It is spherical, however, it is not a perfect ball. Due to rotation, the planet is slightly flattened at the poles; such a figure is usually called a spheroid or geoid - “like the earth.”
The earth is huge, its size is difficult to imagine. The main parameters of our planet are as follows:
- Diameter - 12570 km
- Length of the equator - 40076 km
- The length of any meridian is 40008 km
- The total surface area of the Earth is 510 million km2
- Radius of the poles - 6357 km
- Equator radius - 6378 km
The earth simultaneously rotates around the sun and around its own axis.
The earth rotates around an inclined axis from west to east. Half of the globe is illuminated by the sun, it is day there at that time, the other half is in the shadow, there it is night. Due to the rotation of the Earth, the cycle of day and night occurs. The Earth makes one revolution around its axis in 24 hours - a day.
Due to rotation, moving currents (rivers, winds) are deflected to the right in the northern hemisphere, and to the left in the southern hemisphere.
Rotation of the Earth around the Sun
The Earth rotates around the sun in a circular orbit, completing a full revolution in 1 year. The earth's axis is not vertical, it is inclined at an angle of 66.5° to the orbit, this angle remains constant during the entire rotation. The main consequence of this rotation is the change of seasons.
Let's consider the extreme points of the Earth's rotation around the Sun.
- December 22- winter solstice. The southern tropic is closest to the sun (the sun is at its zenith) at this moment - therefore, it is summer in the southern hemisphere, and winter in the northern hemisphere. Nights in the southern hemisphere are short; on December 22, in the southern polar circle, the day lasts 24 hours, night does not come. In the northern hemisphere, everything is the other way around; in the Arctic Circle, the night lasts 24 hours.
- 22nd of June- day of the summer solstice. The northern tropic is closest to the sun; it is summer in the northern hemisphere and winter in the southern hemisphere. In the southern polar circle, night lasts 24 hours, but in the northern circle there is no night at all.
- March 21, September 23- days of the spring and autumn equinoxes The equator is closest to the sun; day is equal to night in both hemispheres.
Many of the features of life familiar to us since childhood are the result of processes on a cosmic scale. The change of day and night, seasons, the duration of the period during which the Sun is above the horizon are associated with how and at what speed the Earth rotates, with the peculiarities of its movement in space.
Imaginary line
The axis of any planet is a speculative construction, created for the convenience of describing movement. If you mentally draw a line through the poles, this will be the Earth's axis. Rotation around it is one of the two main movements of the planet.
The axis does not make 90º with the plane of the ecliptic (the plane around the Sun), but deviates from the perpendicular by 23º27". It is believed that the planet rotates from west to east, that is, counterclockwise. This is what its movement around the axis looks like when observed in the North pole.
Irrefutable proof
It was once believed that our planet was stationary, and the stars fixed in the sky revolved around it. For quite a long time in history, no one was interested in the speed at which the Earth revolves in orbit or around its axis, since the very concepts of “axis” and “orbit” did not fit into the scientific knowledge of that period. Experimental proof of the fact that the Earth is constantly moving around its axis was obtained in 1851 by Jean Foucault. It finally convinced everyone who still doubted this in the century before last.
The experiment was carried out under a dome in which a pendulum and a circle with divisions were placed. Swinging, the pendulum shifted several notches with each new movement. This is only possible if the planet rotates.
Speed
How fast does the Earth rotate on its axis? It is quite difficult to give an unambiguous answer to this question, since the speed of different geographical points is not the same. The closer the area is to the equator, the higher it is. In the Italian region, the speed value, for example, is estimated at 1200 km/h. On average, the planet travels 15º in an hour.
The length of the day is related to the speed of the Earth's rotation. The length of time during which our planet makes one revolution around its axis is determined in two ways. To determine the so-called sidereal or sidereal day, any star other than the Sun is selected as a reference system. They last 23 hours 56 minutes and 4 seconds. If our luminary is taken as the starting point, then the day is called solar. Their average duration is 24 hours. It varies somewhat depending on the position of the planet relative to the star, which affects both the speed of rotation around its axis and the speed at which the Earth rotates in orbit.
Around the center
The second most important movement of the planet is its “circling” in orbit. Constant movement along a slightly elongated trajectory is felt by people most often due to the change of seasons. The speed at which the Earth moves around the Sun is expressed for us primarily in units of time: one revolution takes 365 days 5 hours 48 minutes 46 seconds, that is, an astronomical year. The exact figure clearly explains why every four years there is an extra day in February. It represents the sum of hours accumulated during this time that were not included in the accepted 365 days of the year.
Trajectory Features
As already noted, the speed at which the Earth rotates in orbit is associated with the characteristics of the latter. The planet's trajectory differs from an ideal circle; it is slightly elongated. As a result, the Earth either approaches the star or moves away from it. When the planet and the Sun are separated by a minimum distance, this position is called perihelion. The maximum distance corresponds to aphelion. The first falls on January 3, the second on July 5. And for each of these points the question: “At what speed does the Earth rotate in orbit?” - has its own answer. For aphelion it is 29.27 km/s, for perihelion it is 30.27 km/s.
Length of day
The speed at which the Earth rotates in its orbit, and in general the movement of the planet around the Sun, have a number of consequences that determine many of the nuances of our lives. For example, these movements affect the length of the day. The sun constantly changes its position in the sky: the points of sunrise and sunset shift, the height of the star above the horizon at noon becomes slightly different. As a result, the length of day and night changes.
These two values coincide only at the equinox, when the center of the Sun crosses the celestial equator. The tilt of the axis turns out to be neutral with respect to the star, and its rays fall vertically onto the equator. The spring equinox falls on March 20-21, the autumn equinox on September 22-23.
Solstice
Once a year a day reaches its maximum length, and six months later it reaches its minimum. These dates are usually called solstice. Summer falls on June 21-22, and winter falls on December 21-22. In the first case, our planet is positioned in such a way in relation to the star that the northern edge of the axis looks in the direction of the Sun. As a result, the rays fall vertically onto and illuminate the entire region beyond the Arctic Circle. In the Southern Hemisphere, on the contrary, the sun's rays reach only the area between the equator and the Arctic Circle.
During the winter solstice, events proceed in exactly the same way, only the hemispheres change roles: the South Pole is illuminated.
Seasons
Orbital position affects more than just how fast the Earth moves around the Sun. As a result of changes in the distance separating it from the star, as well as the tilt of the planet’s axis, solar radiation is distributed unevenly throughout the year. And this, in turn, causes the change of seasons. Moreover, the duration of the winter and summer half-years is different: the first is 179 days, and the second - 186. This discrepancy is caused by the same tilt of the axis relative to the plane of the ecliptic.
Light belts
The Earth's orbit has another consequence. The annual movement leads to a change in the position of the Sun above the horizon, as a result of which belts of illumination are formed on the planet:
Hot regions are located on 40% of the Earth's territory, between the Southern and Northern Tropics. As the name suggests, this is where most of the heat comes.
Temperate zones - between the Arctic Circle and the Tropics - are characterized by a pronounced change of seasons.
The polar zones, located beyond the Arctic Circles, are characterized by low temperatures throughout the year.
The movement of planets in general and, in particular, the speed at which the Earth orbits, also influence other processes. Among them are the flow of rivers, the change of seasons, and certain rhythms of life of plants, animals and humans. In addition, the rotation of the Earth, due to its influence on illumination and surface temperature, affects agricultural work.
Today, what is the speed of rotation of the Earth, what is its distance to the Sun, and other features related to the movement of the planet are studied in school. However, if you think about it, they are not at all obvious. When such a thought comes to mind, I would like to sincerely thank those scientists and researchers who, largely thanks to their extraordinary minds, were able to discover the laws of the cosmic life of the Earth, describe them, and then prove and explain them to the rest of the world.
For a very long time, people thought that our planet was flattened and rested on 3 pillars. A person is unable to notice its rotation while standing on it. The reason for this is the size. They make a huge difference! The size of a person is too insignificant in relation to the size of the globe. Time moved forward, science progressed, and with it people’s ideas about their own planet.
What have we come to today? Is it true that and not the other way around? What other astronomical knowledge is valid in this area? First things first.
Along its axis
Today we know that it simultaneously takes part in two types of motion: the Earth rotates around the Sun and along its own imaginary axis. Yes, exactly the axles! Our planet has an imaginary line that “pierces” the surface of the earth at its two poles. Draw your axis mentally into the sky, and it will pass next to the North Star. That is why this point always seems motionless to us, and the sky seems to be rotating. We think that they are moving from east to west, but we note that it only seems to us! Such movement is visible, since it is a reflection of the planet’s real rotation - along the axis.
The daily rotation lasts exactly 24 hours. In other words, in one day the globe makes one full circle along its own axis. Each of the earth's points first passes through the illuminated side, then through the dark side. And a day later everything repeats again.
For us, it looks like a constant change of days and nights: morning - day - evening - morning... If the planet did not rotate in this way, then on the side facing the light there would be eternal day, and on the opposite side there would be eternal night. Horrible! It's good that this is not so! In general, we figured out the daily rotation. Now let's find out how many times the Earth revolves around the Sun.
Sunny round dance
We also won’t notice this with the naked eye. However, this phenomenon can be felt. We all know very well the warm and cold seasons of the year. But what do they have in common with the movements of the planet? Yes, they have everything in common! The Earth revolves around the Sun in three hundred and sixty-five days, or one year. In addition, our globe is a participant in other movements. For example, together with the Sun and its “colleagues” the planets, the Earth moves relative to its own galaxy - the Milky Way, in turn, moving relative to its “colleagues” - other galaxies.
It is important to know that in the entire Universe nothing is stationary, everything flows and changes! Let us note that the movement of the celestial body we see is just a reflection of a rotating planet.
Is the theory correct?
Today, many people are trying to prove the opposite: they believe that the Earth does not revolve around the Sun, but, on the contrary, the heavenly body revolves around the globe. Some scientists talk about the joint movement of the Earth and the Sun, which occurs relative to each other. Perhaps one day the world's scientific minds will turn all the scientific ideas known today about space upside down! So, all the “i”s are dotted, and you and I learned that around the Sun (at a speed, by the way, about 30 kilometers per second), and it makes a full revolution in 365 days (or 1 year), at the same time Our planet rotates on its axis every day (24 hours).
Even in ancient times, while observing the starry sky, people noticed that during the day the sun, and in the night sky - almost all the stars - repeat their path from time to time. This suggested that there were two reasons for this phenomenon. Either it occurs against the background of a motionless starry sky, or the sky rotates around the Earth. Claudius Ptolemy, an outstanding ancient Greek astronomer, scientist and geographer, seemed to solve this issue by convincing everyone that the Sun and the sky revolve around the motionless Earth. Despite the fact that I couldn’t explain it, many people came to terms with it.
The heliocentric system, based on a different version, won its recognition through a long and dramatic struggle. Giordano Bruno died at the stake, the elderly Galileo admitted the “rightness” of the Inquisition, but “... still it moves!”
Today, the rotation of the Earth around the Sun is considered completely proven. In particular, the movement of our planet in a circumsolar orbit is proven by the aberration of starlight and parallactic displacement with a periodicity equal to one year. Today it has been established that the direction of rotation of the Earth, more precisely, its barycenter, in orbit coincides with the direction of its rotation around its axis, that is, it occurs from west to east.
There are many facts indicating that the Earth moves through space in a very complex orbit. The rotation of the Earth around the Sun is accompanied by its movement around its axis, precession, nutational oscillations and rapid flight together with the Sun in a spiral within the Galaxy, which also does not stand still.
The rotation of the Earth around the Sun, like other planets, takes place in an elliptical orbit. Therefore, once a year, on January 3, the Earth is as close as possible to the Sun and once, on July 5, it moves away from it at its greatest distance. The difference between perihelion (147 million km) and aphelion (152 million km), compared with the distance from the Sun to the Earth, is very small.
Moving in a circumsolar orbit, our planet makes 30 km per second, and the Earth’s revolution around the Sun is completed within 365 days 6 hours. This is the so-called sidereal, or sidereal year. For practical convenience, it is customary to count 365 days a year. “Additional” 6 hours over 4 years add up to 24 hours, that is, one more day. These (accumulated, extra) days are added to February once every 4 years. Therefore, in our calendar, 3 years contain 365 days, and a leap year, the fourth year, contains 366 days.
The Earth's own rotation axis is inclined to the orbital plane at 66.5°. In this regard, during the year the sun's rays fall on every point of the earth's surface under the influence of
y corners. Thus, at different times of the year, points at different points receive unequal amounts of light and heat at the same time. Because of this, in temperate latitudes the seasons have a pronounced character. At the same time, throughout the year, the sun's rays at the equator fall on the earth at the same angle, so the seasons there differ slightly from each other.
Regardless of the fact that the constant movements of our planet are usually imperceptible, various scientific facts have long proven that planet Earth moves along its own strictly defined trajectory not only around the Sun itself, but also around its own axis. This is what determines the mass of natural phenomena observed by people every day, such as the change in time of day and night. Even at this moment, reading these lines, you are in constant motion, a movement that is caused by the movement of your home planet.
Fickle movement
It is interesting that the speed of the Earth itself is not a constant value, for reasons that scientists, unfortunately, have not yet been able to explain, however, it is known for certain that each century the Earth slightly slows down the speed of its normal rotation by an amount equal to approximately 0. 0024 seconds. It is believed that such an anomaly is directly related to a certain lunar attraction, which determines the ebb and flow of the tides, on which our planet also spends a significant share of its own energy, which “slows down” its individual rotation. The so-called tidal protrusions, moving as usual in the direction opposite to the Earth's course, cause the emergence of certain frictional forces, which, in accordance with the laws of physics, are the main braking factor in such a powerful space system as the Earth.
Of course, there is actually no axis; it is an imaginary straight line that helps make calculations.
In one hour, it is believed that the Earth rotates 15 degrees. It’s not hard to guess how long it takes for it to completely turn around its axis: 360 degrees - in one day in 24 hours.
Day at 23 o'clock
It is clear that the Earth rotates around its own axis in the 24 hours familiar to people - an ordinary earthly day, or more precisely - in 23 hours minutes and almost 4 seconds. The movement invariably occurs from the western part to the eastern part and nothing else. It is not difficult to calculate that under such conditions the speed at the equator will reach about 1670 kilometers per hour, gradually decreasing as it approaches the poles, where it smoothly goes to zero.
It is impossible to detect with the naked eye the rotation performed by the Earth at such a gigantic speed, because all surrounding objects move along with people. All planets in the solar system undergo similar movements. For example, Venus has a much lower speed of movement, which is why its days differ from those on Earth by more than two hundred and forty-three times.
The fastest planets known today are considered to be Jupiter and the planet Saturn, completing their full rotation around their axis in ten and ten and a half hours, respectively.
It should be noted that the rotation of the Earth around its axis is an extremely interesting and unknown fact that requires further close study by scientists around the world.