After evidence was obtained in the 1920s that the universe is expandin

Hi! But the region just outside the center is not the center, the center is the center. Thus the region outside the nucleus has lower lumosity than the nucleus, no?

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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

As per passage rotational velocity is similar but the main Achilles heel is the higher luminosity part.

Author compares the outermost region with the region JUST outside nucleus.

and as is evident from the prompt, the luminosity is maximum at nucleus, lesser outside nucleus and least at the outermost regions of a typical spiral galaxy!

I was also confused between D and E and wrongly selected E.

But correct answer is D.

Cleverly written question!

P1: Will the universe continue to expand? Critical Density = 3H to close the universe, but it’s very low; close universe – enough invisible matter to exceed the luminous matter in density.

P2: Search for missing matter – study rotational velocity of galaxies from the center of rotation; Proven wrong: Luminosity falls of rapidly with distance from center; Proven: Luminosity is balanced by an increase the nonluminous mass

P3: 90% of the mass of universe in not radiating any wavelength and it CAN be helpful to find out if the universe will continue to expand.

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

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

“This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.”

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.

Thank you GMATNinja, your reply to this question was very helpful.

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.

“Will the universe continue to expand? Critical Density = 3H to close the universe, but it’s very low; close universe – enough invisible matter to exceed the luminous matter in density.”

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

“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.”

GittinGud, the concepts in this passage can be confusing! Breaking the relevant part of the passage down into smaller chunks can help establish that relationship:

This sentence tells us that there needs to be a density of at least 3 hydrogen atoms per cubic meter to stop the expansion of the universe.

Here is where we get information about the luminous and nonluminous matter. This sentence tells us that the amount of luminous matter does not come close to reaching that 3 hydrogen atoms per cubic meter threshold. So, if the expansion of the universe is to stop, there must be a large amount of nonluminous.

Don't get too bogged down in the exact numbers -- to answer the question, we only need the information explained above. Here's the question again:

We know from the first excerpt of the passage that to stop expansion of the universe we need at least three hydrogen atoms per cubic meter. So, if the density is equivalent to "significantly less" than that number, we know that the universe will not stop expanding. This corresponds nicely to answer choice (C), which is the correct answer.

I hope this answers your question!

AjiteshArun DmitryFarber
Can you please help in Q1 ?
I marked B as the author is crticizing the accepted view regarding the rotational velocity
I rejected C because the author is not summarizing he just told us about the findings

teaserbae

In a global purpose question, think about answer to one question:
Why the author has written the entire passage?


The author is not criticizing the accepted view.
He is sharing his findings which were different from Kepler's law


Do not get lost in details, missing the bigger picture.
Para 1 talks about the discussion of enough material to stop an expansion of the universe.
Para 2 talks about the relationship between rotational speed and missing matter.
Para 3 talks about the significance of dark matter.

If you now zoom out, you can see while C makes apt choice.
Happy study prep

adkikani is right: the author provides us "our contribution to the search for this 'missing matter'..." and then continues with "our findings suggest that as much as 90 percent..."

The passage says:

Instead we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly.

This means that rotational velocity either increases (slightly) with distance from the center or remains the same. That in turn means that as we get closer to the center, the rotational velocity either decreases slightly or remains the same. In other words: (a) close to center = slower (or the same) and (b) far from the center = faster (or the same).

The question asks us to complete:

... in comparison with the outermost regions of a typical spiral galaxy, the region just outside the nucleus can be characterized as having _______.

Because the outermost regions have the same rotational velocity as, or a slightly higher rotational velocity than regions closer to the center, we cannot say that the region just outside the nucleus has higher rotational velocity than the outermost regions (option A).

Actually once the answer is known it is very easy to find the way to reach not true the other way round. I cannot understand how do we know that for the highlighted conclusion the same spiral galaxies were used.He just mentions that our findings....from what not given.

The paragraph goes on to explain the question that whether the universe will stop expanding?
The author introduces a study and infers result out of that study.
Q1. The primary purpose of the passage is to summarize a research finding. Hence C is the right choice.
Q2. It is stated in the 2nd paragraph that, the luminosity decreases as the distance from the center of the nucleus increases and the rotational velocity remains constant, which was surprising.
Hence we can say that when compared to the outermost layer, the layer just outside the nucleus will have higher luminosity and similar rotational velocity.

Q3. The highlighted text states that 90% is not radiating with enough wavelength, and this lies on the fact that the spiral galaxy contains non luminous mass as the distance from the center of the nucleus increases. Hence if spiral galaxies are less common than other types of galaxies that contain little luminous mass the argument falls apart. Hence A.

Can someone explain the OA for Question Number 118?

OE
Q1. 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
Main idea
Figuring out the authors’ primary concern depends on a careful review of the passage as a whole. The first paragraph identifies the larger question that is the context for the authors’ investigation. The second paragraph presents the part of the question the authors researched, concluding with their unexpected results. The third paragraph explains the importance of these findings in relation to the larger question of the universe’s possible “close.” The authors’ primary purpose in this passage is to summarize the findings of their research.
A. The authors do not discuss approaches to the question they research.
B. The authors mention that their findings do not conform to Kepler’s law, but the passage’s primary focus is on summarizing research findings and not on criticizing any particular view.
C. Correct. This passage presents a summation of the findings of the authors’ research.
D. The authors do not contrast different theories in this passage.
E. The authors do not discuss new techniques in this passage.
The correct answer is C.

Q2. 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
Inference
In the second paragraph, the authors observe that outside the bright nucleus of a typical spiral galaxy luminosity falls off rapidly (lines 20–21); the region just outside the nucleus may thus be characterized as having higher luminosity than the outermost regions of a spiral galaxy. Their research finds that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly (lines 27–30). The region just outside the nucleus may thus be characterized as sharing with the outermost regions of a spiral galaxy a similar rotational velocity.
A. This region was expected to have higher rotational velocity, but the research findings did not corroborate this hypothesis; it is correct that the region has higher luminosity.
B. The region does have higher luminosity, but not lower rotational velocity.
C. The region has neither lower luminosity nor lower rotational velocity.
D. Correct. The region has similar rotational velocity and higher luminosity.
E. The region has similar rotational velocity but higher luminosity.
The correct answer is D.

Q3. 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.
Application
The authors’ conclusion about nonluminous matter is based on their study of the rotational velocity of spiral galaxies. If spiral galaxies were found to be atypical of galaxies, then it would be possible that, in those other galaxies, nonluminous matter does not increase as luminous matter decreases. If this were the case, the authors’ conclusion would be based on a sample of galaxies not representative of the whole, and their argument would be seriously weakened.
A. Correct. The authors’ conclusion assumes that spiral galaxies are typical of all galaxies; information calling that assumption into question weakens the argument.
B. The relation rather than the composition of luminous and nonluminous mass is relevant to the conclusion.
C. Nonluminous mass increases as luminous mass decreases: This finding does not rule out that the nucleus contains some nonluminous mass; the argument is not affected.
D. The density of the observable universe is only a fraction of the density needed to “close” the universe, so even if this density were greater, it is not likely to exceed the density of nonluminous matter.
E. The authors are concerned only with measurable rotational velocity.
The correct answer is A.

Q4. 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.
Inference
An inference is drawn from stated information. This question refers to the first paragraph, where the authors explain that the critical density of matter needed to brake the expansion and “close” the universe is equivalent to three hydrogen atoms per cubic meter (lines 6–9). If the density is significantly less, then the universe will not “close” but continue to expand indefinitely.
A. The authors’ finding that luminosity is not a true indicator of mass is not derived from the conclusion that the density is less than three hydrogen atoms per cubic meter.
B. The authors’ finding that different regions rotate at similar velocities does not come from the hypothesis about the density of the universe.
C. Correct. If the critical density needed to “close” the universe is equivalent to three hydrogen atoms per cubic meter, then a density of significantly less than this amount means that the universe will continue its expansion.
D. This statement would be true of the hypothetical “close” of the universe, but if the density is less than three hydrogen atoms per cubic meter, the universe will continue its expansion.
E. This statement cannot be inferred from the hypothesis about the density of the universe.
The correct answer is C.

Q5. 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
Supporting ideas
This question asks the reader to find the list of possible explanations for the “missing” or dark matter that the authors give in the passage and to check that list against the possible answers. Using the process ofelimination will show which answer is not included on the authors’ list. In the final paragraph, the authors write, 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 (lines 37–40).
A. The authors include massive black holes.
B. The authors include small black holes.
C. The authors include small, dim stars.
D. Correct. The authors do not include massive stars in their list of possible explanations for “missing matter.”
E. The authors include large planets.
The correct answer is D.

GMATNinja | nightblade354 | eakabuah | mira93 | VeritasKarishma | GMATNinjaTwo

On 116, answer choice B

Technically the passage does say ".... Instead we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly.”

Thus, in comparison between outermost regions vs. region just outside the nucleus

Because its possible that rotational velocity increases slightly,

Thus why cant we say rotational velocity of the region just outside the nucleus is going to be lower in comparison to the rotational velocity for the outermost region ( there are 2 possibilities -- either remaining constant or increases slightly)

Q116:

There is some confusion between B and D in terms of velocity, but D is correct as:

B: Similar could mean: 1. same, 2. a little bit more or 3. a little bit less, hence D covers both scenarios stated in the passage, i.e. "slightly Lower velocity" (KEYWORD in the passage in "increases SLIGHTLY") and "same" (Keyword: remains constant).

D covers only one of the 2 scenarios and hence is incorrect.

117. Here's my take on it.

We should treat this as a CR Question:
Conclusion: 90% of the universe is dark matter.
Premise: The study carried out by the author on "Spiral Galaxies"
Assumption: Spiral galaxies are the main type (represent a majority) of the galaxies in the universe.

A. CORRECT: The author's conclusion that 90% of the mass of universe is dark matter is based on studying "spiral galaxies" so if the spiral galaxies represent a minority of the total universe as this choice states, the conclusion falls apart as the assumption no longer holds, hence it weakens the conclusion.

B. Irrespective of what they are made up of they still represent "dark matter".
C. This does not impact the conclusion in any way.
D. The conclusion is about the "composition" of the density not the absolute amount of the density.
E. "Some" may represent a minority of the galaxies and hence this does not challenge the premise/assumption sufficiently.

8 minute 34 seconds including the reading time. All answers correct


The passage is a first person description. Also, the author has described the findings, contradiction with theory, more findings etc.
Therefore, (C) is most suitable


Passage states that the luminous intensity decreases with the increase in distance from the centre. However, contrary to expectations, rotational velocity remains similar or increases.
So moving from outermost region to the region just outside the nucleus, luminosity increases, while rotational velocity remains the same. Therefore, (D)