twilights

Twilight denotes the period of partial illumination between day and night, occurring before sunrise and after sunset. It arises when the Sun is below the horizon but its light is scattered in Earth’s atmosphere, creating a dim sky and lingering illumination.

There are three conventional phases defined by how far the Sun is below the horizon: civil twilight (sun 0 to 6 degrees below), nautical twilight (6 to 12 degrees), and astronomical twilight (12 to 18 degrees). Civil twilight is when outdoor activities are typically feasible; nautical twilight allows the horizon to be discernible at sea; astronomical twilight is when the sky is still too bright for most astronomical observations.

The colors of twilight result from scattering of sunlight in the atmosphere and its refraction. The sky commonly shows a range of hues from blue higher in the sky to warm reds and oranges near the horizon. The duration and appearance of twilight vary with latitude and season; at higher latitudes, twilight can last many hours and, in extreme cases, persist for months or lead to continuous twilight near the poles.

In photography and culture, specific moments within twilight—the golden hour and blue hour—are celebrated for their distinctive lighting. The overall duration and character of twilight depend on latitude, season, and local topography, such as mountains or buildings that influence the visible horizon.

In scientific and navigational contexts, twilight times help determine daylight conditions and plan astronomical observations. Twilight ends when the Sun is 18 degrees below the horizon, marking the onset of true night.