UPSC Prelims 1996 · General Studies
Question 125: Science and Technology
Consider the following statements: A person in a spaceship located half-way between the earth and the sun will notice that the I. Sky is jet black. II. Stars do not twinkle. III. Temperature outside the spaceship is much higher than that on the surface of the earth. Of these statements
AnswerThe answer is (b).
Outside the atmosphere the sky appears black even with the Sun in view, because there is no air to scatter sunlight (I), and stars shine steadily without twinkling, since twinkling is caused by the atmosphere's changing refraction (II). Statement III is the one the key rejects: space is a near-vacuum, so there is no hot air around the ship, and open space is very cold, with only surfaces facing the Sun heating up. Remember: black sky and steady stars in space.
- I. With no air to scatter light, the sky looks black.
- II. Stars do not twinkle without the atmosphere.
- III. Space is a near-vacuum and very cold; only sunlit surfaces heat up, so it is not simply hotter than Earth's surface.
Why each option is right or wrong
- (a) III alone, but I and II are also correct.
- (b) Right: statements I and II.
- (c) Includes III, which the key rejects, and leaves out II.
- (d) Includes III, which the key rejects.
Worth knowing: A sunlit object half way to the Sun receives about four times Earth's sunlight and would be hotter than Earth's surface, so III is arguable.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1996, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.