VOA慢速英语2014 如何找到陨石?

 

How Does One Find a Meteorite¹? 如何找到陨石?

Editor's Note: The annual Perseid meteor shower will peak in the skies over Earth on the night of Aug. 12-13. Despite a bright moon supermoon, there should still be a good show from this prolific² shower.

Much of the world can see Perseids any time after full dark, with peak viewing projected early on the morning of Aug. 13, between 3:00 to 4:00 a.m., your local time. Addtional information can be found from the NASA website.

And now, for a story on meteorite from George Putic and Anna Mateo.

Space rocks often enter the Earth’s atmosphere.  But they usually explode and burn before falling to the ground.  About 70 percent of our planet is covered with water.  As a result, most meteorites³ falling from the sky disappear on the oceans’ floor.  We would not know about them if it was not for an international agency.

You may remember the meteorite that exploded last year 23 kilometers above Chelyabinsk, in Russia.  Scientists estimate it was about 18 meters long before it fell to Earth.  They also think it had a mass of about 10,000 tons.  

Many people would have died if the meteorite fell in a populated area.  Luckily, it did not.  Instead it broke apart mid-air and most of the pieces fell into Lake Chebarkul.  But that is a little too close for some people.

The Comprehensive Nuclear-Test-Ban Treaty Preparatory Commission is a group based in Vienna, Austria.  It says the Earth is visited by meteorites more often than we know.   

The group records explosions made by meteorites that enter Earth’s atmosphere.  Pierrick Mialle works for the commission, also known as the CTBTO.  He is an acoustics⁴ expert, specializing in the study of sounds. 

He says since meteorites are sometimes entering the atmosphere, they are creating loud air bursts.

The commission controls sensors⁵ and other equipment that watch for possible violations⁶ of the Nuclear Test ban treaty.  Some of the devices are seismic⁷, meaning they measure the movement of the Earth.  Others are hydrostatic, meaning they measure the movement of the Earth’s water.  The Commission also uses ultrasound and radioactivity sensors. 

Between 2000 and 2013, the CTBTO recorded 26 powerful explosions of large meteorites entering the atmosphere. 

The B612 Foundation also studies meteorite impacts.  This group estimates at least four of those 26 explosions were stronger than the nuclear bomb that destroyed Hiroshima.

In addition to loud noise, explosions create low frequency infrasound.  Sound waves can travel very long distances at such low frequencies.  But human beings are unable to hear them.

CTBTO stations as far away as the Antarctica recorded the explosion of the Chelyabinsk meteorite.

Mr. Mialle says listening stations operate anywhere from four to 15 high-technology sensors.  He says that the sensors work like large microphones. 

“They are called micro barometer⁸ because they measure micro fluctuations⁹ of the atmosphere.  It’s like a large microphone except there’s no membrane¹⁰.”

He adds that some of the explosions are hard to identify immediately after they are recorded.

“For instance, the first time we had this, what was later called the Super Bolide of North Pacific, in the first few weeks all that was known was a large event in the middle of the Pacific.  But we didn’t know what it was.”

The commission keeps contact with other agencies, such as the American space agency, that follow meteorites.  Space agency officials later confirmed that the mysterious explosion was caused by a meteorite.

When complete, the CTBTO system will have 337 stations worldwide.  And these stations will be listening for nuclear explosions and other loud sounds in the atmosphere.

1 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

2 prolific   

adj.丰富的，大量的；多产的，富有创造力的

参考例句：

• She is a prolific writer of novels and short stories.她是一位多产的作家，写了很多小说和短篇故事。
• The last few pages of the document are prolific of mistakes.这个文件的最后几页错误很多。

3 meteorites   

n.陨星( meteorite的名词复数 )

参考例句：

• Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
• One theory about the existence of extraterrestrial life rests on the presence of carbon compounds in meteorites. 地球外存在生命的理论是基于陨星上存在碳化合物质这一事实的。 来自《简明英汉词典》

4 acoustics   

n.声学，(复)音响效果，音响装置

参考例句：

• The acoustics of the new concert hall are excellent.这座新音乐厅的音响效果极好。
• The auditorium has comfortable seating and modern acoustics.礼堂里有舒适的座椅和现代化的音响设备。

5 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句

6 violations   

违反( violation的名词复数 )； 冒犯； 违反（行为、事例）； 强奸

参考例句：

• This is one of the commonest traffic violations. 这是常见的违反交通规则之例。
• These violations of the code must cease forthwith. 这些违犯法规的行为必须立即停止。

7 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

8 barometer   

n.气压表，睛雨表，反应指标

参考例句：

• The barometer marked a continuing fall in atmospheric pressure.气压表表明气压在继续下降。
• The arrow on the barometer was pointing to"stormy".气压计上的箭头指向“有暴风雨”。

9 fluctuations   

波动，涨落，起伏( fluctuation的名词复数 )

参考例句：

• He showed the price fluctuations in a statistical table. 他用统计表显示价格的波动。
• There were so many unpredictable fluctuations on the Stock Exchange. 股票市场瞬息万变。

10 membrane   

n.薄膜，膜皮，羊皮纸

参考例句：

• A vibrating membrane in the ear helps to convey sounds to the brain.耳膜的振动帮助声音传送到大脑。
• A plastic membrane serves as selective diffusion barrier.一层塑料薄膜起着选择性渗透屏障的作用。