Convert **light speed (vacuum)** to **kilometer/second (km/sec)**

Selected category: speed.

Speed of light (c) in vacuum is equal to 299 792 458 meters/sec with a relative measurement uncertainty of 4 parts per billion. Up to 17^{th} century humanity wasn't sure if light was transmitted instantaneously or simply very quickly. The Danish astronomer, Ole Christensen Rømer first demonstrated that light travelled at a finite speed when he studied the apparent motion of Jupiter's moon Io.

Kilometer per second (km/sec) is a unit of velocity equal to 1000 m/sec.

Swap, do a kilometer/second (km/sec) to light speed (vacuum) conversion.