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Difficulty: MediumParagraph Reordering and Placement

The following paragraphs are from an essay about the discovery of pulsars. For the sake of the logic and cohesion of this essay, in what order should the paragraphs be arranged?

  1. 1[1]
    In the summer of 1967, graduate student Jocelyn Bell was busy analyzing miles of chart paper tracking radio waves from outer space. Using a newly constructed radio telescope array in Cambridge, England, she was scanning the skies for quasars—distant, active galactic nuclei.
  2. 2[2]
    While examining these printouts, Bell noticed an unusual signal: a series of regular, rapid pulses occurring every 1.33 seconds. Her supervisor, Antony Hewish, initially dismissed the anomaly as man-made interference, arguing that cosmic sources could not pulse so quickly.
  3. 3[3]
    To rule out this possibility of local interference, Bell continued her observations and soon discovered three other rapidly pulsing sources in different parts of the sky. This new evidence convinced the research team that the signals were indeed coming from deep space.
  4. 4[4]
    These mysterious cosmic beacons were soon named 'pulsars,' short for pulsating radio stars. Astronomers eventually determined that pulsars are rapidly rotating neutron stars—the collapsed cores of massive stars—which emit beams of electromagnetic radiation that sweep across the Earth like lighthouse beams.

Answer

The correct order of paragraphs is Paragraph 1, Paragraph 2, Paragraph 3, and then Paragraph 4.
The correct order follows a clear chronological and logical progression. Paragraph 1 establishes the setting (1967), the researcher (Jocelyn Bell), and the initial research (analyzing chart paper for quasars). Paragraph 2 follows logically as Bell examines 'these printouts' (referring to the chart paper), detects a pulsing signal, and her supervisor suspects 'man-made interference.' Paragraph 3 continues the narrative with 'To rule out this possibility of local interference,' explaining how she found more signals and proved they came from deep space. Paragraph 4 concludes the essay by referring to the deep-space signals as 'these mysterious cosmic beacons,' naming them 'pulsars,' and explaining their physical mechanism.

Step-by-Step Solution

1
Identify the introductory paragraph.
Paragraph 1 is identified as the introduction.
Paragraph 1 sets up the narrative by establishing the context (1967, Cambridge), the researcher (Jocelyn Bell), and the goal of analyzing chart paper from a radio telescope to scan for quasars. None of the other paragraphs can begin the essay because they refer to pre-existing research or signals.
2
Determine the next logical step in the narrative.
Paragraph 2 follows Paragraph 1.
Paragraph 2 starts with 'While examining these printouts,' which directly links back to the 'chart paper' mentioned in Paragraph 1. It introduces the discovery of the anomaly and the supervisor's initial skepticism, labeling the pulses as 'man-made interference.'
3
Link the verification process to the initial skepticism.
Paragraph 3 follows Paragraph 2.
Paragraph 3 begins with 'To rule out this possibility of local interference,' directly responding to the supervisor's concern in Paragraph 2. It documents the discovery of additional sources that proved the signals originated in deep space.
4
Establish the concluding paragraph that names and defines the phenomenon.
Paragraph 4 follows Paragraph 3.
Paragraph 4 opens with 'These mysterious cosmic beacons,' referring back to the deep-space signals confirmed in Paragraph 3. It provides the final resolution by naming the beacons 'pulsars' and defining their astronomical nature.

Key Concept

Paragraph reordering relies on identifying cohesive transition words, pronoun references, and logical/chronological progression between paragraphs.
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Topics

Paragraph Reordering and Placement

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