Why does the sun illuminate the earth differently throughout the year? Why does the sun illuminate the earth differently The sun illuminates the earth

With the help of this video tutorial, you can independently study the topic "Distribution of sunlight and heat." First, discuss what determines the change of seasons, study the scheme of the annual rotation of the Earth around the Sun, paying special attention to the most remarkable four dates in terms of illumination by the Sun. Then you will find out what determines the distribution of sunlight and heat on the planet and why this happens unevenly.

Rice. 2. Illumination of the Earth by the Sun ()

In winter, the southern hemisphere of the Earth is better illuminated, in summer - the northern one.

Rice. 3. Scheme of the annual rotation of the Earth around the Sun

Solstice (summer solstice and winter solstice) - the times when the height of the Sun above the horizon at noon is greatest (summer solstice, June 22) or least (winter solstice, December 22). In the southern hemisphere, the opposite is true. On June 22, in the northern hemisphere, the greatest illumination by the Sun is observed, the day is longer than the night, and the polar day is observed beyond the polar circles. In the southern hemisphere, again, the opposite is true (i.e., all this is typical for December 22).

Arctic Circles (Arctic Circle and Antarctic Circle) - the parallels respectively with north and south latitude are about 66.5 degrees. North of the Arctic Circle and south of the Antarctic Circle, polar day (summer) and polar night (winter) are observed. The area from the Arctic Circle to the Pole in both hemispheres is called the Arctic. polar day - the period when the sun at high latitudes around the clock does not fall below the horizon.

polar night - the period when the Sun does not rise above the horizon at high latitudes around the clock - a phenomenon opposite to the polar day, is observed simultaneously with it at the corresponding latitudes of the other hemisphere.

Rice. 4. Scheme of the illumination of the Earth by the Sun by zones ()

Equinox (spring equinox and autumn equinox) - moments when the sun's rays touch both poles, and fall vertically on the equator. The spring equinox occurs on March 21st and the autumnal equinox occurs on September 23rd. These days, both hemispheres are equally lit, the day is equal to the night,

The main reason for the change in air temperature is the change in the angle of incidence of the sun's rays: the more sheer they fall on the earth's surface, the better they warm it.

Rice. 5. The angles of incidence of the sun's rays (at the position of the Sun 2, the rays warm the earth's surface better than at position 1) ()

On June 22, the sun's rays most sheer fall on the northern hemisphere of the Earth, thereby warming it to the greatest extent.

Tropics - The Northern Tropic and the Southern Tropic are parallels, respectively, with northern and southern latitudes of about 23.5 degrees. On one of the days of the solstice, the Sun at noon is above them at its zenith.

The tropics and polar circles divide the Earth into zones of illumination. Belts of illumination - parts of the Earth's surface bounded by the tropics and the polar circles and differing in lighting conditions. The warmest illumination zone is tropical, the coldest is polar.

Rice. 6. Belts of illumination of the Earth ()

The sun is the main luminary, the position of which determines the weather on our planet. The moon and other cosmic bodies have an indirect influence.

Salekhard is located on the line of the Arctic Circle. In this city, an obelisk to the Arctic Circle is installed.

Rice. 7. Obelisk to the Arctic Circle ()

Cities where you can watch the polar night: Murmansk, Norilsk, Monchegorsk, Vorkuta, Severomorsk, etc.

Homework

Section 44.

1. Name the days of the solstice and the days of the equinox.

Bibliography

Main

1. Initial course of geography: textbook. for 6 cells. general education institutions / T.P. Gerasimova, N.P. Neklyukov. - 10th ed., stereotype. - M.: Bustard, 2010. - 176 p.

2. Geography. Grade 6: atlas. - 3rd ed., stereotype. - M.: Bustard; DIK, 2011. - 32 p.

3. Geography. Grade 6: atlas. - 4th ed., stereotype. - M.: Bustard, DIK, 2013. - 32 p.

4. Geography. 6 cells: cont. maps: M.: DIK, Drofa, 2012. - 16 p.

Encyclopedias, dictionaries, reference books and statistical collections

1. Geography. Modern illustrated encyclopedia / A.P. Gorkin. - M.: Rosmen-Press, 2006. - 624 p.

Literature for preparing for the GIA and the Unified State Examination

1. Geography: Initial course: Tests. Proc. allowance for students 6 cells. - M.: Humanit. ed. center VLADOS, 2011. - 144 p.

2. Tests. Geography. Grades 6-10: Teaching aid / A.A. Letyagin. - M .: LLC "Agency" KRPA "Olimp": "Astrel", "AST", 2001. - 284 p.

1. Federal Institute of Pedagogical Measurements ().

2. Russian Geographical Society ().

3. Geografia.ru ().

The sun is the main source of heat and the only star in our solar system, which, like a magnet, attracts all the planets, satellites, asteroids, comets and other "inhabitants" of space.

The distance from the Sun to the Earth is over 149 million kilometers. It is this distance of our planet from the Sun that is commonly called an astronomical unit.

Despite its significant distance, this star has a huge impact on our planet. Depending on the position of the Sun on Earth, day follows night, summer replaces winter, magnetic storms arise and amazing auroras form. And most importantly, without the participation of the Sun on Earth, the process of photosynthesis, the main source of oxygen, would be impossible.

The position of the sun at different times of the year

Our planet moves around the celestial source of light and heat in a closed orbit. This path can be schematically represented as an elongated ellipse. The Sun itself is not located in the center of the ellipse, but somewhat to the side.

The Earth moves in and out of the Sun, completing a full orbit in 365 days. Our planet is closest to the sun in January. At this time, the distance is reduced to 147 million km. The point in the earth's orbit closest to the sun is called perihelion.

The closer the Earth is to the Sun, the more the South Pole is illuminated, and summer begins in the countries of the southern hemisphere.

Closer to July, our planet moves as far as possible from the main star of the solar system. During this period, the distance is more than 152 million km. The farthest point in the Earth's orbit from the Sun is called aphelion. The farther the globe is from the Sun, the more light and heat the countries of the northern hemisphere receive. Then summer comes here, and, for example, in Australia and South America, winter dominates.

How the Sun illuminates the Earth at different times of the year

The illumination of the Earth by the Sun at different times of the year directly depends on the remoteness of our planet in a given period of time and on which "side" the Earth is turned at that moment to the Sun.

The most important factor influencing the change of seasons is the earth's axis. Our planet, revolving around the Sun, has time to turn around its own imaginary axis at the same time. This axis is located at an angle of 23.5 degrees to the heavenly body and always turns out to be directed to the North Star. A full rotation around the earth's axis takes 24 hours. Axial rotation also provides a change of day and night.

By the way, if this deviation did not exist, then the seasons would not replace each other, but would remain constant. That is, somewhere a constant summer would reign, in other areas there would be a constant spring, a third of the earth would forever be watered with autumn rains.

Under the direct rays of the Sun on the days of the equinox is the earth's equator, while on the days of the solstice the sun at the zenith will be at latitudes of 23.5 degrees, gradually approaching zero latitude in the rest of the year, i.e. to the equator. The sun's rays falling vertically bring more light and heat, they do not dissipate in the atmosphere. Therefore, the inhabitants of countries located on the equator never know the cold.

The poles of the globe are alternately in the rays of the sun. Therefore, at the poles, day lasts half a year, and night lasts half a year. When the North Pole is illuminated, then spring comes in the northern hemisphere, replacing summer.

In the next six months, the picture changes. The South Pole is facing the Sun. Now summer is beginning in the southern hemisphere, and winter is setting in in the countries of the northern hemisphere.

Twice a year, our planet is in a position where the sun's rays equally illuminate its surface from the Far North to the South Pole. These days are called the equinoxes. Spring is celebrated on March 21, autumn - September 23.

Two more days of the year are called solstices. At this time, the Sun is either as high as possible above the horizon, or as low as possible.

In the northern hemisphere, December 21 or 22 is the longest night of the year, the winter solstice. And on June 20 or 21, on the contrary, the day is the longest, and the night is the shortest - this is the day of the summer solstice. In the southern hemisphere, the opposite is true. There are long days in December and long nights in June.

On a hot summer day, when the weather is clear and we are exhausted from the high temperature, we often hear the phrase "the sun is at its zenith." In our understanding, we are talking about the fact that the celestial body is located at the highest point and warms as much as possible, one might even say, scorches the earth. Let's try to plunge a little into astronomy and understand in more detail this expression and how true our understanding of this statement is.

Earth parallels

Since the school curriculum, we know that on our planet there are so-called parallels, which are invisible (imaginary) lines. Their existence is due to the elementary laws of geometry and physics, and knowledge of where these parallels come from is necessary in order to understand the entire course of geography. It is customary to single out the three most important lines - the equator, the Arctic Circle and the tropics.

Equator

It is customary to call the equator an invisible (conditional) line dividing our Earth into two identical hemispheres - the Southern and the Northern. It has long been known that the Earth does not stand on three whales, as was believed in ancient times, but has a spherical shape and, in addition to moving around the Sun, rotates around its axis. So it turns out that on Earth, which has a length of about 40 thousand km, this is the equator. In principle, from a mathematical point of view, everything is clear here, but does this matter for geography? And here, upon closer examination, it turns out that the part of the planet that is located between the tropics receives the most solar heat and light. This is due to the fact that this region of the Earth is always turned towards the Sun, so the rays here fall almost vertically. It follows from this that the highest air temperature is observed in the equatorial regions of the planet, and air masses saturated with moisture create strong evaporation. The sun at its zenith at the equator happens twice a year, that is, it shines absolutely vertically down. For example, in Russia such a phenomenon never occurs.

Tropics

On the globe there are Southern and Northern tropics. It is noteworthy that the sun at its zenith is here only once a year - on the day of the solstice. When the so-called winter solstice occurs - on December 22, the Southern Hemisphere turns out to be maximally turned to the Sun, and on June 22 - vice versa.

Sometimes the South is called in honor of the zodiac constellation that is in the path of the Sun these days. So, for example, the South is conditionally called the Tropic of Capricorn, and the North - Cancer (December and June, respectively).

arctic circles

The polar circle is considered to be a parallel, above which such a phenomenon as polar night or day is observed. The location of the latitude at which the polar circles are located also has a completely mathematical explanation, this is 90 ° minus the tilt of the planet's axis. For the Earth, this value of the polar circles is 66.5 °. Unfortunately, inhabitants of temperate latitudes cannot observe these phenomena. But the sun at its zenith on the parallel corresponding to the polar circle, the event is absolutely natural.

Common Facts

The Earth does not stand still and, in addition to moving around the Sun, rotates around its axis every day. Throughout the year, we observe how the length of the day changes, the air temperature outside the window, and the most attentive can note the change in the position of the stars in the sky. For 364 passes a complete path around the Sun.

Day and night

When it is dark in our country, that is, it means that the Sun illuminates the other hemisphere in a given period of time. A logical question arises why the day is not equal to the length of the night. The fact is that the plane of the trajectory is not at right angles to the earth's axis. Indeed, in this case we would not have seasons in which the ratio of the longitude of day and night changes.

On the 20th of March, it tilts towards the Sun. Then at about noon on the equator line, you can absolutely say for sure that the sun is at its zenith. This is followed by days when a similar phenomenon is observed at more northern points. Already on June 22, the sun at its zenith is located on the Tropic of Cancer, this day is considered the middle of summer and has a maximum longitude. For us, the most familiar definition is the phenomenon of the solstice.

It is interesting that after this day everything happens anew, only in the reverse order, and continues until the moment when the sun is at its zenith again on the equator line at noon - this happens on September 23rd. At this time, the middle of summer comes in the southern hemisphere.

From all this it follows that when the sun is at its zenith at the equator, throughout the globe the length of the night is 12 hours, the same length of time is equal to the day. We used to call this phenomenon the day of the autumn or spring equinox.

Despite the fact that we have dismantled the correct explanation of the concept of “the sun at its zenith”, all the same, for us the wording will be more familiar, which simply means that the sun is as high as possible on this particular day.

Question: Help please! 1. Formulate the geographical consequences of the Earth's rotation: ??) around its axis; b) around the sun. 2. Why does the Sun illuminate the Earth differently during the year? 3. Do you think day is always equal to night at the equator? Does this happen at the poles? 4. Where on Earth is day always equal to night, and is the Sun at its zenith twice a year? 5. The highest position of the Sun on the horizon is called: a) zenith; b) the equator; c) tropical. 6. Complete the sentence:<<Угол падения солнечных лучей и высота Солнца на горизонтом уменьшаются,если...>>

Help me please! 1. Formulate the geographical consequences of the Earth's rotation: ??) around its axis; b) around the sun. 2. Why does the Sun illuminate the Earth differently during the year? 3. Do you think day is always equal to night at the equator? Does this happen at the poles? 4. Where on Earth is day always equal to night, and is the Sun at its zenith twice a year? 5. The highest position of the Sun on the horizon is called: a) zenith; b) the equator; c) tropical. 6. Complete the sentence:<<Угол падения солнечных лучей и высота Солнца на горизонтом уменьшаются,если...>> 7. Which statement is true? 1) The change of day and night is a consequence of the inclination of the earth's axis to the plane of the orbit. 2) In the polar circles, the Sun is below the horizon for half a year. 3) At the time of the summer solstice, the rays of the Sun at noon fall vertically on the Tropic of the North. 4) Only twice a year the North and South Poles of the Earth are illuminated by the Sun in the same way.

Answers:

1. A. 2. Because the Earth rotates around its axis and the rays of the sun do not fall evenly. 3. Yes, always. Yes, sometimes. 4. I don't know. 5. A. 6. I don't know. 7.4.

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