Earth's Motion

Earth's Rotation

• Earth's rotation is responsible for the apparent movement of the Sun across the sky and the occurrence of day and night.
• The Earth's axis is an invisible line that runs through the planet's center from the North Pole to the South Pole.
• The Earth is tilted at an angle of 23.5°, resulting in different parts of the planet receiving varying amounts of sunlight at any given time.
• This tilt is also responsible for the four seasons we experience on Earth.

Day and Night Cycle

• As the Earth rotates on its axis, one side of the Earth (or hemisphere) faces towards the Sun while the other side faces away.
• The Earth makes one rotation on its axis every 24 hours, or one day.
• As the Earth spins on its axis, the side facing the Sun moves from sunlight into darkness, appearing as a sunset from our view on Earth.
• Meanwhile, the dark half of Earth moves into the sunlight, experiencing sunrise.

Apparent Motion of the Sun

• The Sun appears to move from east to west across the sky due to the Earth's rotation from west to east.
• Shadows support this claim, as they change throughout the day.
• As the Sun appears to rise in the east in the morning, its light makes long shadows that point towards the west.
• By noon, the shadows become shorter, and as the day continues, the Sun appears to move towards the west, causing the shadows to lengthen again and point towards the east.

Historical Significance

• Before the invention of clocks, people used the Sun's apparent motion to tell time.
• The Sun's apparent motion can be used to create a sundial, allowing people to estimate time.