Passage 5
After evidence was obtained in the 1920s that the univer is expanding, it became reasonable to ask: Will the univer continue to expand indefinitely, or is there enough mass in it for the mutual attraction of its constituents to bring this expansion to a halt? // 提出问题宇宙是否会一直持续扩大下去还是会停止。 It can be calculated that the critical density（临界密度）of matter needed to brake the expansion and “clo” the univer is equivalent to three hydrogen atoms per cubic meter. //回答问题，当临界密度为一立方米中三个氢原子重量时，则可以停止。 But the density of the obrvable univer（对应后文看不见的宇宙部分）—luminous matter in the form of galaxies（插入语解释说明，可略读）—comes to only a fraction of this（注意代词的指代内容：临界密度，一立方米中三个氢原子重量）. If the expansion of the univer is to stop, there must be enough invisible matter in the univer to exceed the luminous matter in density by a factor of roughly 70. // 转折，看得见的宇宙的密度只是临界密度的一部分。因此，可以预测下段会探讨看不见的宇宙部分。
Our contribution to the arch for this “missing matter”（上一段中invisible matter的同义转换）has been to study the rotational velocity of galaxies at various distances from their center of rotation. // 孩子学习不好怎么办总述寻找宇宙中是否存在看不见的部分。 It has been known for some time that outside the bright nucleus of a typical spiral galaxy luminosity （重点信息词，可用于回文定位）falls off rapidly with distance豪情壮志的古诗 from the center.（实际情况） If luminosity were a true indicator of mass, most of the mass would be concentrated toward the center. （理论情况）// 通过光度和距离来探讨是否存在看不见的宇宙部分；实际情况是螺旋星系的光度随着距离的增加而下降符合理论情况光度向中心集中，证明存在物质。 Outside the nucleus the rotational velocity （重点信息词，可用于回文定位）would decrea geometrically with distance from the center, in conformity with Kepler’s law. （理论情况）Instead we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increas slightly. （实际情况）// 依据转动速度和距离探讨是否存在看不见的部分；实际情况是螺旋星系的转动速度随着距离的增加保持不变或小幅增加，不同于理论上的转动速度随距离下降。 This unexpected result indicates that the 现代装修风格falloff in luminous mass（上文中obrvable univer 的同义转
换）with distance from the center is balanced by an increa in电脑画画 nonluminous mass（invisible matter，missing matter的同义转换）. // 因为实际情况和理论的不同，得出结论宇宙中存在看不见的部分。 乌灵胶囊
Our findings suggest that（发现结果的推论）as much as 90 percent of the mass of the univer is not radiating at any wavelength with enough intensity to be detected on the Earth. Such dark matter could be in the form of extremely dim stars of low mass, of large planets like Jupiter, or of black holes, either small or massive. // 通过发现的结果，推断出宇宙中百分之九十的物质是看不见的。 While it has 想女朋友的句子not yet been determined whether this mass is sufficient to clo the univer, some physicists consider it significant（正评价词） that estimates are converging on the critical value. // 没有确定看不见的物质是否能停止宇宙持续扩大，但是肯定了其重要性。
逻辑简图：问题解决型写作结构
第一段：
第一层：提出问题宇宙是否会一直持续扩大下去还是会停止。
第二层：回答问题，当临界密度为一立方米中三个氢原子重量时，则可以停止。第三层：转折，提出看得见的宇宙部分的密度只是这个临界密度的一部分。因此，
可以预测下段会探讨看不见的宇宙部分。
第二段：
第一层：总述通过转动速度来寻找宇宙中是否存在看不见的部分。
第二层：螺旋星系的光度随着距离的增加而下降符合理论情况（光度向中心集中），证明存在物质。
第三层：螺旋星系的转动速度随着距离的增加保持不变或小幅增加，不同于理论上的转动速度随距离下降。
第四层：因为实际情况和理论的不同，得出结论宇宙中存在看不见的部分。
第三段：
第一层：通过发现的结果，推断出宇宙中百分之九十的物质是看不见的。
第二层：没有确定看不见的物质是否能停止宇宙持续扩大，但是肯定了其重要性。
1. The passage is primarily concerned with
主旨题（文章中没有topic ntence, 所以需要总结归纳文章结构内容）
(A) defending a controversial approach （为有争议的方法辩护，原文不符）
(B) criticizing an accepted view 杨善洲电影（批评一个已接受的观点，原文不符）
(C) summarizing rearch findings （总结研究发现的结果，符合原文二、三段的
信息）
(D) contrasting competing theories （对比相互矛盾的理论，原文不符）
(E) describing an innovative technique （描述一个创新的技术）
2. The authors’ study indicates that, in comparison with the outermost regions of a typical spiral galaxy, the region just outside the nucleus can be characterized as having
（细节题，通过spiral galaxy，rotational velocity，luminosity定位到第二段的第二、三层的实际情况的信息，螺旋星系的光度随着距离的增加而下降，转动速度随着距离的增加保持不变或小幅增加）
(A) higher rotational velocity and higher luminosity
(B) lower rotational velocity and higher luminosity
(C) lower rotational velocity and lower luminosity
(D) similar rotational velocity and higher luminosity
(E) similar rotational velocity and similar luminosity
3. The authors’ suggestion that “as much as 90 percent of the mass of the univer is not radiating at any wavelength with enough intensity to be detected on the Earth” (lines 34–37) would be most weakened if which of the following were discovered to be true?
（类似逻辑题，注意逻辑推理的条件和结论）
结论是：宇宙中百分之九十的物质是看不见的
文中在第二段提到证明看不见的物质，但前提是讨论a typical spiral galaxy螺旋星系的亮度和旋转速度来证明看不见的物质存在，所以削弱螺旋星系在宇宙中的比重，即可以削弱看不见的物质在宇宙中的比重。
(A) Spiral galaxies are less common than types of galaxies that contain little nonluminous matter.
(B) Luminous and nonluminous matter are compod of the same basic elements.
(C) The bright nucleus of a typical spiral galaxy also contains some nonluminous matter.
>msdtc
