For an observer located in the Northern Hemisphere, for example, in the European part of Russia, the Sun usually rises in the east and rises to the south, occupying the most high position in the sky, then slopes to the west and disappears behind the horizon. This movement of the Sun is only visible and is caused by the rotation of the Earth around its axis. If you look at the Earth from above in the direction of the North Pole, it will rotate counterclockwise. At the same time, the Sun remains in place, the appearance of its movement is created due to the rotation of the Earth.
Annual rotation of the Earth
The Earth also rotates counterclockwise around the Sun: if you look at the planet from above, from the North Pole. Because earth's axis has an inclination relative to the plane of rotation, as the Earth rotates around the Sun, it illuminates it unevenly. For some areas sunlight hits more, others get less. Thanks to this, the seasons change and the length of the day changes.
Spring and autumn equinox
Twice a year, on March 21 and September 23, the Sun illuminates the Northern and Southern Hemispheres equally. These moments are known as the autumn equinox. In March, autumn begins in the Northern Hemisphere, and autumn in the Southern Hemisphere. In September, on the contrary, autumn comes to the Northern Hemisphere, and spring to the Southern Hemisphere.
Summer and winter solstice
In the Northern Hemisphere, on June 22, the Sun rises highest above the horizon. The day has the longest duration, and the night on this day is the shortest. The winter solstice occurs on December 22 - the day has the most short duration, and the night is as long as possible. IN Southern Hemisphere everything happens the other way around.
polar night
Due to the tilt of the earth's axis, the polar and subpolar regions of the Northern Hemisphere are winter months find themselves without sunlight - the Sun does not rise above the horizon at all. This phenomenon is known as polar night. A similar polar night exists for the circumpolar regions of the Southern Hemisphere, the difference between them is exactly six months.
What gives the Earth its rotation around the Sun
The planets cannot help but revolve around their stars - in otherwise they would simply be drawn in and burned. The uniqueness of the Earth lies in the fact that its axis tilt of 23.44° turned out to be optimal for the emergence of all the diversity of life on the planet.
It is thanks to the tilt of the axis that the seasons change, there are different climatic zones, providing the diversity of the earth's flora and fauna. Changes in the heating of the earth's surface provide movement air masses, which means precipitation in the form of rain and snow.
The distance from the Earth to the Sun of 149,600,000 km also turned out to be optimal. A little further, and water on Earth would only be in the form of ice. Any closer and the temperature would have been too high. The very emergence of life on Earth and the diversity of its forms became possible precisely thanks to the unique coincidence of so many factors.
The average distance from the Earth to the Sun is approximately 150 million kilometers. But since rotation of the earth around the sun occurs not along a circle, but along an ellipse, then in different time Years, the Earth is either a little further from the Sun or a little closer to it.
In this real photo, taken using slow motion, we see the path the Earth takes in 20-30 minutes relative to other planets and galaxies, rotating around its axis.
Change of seasons
It is known that in summer, during the hottest time of the year - in June, the Earth is approximately 5 million kilometers further from the Sun than in winter, in the coldest time of the year - in December. Hence, change of seasons occurs not because the Earth is further or closer to the Sun, but for another reason.
The earth is at its own forward movement around the Sun constantly maintains the same direction of its axis. And during the progressive rotation of the Earth around the Sun in orbit, this imaginary Earth’s axis is always inclined to the plane earth's orbit. The reason for the change of seasons is precisely that the Earth's axis is always inclined to the plane of the Earth's orbit in the same way.
Therefore, on June 22, when the longest day of the year occurs in our hemisphere, the Sun illuminates and North Pole, and the South Pole remains in darkness, since the sun's rays do not illuminate it. When is summer here in the Northern Hemisphere? long days And short nights, in the Southern Hemisphere, on the contrary, there are long nights and short days. Consequently, it is winter there, where the rays fall “obliquely” and have low calorific value.
Temporal differences between day and night
It is known that the change of day and night occurs as a result of the rotation of the Earth around its axis (more details:). A temporal differences between day and night depend on the rotation of the Earth around the Sun. In winter, on December 22, when the longest night and shortest day begin in the Northern Hemisphere, the North Pole is not illuminated by the Sun at all, it is “in darkness,” and the South Pole is illuminated. In winter, as you know, residents of the Northern Hemisphere have long nights and short days.
On March 21–22, day is equal to night, it comes the vernal equinox ; the same equinox - already autumn– sometimes on September 23rd. These days, the Earth occupies such a position in its orbit relative to the Sun that the sun's rays simultaneously illuminate both the North and South poles, and they fall vertically on the equator (the Sun is at its zenith). Therefore, on March 21 and September 23, any point on the surface globe Illuminated by the Sun for 12 hours and in darkness for 12 hours: all over the globe day is equal to night.
Climate zones of the Earth
The rotation of the Earth around the Sun also explains the existence of various climatic zones Earth. Due to the fact that the Earth has a spherical shape and its imaginary axis is inclined to the plane of the earth's orbit always at the same angle, different parts of the earth's surface are heated and illuminated differently sun rays. They fall on separate areas of the surface of the globe at different angles of inclination, and as a result their calorific value is different zones The surface of the Earth is not the same. When the Sun is low above the horizon (for example, in the evening) and its rays fall on earth's surface at a slight angle, they heat very weakly. On the contrary, when the Sun is high above the horizon (for example, at noon), its rays fall on the Earth at a large angle, and their calorific value increases.
Where the Sun on some days is at its zenith and its rays fall almost vertically, there is the so-called hot belt. In these places, animals have adapted to the hot climate (for example, monkeys, elephants and giraffes); Tall palm trees and bananas grow there, pineapples ripen; there, under the shadow of the tropical Sun, with their crown spread wide, there stand gigantic baobab trees, the thickness of which reaches 20 meters in girth.
Where the Sun never rises high above the horizon are two cold belts with poor flora and fauna. Here is the animal and vegetable world monotonous; large spaces are almost devoid of vegetation. Snow covers vast expanses. Between the hot and cold zones there are two temperate zones , which occupy largest spaces surface of the globe.
The rotation of the Earth around the Sun explains the existence five climate zones: one hot, two moderate and two cold.
The hot zone is located near the equator, and its conventional boundaries are the northern tropic (Tropic of Cancer) and the southern tropic (Tropic of Capricorn). Conditional boundaries cold belts are the northern and southern polar circles. The polar nights last there for almost 6 months. There are days of the same length. There is no sharp boundary between thermal zones, but there is a gradual decrease in heat from the equator to the South and North Poles.
Around the North and South Poles, vast spaces are occupied by continuous ice fields. In the oceans washing these inhospitable shores, colossal icebergs float (more details:).
Explorers of the North and South Pole
Reach Northern or South Pole has long been a man's daring dream. Brave and tireless Arctic explorers have made these attempts more than once.
Such was the Russian explorer Georgiy Yakovlevich Sedov, who in 1912 organized an expedition to the North Pole on the ship “St. Foka." The tsarist government was indifferent to this large enterprise and did not provide adequate support to the brave sailor and experienced traveler. Due to lack of funds, G. Sedov was forced to spend the first winter on Novaya Zemlya, and the second on. In 1914, Sedov, together with two companions, finally undertook last try reach the North Pole, but the state of health and strength failed this daring man, and in March of the same year he died on the way to his goal.
Have equipped ourselves more than once large expeditions on ships to the Pole, but these expeditions also failed to reach their goal. Heavy ice“fettered” the ships, sometimes broke them and carried them away with their drift far in the direction opposite to the intended path.
Only in 1937 was it first delivered to the North Pole by airship. Soviet expedition. The brave four - astronomer E. Fedorov, hydrobiologist P. Shirshov, radio operator E. Krenkel and the old sailor leader of the expedition I. Papanin - lived on a drifting ice floe for 9 months. The huge ice floe sometimes cracked and collapsed. Brave explorers were more than once in danger of dying in the waves of cold weather. arctic sea, but despite this, they produced their Scientific research where no man has ever set foot before. Important research was carried out in the fields of gravimetry, meteorology and hydrobiology. The existence of five climate zones associated with the rotation of the Earth around the Sun has been confirmed.
Ecology
The Earth goes through four seasons as it makes one revolution around the Sun, all of which occurs along with the waxing and waning of daylight hours during the six months that occur between the winter and summer solstice.
We also live in a 24-hour daily cycle during which the Earth rotates on its axis; moreover, there is a 28-day cycle of the Moon's rotation around the Earth. These cycles repeat endlessly. However, there are many subtleties hidden in and around these cycles that most people are unaware of, cannot explain, or simply do not notice.
10. Highest point
Fact: The sun does not necessarily reach its highest point at noon.
Depending on the time of year, the position of the Sun at its highest point varies. This happens for two reasons: the Earth's orbit is an ellipse, not a circle, and the Earth, in turn, is tilted towards the Sun. Since the Earth almost always rotates with same speed, and its orbit is certain times years faster than others, sometimes our planet either overtakes or lags behind its circular orbit.
Changes due to the Earth's tilt are best viewed by imagining points close together on the Earth's equator. If you tilt the circle of dots by 23.44 degrees (the current tilt of the Earth), you will see that all the dots except those currently located on the equator and tropics will change their longitude. There are also changes in the time the Sun is at its most high point, they are also associated with geographic longitude, in which the observer is located, however, this factor is constant for each longitude.
9. Sunrise direction
Fact: Sunrise and sunset do not change direction immediately after the solstice.
Most people believe that in the northern hemisphere, the earliest sunset occurs around the December solstice and the latest sunset occurs around the June solstice. Actually this is not true. Solstices are simply dates that indicate the length of the shortest and longest daylight hours. However, changes in time during the midday period entail changes in the periods of sunrise and sunset.
During the December solstice, noon occurs 30 seconds late each day. Since there is no change in daylight hours during the solstice, both sunset and sunrise are delayed by 30 seconds each day. Since sunset is late during the winter solstice, the earliest sunset already has time to “happen.” At the same time, on the same day the sunrise also comes late, you have to wait for the latest sunrise.
It also happens that the latest sunset occurs after a short time after the summer solstice, and most early sunrise occurs shortly before the summer solstice. However, this difference is not as significant compared to the December solstice because the change in noon time due to eccentricity at this solstice depends on the changes in noon due to obliquity, but the overall rate of change is positive.
8. Elliptical orbit of the Earth
Most people know that the Earth revolves around the Sun in an ellipse, not a circle, but the eccentricity of the Earth's orbit is approximately 1/60. A planet that orbits its sun always has an eccentricity between 0 and 1 (counting 0, but not counting 1). An eccentricity of 0 indicates that the orbit is a perfect circle with the sun at the center and the planet rotating at a constant speed.
However, the existence of such an orbit is extremely unlikely, since there is a continuum possible values eccentricity, which in a closed orbit is measured by dividing the distance between the sun and the center of the ellipse. The orbit becomes longer and thinner as the eccentricity approaches 1. A planet always spins faster as it gets closer to the Sun, and slows down as it moves away from it. When the eccentricity is greater than or equal to 1, the planet circles its sun once and flies off into space forever.
7. Earth wobbles
The earth periodically goes through vibrations. This is explained mainly by the influence of gravitational forces, which “stretch” the equatorial bulge of the Earth. The Sun and Moon also exert pressure on this bulge, thereby creating vibrations of the Earth. However, for everyday astronomical observations these effects are negligible.
The Earth's tilt and longitude have a period of 18.6 years, which is the time it takes for the Moon to circle through the nodes, creating wobbles ranging from two weeks to six months. The duration depends on the Earth's orbit around the Sun and on lunar orbit around the Earth.
6. Flat Earth
Fact (sort of): The Earth is truly flat.
The Catholics of Galileo's era were perhaps only slightly right in believing that the Earth was flat. It so happens that the Earth has an almost spherical shape, but it is slightly flattened at the poles. The equatorial radius of the Earth is 6378.14 kilometers, while its polar radius is 6356.75 kilometers. Consequently, geologists had to come up with different versions latitude.
Geocentric latitude is measured by visual latitude, that is, it is the angle relative to the equator to the center of the Earth. Geographic latitude- this is latitude from the point of view of the observer, namely this is the angle consisting of the equator line and a straight line passing under a person’s feet. Geographic latitude is the standard for constructing maps and determining coordinates. However, measuring the angle between the Earth and the Sun (how far north or south the Sun shines on the Earth depending on the time of year) is always done in a geocentric system.
5. Precession
The earth's axis points towards the top. In addition, the ellipse that forms the Earth's orbit rotates very slowly, making the shape of the Earth's movement around the Sun very similar to a daisy.
In connection with both types of precession, astronomers have identified three types of years: sidereal year(365, 256 days), which has one orbit relative to distant stars; the anomalous year (365.259 days), which is the period of time during which the Earth moves from its closest point (perihelion) to its farthest point from the Sun (aphelion) and back; tropical year(365, 242 days), lasting from one day of the vernal equinox to the next.
4. Milankovitch cycles
Astronomer Milutin Milankovitch discovered in the early 20th century that the Earth's tilt, eccentricity and precession are not constant values. Over a period of about 41,000 years, the Earth completes one cycle, during which it tilts from 24.2 - 24.5 degrees to 22.1 - 22.6 degrees and back. Currently, the Earth's axial tilt is decreasing, and we are exactly halfway to the minimum tilt of 22.6 degrees, which will be reached in about 12,000 years. The Earth's eccentricity follows a much more erratic cycle, lasting 100,000 years, during which time it fluctuates between 0.005 and 0.05.
As already mentioned, its current indicator is 1/60 or 0.0166, but now it is declining. It will reach its minimum in 28,000 years. He suggested that these cycles cause glacial period. When the values of inclination and eccentricity are particularly high, and the precession is such that the Earth is tilted away from the Sun, or towards the Sun, then we end up with too cold winter V western hemisphere, at the same time, in spring or summer it melts too much a large number of ice.
3. Slow rotation
Due to friction caused by tides and stray particles in space, the Earth's rotation speed gradually slows down. It is estimated that with each century, the Earth takes five hundredths of a second longer to rotate once. At the beginning of the Earth's formation, a day lasted no more than 14 hours instead of today's 24. The slowing of the Earth's rotation is the reason why every few years we add a fraction of a second to the length of the day.
However, the time when our 24-hour system will cease to be relevant is so far away that almost no one makes assumptions about what we will do with the emerging extra time. Some believe that we could add a period of time to each day, which could eventually give us a 25-hour day, or change the length of the hour by dividing the day into 24 equal parts.
2. The moon is moving away
Every year the Moon moves away from its Earth's orbit by 4 centimeters. This is due to the tides that it “brings” to Earth.
The Moon's gravity acting on the Earth distorts earth's crust by a few centimeters. Because the Moon rotates much faster than its orbits, the bulges pull the Moon along with them and pull it out of its orbits.
1. Seasonality
Solstice and equinox symbolize the beginning of their respective seasons, not their midpoint. This is because the Earth takes time to heat up or cool down. Thus, seasonality is distinguished by the corresponding length of daylight. This effect is called seasonal lag and varies depending on geographical location observer. The further a person travels from the poles, the less tendency there is to lag behind.
In many North American cities, the lag is typically about a month, resulting in the coldest weather occurring on January 21st and the warmest weather on July 21st. However, people who live in such latitudes also enjoy the warm summer days at the end of August, wearing light clothing and even going to the beach. Moreover, the same date on the “other side” of the summer solstice will correspond to approximately April 10. Many people will remain only in anticipation of summer.
> > > Earth's orbit
Earth's orbit around the Sun in the Solar System: description of elliptical motion, changing seasons of the planet, spring and autumn equinoxes, Lagrange points.
In the 16th century, Nicolaus Copernicus made a real revolution, proving that in the center solar system The Sun is set, and other objects rotate around ( heliocentric system). Then what about circular Earth's orbit?
Orbital characteristics of the Earth
The Earth rotates around the Sun in an orbit with an acceleration of 108,000 km/h, spending 365.242199 per pass sunny days. Yes, that's why we need to add a day every 4 years.
The distance from the Earth to the Sun changes as it passes. The planet is approaching (perihelion) at 147,098,074 km. The average distance is 149.6 million km. The greatest distance (aphelion) is 152,097,701 km.
If you live in the northern hemisphere, you may have noticed that heat/cold does not agree with the distance principle because it depends on the axial tilt.
Elliptical orbit of the Earth
No, the planet's route is not a perfect circle. We are rotating along an elongated ellipse. This was first described by Johannes Kepler. You can study the Earth's orbital movement in the diagram.
The scientist measured the orbits of Earth and Mars and realized that they periodically accelerated and slowed down. This coincided with aphelion and perihelion, which means the distance from the star is based on orbital speed(no circular orbit).
To characterize the nature of elliptical orbits, researchers use the concept of eccentricity - from 0 to 1. If it is close to 0, then we have practically a circle. The Earth’s is 0.02, that is, close to circular.
Seasonal orbital changes
The tilt of the Earth's axis plays a big role. Our 4 seasons (seasons) appeared only due to the fact that the axis rotation is at an angle of 23.4°. This leads to the solstice and equinox.
That is, if North hemisphere departed from the Sun, then goes into winter time, and in the south there is summer heat. After 6 months they change places. The winter solstice occurs on December 21, the summer solstice on June 21, the spring equinox on approximately March 20, and the autumn equinox on September 23.
About Lagrange points
What are Lagrange points in space? it's the same interesting point. There are 5 points on our orbital path where the total gravitational force between the Earth and the Sun guarantees centripetal force.
The points are marked L1 to L5. L1, L2 and L3 are set in a straight line from us to the Sun. They are not stable, which means the satellite sent there will move.
L4 and L5 are at the corners of two triangles, where the Sun and Earth are located below. Due to their stability they are the best places for the position of probes and telescopes.
It is important for us to study the orbit not only of our home planet, but also of alien worlds in the solar system. Because distance from a star often plays a role key role presence of life on Earth.
Our planet is in constant motion. The Earth rotates around its axis and at the same time moves around the Sun. The Earth makes one revolution around its axis in one sidereal day, the duration of which differs from the astronomical day by 3 minutes 56 seconds less. At the same time, the speed of movement of our planet is different latitudes varies. At the poles it is higher than at the equator, which is caused by an increase in centrifugal force on the pluses.
Many people believe that the trajectory of the Earth relative to the center of the solar system is a circle. But this is a misconception. In fact, the Earth's trajectory is elliptical. The average distance from our planet to the Sun is 149,597,870 kilometers. Perihelion, or the part of the orbit closest to the Sun, is located at a distance of about 147,000,000 km, aphelion (the point of the orbit farthest from the sun) - at a distance of about 152,000,000 km.
For a long time, the geocentric theory was considered official. It says that the Sun, as well as all the others celestial bodies and the stars move around the Earth. The first opponents of this theory appeared already in the 6th century BC. However, their research has not been widely disseminated.
The first serious work proving the movement of the Earth around our luminary was written in the 16th century by Nicolaus Copernicus. He was supported by many contemporaries, among whom were astronomers, physicists, philosophers and theologians. For a long time, the heliocentric (that is, the opposite of geocentric) theory was rejected by official level. Her main opponent was Catholic Church, whose representatives believed that the statement about the rotation of our planet around the Sun contradicts the biblical canons.
Constant changes in the amount of light and heat received from the Sun entail a change in seasons. The Earth makes a revolution around the star in 365.25 days. Moreover, every day the Sun moves 1 degree per day relative to the stars. This process can be easily observed anywhere on Earth without any optical instruments.
The sun moves from west to east. And in the spring, for example, we can observe that the sun every day is slightly higher than the horizon line than the day before. As a result, more and more heat reaches the Earth's surface at a given point every day. As a result, winter gradually gives way to summer. However, in the subpolar zone there are areas that do not receive sunlight at all for part of the year, which is why the so-called polar night occurs there. At other times, the Sun, on the contrary, does not fall below the horizon. This phenomenon is called the polar day.
The change in the length of daylight hours as the Earth moves around the Sun is due to the fact that the axis of our planet is tilted relative to the Sun. At those moments when the direction of the Sun and the direction of the earth's axis are perpendicular to each other, the equinox occurs. On these days, the length of daylight is equal to the length of night.
In the Northern Hemisphere, the date falls on March 21, and on September 22-23. observed here from June 20-21 to December 21-22. The first date indicates the maximum duration of daylight in a year, the second - the maximum duration of night. After the winter solstice, the day begins to increase, and after the summer solstice, the day begins to decrease.
In the Southern Hemisphere, the earth's axis has the exact opposite tilt compared to the Northern Hemisphere. Therefore, the seasons here are completely opposite to the northern ones.