Rotation and Revolution

This article describes about the two most important movements of the earth, Rotation and Revolution, the effects of each and the difference between them.

Rotation and Revolution

The terms rotation and revolution refer to the various movements of the earth around its own axis as well as on its orbit around the sun. Both these movements has it’s own significance as they are the primary causes for the different weather phenomenon occurring on the earth as well as the occurrence of day and night.




What is Rotation?

Rotation refers to the spinning of any object around its own axis. Any celestial body like the planets, satellites or stars rotates around its center of mass and has their own speed and time.

Showing the Tilt of the axis and earth's rotation

Figure 1: Showing the Tilt of the axis and earth’s rotation

The earth rotates around its axis at an angle of 23.5 degrees relative to its orbital plane within a period of 24 hours or one day. This allows the sunlight to reach the surface of the earth at different times throughout the day. Because of this tilt in axis the equator or 0-degree latitude has almost equal amount of daylight and darkness (12 hours of day and 12 hours of night) while the poles experience 6 months of daylight and six months of darkness. The tilt of the earth on its axis is the primary reason we experience the different seasons within a year.

Also, not every planet rotates in the same direction. Our planet Earth, rotates on its axis from West to East. A list of planets and their time taken to complete one full rotation as well as their respective directions are mentioned below:

Rotation causing night and day - Rotation and Revolution

Figure 2: Rotation causing night and day




What is Revolution?

As the earth rotates from east to west on its axis, it also travels around the Sun in a fixed path known as its orbit. This is due to the gravitational effect of the sun that all the celestial bodies revolve around the Sun in their fixed orbits.

Showing the different positions of the Earth on its Orbit - Rotation and Revolution

Figure 3: Showing the different positions of the Earth on its Orbit

The earth takes almost 365.24 days to revolve around the sun on its orbit. We must also know that these orbits are imaginary lines or pathways which are slightly elliptical in shape and no orbits cross the path of another planet’s orbit.

A list of planets and the time they take to travel one full round around the sun is given below.

What is the difference between Rotation and Revolution?

Rotation

  • Rotation is the movement of a body around the centre of mass on its axis.
  • Rotation causes day and night
  • The Earth takes 24 hours to complete one rotation on its axis
  • The Speed of rotation is least at the equator and maximum at the poles

Revolution

  • Revolution is the movement of any celestial body around the Sun on its orbit
  •  Revolution causes the change of seasons
  • The Earth takes almost 365 days to complete one revolution around the Sun
  • Speed of revolution is highest when the earth is closest to the sun and least when away from the sun. This is due to the elliptical shape of the Orbit

Thus we understand that both the movements of Rotation and Revolution causes the change of the length of the day, the seasons and many other geographical phenomenon and are extremely significant for life on earth.

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