A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but dueto their differing velocities they slowly gain on or fall behind the disintegrating comet until a shroud of dust surrounds the entire cometary orbit. Astronomers have hypothesized that ameteor stream should broaden with time as the dust particles’ individual orbits are perturbed by planetary gravitational fields. A recent computer-modeling experiment tested thishypothesis by tracking the influence of planetary gravitation over a projected 5,000-year period on the position of a group of hypothetical dust particles. In the model, the particleswere randomly distributed throughout a computer simulation of the orbit of an actual meteor stream, the Geminid. The researcher found, as expected, that the computer-model streambroadened with time. Conventional theories, however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream. Surprisingly, thecomputer-model meteor stream gradually came to resemble a thick-walled, hollow pipe.
Whenever the Earth passes through a meteor stream, a meteor shower occurs. Moving at over 1,500,000 miles per day around its orbit, the Earth would take, on average, just over aday to cross the hollow, computer-model Geminid stream if the stream were 5,000 years old. Two brief periods of peak meteor activity during the shower would be observed, one as theEarth entered the thick-walled “pipe" and one as it exited. There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the twobursts of activity would vary from one year to the next.
Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 show just such a bifurcation, a secondaryburst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. The time intervals between the bursts suggest the actual Geminid stream isabout 3,000 years old.
The passage suggests that which of the following is a prediction concerning meteor streams that can be derived from both the conventional theories mentioned in the highlighted text and the new computer derived theory?
第一结构：A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities.
(1)These particles follow...
(2)Astronomers have hypothesized...
(3)A recent computer-modeling experiment...
(4)In the model, the particles ...
(5)Conventional theories, however...
第2结构：Whenever the Earth passes through a meteor stream, a meteor shower occurs. (1)Moving at..
(3)There is no reason why ...
第3结构：Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower?
(1)The Geminid data
(2)The time intervals between the bursts suggest the actual Geminid stream is about 3,000 years old.
(A) Dust particles in a meteor stream will usually be distributed evenly throughout any cross section of the steam.（与文章内容不符，传统理论认为中间密度大，两边稀，现代理论认为两边大，中间中空，没有一个认为是平均分布的）
(B) The orbits of most meteor streams should cross the orbit of the Earth at some point and give rise to a meteor shower.（文章为提及，文章（第2结构）是说当地球穿过meteor streams，产生流星雨，没有提到meteor streams的轨道和地球轨道cross造成流星雨）
(C) Over time the distribution of dust in a meteor stream will usually become denser at the outside edges of the stream than at the center.（与题干逻辑方向不符，题目问的是both 传统理论和现在的理论，选项C知识现代的理论内容）
(D) Meteor showers caused by by older meteor streams should be, on average, longer in duration than those caused by very young meteor streams. （第1结构，第5层次+第2结构，现代的研究发现，as expected ,meteor stream broaden with time,时间越久，越老的流星群越宽，地球穿过这个流星群产生的流星雨的持续时间就会越长，与层次内容相符)
(E) The individual dust particles in older meteor streams should be, on average, smaller than those that compose younger meteor streams.（文章未提及，新老流星群particle的大小问题）
哎 全文给我翻译了 这题目还是做不出来
这题是要找一个传统和电脑都能得出的结论，电脑说as expected time broaden啥的，可是划线的传统部分只说了stream的形状啊，还是不明白怎么得出来的d..
The researcher found, as expected, that the computer-model streambroadened with time
这篇难度真的有点高至少720加，读懂也很难做对尤其是时间压力1分半，这题找对应定位，就是broadened with time = longer in duration 时间对比！！
2019-07-14 17:16:43 回复
"有题做就不错了" 你这样的思维商业能发展就见鬼了 人家好心提意见是想让它更优化 比你所谓的商科思维更有远瞻性全局性好吧！
【Inference类题目做题技巧 来源：曼哈顿论坛】【Key Takeaways for Inference Questions】 (1) First, figure out where to look; the clues will be in the wording of the question itself. In this case, they highlighted a couple of words for us, but they also gave important direction when they asked what could be derived from both the theory and the model. (2) Whenever possible, know what you’re not looking for as well. In this case, the question asks where the theory and the model agree, not where they disagree. Because the passage does also give info about where the two contradict, chances are a trap answer will include that info. (3) If the text is just too hard to understand, use a couple of tactics to try to eliminate some wrong answers. Anything that isn’t actually mentioned in the passage can be crossed off. You can also use common sense; if something really doesn’t make sense in the real world, don’t guess that one.
2018-12-23 00:23:19 回复
这道题解题关键：问的是computer derived theory和convention这两个都同意的观点。 A：这是前者的观点，后者的观点是离中心越近中心越dense。 B：（曼哈顿论坛解释）文章中没有提到，且此选项读完之后也发现违背了常识，宇宙中那么多meteor Stream,怎么可能大多数的met Stream会越过地球的轨道呢？ （我的看法）紧接着的第二段说的是 earth pass though meteor stream,而不是meteor stream cross 地球的orbit.顺序搞反了。 C:这是与convention观点相反，convention不同意。我们要找的是BOTH agree. D：思路：定位到highlight所在原句后，从它前面一个句子开始仔细阅读。读完发现并没有computer和convention BOTH AGREE的内容。相反，讲得是他们各自的观点。而且原句中还有一个however的转折提示convention和computer对于distribution持不同观点。所以跳到后面看看有没有提示他们都同意的内容，第二段第一句说地球earth pass though meteor st时候会引发流星雨，而highlight所在原句前面一句说The researcher found, as expected, that the computer-model Stream broadened with time.即stream随着时间增长会扩大。既然地球经过这个Stream时会引发流星雨，那我们自然就可以推论出，越宽的Stream（即越老的）会cause 持续时间更长的流星雨。 E:第一段确实提到了dust particles,但是没有讲任何与它们size相关的事。 写在后面：考试的时候时间紧迫，不可能一步一步这么分析的。infer题有时候脑子转不过弯没法自己根据信息推出正确答案，用排除法比较。此题关键是抓住题目问的问题： INFER BOTH agree。那么只讲了某一方的观点就可以排除：AC。文中根本没有提到，没办法INFER的：E。再看剩下的BD，扫一眼B选项看到earth orbit直接定位到第二段，发现顺序不对，以及一看就不是两者的观点而是在描述科学现象，排除。 然后选D。
2018-11-18 20:10:53 回复
There is no reason why the Earth should always pass through the stream's exact center, so the time interval between the two bursts of activity would vary from one year to the next. 这句怎么解释？虽然说stream会随时间而变宽，但是后面又说了不一定过中心点，而离圆心越远的割线越短，距离圆心的距离不确定，两个burst的interval也不确定。怎么可以从interval的长度推断age呢？说不通啊