Twilight is the time of day when the sun is just below the horizon, creating a soft, diffused light. It occurs in three phases: civil, nautical, and astronomical twilight. During civil twilight, there is enough natural light for most outdoor activities, while nautical twilight is when the horizon is still visible at sea, and astronomical twilight marks the point when the sky is dark enough for astronomers to observe celestial objects. The duration of twilight varies depending on the geographical location and the time of year. Near the poles, twilight can last for hours or even days, while in tropical regions, it is usually brief. This phenomenon is influenced by the angle of the Earth in relation to the sun.