Midnight sun

As the midnight sun in areas north of the north and south of the Antarctic Circle is called visible sun in the summer at midnight.

Description

Not - from a location directly on the Arctic Circle from observing the sun rises once a year - at the time the North or Südsommersonnenwende. Having successfully achieved in the days running its lowest level over the horizon, it rises up again. The further one is approaching during the period around the summer solstice from the Arctic Circle from the north pole (or the Antarctic Circle in the south pole), to the more days, the process of the midnight sun to watch. As the sun here does not fall below the horizon, one speaks of the polar day. The polar day would directly take six months to the geographic pole. Due to the refraction of light ( refraction) in the atmosphere, however, the polar day lasts a little longer than half a year.

Celestial mechanics

The different day and night length at all latitudes of our planet finds its origin in the axis position of the earth to the ecliptic, the Erdumlaufbahnebene. Our earth's axis is the orbit plane is not vertical, but has an inclination angle of 23.44 degrees. If the Earth's axis perpendicular to Erdumlaufbahnebene, then the sun would wander throughout the year at both poles always exactly along the horizon. In fact, this happens only for a short time twice a year: at astronomical autumn and early spring.

Conceptual framing

The term midnight sun can quickly rise to the error, the sun would reach its lowest level ever at 24:00 clock. This is because of various phenomena in a specific place only approximately true:

• Firstly, the time of the sun lowest values ​​of longitude of the place as the accepted time there depends, because defines a time zone, the mean solar time of a particular meridian; this but a whole range of longitude ( for example, 15 degrees of longitude ). At the edge of a time zone, the mean solar time at eg 30 minutes vary the time zone of the ( this deviation remains constant throughout the year ).
• On the other hand also varies for a given location the true solar time during the year by about plus / minus fifteen minutes ( phenomenon of the equation of time ). Reasons for this is that the Earth orbits the Sun because of its slightly elliptical orbit at varying speeds.
• In addition, shifts in a DST true midnight for another hour.

At Nordkapp the midnight sun reaches its lowest level average clock 23:17 CET or 00:17 GMT clock and is here to observe from 11 May to 31 July, while on Svalbard, the midnight sun already from April 20 to 25 can observe August..