【英语时差8,16】重空气

Heavy air on this Moment of Science.

 

Here's an oxiny question: does air weigh anything?

 

At first it might seem preplexing, on the one hand, air just seems floating, I mean, to say something is as light as air is to say its weighlessness, is isn't? 

 

But then, a strong wind can pull floations down and set things fly. So air isn't exactly nothing. Air doesn't affect to have a weight and here's a simple way you can prove it.

 

You'll need two identical balloons, a string and a doul. Test the uninfeded balloons to either end of the doul, test the string to the center of the doul and then hanging it from something. If the baloons are very nearly identical, the doul should hang evenly without tipping to either side. You now have a basic scale. Next, inflate¹ one of the balloons by blowing into it, what happens? You bet, the side with inflated² balloon hangs lower than the other side. You have demonstrated that air has a weight.

 

The simply demonstration³ sometimes confuses people. Why does a balloon filled with air fall? When it's only surrounded by air, why doesn't it just remain where it is? The answer lies in density⁴. Any fluit anything that has a greater of density than its surroundings will sink. When you blow the baloon, you are increasing its overall density by forcing air inside it. That's because the air inside the baloon is under greater of pressure than the air outside. It's being squeezing entirely⁵ by the sides of the balloon. Greater pressure it's greater of density so the heavy air inside the balloon will fall.

1 inflate   

vt.使膨胀，使骄傲，抬高（物价）

参考例句：

• The buyers bid against each other and often inflate the prices they pay.买主们竞相投标，往往人为地提高价钱。
• Stuart jumped into the sea and inflated the liferaft.斯图尔特跳到海里给救生艇充气。

2 inflated   

adj.（价格）飞涨的；（通货）膨胀的；言过其实的；充了气的v.使充气（于轮胎、气球等）( inflate的过去式和过去分词 )；（使）膨胀；（使）通货膨胀；物价上涨

参考例句：

• He has an inflated sense of his own importance. 他自视过高。
• They all seem to take an inflated view of their collective identity. 他们对自己的集体身份似乎都持有一种夸大的看法。 来自《简明英汉词典》

3 demonstration   

n.表明，示范，论证，示威

参考例句：

• His new book is a demonstration of his patriotism.他写的新书是他的爱国精神的证明。
• He gave a demonstration of the new technique then and there.他当场表演了这种新的操作方法。

4 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

5 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。