Which one of the following is a reason why astronomical distances are measured in light-years?
[amp_mcq option1=”Distances among stellar bodies do not change.” option2=”Gravity of stellar bodies does not change.” option3=”Light always travels in straight line.” option4=”Speed of light is always same.” correct=”option4″]
This question was previously asked in
UPSC IAS – 2021
The correct answer is D) Speed of light is always same.
Astronomical distances are vast, making standard units like kilometres or miles impractical. A light-year is defined as the distance light travels in one year in a vacuum. The use of light-years as a unit of distance in astronomy is based on the fact that the speed of light in a vacuum is a constant (approximately 299,792,458 meters per second). This constant speed provides a reliable basis for measuring extremely large distances across space based on time.