Astronomical distances, especially the distances between planets and stars, are so huge that they are measured in miles and kilometers. Expressing these in units can be extremely difficult, so they can be measured in AU (Astronomical Units), light years, parsecs, etc.
The speed of light is constant throughout the universe and it is known for high precision. For this reason astronomical distances are measured in light years.
Q. Which of the following is the reason for astronomical distances being measured in light years ? [UPSC 2021]
(a) The distances between stellar bodies do not change.
(b) The gravity of stellar bodies does not change.
(c) Light always travels in a straight line.
(d) The speed of light is always the same.
Q. One parsec, a unit of measurement of stellar distances, is equal to – [RAS 1999]
(a) 4.25 light years
(b) 3.25 light years
(c) 4.50 light years
(d) 3.05 light years