Encyclopædia Galactica Rami T. F. Rekola Tuorlan Astronomical Society Tuorla Observatory University of Turku

Light year (ly)

Light year is the distance light travels in one year. The speed of light is about 300,000 km/s, so during one year the light travels approximately 9500 billion km (5900 billion miles). One would have to drive around the Earth on the equator 236 million times to get this many kilometres on the clock.