Earth's Rotation and Revolution

All eight planets, including Earth, have two main types of movements:

1. Rotation: Earth spins on its axis, completing a full turn in about $24 ext{ hours}$.

   • Causes day and night.

   • At the equator, the speed is about $1600 ext{ km/h}$.

2. Revolution: Earth orbits around the sun, taking about $365 ext{ days and } 6 ext{ hours}$ for one complete trip.

   • This movement is responsible for changing seasons.

Key Concepts

• Axial Tilt: Earth's axis is tilted at 23.5°, which influences the seasons.

  • This tilt affects daylight duration for each hemisphere throughout the year.

Effects of Earth's Rotation

1. Day & Night: Areas of Earth facing the sun experience daylight, while those facing away are in darkness.

2. Coriolis Effect: Influences wind and ocean current directions.

3. Circle of Illumination: Dividing line that shows daylight versus darkness on Earth.

Effects of Earth's Revolution

• Perihelion: Closest point to the sun (about $147 ext{ million km}$), occurs around January 3rd.

• Aphelion: Farthest point from the sun (about $152 ext{ million km}$), occurs around July 4th.

Important Dates

• Equinoxes:

  • March 21 (Spring in Northern Hemisphere) and September 22/23 (Autumn in Northern Hemisphere).

• Solstices:

  • June 21 (Summer in Northern Hemisphere) and December 21/22 (Winter in Northern Hemisphere).

Definitions

• Rotation: Spinning of Earth on its axis.

• Revolution: The orbiting of Earth around the sun.

• Solstice: Longest or shortest day of the year.

• Equinox: Equal day and night lengths.

• Orbit: The path Earth takes around the sun.

Summary of Seasonal Variations

• June 21: Longest day in Northern Hemisphere.

• December 21: Shortest day in Northern Hemisphere.

• March 21 and September 23: Equal day