The commonly accepted unit of measurement for distance in space is the light-year. A light-year is defined as the distance that light travels in a vacuum in one year, approximately 5.88 trillion miles (9.46 trillion kilometers). This unit is used primarily in astronomy to express vast distances between celestial objects, such as stars and galaxies. Light-years provide a practical way to communicate the enormous scales involved in space exploration and the universe, allowing scientists and astronomers to gauge distances within the cosmos with greater context and understanding.