Earth, Moon, and

Earth, Moon, and the Sun

This introductory section sets the stage for understanding the apparent motion of the Sun in the sky and the Earth's movement. It begins with a real-life observation by a student, Rashmika, who notices that the shadows of coconut trees are longer in the morning and shorter in the afternoon. She hypothesizes that this change is due to the movement of the Sun across the sky during the day. However, she recalls from previous learning that the Earth moves around the Sun, which puzzles her about whether the Sun actually moves or if it is the Earth that moves. This section introduces the fundamental question of apparent solar motion versus Earth's actual motion, which is the basis for the chapter. It encourages students to think critically about everyday observations and to question their assumptions. The section also includes images of the Sun and shadows to visually support the concept of changing shadow lengths and the Sun's apparent path.

• Shadows of objects change length during the day due to the Sun's apparent movement.
• The Sun appears to move from East to West across the sky.
• Earth moves around the Sun, which raises questions about the Sun's apparent motion.
• Observation and questioning are key to understanding celestial motions.
• The chapter will explore Earth's rotation and revolution to explain these phenomena.
• 📌 Shadow: The dark area formed when an object blocks light.
• 📌 Apparent motion: The perceived movement of an object as seen from a particular viewpoint.

12.1 Rotation of the Earth

This section explains the concept of Earth's rotation and how it causes the apparent movement of the Sun from East to West, leading to day and night. It begins by relating the observation that the Sun rises in the East and sets in the West to the Earth's rotation. To help visualize this, the section introduces the analogy of a merry-go-round. When a person sits on a merry-go-round turning anti-clockwise, objects outside appear to move clockwise. This helps students understand that the apparent motion of the Sun is due to the Earth's rotation on its own axis, not the Sun moving around the Earth. The Earth rotates about an imaginary line called its axis, which passes through the geographic North and South Poles. The Earth completes one rotation approximately every 24 hours. When viewed from above the North Pole, the Earth rotates anti-clockwise, i.e., from West to East. Using a globe, students can simulate this rotation and observe how locations move around the axis. The section also explains that half of the Earth faces the Sun and experiences daytime, while the other half is in darkness, experiencing night. The rotation from West to East causes the Sun to appear to rise in the East and set in the West. This section includes several activities using a globe and torchlight to demonstrate day and night and the direction of Earth's rotation. Activity 12.2: Using a globe and torchlight to understand Earth's rotation and day-night cycle.

• Earth rotates on its own axis passing through the North and South Poles.
• One complete rotation takes about 24 hours.
• Rotation is anti-clockwise when viewed from the North Pole (West to East).
• Earth's rotation causes day and night.
• Half of the Earth is illuminated by the Sun at any time, causing daytime; the other half is in darkness, causing night.
• The Sun appears to rise in the East and set in the West due to Earth's rotation.
• 📌 Rotation: The spinning of an object around its own axis.
• 📌 Axis of rotation: An imaginary line through an object around which it rotates.
• 📌 Day and night: Caused by Earth's rotation, with the side facing the Sun experiencing day and the opposite side experiencing night.