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Q34 (NDA-II/2009) Geography › World Physical Geography › Earth rotation and time Answer Verified

Consider the following statements : 1. The earth’s rotation axis is not at 90° to its orbital plane, 2. The earth’s rotation axis is inclined at 23.5°. Which of the statements given above is/are correct?

Result
Your answer: —  ·  Correct: C
Explanation

Statement 1 is correct because the Earth's rotation axis is not perpendicular (90°) to its orbital plane; instead, it is tilted [c3, t2]. This tilt is known as obliquity [t1, t8]. Statement 2 is also correct as the standard value for this axial tilt is approximately 23.5° [c1, t2, t3]. Specifically, the axis makes an angle of 23.5° with the normal (perpendicular) to the orbital plane, which implies it makes an angle of 66.5° with the orbital plane itself [c1]. This inclination is responsible for the variation in seasons and the changing length of day and night throughout the year [c4, t9]. While the exact value fluctuates slightly over long cycles between 22.1° and 24.5°, the current mean value is widely cited as 23.5° in educational contexts [t5, t6, t8]. Therefore, both statements accurately describe the Earth's axial orientation.

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 19: The Motions of The Earth and Their Effects > 19.1. Rotation of Earth > p. 251
  2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > In a Nutshell > p. 184
  3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > 12.2.2 Seasons on the Earth > p. 177
  4. [4] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/obliquity
  5. [5] https://education.nationalgeographic.org/resource/axis/
  6. [6] https://science.nasa.gov/science-research/earth-science/milankovitch-orbital-cycles-and-their-role-in-earths-climate/
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