Rotation And Revolution Of The Earth Essay

Earth’s Rotation vs Revolution

Rotation of the earth describes the spinning of the earth around its axis, resulting in the 24 hour phenomenon of day and night over the earth. Revolution on the other hand describes the movement of the earth around the sun over a period of one year, causing seasons to occur.
Rotation of the earth causes difference in time over countries and continents. The parts of the earth that are in front of the sun experience day, while the part of the earth away from the sun has night. During the course of revolution depending upon which hemisphere of the earth is closer to the sun, and which one is farther, we have summer and winter respectively. When both the hemispheres are equidistant from the sun there is spring or autumn or fall.

The rotation of the earth around its axis follows the west to east path. The path of the earth around the sun during revolution is an ellipse rather than a circle and this is the reason why the earth is closer to the sun sometimes and farther from it other times, thus causing seasonal fluctuations in weather known as seasons.

The impact of rotation on earth goes far beyond causing day and night. It in fact impacts upon the shape of the earth, which is an oblate spheroid, ocean depth and tectonic plate movement. The earth rotates around its axis at approximately 15 angular degrees per hour. For one complete revolution the earth takes 365.25 days in a slightly elliptical orbit, which has the sun at one focal point of the ellipse.

Rotation and revolution are terms often erroneously used interchangeably because they mean the same thing in a literal and literary sense. However in geography and astronomy the two terms have entirely different meanings and connotations. From a practical point of view the implications of the two phenomena are enormous. Getting a fix on the earth’s various time zones, the study of tides and seismic activity: all of these are interlined with the earth’s rotation. The climatic seasons on the other hand depend entirely on revolution and this helps us anticipate and prepare for the changes.

From a school child’s perspective, it is fascinating to discover that because of rotation one can have night in India and daytime in the US at the same instant. They would also find it incredible that while it is the peak of winter in London in the month of December, there would be summer in Cape Town in the same month. In fact most cultural, demographic and ecological differences that abound upon this beautiful planet of ours are directly linked to these two celestial phenomena.
While we go about our daily lives do we ever for an instant imagine that we are hurtling through space perched on a rock that spins around itself, while tracing a path around its sun, which itself is part of vast galaxy of stars, one among millions and millions of other galaxies found in the universe. Truly the mind boggles.

1.Rotation of earth takes place on its axis while revolution is its motion around sun.
2.Rotation is completed in 24 hrs while revolution takes 365 days for completion.
3.Due to rotation, there is a difference in the times across nations in the world.

Manisha Kumar. "Difference Between Earth’s Rotation and Revolution." October 11, 2011 < >.

Earth Rotation and Revolution
Oct 17, 2013

Earth is a small blue planet. Earth is just the right distance from the Sun for its temperature to let water exist as a liquid, a solid, and a gas. The presence of water as a liquid on Earth’s surface throughout its long history also enabled life to evolve. Another characteristic of Earth is that it is dynamic. Its interior and surface continually change as a result of its internal heat.

The axis of the Earth  is tilted at an angle of 23 degrees from the vertical. That is, the earth’s axis forms an angle of 23½ degree with the perpendicular to the plane of the earth’s orbit. This means that the earth’s axis makes an angle of 66½ o with the orbital plane. Therefore, the earth is always inclined towards one side while revolving around the sun. The tilting of the Earth’s axis is also called the inclination of earth’s axis. The spherical shape of the earth results in only half of the Earth facing the sun getting the sunlight while, the other half is in darkness. 

The earth moves in space in two distinct ways: 

(i)   Rotation  

     The taking approximately earth rotates on its axis 24 hours to complete one rotation. This has important environmental consequences.

  • Rotation creates a diurnal cycle of light and darkness, temperature, and humidity changes.

  • Rotation requires the creation of standardized time zones. There are 24, one for each hour of the earth's rotation.

  • Rotation causes the tides‐ the twice daily rise and fall of sea level. Tides are complicated because they are the result of both the gravity of the moon and the gravity of the sun. Sometimes the sun and the moon are lined up with the earth, but most of the time they are not. Tides are highest when the earth, sun and moon are in a straight line.

  • The Coriolis Force. Rotation causes a deflection of ocean and air currents. The earth rotates much faster than the winds or currents move. This causes a large deflection in the direction that winds move and ultimately results in rotation around low pressure cells and high pressure cells. It also causes large rotating pools of water in the oceans called gyres. The Coriolis force only operates on large features.

  • At the Equator the eastward velocity is 1700 Km/hr; at the poles it is 0

  • A difference of 1 hour between two meridians which are 15 0apart. 

(ii)   Revolution:

The Earth revolves around the Sun once every 365.242199 mean solar days. The Earth orbits the Sun at a speed of 108,000 km/h. Earth’s perihelion(147,098,074 km) occurs around January 3, and the aphelion around July 4 (152,097,701 km) . 

The position of the earth changes around the sun as follows:

On 21st June, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the Tropic of Cancer. As a result, these areas receive more heat. The areas near the poles receive less heat as the rays of the sun are slanting. The North Pole is inclined towards the sun and the places beyond the Arctic Circle experience continuous daylight for about six months. Since a large portion of the Northern Hemisphere is getting light from the sun, it is summer in the regions north of the equator. The longest day and the shortest night at these places occur on 21st June. At this time winter season occurs in the Southern Hemisphere.

On 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it. As the sun’s rays fall vertically at the Tropic of Capricorn (23½° S), a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights.  

On 21st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox.




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