另一个分子。

　　Because trillions of molecules are constantly colliding, a lot of heat gets exchanged. 由于几万亿个分子在不停撞击，大量的热量得到交换。

　　But at the height of the thermosphere, at fifty miles or more, 但是，在热层的高度，即在80公里以上的高度，

　　the air is so thin that any two molecules will be miles apart and hardly ever come in contact. 空气那么稀薄，两个分子相隔数公里，几乎没有接触的机会。

　　So although each molecule is very warm, there are few interactions between them and thus little heat transference. 因此，虽然每个分子的动能都很高，但彼此之间几乎没有影响，因此没有多少热量传递。这对卫星和宇宙飞船来说是个好消息。

　　This is good news for satellites and spaceships because if the exchange of heat were more efficient any man-made object orbiting at that level would burst into flame. 这是因为，要是热量交换的频率较高，在那个高度运行的任何人造物体都会熊熊起火。

1 Fahrenheit   

n./adj.华氏温度；华氏温度计(的)

参考例句：

• He was asked for the boiling point of water in Fahrenheit.他被问到水的沸点是华氏多少度。
• The thermometer reads 80 degrees Fahrenheit.寒暑表指出华氏80度。

2 supplementary   

adj.补充的，附加的

参考例句：

• There is a supplementary water supply in case the rain supply fails.万一主水源断了，我们另外有供水的地方。
• A supplementary volume has been published containing the index.附有索引的增补卷已经出版。

3 ozone   

n.臭氧，新鲜空气

参考例句：

• The ozone layer is a protective layer around the planet Earth.臭氧层是地球的保护层。
• The capacity of ozone can adjust according of requirement.臭氧的产量可根据需要或调节。

4 plunges   

n.跳进，投入vt.使投入，使插入，使陷入vi.投入，跳进，陷入v.颠簸( plunge的第三人称单数 )；暴跌；骤降；突降

参考例句：

• Even before he plunges into his program, he has his audience in his pocket. 他的节目甚至还没有出场，就已控制住了观众。 来自《简明英汉词典》
• 'Monseigneur, he precipitated himself over the hill-side, head first, as a person plunges into the river.' “大人，他头冲下跳下山坡去了，像往河里跳一样。” 来自英汉文学 - 双城记

5 erratic   

adj.古怪的，反复无常的，不稳定的

参考例句：

• The old man had always been cranky and erratic.那老头儿性情古怪,反复无常。
• The erratic fluctuation of market prices is in consequence of unstable economy.经济波动致使市场物价忽起忽落。

6 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。

7 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。