每次做完托福听力的讲座以后，除了重听回顾错题，迷惑的地方精听，以及积累陌生词汇/内容以外，总结讲座的话题和结构也很重要 + 也很有用。之前总结过教授打岔的方式，今天讲下如何从“内容”的角度总结，有助自己下一次的做题。
常会遇到讲 “假说” 内容的文章（特别是 life science, nature science 或者 social science 的话题），做多了以后，发现涉及到 “假说” 的，都包含这么几个部分的内容：- But what about those gas planets in the outer solar system, in the outer accretion disk? Well, the first theory says the accretion process was similar to the one that formed the rocky planets, with some key differences. Remember, the gas giants are farther from the sun, where temperatures are much colder. So, in the outer accretion disk, compounds like water and ammonia exist in frozen form. Closer to the sun, they're more likely to be vaporized by solar radiation. What this means is that in addition to rocky and metallic particles there would be other solids like frozen water and frozen ammonia.
- ...so more solid substances are available to clump into protoplanets, right?
- Precisely! So the solid cores of the gas giants could conceivably have formed by accretion. And once their mass reaches a certain point, around about 5 to 10 Earths, what would happen?
- Five to ten Earths? With a mass that big, I guess gravity would start to pull in more and more material faster, right?
- Material, meaning gas. It would rapidly pull in more and more gas from the accretion disk, so you end up with a solid core of rock, metal and ice surrounded by massive amounts of gas. That's the core accretion theory.非常漂亮的总分总结构，解释了一下 core accretion theory 是什么，一般这种比较抽象的话题，中间还会设计学生互动，去解释一些抽象概念或者强调一些重要内容。
Gause said that whenever you've got two similar species competing for the exact same limited resources, one of them will have some sort of advantage-however slight- that'll eventually enable this species to dominate and ultimately exclude the other one ...even cause it to become extinct. That's why Gause's hypothesis came to be called the "competitive exclusion principle." Gause did some lab experiments, like placing two paramecium species in the same environment where they'd have to compete for the same food. He found that, over time, one species was consistently able to drive out the other... to eliminate it from the habitat... just as his hypothesis predicted.在给出理论以后，教授会解释下学者是怎么得出这个理论的。Of course there have been a lot of theories over the centuries. The oldest recorded one is by the Greek historian Herodotus.He visited Egypt around 450 B.C.E.,when the pyramid was already 2,000 years old.His theory was that cranes were used. Much like we use cranes today to construct tall buildings.And Herodotus may have seen Egyptians using cranes made of wood. But the problem with this theory has to do with simple mechanics.A crane needs a wide and sturdy base to stand on or it will fall over.Well, as you get toward the top of the pyramid, there's really no place for a crane to stand. The stone blocks are too narrow to provide a base. Well, so much for that theory.教授介绍完假说后，解释这个假说不太可行，被推翻 + 原因。
- So, which theory's correct?
- That's the debate. Most of my colleagues favor core accretion. Personally, I think the accretion theory works for the formation of rocky planets, but not necessarily for gas planets.通常教授给出明确态度时，而且还和别人的不同，都是比较重要的考点，要认真听。
Sun Sun
毕业于爱默生，语言学学士学位及全球营销传播学硕士学位。
曾于马萨诸塞州州政府任布鲁斯议员的翻译，硕士毕业后在冰岛和波士顿工作了两年时间，参与了大量的商务会议及商务谈判。
主授托福®口语，托福®听力，托福®阅读，雅思听力，雅思口语，GRE/GMAT阅读，SAT 文法。
(2024.01.27) 托福口语30，托福写作30，托福听力30, 托福阅读30
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