Polar night … Sounds mysteriously and unusually. To observe this phenomenon many people go for the Polar circle. This miracle of the nature can be seen in Severomorsk, Vorkuta, Norilsk, Murmansk and some other cities. Some people say that it is very beautiful, others complain that in Polar night various illnesses become aggravated. What the phenomenon it – is polar night?
Polar night is such period when more than a day the Sun does not leave because of the horizon. At the width of 66 °33' short polar is observed night – it lasts one day. On a pole polar night – the longest, its duration is six months. Scientists explain that polar night – the phenomenon which arises because Earth bends to the ecliptic plane. The tilt angle makes about 23.5 °.
Thus, during polar night the people do not see the Sun in the sky at all. Even then, when on hours the midday and on the street hardly brightens, it is at all not sunlight but only only reflected lights. It should be noted that polar night is not only in northern, but also in the southern hemisphere of the globe. Only the temporary difference between these phenomena makes half a year in the north and in the south.
It is necessary to tell, not polar night causes delight in all people. Many residents of the northern cities expect it with nervousness as during this period their illnesses begin to become aggravated: such, for example, as "jumps" of pressure, cardiovascular insufficiency and some other diseases. It is easy for it to find an explanation: it is rather difficult to organism to adapt to conditions when there is no sunlight throughout a long time. In polar night the doctors recommend to all people to have a rest, not to overtire more, to spend in the fresh air much time, it is obligatory to get enough sleep and to eat properly. Scientists say that there are several types of polar night. So, civil polar night is observed in many cities lying behind a polar circle. The sun, of course, does not ascend, however, at noon the visibility after all improves. Navigation polar night is observed in northern areas – from 72 ° 33' up to 78 ° 33', these are the cities of Dickson, Spitsbergen and some other. Astronomical polar night is celebrated around latitudes from 78 ° 33' up to 84 ° 33', here are recorded astronomical twilight. And here full polar night is the share of latitudes from 84 ° 33' to Northern and Southern poles. Here throughout a long time it is possible to observe some galaxies – and such observations become very valuable to astronomers.