Theory:

Motions of the Earth
  • Shape: Spherical
Inclination of Earth’s axis
  • Earth rotates on its axis.
  • Axis is an imaginary line that runs from the North Pole to the South Pole.
  • Axis passes through the centre of the Earth.
  • Tilted or inclined from the vertical by an angle of 23½°.
  • Makes an angle of 66½° with the plane of the Earth’s orbit.
shutterstock_1722564016.jpg
Velocity of the Earth’s rotation
  • 1670 km per hour at the equator
  • 845 km per hour at 60° N and S latitudes and
  • Zero at the poles
Rotation
  • It is the spinning movement of the Earth on its axis.
  • The Earth rotates from west to east (anti-clockwise).
  • It takes 23 hours 56 minutes and 4.09 seconds to complete one rotation.
  • The line which divides the surface of the Earth into a lighted half and a dark half is called the Terminator Line.
shutterstock_1825910078.jpg
Revolution
  • It is the movement of the Earth around the Sun on its elliptical path.
  • The Earth takes 365 ¼ days for it to complete one revolution.
  • Revolution speed: 30 km per second.
  • Inclination of the Earth on its axis and its revolution around the Sun cause different seasons
  • The Northern Hemisphere is inclined towards the Sun: 21st March to 23rd September (6 months).
  • The Southern Hemisphere is inclined towards the Sun: From Sep 23rd to March 21st (6 months).
shutterstock_1712195425.jpg
 
Equinoxes
  • Equator faces the Sun directly on 21 March and 23 September.
  • The day and night are equal throughout the Earth.
Summer Solstice
  • On 21st June, the Tropic of Cancer faces the Sun.
  • Longest day in Northern Hemisphere and longest night in Southern Hemisphere.
Winter Solstice
  • On 22nd December, the Tropic of Capricorn faces the Sun.
  • Longest day in Southern Hemisphere and longest night in Northern Hemisphere.
 Summer SolsticeWinter Solstice
Date
21st June
22nd December
Longest day (Hemisphere)
North
South
Longest night (Hemisphere)
South
North
 
shutterstock_1696757482.jpg
 
Aphelion & Perihelion
  • Perihelion is the Earth’s closest position to the Sun.
  • Aphelion is the farthest position of the Earth from the Sun.
shutterstock_1716699340.jpg