Until recently most astronomers believed that the space between the galaxies in our universe was a near-perfect vacuum. This orthodox view of the universe is now being challenged by astronomers who believe that a heavy “rain” of gas is falling into many galaxies from the supposedly empty space around them. The gas apparently condenses into a collection of small stars, each a little larger than the planet Jupiter. These stars vastly outnumber the other stars in a given galaxy. The amount of “intergalactic rainfall” into some of these galaxies has been enough to double their mass in the time since they formed. Scientists have begun to suspect that this intergalactic gas is probably a mixture of gases left over from the “big bang” when the galaxies were formed and gas was forced out of galaxies by supernova explosions.
It is well known that when gas is cooled at a constant pressure its volume decreases. Thus, the physicist Fabian reasoned that as intergalactic gas cools, the cooler gas shrinks inward toward the center of the galaxy. Meanwhile its place is taken by hotter intergalactic gas from farther out on the edge of the galaxy, which cools as it is compressed and flows into the galaxy. The net result is a continuous flow of gas, starting as hot gases in intergalactic space and ending as a drizzle of cool gas called a “cooling flow,” falling into the central galaxy.
A fairly heretical idea in the 1970’s, the cooling-flow theory gained support when Fabian observed a cluster of galaxies in the constellation Perseus and found the central galaxy, NGC 1275, to be a strange-looking object with irregular, thin strands of gas radiating from it. According to previous speculation, these strands were gases that had been blown out by an explosion in the galaxy. Fabian, however, disagreed. Because the strands of gas radiating from NGC 1275 are visible in optical photographs, Fabian suggested that such strands consisted not of gas blown out of the galaxy but of cooling flows of gas streaming inward. He noted that the wavelengths of the radiation emitted by a gas would changes as the gas cooled, so that as the gas flowed into the galaxy and became cooler, it would emit not x-rays, but visible light, like that which was captured in the photographs. Fabian’s hypothesis was supported by Canizares’ determination in 1982 that most of the gas in the Perseus cluster was at a temperature of 80 million degrees Kelvin, whereas the gas immediately surrounding NGC 1275 (the subject of the photographs) was at one-tenth this temperature.
1. The primary purpose of the passage is to
(A) illustrate a hypothesis about the origin of galaxies
(B) provide evidence to dispute an accepted theory about the evolution of galaxies
(C) summarize the state of and prospects for research in intergalactic astronomy
(D) report new data on the origins of intergalactic gas（B）
(E) reconcile opposing views on the formation of intergalactic gas
答案d 为什么不对呢？ 我觉得文章主要讲的是intergalactic gas。 而b 是说 evolution of galaxies. 而且很多新老观点的文章primary purpose 都不是refute 旧观点，而是支持论述新观点。 我感到迷惑，不知道怎样确定新老观点文章中的主题题。 不知道NN们有什么好的办法。请指教。
我和楼主有同样的疑问.
请问如何search别人的discussion? 好象唯一的方法就是search 33. 而我只看到这片讨论.
ding. I have the same question.
http://forum.chasedream.com/dispbbs.asp?BoardID=25&ID=88351
以上供参考。我觉得还是B概括了全文的中心意思。
我有同样的问题。看了wangyu得全文解释，还是不知道为什么文章是讨论the evolution of galaxies的呀？总觉得是关于intergalactic gas的。所以选的时候，自动排除了A和B。
再问
The primary purpose of the passage is to
(A) illustrate a hypothesis about the origin of galaxies
(B) provide evidence to dispute an accepted theory about the evolution of galaxies
(C) summarize the state of and prospects for research in intergalactic astronomy
(D) report new data on the origins of intergalactic gas（B）
(E) reconcile opposing views on the formation of intergalactic gas
文章开始提出传统理论，星系间为真空。后来提出新理论，星系间存在气体且使星系壮大。此后，文章对新理论进行了论据支持，从而反对了传统理论。传统理论和新理论的内容都是与星系演化紧密相关的。
供参考。
仅比较B里的evolution和D里的origins就能判断哪个好啊。
文章来回说气体怎么怎么冷却收缩东东，一直在说一个变化过程啊。新理论里气体本来就有，没说气体从哪里来，只说它怎么变变变！ 哈哈
不论是 支持新的 还是 驳斥旧的， 横竖都体现了新老，那就行啦！
哎，刚才我好像误会LZ的意思了。
对啊对啊，新老对比，作者当然要就是新的！老的都认可，他何必要写啊。
所以主题当然是 支持新观点阿
4. The author of the passage probably mentions Canizares’ determination in order to
(A) clarify an ambiguity in Fabian’s research findings
(B) illustrate a generalization about the temperature of gas in a galaxy cluster
(C) introduce a new argument in support of the orthodox view of galaxies
(D) provide support for Fabian’s assertions about the Perseus galaxies（D）
(E) provide an alternate point of view concerning the movement of gas within a galaxy cluster
我觉得B也沾边啊，虽然是D更好些。那B有哪里不很合适呢？如果没有D是不是B也可以呢？
谢谢～
可用反证法排除D:如果D正确，那么什么是origin of intergalactic gas呢?
文章中就提到一句Scientists have begun to suspect that this intergalactic gas is probably a mixture of gases left over from the “big bang” when the galaxies were formed and gas was forced out of galaxies by supernova explosions.
而文章中的其他文字，都是在说intergalactic gas形成后怎么流入galaxy,所以可以排除D(包括A).
一家之见，大家继续讨论．
看了翻译，还是觉得有问题。
正如前面众XDJM说的，旧观点说space between the galaxies in our universe was a near-perfect vacuum
新观点说astronomers who believe that a heavy “rain” of gas is falling into many galaxies from the supposedly empty space around them
要比较也只能是这两样东西的比较
B很有问题~为什么不是D啊~
看了翻译，还是觉得有问题。
正如前面众XDJM说的，旧观点说space between the galaxies in our universe was a near-perfect vacuum
新观点说astronomers who believe that a heavy “rain” of gas is falling into many galaxies from the supposedly empty space around them
要比较也只能是这两样东西的比较
B很有问题~为什么不是D啊~
同问: 文章不是都说明space between galaxies,
没有人选C么
文章结构:
1p: 一个orthodox view 提出challenge此orthodox view一个解释 big bang explosion gas from the galaxy
2p: 提出另一个解释 cooling gas flow streaming inward
3p: 给出正评价的解释是cooling gas flow streaming inward 以P的例子来解释为什么
整篇文章的大构架是
反对orthodox view
之后是两个反对orthodox view的解释角逐
最后选了cooling gas flow streaming inward但是不论这两个解释如何角逐
总的要点是要反对orthodox view
1. 错误原因没有理解清楚逻辑结构The primary purpose of the passage is to
(A) illustrate a hypothesis about the origin of galaxies 首先不是a hypothesis 而是两个 其次不是origin of galaxies这个内容
(B) provide evidence to dispute an accepted theory about the evolution of galaxies
(C) summarize the state of and prospects for research in intergalactic astronomy如果没有理解了逻辑结构就会选C 关键是要明白文章整个大的构架是要反对orthodox view 不论这个大构架里面做了怎样的引申和转折
(D) report new data on the origins of intergalactic gas（B）没有new data
(E) reconcile opposing views on the formation of intergalactic gas 没有reconcile
天蝎座1107 发表于 2009-7-29 10:45
文章结构:1p: 一个orthodox view 提出challenge此orthodox view一个解释 big bang explosion gas fro ...
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