Dark matter and dark energy have both been postulated by astrophysicis

Question

Dark matter and dark energy have both been postulated by astrophysicists to fill a gap in the fabric of the cosmos which is known as the puzzle of the missing mass. In doing so, astrophysicists sought to bring the characteristics of the universe better in line with Einsteins Theory of Relativity, which predicts that the density of the universe is about 25 times greater than has been heretofore observed. Only 4% of the universe is thought to be composed of conventional matter and energy; about 22% is thought to be composed of dark matter and the remaining 74% is thought to be dark energy. Dark matter does not interact with conventional matter or energy by electromagnetic forces and thus its presence cannot be detected directly. The presence of dark matter must be inferred through its indirect manifestations: anomalous gravitational effects, the rotational velocity data of stars in spiral galaxies and the unusual distribution of mass in a star system known as the Bullet Cluster. Although dark matter was conclusively detected through its gravitational lensing effect in August 2006, many aspects of dark matter remain speculative. It has been noted that the terms dark matter and dark energyserve mainly as expressions of human ignorance, much like the marking of early maps with terra incognita.   1 
 C 
1. Which of the following best expresses the central idea of the passage?
(A) Dark matter and dark energy can be directly identified.
(B) Astrophysicists are ignorant of many important details of the universes composition.
(C) Although not well understood, dark matter and dark energy help reconcile theory with observation.
(D) Despite a recent observation, the existence of dark matter and dark energy is still debated in the scientific community.
(E) Dark matter and dark energy were suggested by Einsteins Theory of Relativity.

2 
 A 
2. According to the passage, each of the following is true of dark matter or dark energy EXCEPT:
(A) They explain why the universe may be 25 times denser than has been observed.
(B) They are thought to account for 96% of the universe.
(C) They are not well understood by physicists.
(D) Their existence can be deduced from observations such as unexpected mass distributions.
(E) They may solve the puzzle of the missing mass.

3 
 D 
3. The passage suggests which of the following about anomalous gravitational effects?
(A) The Theory of Relativity does not adequately account for them.
(B) Their appearance is not understood by physicists.
(C) They may explain the puzzle of the missing mass.
(D) Without the existence of dark matter, they cannot be satisfactorily explained.
(E) They are related to the distribution of mass in the Bullet Cluster.

Source: GMAT Hacks

Nikhil · Accepted Answer

1. Which of the following best expresses the central idea of the passage?

(A) Dark matter and dark energy can be directly identified.

INCORRECT  Out of scope. The identification process of dark energy is not mentioned in the passage while identification of dark matter through direct or indirect methods is mentioned.

(B) Astrophysicists are ignorant of many important details of the universes composition.

INCORRECT  Human ignorance is mentioned in the last sentence of the passage but there is no mention of astrophysicists ignorance.

(C) Although not well understood, dark matter and dark energy help reconcile theory with observation.

Correct  Astrophysicists postulate dark matter and dark energy to fill a gap. The dark matter and dark energy are not easily detected. This expresses the central idea of the passage.

(D) Despite a recent observation, the existence of dark matter and dark energy is still debated in the scientific community.

INCORRECT  There is no mention of any "recent observation" in the passage. The passage doesn't mention any debate around the existence of dark matter and dark energy

(E) Dark matter and dark energy were suggested by Einsteins Theory of Relativity.

INCORRECT  Dark matter and dark energy were suggested by astrophysicists and not Einstein.

2. According to the passage, each of the following is true of dark matter or dark energy EXCEPT:

(A) They explain why the universe may be 25 times denser than has been observed.

Correct  Theory of Relativity predicts that the density of the universe is about 25 times greater. There is no mention of dark matter or dark energy explanining the reason for this density.

(B) They are thought to account for 96% of the universe.

INCORRECT  This option is true based on "about 22% is thought to be composed of dark matter and the remaining 74% is thought to be dark energy"

(C) They are not well understood by physicists.

INCORRECT  This option is true in saying many aspects of dark matter and dark energy are not well understood. The passage does mention many aspects of dark matter remain speculative.

(D) Their existence can be deduced from observations such as unexpected mass distributions.

INCORRECT  This is stated in the passage. "The presence of dark matter must be inferred through its indirect manifestations: the unusual distribution of mass in a star system known as the Bullet Cluster."

(E) They may solve the puzzle of the missing mass.

INCORRECT  This is mentioned in the first line of the passage. "Dark matter and dark energy have both been postulated by astrophysicists to fill a gap in the fabric of the cosmos which is known as the puzzle of the missing mass."

3. The passage suggests which of the following about anomalous gravitational effects?

(A) The Theory of Relativity does not adequately account for them.

INCORRECT  The passage doesn't specify any relation between Theory of Relativity and anomalous gravitational effects. They are mentioned in the passage in different contexts.

(B) Their appearance is not understood by physicists.

INCORRECT  Their appearance is understood by physicists and linked to the presence of dark matter.

(C) They may explain the puzzle of the missing mass.

INCORRECT  They may explain the dark matter and not the puzzle of missing mass.

(D) Without the existence of dark matter, they cannot be satisfactorily explained.

Correct  The anomalous gravitational effects have been linked to the presence of dark matter. WIthout the existence of dark matter, they cannot be satisfactorily explained.

(E) They are related to the distribution of mass in the Bullet Cluster.

INCORRECT  The anomalous gravitational effect and the Bullet Cluster are not linked to each other. They both help explain the presence of dar matter.

Sreyoshi007 · Answer

Main idea of the passage is that dark matter and dark energy are used by physicists to better explain missing mass. We can understand this in the following line
 
Plus we are told that dark matter and dark energy is not very well understood.
Hence  option C  is the correct answer.

This was a tricky one but if we go by process of elimination we can arrive at the answer properly;
Starting with option E,
Yes, we are told in the passage that dark matter and energy  may  solve the puzzle of missing mass.
Eliminate E.

Lets see D,
Correct, the passage mentions that the existence of dark matter and energy can be deduced from observations such as unexpected mass distributions. Safe to eliminate D.

Moving on to C,
The passage does mention that physicists do not understand Dark matter and energy very clearly yet. Eliminate C.

In B, the lines tell that 96% of the universe is dark matter and energy. Eliminate B.

Hence we are left with  A, which is the correct answer . We are not told that dark matter and energy explain why the universe may be 25 times denser than has been observed. Rather, it  may  help explain.

Refer to the following lines in the passage ;
 
Hence  option D  is the right answer.

Thanks and do press kudos if this helped!

dvishal387 · Answer

The author explains how dark matter and dark energy are used to explain things which humans are ignorant of.
1. The main point is contained in the last sentence of the passage where it is stated that - "..terms dark matter and dark energyserve mainly as expressions of human ignorance" but help to arrive at conclusions through theories presented in before in the passage.
So C is the correct choice.
2. Theory of Relativity predicted the mentioned statement in A and it was no explained by dark matter or dark energy. So A is the correct choice.
3. he line - "The presence of dark matter must be inferred through its indirect manifestations: anomalous gravitational effects, the rotational velocity data of stars in spiral galaxies and the unusual distribution of mass in a star system known as the Bullet Cluster" suggests dark matter helps in satisfactorily explaining the anomalous gravitational effects, hence D is the correct choice.

abhishekdadarwal2009 · Answer

3. The passage suggests which of the following about anomalous gravitational effects?
(A) The Theory of Relativity does not adequately account for them.
(B) Their appearance is not understood by physicists.
(C) They may explain the puzzle of the missing mass.
(D) Without the existence of dark matter, they cannot be satisfactorily explained.
(E) They are related to the distribution of mass in the Bullet Cluster.

Refer to the following lines in the passage ;
Quote:
The presence of dark matter must be inferred through its indirect manifestations: anomalous gravitational effects, the rotational velocity data of stars in spiral galaxies and the unusual distribution of mass in a star system known as the Bullet Cluster.

How can D be the correct answer, the passage says that the dark matter can be inferred by the

1. anomalous gravitational effects,
2. the rotational velocity data of stars in spiral galaxies and 
3. the unusual distribution of mass

there is no indication that the reverse is also true, ie anomalous gravitational effects can be explained by dark matter.

honneeey · Answer

Hi, I understand the confusion here ! The passage says that "The presence of dark matter must be inferred through its indirect manifestations: anomalous gravitational effects..." What does "its" point to? It points towards "Presence of dark matter". Now sentence says," Presence of dark matter must be inferred thru ITS indirect manifestations" It means "Presence of dark matter's indirect manifestations"-Possessive noun. Therefore, Logical sequence that can be drawn is - Presence of dark matter-->Indirect Manifestations(anomalous gravitational effects) Eventually, it can be said that "Without the existence of dark matter, they(indirect manifestations) cannot be satisfactorily explained." Hope it helped. Kudos if I helped!

AntrikshR · Answer

Hello,

The way i understood "The presence of dark matter must be inferred through its indirect manifestations: anomalous gravitational effects.." is "Anomalous Gravitation Effects, rotational velocity etc. are necessary to infer the presence of dark matter"-----> Necessary Condition is given.
X (A.G.E,Rotational velocity etc) ----->Y (Presence of dark matter)

Now, Option D says "Without the existence of dark matter, they cannot be satisfactorily explained"
==> Not Y---> Not X, which is correct in case of necessary conditions. 
This essentially means, if dark matter doesn't exists then certainly A.G.E can't be explained.
Hence, option D is correct.

richirish · Answer

Easy passage overall, 3 mins to solve all questions,  SajjadAhmad , please share difficulty levels and source

Sajjad1994 · Answer

Source is GMAT Hacks and the difficulty levels are as follow:

Question #1: 650
Question #2: 700
Question #3: 700

Regards

VerbalBot · Answer

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Dark matter and dark energy have both been postulated by astrophysicis

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Dark matter and dark energy have both been postulated by astrophysicis

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