The Earth
- The Earth is the third planet from the Sun and the only known planet to support life.
- It has a diameter of 12,742 km and an atmosphere composed mainly of nitrogen (78%) and oxygen (21%).
- The Earth has one natural satellite – the Moon.
Unique Features of Earth
✅ Presence of Liquid Water – 71% of Earth’s surface is covered with water.
✅ Atmosphere – Protects from harmful solar radiation and maintains temperature.
✅ Magnetic Field – Protects Earth from solar winds.
✅ Plate Tectonics – Helps in landform changes and supports geological activity.
The Moon
- The Moon is the Earth’s only natural satellite and the fifth-largest moon in the solar system.
- Diameter: 3,474 km (1/4th of Earth’s size).
- Distance from Earth: ~384,400 km.
- The Moon has no atmosphere, water, or weather, making its surface dry and barren.
- Gravity on the Moon is 1/6th of Earth’s gravity.
Movements of the Moon
- Revolution Around Earth
- The Moon revolves around the Earth in 27.3 days (sidereal month).
- Its orbit is elliptical.
- Rotation on Its Axis
- The Moon rotates on its axis in 27.3 days (same as its revolution).
- This is why only one side of the Moon is visible from Earth (synchronous rotation).
Phases of the Moon
The Moon’s phases are caused by the changing positions of the Sun, Earth, and Moon.
- New Moon – The Moon is between Earth and the Sun, and its dark side faces Earth.
- Waxing Crescent – A small portion of the Moon is visible.
- First Quarter – Half of the Moon is visible.
- Waxing Gibbous – More than half is visible.
- Full Moon – The entire Moon is visible.
- Waning Gibbous – The Moon starts decreasing in size.
- Last Quarter – Half of the Moon is visible again.
- Waning Crescent – Only a small portion is visible before becoming a New Moon again.
Eclipses
1. Solar Eclipse
- Occurs when the Moon comes between the Sun and Earth, blocking sunlight.
- Can be Total, Partial, or Annular.
2. Lunar Eclipse
- Occurs when the Earth comes between the Sun and Moon, casting a shadow on the Moon.
- Can be Total or Partial.
Tides and the Moon
- The gravitational pull of the Moon causes high and low tides on Earth.
- Spring Tides – Occur during New Moon and Full Moon (higher tides).
- Neap Tides – Occur during First and Last Quarter (lower tides).
MCQs on Earth and the Moon
1. What is the diameter of the Earth?
a) 6,371 km
b) 12,742 km
c) 3,474 km
d) 10,000 km
Answer: b) 12,742 km
2. How long does the Moon take to orbit the Earth?
a) 24 hours
b) 365 days
c) 27.3 days
d) 30 days
Answer: c) 27.3 days
3. Why do we always see the same side of the Moon?
a) The Moon does not rotate
b) The Moon rotates at the same rate as it revolves around Earth
c) Earth’s gravity pulls it
d) The Moon changes its speed
Answer: b) The Moon rotates at the same rate as it revolves around Earth
4. What causes tides on Earth?
a) Earth’s rotation
b) Wind and ocean currents
c) Gravitational pull of the Moon and Sun
d) Earth’s magnetic field
Answer: c) Gravitational pull of the Moon and Sun
5. What is the phase of the Moon when it is completely illuminated?
a) New Moon
b) First Quarter
c) Full Moon
d) Last Quarter
Answer: c) Full Moon
6. What type of eclipse occurs when the Earth comes between the Sun and the Moon?
a) Solar Eclipse
b) Lunar Eclipse
c) Annular Eclipse
d) Penumbral Eclipse
Answer: b) Lunar Eclipse
7. What is the surface of the Moon covered with?
a) Water and sand
b) Thick clouds
c) Dust and rocky material
d) Vegetation
Answer: c) Dust and rocky material
8. How much weaker is the Moon’s gravity compared to Earth’s?
a) 1/2
b) 1/3
c) 1/6
d) 1/10
Answer: c) 1/6
Short Answer Questions
1. Why does the Moon have no atmosphere?
The Moon has low gravity, which is not strong enough to hold an atmosphere.
2. How do tides occur?
Tides occur due to the gravitational pull of the Moon and the Sun on Earth’s oceans.
3. What are the different phases of the Moon?
The phases of the Moon are New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent.
4. What is a solar eclipse?
A solar eclipse occurs when the Moon comes between the Sun and Earth, blocking sunlight.
5. What is the importance of the Moon for Earth?
- It stabilizes Earth’s tilt, helping in a stable climate.
- It causes tides, which affect marine life and ecosystems.
Conclusion
The Earth and the Moon have a close relationship, affecting tides, eclipses, and Earth’s stability. The Moon’s gravitational influence plays a crucial role in Earth’s natural phenomena.
Would you like additional diagrams or explanations? 😊