Hi, welcome to this hall on the topic earth’s rotation and revolution.
- Movement of the Earth
- Rotation of the Earth
- Effect of rotation of the Earth
- Revolution of the Earth.
- Effects of the revolution of the Earth
- Differences between rotation and revolution.
- Revision questions
Movement Of The Earth
The earth moves in space in two different ways. These are:
- Rotation
- Revolution
Rotation Of The Earth
Definition And Its Effect On The Earth: Rotation of the earth is defined as the movement of the earth around the sun on its axis.
- The earth moves or rotate on its axis from West to East.
- The rotating earth is inclined at an angle of 23 ½° along its axis.
- It takes the earth 24 hours (i.e a day) to complete one rotation (i.e the Earth rotate through 360° in every 24 hours).
- The rotation of the earth cause day and night.
- This is why it is said that there are 24 hours in a day. That is, 12 hours of daylight and 12 hours of darkness. However, this division does not occur at all times in all places.
- It rotates through 15° in 1 hour or 1° in 4 minutes.
Effect Of Rotation Of The Earth
- Day and night: As the Earth rotate, only one part of the earth surface facing the sun receives the rays of the sun and experience daylight (day) while the other part of the earth backing The sun rays will experience darkness (night).
- Deflection of winds and ocean Currents: The rotation of the Earth causes winds and ocean currents to be deflected to the right of the direction in which they move in the Northern hemisphere and, to the left of this direction in the Southern hemisphere.
- Apparent sunrise and sunset: During rotation of the Earth, part of the earth that emerges from the darkness into the rays of the Sun experiences sunrise while the part that is moving away from the sun’s rays to darkness will experience sunset.
- Time differences from place to place: The Earth rotate through 360° in every 24 hours which means that for every one hour, it passes through 15°. Since the earth moves from West to East, it means that for every 15°, the east is always one hour ahead of time while the West is always one hour behind time.
- Daily rising and falling of the tides: During rotation of the Earth, it results in the rising and falling in the level of water in the seas and oceans. Owing to rotation of the Earth, the tides-producing forces cause the surface of the water to oscillate, resulting in The rising and falling in the level of water in the seas and oceans.
- Dawn and Twilight: Dawn refers to the brief period between sunrise and full daylight while Twilight refers to the brief period between sunset and complete darkness. Dawn and Twilight which are the result of rotation caused by the earth receive diffused or reflected light from the sun while it is still below the horizon.
Revolution Of The Earth
Definition And Its Effect On The Earth: Revolution of the Earth is defined as the movement of the Earth around the sun on its orbit.
- The revolving earth is tilted or inclined at an angle of 66½° to the plane of ecliptic during its revolution.
- It takes the earth 365 ¼ days to complete one revolution (i.e moves around the sun).
- The revelation of the Earth causes four seasons in a year.
- The ¼day or 6 hours is added up every four years to make an extra day in a leap year. A leap year has 366 days while a normal year has 365 days.
Effect Of Revolution Of The Earth
1. It determines a year: The time taken by the earth to move around the sun (i.e, complete it orbit) is fixed at 365¼ Days which makes up a year.
2. Varying the length of day and night at different times of the year: The length of the day and night varies depending on the position of the earth in relation to the sun. In the Northern hemisphere, during the winter around December 22, as we go northwards, the hours of darkness increase. At the Arctic circle (66½°N), the sun never rises and there is darkness for the whole day (December, 22). But in the Northern hemisphere, the period of the day light increases toward the South Pole on December, 22 and the region experiences summer.
In the Northern hemisphere, during summer around June 21, the periods or hours of daylight increase as we go toward the North Pole. At the Arctic circle (66½°), the sun never sets by June 21, and there is a complete 24 hours period of continuous day light and this region (Arctic circle) at this time is called the Land of the midnight sun. The sun is overhead at the Tropic of cancer and no part is in darkness.
Differences Between Rotation And Revolution
| Feature | Rotation | Revolution |
|---|---|---|
| Definition | The Earth rotates on its axis. | The Earth revolves around the Sun along its orbit. |
| Duration | Completes 360° in 24 hours (one day). | Completes one revolution in 365¼ days (one year). |
| Inclination Angle | Inclined at 23½° along its axis. | Tilted at 66½° to the plane of the ecliptic. |
| Effects | Causes day and night. | Causes seasons. |
| Other Impacts | Causes a time difference of one hour between two meridians 15° apart. | Causes changes in the altitude of the midday sun. |
Revision Questions
- What is the rotation of the Earth?
- (a) Distinguish between Earth’s rotation and revolution. (b) highlight any two effects of Earth’s rotation and revolution.
- (a) Define revolution of the earth. (b) Describe how revolution of the Earth affect the length of day and night and the Northern hemisphere.