Midnight sun

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The midnight sun is the term used to describe the sun when it is visible above the horizon in areas north of the northern and southern Arctic Circle in summer even at the lowest point of its daily orbit in the sky ( midnight ) .

Midnight sun at the North Cape

description

Observed from a location directly on the Arctic Circle, the sun does not set once a year - at the time of the respective north or south summer solstice . After it has reached its lowest point above the horizon in the course of the day , it rises again. On June 21, the sun in the Arctic Circle is in the east in the morning and rises until it reaches its highest point in the south at noon. Then she descends again, stands in the west in the evening and touches the horizon in the north at midnight.

Now the further you get during the period around the summer solstice from the Arctic Circle from the north pole approaches (or from the Antarctic from the South Pole ) to the more days of operation of the midnight sun can be observed. Since the sun does not sink below the horizon, it is called polar day . The polar day should last half a year directly at the geographical pole . Because of refraction ( refraction ) in the Earth's atmosphere , however, the polar day holds something longer than half a year.

Midnight sun in Norway (from south to north)
place Geographic
latitude		 The top of
the sun
stays about
midnight
from the		 Whole sun
visible 24 hours a day		 The top of
the sun
disappears
about midnight
from		 Polar
night
begins
with
the		 Polar
night
end
Polar circle 66 ° 34 ′ June 5th June 12th - July 1st July 6th - -
Bodø 67 ° 17 ′ 31. May June 4th - July 8th July 12 - -
Svolvær 68 ° 14 ′ 25. May May 28th - July 14th July 18th 7th Dec Jan. 5
Harstad 68 ° 48 ′ May 22 May 25th - July 18th 21 July Dec 2 Jan. 10
Bardufoss 69 ° 04 ′ May 20th May 23 - July 19 22nd of July Nov 30 Jan. 12
Andenes 69 ° 19 ′ May 19th May 22nd - July 21st July 23 Nov 29 Jan. 13
Tromso 69 ° 39 ′ May 18 May 20th - July 22nd July 25th Nov 27 Jan. 15
Bossekopp 69 ° 57 ′ May 16 May 19 - July 24 July 26th Nov 25 Jan. 17
Vardø 70 ° 22 ′ May 15 May 17th - July 26th July 28th 23 Nov Jan. 19
Hammerfest 70 ° 40 ′ May 13th May 16 - July 27 29th of July Nov 22 Jan. 20
Berlevåg 70 ° 44 ′ May 13th May 15 - July 28 30th July Nov 21 Jan. 21
North Cape 71 ° 10 ′ May 11th May 14th - July 29th July 31 Nov 20 Jan. 22
Jan Mayen 70 ° 59 ′ 12th of May May 14th - July 28th 30th July Nov 20 Jan. 21
Bear Island 74 ° 30 ′ April, 30th May 1st - Aug 10th Aug 12 Nov 7 Feb 4
Hops 76 ° 33 ′ April 23 April 25th - Aug 17th Aug 18 Oct 31 Feb 10
Svea 77 ° 54 ′ April 19th April 21st - Aug 21st 23 Aug Oct. 27 Feb 15
Barentsburg 78 ° 04 ′ April 19th April 20 - Aug 21 23 Aug Oct 26 Feb 15
Longyearbyen 78 ° 13 ′ April 18 April 20 - Aug 22 24 Aug Oct 26 Feb 16
Pyramids 78 ° 39 ′ 17th April April 19 - Aug 23 25 Aug Oct 25 Feb 17
Ny-Ålesund 78 ° 55 ′ April 16 April 18 - Aug 24 25 Aug Oct. 24 Feb 18
Magdalenefjord 79 ° 34 ′ April 14th April 16 - Aug 26 27 Aug Oct. 22 19 Feb
Rossøya 80 ° 50 ′ 11 April April 12th - Aug 29th 31 Aug 19 Oct 23 Feb
North Pole 90 ° 00 ′ March 18th March 20 - September 23 Sept. 24 Sept 25 March 18th

Celestial mechanics

The different day and night lengths on all latitudes of our earth are caused by the axial position of our earth to the ecliptic , the earth orbit plane . Our earth's axis is not perpendicular to the plane of its orbit, but has an angle of inclination of currently around 23.43 degrees. If the earth's axis were perpendicular to the plane of the earth's orbit, then the sun would always move exactly along the horizon at both poles all year round. In fact, this only happens twice a year for a short time: at the astronomical beginning of autumn and spring .

Midnight sun
Polar day near Skibotn

Conceptual classification

The term midnight sun quickly leads to the misconception that the sun always reaches its lowest point at midnight. Due to various phenomena at a certain location, this is only approximately the case:

  • On the one hand, the time of the lowest point of the sun depends on the longitude of the location, because a time zone defines the mean solar time of a certain degree of longitude as the time applicable there; but this for a whole range of degrees of longitude (e.g. 15 degrees of longitude). At the edge of a time zone, the mean solar time can be increased by e.g. B. 30 minutes deviate from the time zone (this deviation remains constant throughout the year).
  • On the other hand, the true solar time for a given location fluctuates by around plus / minus a quarter of an hour over the course of the year (phenomenon of the equation of time ). One of the reasons for this is that the earth orbits the sun at varying speeds because of its slightly elliptical orbit.
  • In addition, with a daylight saving time regulation, the true midnight is shifted by another hour.

At the North Cape , the midnight sun reaches its lowest level on average at 11:17 p.m. CET or 12:17 p.m. CEST and can be observed here from May 11th to July 31st, while on Svalbard the midnight sun can be observed from April 20th to 25th. August can watch.

Individual evidence

  1. ↑ Sola skinner døgnet rundt (The sun shines all day) - Report to yr.no from May 20, 2009, accessed on May 21, 7 p.m. ( Bokmål )

Web links

Commons : Midnight sun  - collection of images, videos, and audio files