In addition to conventional galaxies, the universe contains

Thank you for the insight. But, don't you think that if i reattempt, its going to be right because , may be, i would remember the answer and explanation. I hope when you say reattempting, it is reattempting after a few days . Cool, i will try to do this and see how it works . Thank you again for the quick response

What is the level of this RC passage? Can anyone tell me

Hello PallabiKundu

What I have understand is that you are asking for the difficulty level of the questions. Below it is.

Question #1: 550
Question #2: 600
Question #3: 550
Question #4: 600
Question #5: 650
Question #6: 650
Question #7: 600

Overall: 600

I have a general question about the passage.

"Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect."

What's the point of saying "have long speculated" here?

As far as I understood:
- Dim galaxies are one of the two possible explanations of the missing baryonic mass (the other explanation is that missing baryonic mass is in intergalactic space).

Shouldn't we say just "Astronomers speculate"? Or in the worst case scenario, "Astronomers have speculated" (without "long")?

Additionally, the passage is in present tense, therefore I see no reason to use present perfect (have speculated).

Thanks.

Their speculation started a long ago and it is still going on.
have long speculated is correct here


Dim galaxies are one of the two possible explanations of the missing baryonic mass (the other explanation is that missing baryonic mass is in intergalactic space).- WRONG
Dim galaxies are one of the two possible SOURCE of the missing baryonic mass (the other source is that missing baryonic mass is in intergalactic space).

Dear Experts,

GMATNinja
VeritasKarishma
AjiteshArun

In Q6., I got hesitated in choice B,



According to the passage,


Why author would agree with choice(B) with the word "OFTEN"?
Since I cannot see any mentions of the likelihood of galaxy shapes.

How can I eliminate it with confidence?

Appreciate,
-tor

Hi TorGmatGod,

The correct answer will be something that the author is (most) likely to disagree with. In the portion of the passage you're looking at, the author clearly says "these galaxies have the same general shape... as a common type of conventional galaxy, the spiral". This means that ~ low-surface-brightness galaxies are spiral in shape. The only difference between what we see in the passage and what option B says is that option B includes the word often.

(1) Low-surface-brightness galaxies are spiral in shape. ← This is what the passage tells us.
(2) Low-surface-brightness galaxies are often spiral in shape. ← This is option B.

Someone who agrees with (1) will most likely also agree with (2). If it helps, we can read B as "many low-surface-brightness galaxies are spiral in shape". If all low-surface-brightness galaxies are spiral in shape, then the statement "many low-surface-brightness galaxies are spiral in shape" is also true, so the author is unlikely to disagree with it. On the other hand, the author would definitely disagree with E, because he or she says that the missing baryonic mass "might eventually be discovered in intergalactic space".

"same general shape" and "often have the same shape" are not very different.
"Same general shape" means that most have this shape but there could be some exceptions. "Often have the same shape" is also the same idea. When you are talking about galaxies, there is a lot we don't know. So making definitive statements is not possible.

Adding a data point to help others gauge their performance:
9:08 minutes to read and answer all 7 questions. I got 6/7 correct
English as a second language

AjiteshArun
Thanks for the nice explanation, but it confused a bit me.

It seems that Low-surface-brightness galaxies is same as dim galaxies, right? From the above quote, the conventional galaxy is the spiral as the spiral has been used as the modifier of conventional galaxy. So, from the quote, it seems that conventional galaxy (not Low-surface-brightness galaxies/ dim galaxies) are spiral in shape.
Am I missing anything here?
Thank you very much.

Hi TheUltimateWinner,

Let's look at that part of the passage again:

This is where the author tells us that very dim galaxies have the same general shape as spiral galaxies do.

Paraphrasing:
Passage pattern: introducing & explaining a phenomenon, with its benefits (answer 7)

Introduction: Conventional galaxies vs dim galaxies
Dim galaxies are
1. Recently went unnoticed by astronomers
2. Have same structure as conventional galaxies
3. Are spiral but tends to be much larger size than conventional galaxies (answer 2)
4. Mass spread out in larger area than conventional galaxies
5. Fewer star per unit volume
6. Low-surface brightness galaxies
7. Evolves slowly than conventional galaxies (answer 1)

Baryons numbers (mass)
1. can be estimated based on how luminous galaxies are.
2. baryons are the source of galactic luminosity (answer 5)
3. Answer to missing baryonic mass in universe (answer 4)
4. The amount of helium in the universe suggests that there are far more baryons in the universe – (answer 3)

Benefits of finding Baryonic mass:
might eventually be discovered in intergalactic space or
as some large population of galaxies that are difficult to detect.

Hi Experts,
KarishmaB GMATNinja

I was confused btw D & E in Q96.
96. The author of the passage would be most likely to disagree with which of the following statements?
(D) Astronomers have devised a useful way of estimating the total baryonic mass in the universe.
(E) Astronomers have discovered a substantial amount of baryonic mass in intergalactic space.

"Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect"
From these 2 lines, we can infer that Astronomers might discover baryonic mass in future. So author doesn't completely disagree with the idea that baryonic mass can be discovered or would have been discovered. Author has shared hints about the discovery in a positive way.
The reason I rejected D bcz author didn't share any perspective on devising a useful way of estimating baryonic mass. We don't know author's perspective regarding this new way.

95. The author mentions the fact that baryons are the source of stars’ luminosity primarily in order to explain
(E) how astronomers know bright galaxies contain more baryons than do dim galaxies
Why E is incorrect?

Based on luminosity, we can calculate no of baryons. So astronomers can say bright galaxies will have more no. of baryons compared to dim. Why E is incorrect then?

Thank you very much.

Hi Sneha2021,

Let's take a look at some of the important words in that part of the passage.

Option E tells us that astronomers have (already) discovered a substantial amount of baryonic mass in intergalactic space. If they've already discovered so much baryonic mass in intergalactic space, why are they still speculating that intergalactic space would be a good place to go looking for the missing baryonic mass? The passage certainly doesn't tell us that they've already found lots of baryonic mass there and now want to look for even more, so it's more likely that they haven't found any (or much) baryonic mass in intergalactic space yet, and that's why they think intergalactic space may where the missing baryonic mass is. Even the second candidate ("some large population of galaxies that are difficult to detect") is something that we wouldn't expect astronomers to already know a great deal about.

Question 6 (or 96)

Starting with (E):

The words "have discovered" very specifically tell us that astronomers already discovered a substantial amount of baryonic mass in intergalactic space. The last line of the passage tells us that astronomers have speculated that this mass exists, but nothing indicates that it has already been discovered, as written in (E).

Additionally, the same line discusses two possible answers to the long-standing puzzle of extra mass: matter in intergalactic space, or extra galaxies that are difficult to detect.

The passage provides ample support for the second answer: these difficult-to-detect galaxies HAVE been detected. They may well account for the entirety of the missing mass. By contrast, the author doesn't provide any evidence to support the idea that there is a substantial amount of baryonic mass in intergalactic space.

The author would disagree that astronomers have discovered a substantial amount of baryonic mass in intergalactic space, so (E) is the correct answer.

Here's (D):

The author discusses two ways of estimating baryonic mass: luminosity, and "the amount of helium in the universe, as measured by spectroscopy." This second method is used to estimate the total baryonic mass in the universe, so that's the method (D) is talking about.

There is a gap between the two measures -- the measured luminosity of galaxies is low compared to measured amount of helium. From this, the author says that there is "missing" matter. This means that the author trusts the higher number given by the helium method, and is searching for a reason to explain why the luminosity is lower than it should be.

Because the author trusts the helium method of measuring the total baryonic mass in the universe, the author would agree with (D).

(D) is out.

Question 5 (or 95)

Here's the exact wording of question 5:

To answer this question, we're not just looking for something that's true about the "fact." We're looking for the primary reason WHY the author included the fact in the passage. What role does it play in the author's overall point?

In the second paragraph, the author talks about a "long-standing puzzle" : there is "missing" baryonic mass in the universe. We know about this missing mass because of a gap between two different ways to measure baryonic mass -- helium and luminosity.

So, the author mentions the fact that baryons are the source of stars’ luminosity to connect these dots. That's a great fit with (C):

(C) is the correct answer to question 5.

Here's (E):

Again, when the author mentions the "fact," he/she is primarily trying to show how luminosity plays into the puzzle of the missing mass. He/she is not concerned with comparing the masses of different types of galaxies.

Additionally, the author would not agree that dim galaxies have fewer baryons than bright galaxies do -- in fact, we know from the first paragraph that they have the "same approximate number of stars as a common type of conventional galaxy." It's just that dim galaxies are more spread out, making it tough to detect the luminosity of those galaxies. In other words, the luminosity measure was off because it failed to detect the baryons in the dim galaxies.

Eliminate (E) for question 5.

I hope that helps!

ThatDudeKnows why not E in the primary purpose. Isn’t the last para talking about a situation that shows there are more baryons and this is inconsistent with the situation that these galaxies can help account for Missing baryons avigutman

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Can you elaborate on how the above qualifies as an inconsistency please, Elite097? I’m not seeing it unfortunately.

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