标题: OG passage 23, 有特殊的地方 [打印本页] 作者: v22 时间: 2005-9-3 15:02 标题: OG passage 23, 有特殊的地方 New observations about the age of some globular clusters in our Milky Way galaxy have cast doubt on a long-held theory about how the galaxy was formed. The Milky Way contains about 125 globular clusters (compact groups of anywhere from several tens of thousands to perhaps a million stars) distributed in a roughly spherical halo around the galactic nucleus. The stars in these clusters are believed to have been born during the formation of the galaxy, and so may be considered relics of the original galactic nebula, holding vital clues to the way of the formation took place. The conventional theory of the formation of the galaxy contends that roughly 12 to 13 billion years ago the Milky Way formed over a relatively short time (about 200 million years) when a spherical cloud of gas collapsed under the pressure of its own gravity into a disc surrounded by a halo. Such a rapid formation of the galaxy would mean that all stars in the halo should be very nearly the same age. However, the astronomer Michael Bolte has found considerable variation in the ages of globular clusters. One of the clusters studied by Bolte is 2 billions years older than most other clusters in the galaxy, while another is 2 billion years younger. A colleague of Bolte contends that the cluster called Palomar 12 is 5 billion years younger than most other globular clusters. To explain the age differences among the globular clusters, astronomers are taking a second look at “renegade” theories. One such newly fashionable theory, first put forward by Richard Larson in the early 1970’s, argues that the halo of the Milky Way formed over a period of a billion or more years as hundreds of small gas clouds drifted about, collided, lost orbital energy, and finally collapsed into a centrally condensed elliptical system. Larson’s conception of a “lumpy and turbulent” protogalaxy is complemented by computer modeling done in the 1970’s by mathematician Alan Toomre, which suggests that closely interacting spiral galaxies could lose enough orbital energy to merge into a single galaxy. 这篇文章错了两道题目： 139. Which of the following, if true, would be most useful in supporting the conclusions drawn from recent observations about globular clusters? (A) There is firm evidence that the absolute age of the Milky Way galaxy is between 10 and 17 billion years. (B) A survey reveals that a galaxy close to the Milky Way galaxy contains globular clusters of ages close to the age of Palomar 12. E (C) A mathematical model proves that small gas clouds move in regular patterns. (D) Space probes indicate that the stars in the Milky Way galaxy are composed of several different types of gas. (E) （E）A study of over 1,500 individual stars in the halo of the Milky Way galaxy indicates wide discrepancies in there ages.‘这个题目虽然选对，我是用排除法的，因为其他的都比E离谱。但是E中有一个疑问，文章都没说到1,500 。。，没这个数字，选项就这样说出，真是混淆啊。这种题目实战中少见把？这个数字都没有啊！！！！都不明白出题目的人怎么推理的。。。 141. The passage suggests that Toomre’s work complements Larson’s theory because it (A) specifies more precisely the time frame proposed by Larson (B) subtly alters Larson’s theory to make it more plausible (C) supplements Larson’s hypothesis with direct astronomical observations C----D (D) provides theoretical support for the ideas suggested by Larson (D) （E）expands Larson’s theory to make it more widely applicable 这个题目我选了C的，答案为D/computer modeling 不是observations吗，怎么是theoretical ？美国那里是用computer 观察天文图片的啊！！不明白 140. If Bolte and his colleague are both correct, it can be inferred that the globular cluster Paloma 12 is approximately (A) 5 billion years younger than any other cluster in the galaxy (B) the same age as most other clusters in the galaxy (C) 7 billion years younger than another cluster in the galaxy (D) 12 billion years younger than most other clusters in the galaxy (C) (E) 2 billion years younger than most other clusters in the galaxy 选了E的，答案为C。其实E也不想选的，如果不能弄明白C，我就觉得没答案。 怎么要两个人预测的年数加起来，这个题目真是/Bolte预测早两年，his colleague预测早5年，那可以5年包含2年的呀。作者: v22 时间: 2005-9-4 19:43
顶一把作者: hhl3000 时间: 2006-1-22 13:54