英语听力：探索发现 科学新发现：我们的大气层-18

The air thins and they begin to lose the protective weight of the miles of air above them.

The pressure is dropping, when you finally get to the stratosphere, and to the altitude we like to work at, it's only one one hundredth that of it's on the ground, it's a whole different world than down here.

The weight of the miles of air above us creates air pressure, we often think of air as weightless, but all those gas molecules¹ add up, grand central station's main concourse contains over 200 tons of air, as gravity pulls the air down, it compresses the layers below, making them denser³, this dense² air is what we are used to dealing⁴ with on the ground, just a pint⁵ of it contains more than 8.5 billion trillion gas molecules, but higher up around the balloon, there was less atmosphere pressing down from above, the air up here is thinner.

It's like being under a thousand blankets, and each blanket is a layer of atmosphere, and we are being pushed under all of these blankets, as you go higher, you go up through the blankets, so it's pushing on you less, until you are at the top above most of the blankets where you don't feel it at all.

That thin air seems alien to us because our bodies and technology are so perfectly⁶ adapted to thicker air, we even need it to hear, the gas carries sound through air as pulsing waves of pressure.

Sound is just a wave like a water wave in a pond, but if you take away the water, there is nothing for the wave to go across, and as the atmosphere gets thinner and thinner, it supports that wave less and less.

1 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。

2 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

3 denser   

adj. 不易看透的, 密集的, 浓厚的, 愚钝的

参考例句：

• The denser population necessitates closer consolidation both for internal and external action. 住得日益稠密的居民，对内和对外都不得不更紧密地团结起来。 来自英汉非文学 - 家庭、私有制和国家的起源
• As Tito entered the neighbourhood of San Martino, he found the throng rather denser. 蒂托走近圣马丁教堂附近一带时，发现人群相当密集。

4 dealing   

n.经商方法，待人态度

参考例句：

• This store has an excellent reputation for fair dealing.该商店因买卖公道而享有极高的声誉。
• His fair dealing earned our confidence.他的诚实的行为获得我们的信任。

5 pint   

n.品脱

参考例句：

• I'll have a pint of beer and a packet of crisps, please.我要一品脱啤酒和一袋炸马铃薯片。
• In the old days you could get a pint of beer for a shilling.从前，花一先令就可以买到一品脱啤酒。

6 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。