Chapter 12: Earth, Moon, and the Sun
Introduction
The Earth, Moon, and Sun form a gravitational system that governs day and night, seasons, tides, and eclipses. Understanding their motions helps explain natural phenomena and the calendar.
1. The Earth
- Shape: Slightly flattened sphere (oblate spheroid)
- Rotation: Spins around its axis → causes day and night
- Time for one rotation: 24 hours
- Revolution: Moves around the Sun → causes seasons
- Time for one revolution: 365.25 days
- Tilt of axis: 23.5° → uneven sunlight → seasons
2. The Moon
- Natural satellite of Earth
- Revolves around Earth → causes phases of the Moon
- Rotation period: ~27.3 days (synchronous with revolution → same side faces Earth)
- Influences tides due to gravitational pull
3. The Sun
- Star at the center of the solar system
- Provides light and heat for Earth
- Appears to rise in the east and set in the west due to Earth’s rotation
- Influences climate, weather, and seasons
4. Day and Night
- Earth rotates → Sun illuminates one half → day; opposite half → night
5. Phases of the Moon
- New Moon → Crescent → First Quarter → Gibbous → Full Moon → Gibbous → Last Quarter → Crescent → New Moon
6. Eclipses
- Solar eclipse: Moon blocks Sun → daytime darkness
- Lunar eclipse: Earth blocks Sun → Moon appears dark/red
7. Tides
- Caused by Moon’s gravitational pull on oceans
- High tide and low tide occur daily
8. Key Points to Remember
- Earth rotates for day/night and revolves for seasons
- Moon causes tides and has phases
- Sun provides light and heat essential for life
- Eclipses occur due to alignment of Sun, Moon, and Earth
Questions – Earth, Moon, and the Sun
1. Very Short Answer (1 mark)
- What causes day and night?
- How long does Earth take to rotate once?
- What causes seasons?
- How long does Earth take to revolve around the Sun?
- What is a lunar eclipse?
- What is a solar eclipse?
- Name the natural satellite of Earth.
- Why do tides occur?
- What is the tilt of Earth’s axis?
- Why do we always see the same side of the Moon?
2. Multiple Choice Questions (MCQ)
- Earth is shaped like:
a) Perfect sphere
b) Cube
c) Oblate spheroid
d) Cylinder - Moon takes how many days to complete one revolution?
a) 24 hours
b) 27.3 days
c) 365 days
d) 7 days - Solar eclipse occurs when:
a) Earth blocks Sun
b) Moon blocks Sun
c) Sun blocks Moon
d) Moon blocks Earth - Day and night are caused by:
a) Earth’s revolution
b) Moon’s revolution
c) Earth’s rotation
d) Sun’s movement - High tide occurs due to:
a) Sun’s rotation
b) Moon’s gravitational pull
c) Earth’s tilt
d) Sun’s eclipse
3. Fill in the Blanks
- Earth rotates on its __________.
- Time for one rotation of Earth is __________.
- Moon revolves around Earth in __________ days.
- Tilt of Earth’s axis is __________ degrees.
- A solar eclipse occurs when the __________ comes between the Sun and Earth.
4. True/False Type
- Day and night occur due to Earth’s revolution. (True/False)
- Moon’s gravitational pull causes tides. (True/False)
- We see different sides of the Moon at different times. (True/False)
- Solar eclipses occur during New Moon. (True/False)
- Earth’s axis is tilted at 23.5°. (True/False)
5. Short Answer Questions (2–3 marks)
- Explain why day and night occur.
- Explain why seasons occur.
- Name two types of eclipses and explain briefly.
- How do tides occur?
- Describe why the same side of the Moon always faces Earth.
6. Long Answer Questions (4–5 marks)
- Explain the rotation and revolution of Earth and their effects.
- Describe the phases of the Moon with a diagram.
- Explain solar and lunar eclipses with examples.
- Discuss the role of the Sun in day/night and seasons.
- Explain how the Moon influences tides.
7. Higher-Order Thinking (HOT) & Application
- If Earth’s axis was not tilted, how would seasons be affected?
- Why do lunar and solar eclipses not occur every month?
- How do phases of the Moon affect tidal patterns?
8. Passage-Based Questions
Read the passage and answer:
Earth rotates on its axis and revolves around the Sun. Rotation causes day and night, while revolution and tilt of the axis cause seasons. Moon revolves around Earth causing phases and tides. Eclipses occur due to alignment of Sun, Earth, and Moon.
- What causes day and night?
- How are seasons caused?
- Name the natural satellite of Earth.
- What is the reason for tides?
Answer Key – Earth, Moon, and the Sun
1. Very Short Answer
- Earth’s rotation
- 24 hours
- Earth’s revolution and axis tilt
- 365.25 days
- Earth blocks Sun → Moon appears dark
- Moon blocks Sun → part/all sunlight blocked on Earth
- Moon
- Moon’s gravitational pull on oceans
- 23.5°
- Moon’s rotation period = revolution period
2. MCQ Answers
- c) Oblate spheroid
- b) 27.3 days
- b) Moon blocks Sun
- c) Earth’s rotation
- b) Moon’s gravitational pull
3. Fill in the Blanks
- axis
- 24 hours
- 27.3
- 23.5
- Moon
4. True/False
- False
- True
- False
- True
- True
5. Short Answer
- Rotation of Earth → Sun illuminates half → day; opposite half → night
- Revolution + tilt → unequal sunlight → seasons
- Solar – Moon blocks Sun; Lunar – Earth blocks Sun
- Moon’s gravity pulls ocean water → high and low tides
- Moon’s rotation = revolution → same side faces Earth
6. Long Answer
- Rotation → day/night; Revolution → seasons; Explained with diagram
- Moon phases: New Moon → Crescent → First Quarter → Gibbous → Full Moon → Gibbous → Last Quarter → Crescent → New Moon
- Solar eclipse – Moon blocks Sun; Lunar eclipse – Earth blocks Sun
- Sun provides light, heat, drives seasons and day/night
- Moon’s gravitational pull → tidal bulges in oceans
7. HOT & Application
- No tilt → no seasons; constant climate
- Moon’s orbit and alignment not always exact → eclipses rare
- Moon phases influence tidal strength (spring tides, neap tides)
8. Passage-Based
- Earth’s rotation
- Revolution + tilt
- Moon
- Moon’s gravitational pull