A constellation is understood as an area of the sky within certain established boundaries. The entire sky is divided into 88 constellations, which can be found by their characteristic arrangement of stars.
Some constellation names are associated with Greek mythology, for example Andromeda, Perseus, Pegasus, some with objects that resemble figures formed by bright stars of the constellations: Arrow, Triangle, Libra, etc. There are constellations named after animals, for example Leo, Cancer, Scorpion.
Constellations in the firmament are found by mentally connecting their brightest stars with straight lines into a certain figure. In each constellation, bright stars have long been designated by Greek letters, most often the brightest star of the constellation - by a letter, then by letters, etc. in alphabetical order of decreasing brightness; for example, polar Star there are constellations Ursa Minor.
Stars have different brightness and color: white, yellow, reddish. The redder the star, the colder it is. Our Sun belongs to the yellow stars.
The ancient Arabs gave the bright stars their own names. White stars: Vega in the constellation Lyra, Altair in the constellation Eagle, (visible in summer and autumn), Sirius- the brightest star in the sky (visible in winter); red stars: Betelgeuse in the constellation Orion and Aldebaran in the constellation Taurus (visible in winter), Antares in the constellation Scorpio (visible in summer); yellow Chapel in the constellation Auriga (visible in winter).
Accurate measurements show that stars have both fractional and negative stellar magnitudes, for example: for Aldebaran the stellar magnitude m= 1.06, for Vega m= 0.14, for Sirius m= -1.58, for the Sun m = - 26,80.
The phenomena of the diurnal movement of stars are studied using a mathematical construction - the celestial sphere, that is, an imaginary sphere of arbitrary radius, the center of which is at the point of observation.
The axis of the apparent rotation of the celestial sphere, connecting both poles of the world (P and P ") and passing through the observer, is called axis of the world... The axis of the world for any observer will always be parallel to the axis of rotation of the Earth.
To make a star map depicting constellations on a plane, you need to know the coordinates of the stars. In the equatorial system, one coordinate is the distance of the star from the celestial equator, called declination... It varies within ± 90 ° and is considered positive north of the equator and negative south. Declination is similar to latitude. The second coordinate is analogous to geographic longitude and is called right ascension.
Right ascension of a star is measured by the angle between the planes of the great circles, one passes through the poles of the world and this star, and the other through the poles of the world and the vernal equinox, which lies at the equator. This point was named so because the Sun happens in it (on the celestial sphere) in the spring of March 20-21, when the day is equal to the night.
Determination of geographical latitude
The phenomena of the passage of luminaries through the celestial meridian are called culminations. In the upper culmination, the height of the luminary is maximum, in the lower culmination, it is minimum. The time interval between culminations is half a day.
Geographic latitude can be determined by measuring the height of any star with a known declination at the upper climax. It should be borne in mind that if the luminary at the moment of culmination is located south of the equator, then its declination is negative.
EXAMPLE OF SOLUTION OF THE PROBLEM
Task... Sirius was at the top climax at 10 °. What is the latitude of the observation site?
Ecliptic. Visible movement of the sun and moon
The sun and moon change the altitude at which they climax. From this we can conclude that their position relative to the stars (declination) changes. It is known that the Earth moves around the Sun, and the Moon around the Earth.
Determining the height of the Sun at noon, we noticed that twice a year it happens at the celestial equator, in the so-called equinox points... It happens on days spring and autumn equinox(around March 21 and around September 23). The horizon plane bisects the celestial equator. Therefore, on the days of the equinox, the paths of the Sun above and below the horizon are equal, therefore, the lengths of the day and night are equal. Moving along the ecliptic, the Sun on June 22 moves farthest from the celestial equator towards the north pole of the world (by 23 ° 27 "). At noon for the northern hemisphere of the Earth it is highest above the horizon (this value is higher than the celestial equator). The day is the longest, it's called day summer solstice.
The path of the Sun runs through 12 constellations called zodiacal (from the Greek word zoon - animal), and their combination is called the zodiac belt. It includes the following constellations: Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius... Each zodiac constellation, the Sun, passes for about a month. The vernal equinox (one of the two intersections of the ecliptic with the celestial equator) is located in the constellation Pisces.
EXAMPLE OF SOLUTION OF THE PROBLEM
Task... Determine the midday height of the Sun in Arkhangelsk and Ashgabat on the days of the summer and winter solstices
| Given 1 = 65 ° |
SOLUTION The approximate values of the latitude of Arkhangelsk (1) and Ashgabat (2) are found on a geographic map. The declination of the Sun on the days of the summer and winter solstices is known. we find: |
| 1L -? 2L -? 1s -? 2s -? |
Moon movement. Solar and lunar eclipses
Not being self-luminous, the Moon is visible only in the part where the sun's rays fall, or the rays reflected by the Earth. This explains the phases of the moon. Every month the Moon, moving in its orbit, passes between the Earth and the Sun and faces us with the dark side, at this time a new moon occurs. After 1 - 2 days after that, a narrow bright crescent of the young Moon appears in the western part of the sky. The rest of the lunar disk is at this time poorly illuminated by the Earth, which is turned towards the Moon by its daytime hemisphere. After 7 days, the Moon moves away from the Sun by 90 °, the first quarter begins, when exactly half of the Moon's disk is illuminated and the "terminator", that is, the dividing line of the light and dark sides, becomes straight - the diameter of the lunar disk. In the following days, the "terminator" becomes convex, the view of the moon approaches the bright circle, and in 14-15 days the full moon comes. On the 22nd day, the last quarter is observed. The angular distance of the Moon from the Sun decreases, it again becomes a sickle, and after 29.5 days, a new moon comes again. The interval between two successive new moons is called a synodic month, with an average duration of 29.5 days. The synodic month is longer than the sidereal month. If a new moon occurs near one of the nodes of the lunar orbit, a solar eclipse occurs, and a full moon near the node is accompanied by a lunar eclipse.
Lunar and solar eclipses
Due to a slight change in the distances of the Earth from the Moon and the Sun, the apparent angular diameter of the Moon is sometimes slightly larger, sometimes slightly less than the solar one, sometimes equal to it. In the first case, the total eclipse of the Sun lasts up to 7 minutes. 40 s, in the third - only one instant, and in the second case, the Moon does not completely cover the Sun entirely, there is annular eclipse... Then a shining rim of the solar disk is visible around the dark disk of the moon.
On the basis of exact knowledge of the laws of motion of the Earth and the Moon, the moments of eclipses and where and how they will be visible have been calculated for hundreds of years ahead. Maps have been compiled showing the total eclipse strip, lines (isophases) where the eclipse will be visible in the same phase, and lines, relative to which the moments of the beginning, end and middle of the eclipse can be counted for each locality.
Solar eclipses per year for the Earth can be from two to five, in the latter case, certainly private. On average, in the same place, a total solar eclipse is seen extremely rarely - only once during 200-300 years.
If the Moon is between the Sun and the Earth on a new moon, then solar eclipses occur. In a total eclipse, the Moon completely covers the solar disk. In broad daylight, twilight suddenly falls for several minutes and the faintly luminous corona of the Sun and the brightest stars become visible to the naked eye.
Total solar eclipse
Accurate time and geographic longitude determination
For measuring short periods of time in astronomy, the basic unit is average duration of sunny days, that is, the average time interval between the two upper (or lower) culminations of the center of the Sun. This is due to the fact that the Earth does not revolve around the Sun in a circle, but in an ellipse, and the speed of its movement changes slightly.
The moment of the upper culmination of the center of the Sun is called true noon... But to check the clock, to determine the exact time, there is no need to mark the moment of the culmination of the Sun on it. It is more convenient and more accurate to mark the moments of the climax of the stars, since the difference between the moments of the climax of any star and the Sun is precisely known for any time.
Determining the exact time, storing it, and transmitting it by radio to the entire population is a task precise time service that exists in many countries.
Since ancient times, people have used the duration of either the lunar month or the solar year to count large periods of time, that is, the duration of the Sun's revolution along the ecliptic. The year determines the frequency of seasonal changes. The solar year lasts 365 solar days 5 hours 48 minutes 46 seconds.
When compiling a calendar, it is necessary to take into account that the duration of the calendar year should be as close as possible to the duration of the Sun's revolution along the ecliptic, and that the calendar year should contain an integer number of solar days, since it is inconvenient to start the year at different times of the day.
90 ° - 58 ° 34 "= 31 ° 26"
2. From Moscow (n = 2) the plane took off at 23h45 and arrived in Novosibirsk (n = 5) at 06h 08min. How long was he in flight?
24-00 - 23-45 + 6-08 = 6-23 time spent on the flight, excluding standard time
Time difference between Moscow and Novosibirsk = 3 hours. 6-23 - 3 hours = 3-23
3-23 hours flight time
3. What is the declination of the zenith point? What is the midday height of the Sun in Krasnozersk (φ = 53 ° 58 "N) on March 21?
4. A telegram was sent from Vladivostok (n = 9) at 14h20min to St. Petersburg (n = 2), where it was delivered to the addressee at 11h25min. How long has elapsed from the moment the telegram was sent to its delivery to the addressee?
The time difference between Vladivostok and St. Petersburg = 7 hours. When it is 14-20 in Vladivostok, 7-20 in St. Petersburg. 11-25 - 7-20 = 4-05.
Therefore, delivery took 4 hours 05 minutes.
5. At 1832 hours local time, the navigator of the ship received a Moscow time signal transmitted at 11:00. Determine the longitude of the ship if you know the longitude of Moscow (2h30 m).
2 hours = 30 °; 60 time minutes corresponds to 15 °, therefore 30 time minutes corresponds to 7.5 °. Accordingly, the longitude of Moscow is 37.5 ° E.
The time difference between the ship and Moscow is 7 hours 32 minutes.
60 time minutes corresponds to 15 °; therefore 7 o'clock corresponds to 105 ° longitude; 30 time minutes corresponds to 7.5 °; 4 time minutes corresponds to 1 °; 2 time minutes corresponds to 0.5 °. Thus, 7h 32m corresponds to 113 °.
The ship is located 113 ° east of Moscow.
Consequently, the longitude of the ship is 113 + 37.5 = 150.5 ° E.
6. In what place on Earth is the Sun at its zenith twice a year? Explain the answer.
2 times a year, the Sun is at its zenith over the territory located between the tropics.
06.22 the Sun moves from the northern tropic to the south, 22.12 the Sun moves from the southern tropic.
7. On what day of the year was the observation carried out in Novosibirsk (φ = 55 °), if the midday height of the Sun was 32 ° 15 "?
90 - φ - declination of the Sun = 32 ° 15 "
90 - 55 - declination of the Sun = 32 ° 15 "
90 - 55 - 32 ° 15 "= Sun declination
2 ° 45 "= declination of the sun.
The minimum value of the noon height of the Sun in Novosibirsk is 90 ° - 55 ° - 23.5 ° = 11.5 °
The noon height of the Sun in Novosibirsk on the day of the equinox is 90 ° - 55 ° = 35 °
Therefore, when the Sun's midday altitude is 32 ° 15 ", the declination will be negative. That is, on this day the Sun is located in the southern hemisphere
23.5 ° corresponds to 1410 arc minutes
The sun moves 1410 arc minutes in 93 days
The sun moves 15 arc minutes in 1 day. 2 ° 45 "corresponds to 165". It takes 11 days for the Sun to move 2 ° 45 ". Therefore, the Sun is 11 days away from the autumnal equinox. 23.09 - 11 days = 12.09.
Consequently, the observations in Novosibirsk were carried out on September 12
8. Determine the local time in Novosibirsk (λ = 5h32m), if the clock shows an average Moscow time (n = 2) 18h38min.
Novosibirsk is located east of Moscow.
= 5h32m means that Novosibirsk is at a distance from Greenwich at this time.
60 time minutes corresponds to 15 °; therefore, 5 hours corresponds to 75 ° longitude; 30 time minutes corresponds to 7.5 °; 4 time minutes corresponds to 1 °; 2 time minutes corresponds to 0.5 °. Thus, 5h 32m corresponds to 83 ° longitude.
Consequently, the longitude of Novosibirsk is 83 ° E.
The average Moscow time corresponds to 30 ° East longitude. Moscow belt is the 2nd, the middle meridian is a multiple of 15 °.
Thus, the difference in longitudes between Novosibirsk time and Moscow average is 53 °.
60 time minutes corresponds to 15 °; therefore, 3 o'clock corresponds to 45 ° longitude;
53 ° - 45 ° = 8 °
7.5 ° corresponds to 30 time minutes; 0.5 ° corresponds to 2 time minutes
Thus, 53 ° longitude corresponds to 3h 32m
18h38m + 3h 32m = 22h10m - local time in Novosibirsk.
9. In the fall, the hunter went into the forest in the direction of the North Star. How should he come back, guided by the position of the Sun?
The direction to the North Star is the direction to the north. Autumn astronomically falls on a period close to the day of the autumnal equinox. Therefore, day and night are approximately equal. Therefore, on the way to the forest (and this is morning) the Sun should be on the right in the direction of travel. On the way back, the hunter goes south in the evening, therefore, the Sun is in the west. The sun should be on the right.
10. Where the Sun is higher on the same day: in Novosibirsk (φ = 55 °), or in Moscow (φ = 55 ° 45 "). What is the difference in the heights of the Sun?
On the same day, the Sun has the same declination for points located in the same hemisphere between the corresponding tropic and the pole. Hence, the altitude depends on the latitude of the place. The lower the latitude, the higher, ceteris paribus, the higher the midday height of the Sun. The difference in the heights of the Sun for 2 points when measured on one day differs by the difference in latitude
On the same day, the noon height of the Sun is higher in Novosibirsk
On the same day, the noon height of the Sun is 45 "higher in Novosibirsk than in Moscow.
11. Determine the local time at the point, the geographical longitude of which is 7h46 m, if the clock in Moscow (λ = 2h30 m) shows the time 18h38min.
The point is located east of Moscow.
λ = 2h30m means that Moscow is at a distance from Greenwich at this time.
60 time minutes corresponds to 15 °; therefore, 2 hours corresponds to 30 ° longitude; 30 time minutes corresponds to 7.5
λ = 7h46m means that the point is located from Greenwich at this time
60 time minutes corresponds to 15 °; therefore, 7 o'clock corresponds to 105 ° longitude;
4 time minutes corresponds to 1 °, therefore 44 time minutes corresponds to 11 °.
0.5 ° corresponds to 2 time minutes
longitude of the point 105 ° + 11 ° + 0.5 ° = 116.5 ° E.
Thus, the difference in longitudes between Moscow time and this point is 116.5 ° - 37.5 ° = 79 °
60 time minutes corresponds to 15 °; therefore, 75 ° longitude corresponds to 5 hours;
4 time minutes corresponds to 1 °; therefore, 4 ° corresponds to 16 time minutes.
Consequently, the difference between Moscow and the point is the time difference of 5h16m.
18h38m + 5h 16m = 23h54m - local time at this point.
12. Between what points does the Sun rise and set on the winter solstice?
22.12 The sun rises at point south-w and sets at point south-w
13. In Moscow (λ = 2h30 m, n = 2) the clock shows the time 18h50min. What is the local and standard time at this moment in Omsk (λ = 4h54 m, n = 5)?
The time difference between Moscow and Omsk is 3 hours.
Omsk east of Moscow. Therefore, 18h50min + 3h = 21h50min
Standard time in Omsk 21h50min
60 time minutes corresponds to 15 °; therefore, 2 hours corresponds to 30 ° longitude; 30 time minutes corresponds to 7.5
Thus, 2h 30m corresponds to 37.5 ° E.
60 time minutes corresponds to 15 °; therefore, 4 hours corresponds to 60 ° longitude;
4 time minutes corresponds to 1 °, therefore 52 minutes corresponds to 13 ° longitude
2 time minutes corresponds to 0.5 ° longitude
Thus, 4h54 m corresponds to 73.5 ° E.
The longitude difference between Moscow and Omsk is 73.5 ° E. - 37.5 ° E = 36 ° longitude.
15 ° longitude corresponds to 1 hour; 1 ° longitude corresponds to 4 time minutes.
Thus, 36 ° longitude corresponds to 2 hours 24 minutes.
18h50min + 2h24min = 21h14min
Local time in Omsk 21h14min
14. Between what points does the sun rise and set on the summer solstice?
06.22 The sun rises at point s-w and sets at point s-w
15. What is the longitude of the place of observation, if the observer noticed that the solar eclipse began at 13h52m, and should be at 7h15m GMT?
13h52m - 7h15m = 6h37m - the distance of the observation site from Greenwich.
15 ° longitude corresponds to 1 hour; 6 hours correspond to 90 ° longitude
1 ° longitude corresponds to 4 time minutes; 36 minutes corresponds to 9 ° longitude
60 arc minutes correspond to 4 time minutes
15 arc minutes corresponds to 1 time minute
Consequently, the longitude of the observation site is 99 ° 15 "E.
16. At what latitude does the midday height of the Sun not exceed 23 ° 26 "?
Maximum midday altitude occurs in the northern hemisphere on the summer solstice and in the southern hemisphere on the winter solstice. On this day, the solar declination is + 23 ° 26 ".
h = 90 ° - φ + 23 ° 26 "; therefore at h = 23 ° 26" φ = 90 ° - 23 ° 26 "+ 23 ° 26" = 90 °
The midday height of the Sun does not exceed 23 ° 26 "at the latitude of the North Pole 22.06 and South Pole 22.12.
In a given locality, each star always culminates at the same height above the horizon, because its angular distance from the pole of the world and from the celestial equator remains unchanged. The sun and moon change the altitude at which they culminate. From this we can conclude that their position relative to the stars (declination) changes. We know that the Earth moves around the Sun and the Moon around the Earth. Let us trace how the position of both luminaries in the sky changes as a result.
If we observe the time intervals between the upper culminations of the stars and the Sun by the exact clock, then we can be sure that the intervals between the culminations of the stars on four minutes shorter than the intervals between the climaxes of the Sun. This is explained by the fact that during one revolution around the axis (day) the Earth passes about 1/365 of its path around the Sun. It seems to us that the Sun is shifting against the background of the stars to the east - in the direction opposite to the daily rotation of the sky. This shift is about 1 °. To turn to such an angle, the celestial sphere needs another 4 minutes, by which the culmination of the Sun is "delayed". Thus, as a result of the Earth's orbital motion, the Sun in a year describes a large circle in the sky relative to the stars, called ecliptic(fig. 17).
Since the Moon makes one revolution to align the rotation of the sky in a month and therefore passes not 1 °, but about 13 ° in a day, its culmination is delayed every day not by 4 minutes, but by 50 minutes.
Determining the height of the Sun at noon, we noticed that it happens twice a year at the celestial equator, at the so-called equinox points. It happens on days spring and autumn equinox(around March 21 and around September 23). The horizon plane divides the celestial equator in half (Fig. 18). Therefore, on the days of the equinox, the paths of the Sun above and below the horizon are equal, therefore, equal to the duration of the day and night.
What is the declination of the Sun on the days of the equinoxes?
Moving along the ecliptic, the Sun on June 22 moves farthest from the celestial equator towards the north pole of the world (by 23 ° 27 "). At noon for the northern hemisphere of the Earth it is highest above the horizon (this value is higher than the celestial equator, see Fig. 17 and 18) .The longest day, it is called summer solstice.
The great circle of the ecliptic crosses the great circle of the celestial quator at an angle of 23 ° 27 ". At the same time, the Sun is below the quator in winter solstice, December 22 (see Fig. 17 and 18). Thus, on this day, the height of the Sun in the upper climax decreases by 46 ° 54 "compared to June 22, and the day is the shortest. (From the course of physical geography, you know that differences in the conditions of illumination and heating of the Earth by the Sun determine its climatic zones and the changing seasons.)
The deification of the Sun in ancient times gave rise to myths describing the periodically recurring events of the "birth", "resurrection" of the "sun god" throughout the year: the dying of nature in winter, its rebirth in spring, etc. Christian holidays bear traces of the cult of the Sun.
The path of the Sun runs through 12 constellations called zodiacal(from the Greek word zoon - animal), and their combination is called the zodiac belt. It includes the following constellations: Fishes, Aries,Taurus, Twins, Cancer, a lion, Virgo, scales, Scorpion, Sagittarius, Capricorn,Aquarius... Each zodiac constellation, the Sun, passes for about a month. The vernal equinox (one of the two intersections of the ecliptic with the celestial equator) is located in the constellation Pisces.
It is clear that at midnight the zodiacal constellation opposite to that in which the Sun is located passes the upper culmination. For example, in March, the Sun passes through the constellation Pisces, and at midnight the constellation Virgo culminates.
So, we made sure that the apparent motion of the Moon, which revolves around the Earth, and the Sun, around which the Earth revolves, is detected and described in the same way. And based on these observations alone, it is impossible to decide whether the Sun moves around the Earth or the Earth around it.
The planets move against the background of the starry sky in a more complex way. They move one way or the other, sometimes slowly writing out loops (Fig. 19). This is due to the combination of their true motion with the motion of the Earth. In the starry sky, the planets (translated from the ancient Greek "wandering") do not occupy a constant place, as well as the Moon and the Sun. Therefore, on the map of the starry sky, the position of the Sun, Moon and planets can be indicated only for a certain moment.
An example of solving the problem
Task. Determine the midday height of the Sun in Arkhangelsk and Ashgabat on the days of the summer and winter solstices.
Pay attention to how the difference in the noon heights of the Sun on the days of the solstices (for each city) is related to the difference in its declination on these dates.
Compare the difference in the height of the Sun on the same day in these two cities with the difference in their geographic latitudes. Make a conclusion.
How, knowing the height of the Sun at noon in one of the cities, on the day of the summer solstice, can you calculate its height in another city?
Exercise 4
1. At what latitude does the Sun climax at its zenith on the summer solstice?
2. On what days of the year does the Sun reach its zenith for an observer at the Earth's equator?
3. Determine the geographical latitude of the point at which on the day of the winter solstice the climax of the Sun occurs in the point of the south.
Assignment 3
1. Find the 12 zodiac constellations on the star map. Using a moving map of the starry sky, determine which of them will be visible above the horizon on the evening of observation.
2. According to the "School Astronomical Calendar" find the coordinates of the planets at this time and determine on the map in which constellation they are located. Find them in the sky in the evening.
Life on our planet depends on the amount of sunlight and heat. It is scary to imagine, even for a moment, what it would be like if there were no such 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 sun's rays 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 hit the Earth at an angle of 0 to 90 degrees. The angle of the rays hitting the earth is different, because our planet has the shape of a ball. The larger it is, the lighter and warmer it is.
Thus, if the beam travels at an angle of 0 degrees, it only glides along the surface of the earth, without heating it. Such an 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
If the angle of the sun's rays on the ground is straight, this indicates that
Thus, 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 the geographical latitude. The closer to zero latitude, the closer to 90 degrees the angle of incidence of the rays, the higher the sun is above the horizon, the warmer and lighter.
How the sun changes its height above the horizon
The sun's height above the horizon is not constant. On the contrary, it is always changing. The reason for this lies in the continuous movement of the planet Earth around the star Sun, as well as the rotation of the planet Earth around its own axis. As a result, the day is followed by the night, and the seasons of each other.
The area 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 the least heat and light; here there are concepts like night, which last about six months.
Days of the autumn and spring equinox
Highlighted 4 main astrological dates, 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.
It is southern and illuminated by the sun equally, and the length of the night is equal to the length of the day. When astrological autumn comes in the Northern Hemisphere, in the Southern Hemisphere, on the contrary, it is spring. The same can be said for winter and summer. If in the Southern Hemisphere it is winter, then in the Northern Hemisphere it is summer.
Summer and winter solstice days
June 22 and December 22 are summer days and December 22 is the shortest day and longest night in the Northern Hemisphere, and the winter sun is at its lowest altitude over the horizon for the entire 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 on the horizon, is called the polar night. The shortest night is at 67 degrees latitude and lasts only 2 days, and the longest is at the poles and lasts 6 months!
December is the month of the year with the longest nights in the Northern Hemisphere. People in Central Russia wake up to work in the dark and return at night too. This is a difficult month for many, as the lack of sunlight affects the physical and mental well-being of people. For this reason, depression may even develop.
In Moscow in 2016, the sunrise on December 1 will be at 08.33. In this case, the length of the day will be 7 hours 29 minutes. it will be very early for the horizon, at 16.03. The night will be 16 hours 31 minutes. Thus, it turns out that the longitude of the night is 2 times longer than the length of the day!
This year, the day of the winter solstice is December 21. The shortest day will last exactly 7 hours. Then the same situation will last for 2 days. And already 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 sun will rise in December at exactly 9 o'clock, which is 27 minutes later than December 1st
June 22 is the day of the summer solstice. Everything happens exactly the opposite. For the whole year, it is on this date that 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. A polar day begins beyond the Arctic Circle, the sun does not set over the horizon at the North Pole for 6 months. Mysterious white nights begin in St. Petersburg in June. They last from about mid-June for two to three weeks.
All of these 4 astrological dates can vary by 1-2 days, since the solar year does not always coincide with the calendar year. Also, offsets 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 above the horizon over a specific area of the earth's surface has changed, climatic conditions and seasons change.
For example, in the Far North, the sun's rays fall at a very small angle and only slide 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 icy 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 and tropical. Seasonal fluctuations are also practically not felt in the equator area, in these areas there is eternal summer.
Measuring the height of the sun above the horizon
As they say, all ingenious is simple. So it is here. A device for measuring the height of the sun above the horizon is elementary. It is a horizontal surface with a pole in the middle 1 meter long. 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. You need 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 will be the angle at which the sun is above 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.