Convert Kilometer/Second (km/s) to Speed of Light (c) instantly.
About these units
Kilometer/Second (km/s)
A kilometer per second represents a very high speed—1,000 meters every second—and is particularly important in astronomy, planetary science, and astrophysics. Orbital velocities around planets, escape velocities, solar winds, and the motion of stars relative to each other are commonly measured in km/s. This scale captures speeds far beyond terrestrial transportation. For example, Earth orbits the Sun at roughly 30 km/s, and meteoroids entering Earth's atmosphere may arrive at speeds between 11 and 72 km/s. km/s is a natural step up from m/s when describing the motion of celestial bodies.
Speed of Light (c)
The speed of light in a vacuum, denoted c, is exactly 299,792,458 m/s, one of the most fundamental constants of physics. Light speed defines the structure of spacetime, the upper limit for classical information transfer, and the basis for relativity. Time dilation, length contraction, and mass-energy equivalence (E = mc²) all arise from the invariance of c. In astronomy, the speed of light is used to define light-years, measure cosmic distances, and synchronize observations across telescopes. In communication technology, optical networks rely on light-speed propagation through fiber, albeit slightly slower than in vacuum. c is not just a speed—it is a cornerstone of the physical universe.