Class 6 Social Science: Motions of the Earth

Introduction
- Two types of motions
  - Rotation
  - Revolution
- Axis
  - Imaginary line
  - Makes an angle of 66½° with orbital plane
- Orbital Plane
  - Plane formed by the orbit
Rotation
- Definition
  - Movement of the earth on its axis
- Key Facts
  - Direction: West to East (counter-clockwise)
  - Time taken: 24 hours (one earthday)
- Effects
  - Day and night formation
  - Circle of Illumination
    - Division line between day and night
Revolution
- Definition
  - Movement of the earth around the sun in a fixed path (orbit)
- Key Facts
  - Time taken: 365¼ days (one year)
  - Leap Year
    - Every 4th year has 366 days (extra day in February)
- Causes of Seasons
  - Fixed inclination of the earth's axis
  - Revolution around the sun
Solstice and Equinox (Seasonal Changes)
- Summer Solstice (June 21)
  - Northern Hemisphere tilted towards the sun
  - Longest day and shortest night in the North
  - Tropics of Cancer receives direct rays
- Winter Solstice (December 22)
  - Southern Hemisphere tilted towards the sun
  - Longest day and shortest night in the South
  - Tropics of Capricorn receives direct rays
- Equinox (March 21 and September 23)
  - Direct rays on the Equator
  - Whole earth experiences equal days and equal nights

Motions of the Earth Mind Map