GWD27-10 11 12

这篇黑洞的文章我全错了，看了一遍答案后还是想不通。请指教！

GWD27-Q10 to Q12:

 Astronomers theorize that a black

            hole forms when a massive object

            shrinks catastrophically under its own

Line gravity, leaving only a gravitational

  (5)field so strong that nothing escapes it.

Astronomers must infer the existence

of black holes, which are invisible,

from their gravitational influence on

the visible bodies surrounding them.

 (10)For example, observations indicate

that gas clouds in galaxy M87 are

whirling unusually fast about the gal-

axy’s center.  Most astronomers

believe that the large concentration

 (15)of mass at the galaxy’s center is a

black hole whose gravity is causing

the gas to whirl.  A few skeptics have

argued that the concentration of mass

necessary to explain the speed of the

 (20)whirling gas is not necessarily a black

             hole:  the concentration in M87 might

             be a cluster of a billion or so dim stars.

       The same hypothesis might have

been applied to the galaxy NGC 4258,

 (25)but the notion of such a cluster’s

existing in NGC 4258 was severely

undermined when astronomers mea-

sured the speed of a ring of dust and

gas rotating close to the galaxy’s

 (30)center.  From its speed, they calcu-

lated that the core’s density is more

than 40 times the density estimated

            for any other galaxy.  If the center of

NGC 4258 were a star cluster, the

 (35)stars would be so closely spaced

that collisions between individual

stars would have long ago torn the

cluster apart.

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Q10:

The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

1. The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole.

2. The concentration of mass at the center of M87 is probably a large cluster of dim stars.

C.     The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core.

D.     The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87.

E.      The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87.

Answer: D

这道题是否就是比较skeptics与most astronomers 观点相同的地方？

我之前没有想到most astronomers与D的关系，现在想明白了，Most astronomers

believe that the large concentration

 (15)of mass at the galaxy’s center is a

black hole whose gravity is causing

the gas to whirl. 

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Q11:

The passage asserts which of the following about the existence of black holes?

1. Astronomers first speculated about the existence of black holes when they observed gas whirling around the center of a particular galaxy.

2. Evidence used to argue for the existence of black holes is indirect, coming from their presumed effects on other astronomical bodies.

3. Recent observations of certain astronomical bodies have offered proof.

4. A considerable body of evidence suggests the existence of black holes, even though their behavior is not completely consistent with the laws of physics.

5. Many astronomers are skeptical about certain recent evidence that has been used to argue for the existence of black holes.

Answer: B

我选了A， 答案B究竟在说什么？哪里体现？------

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Q12:

Which of the following, if true, would most clearly undermine the possible explanation for the whirling gas in M87 that is mentioned in the last sentence of the first paragraph?

1. The stars in a star cluster at the center of M87 could exert a strong gravitational force without tearing the cluster apart.

2. A cluster of stars at the center would preclude the existence of certain other astronomical phenomena that have been observed at the center of M87.

3. The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.

4. Only one other galaxy has been observed to contain gas clouds whirling about its center as they do about the core of M87.

5. The gravitational force of a cluster of a billion or so dim stars would be sufficient to cause a whirling ring of gas and dust to collect around the center of a galaxy.

Answer: B

问题问如何削弱skeptics的观点，即如何削弱它是clusters, B是说如果M87是cluster,会与M87已存现象矛盾， 所以削弱。

但是我选了A， 现在才看出A是加强了。做题的时候完全看不出阿！！

Q11..Astronomers must infer the existence of black holes, which are invisible,from their gravitational influence on the visible bodies surrounding them.从这句看出B是对的.B的意思是证明黑洞存在的证据是间接从黑洞对其他星体的作用体现的.

Q12给的答案是A吧?我都是觉得A是加强,LZ的答案是哪里的?

Q12 答案是A or B?

我们怎么知道A是加强?

请大牛指点

A说star cluster会exert a strong gravitational force但又不会把cluster tear apart，正好驳斥了第二段反对star cluster的原因，故加强。