Why does the day increase in spring and decrease in autumn? What is daylight

As for the duration of the time of day, it is, of course, not constant. Basic astronomical laws contribute here. Cosmic time differs from earthly time, but it is not so subject to change. That is, it is relative. It turns out that how much time lasts in a day during daylight hours is usually divided on our planet into two intervals. This is from 7 am to 11 pm. This is the period of activity of the largest part of the planet's population. And also from 18 pm to 23 pm - this is the time that is actively used after the end of the working day.

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About daylight hours

So, 17 hours and 34 minutes is the answer to the question of how many hours and minutes the daylight hours last on June 22, 2017. But what kind of indicator is daylight hours, what does it depend on and how is it formed? We suggest you look into it in more detail.

Daylight hours are the period of rotation of our planet around its axis. When one part of the planet is turned towards the sun, then during this period it will be light in the countries. On average, daylight hours total 4,507 hours throughout the year. But in every country different time This duration will vary from year to year. Often in winter time day in our country, in particular, daylight hours are only 5 hours, but in the summer it can reach up to 17 hours. The longest day is June 22.

Interesting! In Tokyo, where nine hours are added to world time, the annual duration of daylight hours is equal to 4175 hours, but in Beijing it is already 4377 hours, in Minsk it is already 4578 hours, as well as in Moscow (due to last cancellation time change).

Remember that our planet revolves around the sun in an elliptical, not a circular orbit. That is, the planet either approaches the sun or moves away from it. To this we must add the constantly changing acceleration. Our planet reaches its maximum proximity to the sun somewhere on January 2-3, during this period it has maximum acceleration. For the same reason, due to rapid movement, less light reaches the earth than usual during the year.

During this period, our planet does not have time to warm up. When the Earth rotates slowly and is far from the Sun, it receives more sunlight and, accordingly, daylight hours also last longer.

Four sectors identified in the ecliptic:
About degrees at the Spring Solstice.
90 degrees during the Summer Solstice.
180 degrees at the Autumn Solstice.
270 degrees at Winter Solstice.

Interesting! In Moscow, as in other cities around the world, the length of daylight hours depends on the time of year. If we consider the average for the year, it is 12 hours and 15 minutes.

The average length of daylight in the capital, if we consider it by month from the beginning of the year:
1. Eight hours and the same number of minutes.
2. Daylight hours increase to 9 hours and 37 minutes.
3. There is a further increase in daylight hours to 12 hours and 15 minutes.
4. In April, daylight hours increase by another two hours and are already 14 hours and 32 minutes.
5. In May this figure is 16 hours and 34 minutes.
6. In June, the longest day of the year is June 22, with an average of 17 hours and 54 minutes. That is, almost 18 hours, which is extremely long.
7. In July, the number of hours of daylight gradually but surely decreases. While we are talking about minutes, this is 17 hours and 8 minutes.
8. In the last month of summer, daylight hours become 14 hours and 45 minutes.
9. In September, daylight hours are reduced to 12 hours.
10. Next comes 10 hours and 26 minutes.
11. In November there is a reduction of another two hours, 8 hours and 45 minutes will be the average.
12. In December, the average is 7 hours and 49 minutes.

The benefits and necessity of sunlight for the human body are not in doubt. Any of us knows that without it it is impossible to exist. In winter, we all experience a more or less severe deficiency of it, which negatively affects our well-being and undermines our already unstable immunity.

What happens to daylight hours?

With the onset of the cold season, the duration of which is rapidly decreasing, rights are increasingly being ceded. The nights become longer and longer, and the days, on the contrary, become shorter. After the period winter equinox the situation is beginning to change in the opposite direction, which most of us are looking forward to. Many people want to accurately navigate the length of daylight hours now and in the near future.

As is known, the number of daylight hours in a day begins to increase at the end of the so-called winter solstice. At its peak, daylight hours are recorded annually, the duration of which is the shortest. WITH scientific point From a perspective, the explanation lies in the location of the sun at precisely this time at the most distant point in the orbit of our planet. This is influenced by the elliptical (i.e. elongated) shape of the orbit.

In the northern hemisphere it happens in December and falls on the 21st-22nd. A slight shift in this date depends on the dynamics of the Moon and shifts in the Earth. At the same time, the southern hemisphere is experiencing a reverse period summer solstice.

Daylight hours: duration, timing

A few days before and after the date of each solstice, the daylight does not change its position. Only two or three days after the end of the darkest day does the light period begin to gradually increase. Moreover, at first this process is practically invisible, since the increase occurs only for a few minutes a day. In the future, it begins to brighten faster, this is explained by an increase in the speed of solar rotation.

In fact, the increase in the length of daylight hours in the northern hemisphere of the Earth begins no earlier than December 24-25, and it occurs until the date of the summer solstice. This day alternately falls on one of three: from June 20 to June 22. Increasing daylight hours has a noticeable positive effect on people's health.

According to astronomers, the winter solstice is considered the moment the sun reaches its lowest angular height above the horizon. After it, for several days the sun may begin to rise even a little later (by a few minutes). An increase in the length of daylight hours is observed in the evenings and occurs due to an increasingly later sunset.

Why does this happen

This effect is also explained by the increase in the speed of the Earth's movement. You can verify this by looking at the table showing sunrises and sunsets. As astronomers say, the day increases in the evening, but unevenly on both sides. The graph of daylight hours gives a clear idea of ​​the dynamics of this process.

Every day the sunset shifts by a few minutes. Accurate data can be easily tracked using the appropriate tables and calendars. As scientists explain, this effect is caused by a combination of the daily and annual movements of the sun across the sky, which is slightly faster in winter than in summer. In turn, this is caused by the fact that, revolving at a constant speed around its own axis, the Earth in winter is located closer to the Sun and moves in orbit around it a little faster.

The elliptical orbit along which our planet moves has a pronounced eccentricity. This term denotes the amount of elongation of an ellipse. The point of this eccentricity that is closest to the Sun is called perihelion, and the most distant point is called aphelion.

Kepler's laws state that a body moving in an elliptical orbit is characterized by maximum speed at those points that are as close as possible to the center. That is why the movement of the sun across the sky in winter is slightly faster than in summer.

How does the Earth's orbit affect climate?

According to astronomers, the Earth passes the perhelion point on approximately January 3, and aphelion on July 3. It is possible that these dates may change by 1-2 days, due to the additional influence of the Moon's movement.

The elliptical shape of the Earth's orbit also affects climate. During winter in the Northern Hemisphere, our planet is located closer to the Sun, while in summer it is further away. This factor makes the difference between climatic seasons our northern hemisphere.

At the same time, in the Southern Hemisphere this difference is more noticeable. As scientists have established, one revolution of the perihelion point occurs in approximately 200,000 years. That is, in about 100,000 years the situation will change to the exact opposite. Well, we'll wait and see!

Give me sunshine!

If we return to current problems, the most important thing for us is the fact that the emotional, mental and physical state of the inhabitants of the Earth improves in direct proportion to the increase in the duration of daylight hours. Even a slight (several minutes) lengthening of the day immediately after the winter solstice has a serious moral effect on people tired of the dark winter evenings.

From a medical point of view, the positive effect of sunlight on the body is explained by an increase in the production of the hormone serotonin, which controls the emotions of happiness and joy. Unfortunately, it is produced extremely poorly in the dark. That is why increasing the duration of the light interval by influencing the emotional sphere leads to a general improvement in well-being and strengthening of human immunity.

A significant role in the sensations of each of us is played by daily internal biorhythms, which are energetically tied to the alternation of day and night that has continued since the creation of the world. Scientists are confident that our nervous system can work adequately and cope with external overloads only by regularly receiving a very specific dose of sunlight.

When the light is not enough

If there is not enough sunlight, the consequences can be very sad: from regular nervous breakdowns to serious mental disorders. With an acute lack of light, a real depressive state can develop. And seasonal ones, which are expressed in depression, bad mood, general decrease emotional background observed all the time.

In addition, modern city dwellers are subject to another misfortune. Daylight hours, which are too short for modern city life, require adjustment. We are talking about a huge, often excessive amount of artificial lighting, which almost any resident of a metropolis receives. Our body, unadapted to such amounts of artificial light, is capable of getting confused in time and falling into a state of desynchronosis. This leads not only to weakening nervous system, but also to the exacerbation of any existing chronic diseases.

What is the length of the day

Let us now consider the concept of day length, which is relevant for each of us in the first days after the winter solstice. This term refers to the period of time that lasts from sunrise to that is, the time during which our luminary is visible above the horizon.

This value is directly dependent on solar declination and geographical latitude points where it needs to be determined. Near the equator, the length of the day does not change and is exactly 12 hours. This figure is borderline. For the northern hemisphere, in spring and summer the day lasts longer than 12 hours, in winter and autumn - less.

Autumn and spring equinox

Days when the length of the night coincides with the length of the day are called days spring equinox, or autumn. This happens on March 21 and September 23 respectively. It is clear that the length of the day reaches its highest figure at the moment of the summer solstice, and the lowest - on the day of the winter.

Beyond the polar circles of each hemisphere, the length of the day goes off scale in 24 hours. We are talking about a well-known concept. At the poles, it lasts for as long as six months.

The length of the day at any point in the hemisphere can be determined quite accurately using special tables containing calculations of the length of daylight hours. Of course, this figure changes daily. Sometimes, for a rough estimate, it uses such a concept as the average length of daylight by month. For clarity, let’s consider these figures for the geographical point where the capital of our country is located.

Daylight hours in Moscow

In January, daylight hours at the latitude of our capital average 7 hours 51 minutes. In February - 9 hours 38 minutes. In March its duration reaches 11 hours 51 minutes, in April - 14 hours 11 minutes, in May - 16 hours 14 minutes.

For three summer months: June, July and August - these figures are 17 hours 19 minutes, 16 hours 47 minutes and 14 hours 59 minutes. We see that June days the longest, which corresponds to the summer solstice.

In autumn, daylight hours continue to decrease. In September and October, its duration is 12 hours 45 minutes and 10 hours 27 minutes, respectively. The last cold dark days - November and December - are famous for their record short light days, the average day length of which does not exceed 8 hours 22 minutes and 7 hours 16 minutes, respectively.

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Length of daylight

The length of daylight determines the annual cycle, which governs all life on planet Earth. At the same time, as the length of daylight hours changes, one season changes another: spring is followed by summer, autumn, winter and spring again. This dependence can be seen especially clearly in the example of plants. In the spring, as the length of daylight increases, sap flow begins in them; in the summer you can observe their blossoming, in the fall - withering, and in the winter - suspended animation, a sleep similar to death. But, perhaps not in such an obvious form, the length of daylight also affects a person.

The influence of daylight hours on humans

The lack of sufficient natural light also affects the psycho-emotional state. In winter, as well as at the beginning of spring, many people complain of depression, bad mood, headaches, insomnia and irritability. Dysfunction of the nervous system provokes disruptions in the functioning of other organs and systems. The synthesis of natural vitamin D in the body decreases, which entails a decrease in the protective properties of the immune system, therefore total diseases and exacerbations of chronic pathological processes at this time of year are the highest. Doctors advise at the end of winter - beginning of spring to get out into nature at least on weekends, spend more time during the day on fresh air, this will help cope with bad mood and improve overall well-being.