A light-year, alternatively spelled light year (ly or lyr [2]), is a unit of length used to express astronomical distances and is equal to exactly, which is approximately 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Using lightyears to measure distance in the Universe and how long it would take to travel one lightyear by foot, car, plane and rocket. A light-year is the distance light travels in a vacuum over the course of one year. Multiply the speed of light by the number of seconds in a year, and you get the magic number: about 9.46 trillion kilometers, or roughly 5.88 trillion miles. A light-year is a measurement of distance and not time (as the name might imply). A light-year is the distance a beam of light travels in a single Earth year, which equates to approximately 6 ...
