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

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

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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.


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 : )

Originally posted by kahipz on 05 Nov 2015, 13:59.
Last edited by Bunuel on 17 Dec 2018, 04:30, edited 3 times in total.
Renamed the topic and edited the question.
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Re: Images from ground-based telescopes are invariably distorted by the Ea  [#permalink]

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

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New post 05 Nov 2015, 14:26
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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.

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 Ea  [#permalink]

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New post 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 Ea  [#permalink]

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New post 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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New post 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 Ea  [#permalink]

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New post 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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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 Ea  [#permalink]

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New post 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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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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New post 15 Jan 2017, 08:12
I am still not convinced on answer option E. The Answer option E would be true if the 'telescopes with more light gathering capacity" are "ground based telescopes". Since the answer E does not explicitly specify the same i chose B over E.
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Re: Images from ground-based telescopes are invariably distorted by the Ea  [#permalink]

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New post 15 Jan 2017, 21:18
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LarryM wrote:
I am still not convinced on answer option E. The Answer option E would be true if the 'telescopes with more light gathering capacity" are "ground based telescopes". Since the answer E does not explicitly specify the same i chose B over E.


For a weakening / strengthening type question it not required to satisfy the "must be true" condition - a "could be" scenario would suffice. Option E states a negative point about space telescopes. In this case, highlighting a weakness of the space-based telescope is good enough to qualify the option as the weakening statement. Because of option E, it could be possible that the ground based telescopes would not be obsoleted (IF the ground based telescopes have more light gathering capacity). It is alright to add such conditions for a weakening / strengthening question.

For more explanation about choices B and E, please refer to the following post:

is-this-answer-key-from-og-correct-208210.html#p1715182
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What happens here is that when we automatically see a weaken question we focus on just weakening the conclusion. Its important to understand the connection of why the author ended with his conclusion, in this case, the premise. The statement says: Therefore (conclusion indicator), ground based telescopes will soon become obsolete for advanced astronomical research purposes.

If you only focus on the part of "GB telescopes will soon become obsolete" and based it on the fact that its because of disorted images, then yes, you will fall for trap answer B.

But look more closely, it is saying it will become obsolete for a particular reason (it never says it will become completely obsolete) and that reason is for advanced astronomical research. So we need to look for an answer that states that the GB telescope is still needed for that research and that it has a unique quality that the space telescope does not have. And only answer E states that.
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New post 30 Jul 2017, 07:02
@gmatninja my issue with OA is that even though option E suggests that space telescopes have a drawback and cannot do a certain thing, it does not cast doubt on the argument that ground telescopes might become obsolete. maybe there would be a new kind of telescope/maybe even ground telescopes suck at that thing. We dont know!
is this not a very good quality QG question?
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New post 23 Aug 2017, 07:09
Here's the official explanation for reasoning:

The argument implicitly assumes that advanced astronomical research can be accomplished more effectively with the more
detailed, less distorted images produced by space telescopes and that therefore almost all advanced astronomical research will soon be conducted with space telescopes. This reasoning would be undermined by evidence that ground-based telescopes have substantial advantages for advanced astronomical research despite their distorted images or by evidence that space telescopes will not soon become common or affordable enough to support most advanced astronomical research.

Hope this helps. Thanks.

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

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New post 24 Aug 2017, 15:21
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shrewd1 wrote:
GMATNinja my issue with OA is that even though option E suggests that space telescopes have a drawback and cannot do a certain thing, it does not cast doubt on the argument that ground telescopes might become obsolete. maybe there would be a new kind of telescope/maybe even ground telescopes suck at that thing. We dont know!
is this not a very good quality QG question?

You are right that ground telescopes might still become obsolete, even if (E) is true. However, we do not need an answer that PROVES that ground telescopes will not become obsolete. Rather, we need an answer choice that casts the most doubt on the author's conclusion. Choice (E) directly weakens the author's argument and conclusion, so it is the best answer.
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New post 30 Oct 2017, 18:17
could anyone please explain to me why option D is incorrect?
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New post 01 Nov 2017, 10:32
Can anyone please explain for me why A is not correct? Since it seems like ground-based is much more practical than space telescope.
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New post 05 Nov 2017, 23:22
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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.

oanhsokie wrote:
Can anyone please explain for me why A is not correct? Since it seems like ground-based is much more practical than space telescope.

Choice (A) only talks about two specific telescopes, and that is not enough data to make general statements about the practicality of each technology. Also, just because a space telescope is behind schedule and over budget does not necessarily mean that the technology is impractical or unaffordable. The planners may have underestimated the costs, but that doesn't tell us how the actual costs compare to the actual costs of ground-telescopes. Finally, space telescopes might become more cost-efficient and practical as the technology is developed. Thus, even if space telescopes are less practical now, that does not imply that they won't eventually replace ground-telescopes as costs go down.

csaluja wrote:
could anyone please explain to me why option D is incorrect?

Choice (D) just tells us the best way to use ground-based telescopes. The arrangement described might be better than any other EARTH-BASED arrangement, but if a space telescope is even better than the BEST ground-based setup, then the ground-based telescopes will likely become obsolete.
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