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

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

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New post 03 Apr 2018, 09:38
Sorry experts I just don't understand how E is the correct answer:

It just says that for more detailed studies astronomers should use telescopes with more light-gathering capacity than space telescopes can provide......... NO ONE SAYS THAT GROUND-BASED TELESCOPES CAN PROVIDE THAT CAPACITY, CHOOSING ANSWER E I HAVE TO MAKE AN IMPORTANT ASSUMPTION THAT IS NOT SPECIFIED ANYWHERE IN THE TEXT....
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Re: Images from ground-based telescopes are invariably distorted by the Ea  [#permalink]

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New post 03 Apr 2018, 17:56
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Fedemaravilla wrote:
Sorry experts I just don't understand how E is the correct answer:

It just says that for more detailed studies astronomers should use telescopes with more light-gathering capacity than space telescopes can provide......... NO ONE SAYS THAT GROUND-BASED TELESCOPES CAN PROVIDE THAT CAPACITY, CHOOSING ANSWER E I HAVE TO MAKE AN IMPORTANT ASSUMPTION THAT IS NOT SPECIFIED ANYWHERE IN THE TEXT....
Let's put some of the information given in the stimulus and in option E down:

1. Astronomers rely on DSA. This means that astronomers are already using DSA to determine the chemical composition and evolutionary history of stars.
2. Space telescopes cannot provide DSA; DSA can be provided only by telescopes with more light-gathering capacity than space telescopes can provide. So DSA needs non-space telescopes.

Because astronomers are already using DSA, and space telescopes can't do DSA, astronomers must be using telescopes that are not space telescopes. Such telescopes must be terrestrial (the opposite of space). Hence E is quite solid as an answer choice.

More generally, you'll find that the correct option does very often involve a "stretch". The GMAT doesn't say how much of a stretch is too much, but a little bit is okay. It'd be very hard to make a compact CR question if the question makers could not take certain things for granted. In this case, as soon as we see that E gives us a weakness (of space telescopes), we should be seriously considering it as a "candidate" option.
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Re: Images from ground-based telescopes are invariably distorted by the Ea  [#permalink]

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New post 08 Apr 2018, 17:29
AjiteshArun wrote:
Fedemaravilla wrote:
Sorry experts I just don't understand how E is the correct answer:

It just says that for more detailed studies astronomers should use telescopes with more light-gathering capacity than space telescopes can provide......... NO ONE SAYS THAT GROUND-BASED TELESCOPES CAN PROVIDE THAT CAPACITY, CHOOSING ANSWER E I HAVE TO MAKE AN IMPORTANT ASSUMPTION THAT IS NOT SPECIFIED ANYWHERE IN THE TEXT....
Let's put some of the information given in the stimulus and in option E down:

1. Astronomers rely on DSA. This means that astronomers are already using DSA to determine the chemical composition and evolutionary history of stars.
2. Space telescopes cannot provide DSA; DSA can be provided only by telescopes with more light-gathering capacity than space telescopes can provide. So DSA needs non-space telescopes.

Because astronomers are already using DSA, and space telescopes can't do DSA, astronomers must be using telescopes that are not space telescopes. Such telescopes must be terrestrial (the opposite of space). Hence E is quite solid as an answer choice.

More generally, you'll find that the correct option does very often involve a "stretch". The GMAT doesn't say how much of a stretch is too much, but a little bit is okay. It'd be very hard to make a compact CR question if the question makers could not take certain things for granted. In this case, as soon as we see that E gives us a weakness (of space telescopes), we should be seriously considering it as a "candidate" option.

AjiteshArun, thanks for the great response!

The other key to this question is that we are looking for something that "would cast the most doubt on the conclusion drawn above."

So we just need something that would make us question the author's logic/conclusion. The author says that space telescopes should provide superbly detailed images. Therefore, ground telescopes will soon become obsolete. In reaching the conclusion, the author is only considering image quality.

Choice (E) says, "You (author) might be right about image quality, but you haven't considered DSA." So even if we don't know that ground telescopes have the capacity needed for DSA, we already have a reason to doubt the author's logic. The author was ONLY considering image quality and failed to consider DSA.

As explained perfectly by AjiteshArun, it is very reasonable to suspect that ground telescopes have such capacity. However, even without knowing that for sure, we've already poked a hole in the author's argument. That doesn't necessarily PROVE that the author is wrong, but it certainly casts doubt on the argument/conclusion.

None of the other answer choices affect the author's argument, so (E) is definitely the best answer.
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Re: Images from ground-based telescopes are invariably distorted by the Ea  [#permalink]

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New post 29 Nov 2018, 16:07
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kahipz wrote:
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.


A student asked me to respond to this question, so . . .

1) Read question stem to determine question type.
Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?
We have a Weaken the Argument question.

2) Read passage and summarize premises and the conclusion.
PREMISE: Images from GBTs (ground-based telescopes) distorted by atmosphere
PREMISE: Space telescopes above atmosphere should make detailed images
CONCLUSION: GBTs to become obsolete for advanced research

3) Check the answer choices while reminding yourself of the CONCLUSION.

(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.
Does this weaken the conclusion that GBTs will become obsolete for advanced research?
These project-management issues do NOT affect the conclusion.
ELIMINATE A

(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 other words, high GBTs are better than low GBTs with regard to one particular phenomenon: the twinkling star effect.
Does this weaken the conclusion that GBTs will become obsolete for advanced research?
Not really. The reason for the soon-to-be demise of GBTs is that they suffer from atmospheric effects.
So, regardless of whether some GBTs are immune to ONE TYPE of atmospheric effect, the space telescopes are immune to ALL atmospheric effects.
ELIMINATE B

(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.
This is similar to answer choice B.
In other words, SOME (well-placed) GBTs are better than other GBTs with regard to ONE particular atmospheric phenomenon: wind turbulence.
Does this weaken the conclusion that GBTs will become obsolete for advanced research?
ELIMINATE C (see answer choice B for rationale)

(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.
This is similar to answer choices B & C.
Once again, we're told that SOME GBTs are better than other GBTs for a specific reason.
Does this weaken the conclusion that GBTs will become obsolete for advanced research?
No.
Answer choice D does not suggest that any GBTs are better suited than space telescopes are to study the universe.
ELIMINATE D

(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.
Does this weaken the conclusion that GBTs will become obsolete for advanced research?
Yes!
If space telescopes are too small for certain research, then researches will still need some GBTs to perform the research described above.

Answer: E

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

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New post 20 Dec 2018, 22:26
E is best choice here
As it states the most important aspect of any astronomical research and hence weaken the conclusion of obseleteness of ground based telescopes
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Re: Images from ground-based telescopes are invariably distorted by the Ea  [#permalink]

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New post 16 Jan 2019, 10:24
But option E doesn't tell that ground based telescope will do this work, better.
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Re: Images from ground-based telescopes are invariably distorted by the Ea &nbs [#permalink] 16 Jan 2019, 10:24

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