The movements of the planets around the sun and their axes cause many amazing, and sometimes inexplicable phenomena. For the first time about the polar night and the polar day, he spoke an ancient Greek astronomer bioon.
Causes of appearance
Earth is located at a distance of about 150 million kilometers from the sun. It moves around the Sun at a speed of 30 km/s, making a full revolution in one earthly year, and at the same time rotates around its axis.
The axis of rotation of the earth is inclined to the plane of its rotation around the sun at an angle of 23 degrees. Despite the fact that the angle of inclination of the earth is constant, it rotates around the sun, so it becomes possible to change the polar night for a day (once every 6 months).
Polar day and polar night are in areas located between poles and polar circles, that is, between 66 degrees of northern latitude and the northern pole and 66 degrees of the south latitude and the southern pole, respectively. These areas between poles and latitudes are called the Arctic. Thus, these astronomical phenomena are characteristic of the Northern Arctic and Southern Arctic.
Polar day
Presents a time period, for example, from March 18 to September 26 at the North Pole and from September 21 to March 23 at the South Pole, when the sun does not go beyond the horizon, but describes circles along its line.
Duration
The longest polar day was recorded at the North Pole and is 190 days. At the South Pole, the polar day lasts 184 days. In general, the duration of the polar day, as well as the night, depends on the parallel on which the item is located.
Polar day
Where can you see
The polar day can be observed in all countries whose settlements lie above the northern polar circle. This includes Canada (Inuvik), Norway (Alta, Lekes, Narvik, Hammerfest), Sweden (Kirun), Finland (Kemiyarva and Rovaniemi). Many cities of Eurasia see a polar day:
polar night
It is a period, for example, from September 25 to March 17 at the North Pole, the time when the sun does not leave due to the horizon.
It is known that the polar night does not come right away, but begins with dusk, which are divided into:
There is also the concept of “complete polar night”, characterized by the inability to see the slightest amount of sunlight. This moment is very valuable for astronomers, because the most remote galaxies become visible. The night in the southern Arctic of the Arctic for 6 days is longer than in the northern. In Norway and Eurasia, the northern lights are adjacent to the polar night. Interestingly, during the polar night, animals fall into hibernation, and plants turn into a state of animation.
polar night
Duration
The polar night, characterized by the smallest duration, occurs at the latitude of the polar circle. The sun, disappearing beyond the horizon for 40 hours, reappears after 2 days. The longest polar night is observed by the south pole.
Where can you see
20% of the territory of Eurasia allow you to see a polar night. In cities such as Vorkuta, Norilsk, Murmansk, Salekhard (located exactly on the line of the northern polar circle), Severomorsk.
The best of places for observing the polar night is in Norway, the city of Longyir.
The polar night covers the northernmost city of the USA Barrow and lasts about 3 months here. Cities of Sweden, Greenland, Finland are in the zone of polar night. In the northern city of the planet (Canada Alert) comes the longest polar night (5 months).
Solstice and equinoxes
In the days of the equinox, both poles of the globe are illuminated the same, the duration of the day is equal to the night. Select the spring (March 21) and autumn (September 23) equinox. On the day of the spring equinox, the sun goes into the southern hemisphere. On the day of the autumn equinox, the sun goes into the northern hemisphere.
Winter solstice is accompanied by the longest night and the shortest day, falls on December 22.
Summer solstice has the longest day and the shortest night. It can be observed on June 21.
The effect on the body of a polar night and polar day
The human body sometimes also does not withstand such loads that arise as a result of a lack of solar radiation, since the metabolic processes responsible for the production of serotonin. The response to such changes is the development of depression and apathy.
Often the lack of sun ultraviolet irradiation leads to a lack of vitamin D in children and adults.
During the polar day in the body, the production of melatonin is disturbed, since this hormone is produced during sleep in the dark. It is produced by the epiphysis of the brain, provided that the complete darkness. The lack of biologically active substance leads to increased nervous excitability, anxiety, a decrease in the body’s immune forces. So in the case of a polar day, constant sunlight is far from an assistant to health.
Studies of the Jerusalem clinic confirmed the negative influence of the polar night on the female reproductive system, associated the lack of solar radiation with the locking of ovulation mechanisms.
The period associated with the polar night and the polar day is difficult, young children who often disrupt sleep, nutrition and wakefulness. The occurrence of sleep inversion is characteristic when it is impossible to fall asleep in the evening, and wake up in the morning.
Polar night in Murmansk
Prevention of the negative effects of the polar day and polar night
It is very important for people who are constantly living in the conditions of such astronomical phenomena to carry out some preventive measures to prevent pernicious effect on the body. These include:
