OG11-verbal review-56-63-流星，如何来读科普类文章

yangluoya

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 pa rent comet，but due to 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 a meteor stream should broaden with time as the dust particles’ individual orbits are perturbed by planetary gravitational fields．A recent computer—modeling experiment tested this hypothesis by tracking the influence of planetary gravitation over a projected 1000··year period on the positions of a group of hypothetical dust particles．In the model，the particles were 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 stream broadened with time．Conventional theories，however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream．Surprisingly, the computer. 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 a little over 1500，000 miles per day around its orbit，the Earth would take，on average，just over a day 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 the Earth entered the thick-walled＂pipe＂and one as it exited．There is no reason why the Earl[h 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．

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 secondary burst 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 is about 3000 years old．

Questions 56-63 refer to the passage on page 41．

61．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 lines 18-19 and the new computer-derived theory?

(A)  Dust particles in a meteor stream will usually be distributed evenly throughout any cross section of the stream．

(B)  The orbits of most meteor streams should cross the orbit of the Earth at some point and give rise to a meteor shower．

(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．

(D)  Meteor showers caused by older meteor streams should be on average，longer in  duration than those caused by very young meteor streams。

(E)  The individual dust particles in older meteor streams should be, on average, smaller than those that compose younger meteor streams．

62．It can be inferred from the last paragraph of the passage that which of the following must be true of the Earth as it orbits the Sun?

(A)  Most meteor streams it encounters are more than 2，000 years old．

(B)  When passing through a meteor stream，it usually passes near to the stream's center．

(C)  It crosses the Geminid meteor stream once every year．

(D)  It usually takes over a day to cross the actual Geminid meteor stream．

(E)  It accounts for most of the gravitational perturbation affecting the Geminid meteor stream．

63．  Which of the following is an assumption underlying the last sentence of the passage?

(A)  In each of the years between 1970 and 1979，the Earth took exactly 19 hours to cross the Geminid meteor stream．

(B)  The comet associated with the Geminid meteor stream has totally disintegrated．

(C)  The Geminid meteor stream should continue to exist for at least 5，000 years．

(D)  The Geminid meteor stream has not broadened as rapidly as the conventional theories would have predicted．

(E)  The computer-model Geminid meteor stream provides an accurate representation of the  development of the actual Geminid stream．

 

 

61：OG说新老理论都认为a meteor stream should broaden with time ， 但是从原文来看，这应该只是新观点所认同的。文中有一个很明显的转折可以说明：The researcher found, as expected, that the computer. model stream broadened with time．Conventional theories，however, predicted that ......这个题感觉问题很大哦，找不出答案

62：虽然可以理解，但这个是一个很高要求的逻辑踢，不仅要涉及到其他段落，还要做进一步推理，有点像猜谜。

最后一句话是引用了一个公式，而这个公式是前一段理论模型中用到的。所以assumption 就是理论模型是正确的。

最后一句话是引用了一个公式，而这个公式是前一段理论模型中用到的。所以assumption 就是理论模型是正确的。

 做完这一篇才知道什么叫生不如死

 

[此贴子已经被作者于2007-7-13 15:11:02编辑过]

nuj_am

I don't wanna depress you, but this article is not difficult.

You should read OG10 P29, P47. That is much more生不如死, hehe