How fast does light travel in a vacuum when measured in meters per second?

Light traveling through a vacuum moves at exactly 299,792,458 meters (983,571,056 feet) per second. That's about 186,282 miles per second — a universal constant known in equations and in shorthand as "c," or the speed of light.

According to physicist Albert Einstein's theory of special relativity, on which much of modern physics is based, nothing in the universe can travel faster than light. The theory states that as matter approaches the speed of light, that matter's mass becomes infinite. That means the speed of light functions as a speed limit on the whole universe.

The speed of light is so immutable that, according to the U.S. National Institute of Standards and Technology, it is used to define international standard measurements like the meter (and by extension, the mile, the foot and the inch).