考满分 toefl

1 .listen to part of a lecture in an astronomy class

听一段天文学课上的讲座。

1 .P: Earth and the planet Venus are neighbors. They're approximately the same size and have approximately the same mass, but the surface temperature on Venus is far hotter than the hottest regions on earth, and the atmosphere of Venus exerts more than 90 times the pressure exerted by Earth's atmosphere. And Venus is surrounded by clouds loaded with sulfuric acid, clouds so dense that optical telescopes can't penetrate them. Robert?

教授: 地球和金星是邻居。它们大小相近，质量也大致相当，但金星表面温度远高于地球最热地区，金星大气压更是地球的90多倍。而且金星被充满硫酸的厚密云层包裹，这些云层密度极高，光学望远镜无法穿透。罗伯特？

2 .S: But the textbook goes into a lot of detail about the surface features of Venus, like there are a lot of volcanoes and most of the craters look pretty fresh and stuff like that. P: That's right.

学生: 但教科书详细描述了金星表面特征，比如有很多火山，大部分陨石坑看起来都很新之类的。 教授: 确实如此。

1 .S: How can we know that if we can't see through the clouds? P: Good question. The answer is that the clouds block light waves, but they don't block radar waves. So in the 1990s the United States sent an orbiting space probe to Venus. It was called Magellan. Magellan's mission was to collect radar data and relay them back to Earth, where they were used to create a detailed map of the planet. The European Space Agency did the same thing in 2005 when they sent up a probe called Venus Express, which brings me to my next point.

学生: 既然我们无法穿透云层观测，这些信息是如何获得的呢？ 教授：这个问题很好。答案是云层会阻挡光波，但不会阻挡雷达波。因此，在20世纪90年代，美国向金星发射了一个轨道探测器，名为"麦哲伦号"。麦哲伦号的任务是收集雷达数据并将其传回地球，这些数据被用于绘制行星的详细地图。欧洲航天局在2005年也做了同样的事情，他们发射了一个名为"金星快车"的探测器——这正好引出我要说的下个重点.

1 .These probes Magellan and Venus Express mapped the same area. So we should have been able to lay these two maps, one on top of the other, and see the same volcanoes and craters in exactly the same places, even though the information was collected 15 years apart. But that's not what happened when the two maps were compared. The surface features didn't line up, and the explanation researchers arrived at was that the rate of Venus's rotation had changed, that Venus was rotating at a slower rate when Venus Express was in orbit than when Magellan was in orbit.

麦哲伦号和金星快车这两个探测器绘制的是同一区域的地图。因此，我们应该能够将这两张地图叠放在一起，看到火山和陨石坑完全处于相同的位置，尽管这是相隔15年采集的数据。但实际对比时发现，地表特征的位置并不匹配。研究人员得出的结论是：金星自转速率发生了变化——当金星快车在轨运行时，金星的自转速度比麦哲伦号探测时期更慢了。

1 .Now we've already known for some time that Venus rotates very slowly. One day on Venus is equal to eight months on Earth. The academic year at this university runs from September to May. That's about a single day on Venus. Uh, but the discrepancy between these maps suggests that its rotation has slowed even more by six and a half minutes. Okay, granted, there could be something out of whack here. The instruments on either Magellan or Venus Express might have malfunctioned, but long range radar mapping of Venus has also been done from earth based observatories, and it's shown the same result. So what's putting the brakes on Venus, assuming the slowdowns for real，Jennifer？

其实我们早就知道金星自转非常缓慢，金星上的一天相当于地球的八个月。例如我们大学的学年从九月持续到五月，这段时间大约相当于金星上的一天。但这两张地图的差异表明，其自转速度又额外减缓了六分半钟。当然，这里可能存在误差——麦哲伦号或金星快车的仪器可能出现故障。但地基天文台进行的远程雷达测绘也显示了相同结果。那么，假设这种减速真实存在，究竟是什么在给金星"刹车"呢？詹妮弗。

2 .S: Well, you said it's covered by dense clouds. Could they have something to do with it? P: They could indeed. Not only does Venus have impenetrably dense clouds, it also has powerful winds reaching speeds of more than 200 miles per hour. And the best theory we have right now is that these high intensity weather systems are causing a lot of friction against the planet's surface. Over the long term, that friction is putting the brakes on the planet's rotation.

学生：教授，您提到金星有厚密云层，这和减速有关吗？ 教授：确实可能相关。金星不仅有无法穿透的厚密云层，还存在着时速超过200英里（约322公里）的强风。目前最合理的理论是：这些高强度天气系统与地表产生剧烈摩擦，长期作用下逐渐减缓了行星自转。

3 .S: Can the same thing happen here on earth? P: Well, our winds and tides do have some effect on Earth's rotation, but it's minimal, just tiny fractions of a second over long periods of time, nothing like what's apparently happened on Venus. One thing it'd be very helpful to know is whether Venus has a liquid core or a solid core. The type of core would influence how Venus reacts to various external forces, and speaking of Earth, the more we learn about the forces, particularly the atmospheric forces, that have shaped the evolution of Venus, the more insight we'll have into the forces that are currently shaping the evolution of Earth. So we really need to land a probe on the surface.

学生: 地球也会发生类似现象吗？ 教授: 地球的风和潮汐对自转确实有影响，但程度极小——长期来看只是秒的小数点变化，远不及金星的变化。如果能确定金星内核是液态还是固态，将极大帮助我们理解其对外力的反应。说到地球，我们越了解影响金星变化的外力，特别是大气压力，就越能洞察当前影响地球演变的因素。因此我们亟需向金星表面投放探测器。

4 .S: On the surface? P: The Russians did it in the 1970s and 80s. But because of the intense heat and pressure, none of them lasted more than two hours. Of course, the technology's come a long way since then. The thing is, there's only so much funding available for space exploration, and Venus missions are currently not that high on the priority list.

学生: 在表面着陆？ 教授: 苏联在1970-80年代实施过此类任务。但由于极端高温高压，探测器存活都不超过两小时。当然现在技术进步很多，但问题是航天探索资金有限，金星任务目前优先级不高。