The speed of light in a vacuum is exactly 299,792,458 meters per second (m/s). This value is not just a measurement—it is a defined constant of nature and one of the most fundamental quantities in physics.

Light is an electromagnetic wave, and in a perfect vacuum (a space with no matter), it travels at its maximum possible speed. This speed is denoted by the symbol “c” and is critical in many areas of science, particularly in Einstein’s theory of relativity, where it acts as the ultimate speed limit of the universe. Nothing—no signal, object, or information—can travel faster than this speed.

Since 1983, the meter has been defined based on the speed of light: one meter is the distance light travels in 1⁄299,792,458 of a second. This definition makes the speed of light an exact number, with no uncertainty, unlike most measured physical constants.

This constant also appears in the famous equation E = mc², showing the equivalence of energy and mass. In this formula, the “c²” (the speed of light squared) acts as a huge multiplier, demonstrating how a small amount of mass can be converted into a large amount of energy.

In summary, the speed of light is more than just a speed—it’s a foundation upon which much of modern physics is built.