Very many features of life that are familiar to us from childhood are the result of processes of 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 structure created for the convenience of describing motion. If you mentally draw a line through the poles, this will be the axis of the Earth. The rotation around it is one of the two main movements of the planet.
The axis is not 90 ° with the ecliptic plane (the plane of the Earth's rotation 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 how its movement around the axis looks if you observe it at the North Pole.
Irrefutable evidence
It was once believed that our planet was motionless, and the stars fixed in the sky revolve around it. For quite a long time in history nobody was interested in how fast the Earth revolves in orbit or around an axis, since the very concepts of “axis” and “orbit” did not fit into the scientific knowledge of that period. An experimental proof of the fact of the constant motion of the Earth around its axis was obtained in 1851 by Jean Foucault. It finally convinced everyone who had doubts about this in the century before last.
The experiment was conducted in the Paris Pantheon, under the dome of which a pendulum and a circle with divisions were placed. Swinging, the pendulum with each new movement shifted by several divisions. This is only possible if the planet rotates.
Speed
How fast does the earth rotate around its axis? It is rather difficult to give an unambiguous answer to this question, since the speed of various 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 overcomes 15º in an hour.
The Earth’s rotation speed is associated with the duration of the day. The length of time for which our planet makes one revolution around an axis is determined in two ways. To determine the so-called stellar or sidereal days, any star except the Sun is selected as a reference system. They last 23 hours 56 minutes and 4 seconds. If our star is taken as the starting point, then the day is called sunny. Their average value is 24 hours. It varies somewhat depending on the position of the planet relative to the luminary, which affects both the speed of rotation around the axis and the speed with which the Earth rotates in orbit.
Around the center
The second most important planetary motion is its “orbit” in orbit. Invariable movement along a slightly elongated trajectory is felt by people most often by changing seasons. The speed with which the Earth moves around the Sun is primarily expressed in units of time for us: 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 in February there is an extra day. It represents the sum of the hours accumulated during this time that were not included in the accepted 365 days of the year.
Trajectory features
As already noted, the speed with which the earth rotates in orbit is related to the characteristics of the latter. The trajectory of the planet is different from the ideal circle, it is slightly elongated. As a result, the Earth is either approaching the luminary or moving away from it. When the minimum distance separates the planet and the Sun, this position is called perihelion. Maximum removal corresponds to aphelion. The first falls on January 3, the second on July 5. And for each of these points, the question is: “At what speed does the Earth rotate in orbit?” - has his own answer. For aphelion it is 29.27 km / s, for perihelion - 30.27 km / s.
Day length
The speed with 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 is constantly changing its position in the sky: the points of sunrise and sunset are shifting, the height of the sun is becoming slightly different above the horizon at noon. As a result, the length of the day and night changes.
These two values coincide only at the equinox, when the center of the sun crosses the celestial equator. In this case, the tilt of the axis is neutral with respect to the luminary, and its rays plummet to the equator. The vernal equinox falls on March 20-21, the autumn equinox - on September 22-23.
Solstice
Once a year, the day reaches its maximum in duration, and after six months - the minimum. These dates are commonly called solstices. Summer falls on June 21-22, and winter - on December 21-22. In the first case, our planet is so located in relation to the luminary that the northern edge of the axis looks in the direction of the sun. As a result, the rays plummet on the northern tropic and illuminate the entire area 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
The position in orbit does not only affect how fast the earth moves around the sun. As a result of the change in the distance separating from the luminary, as well as the tilt of the planet's axis, solar radiation is unevenly distributed throughout the year. And this, in turn, becomes the reason for the change of seasons. Moreover, the duration of the winter and summer seasons is different: the first is 179 days, and the second is 186. The same inclination of the axis relative to the ecliptic plane leads to this mismatch.
Light belts
Orbiting the Earth has another consequence. Annual movement leads to a change in the position of the Sun above the horizon, as a result of which light belts formed on the planet:
Hot are located on 40% of the Earth, between the South and North tropics. As the name implies, the most heat comes here.
Temperate zones - between the Arctic Circle and the Tropics - are characterized by a pronounced change of seasons.
The polar belts located beyond the Arctic circles are characterized by low temperature throughout the year.
The motion of the planets as a whole and, in particular, the speed with which the earth rotates in orbit, also affect other processes. Among them, the course of rivers, the change of seasons, certain rhythms of life of plants, animals and humans. In addition, the rotation of the Earth, due to its effect on light 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 associated with the movement of the planet, are studied in school. However, if you think about it, they are completely unobvious. When such an idea comes to mind, I would like to thank from the bottom of my heart those scientists and researchers who, in many respects, thanks only to their extraordinary mind, were able to discover the laws of the cosmic life of the Earth, describe them, and then prove and explain to the rest of the world.