Overview

Sunrise is the instant when the upper edge of the Sun first becomes visible above the local horizon as a result of Earth's rotation. It marks the transition from night and the end of morning twilight, and is commonly associated with the direction of the east. Observers distinguish sunrise from earlier stages of dawn, which are defined by progressively increasing sky brightness rather than the Sun itself.

Physical causes and measurement

The apparent time of sunrise depends on geometric position, axial tilt of the planet, the observer's latitude and longitude, and atmospheric effects. Atmospheric refraction bends sunlight so the Sun appears higher than its geometric position; observers commonly apply conventional corrections that account for the Sun's angular radius and typical refraction near the horizon. Local elevation and topography shift the visible horizon and can bring sunrise earlier or delay it compared with a sea-level observer.

Twilight phases and seasonal variation

Before the Sun is visible the sky passes through recognized twilight phases: astronomical, nautical, and civil twilight, each defined by the Sun's angular depth below the horizon. Seasonal change in the Sun's declination, from Earth's axial tilt, alters sunrise times and the Sun's rising direction through the year; near the equinoxes the Sun rises close to due east, while toward the solstices it rises north or south of east.

Observable effects

  • Colors: Scattering of short wavelengths reddens low-angle sunlight, producing warm hues at sunrise.
  • Crepuscular rays and alpenglow: Rays, silhouettes, and indirect illumination result from clouds, aerosols, or terrain shapes.
  • Local variation: Weather, air pollution, and sea spray affect clarity and apparent color.

Practical importance and cultural role

Sunrise has practical uses in timekeeping, navigation, and determining daily schedules. It defines moments used in some religious observances and traditional rituals and is prized in photography for the "golden hour," when light quality is favorable. In polar regions, the Sun may remain above or below the horizon for extended periods, producing polar day or polar night and removing a conventional daily sunrise for months.

Precise language helps: the Sun names the star, while the horizon is the apparent boundary between Earth and sky. Sunrise commonly occurs in the east, follows twilight and night, and ushers in morning. Its opposite event is sunset, when the solar disk disappears below the horizon. Understanding these distinctions is useful in astronomy, meteorology, and everyday life.