- 2018年04月13日13:37 来源：小站整理
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TPO 53 Lecture3听力原文文本
Listen to part of a lecture in an astronomy class.
Professor: Saturn’s rings have always baffled astronomers.Until about 30 years ago, we thought the rings were composed of particles of ice and rock that were left over from Saturn’s formation, extra material that never managed to form er...er coalesce into a moon.
As you know, it’s believed that Saturn and all the planets in our solar system, coalesced from a swirling cloud of gas some 4.8 billion years ago. However, if the rings are made of leftovers from that process, then they’d also be about 4.8 billion years old. The problem is that anything gathering space dust for that long would certainly have darkened by now.
But Saturn’s rings, most of them anyway, are pristine, so bright and shiny that they make Saturn “the jewel of the solar system”. So the hypothesis that the rings are just made of material left over from the time of planetary formation. That hypothesis must be wrong. Saturn’s rings are much younger than the planet itself. They may have formed only a few hundred million years ago, around the time the earliest dinosaurs lived on earth. We realize now that the ring particles, which range in size from microscopic dust to boulders, bigger than large houses, well, a lot of these particles are eventually lost. Then we believed they gradually spiral down out of the rings and into the planet’s atmosphere. This occurs as a result of the planet’s gravity. And also because of the effects of its magnetic field.
Now, if material from Saturn’s rings is being lost, and nothing new is added from time to time, the rings would be disappearing, but that’s not happening. So somehow, there must be new material feeding the ring system. Question is, where is this new material coming from? So, we’re back to square one. But, instead of asking how did the rings form, we should be asking… anyone? Beth?
Student: How do the rings form?
Professor: How do the rings form! Because they are apparently replenishing themselves somehow. OK, here is one possibility. The moons, the dozens of moons, they all orbit Saturn, are providing raw material for the rings.
A moon in the system is complex at Saturn’s, and Saturn has at least 49 known moons which vary tremendously in size and shape. A moon in such a complex system, is not only affected by the gravitational force of the planet, but also by that of the other moons.
Student: So the planet may be pulling a moon one way, and other moons may be pulling it other ways?
Professor: Exactly. Such forces could actually alter a moon's orbit, and as a result there might be a collision when moon might crash into another. And the debris from that collision could become part of the rings. Then there are tidalforces, a moon might get too close to the planet and get broken apart by Saturn's tidal forces.
Student: Excuse me! You mean, tidal force is like high tide and low tide on the oceans?
Professor: Well, by tidal force, I'm referring to the gravitational pull of Saturn on its moons. In the mid-1800s, a French scientist named Edouard Roche was studying the effects of a planet's tidal forces on its moons.Roche was able to show mathematically that if one celestial body, say a moon, if it passes too close to another, say a planet, that has a gravitational force stronger than the force of self-attraction that holds the moon together.
Well, that first body，that moon， it'd be ripped apart. We call the distance at which this happens the "Roche limit". So if one of Saturn's moons reaches the Roche limit of the planet, or even a larger moon, it would disintegrate, be torn apart and thus add more material to the ring system.
And there's another way new material might be added to the Saturn's rings, an asteroid crashing into one of the moons. This hypothesis is supported by the fact that some of the many rings are a bit reddish in color. Yes, George?
Student: I'm sorry, I don't follow the logic.
Professor: Well, this reddish coloration suggests the presence of complex organic molecules, carbon-based molecules, mixed in with the water ice. Remember, the rest of Saturn's rings are made almost entirely of water ice. And none of Saturn's moons is red. But asteroids could be. And thus could end up contributing to the ring system, the kind of carbon-based molecules we're talking about.
Question 1 of 6
What is the main purpose of the lecture?
A. To show the connection between asteroids and Saturn’s rings
B. To discuss theories about the formation of Saturn’s rings
C. To describe the composition of Saturn's rings
D. To show how Saturn’s rings affect the planet’s atmosphere
Question 2 of 6
What leads scientists to believe that Saturn's rings are much younger than the planet itself?
A. Most of the rings are bright and shiny.
B. Most of the rings are composed of complex materials.
C. The rings are much thinner than scientists realized.
D. There are small moons in between Saturn’s rings.
Question 3 of 6
Why do astronomers suspect that new material has been added to Saturn's ring system?
A. The number of moons orbiting Saturn has increased over time.
B. The rings exist in spite of Saturn’s gravity and magnetic pull.
C. The tidal forces of Saturn are stronger than previously believed.
D. The amount of water-ice in Saturn’s rings is smaller than previously believed.
Question 4 of 6
Why does the professor mention Edouard Roche?
A. To explain why Saturn's magnetic pull affects the orbits of Saturn's moons
B. To explain how much gravitational force is needed to make particles coalesce into a moon
C. To explain how a moon might contribute material to Saturn’s ring system
D. To explain why asteroids are attracted to Saturn’s ring system
Question 5 of 6
Why does the professor mention the reddish color in some of Saturn's rings?
A. To explain why he calls Saturn "the jewel of the solar system"
B. To prove that Saturn's rings and its moons are composed of similar material
C. To explain how scientists realized that the ring particles vary greatly in size
D. To support the possibility that some rings may contain molecules from an asteroid
Question 6 of 6
Why does the professor say this:
A. He wants the woman to answer her own question.
B. He wants the woman to rephrase her question.
C. He is glad that the woman understands the point he just made.
D. He believes that more research on ring formation is needed.
题目解析：本题定位到原文：Professor: Saturn’s rings have always baffle the astronomers. Until about 30 years ago, we thought the rings were composed of particles of ice and rock that were left over from Saturn’s formation. 此处原文是讲座开头，教授是以讲解土星环的构成开头的，听完全篇我们也可以发现，这一篇全篇就是在讲关于土星环形成的理论。 题干问的是这个讲座主要讲了什么东西。 选项A的意思是展示行星和土星环之间的联系，选项B的意思是讨论了土星环形成的理论，选项C的意思是描述了土星环的构成，选项D的意思是说明土星环是怎么影响行星的大气层的。选项B符合原文，其他三个选项则不合适。
题目解析：本题定位到原文：However, if the rings are made of left over some process, then they’d also be about 4.8 billion years old.......But Saturn’s rings, most of them anyway, are pristine, so bright and shiny that they make Saturn “the jewel of the solar system”. 此处原文的大意是：研究者本来认为，如果土星环是由气体旋转形成的话，那它们的年龄会是很老了，那么就会暗淡无光，但实际上土星环还是很明亮的，所以可能并没有已经形成了那么长时间。 题干问的是是什么让科学家相信土星环要比行星本身年轻得多的。 选项A的意思是很多土星环很明亮，闪闪发光，选项B的意思是很多土星环是由复杂材料构成的，选项C的意思是土星环比科学家意识到的要细，选项D的意思是土星环里有小的卫星。选项A符合原文，其他三个选项则不合适。
题目解析：本题定位到原文：Now, if material from Saturn’s rings has been lost, and nothing new is added from time to time, the rings would be disappearing, but that’s not happening. 此处原文的大意是：如果土星环里的材料会遗失的话，而且还没有新的东西补充的话，那土星环就会消失，但其实并没有消失。 题干问的是天文学家为什么怀疑土星环里有新的材料。 选项A的意思是环绕土星的卫星数量增加了，选项B的意思是尽管在重力和磁力的作用下，土星环还是存在的，选项C的意思是土星的潮汐比以前更强了，选项D的意思是土星环里的冰比以前少了。选项B符合原文，其余三个选项不合适。
题目解析：本题定位到原文：So if one of the Saturn's moons reaches the Roche limit of the planet, or even the larger moon, it would disintegrate between on a part and that said more material to the ring system. 此处原文的大意是：这里教授其实是想用Roche的极限理论说明，在引力的作用下，卫星会被撕裂，然后就成为了土星环的材料。 题干问的是教授为什么要提到Roche。 选项A的意思是解释为什么土星的磁场会影响土星卫星的轨迹，选项B的意思是解释要多大的重力才可以使粒子结合成卫星，选项C的意思是解释为什么卫星可能会为土星环提供材料，选项D的意思是解释为什么行星会被吸引到土星环系统。选项C符合原文，其余三个选项均不合适。
题目解析：本题定位到原文：Professor: Well, this reddish coloration suggests that the presence of complex organic molecules, carbon-based molecules, mixed in with the water ice. Remember, the rest of Saturn's rings are made almost entirely of water ice. And none of the Saturn's moon is red. 此处原文的大意是：这里教授的意思是土星环是发红的，发红其实意为着它里面有一些复杂分子存在。 题干问的是为什么教授要提到土星环发红。 选项A的意思是为了解释他为什么把土星环叫做太阳系的珠宝，选项B的意思是为了证明土星环和它的卫星是由相似材料构成的，选项C的意思是为了解释科学家是如何意识到土星环的物质在大小上差别很大的，选项D的意思是为了支持一些土星环可能会含有行星里面的例子的可能性。选项D符合原文，其余三个选项则不合适。
题目解析：本题定位到原文：Professor: How do the rings form! 此处原文的大意是：这里是教授先故意停顿了一下，让学生猜他接下来要说什么，女生猜中了，教授很开心，就加重语气重复了一遍女生的话。 题干问的是教授为什么要说这句话。 选项A的意思是他想要女生去回答她自己的问题，选项B的意思是她想要女生改述一遍自己的问题，选项C的意思是他很开心女生明白了他想说的点，选项D的意思是他相信更多的关于土星环形成的理论是需要的。选项C符合原文，其余三个选项则不合适。