Polar day - polar night

It is not easy to imagine that a day of light lasts more than 24 hours, that it does not change at night and the street is constantly light. Or, on the contrary, all the time, night, darkness, cold. But so it is beyond the inner boundaries of the polar circles.

The polar day is the period during which the Sun is above the horizon and does not enter it for more than one day. This phenomenon can be observed in the polar regions located to the north of the Arctic Circle and south of the Southern Arctic Circle.

A polar day is possible due to the inclination of the plane of the equator of the Earth relative to the plane of the ecliptic by approximately 23 ° 26 '. It lasts almost two days on polar circles and increases the duration at higher latitudes to 186 days at the poles. The shortest is at a latitude of about 65 ° 43 '. The longest is at the North and South poles. There its duration reaches six months. At the North Pole, it begins on March 17 and lasts until September 25. And at the South Pole continues approximately from September 20 to March 22. During the polar day, the sun does not set every day beyond the horizon, but makes the circle parallel to the horizon line. In addition, the phenomenon of refraction allows us to observe the presence of the sun simultaneously on both poles for several days in a row before and after the equinoxes.

Near the outer side of the polar circles there is a polar night. At this time in the sky there is no Sun more than a day. The boundary of a constant night near the northern polar circle is approximately at a latitude of 73 ° 5 'to the South. Such a night can last a maximum of 178 days.

The beginning and duration of polar days and nights are different for different settlements. Also, they have different weather conditions. This is due to their location at a certain geographical latitude. For example, in the north, in Zapolyarnoe, the polar night lasts from November 30 to January 13; In Murmansk begins on December 2, and ends on January 11; Polar Zori (the weather is very harsh in winter) is met on December 21, and on the 23rd of the same month.

As we have already seen, these phenomena have a duration of approximately 186 - 178 days, that is, at poles six months last a day, six months - a night. And these periods determine the weather conditions on the terrain. There are no four seasons of the year, but only conventionally divided summer (on a polar day) and winter (when the polar night comes). And what happens to our planet during such periods?

In the summer, one of the poles of the Earth faces the Sun and does not go into shadow, despite the rotation of the planet around its axis. On this site - a polar day. But he is not the same as we used to see him. After all, it can not be called a part of the day, because it lasts six months. Since the pole is directed towards the luminary, accordingly, the Sun does not hide behind the horizon, but moves along it.

At the opposite pole, the situation is quite different. Since at this time he is almost half a year in the shadows, it is a constant night. The sun does not show above the horizon.

Shortly before the onset of the polar day on the "dark" pole there is a fascinating phenomenon of nature - the northern lights. When it arises, it becomes lighter around, as in the full moon. Northern lights are just an optical effect, but what an exciting one! How many people want to see him live at least once!

The Northern Lights appear in the upper layers of the atmosphere due to the interaction of the Earth's magnetic field with cosmic particles. This glow of air at an altitude of 60 to 1000 km in the form of arc-shaped rays, curtains, crowns. It can be seen on the poles of both hemispheres, but with varying intensity, depending on the longitude. It lasts from several minutes to several days and can appear at different times of the year only in the night sky.