The reduction in the duration of daylight hours in the autumn-winter period affects the deterioration of well-being and the weakening of human immunity, the change from the upswing phase to the downturn phase in all life cycles, an increase in the expenditure side of countries' budgets, and the suspension of seasonal work in a number of sectors of the economy (agriculture, construction and others).
The winter solstice marks the minimum daylight hours. On this day, the Sun crosses the farthest point of the ellipse along which the Earth rotates. This day for residents of the northern hemisphere of our planet occurs on December 21-22, while at the same time, for residents of the southern hemisphere, the summer solstice day of maximum duration begins.
Sunlight promotes the production of the hormone serotonin in the human body, which causes emotions of joy and happiness. With short daylight hours, the production of serotonin is reduced, which depresses the emotional sphere of the body and leads to a deterioration in its condition. The equal length of day and night on the days of the autumn and spring equinoxes creates ideal conditions for daily biorhythms. The period of the cycle, beginning on the day of the autumn equinox and ending on the day of the winter solstice, represents the stage of reduction of daylight hours in the phase of its lag from the duration of the night. This stage is the most unfavorable; during it, all life on Earth is increasingly oppressed. The second stage, starting on the day of the winter solstice and ending on the day of the spring equinox, is also in the phase of the lag between daylight and night, but this lag is gradually decreasing, the negative impact of the lack of sunlight is gradually weakening. The less sunlight a person receives per day, the more susceptible he is to nervous breakdowns, including depression and mental disorders. Technical civilization is trying to compensate for the lack of sunlight with artificial lighting, to which the human body is not adapted; it perceives artificially illuminated night hours as daylight hours, falling into the so-called state of desynchronosis, which aggravates chronic diseases.
At the same time, the population of the northern hemisphere is less affected by the changing seasons than the population of the southern hemisphere, because In winter, the northern hemisphere is closer to the Sun. The period from sunrise to sunset is called the length of the day. This value depends on geographic latitude. At the equator, the length of the day is a constant of 12 hours. In the northern hemisphere, in the autumn-winter period, the length of the day is less than 12 hours, and in the spring-summer period, it is more than 12 hours. At the Earth's poles, polar day and night last six months. Given the importance of day length, daily and monthly average day length tables have been compiled for each latitude.
For example, the minimum average monthly day length at the latitude of Moscow is 7 hours 16 minutes in December and 7 hours 51 minutes in January.
From this article you will learn when the summer and winter solstices, as well as the autumn and spring equinoxes, occur.
The shortest and longest days throughout the year are called solstice days, which are summer and winter, and the time when days and nights are equal is equinoxes, spring and autumn. Let's find out more about these days.
When, in what month in winter, will daylight hours begin to profit and begin to grow?
Mid-latitude winter solstice in RussiaThe shortest day in winter is winter solstice– we’ll be there on December 21 or 22. On one of these days, the shortest day of the year, in the northern hemisphere, in the middle latitudes, it lasts 5 hours and 53 minutes, then the day will increase and the night will decrease.
The closer to the Arctic Circle, the shorter the day. Beyond the Arctic Circle, the sun may not appear at all at this time.
Attention. According to the old style, the winter solstice coincided with Christmas. In the old days, this time was highly revered: they decorated their home festively, prepared kutia from wheat, and baked pies and gingerbreads from the flour of the new harvest. For the New Year and Christmas holidays, they fed spring and summer animals (pig, calf) in order to slaughter them for the Christmastide and prepare delicious meat dishes.
At the equator, day all year round is the same in length as night (12 hours).
As for the southern hemisphere, everything is different there: when we, in the northern latitudes, have the winter solstice, they have the summer solstice.
This is interesting. The winter solstice was first established by Julius Caesar. This happened in 45 BC. Then this day was December 25th.
When, on what date, does the shortest day and the longest night of the year occur, and how long does it last?
The longest day at mid-latitude in Russia and Ukraine The longest day occurring in a year ( summer solstice) occurs on June 20, but may occur on June 21 or 22 (depending on the shift in the calendar due to leap year). For Moscow, the length of the day is 17 hours 33 minutes, and then the days begin to get shorter and the nights longer.
How can we explain the summer solstice? This is the day when the sun reaches its highest point above the horizon at noon. After this day the sun begins to go down and this continues until December 21st or 22nd.
In ancient times, the following beliefs were associated with this day:
- At this time, healers collected medicinal herbs, since the greatest beneficial properties of plants are manifested right now.
- On the night after the summer solstice, the girls cast a spell on their betrothed, and he would certainly show up.
- From this day on, it was possible to swim in reservoirs, but previously it was prohibited, since, according to legend, devils sat in the water. From this day they left for a short time, until the holiday of Elijah (August 2).
Note. According to the old style, the summer solstice coincided with Midsummer's Day.
How much will daylight increase after December 22?
The shortest day in winter in central Russia The shortest day is considered to be December 21 or 22, but in fact the next few days are the same length, and only on December 24-25 the day is added.
At first, the increase in day is imperceptible, since it increases by 1 minute, and then in the evening, and in the morning the sun rises even later, and then the increase in day is noticeable, and on March 20-22, the day becomes the same size as the night, about 12 hours.
Interesting. But on other planets of our Universe, the length of the day on some planets is similar to the Earth’s day, on others it is completely different. Length of day on other planets(in Earth hours):
- Jupiter – 9 o'clock
- Saturn - close to 10 o'clock
- Uranus - close to 13 hours
- Neptune - close to 15 hours
- Mars - 24 hours 39 minutes
- Mercury is close to 60 of our days
- Venus – our 243rd day
From what day do days become longer than nights?
Spring equinox in central Russia After the day spring equinox, which occurs from March 20 to March 22 (differently each year, due to the leap days), the day becomes longer than the night.
The Slavs associate the holiday of the Forty Saints with the day of the spring equinox. On this day, birds (larks) were baked from butter dough, and they called out for spring, and with it, from distant lands, the first birds.
In many Asian countries (former Soviet republics in Central Asia, Afghanistan, Iran), the day of the vernal equinox is the New Year.
In Russia (middle latitude), from the days of the equinox and solstice, it is customary for people to start countdown And time of year:
- Spring – from the 20th of March to the 20th of June
- Summer – from the 20th of June to the 20th of September
- Autumn – from the 20th of September to the 20th of December
- Winter – from the 20th of December to the 20th of March
When is the longest day and shortest night of the year, and how many days are they?
The longest day of the year in central Russia The longest day in 2017 occurred on June 21. For several days, the days were just as long (17 hours 33 minutes), and from June 24 the days began to decrease.
When, from what date in the summer, will daylight hours begin to decrease?
The day has been decreasing since June 24 If we take data for Moscow, then the longest day was 17 hours 33 minutes.
For Moscow, the days will decrease in the following sequence:
- By the end of June, the day decreased by 6 minutes, and became 17 hours 27 minutes
- For July - by 1 hour 24 minutes, day length 16 hours 3 minutes
- For August - by 2 hours 8 minutes, the day lasts 13 hours 51 minutes
- Until the equinox (September 24), the day will shorten by 1 hour 45 minutes, the length of the day will be 12 hours 2 minutes
When does the night become longer than the day?
Autumn equinox day occurs from September 21 to 23, when the day is the same length as the night, about 12 hours. After this day, the night begins to increase and the day decreases.
After the equinox, the length of the day decreases even more:
- At the end of September the day lasts 11 hours 35 minutes
- During October, the day will decrease by 2 hours 14 minutes, and at the end of the month it will be 9 hours 16 minutes
- During November, the day decreases less intensively, by 1 hour 44 minutes, the length of the day is 7 hours 28 minutes
- Until the winter solstice (December 21), the day will decrease by 28 minutes, the length of the day will be 7 hours, and the night will be 17 hours.
It is noteworthy that on days equal in length to the nights (autumn and spring equinoxes), the sun rises exactly in the east and sets exactly in the west.
So, we found out when the longest and shortest days of the year are.
Video: Days of solstices and equinoxes
Changes in the length of daylight hours in different seasons are explained by the rotation of the Earth around its axis. If the Earth did not rotate, the day and night cycles would be completely different. Although, it is likely that they would be completely absent. Whether daylight hours shorten or increase depends on the time of year and where you are on Earth. In addition, daytime is affected by the angle of the Earth's axis and its path around the Sun.
Rotation duration
A 24-hour day is the time it takes for the Earth to complete a full revolution on its own axis, which is why the Sun appears in the same place in the sky the next day. However, do not forget that the Earth continues to move around the Sun, and this phenomenon has a huge impact on the length of daylight hours.
The actual time of one rotation of the Earth is somewhat shorter than we used to think: about 23 hours and 56 minutes. Astronomers discovered this by recording the time a star appeared in the same place in the sky the next day - a phenomenon called a star day.
Longer and shorter days
Although a solar day is 24 hours long, not every day contains 12 hours of daylight and 12 hours of darkness. In winter the nights are longer than in summer. This phenomenon is explained by the fact that the imaginary axis of the Earth is not located at a right angle: it tilts at an angle of 23.5 degrees. Actually, as our planet orbits the Sun throughout the year, the northern half of the Earth tilts toward the Sun in the summer, causing long daylight hours and short nights. In winter, this changes: our planet moves away from the Sun, and night time becomes longer. In spring and autumn, the Earth is neither tilted towards the Sun nor away from it, but somewhere in between, so day and night are the same at these times of the year. Here's how you can explain why the length of daylight hours increases in spring: our planet turns towards the sun!
Our number of daylight hours depends on our latitude and the fact of what the Earth's position is in relation to the Sun. The axis of rotation of our planet is inclined from the orbital plane and is always located in one direction - towards the polar star. As a result, the position of the earth's axis in relation to the sun constantly changes throughout the year.
Actually, it is this factor that influences the propagation of sunlight across the Earth’s surface at any given latitude.
Changing the angle changes the amount of solar energy that reaches certain areas of the planet. This causes a seasonal change in the intensity of sunlight reaching the surface and affects the length of daylight hours.
The change in intensity occurs because the angle at which rays from the Sun travel and hit Earth changes as the seasons change.
Let's prove it in practice
If you shine a flashlight on the ceiling, the area illuminated will change depending on whether you shine the light at a right angle or not. Similarly, the energy of the Sun spreads across different geographical areas when it reaches the surface of the Earth. It is more concentrated in our summer months when the sun is higher in the sky.
Between the summer and winter solstice, the number of daylight hours decreases, and the rate of decrease is greater the higher the latitude. The fewer hours of sunshine, the colder the nights. This is why the length of daylight in the spring increases: the planet gradually turns towards the Sun, absorbing more and more solar energy on one of its sides.
Since, parallel to its rotation around the Sun, the Earth also continues to rotate around its own axis, it makes one full revolution in 24 hours. Interestingly, the length of the day changes over time. So, about 650 million years ago, the day lasted about 22 hours instead of the usual 24!
Solstice
Solstice is a phenomenon when, at a certain position in the Earth's orbit, the longest and shortest days of the year are marked. The winter solstice, occurring in the Northern Hemisphere, marks the shortest day, after which daylight hours begin to slowly increase. The summer solstice in the same hemisphere occurs during the longest daylight hours, after which it begins to get shorter. The solstice is also named after the month in which it occurs.
It is also important to understand that the length of daylight on the solstice depends on the hemisphere in which you are located. Thus, in the Northern Hemisphere, the June solstice marks the longest daylight hours of the year. While in the Southern Hemisphere, the June solstice marks the longest night.
