OG13-RC 117 阅读中的一道逻辑题没看懂啊？急死啦！求大侠！

木以晨夕 · 发表于 2013-8-1 21:52:10

这道题看了OG还是没有明白，OG的意思是"If spiral galaxies were found to be atypical of galaxies, then the author's conclusion would be based on a sample of galaxies not representative of the whole, and their argument would be seriously weakened."

但是选项（A）直说了Spiral galaxies are less common than types of galaxies that contain little nonluminous matter. less common可以说明是非典型吗？

最好来个逻辑图，本人逻辑真心差。。。。。

Line After evidence was obtained in the 1920s that

the universe is expanding, it became reasonable

to ask: Will the universe continue to expand

indefinitely, or is there enough mass in it for the

(5) mutual attraction of its constituents to bring this

expansion to a halt? It can be calculated that

the critical density of matter needed to brake the

expansion and "close" the universe is equivalent

to three hydrogen atoms per cubic meter. But the

(10) density of the observable universe—luminous matter

in the form of galaxies—comes to only a fraction

of this. If the expansion of the universe is to stop,

there must be enough invisible matter in the

universe to exceed the luminous matter in density

(15) by a factor of roughly 70.

Our contribution to the search for this "missing

matter" has been to study the rotational velocity

of galaxies at various distances from their center

of rotation. It has been known for some time that

(20) outside the bright nucleus of a typical spiral galaxy

luminosity falls off rapidly with distance from the

center. If luminosity were a true indicator of mass,

most of the mass would be concentrated toward

the center. Outside the nucleus the rotational

(25) velocitywould decrease geometricallywith distance

from the center, in conformity with Kepler's law.

Instead we have found that the rotational velocity

in spiral galaxies either remains constant with

increasing distance from the center or increases

(30) slightly. This unexpected result indicates that the

falloff in luminous mass with distance from the

center is balanced by an increase in nonluminous

mass.

Ourfindings suggest that as much as 90
(35) percent of the mass of the universe 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,

(40) either small or massive. While it has not yet been

determined whether this mass is sufficient to

close the universe, some physicists consider it

significant that estimates are converging on the

critical value.

The authors' suggestion that "as much as 90 percent

of the mass of the universe 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?

(A) Spiral galaxies are less common than types of

galaxies that contain little nonluminous matter.

(B) Luminous and nonluminous matter are

composed of the same basic elements.

(C) The bright nucleus of a typical spiral galaxy also

contains some nonluminous matter.

(D) The density of the observable universe is

greater than most previous estimates have

suggested.

(E) Some galaxies do not rotate or rotate too slowly

for their rotational velocity to be measured.

木以晨夕 · 发表于 2013-8-1 23:58:26

有人吗？自己顶！

lhz910216 · 发表于 2013-8-3 16:33:32

做这道题目首先必须理解上下文
16-33行，一直在说a typical spiral galaxy的情况，最后一句话说This unexpected result indicates that the
falloff in luminous mass with distance from the
center is balanced by an increase in nonluminous
mass.
题目中说宇宙中90%是这种nonluminous mass（参考的就是上述提到的spiral galaxy）
A选项说spiral galaxy非典型，就是not common，不能代表大多数galaxy的情况，因为有很多galaxy几乎不含nonluminous mass
这也就说只由spiral galaxy中的nonluminous mass含量是不能推断整个宇宙的，所以是weaken。

不止这么说你明白不，实在不会画图~

木以晨夕 · 发表于 2013-8-3 18:06:20

lhz910216 发表于 2013-8-3 16:33
做这道题目首先必须理解上下文
16-33行，一直在说a typical spiral galaxy的情况，最后一句话说This unexpe ...

明白了，LS说得听清楚的，谢谢！！！

mogu724 · 发表于 2013-8-28 23:18:36

lhz910216 发表于 2013-8-3 16:33
做这道题目首先必须理解上下文
16-33行，一直在说a typical spiral galaxy的情况，最后一句话说This unexpe ...

大侠看看我的想法对不对呗

文中reaserch是关于 typical 的情况发现了随着luminous的减少 nonluminous增多得出了个结论：宇宙中90%都是non

A是说观察的这个 spiral 不typical ，包含少的non 所以不能得出宇宙中大多数都是non

是从假设推翻了argument么？一开始假设spiral typical 后来用非typical来削弱

ciciwenwen · 发表于 2014-1-14 22:34:36

mogu724 发表于 2013-8-28 23:18
大侠看看我的想法对不对呗

文中reaserch是关于 typical 的情况发现了随着luminous的减少 nonluminous ...

作者说在漩涡星云中，9成是暗物质，本来他也说很多都是看不见的，意思就是质量基本都在暗物质上。于是他认为宇宙中其他星云也是这样的构造-----暗物质绝对质量多余光物质。但是假设漩涡星云只是星系中很少见的一种呢？即如果其他星云都是极少有暗物质而基本是光物质呢？那就weaken了他的言论。

OG13-RC 117 阅读中的一道逻辑题没看懂啊？急死啦！求大侠！

所属分类: GMAT考试

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