Which one of the following is a reason why astronomical distances are measured in light-years?
[UPSC Civil Services Exam – 2021 Prelims]
(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.
- A light-year is a measurement of distance in space.
- The astronomical distances are measured in light-years because, the speed of light is constant throughout the universe and is known to high precision. In a vacuum, light travels at 670,616,629 mph (1,079,252,849 km/h).
- To find the distance of a light-year, you multiply this speed by the number of hours in a year (8,766). The result: One light-year equals 5,878,625,370,000 miles (9.5 trillion km).