The movement of the sun at different latitudes.

Memo for solving problems on the topic "Earth as a planet solar system»

To perform tasks to determine the height of the Sun above the horizon at various points located on the same parallel, it is necessary to determine the noon meridian using the data on the time of the Greenwich meridian. The midday meridian is determined by the formula:

(12 hours - Greenwich meridian time) * 15º - if the meridian is in the Eastern Hemisphere;

(Greenwich meridian time - 12 noon) * 15º - if the meridian is in the Western Hemisphere.

The closer the meridians proposed in the task are to the noon meridian, the higher the Sun will be in them, the farther - the lower.

Example1. .

Determine in which of the points indicated by letters on the map of Australia, on March 21, the sun will beuppermost above the horizon at 5 am GMT solar time. Write down the rationale for your answer.

Answer. At point A

Point A is closer than other points to the midday meridian (12 - 5) * 15º \u003d 120º East.

Example2. Determine which of the marked letters on the map North America points the sun will be below everything above the horizon at 18:00 GMT. Write down your reasoning.

Answer. At point A (18-12)*15º =90 º

2. To perform tasks to determine the height of the Sun above the horizon at various points that are not on the same parallel, and when there is an indication of the day of the winter (December 22) or summer (June 22) solstice, you need

remember that the Earth moves counterclockwise and the more east the point is, the earlier the Sun will rise above the horizon .;

to analyze the position of the points indicated in the assignment relative to the polar circles and tropics. For example, if the question has an indication of the day - December 20, this means a day close to the day winter solstice, when the polar night is observed in the territory north of the Arctic Circle. This means that the further north the point is located, the later the Sun will rise above the horizon, the further south, the earlier.

Determine in which of the points indicated by letters on the map of North America, on December 20, the Sun first of all on the Greenwich meridian time will rise above the horizon. Write down your reasoning.

Answer. At point C.

Point A is located to the east of point C, and point C is to the north (December 20, the shorter the day, the closer to the north pole).

1. To complete tasks for determining the length of the day (night) in connection with a change in the angle of inclination of the earth's axis to the plane of the orbit, you need to remember that the degree measure of the angle of inclination of the earth's axis to the plane of the Earth's orbit determines the parallel on which the Arctic Circle will be located. Then the analysis of the situation proposed in the task is carried out. For example, if the territory is in the conditions long duration day (in June in the northern hemisphere), then the closer the territory is to the Arctic Circle, the longer the day, the further - the shorter.

Determine which of the parallels: 20° N, 10° N, at the equator, 10° S, or 20° S. - will there be a maximum length of day on the day when the Earth is in orbit in the position shown in the figure by number 3? Justify your answer.

Answer.The maximum duration will be at latitude 20 S.

At point 3, the Earth is on the day of the winter solstice - December 22, in conditions of longer daylight - the Southern Hemisphere. Point A occupies the most southern position.

On which of the parallels indicated in the figure by letters, on December 22, the duration daylight hours least?

4. To determine the geographical latitude of the area, the dependence of the angle of incidence is taken into account sun rays from the latitude of the area. On the days of the equinox(March 21 and September 23), when the rays of the Sun fall vertically on the equator, the formula is used to determine the geographical latitude:

90 º - angle of incidence of the sun's rays = latitude of the area (north or south is determined by the shadows cast by objects).

On the days of the solstices (June 22 and December 22), it must be taken into account that the rays of the Sun fall vertically (at an angle of 90º) on the tropic (23.5 º N and 23.5º S). Therefore, to determine the latitude of the area in the illuminated hemisphere (for example, June 22 in the Northern Hemisphere), the formula is used:

90º- (angle of incidence of the sun's rays - 23.5º) = latitude of the area

To determine the latitude of the area in the unlit hemisphere (for example, December 22 in the Northern Hemisphere), the formula is used:

90º - (angle of incidence of the sun's rays + 23.5º) = latitude of the area

Example1.

Determine geographical coordinates point, if it is known that on the days of the equinox the noonday Sun stands there above the horizon at an altitude of 40º (the shadow of the object falls to the north), and local time is ahead of the Greenwich meridian time by 3 hours. Write down your calculations and reasoning

Answer. 50 º N, 60 º E

90 º - 40 º = 50 º ( NL , because the shadow of objects falls to the north in the northern hemisphere)

(12-9)x15 =60º ( o.d. , because local time is ahead of Greenwich Mean Time, so the point is located to the east)

Example2.

Determine the geographical coordinates of a point located in the United States, if it is known that on March 21 at 17 o'clock in the solar time of the Greenwich meridian at this point it is noon and the Sun is at an altitude of 50 ° above the horizon. Write down your reasoning.

Answer. 40ºN, 75ºW

90 º -50 º =40 º ( NL -because USA is in the northern hemisphere

(17h -12h)*15 = 75º (h.d., because it is located from the Greenwich meridian to the west for 3 time zones)

Example3.

Determine the geographical latitude of the place if it is known that on June 22 the noon Sun is above the horizon at an altitude of 35º NL Record your calculations.

Answer.78,5 º NL

90 º -(35 º -23.5 º ) = 78.5 s.l.

5. To determine the meridian (geographical longitude of the area), on which the point is located, according to the time of the Greenwich meridian and local solar time, it is necessary to determine the time difference between them. For example, if it is noon (12 o'clock) on the Greenwich meridian, and the local solar time at the specified point is 8 o'clock, the difference (12-8) is 4 hours. The length of one time zone is 15º. To determine the desired meridian, the calculation is 4 x 15º = 60º. To determine the hemisphere in which a given meridian is located, you need to remember that the Earth rotates from west to east (counterclockwise). So, if the time of the Greenwich meridian is greater than at a given point, the point is in the Western Hemisphere (as in the proposed example). If the time of the Greenwich meridian is less than the given point, the point is in the Eastern Hemisphere.

Example.

On what meridian is the point located, if it is known that at noon according to the Greenwich meridian time, the local solar time is 16 hours in it? Write down your reasoning.

Answer. The point is on meridian 60º o.d.

16h. -12h. = 4 hours (time difference)

4x15 º = 60 º

Eastern longitude, because at the point 16.00, when it is still 12.00 at Greenwich (i.e. the point is located to the east)

φ = 90° - North Pole
Only at the Pole day and night last for six months. On the day of the vernal equinox, the Sun makes a full circle along the horizon, then every day it spirals higher, but not higher than 23 ° 27 (on the day of the summer solstice). After that, revolution after revolution, the Sun again descends to the horizon. Its light is repeatedly reflected from ice and hummocks. On the day of the autumnal equinox, the Sun once again bypasses the entire horizon, and its next turns very gradually go deeper and deeper below the horizon. Dawn lasts for weeks, even months, moving through all 360 °. The white night gradually darkens, and only near the day of the winter solstice does it become dark. This is the middle of the polar night. But the Sun does not fall under the horizon below 23°27. The polar night gradually brightens and the morning dawn lights up.

φ \u003d 80 ° - one of the latitudes of the Arctic
The motion of the Sun at latitude φ = 80° is typical for regions north of the Arctic Circle, but south of the pole. After the day of the spring equinox, the days grow very quickly, and the nights shorten, the first period of white nights begins - from March 15 to April 15 (1 month). Then the Sun, instead of setting below the horizon, touches it at the north point and rises again, goes around the sky, moving all 360 °. The daily parallel is located at a slight angle to the horizon, the Sun culminates over the south point and descends to the north, but does not go beyond the horizon and does not even touch it, but passes above the north point and again makes another daily revolution in the sky. So the Sun rises in a spiral higher and higher until the day of the summer solstice, which marks the middle of the polar day. Then the turns of the daily motion of the Sun descend lower and lower. When the Sun touches the horizon at the north point, the polar day will end, which lasted 4.5 months (from April 16 to August 27), the second period of white nights will begin from August 27 to September 28. Then the duration of the nights increases rapidly, the days become shorter and shorter, because. the points of sunrise and sunset are rapidly shifting to the south, and the arc of the daily parallel over the horizon is shortening. On one of the days before the winter solstice, the Sun does not rise above the horizon at noon, the polar night begins. The sun, moving in a spiral, goes deeper and deeper below the horizon. The middle of the polar night is the day of the winter solstice. After it, the Sun again spirals towards the equator. In relation to the horizon, the turns of the spiral are inclined, therefore, when the Sun rises to the southern part of the horizon, it gets light, then it gets dark again, there is a struggle between light and darkness. With each turn, the daytime twilight becomes lighter and, finally, the Sun appears for a moment above the southern (!) horizon. This long-awaited beam marks the end of the polar night, which lasted 4.2 months from October 10 to February 23. Every day the Sun lingers longer and longer above the horizon, describing an ever larger arc. The greater the latitude, the longer the polar days and polar nights, and the shorter the period of daily change of days and nights between them. In these latitudes, long twilight, because The sun goes under the horizon at a slight angle. In the Arctic, the Sun can rise at any point on the eastern horizon from north to south, and set also at any point on the western horizon. Therefore, the navigator, who believes that the Sun always rises at the point of the east and sets at the point, runs the risk of making a heading error of 90 °.

φ = 66°33" - Arctic Circle
Latitude φ \u003d 66 ° 33 "- the maximum latitude that separates the regions in which the Sun rises and sets every day from the regions in which merged polar days and merged polar nights are observed. At this latitude in summer, the points of sunrise and sunset shift with "wide steps" from the points east and west 90 ° north, so that on the day of the summer solstice they meet at the point north. Therefore, the Sun, having descended to the northern horizon, immediately rises again, so that two days merge into a continuous polar day (June 21 and 22 Before the polar day and after it, periods of white nights set in. The first - from April 20 to June 20 (67 white nights), the second - from June 23 to August 23 (62 white nights). On the day of the winter solstice, the points of sunrise and sunset meet at the south point.There is no day between two nights.The polar night lasts two days (December 22, 23) Between the polar day and the polar night, the Sun rises and sets every day, but the length of days and nights changes rapidly.

φ = 60° - latitude of St. Petersburg
The famous white nights are observed before and after the summer solstice, when "one dawn hurries to replace another", i.e. The sun descends shallowly below the horizon at night, so that its rays illuminate the atmosphere. But the inhabitants of St. Petersburg are silent about their "black days", when the Sun on the day of the winter solstice rises at noon only 6 ° 33" above the horizon. The white nights (navigational twilight) of St. Petersburg are especially good in combination with its architecture and the Neva. They begin around May 11 and last 83 days until August 1. The brightest time - the middle of the interval - is around June 21. During the year, the points of sunrise and sunset shift along the horizon by 106 ° But white nights are observed not only in St. Petersburg, and all along the parallel φ = 60° and north up to φ = 90°, southward φ = 60° the white nights become shorter and darker.

φ = 54°19" - latitude of Ulyanovsk

This is the latitude of Ulyanovsk. The movement of the Sun in Ulyanovsk is typical for all middle latitudes. The radius of the sphere depicted in the figure is so large that, in comparison with it, the Earth looks like a point (it is symbolized by the observer). Geographic latitude φ is given by the height of the pole above the horizon, i.e. angle Pole (P) - Observer - North Point (C) in the horizon. On the day of the vernal equinox (21.03), the Sun rises exactly in the east, rises across the sky, shifting to the south. Above the south point - the highest position of the Sun on a given day - the upper culmination, i.e. noon, then it "downhill" descends and sets exactly in the west. The further movement of the Sun continues below the horizon, but the observer does not see this. At midnight, the Sun reaches a lower climax below the north point, then rises again to the eastern horizon. On the day of the equinox, half of the daily parallel of the Sun is above the horizon (day), half is below the horizon (night). On the next day, the Sun does not rise exactly at the point of the east, but at a point slightly shifted to the north, the daily parallel passes over the previous one, the height of the Sun at noon is greater than on the previous day, the setting point is also shifted to the north. Thus, the daily parallel of the Sun is no longer divided by the horizon in half: most of it is above the horizon, the smaller one is below the horizon. The summer half of the year is coming. The points of sunrise and sunset are increasingly shifting to the north, more and more of the parallel is above the horizon, the midday height of the Sun increases and on the day of the summer solstice (21.07 -22.07) in Ulyanovsk reaches 59 ° 08 ". At the same time, the points of sunrise and sunset are shifted relative to the points of the east and west to the north by 43.5 °.After the day of the summer solstice, the daily parallels of the Sun descend to the equator.On the day of the autumnal equinox (23.09), the Sun again rises and sets at the points of east and west, passes along the equator.In the future, the Sun gradually day after day descends under the equator, with the points of sunrise and sunset shifting to the south until the day of the winter solstice (23.12) also by 43.5 °. winter time is below the horizon. The midday height of the Sun decreases to 12 ° 14 ". The further movement of the Sun along the ecliptic occurs along parallels, again approaching the equator, the points of sunrise and sunset return to the points of east and west, the days increase, spring comes again! It is interesting that in Ulyanovsk the points of sunrise are shifting along the eastern horizon by 87 °. The points of sunset respectively "walk" along the western horizon. The sun rises exactly in the east and sets exactly in the west only twice a year - on the days of the equinoxes. The latter is true on the entire surface of the Earth, except for the poles.

φ = 0° - Earth's equator
The movement of the sun over the horizon different times year for an observer located at mid-latitudes (left) and at the Earth's equator (right).

At the equator, the Sun passes through the zenith twice a year, on the days of spring and autumnal equinoxes, i.e. There are two "summers" at the equator, when we have spring and autumn. Day at the equator is always equals night(for 12 hours). The points of sunrise and sunset shift slightly from the points of east and west, no more than 23 ° 27 "towards the south and by the same amount towards the north. There is practically no twilight, a hot bright day is abruptly replaced by a black night.

φ \u003d 23 ° 27 "- Northern Tropic
The sun rises steeply above the horizon, during the day it is very hot, then it drops steeply below the horizon. Twilight is short, nights are very dark. The most salient feature is that the Sun once a year, on the day of the summer solstice, reaches its zenith at noon.

φ = -54°19" - latitude corresponding to Ulyanovsk in the Southern Hemisphere
As in the entire southern hemisphere, the Sun rises on the eastern horizon and sets on the western. After sunrise, the sun rises northern part horizon at noon, at midnight goes under the southern horizon. Otherwise, the movement of the Sun is similar to its movement at the latitude of Ulyanovsk. The movement of the Sun in the southern hemisphere is similar to the movement of the Sun at the corresponding latitudes northern hemisphere. The only difference is that from the east, the Sun moves towards the northern horizon, and not the southern one, culminates over the north point at noon, and then also sets on the western horizon. The seasons in the northern and southern hemispheres are opposite.

φ \u003d 10 ° - one of the latitudes of the hot zone
The movement of the Sun at a given latitude is characteristic of all places located between the northern and southern tropics of the Earth. Here the Sun passes through the zenith twice a year: on April 16 and August 27, with an interval of 4.5 months. The days are very hot, the nights are dark, starry. Days and nights differ little in duration, there is practically no twilight, the Sun sets below the horizon, and it immediately becomes dark.

such a picture as in the photograph (Fig. 1). Why do we see divergent rather than parallel rays?

Question 3. The newly appointed director of the cinema decided to introduce new technologies and instead of a white cloth screen, hang a flat mirror. What does this mean for viewers?

Task 4. Why at night in the light of car headlights does a puddle on the road seem to the driver as a dark spot on a light background?

Question 5. The arrow AB and the axis of symmetry OO 1 of a round flat mirror (Fig. 2) belong to the same plane π. Build its image.

RICE . 3

Question 6. Mark with shading in fig. 2 area from which the entire arrow can be seen in the mirror. How many times do you need to increase the diameter of the mirror so that an observer located at point C can see the entire reflection of the entire arrow. The position of the axis OO 1 of the mirror is unchanged.

Question 7. Two parallel beams 1 and 2 propagate in water (Fig. 3). Beam 1 goes directly into the air, and beam 2 goes through a transparent plane-parallel plate lying on the surface of the water. Will the beams remain parallel as they exit into the air?

Question 8. A dolphin is watching from under the water for a trainer standing on the edge of the pool. The trainer has a fish in his hand. Which of the distances from the dolphin to the fish is greater: apparent to the dolphin or actual?

Question 9. The diamond was lowered into the water. Did its limiting angle of total reflection increase or decrease after that? Pre-

breaking diamond n A 2.42, water n B 1.33.

2012-2013 academic year year, No. 4, 8 cells. Physics. Laws of reflection and refraction of light

Question 10*. Physicists have learned to create substances (metamaterials) with a negative refractive index. Suppose you have such a transparent plate at your disposal, with a refractive index of n = -1. How can you use a laser pointer to make sure that this is really a metamaterial?

Task 1 . The sun rose above the horizon at an angle of 56º. What angle with the horizon must a plane mirror make in order to be able to

Task 3 . In the center of the wall of a square room, the height of which is H = 3 m, and the length L = 4 m, hangs a mirror with a height h = 0.6 m. From what maximum distance l, a person standing in front of the mirror can see the opposite wall of the room in full height?

Task 4 . The planes of two mirrors form an angle α (Fig. 5). A beam lying in the plane of the figure falls on the mirror M 1 at an angle φ1. Then this beam is reflected from the mirror M 2 and leaves the system of mirrors. Find the deflection angle δ of the beam passing through the system.

2013, ZFTSH MIPT, Slobodyanin Valery Pavlovich

2012-2013 academic year year, No. 4, 8 cells. Physics. Laws of reflection and refraction of light

Task 5 . Two flat mirrors form an angle of 100° (Fig. 6). On the bisector of this angle is a point source of light S 0 . How many images of the source S 0 will such an optical system give? Make the necessary builds.

Task 6 . A beam of light falls at an angle φ0 = 45° onto a stack of glass plane-parallel plates whose refractive index increases from 1.40 to 1.80 with a step n = 0.05 (Fig. 7). How many records are in the stack? At what angle φN+1 will this ray come out of the stack?

Task 7 . At the bottom of the lake with a depth of H = 8 m, the fishermen installed a lantern. Calculate the diameter of the area of ​​the water surface from which the light of this lantern can be seen by fishermen at night.

2013, ZFTSH MIPT, Slobodyanin Valery Pavlovich

φ = 90° - North Pole

Only at the Pole day and night last for six months. On the day of the vernal equinox, the Sun makes a full circle along the horizon, then every day it spirals higher, but not higher than 23 ° 27 (on the day of the summer solstice). After that, revolution after revolution, the Sun again descends to the horizon. Its light is repeatedly reflected from ice and hummocks. On the day of the autumnal equinox, the Sun once again bypasses the entire horizon, and its next turns very gradually go deeper and deeper below the horizon. Dawn lasts for weeks, even months, moving through all 360 °. The white night gradually darkens, and only near the day of the winter solstice does it become dark. This is the middle of the polar night. But the Sun does not fall under the horizon below 23°27. The polar night gradually brightens and the morning dawn lights up.

φ \u003d 80 ° - one of the latitudes of the Arctic

The motion of the Sun at latitude φ = 80° is typical for regions located north of the Arctic Circle, but south of the pole. After the day of the spring equinox, the days grow very quickly, and the nights shorten, the first period of white nights begins - from March 15 to April 15 (1 month). Then the Sun, instead of setting below the horizon, touches it at the north point and rises again, goes around the sky, moving all 360 °. The daily parallel is located at a slight angle to the horizon, the Sun culminates over the south point and descends to the north, but does not go beyond the horizon and does not even touch it, but passes above the north point and again makes another daily revolution in the sky. So the Sun rises in a spiral higher and higher until the day of the summer solstice, which marks the middle of the polar day. Then the turns of the daily motion of the Sun descend lower and lower. When the Sun touches the horizon at the north point, the polar day will end, which lasted 4.5 months (from April 16 to August 27), the second period of white nights will begin from August 27 to September 28. Then the duration of the nights increases rapidly, the days become shorter and shorter, because. the points of sunrise and sunset are rapidly shifting to the south, and the arc of the daily parallel over the horizon is shortening. On one of the days before the winter solstice, the Sun does not rise above the horizon at noon, the polar night begins. The sun, moving in a spiral, goes deeper and deeper below the horizon. The middle of the polar night is the day of the winter solstice. After it, the Sun again spirals towards the equator. In relation to the horizon, the turns of the spiral are inclined, therefore, when the Sun rises to the southern part of the horizon, it gets light, then it gets dark again, there is a struggle between light and darkness. With each turn, the daytime twilight becomes lighter and, finally, the Sun appears for a moment above the southern (!) horizon. This long-awaited beam marks the end of the polar night, which lasted 4.2 months from October 10 to February 23. Every day the Sun lingers longer and longer above the horizon, describing an ever larger arc. The greater the latitude, the longer the polar days and polar nights, and the shorter the period of daily change of days and nights between them. In these latitudes, long twilight, because The sun goes under the horizon at a slight angle. In the Arctic, the Sun can rise at any point on the eastern horizon from north to south, and set also at any point on the western horizon. Therefore, the navigator, who believes that the Sun always rises at the point of the east and sets at the point, runs the risk of making a heading error of 90 °.

φ = 66°33" - Arctic Circle

Latitude φ \u003d 66 ° 33 "- the maximum latitude that separates the regions in which the Sun rises and sets every day from the regions in which merged polar days and merged polar nights are observed. At this latitude in summer, the points of sunrise and sunset shift with "wide steps" from the points east and west 90 ° north, so that on the day of the summer solstice they meet at the point north. Therefore, the Sun, having descended to the northern horizon, immediately rises again, so that two days merge into a continuous polar day (June 21 and 22 Before the polar day and after it, periods of white nights set in. The first - from April 20 to June 20 (67 white nights), the second - from June 23 to August 23 (62 white nights). On the day of the winter solstice, the points of sunrise and sunset meet at the south point.There is no day between two nights.The polar night lasts two days (December 22, 23) Between the polar day and the polar night, the Sun rises and sets every day, but the length of days and nights changes rapidly.

φ = 60° - latitude of St. Petersburg

The famous white nights are observed before and after the summer solstice, when "one dawn hurries to replace another", i.e. The sun descends shallowly below the horizon at night, so that its rays illuminate the atmosphere. But the inhabitants of St. Petersburg are silent about their "black days", when the Sun on the day of the winter solstice rises at noon only 6 ° 33" above the horizon. The white nights (navigational twilight) of St. Petersburg are especially good in combination with its architecture and the Neva. They begin around May 11 and last 83 days until August 1. The brightest time - the middle of the interval - is around June 21. During the year, the points of sunrise and sunset shift along the horizon by 106 ° But white nights are observed not only in St. Petersburg, and all along the parallel φ = 60° and north up to φ = 90°, southward φ = 60° the white nights become shorter and darker.

φ = 54°19" - latitude of Ulyanovsk

This is the latitude of Ulyanovsk. The movement of the Sun in Ulyanovsk is typical for all middle latitudes. The radius of the sphere depicted in the figure is so large that, in comparison with it, the Earth looks like a point (it is symbolized by the observer). Geographic latitude φ is given by the height of the pole above the horizon, i.e. angle Pole (P) - Observer - North Point (C) in the horizon. On the day of the vernal equinox (21.03), the Sun rises exactly in the east, rises across the sky, shifting to the south. Above the south point - the highest position of the Sun on a given day - the upper culmination, i.e. noon, then it "downhill" descends and sets exactly in the west. The further movement of the Sun continues below the horizon, but the observer does not see this. At midnight, the Sun reaches a lower climax below the north point, then rises again to the eastern horizon. On the day of the equinox, half of the daily parallel of the Sun is above the horizon (day), half is below the horizon (night). On the next day, the Sun does not rise exactly at the point of the east, but at a point slightly shifted to the north, the daily parallel passes over the previous one, the height of the Sun at noon is greater than on the previous day, the setting point is also shifted to the north. Thus, the daily parallel of the Sun is no longer divided by the horizon in half: most of it is above the horizon, the smaller one is below the horizon. The summer half of the year is coming. The points of sunrise and sunset are increasingly shifting to the north, more and more of the parallel is above the horizon, the midday height of the Sun increases and on the day of the summer solstice (21.07 -22.07) in Ulyanovsk reaches 59 ° 08 ". At the same time, the points of sunrise and sunset are shifted relative to the points of the east and west to the north by 43.5 °.After the day of the summer solstice, the daily parallels of the Sun descend to the equator.On the day of the autumn equinox (23.09), the Sun again rises and sets at the points of east and west, passes along the equator.In the future, the Sun gradually day by day descends under the equator. At the same time, the points of sunrise and sunset shift to the south until the day of the winter solstice (23.12) also by 43.5 °. Most of the parallels in winter are under the horizon. The midday height of the Sun decreases to 12 ° 14 ". The further movement of the Sun along the ecliptic occurs along parallels, again approaching the equator, the points of sunrise and sunset return to the points of east and west, the days increase, spring comes again! Interestingly, in Ulyanovsk, the sunrise points are shifted along the eastern horizon by 87°. Points of entry, respectively, "walk" along the western horizon. The sun rises exactly in the east and sets exactly in the west only twice a year - on the equinoxes. The latter is true on the entire surface of the Earth, except for the poles.

φ = 0° - Earth's equator

The movement of the Sun over the horizon at different times of the year for an observer located at mid-latitudes (left) and at the Earth's equator (right).

At the equator, the Sun passes through the zenith twice a year, on the days of the spring and autumn equinoxes, i.e. There are two "summers" at the equator, when we have spring and autumn. Day at the equator is always equal to night (12 hours each). The points of sunrise and sunset shift slightly from the points of east and west, no more than 23 ° 27 "towards the south and by the same amount towards the north. There is practically no twilight, a hot bright day is abruptly replaced by a black night.

φ \u003d 23 ° 27 "- Northern Tropic

The sun rises steeply above the horizon, during the day it is very hot, then it drops steeply below the horizon. Twilight is short, nights are very dark. The most characteristic feature is that the Sun once a year, on the day of the summer solstice, reaches its zenith at noon.

φ = -54°19" - latitude corresponding to Ulyanovsk in the Southern Hemisphere

As in the entire southern hemisphere, the Sun rises on the eastern horizon and sets on the western. After sunrise, the Sun rises above the northern part of the horizon at noon, at midnight it goes under the southern horizon. Otherwise, the movement of the Sun is similar to its movement at the latitude of Ulyanovsk. The movement of the Sun in the southern hemisphere is similar to the movement of the Sun at the corresponding latitudes of the northern hemisphere. The only difference is that from the east, the Sun moves towards the northern horizon, and not the southern one, culminates over the north point at noon, and then also sets on the western horizon. The seasons in the northern and southern hemispheres are opposite.

φ \u003d 10 ° - one of the latitudes of the hot zone

The movement of the Sun at a given latitude is characteristic of all places located between the northern and southern tropics of the Earth. Here the Sun passes through the zenith twice a year: on April 16 and August 27, with an interval of 4.5 months. The days are very hot, the nights are dark, starry. Days and nights differ little in duration, there is practically no twilight, the Sun sets below the horizon, and it immediately becomes dark.