英语听力文摘 English Digest 706 地球的引力改变过么？

Has Earth’s Gravitational Pull Been Changing?

Don, why are you slouching? Don’t you know it’s bad for you?

Did you know that about 200 tons of debris¹ strike the Earth every day? So I was thinking! Although most of this stuff burns up in the atmosphere, the resulting dust still settles and adds to the Earth’s mass. That’s about half a million tons per year!

All right, but what does all this have to do with your posture²?

Sit Up Straight

So if the earth keeps accumulating mass, doesn’t that mean that the Earth’s gravitational pull has been increasing? After all, gravity is directly proportional to mass.

Are you saying you can’t sit up straight because gravity is stronger now than it used to be?

Admit it, Ya?l–it’s a good one.

Earth’s Mass

Earth’s mass in metric tons is approximately six followed by twenty-one zeroes. So assuming that your estimate is correct, and the Earth accumulates a half a million tons of debris every year, this means that in the sixty million years since dinosaurs³ existed the Earth would have accumulated approximately thirty trillion tons of meteoric⁴ debris. That’s thirteen zeroes.

The point is that a number with thirteen zeroes is minuscule⁵ relative to a number with twenty-four zeroes. While thirty trillion tons sounds impressive, it is nothing compared to the Earth’s total mass. So it’ s definitely not all that extra gravity that’s making you slouch

1 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

2 posture   

n.姿势，姿态，心态，态度；v.作出某种姿势

参考例句：

• The government adopted an uncompromising posture on the issue of independence.政府在独立这一问题上采取了毫不妥协的态度。
• He tore off his coat and assumed a fighting posture.他脱掉上衣，摆出一副打架的架势。

3 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

4 meteoric   

adj.流星的，转瞬即逝的，突然的

参考例句：

• In my mind,losing weight is just something meteoric.在我眼中，减肥不过是昙花一现的事情。
• His early career had been meteoric.他的早期生涯平步青云。

5 minuscule   

adj.非常小的；极不重要的

参考例句：

• The human race only a minuscule portion of the earth's history.人类只有占有极小部分地球历史。
• As things stand,Hong Kong's renminbi banking system is minuscule.就目前的情况而言，香港的人民币银行体系可谓微不足道。