Sidereal Time is a timekeeping system that is based on the Earth's rotation relative to distant stars rather than the Sun. It measures the time it takes for the Earth to complete one full rotation on its axis, which is approximately 23 hours, 56 minutes, and 4 seconds. This is slightly shorter than the 24-hour solar day we commonly use. Astronomers use Sidereal Time to track the positions of celestial objects in the night sky. By knowing the sidereal time, they can determine which stars and constellations are visible at any given moment, aiding in navigation and observation of the universe.