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Twilight occurs according to the solar elevation angle θ s, which is the position of the geometric center of the Sun relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (nearest the horizon), nautical twilight, and astronomical twilight (farthest from the horizon).
The time of dusk is the moment at the very end of astronomical twilight, just before the minimum brightness of the night sky sets in, or may be thought of as the darkest part of evening twilight. [4] However, technically, the three stages of dusk are as follows: At civil dusk, the center of the Sun's disc goes 6° below the horizon in the ...
Dawn begins with the first sight of lightness in the morning, and continues until the Sun breaks the horizon. The morning twilight is divided in three phases, which are determined by the angular distance of the centre of the Sun (degrees below the horizon) in the morning.
Matutinal animals are active only after dawn, and vespertine only before dusk. A number of factors affect the time of day an animal is active. Predators hunt when their prey is available, and prey try to avoid the times when their principal predators are at large. The temperature may be too high at midday or too low at night. [2]
Dusk is the end of evening twilight. [13] Dawn is the beginning of morning twilight. The brightness and color of the sky vary greatly over the course of a day, and the primary cause of these properties differs as well. When the Sun is well above the horizon, direct scattering of sunlight (Rayleigh scattering) is the overwhelmingly dominant ...
Special cases of the Sun-synchronous orbit are the noon/midnight orbit, where the local mean solar time of passage for equatorial latitudes is around noon or midnight, and the dawn/dusk orbit, where the local mean solar time of passage for equatorial latitudes is around sunrise or sunset, so that the satellite rides the terminator between day ...
Earth's terminator as seen from space. A terminator or twilight zone is a moving line that divides the daylit side and the dark night side of a planetary body.The terminator is defined as the locus of points on a planet or moon where the line through the center of its parent star is tangent.
Video Vault – showcasing some public domain content such as old films and select episodes of old shows. Video Vault: Kentucky Edition – showcasing some public domain content involving some Kentuckians with ties to the film industry. Wildcat Insights – magazine program devoted to the University of Kentucky