Translation and rotation it's both Earth movements that determine the duration of days and years.
Earth is in continuous movement. It travels, with the rest of the planets and bodies of the Solar System, rotating around the center of our galaxy, the Milky Way, which also does not stand still. However, these movements affect us little in our daily lives.
More important, for us, is the movement that it makes describing its orbit around the Sun, since it determines the year and the change of seasons. And, even more, the rotation of the Earth around its own axis, which causes day and night, that determines our schedules and biorhythms and that, in short, is an inexcusable part of our lives.
The translation movement: the year
Through the movement of the Earth, the Earth moves around the Sun, driven by gravitation, in 365 days, 5 hours and 57 minutes, equivalent to 365.2422 days, which is the duration of the year.
Our planet describes an elliptical path of 930 million kilometers, at an average distance from the Sun of 150 million kilometers. The Sun is in one of the foci of the ellipse. The average Sun-Earth distance is 1 U.A. (Astronomical Unit), which is equivalent to 149,675,000 km.
As a result of that very long road, the Earth travels at a speed of 29.5 kilometers per second, traveling in an hour 106,000 kilometers, or 2,544,000 kilometers a day.
The eccentricity of the Earth's orbit causes the distance between the Earth and the Sun to vary over the course of a year. At the beginning of January the Earth reaches its maximum proximity to the Sun and is said to pass through the perihelion. At the beginning of July it reaches its maximum distance and is in aphelion. The distance between the Earth and the Sun in the perihelion is 142,700,000 kilometers and the Earth-Sun distance in the aphelion is 151,800,000 kilometers.
The rotation movement: the day
Every 24 hours (every 23 h 56 minutes), the Earth makes a complete turn around an ideal axis that passes through the poles. It turns in a West-East direction, in a direct direction (counterclockwise), producing the impression that it is the sky that revolves around our planet.
This movement, called rotation, is due to the succession of days and nights, being during the day the time in which our horizon appears illuminated by the Sun, and at night when the horizon remains hidden from the sun's rays.
Half of the earth globe will be illuminated, in that half it is daytime while on the dark side it is night. In their rotation movement, the different continents pass from day to night and night to day.
On the next page we talk about other movements.
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