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QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou

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QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou [#permalink] New post 21 Sep 2016, 02:11
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Question Stats:

57% (02:52) correct 42% (06:04) wrong based on 7 sessions
Supernovas in the Milky Way are the likeliest source for most of the cosmic rays reaching Earth. However, calculations show that supernovas cannot produce ultrahigh-energy cosmic rays (UHECRs), which have energies exceeding 1018 electron volts. It would seem sensible to seek the source of these in the universe’s most conspicuous energy factories: quasars and gamma-ray bursts billions of light-years away from Earth. But UHECRs tend to collide with photons of the cosmic microwave background—pervasive radiation that is a relic of the early universe. The odds favor a collision every 20 million light-years, each collision costing 20 percent of the cosmic ray’s energy. Consequently, no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.
For the following question, consider each of the choices separately and select all that apply.

It can be inferred that the author of the passage would agree with which of the following about the origin of UHECRs that reach Earth?

  • The origin is something other than supernovas in the Milky Way.
  • The origin is most likely something other than very distant quasars or gamma-ray bursts.
  • The origin is most likely no more than a little over 100 million light-years away from Earth
.

[Reveal] Spoiler: OA
A,B, and C



In the context of the author’s argument, the last sentence performs which of the following functions?

A) It explains a criterion that was employed earlier in the argument.
B) It shows that an apparently plausible position is actually self-contradictory.
C) It is a conclusion drawn in the course of refuting a potential explanation.
D) It overturns an assumption on which an opposing position depends.
E) It states the main conclusion that the author is seeking to establish

[Reveal] Spoiler: OA
C



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Re: QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou [#permalink] New post 21 Sep 2016, 02:12
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Explanation

1) All three choices are correct. The question asks about claims the author would agree with. Choice A is correct: The passage states that supernovas in the Milky Way “cannot produce ultrahigh-energy cosmic rays.” Choice B is correct: Since very distant quasars and gamma-ray bursts are
“billions of light-years away from Earth,” they are too far away for a UHECR to reach Earth. Choice C is correct: The last sentence of the passage states that “no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.”

2) The last sentence is the conclusion of an argument in the last half of the passage; it puts a constraint on the possible origin of UHECRs relative to Earth and thereby rules out the possibility, mentioned earlier in the passage, that distant quasars and gamma-ray bursts could be the origin of UHECRs. Therefore Choice C is correct. It is important to note that the last sentence does not show any plausible position to be self-contradictory (Choice B), and that it does not state the author’s main conclusion (Choice E), since it is relevant to only one of the two hypotheses considered in the passage.
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Re: QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou [#permalink] New post 24 Jul 2017, 03:34
Carcass wrote:
Explanation

1) All three choices are correct. The question asks about claims the author would agree with. Choice A is correct: The passage states that supernovas in the Milky Way “cannot produce ultrahigh-energy cosmic rays.” Choice B is correct: Since very distant quasars and gamma-ray bursts are
“billions of light-years away from Earth,” they are too far away for a UHECR to reach Earth. Choice C is correct: The last sentence of the passage states that “no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.”

2) The last sentence is the conclusion of an argument in the last half of the passage; it puts a constraint on the possible origin of UHECRs relative to Earth and thereby rules out the possibility, mentioned earlier in the passage, that distant quasars and gamma-ray bursts could be the origin of UHECRs. Therefore Choice C is correct. It is important to note that the last sentence does not show any plausible position to be self-contradictory (Choice B), and that it does not state the author’s main conclusion (Choice E), since it is relevant to only one of the two hypotheses considered in the passage.


The first question's third choice seems ambiguous as the passage points out much beyond than 100 million light years, however, the answer choice (C) says no more than 100 million light years. How that can be?
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Re: QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou [#permalink] New post 25 Jul 2017, 01:33
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Yes, I totally agree with you if not for a small word you forget to mention in that phrase.

Quote:
The origin is most likely no more than a little over 100 million light-years away from Earth


with this in the passage

Consequently, no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.

They perfectly match.

Hope this helps

Regards
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Re: QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou [#permalink] New post 25 Jul 2017, 11:55
Carcass wrote:
Yes, I totally agree with you if not for a small word you forget to mention in that phrase.

Quote:
The origin is most likely no more than a little over 100 million light-years away from Earth


with this in the passage

Consequently, no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.

They perfectly match.

Hope this helps

Regards


Thank you, :-D :-D :-D the test organizers are so cunning. Also, what you think my level is if I make such a mistake? Thanks in advance.
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Re: QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou [#permalink] New post 26 Jul 2017, 02:30
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Difficult to judge based on one question only. It could be a silly mistake or something related with your English skills.
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Re: QOTD # 1-2 Supernovas in the Milky Way are the likeliest sou   [#permalink] 26 Jul 2017, 02:30
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