The cosmic microwave background is a uniform 2.7 Kelvin radiation that

Question

The cosmic microwave background is a uniform 2.7 Kelvin radiation that permeates the entire universe. Although it was postulated almost 50 years before, Penzias and Wilson discovered the cosmic microwave background accidentally in the 1970s. Working at Bell Labs, these two scientists were using a radio telescope to observe distant stars. They found, however, that no matter where they pointed their telescope they observed an approximately 3 Kelvin background signal. After convincing themselves that this signal was real and not some artifact of their instrument, they consulted with a team at Princeton University that had been searching for the cosmic microwave background. The Princeton team confirmed what Penzias and Wilson had found. Apparently, Penzias and Wilson had accidentally stumbled upon the oldest observable relic of the early universe.

Why does the cosmic microwave background exist and permeate all of space? Just an instant after the Big Bang, all matter in the universe was so energetic, or hot, that it existed as free particles known as “quarks.” In the fractions of a second following, the universe expanded and cooled until the quarks lost enough energy to form electrons, protons, and neutrons, the building blocks of ordinary matter. Photons, the smallest particles of light, also filled the universe and were so energetic that they “bounced” off electrons, keeping the electrons and protons from forming atoms. After approximately 400,000 more years, the photons lost enough energy that atoms could form readily. Without any lone electrons off of which photons could “bounce,” the photons began streaming unimpeded all through the universe, mostly unchanged but for one exception. Due to the further expansion and cooling of the universe, these photons have cooled to just 2.7 degrees above absolute zero. It was these same photons that Penzias and Wilson observed approximately 13.6 billion years later here on Earth.    1 
 1. Which of the following most accurately expresses the author’s intent in writing the passage?

(A) To describe the discovery and reason for the cosmic microwave background
(B) To explain how science discoveries can be made accidentally
(C) To argue that the cosmic microwave background is the oldest observable relic of the universe
(D) To defend the work of Penzias and Wilson
(E) To support the theory of the Big Bang using the cosmic microwave background

2  
 2. According to the passage, which of the following events occurred first after the Big Bang?

(A) The universe expanded and cooled until atoms formed.
(B) Photons streamed unimpeded through space.
(C) All matter existed as particles known as “quarks.”
(D) The cosmic microwave background cooled to 2.7 Kelvin.
(E) Atomic nuclei, composed of protons and neutrons, formed

3  
 3. According to the passage, with which of the following would the author most likely agree regarding the discovery of Penzias and Wilson?

(A) It was not as important as the signal for which they were originally searching.
(B) The telescope belonging to Penzias and Wilson was more sensitive than that of the Princeton team.
(C) Penzias and Wilson would not have discovered the cosmic microwave background if it had been more than 3 Kelvin in temperature.
(D) Penzias and Wilson did not initially understand the implications of their results.
(E) Penzias and Wilson did not believe that their signal was real when they took their discovery to the Princeton team.

Sajjad1994 · Answer

OE

1. Which of the following most accurately expresses the author’s intent in writing the passage?

In the first paragraph of the passage, the author describes the discovery of the cosmic microwave background. The second paragraph explains why the cosmic microwave exists and its implications to science. Therefore, the author wrote this passage to describe the discovery and reason for the cosmic microwave background, which matches  choice (A) .

Choice (B)  is incorrect as the author cites one example of an accidental discovery, but does not explain how multiple discoveries can be made accidentally.

Choices (C)  and  (D)  are incorrect as the author does not argue or defend, respectively. Finally, the main theory presented in the passage is the cosmic microwave background, whereas  (E)  incorrectly makes it seem that the author’s intent is to defend the Big Bang and that the cosmic microwave background is only a subordinate idea. 
 
  Answer: A

Sajjad1994 · Answer

OE

2. According to the passage, which of the following events occurred first after the Big Bang?

The second sentence in the first paragraph states that  “ ust an instant after the Big Bang, all matter in the universe was so energetic, or hot, that it existed as free particles known as ‘quarks.’”  The paragraph proceeds in sequential order, and thus this event happened soonest after the Big Bang, making  (C)  the correct choice. The events described in  choices (A)  and  (B)  are said to have happened approximately 400,000 years after the Big Bang. Answer  choice (D)  describes the present state of the cosmic microwave background, 13.6 billion years later. Answer  choice (E)  is never addressed in the passage. 
  
  Answer: C

Sajjad1994 · Answer

OE

The passage states that Penzias and Wilson accidentally discovered the cosmic microwave background and did not even understand what they had found until after consulting the Princeton group. It can be inferred that they did not initially understand the implications of their result, matching  choice (D) .

Choice (A)  is incorrect as the passage does not describe the importance of the signal for which Penzias and Wilson were originally searching.

Choice (B)  is incorrect as the passage never discusses the Princeton instrumentation used for searching for the cosmic microwave background.

The capabilities of the telescope used by Penzias and Wilson are never discussed, thus  choice (C)  is not supported.

Finally, the opposite of  choice (E)  is stated in the passage, which says that Penzias and Wilson convinced themselves that their signal was real before approaching the Princeton team. 
 
  Answer: D

The cosmic microwave background is a uniform 2.7 Kelvin radiation that

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