Which statement best defines a light-year?

Which statement best defines a light-year?

• A. The distance light travels in 365 days
• B. The distance light travels in one year
• C. The distance to the nearest star
• D. The time it takes light to reach Earth from the Sun

Answer: (B)

A light-year is a distance unit equal to how far light travels in one year in a vacuum. Light moves about 299,792 kilometers every second, so in a year (roughly 31.56 million seconds) it covers roughly 9.46 trillion kilometers (about 5.88 trillion miles). This makes the light-year a convenient way to express huge cosmic distances, like how far away stars and galaxies are. The other ideas mix time with distance or refer to a specific event or object (for example, minutes it takes light to reach Earth from the Sun, or the distance to the nearest star), which aren’t definitions of the unit itself.

A light-year is a distance unit equal to how far light travels in one year in a vacuum. Light moves about 299,792 kilometers every second, so in a year (roughly 31.56 million seconds) it covers roughly 9.46 trillion kilometers (about 5.88 trillion miles). This makes the light-year a convenient way to express huge cosmic distances, like how far away stars and galaxies are. The other ideas mix time with distance or refer to a specific event or object (for example, minutes it takes light to reach Earth from the Sun, or the distance to the nearest star), which aren’t definitions of the unit itself.