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 research3) 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