What distance does a light-year measure?

What distance does a light-year measure?

• A. Time for light to travel one year.
• B. Distance to stars and galaxies.
• C. Distance within the solar system.
• D. Distance from Earth to the Moon.

Answer: (B)

A light-year measures distance. It is the distance light travels in vacuum in one year, which is about 9.46 trillion kilometers (roughly 5.88 trillion miles). Because light has a finite speed, using how far it goes in a year gives a practical way to express the enormous gaps between stars and galaxies. It isn’t a measure of time, and it isn’t specifically about the Solar System or the Earth–Moon distance—the unit is used for the huge scales of distant stars and galaxies.

A light-year measures distance. It is the distance light travels in vacuum in one year, which is about 9.46 trillion kilometers (roughly 5.88 trillion miles). Because light has a finite speed, using how far it goes in a year gives a practical way to express the enormous gaps between stars and galaxies. It isn’t a measure of time, and it isn’t specifically about the Solar System or the Earth–Moon distance—the unit is used for the huge scales of distant stars and galaxies.