Earth makes two different movements: the translation around the Sun and rotating on its axis. To make the first uses an average speed of 29.76 kilometers per second and takes 365 days, 6 hours, 9 minutes and 24 seconds to complete an ellipse. The additional time for 365 days generates an extra day every four years, and leads the leap year. In this journey, called Revolution, traces an ellipse. On January 2 is in the position closest to the Sun, called perihelion point proximity and on the 3rd of July is the peak of withdrawal, called aphelion. Rotational motion is true east and west Earth turns a full circle in 23 hours, 56 minutes and 4 seconds. This movement forms the basis of measurement of time, whose unit is day. The part of the land surface that faces the Sun is called day, which is back, night.
The Earth in its motion of revolution around the Sun, remains tilted. For this reason receives, slanting sunlight that changes every day. Thus arise the four seasons.
The first scientist who proved that the planets move around the sun drawing an ellipse Kepler was a German mathematician, who lived from años1571 and 1630.