c (speed of light)

The speed of light, denoted by "c," is the fastest speed at which all electromagnetic waves, including visible light, travel in a vacuum. It is approximately 299,792 kilometers per second (about 186,282 miles per second). This universal constant means nothing in the universe can travel faster than light. It plays a fundamental role in physics, influencing how we understand space, time, and the structure of the universe. For example, when we observe distant stars or galaxies, we see them as they were when the light left them, which can be millions or billions of years ago.