Daily habitually divided into day, evening, night and morning. And from the point of view of astronomy, few people think about what caused this phenomenon.
And why is it that the sun shines so little in winter, creating the feeling that night falls at four to five in the afternoon.
Daylight and Astronomical: Differences
The revolution of our planet around its so-called axis takes 24 hours. This is an astronomical day, which is divided into two parts: day and night. Half, that is 12 hours, is an astronomical day. Its time and ending is not fixed anywhere.
Daylight - this is the period of time that begins with sunrise and ends with its departure for the horizon. Therefore, the second name is a sunny day. Duration changes every day. And there is not a single day when the sun illuminates the earth for an equal amount of time. Just a second, but different.
By the way, often such information was printed on tear-off calendars that used to be hung in every house. Confirmation of this fact is now easy to find on the Internet.
Day Length Factors
The angle of the Earth to the Sun is 23.5 degrees, which is the main explanation for the short days in winter. In hot time, the heavenly luminary on the horizon lingers for a long time, warming the surface. But in winter everything happens exactly the opposite. The planet deviates from the star, so the sun's beam and hit the earth indirectly and for a short time.And when it rains or is cloudy, it even seems that the day ends before it starts.
By the way, beyond the Arctic Circle, the Sun passes along the horizon, which entails darkness. This phenomenon is called polar night. On the other conventional line - the equator - the light and astronomical days are almost equal and their duration is about 12 hours.
Considering that the Earth rotates around its axis at the same time as the revolution around the Sun, when winter comes in the northern hemisphere, the day decreases. The division of the Earth from pole to pole, into the eastern and southern hemispheres, entails such a thing as a change of time zones.
Winter solstice, or the shortest day
On December 21 or 22 of each year, the inclination of the earth's axis with respect to the Sun reaches the greatest angle. This astronomical phenomenon is called the solstice (solstice) and is characterized by the shortest, 8-hour day of the year. But from this moment on, night time gradually becomes shorter. In the southern hemisphere, the date of the winter solstice is June 20 or 21.
For the first time in Europe, this phenomenon was established by Julius Caesar. In the Julian calendar, the date of the winter solstice was December 25th. It happened in 45 BC. The difference between the tropical and the calendar year led to the fact that by the middle of the 16th century it was December 12th.
The end of the confusion was laid in 1582 by Pope Gregory XIII. And since then, in the Gregorian calendar, the longest night falls on December 21 or 22. It is believed that a shift may occur for another day. But this is allowed with an interval of 3000 years.
The duration of the day in winter is affected by the position of the Sun relative to the Earth. Since the planet moves around its axis, the day comes gradually in latitude. The farther the area is from the equator, the shorter is the cold daylight hours, and beyond the Arctic Circle of the northern hemisphere a whole night sets in.
