The Shape of Earth

The Shape of the Earth

• Earth is one of eight planets in our solar system and has a slightly greater radius at the Equator.
• The Earth's shape is an oblate spheroid, meaning it is not perfectly round, but slightly flattened at the poles and bulging in the middle.
• This shape is due to the gravitational force caused by the Earth's rotation.

Evidences of the Earth's Shape

• Places in the east see the rising Sun earlier, indicating that the Earth is not flat.
• When a ship approaches land, its funnel or mast is seen first, and then the hull, providing evidence that the Earth is not flat.

Movements of the Earth

Rotation

• Rotation is the movement of the Earth on its axis, taking about 24 hours to complete one rotation.
• The Earth rotates from west to east, causing the sun to appear to rise in the east and set in the west.
• The axis of rotation is tilted at an angle of 23.5° and is perpendicular to the Earth's orbit, influencing daylight, temperature, and weather patterns from season to season.

Effects of Earth's Rotation

• Rotation creates a diurnal cycle of light and darkness, temperature, and humidity changes.
• As the Earth rotates, half of the Earth faces the sun and half faces away from the sun, causing day and night.

High and Low Tide

• High and low tide is a result of the gravitational pull between the Sun and the Moon.
• As the Earth rotates, the Sun and the Moon pull on the Earth, causing high and low tide.

Revolution of the Earth

• Revolution is the movement of the Earth around the Sun in a fixed path or orbit.
• The time for one revolution is 365¼ days or one year, and the speed of Earth's revolution is 68,000 miles per hour.

Effects of Revolution of the Earth

• The revolution of the Earth gives the impression that the Sun is moving north and south of the equator.
• The equator faces the Sun directly on March 21 and September 23, resulting in equal day and night throughout the Earth, known as equinoxes.
• The revolution causes variation in the length of day and night.

Seasons

• The revolution of the Earth causes the four seasons:
  • Summer (Kiremt)
  • Autumn (Meher)
  • Winter (Bega)
  • Spring (Belg / Tsedey)
• The seasons result from the tilt of the Earth's axis and the revolution around the Sun.