Multiple choice Why do scientists use light years to measure distances in space? it's the same as kilometers distances are too big because there are no roads in outer space because the only thing that travels in outer space is light Reveal answer Fill a bubble to check yourself B Correct answer Explanation Distances in space are so vast that using standard units like kilometers or miles would result in unmanageably large numbers. A light year is a unit of distance based on how far light travels in one year, which simplifies astronomical calculations.