Sunset is the time when the sun disappears below the horizon at the end of the day, painting the sky in brilliant colors. During sunset, you might see shades of orange, pink, purple, and red spreading across the clouds. This happens because sunlight has to travel through more of Earth's atmosphere when the sun is low, and the atmosphere scatters the blue light away while letting the warm colors through.

People have watched sunsets with wonder throughout human history. Ancient civilizations built monuments aligned with sunset on important dates. Artists paint them, photographers capture them, and families pause to watch them together. Some beaches and mountaintops are famous for their spectacular sunsets.

The word also describes the final period or decline of something. A politician in the sunset of her career is nearing retirement. Sunset industries are those fading away as newer technologies replace them, like how steam locomotives entered their sunset years when diesel engines arrived. When a law includes a sunset provision, it automatically ends after a certain date unless it’s renewed.

Scientists use the precise moment of sunset to calculate things like prayer times, navigation, and the length of daylight throughout the year.