Rotation of the earth around its axis

Our planet is in constant motion, it revolves around the Sun and its own axis. The earth's axis is an imaginary line drawn from the North to the South Pole (they remain motionless during rotation) at an angle of 66 0 33 ꞌ with respect to the plane of the Earth. People cannot notice the moment of rotation, because all objects are moving in parallel, their speed is the same. It would look exactly the same as if we were sailing on a ship and did not notice the movement of objects and objects on it.

A full rotation around the axis is completed within one sidereal day, consisting of 23 hours 56 minutes and 4 seconds. During this interval, then one or the other side of the planet turns towards the Sun, receiving from it a different amount of heat and light. In addition, the rotation of the Earth around its axis affects its shape (flattened poles are the result of the planet's rotation around its axis) and the deviation when bodies move in a horizontal plane (rivers, currents and winds of the Southern Hemisphere deviate to the left, Northern - to the right).

Linear and angular speed of rotation

(Earth rotation)

The linear speed of the Earth's rotation around its axis is 465 m/s or 1674 km/h in the equatorial zone, as we move away from it, the speed gradually slows down, at the North and South Poles it is equal to zero. For example, for citizens of the equatorial city of Quito (the capital of Ecuador in South America), the rotation speed is just 465 m / s, and for Muscovites living on the 55th parallel north of the equator - 260 m / s (almost half as much) .

Every year, the speed of rotation around the axis decreases by 4 milliseconds, which is associated with the influence of the Moon on the strength of sea and ocean ebb and flow. The pull of the Moon "pulls" the water in the opposite direction to the Earth's axial rotation, creating a slight frictional force that slows the rotation rate by 4 milliseconds. The rate of angular rotation remains the same everywhere, its value is 15 degrees per hour.

Why does day turn into night

(The change of night and day)

The time of a complete rotation of the Earth around its axis is one sidereal day (23 hours 56 minutes 4 seconds), during this time period the side illuminated by the Sun is first “in the power” of the day, the shadow side is at the mercy of the night, and then vice versa.

If the Earth rotated differently and one side of it was constantly turned towards the Sun, then there would be a high temperature (up to 100 degrees Celsius) and all the water would evaporate, on the other side, frost would rage and the water would be under a thick layer of ice. Both the first and second conditions would be unacceptable for the development of life and the existence of the human species.

Why do the seasons change

(Change of seasons on earth)

Due to the fact that the axis is tilted with respect to the earth's surface at a certain angle, its sections receive different amounts of heat and light at different times, which causes the change of seasons. According to the astronomical parameters necessary to determine the time of year, some points in time are taken as reference points: for summer and winter, these are the days of the solstice (June 21 and December 22), for spring and autumn - the Equinoxes (March 20 and September 23). From September to March, the Northern Hemisphere is turned towards the Sun for less time and, accordingly, receives less heat and light, hello winter-winter, the Southern Hemisphere at this time receives a lot of heat and light, long live summer! 6 months pass and the Earth moves to the opposite point of its orbit and the Northern Hemisphere already receives more heat and light, the days become longer, the Sun rises higher - summer is coming.

If the Earth were located in relation to the Sun exclusively in a vertical position, then the seasons would not exist at all, because all points on the half illuminated by the Sun would receive the same and uniform amount of heat and light.