Convert Speed of Light (c) to Knot (UK) (kt (UK)) instantly.
About these units
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.
Knot (UK) (kt (UK))
The UK knot historically varied slightly from the international knot because the UK used different values for the nautical mile depending on era and maritime authority. Though the differences were minor, they mattered in navigation, where precision affects charting, dead reckoning, and ocean voyaging. Modern UK practice fully aligns with the international knot (1 nautical mile per hour), but historical documents and charts may reference older UK knot values. The knot's rich maritime heritage—used by sailors measuring speed with knotted ropes dragged along the water—makes it one of the oldest continuously used speed units.