It is exact because by international agreement a metre is defined to be the length of the path travelled by light in vacuum during a time interval of 1/299792458 second. The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Sunlight takes about 8 minutes 17 seconds to travel the average distance from the surface of the Sun to the Earth.Īpproximate values (to three significant digits)įrom the nearest galaxy (the Canis Major Dwarf Galaxy) to Earthįrom Earth to the edge of the observable universe
