Rotation

  • Rotation and revolution are the two primary motions of the earth. The spinning of the earth on its axis is known as rotation of the earth. The earth rotates from west to east. The earth completes one rotation in 23 hours 56 minutes and 4 seconds. The rotational speed of earth at equator is 1,660 kilometre per hour. Rotational speed decreases towards the poles. The earth is slightly flattened at the poles and slightly bulging at the equator due to rotation.
  • One of the main effects of earth’s rotation is the daily occurrence of day and night.
  • When the North Pole is tilted towards the Sun:
  1. Days are longer in Northern Hemisphere and shorter in Southern Hemisphere.
  2. There is summer in the Northern Hemisphere and winter in the Southern Hemisphere.
  • When South Pole faces the Sun:
  • Days are longer in Southern Hemisphere and shorter in the Northern Hemisphere.
  • There is summer in Southern Hemisphere and winter in Northern Hemisphere.
  • As the earth rotates from west to east, the air and water are deflected to the right in the Northern Hemisphere and towards left in the Southern Hemisphere.
  • Tides are caused by the gravitational pull of moon and the Sun. Corresponding high tides are found on the opposite side of the earth due to centrifugal force set up by rotating earth.
  • As the earth rotates from west to east, the sun, the moon and the stars seem to move from east to west. Earth’s axis is inclined and makes an angle of 23°30’ with earth’s orbital plane. The North Pole and the South Pole lie at the ends of the axis.
  • The tilt of earth’s axis is also known as inclination of the earth’s axis.
  • The most important effect of tilted axis of the earth is unequal duration of day and night in different parts of the earth. When the North Pole is tilted towards the Sun, days are longer in Northern Hemisphere and shorter in Southern Hemisphere. When South Pole faces the Sun, days are longer in Southern Hemisphere and shorter in the Northern Hemisphere.

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