A light-year is the distance that light travels in a vacuum in one Julian year (365.25 days). It's a unit of astronomical distance.

There are approximately 5.88 trillion miles (9.46 trillion kilometers) in one light-year.

This is because light-years measure interstellar distances, which are astronomically large, making human-scale distances like 500,000 miles extremely tiny in comparison.

No, this specific conversion (500,000 miles to light-years) is not commonly used because the resulting number is extremely close to zero, and light-years are typically reserved for much larger cosmic distances.