The height of the sun above the horizon: change and measurement. Sunrise in December

Life on our planet depends on the amount of sunlight and heat. It is terrible to imagine even for a moment what would have happened if there had not been such a star in the sky as the Sun. Every blade of grass, every leaf, every flower needs warmth and light, like people 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 of 0 to 90 degrees. The angle of the rays on the ground is different, because our planet has the shape of a sphere. The bigger it is, the lighter and warmer it is.

Thus, if the beam goes at an angle of 0 degrees, it only slides along the surface of the earth without heating it. This angle of incidence is 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 Southern and Northern Tropics.

If the angle of sunlight hits the ground is straight, it means 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 to each other. 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 lighter.

How the sun changes its height above the horizon

The height of the sun above the horizon is not constant. On the contrary, it always changes. The reason for this lies in the continuous motion of the planet Earth around the Sun star, as well as the rotation of the planet Earth around its own axis. As a result, the day is replaced by the night, and the seasons are 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 polar circle receives less heat and light, there are such things as polar day and night, which last about six months.

Days of autumn and spring equinox

Four major astrological dates are identified, which 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 illuminated by the sun in the same way, and the longitude of the night is equal to the longitude of the day. When the astrological autumn comes in the Northern Hemisphere, in the Southern, on the contrary, spring. The same can be said about winter and summer. If the Southern Hemisphere is winter, then in the North there is summer.

Days of summer and winter solstice

June 22 and December 22 - 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 point over the horizon for the whole year.

Above latitude 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 a polar night. The shortest night is at a latitude of 67 degrees and lasts only 2 days, and the longest is at the poles and lasts 6 months!

December is from the whole year that month, when in the Northern Hemisphere the longest nights. 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 in December 1 will be at 08.33. The longitude of the day will be 7 hours and 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 on the 21st of December. The shortest day will last exactly 7 hours. Then the same situation will last for 2 days. And since December 24, the day will go to profit slowly, but surely.

On average, a day of light time 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 1

June 22 is the day of the summer solstice. Everything is exactly the opposite. For the whole year it is on this date the longest day in duration and the shortest night. This is true of the Northern Hemisphere.

In the South everything is the opposite. Interesting natural phenomena are associated with this day. The Polar Circle is followed by a polar day, the sun does not go beyond the horizon at the North Pole for 6 months. In St. Petersburg in June mysterious white nights begin. They last about the middle of June for two to three weeks.

All these 4 astrological dates can change for 1-2 days, since the solar year does not always coincide with the calendar year. Also, biases occur in leap years.

The height of the sun above the horizon and climatic conditions

The sun is one of the most important climate-forming factors. Depending on how the height of the sun over the horizon over a particular area of the earth's surface changes, climatic conditions and seasons change.

For example, in the Far North, the sun's rays fall at a very small angle and only glide along the surface of the earth, without heating it at all. Under the condition of this factor, the climate here is extremely severe, there is permafrost, cold winters with chilling winds and snows.

The higher the height of the sun above the horizon, the warmer the climate. For example, at the equator, it is unusually hot, tropical. Seasonal fluctuations also around the equator are almost not felt, in these areas, eternal summer.

Measuring the height of the sun above the horizon

As they say, all ingenious is simple. So it is here. The instrument for measuring the height of the sun above the horizon is elementary. It is a horizontal surface with a pole in the middle of a length of 1 meter. On a sunny day at noon, the pole casts the shortest shadow. With the help of this shortest shadow, calculations and measurements are carried out. It is necessary to measure the angle between the end of the shadow and the segment connecting the end of the pole with the end of the shadow. This value of the angle and will be the angle of the sun over the horizon. This device is called a gnomon.

Gnomon is an ancient astrological instrument. There are other instruments for measuring the height of the sun above the horizon, such as sextant, quadrant, astrolabe.