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# Images from ground-based telescopes are invariably distorted by the

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Images from ground-based telescopes are invariably distorted by the [#permalink]

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05 Nov 2015, 13:59
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Images from ground-based telescopes are invariably distorted by the Earth's atmosphere. Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images. Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?

(A) An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

(C) By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

(D) When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

(E) Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

[Reveal] Spoiler:
Answer Key

Two controversial choices (for me)

(B) Ground-based telescopes on mountain summits are still subject to more atmospheric distortion than are space telescopes orbiting above the atmosphere.

(E) CORRECT. This indicates an inherent limitation of space-based telescopes: unlike Earth-based telescopes, they lack the light-gathering capacity that astronomers need to perform one of their primary tasks, i.e., detailed spectral analyses. So Earth-based telescopes are unlikely to soon become obsolete.

[Reveal] Spoiler:
My Reasoning:

My initial answer was (B), and still is. As for answer choice (E), I'm unconvinced because the answer choice doesn't point out unambiguously that Earth-based telescopes have that light-gathering capacity that space-based telescopes fall short, even though the explanation just inexplicably claims that capacity for Earth-based telescopes. As a non-expert in this field, I suppose the test takers aren't supposed to infer that space-based and Earth-based telescopes are only two categories of telescopes in a dichotomy, or that Earth-based telescopes inherently have a better light-gathering capacity that the space-based ones.

As for answer (B), from the viewpoint of a domain illiterate, the reference of "make stars appear to twinkle" doesn't come over as downright inferior and worth being rendered obsolete; the answer actually came over as "The problem with atmospheric distortion becomes abated, to whatever extent, when ground-based telescopes are located on mountain summits; hence, can still be of some use". My choice of (B) over (E) bases primarily on the fact that (E) doesn't explicitly claim for ground-based telescopes the capacity that would make it more useful than space-based ones in that particular regard, while (B) explicitly points out how the weakness of ground-based telescopes can be offset.

Thank you : )
[Reveal] Spoiler: OA

Last edited by abhimahna on 13 Oct 2016, 06:20, edited 1 time in total.
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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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05 Nov 2015, 14:26
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kahipz wrote:
There're several questions, taken from OG Verbal Review 2016, have answer keys whose explanations aren't fully convincing to me. The question below is one in particular. I've provided my reasoning at the end as to why I find the explanations unconvincing. Someone please take a look at point out the flaw in my reasoning. Thanks : )

Question:
Images from ground-based telescopes are invariably distorted by the Earth's atmosphere. Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images. Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?

(A) An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

(C) By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

(D) When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

(E) Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

[Reveal] Spoiler:
Answer Key

Two controversial choices (for me)

(B) Ground-based telescopes on mountain summits are still subject to more atmospheric distortion than are space telescopes orbiting above the atmosphere.

(E) CORRECT. This indicates an inherent limitation of space-based telescopes: unlike Earth-based telescopes, they lack the light-gathering capacity that astronomers need to perform one of their primary tasks, i.e., detailed spectral analyses. So Earth-based telescopes are unlikely to soon become obsolete.

My Reasoning:

My initial answer was (B), and still is. As for answer choice (E), I'm unconvinced because the answer choice doesn't point out unambiguously that Earth-based telescopes have that light-gathering capacity that space-based telescopes fall short, even though the explanation just inexplicably claims that capacity for Earth-based telescopes. As a non-expert in this field, I suppose the test takers aren't supposed to infer that space-based and Earth-based telescopes are only two categories of telescopes in a dichotomy, or that Earth-based telescopes inherently have a better light-gathering capacity that the space-based ones.

As for answer (B), from the viewpoint of a domain illiterate, the reference of "make stars appear to twinkle" doesn't come over as downright inferior and worth being rendered obsolete; the answer actually came over as "The problem with atmospheric distortion becomes abated, to whatever extent, when ground-based telescopes are located on mountain summits; hence, can still be of some use". My choice of (B) over (E) bases primarily on the fact that (E) doesn't explicitly claim for ground-based telescopes the capacity that would make it more useful than space-based ones in that particular regard, while (B) explicitly points out how the weakness of ground-based telescopes can be offset.

Thank you : )

kahipz wrote:
There're several questions, taken from OG Verbal Review 2016, have answer keys whose explanations aren't fully convincing to me. The question below is one in particular. I've provided my reasoning at the end as to why I find the explanations unconvincing. Someone please take a look at point out the flaw in my reasoning. Thanks : )

Question:
Images from ground-based telescopes are invariably distorted by the Earth's atmosphere. Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images. Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?

(A) An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

(C) By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

(D) When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

(E) Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

[Reveal] Spoiler:
Answer Key

Two controversial choices (for me)

(B) Ground-based telescopes on mountain summits are still subject to more atmospheric distortion than are space telescopes orbiting above the atmosphere.

(E) CORRECT. This indicates an inherent limitation of space-based telescopes: unlike Earth-based telescopes, they lack the light-gathering capacity that astronomers need to perform one of their primary tasks, i.e., detailed spectral analyses. So Earth-based telescopes are unlikely to soon become obsolete.

My Reasoning:

My initial answer was (B), and still is. As for answer choice (E), I'm unconvinced because the answer choice doesn't point out unambiguously that Earth-based telescopes have that light-gathering capacity that space-based telescopes fall short, even though the explanation just inexplicably claims that capacity for Earth-based telescopes. As a non-expert in this field, I suppose the test takers aren't supposed to infer that space-based and Earth-based telescopes are only two categories of telescopes in a dichotomy, or that Earth-based telescopes inherently have a better light-gathering capacity that the space-based ones.

As for answer (B), from the viewpoint of a domain illiterate, the reference of "make stars appear to twinkle" doesn't come over as downright inferior and worth being rendered obsolete; the answer actually came over as "The problem with atmospheric distortion becomes abated, to whatever extent, when ground-based telescopes are located on mountain summits; hence, can still be of some use". My choice of (B) over (E) bases primarily on the fact that (E) doesn't explicitly claim for ground-based telescopes the capacity that would make it more useful than space-based ones in that particular regard, while (B) explicitly points out how the weakness of ground-based telescopes can be offset.

Thank you : )

Choice B is talking about a particular kind of ground based telescope.(Ground based telescope located on mountains) You dont know how much percentage of Ground based telescope constitute those that are located on the mountains.

I think you are assuming that in near future, all the Ground based telescopes can be migrated to the mountains and hence can be useful. The option does not tell you this.

Also note that, if Space based telescope are already there which can carry out this functionality without any problems that ground based telescope may face, then why will the Ground based telescope be used if same functionality can be achieved by the space based ones .

See to weaken the conclusion, we need to show something that Ground based telescope can do but space based ones cannot, so there will be a reason to use ground based telescope as you cannot achieve that functionality using the space based.

Choice E precisely does that.

It states that Space based telescope may not be useful for analyzing chemical composition of stars .So it presents one drawback for space based telescope.

This functionality can be provided (we are not sure whether ground based can provide this functionality, but still there is a chance) by ground based telescope. So it weakens the conclusion.

We do not need to falsify a conclusion. Any choice that casts some doubt on the conclusion can be a valid Weakener

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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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05 Nov 2015, 20:24
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Images from ground-based telescopes are invariably distorted by the Earth's atmosphere. Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images. Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?

(A) An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

(C) By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

(D) When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

(E) Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

The question says that ground-based telescope will soon become obsolete. The premise supporting this conclusion is "Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images."

To weaken this conclusion, we need to find any attribute of ground-based telescopes that is still advantageous and that use keeps it in astronomical research.

Option E does that, as this describes the fact that Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, can't be done with space telescopes as they don't have light gathering capacity.

Option B is out of consideration. It talks about possible location where it can work or where it can't work.

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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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08 Nov 2015, 06:18
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Dear Kahipz,

Answer choice B is incorrect.

Your thinking is partially correct:

"The problem with atmospheric distortion becomes abated, to whatever extent, when ground-based telescopes are located on mountain summits; hence, can still be of some use"

But did you went back to argument (specially try to correlate with point 2 below), which suggest that:

1. Images from ground-based telescopes are invariably distorted by the Earth's atmosphere

2. Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images

Well, if you correlate the answer choice B with point number 02 above, you would certainly be unable to answer question why "Ground based telescopes are worse than orbiting space telescopes"

Answer choice literally means:

"Ground based telescopes are better when operated at the mountains as compared to when operated at ground"

Hope it helps.

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18 Nov 2015, 23:31
Thanks all for your helps.

As I practise more on CR, I start to develop an inkling as to why E is chosen instead of B, even though, reasoning-wise, I'm still not settled. I'd like to ask one more question though. About the wrong answer choice B, which category of incorrect answer would it fall into? Is it Out of Scope?

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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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20 Nov 2015, 02:51
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kahipz wrote:
As I practise more on CR, I start to develop an inkling as to why E is chosen instead of B, even though, reasoning-wise, I'm still not settled.
The response just above yours is a very good one.

Everything A is distorted by the atmosphere. Everything B operates outside the atmosphere. Therefore for advanced research, everything A will become obsolete. The second option is just saying that some As are better than other As. But the larger point is that any B is better than an A. The fact that some As are better than other As can't change that.
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12 Dec 2015, 14:00
I went with B too.

I feel it's better than E because the conclusion is 'Ground-based telescopes will soon become obsolete because of a certain drawback which can be overcome by using space telescopes.'

B counters the 'obsolete' argument.

E - gives a reason to believe that telescopes with more light-gathering capacity are better.

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01 May 2016, 22:22
The point here is that no person above giving explanations prove that Ground telescopes are the ones that have more light-gathering capacity than the ones those are above Earth's atmosphere.

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option E is ambiguous. IMO B
Lets say Ground telescopes- X
Space telescopes- Y
Light gathering telescopes- Z

Option E says Z is superior to Y but that doesn't support the cause for X not to be obsolete. If Z= X then E is true, but nowhere it is mentioned so.

Atleast option B says X cant be obsolete as they can be useful in some locations

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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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09 Jul 2016, 23:33
I narrowed down to options D and E, but not able to differentiate between both options.

D also mentions Large aperture based telescopes near equator provide best images of center of milky-way and "Astronomical research" as a keyword.
So why not its D??

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10 Jul 2016, 19:24
AJ1012 wrote:
D also mentions Large aperture based telescopes near equator provide best images of center of milky-way
D doesn't say that those telescopes provide the best possible images.

Quote:
they permit the best Earth-based observations

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25 Jul 2016, 23:37
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Really not able to convince how option E is the correct answer.

we need to assume more to chose this.

Experts please help, why 'B' is wrong
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26 Jul 2016, 17:06
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smartguy595 wrote:
Really not able to convince how option E is the correct answer.

we need to assume more to chose this.

Experts please help, why 'B' is wrong

The conclusion is about a causal relation:

Space telescopes are better in one feature, and HENCE they will make earth telescopes obsolete.

Stating a negative feature of the space telescopes attacks this causal relation (though it may not directly attack the possibility that earth telescope will be obsoleted). Because space telescopes has a negative feature they will NOT be able to make the earth satellites obsolete.

If one considers "ground-based telescopes will soon become obsolete" the conclusion then your point is definitely valid. But if one considers "Superior feature of space telescope will cause ground-based telescopes to be obsolete", then option E is correct. In GMAT this causal relation as a conclusion is often tested.

For the same reason stated above option B is wrong. It does not attack the causal relation, but only supports why earth based telescopes may not be obsoleted. (Moreover, the condition that was used to prove that Space telescopes will replace earth telescopes, still holds good - even after mounting the telescopes on higher grounds, the distortion will not be eliminated, and hence the space telescopes still remain better of the two - nonetheless, this does not play any role in attacking the causal relation.)

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Images from ground-based telescopes are invariably distorted by the Earth's atmosphere. Orbiting space telescopes, however, operating above Earth's atmosphere, should provide superbly detailed images. Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?

(A) An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

(C) By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

(D) When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

(E) Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.
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05 Oct 2016, 06:00
Images from ground based telescopes are distored by Earth Atmosphere

Oribiting Telescopes gives detailed images

Conclusion : No use for Ground Based Telescopes in Adv Research purposes

Question : Weakener

If there are some areas in which space Telescopes are not useful

that will act as a weakner

Answer E

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The argument states that -
Orbiting telescopes provide more detailed images --> obsolescence of ground based telescopes for advanced astronomical research.

A - if one orbiting telescope exceeded its budget, does not mean that all such telescopes in the future will exceed their budgets. Also, what about other ground based telescopes? were they both within budget and on schedule?. Additionally, if orbiting telescopes are significantly cheaper than ground based telescopes, then this strengthens the argument.
B - but still they are in the atmospheric zone and are subject to at least some atmospheric distortions.
C - What about other distortions from the atmosphere?
D - "best earth based" is still not better than "space based".
E - Correct answer. Tells us about an important advantage that ground based telescopes have over space based telescopes, suggesting they might not get obsolete.
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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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09 Oct 2016, 11:11
sayantanc2k wrote:
smartguy595 wrote:
Really not able to convince how option E is the correct answer.

we need to assume more to chose this.

Experts please help, why 'B' is wrong

The conclusion is about a causal relation:

Space telescopes are better in one feature, and HENCE they will make earth telescopes obsolete.

Stating a negative feature of the space telescopes attacks this causal relation (though it may not directly attack the possibility that earth telescope will be obsoleted). Because space telescopes has a negative feature they will NOT be able to make the earth satellites obsolete.

If one considers "ground-based telescopes will soon become obsolete" the conclusion then your point is definitely valid. But if one considers "Superior feature of space telescope will cause ground-based telescopes to be obsolete", then option E is correct. In GMAT this causal relation as a conclusion is often tested.

For the same reason stated above option B is wrong. It does not attack the causal relation, but only supports why earth based telescopes may not be obsoleted. (Moreover, the condition that was used to prove that Space telescopes will replace earth telescopes, still holds good - even after mounting the telescopes on higher grounds, the distortion will not be eliminated, and hence the space telescopes still remain better of the two - nonetheless, this does not play any role in attacking the causal relation.)

Hi sayantanc2k,

I am back with a dumb query

Option E states below:

Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

So do we assume that they are talking about ground based telescopes? Since they don't mention that feature in the argument nor is the option specifically stating that these telescopes are ground based telescopes.

Also, unwillingly I chose C because I was under the impression that telescopes will become obsolete due to bad image quality and option C talks about image quality. I know I am assuming ground based telescopes to be large aperture telescopes but our objective is achieved with careful placement and hence these telescopes won't be obsolete.

Can you help me understand better? Is it ok to choose generalized statements when question stem lists particular type. More so in questions wherein terms are difficult to interpret?

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Re: Images from ground-based telescopes are invariably distorted by the [#permalink]

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13 Oct 2016, 05:45
Hi Experts
I have a question.
The answer for choice B is :
(B) Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

In my Opinion, this answer choice completely contradict the evidence in the argument that:
"Images from ground-based telescopes are invariably distorted by the Earth's atmosphere"

The explanation in the OG Verbal review 2016 says:
"B Ground-based telescopes on mountain summits are still subject to more
atmospheric distortion
than are space telescopes orbiting above the
atmosphere."

From E-gmat, a weaken question must provide new information and answer B provides new information although it contradicts an evidence in the argument. Why the OG explanation above says "are still subject to more atmospheric distortion"? knowing that if you take choice B it contradicts and remove the fact that there is distortion for ground based telescope.

Thank you in advance for answering

Teo

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Images from ground-based telescopes are invariably distorted by the [#permalink]

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28 Oct 2016, 09:15
Hello Experts,

What if the light gathering capacity of ground based telescope is less than that of the space based telescope. We have no way to verify this based on the argument. If my assumption is true, then ground based telescopes will be obsolete.
Maybe astronomers are currently using space based telescopes instead of ground based telescopes because they have a superior light gathering ability( the argument says that their light gathering ability is not good but it doesn't say that other telescopes have better ability than space based one's, maybe spaces based one's have the best ability) . Again, we have no way to verify.
I agree that none of the other options weaken the statement.

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28 Oct 2016, 09:50
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warriorguy wrote:
sayantanc2k wrote:
smartguy595 wrote:
Really not able to convince how option E is the correct answer.

we need to assume more to chose this.

Experts please help, why 'B' is wrong

The conclusion is about a causal relation:

Space telescopes are better in one feature, and HENCE they will make earth telescopes obsolete.

Stating a negative feature of the space telescopes attacks this causal relation (though it may not directly attack the possibility that earth telescope will be obsoleted). Because space telescopes has a negative feature they will NOT be able to make the earth satellites obsolete.

If one considers "ground-based telescopes will soon become obsolete" the conclusion then your point is definitely valid. But if one considers "Superior feature of space telescope will cause ground-based telescopes to be obsolete", then option E is correct. In GMAT this causal relation as a conclusion is often tested.

For the same reason stated above option B is wrong. It does not attack the causal relation, but only supports why earth based telescopes may not be obsoleted. (Moreover, the condition that was used to prove that Space telescopes will replace earth telescopes, still holds good - even after mounting the telescopes on higher grounds, the distortion will not be eliminated, and hence the space telescopes still remain better of the two - nonetheless, this does not play any role in attacking the causal relation.)

Hi sayantanc2k,

I am back with a dumb query

Option E states below:

Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

So do we assume that they are talking about ground based telescopes? Since they don't mention that feature in the argument nor is the option specifically stating that these telescopes are ground based telescopes.

Also, unwillingly I chose C because I was under the impression that telescopes will become obsolete due to bad image quality and option C talks about image quality. I know I am assuming ground based telescopes to be large aperture telescopes but our objective is achieved with careful placement and hence these telescopes won't be obsolete.

Can you help me understand better? Is it ok to choose generalized statements when question stem lists particular type. More so in questions wherein terms are difficult to interpret?

sveniga4 wrote:
Hello Experts,

What if the light gathering capacity of ground based telescope is less than that of the space based telescope. We have no way to verify this based on the argument. If my assumption is true, then ground based telescopes will be obsolete.
Maybe astronomers are currently using space based telescopes instead of ground based telescopes because they have a superior light gathering ability( the argument says that their light gathering ability is not good but it doesn't say that other telescopes have better ability than space based one's, maybe spaces based one's have the best ability) . Again, we have no way to verify.
I agree that none of the other options weaken the statement.

Say,

X = space satellite
Y = ground based satellite
function A = taking images
function B = spectral analysis

Conclusion: X will replace Y because X is superior than Y in function A.

Option E: X is not capable of executing function B. So in order to execute B, Y will still be required and hence Y will not be obsoleted... E is definitely a weakener.

Option B and C : Some of the Y's are not as bad in executing function A as the other Y's. This is not as strong a weakening statement as option E.

Option E in a way confirms that Y would not be obsoleted, but option B does not confirm.

Kudos [?]: 3515 [0], given: 22

Images from ground-based telescopes are invariably distorted by the   [#permalink] 28 Oct 2016, 09:50

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