Sunsets

Sunsets are daily optical phenomena that occur as the Sun’s disk passes below the western horizon, marking the transition from day to night. The visible sunset palette arises primarily from Rayleigh scattering: sunlight travels through a greater thickness of Earth’s atmosphere at sunset, scattering shorter wavelengths (blue and green) out of the line of sight and leaving longer wavelengths (red, orange, pink) to dominate. The specific colors depend on atmospheric composition and conditions, including aerosols from dust, pollution, smoke, humidity, and cloud cover. Particulate matter can enhance reds and purples by absorbing shorter wavelengths, while high clouds can reflect and refract light, producing varied hues.

The timing and extent of a sunset vary with latitude, season, and local topography. In clear air, sunsets tend toward deeper reds; in hazy or polluted air, colors may shift toward softer pinks and oranges. After sunset, twilight follows, categorized as civil, nautical, and astronomical depending on solar altitude. The sea, mountains, and urban horizons influence the observed appearance by reflecting light and shaping silhouettes. In some cases, volcanic eruptions or wildfires create dramatic sunsets with intensely saturated colors.

Sunsets have a prominent place in culture and art, often symbolizing endings, transitions, or beauty, and they are a common subject in photography and landscape painting. Observational considerations include an unobstructed western horizon, atmospheric clarity, and the time window when the afterglow remains visible.