The speed of light in a vacuum is approximately 186,282 miles per second. This means that light can travel from the Earth to the Moon in about 1.28 seconds. This incredible speed is a fundamental constant in physics and is denoted by the symbol c. This speed is crucial for understanding various concepts in astronomy and physics. For example, it plays a key role in Einstein's theory of relativity, which describes how time and space are interconnected. The vast distances in the universe make the speed of light an essential factor in measuring those distances.