How Fast Is the Speed of Light?

When light travels in a vacuum, its speed is 186,282 miles per second. The fastest aircraft, which is the Boeing-43 scramjet, has a speed of 7,546 miles per hour. If these two speeds are compared, the jet's speed is approximately 0.0004 percent that of light.

The speed of light is extremely fast and constant in a vacuum. However, if light passes through a medium like dust, then it does slow down. Photons can travel at this speed.

Based on Albert Einstein's general theory of relativity, objects that are moving close to the speed of light experience an increase in mass and a decrease in length. Theoretically, this suggests that it is impossible for an object to travel at this speed.