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After evidence was obtained in the 1920s that the universe

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After evidence was obtained in the 1920s that the universe [#permalink] New post 30 Aug 2009, 01:15
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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 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 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 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 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 velocity would decrease geometrically with 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 slightly. This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.

Our findings suggest 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. 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. 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.[/size]
115. The passage is primarily concerned with
(A) defending a controversial approach
(B) criticizing an accepted view
(C) summarizing research findings
(D) contrasting competing theories
(E) describing an innovative technique
[Reveal] Spoiler:
C


116. 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
(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
[Reveal] Spoiler:
D


117. 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.
[Reveal] Spoiler:
A


118. It can be inferred from information presented in the passage that if the density of the universe were equivalent to significantly less than three hydrogen atoms per cubic meter, which of the following would be true as a consequence?
(A) Luminosity would be a true indicator of mass.
(B) Different regions in spiral galaxies would rotate at the same velocity.
(C) The universe would continue to expand indefinitely.
(D) The density of the invisible matter in the universe would have to be more than 70 times the density of the luminous matter.
(E) More of the invisible matter in spiral galaxies would have to be located in their nuclei than in their outer regions.
[Reveal] Spoiler:
C


119. The authors propose all of the following as possibly contributing to the “missing matter” in spiral galaxies EXCEPT
(A) massive black holes
(B) small black holes
(C) small, dim stars
(D) massive stars
(E) large planets
[Reveal] Spoiler:
D



My take and approach with OEs are here..
[Reveal] Spoiler:
115,,,C..by PoE...easy..
116..D..easy
117..Misread the Q..got wrong..OA says..A...Correct. The authors’ conclusion assumes that spiral galaxies are typical of all galaxies;information calling that assumption into question weakens the argument.
118.....again misread the Q
119..straight D

Last edited by nitya34 on 31 Aug 2009, 07:45, edited 1 time in total.
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Re: RC -universe is expanding [#permalink] New post 30 Aug 2009, 04:56
I took 6 minutes, so guessing most of my answers are wrong :(

here are my answers
E,D,E,C,E
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Re: RC -universe is expanding [#permalink] New post 30 Aug 2009, 05:12
My answers : CDADD
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Re: RC -universe is expanding [#permalink] New post 31 Aug 2009, 06:11
my answers: CDDCE
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Re: RC -universe is expanding [#permalink] New post 31 Aug 2009, 07:46
Posted the OAs alongwith the original post...i will try to post the OEs in few inference Qs
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Re: RC -universe is expanding [#permalink] New post 31 Aug 2009, 14:12
115. C
116. A -- Incorrect (D)
117. D -- Incorrect (A)
118. D -- Incorrect (C)
119. D
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Re: RC -universe is expanding [#permalink] New post 04 Oct 2009, 10:16
This OG RC passage has the first two questions on which I don't agree with the OA.

116.
Passage says: Velocity either remains constant with increasing distance from the center or increases slightly.
Question: compare "outermost regions" vs "region just outside the nucleus".
=> "region just outside the nucleus" could have either similar or lower velocity.
=> Both B and D could be right; a case for D has strong foundations given that we are comparing the "region just outside the nucleus" with the "outermost region" -> greatest possible distance withing the galaxy.

117.
OA is A. I believe A is wrong. Explanation:
"Galaxies that contain little nonluminous matter" = dark matter (in the form of either dim stars, black holes or large planets). Thus, spiral galaxies being less common than "obscure" galaxies does not weaken the 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".
D is the best answer. If the density of the observable universe (small fraction) is increased, that 90% would be lower; increase the fraction significantly, and you can have an observable reduction in that 90%.
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Re: RC -universe is expanding [#permalink] New post 05 Oct 2009, 21:39
115.c
116.a
117.a
118.c
119.e
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Re: RC -universe is expanding [#permalink] New post 05 Oct 2009, 22:06
CDACD
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Re: RC -universe is expanding [#permalink] New post 16 May 2010, 07:49
this RC passage was hard for me. :evil:
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Re: RC -universe is expanding [#permalink] New post 09 Jul 2011, 01:46
I agree, question 116 is clearly ambiguous.
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Re: RC -universe is expanding [#permalink] New post 13 Jul 2011, 15:25
I think the questions could be worded somewhat better but my answers were:
D, C, E, D, D
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Re: RC -universe is expanding [#permalink] New post 02 Sep 2011, 12:18
in #117, why is C incorrect?
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Re: Source:OG 12 After evidence was obtained in the 1920s that [#permalink] New post 25 Jun 2012, 15:42
Took 10 minutes but got only 1 wrong. I think I just got lucky with the answer choices. :-D

Does anybody have a good explanation for 117?
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Re: After evidence was obtained in the 1920s that the universe [#permalink] New post 08 Nov 2012, 07:16
Answer of question 118: The universe would continue to expand indefinitely.
Isn't the passage gives a limit to expand, so doesn't "indefinitely" makes it wrong?
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Re: After evidence was obtained in the 1920s that the universe [#permalink] New post 13 Aug 2013, 09:01
My answers.
C,D ,B,C,D.

Got 1 wrong. :)
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Re: After evidence was obtained in the 1920s that the universe [#permalink] New post 14 Aug 2013, 21:10
Couldn't get Q117..Can some give a detailed explanation please
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Re: After evidence was obtained in the 1920s that the universe [#permalink] New post 14 Aug 2013, 21:35
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akankshasoneja wrote:
Couldn't get Q117..Can some give a detailed explanation please


hi

117. 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.

see the author is concluding:
Our findings suggest 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.
(last para 1st line)
what is the basis of this conclusion:

It has been known for some time that 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 velocity would decrease geometrically with distance from the center, in conformity with Kepler’s law. Instead we have found thatthe rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly.This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.

so author experiment is onTYPICAL galaxy ==>some results came==>then he concluded.
see the flaw is he is considering only a limited source of galaxy and generalising for whole universe.

so the ultimate weakener that is option B:
Spiral galaxies are less common than types of galaxies that contain little nonluminous matter.
SO this is saying that typical spiral galaxy are less number hence whatever conclusion author is trying to make can be wrong.

hope it helps
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Re: After evidence was obtained in the 1920s that the universe [#permalink] New post 15 Aug 2013, 09:03
blueseas wrote:
akankshasoneja wrote:
Couldn't get Q117..Can some give a detailed explanation please


hi

117. 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.

see the author is concluding:
Our findings suggest 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.
(last para 1st line)
what is the basis of this conclusion:

It has been known for some time that 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 velocity would decrease geometrically with distance from the center, in conformity with Kepler’s law. Instead we have found thatthe rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly.This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.

so author experiment is onTYPICAL galaxy ==>some results came==>then he concluded.
see the flaw is he is considering only a limited source of galaxy and generalising for whole universe.

so the ultimate weakener that is option B:
Spiral galaxies are less common than types of galaxies that contain little nonluminous matter.
SO this is saying that typical spiral galaxy are less number hence whatever conclusion author is trying to make can be wrong.

hope it helps

yes it did...thanks...:)
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Re: After evidence was obtained in the 1920s that the universe [#permalink] New post 23 Aug 2013, 07:36
Completed within 10mins with 1 wrong. :x :x

Though I got 117 correct using POE :!: I would like to know the definite rationale to eliminate option D.:?:
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Re: After evidence was obtained in the 1920s that the universe   [#permalink] 23 Aug 2013, 07:36
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