Which one of the following is a reason why astronomical distances are measured in light-years?
✓ Correct answer: d) The speed of light is always the same.
ExplanationAstronomical distances are measured in light-years to effectively express the vast distances in space using a consistent and universal unit.A light-year represents the distance light travels in one year in a vacuum, which is approximately 9.46 trillion kilometers (5.88 trillion miles).Astronomers calculate the distances of stars and other celestial objects in the time it takes for light to reach us since estimating distances in miles or kilometres is inadequate on the cosmological scale.Since the speed of light is known to be constant throughout the universe and for high precision, astronomical distances are expressed in terms of light-years.The fastest light can move is in vacuum.104
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