NextMockSearch exams, e.g. SSC CGL, UPPSC, Lekhpal
हिंदी
UPSC PYQPrelims 2021

Civil Services Examination · Question 76

Which one of the following is a reason why astronomical distances are measured in light-years?

  1. Distances among stellar bodies do not change.
  2. Gravity of stellar bodies does not change.
  3. Light always travels in straight line.
  4. Speed of light is always same.
Show answer & explanation

Answer: (D) Speed of light is always same.

Explanation

The speed of light in vacuum is constant, so the distance light travels in a year is a fixed, convenient unit.