【英语时差8,16】关于飞机凝结尾流（上）

 Have you ever seen a perfectly¹ cloudless sky? Cloudless–that is–except for two or three long white lines smeared² across the perfect blue sky by airplanes like smudges on a pane³ of glass. Why do airplanes sometimes leave contrails behind? Actually, contrails, short for condensation⁴ trails, are essentially⁵ clouds. They are no different from the cirrus clouds that naturally form in that region of the atmosphere. High in the atmosphere, water can exist in one of two basic forms. It can either be invisible water vapor–a gas–or it can condense around microscopic⁶ dust particles into tiny droplets⁷ or ice crystals. Every cloud you see is made of tiny droplets or crystals like this, and so is a contrail.

1 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

2 smeared   

弄脏； 玷污； 涂抹； 擦上

参考例句：

• The children had smeared mud on the walls. 那几个孩子往墙上抹了泥巴。
• A few words were smeared. 有写字被涂模糊了。

3 pane   

n.窗格玻璃，长方块

参考例句：

• He broke this pane of glass.他打破了这块窗玻璃。
• Their breath bloomed the frosty pane.他们呼出的水气，在冰冷的窗玻璃上形成一层雾。

4 condensation   

n.压缩，浓缩；凝结的水珠

参考例句：

• A cloud is a condensation of water vapour in the atmosphere.云是由大气中的水蒸气凝结成的。
• He used his sleeve to wipe the condensation off the glass.他用袖子擦掉玻璃上凝结的水珠。

5 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。

6 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
• A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。

7 droplets   

n.小滴( droplet的名词复数 )

参考例句：

• Droplets of sweat were welling up on his forehead. 他额头上冒出了滴滴汗珠。 来自辞典例句
• In constrast, exhaled smoke contains relatively large water droplets and appears white. 相反，从人嘴里呼出的烟则包含相当大的水滴，所以呈白色。 来自辞典例句