A light-year is the distance that light travels in a vacuum in one Julian year (365.25 days). It's about 9.46 trillion kilometers or 5.88 trillion miles.

This is because a light-year is an incredibly vast distance, covering trillions of kilometers. 5,000,000 centimeters is a relatively tiny distance in comparison.

Centimeters are used for measuring the length of everyday objects like books, rulers, or the height of a small plant.

Direct practical uses are rare due to the extreme scale difference. However, it's useful for educational purposes to demonstrate the vastness of space and the concept of different measurement scales.