Motions of the Earth
Earth is the only planet which supports life. The earth has two types of motions, namely rotation and revolution.
Rotation is the movement of the earth on its axis. The movement of the earth around the sun in a fixed path or orbit is called Revolution. Axis is inclined at an angle of 23.5° from the vertical plane or an angle of 66.5° from the orbital plane. Earth takes approximately 24 hours to complete one rotation. The period of rotation is known as the Earth day.
On June 21, the Northern Hemisphere experiences longest day and shortest night and the Southern Hemisphere experiences longest night and shortest day.
On December 21, the Northern Hemisphere experiences longest night and shortest day and the Southern Hemisphere experiences longest day and shortest night.
Earth completes its revolution around the Sun in 365 days and 6 hours (365.242199 mean solar days). Earth's orbital speed averages about 29.8 km/s. We experience different seasons as the tilted Earth revolves around the Sun. On January 3, the Earth is closest to the Sun (147.3 million km) know as Perihelion. Earth is the farthest from the Sun at 152.1 million km on July 4, know as Aphelion.