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Although civil dawn marks the time of the first appearance of civil twilight before sunrise, and civil dusk marks the time of the first disappearance of civil twilight after sunset, civil twilight statutes typically denote a fixed period after sunset or before sunrise (most commonly 20–30 minutes) rather than how many degrees the Sun is below ...
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.
Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere , when the centre of the Sun 's disc has reached 18° below the observer's horizon . [ 1 ]
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 ...
Crepuscular rays usually appear orange because the path through the atmosphere at dawn and dusk passes through up to 40 times as much air as rays from a high Sun at noon. Particles in the air scatter short-wavelength light (blue and green) through Rayleigh scattering much more strongly than longer-wavelength yellow and red light.
Twilight (both dusk and dawn) is divided into three 6° segments that mark the Sun's position below the horizon. At civil twilight , the center of the Sun's disk appears to be between 1/4° and 6° below the horizon.
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The shadow's fringe appears as a dark bluish to purplish band that stretches over 180° of the horizon [3] [4] opposite the Sun, i.e. in the eastern sky at dusk and in the western sky at dawn. Before sunrise, Earth's shadow appears to recede as the Sun rises; after sunset, the shadow appears to rise as the Sun sets. [3]