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Astronomy professor: Stars twinkle when they are observed [#permalink]
21 Jul 2005, 21:24
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Astronomy professor: Stars twinkle when they are observed from Earth because of the refraction in the Earthâ€™s atmosphere. This refraction is minor and so we donâ€™t see any twinkling of massive objects such as the Moon and the Sun.
Student: I disagree. The Earthâ€™s atmosphere is too transparent to cause any distortion of light coming from space. If your explanation of the twinkling of stars were correct then planets such as Mars and Venus would also twinkle when observed from Earth but they do not. I believe stars appear twinkling because they are so far away that light from them is travelling billions of miles and inevitably gets distorted by occasional aggregations of space dust.
The highlighted portions of the text perform which functions in the argument?
A: the first is the position the student disagrees with while the second is the evidence the student uses to back his opinion
B: the first is a rejection of a possible objection to the professorâ€™s statement; the second is used as evidence in the studentâ€™s argument
C: the first is a challenge to the professorâ€™s statement while the second mentions a fact which the student uses as evidence to refute the professorâ€™s statement
D: the first is a consideration that casts doubt on the professorâ€™s statement while the second is a development of this consideration
E: the first is a relevant addition to the professorâ€™s statement while the second describes a reason why the student disagrees with this addition.
I pick E because the first boldface is in fact relevant information in addition to the professorâ€™s initial stance that â€œStars twinkle when they are observed from Earth because of the refraction in the Earthâ€™s atmosphereâ€
As Folaa mentioned, the first boldface is a relevant addition. IMO, the second boldface is a reason why the student disagrees with the addition. The student states that the refraction is not possible because the earth's atmosphere is too transparent. The second boldface is not an evidence to prove that the earth's atmo is too transparent. Instead, the student wants to say that if what the professor said was true of the massive objects not twinkling because they r huge, then mars and venus should twinkle becos they r smaller in size.