Life on our planet depends on the amount of sunlight and heat. It is terrible to imagine even for a moment what would happen if there were no such star as the Sun in the sky. Every blade of grass, every leaf, every flower needs warmth and light, like people are in the air.
The angle of incidence of the rays of the sun is equal to the height of the sun above the horizon
The amount of sunlight and heat that enters the earth's surface is directly proportional to the angle of incidence of the rays. The sun's rays can fall to the Earth at an angle from 0 to 90 degrees. The angle of the rays hit the earth is different, because our planet has the shape of a ball. The larger it is, the brighter and warmer.
Thus, if the beam goes at an angle of 0 degrees, it only glides along the surface of the earth without heating it. This angle of incidence occurs at the North and South poles, beyond the Arctic Circle. At right angles, the sun's rays fall on the equator and on the surface between the South and North Tropics.
If the angle of sunlight on the earth is straight, this indicates that the sun is at its zenith.
Thus, the angle of incidence of the rays on the surface of the earth and the height of the sun above the horizon are equal. They depend on geographical latitude. The closer to zero latitude, the angle of incidence of rays closer to 90 degrees, the higher the sun is above the horizon, the warmer and brighter.
As the sun changes its height above the horizon
The height of the sun above the horizon is not a constant. On the contrary, it always changes. The reason for this lies in the continuous movement of planet Earth around the star Sun, as well as the rotation of planet Earth around its own axis. As a result, day is replaced by night, and the seasons of each other.
The territory between the tropics receives the most heat and light, here day and night are almost equal in duration, and the sun is at its zenith 2 times a year.
The surface beyond the Arctic Circle receives less heat and light, here there are concepts such as polar day and night, which last about six months.
Days of the Autumn and Spring Equinox
There are 4 main astrological dates that determine the height of the sun above the horizon. September 23 and March 21 are the days of the autumn and spring equinox. This means that the height of the sun above the horizon in September and March these days is 90 degrees.
The southern and northern hemispheres are equally illuminated by the sun, and the longitude of the night is equal to the longitude of the day. When astrological autumn comes in the Northern Hemisphere, in the Southern Hemisphere, on the contrary, spring. The same can be said about winter and summer. If the southern hemisphere is winter, then the northern hemisphere is summer.
Summer and Winter Solstice
June 22 and December 22 are the days of the summer and winter solstice. December 22 is the shortest day and the longest night in the Northern Hemisphere, and the winter sun is at its lowest altitude over the horizon for the whole year.
Above a latitude of 66.5 degrees, the sun is below the horizon and does not rise. This phenomenon, when the winter sun does not rise to the horizon, is called the polar night. The shortest night happens at a latitude of 67 degrees and lasts only 2 days, and the longest happens at the poles and lasts 6 months!
December is the month of the whole year when the longest nights in the Northern Hemisphere are. People in Central Russia wake up to work in the dark and return, too, in the dark. This is a difficult month for many, as the lack of sunlight affects the physical and moral condition of people. For this reason, depression may even develop.
In Moscow in 2016, the sunrise on December 1st will be at 08.33. The longitude of the day will be 7 hours 29 minutes. Sunset over the horizon will be very early, at 16.03. The night will be 16 hours 31 minutes. Thus, it turns out that the longitude of the night is 2 times greater than the longitude of the day!
This year, the winter solstice is December 21st. The shortest day will last exactly 7 hours. Then the same situation will last 2 days. And from December 24, the day will go to profit slowly, but surely.
On average, one minute of daylight will be added per day. At the end of the month, the sunrise in December will be exactly at 9 o’clock, which is 27 minutes later than December 1st
June 22 is the summer solstice. Everything happens exactly the opposite. For the whole year, on this date, the longest day in duration and the shortest night. This is with regards to the Northern Hemisphere.
In the South, the opposite is true. Interesting natural phenomena are associated with this day. Beyond the Arctic Circle, a polar day comes; the sun does not go beyond the horizon at the North Pole for 6 months. In June, mysterious white nights begin in St. Petersburg. They last from about mid-June for two to three weeks.
All these 4 astrological dates can vary by 1-2 days, since the sunny year does not always coincide with the calendar year. Displacements also occur in leap years.
Sun height and climatic conditions
The sun is one of the most important climate-forming factors. Depending on how the height of the sun above the horizon over a specific area of the earth’s surface changed, the climatic conditions and seasons change.
For example, in the Far North, the rays of the sun fall at a very small angle and only glide along the surface of the earth, not heating it at all. Under the condition of this factor, the climate here is extremely harsh, there is permafrost, cold winters with freezing winds and snows.
The greater the height of the sun above the horizon, the warmer the climate. For example, at the equator it is unusually hot, tropical. Seasonal fluctuations are also almost not felt in the equator area; in these areas there is eternal summer.
