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Difficulty: MediumDistinguishing Main Ideas from Supporting Details

Passage

In 1851, French physicist Léon Foucault suspended a 28-kilogram brass-coated lead bob from the dome of the Panthéon in Paris using a 67-meter wire. As the pendulum swung back and forth, a stylus attached to the bob traced lines in wet sand, showing that the plane of oscillation shifted over time. To observers, the pendulum appeared to be slowly rotating clockwise. In reality, the plane of oscillation remained constant in space, while the Earth rotated beneath it. Although astronomers had long accepted Copernican heliocentrism, they relied on complex celestial observations and mathematical models to prove it. Foucault’s demonstration was revolutionary because it offered the first immediate, mechanical evidence of the Earth's rotation that could be observed without looking at the sky. Critics initially questioned the precision of the experiment, pointing to potential disturbances like air currents and wire torsion, but Foucault minimized these errors through careful engineering of the pivot. Ultimately, the Panthéon demonstration democratized science, turning a mathematical abstraction of planetary motion into a tangible public spectacle.

Which statement best summarizes the main idea of the passage?

  1. A
    The pendulum consisted of a 28-kilogram brass-coated lead bob suspended by a 67-meter wire from the Panthéon dome.
  2. Foucault's demonstration was significant because it provided the first direct, mechanical proof of the Earth's rotation, making a theoretical concept visible to the public.Answer
  3. C
    Nineteenth-century physicists revolutionized astronomical science by discovering that the Earth rotates on its axis.
  4. D
    Foucault's demonstration failed to convince critics because of errors caused by air currents and wire torsion.

Answer

Foucault's demonstration was significant because it provided the first direct, mechanical proof of the Earth's rotation, making a theoretical concept visible to the public.
The correct answer captures the primary point of the passage. The passage explains that astronomers already accepted the Earth's rotation but lacked simple, direct proof, and Foucault's demonstration was revolutionary because it provided the first immediate, mechanical evidence that the public could observe.

Step-by-Step Solution

1
Analyze the passage to identify the primary focus and central argument.
The passage details Léon Foucault's 1851 pendulum experiment, highlighting that while astronomers already accepted Earth's rotation, Foucault provided the first direct, mechanical, and publicly observable proof of it.
Understanding the main thesis helps distinguish it from minor details or exaggerated claims.
2
Evaluate the options against the primary focus.
The option describing the physical setup (brass bob and wire) is a minor supporting detail. The option claiming that physicists discovered the Earth's rotation is too broad and contradicts the passage's note that astronomers already accepted this. The option claiming the experiment failed due to errors is directly refuted by the text. The option emphasizing the first direct, mechanical proof that made a theoretical concept visible aligns perfectly with the passage's thesis.
Eliminating options that are either too specific, too broad, or inaccurate isolates the correct main idea.

Key Concept

Distinguishing Main Ideas from Supporting Details
Estimated Time:1m 30s
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Distinguishing Main Ideas from Supporting Details

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