Chapter 33, Problem 4RQ

Is the light-year a measurement of time or distance?

To determine

Whether the light-year is a measurement of time or distance.

Answer to Problem 4RQ

The light-year is a measurement of distance.

Explanation of Solution

The light-year is a distance that light travels in one year. One light-year is approximately equal to $10\text{ trillion}$.

Light years are used to measure vast distances between Earth and stars. For example, Proxima Centauri, the closest star from Sun is $4.2\text{ light-years}$ away. The diameter of the milky way galaxy is 100,000 light-years. Andromeda galaxy is $2.3\text{ million}$ light-years away. Light does not reach to us on the spot as it takes light years to travel.

Conclusion:

Therefore, the light-year is a measurement of distance.