Which medium does light travel fastest through

The fastest thing in the whole universe is the speed of light in a vacuum (like outer space!), clocking in at a great 2.99 x 108 m/s. Light travels in waves, and we call thistraveling propagation. Propagation of waves has both a speed and a direction, called the velocity.

Liquids are not packed as tightly as solids. And gases are very loosely packed. The spacing of the molecules enables sound to travel much faster through a solid than agas. Sound travels about four times faster and farther in water than it does in air.