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UPSC Prelims & Mains Questions
Which one of the following is a reason why astronomical distances are measured in light-years?
A)
Distances among stellar bodies do not change
B)
Gravity of stellar bodies does not change
C)
Light always travels in straight line
D)
Speed of light is always same.

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

Note : A light-year is the distance a beam of light travels in a vacuum in one year. The reasons for measuring astronomical distances in light years are familiar units like kilometers and miles are absurdly small for describing the vastness of the cosmos and the speed of light is both finite and constant with a value of approximately 2.998 x 108 m/s.

Year : 2021
Category : General Studies
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