Images from ground-based telescopes are invariably distorted by the

Hi ReedArnoldMPREP - where is the proof that we are talking about binaries ? thats a big assumption on our part is it not ?

I thought other than Ground based telescopes and Space based telescope -- there could be a 3rd or 4th category of telescopes.

If you choose E - we are making a BIG ASSUMPTION (Which we are not supposed to do when looking for the OA)

The big assumption is THAT there are only 2 types of telescopes

Hi zhanbo - how can one make such an inference ? i thought perhaps there was a 3rd type of telescope (not Earth based nor Space based) -- perhaps under-ground based or underwater based telescope or outerspace telescopes

Thus i thought E just told us that Space based telescopes CANT do the job of Detailed spectral analyses

Blackberry phones are invariably heavier. iPhones are lighter. So, Blackberry phones will become obsolete for folks who want light pockets.
(c) By carefull choice of blackberry models, it is possible for the newer models of blackberry phones to avoid most of the hardware that make Blackberry phones heavy.
(e) All smartphone customers want to play Angry Birds on their smart-phones. iPhone’s battery is too weak to currently play the latest release of Angry Birds.

GMATNinja karishma In option E, is it safe to think that if space telescopes can't fulfill the purpose, only ground telescopes will solve it? No other types of telescopes? Or am I moving away from the argument thinking this way?

GMATNinja karishma In option E, is it safe to think that if space telescopes can't fulfill the purpose, only ground telescopes will solve it? No other types of telescopes? Or am I moving away from the argument thinking this way?

Hi avigutman - just so i fully understand - you would still select E even if you were NOT FULLY CONFIDENT that ground based telescopes can fill in the role to perform Detailed spectral analyses, correct ?

In this analogy - i know iPhones cannot perform the role but can Blackberry's - we dont know .

(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 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.)

Hey,

I have a question regarding choice E.
Stating that space telescopes are not adapted for certain purposes does not imply that ground-based telescopes are. There is no mention of the fact that ground-based telescope is able to capture more light.

Please help

Note that either you can have ground based telescopes or space telescopes. There is nothing else possible. What is not on the ground is above ground (in space). One specific use for which telescopes are used today (astronomers rely on Detailed spectral analyses) needs more light gathering capacity than space telescopes. So ground based telescopes must be providing those.

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.

­Exactly what i was also looking for because nowehere in the actual question statement or the answer choice says that Ground based ones can gather more light. All of the above people are assuming it because thats the only way to answer this question by eliminating B which seems to be very possible. 

I think we still need to do justice to this well-crafted question. Here's my attempt:

I'll just focus on options B, D, and E. However, before I get to the options, let me create a parallel argument.

Students of Class 9A are invariably ill-dressed. Students of Class 9B, however, are well-dressed. Therefore, students of Class 9A will never represent the school in inter-school competitions.

While this argument is not parallel to the original argument in every nuance, I believe it captures the essence of the original argument. If you do not agree, feel free to let me know.

Now, let me create parallel options for this argument:

Option B: Students of Class 9A mentored by their class-teacher do not have the kinds of dressing problems that make students look like beggars.

Does this option weaken the above argument?

The answer is NO. The reason is that this option says that some students of Class 9A (i.e. students mentored by the class-teacher) do not have some kinds of dressing problems. Okay. So, these students are probably better than other students of Class 9A in this respect. However, vis-a-vis students of Class 9B, are these students comparable? There is no indication of this comparison. The reasoning of the argument still holds as is. Even though these students do not have certain kinds of dressing problems, they still are ill-dressed, as originally stated in the argument. Thus, it still doesn't make any sense to ask these students to represent the school. Think about it. The reasoning in the argument was that students of Class 9A are shabby and students of Class 9B are not and that thus students of Class 9A will not represent the school. Even if some students of Class 9A are less shabby than some other students of Class 9A, all the students of Class 9A are still shabby, and thus the reasoning of the argument is still intact.

Similarly, the given option B just says that certain ground-based telescopes (i.e. located on mountain summits) do not have 'certain' kinds of distortions. However, they still have distortions as should every ground-based telescope have (given the facts in the passage). Thus, the reasoning of the argument still holds as is.

Option D (The Parallel form): When students of Class 9A are mentored by their class teacher, they become the best-dressed of the students of Class 9A.

Again, in this option too, just as in option B, we are comparing shabbiness or the sense of dressing among the students of Class 9A. We still are not presenting any advantage students of Class 9A have over students of Class 9B. Of course, if we rank some students of Class 9A in terms of their dressing sense, some students are going to come at the top. However, this doesn't have any effect on the given fact that all students of Class 9A are ill-dressed. Thus, the reasoning of the argument still stands as is.

Similarly, the given option D says that the telescopes located at high altitudes near the equator provide the best 'Earth-based' observations (not the best 'overall' - in which case this option will present an advantage of ground-based telescopes over space telescopes and thus will weaken the argument). Comparing different ground-based telescopes will not help; of course, some of them will be better than the others. However, they all are invariably inferior to the orbiting space telescopes, as stated in the passage. Thus, the reasoning of the passage holds as is.

Option E: This option presents a shortcoming of the orbiting space telescopes. Let me also state that this shortcoming is with respect to ground-based telescopes, not a shortcoming in general. Why do I say that this shortcoming is w.r.t ground-based telescopes?

Because of what the non-essential modifier(within double commas) means. The modifier means that the astronomers rely upon detailed spectral analyses for determining the chemical composition and evolutionary history of stars. If they rely on this capability for determining X (chemical composition etc), they must already be having this capability because, from the context, it seems that they are already determining the chemical composition and evolutionary history of stars. Now, if they have this capability and the orbiting space telescopes cannot provide this capability, it's likely that ground-based telescopes currently provide this capability. Thus, this option presents an advantage ground-based telescopes have over orbiting space telescopes and thus gives us a reason to doubt that ground-based telescopes will become obsolete.

I hope it helps!

- CJ

ChiranjeevSingh ­Thank you for the detailed analysis.
I missed 'Earth-based' and selected D.
To add to your reasoning for E, would it be right to say that the space satellites are something that have not been launched? The qs says that the space telescopes 'should' be able to provide detailed images. Can I say that this implies that space telescopes have not been introduced yet? This futher strengthens your reasoning that it is likely that the ground telescopes have the light capability as the astronomers ARE currently studying the chemical composition.
Kindly let me know if my reasoning is correct.

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

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.