Sunset

As sunset is referred to both the disappearance ( destruction ) of the sun below the horizon as well as the timing of this phenomenon in the daily course of the sun and the celestial phenomenon as such, with all its phenomena. On the sunset followed by the time dusk, which is depending on the latitude of different lengths.

The sunset marked the beginning of the day in some cultures, such as the ancient Germans, in Judaism and Islam. The exact definition of the sunset, that is, the days start according to Islamic understanding, also varies according to different schools. Here, Maliki, Shafi'i and Hanafi law have different views; see also Ramadan # The Daily Fast Start and Fast statements. However, most of the contemporary middle-class day begins at sunrise.

Astronomical phenomena

The term sunset is a linguistic relic of the geocentric world view: it is not the sun moves, but the viewer is moved due to the natural rotation of the earth on the day - night boundary on our earth. The opposite phenomenon is the morning sunrise.

The sinking part with sunrise, meridian passage and the culmination of the most important aspects of astronomical phenomenology, which is why all astronomical calendars and yearbooks contain corresponding data for the Sun and Moon. The latest sunset falls because of the equation of time is not on the summer solstice, but only occurs around the 25th of June. Similarly, the earliest sunset in northern Germany already occurs about December 14, one week before the winter solstice, in Switzerland as early as the 11th of December.

The apparent size of the sun varies between 31 ' ( minutes of arc ) and 28 "( seconds of arc ) to the beginning of July and 32'32 " at the beginning of January, so there is a variance of about ± 1.7 % for the year. The mean apparent diameter of the sun is 31'59, 3 ".

Due to the curvature of the light rays ( refraction and Astronomical refraction) in the Earth's atmosphere the solar disk appears lifted by about 0.6 ° and thus larger than it actually is in diameter.

The true sunset is actually defined as the moment at which the upper edge of the solar disk falls below the true horizon. The true horizon or also known as geocentric horizontal plane passes through the center of the earth. Falls below the upper edge of the solar disk the true horizon, this is the moment of sunset.

General advance calculations can not account for real horizon curves of certain locations and expect for an ideal mathematical horizon, located anywhere in the amount of 0 °. For the calculation of such time points, see Sunrise ( astronomy) or visibility ( astronomy).

Where the sinking point is on the horizon, outside the tropics depends strongly on the season. At the equinox he is almost exactly in the west, in December / January, however, for Central Europe as in the Southwest, and in June / July in the Northwest. Thus, the possible direction varies by almost 90 degrees:

• Astronomical Views of sunsets

Added Sunset on the earth from space ( lower left corner of the image )

Sunset on Mars, taken by the Spacecraft Spirit

Sky coloring

Depending on the weather the sinking of the sun can be linked with an impressive combination of colors that sometimes shines not only in the afterglow, but also has yellow, purple or even green hues. The color change caused by Rayleigh scattering. The Earth's atmosphere acts here with their airborne particles ( aerosols in the Peplosphäre ) as diffusely scattering medium, the blue light is always scattered more strongly than red ( This fact is also responsible for the sky blue). The amount of blue light from the sinking sun disc is scattered, so that more red light reaches the observer.

In addition, in certain temperature stratification, a very small prism effect caused by the atmosphere, which can be exhibited by extremely sharp horizon as Green Flash: The red portion of the solar disk first disappears below the horizon, which briefly at the upper edge of the sun, a green seems to flash - blue hem.