Speed of Light
The maximum speed at which all massless particles, electromagnetic waves, and information travel through a vacuum.
Governing formula
c = 299,792,458 m/s
SI unit
m/s
In depth
In Special Relativity, c is a universal speed limit and space-time conversion constant. It connects mass and energy via E = mc² and remains invariant in all inertial reference frames.
Examples in the real world
Light traveling from the Sun to Earth takes approximately 8 minutes and 20 seconds (1.5 × 10¹¹ m / c).