The speed of light in a vacuum is approximately 299,792,458 meters per second, commonly rounded to 300,000 kilometers per second for simplicity in various calculations. This fundamental constant of nature represents the maximum speed at which all energy, matter, and information can travel, according to the theory of relativity. Light's speed is significant not only in physics but also in astronomy, helping scientists measure astronomical distances using the concept of light-years. It plays a crucial role in understanding the universe, including the behaviors of electromagnetic radiation and the principles of quantum mechanics.