Chapter 12: Earth, Moon,and the Sun
7th StandardScience
Chapter Summary
Earth, Moon,and the Sun - Chapter Summary
# Earth, Moon, and the Sun
## Overview
This chapter explores how the Earth's rotation and revolution affect our observations of the Sun, Moon, and stars, and how these celestial movements lead to phenomena such as day and night, seasons, and eclipses. Through hands-on activities, students examine how the Earth's movements give rise to changes in the sky, different seasons, and solar and lunar eclipses.
## Key Topics Covered
### 1. Rotation of the Earth
- The Earth rotates (spins) around an imaginary line called its **axis**.
- This axis passes through the **North Pole** and **South Pole**.
- The rotation is from **West to East** and completes one full turn in **24 hours**.
- The apparent movement of the **Sun rising in the East** and **setting in the West** is due to Earth's rotation.
- Half of the Earth receives sunlight at a time (day), while the other half is in darkness (night).
#### Activities and Observations:
- **Merry-go-round analogy**: Helps understand how the surroundings appear to move due to the observer's own rotation.
- **Globe and Torch Experiment**: Demonstrates how rotation causes day and night and how sunrise occurs in the east first.
- **Observation from the Equator**: Sun appears overhead at noon, then sets in the west—matching our daily experiences.
### 2. Apparent Motion of Celestial Objects
- Stars and the Moon also appear to rise in the East and set in the West.
- **Pole Star (Dhruva Tara)** appears stationary because Earth’s axis points toward it.
- **Big Dipper (Saptarishi)**: Appears to move during the night due to Earth's rotation.
- **Star Trails**: Long exposure photographs show stars moving in circular arcs.
### 3. Revolution of the Earth
- The Earth **revolves around the Sun** in a nearly circular **orbit**.
- One complete revolution takes approximately **365 days and 6 hours**.
- As Earth revolves, the **night sky changes** — different stars and constellations become visible in different months.
### 4. Seasons on Earth
- Earth’s axis is **tilted**, not straight up.
- The tilt and spherical shape of Earth cause **variation in sunlight intensity and duration** in different hemispheres, leading to seasons.
#### Effects of Tilt:
- In **June**, Northern Hemisphere is tilted toward the Sun — results in **summer** with longer days.
- In **December**, the Southern Hemisphere is tilted toward the Sun — results in **summer there** and **winter in the North**.
- **Equinoxes** (21 March & 23 September): Equal day and night.
- **Solstices** (21 June & 22 December): Longest and shortest days.
#### Myths Debunked:
- Seasons are **not** caused by Earth being closer or farther from the Sun.
- Earth is actually **closest to the Sun in January**.
Here is **Part 2** of the markdown summary for the chapter **"Earth, Moon, and the Sun"**, continuing from Part 1.
### 5. Eclipses
#### 5.1 Solar Eclipse
- Occurs when the **Moon comes between the Earth and the Sun**, casting a shadow on Earth.
- Despite being smaller, the Moon can block the Sun due to its proximity, making their **apparent sizes** similar.
- **Total Solar Eclipse**: Entire Sun is blocked; area appears dark during daytime.
- **Partial Solar Eclipse**: Only part of the Sun is covered.
- Safe viewing must be done using protective methods; **never view directly**.
#### 5.2 Lunar Eclipse
- Happens when the **Earth comes between the Sun and the Moon**, casting a shadow on the Moon.
- **Total Lunar Eclipse**: Entire Moon in Earth's shadow; appears dark red.
- **Partial Lunar Eclipse**: Only part of Moon darkened.
- Safe to view with **naked eyes**.
## New Terms and Definitions (in Simple English)
| Term | Definition |
|----------------------|----------------------------------------------------------------------------|
| Rotation | Spinning of an object around an imaginary line (axis) |
| Axis of rotation | Imaginary line through the center of an object that it spins around |
| Revolution | Movement of one object around another |
| Orbit | Path that an object follows while revolving around another object |
| Hemisphere | Half of the Earth (Northern or Southern) |
| Solstice | Day with the longest or shortest daylight |
| Equinox | Day with equal length of day and night |
| Eclipse | Blocking of light from one object by another |
| Solar eclipse | When Moon blocks the Sun’s light from reaching the Earth |
| Lunar eclipse | When Earth blocks sunlight from reaching the Moon |
| Apparent size | How big something looks from where you see it |
| Pole Star | A star that appears fixed in the sky, aligned with Earth’s axis |
| Constellation | Group of stars that form a recognizable pattern |
## Practice Questions
### Easy (3)
1. **What causes day and night on Earth?**
**Answer**: The Earth's rotation causes day and night.
**Explanation**: As the Earth rotates, different parts face the Sun (day) and move away (night).
2. **In which direction does the Sun appear to rise?**
**Answer**: In the East.
**Explanation**: The Earth rotates from West to East, so the Sun appears in the East first.
3. **How long does the Earth take to complete one rotation?**
**Answer**: 24 hours.
**Explanation**: One full spin on its axis takes one day.
### Medium (2)
4. **Why do different constellations appear in the night sky during the year?**
**Answer**: Because the Earth revolves around the Sun.
**Explanation**: Our view of the stars changes as we look in different directions throughout the year.
5. **Why is it summer in India when it is winter in Australia?**
**Answer**: Because of the tilt of the Earth's axis.
**Explanation**: When the Northern Hemisphere is tilted toward the Sun, it’s summer there, and winter in the South.
### Difficult (3)
6. **What is the role of Earth's tilt in causing seasons?**
**Answer**: The tilt causes different hemispheres to receive varying sunlight.
**Explanation**: This variation changes the intensity and duration of sunlight across the year.
7. **Why can the Moon cause a total solar eclipse but not planets like Venus or Mercury?**
**Answer**: Because the Moon appears the same size as the Sun from Earth.
**Explanation**: Though smaller, the Moon is closer, making its apparent size large enough to block the Sun.
8. **What is the difference between rotation and revolution?**
**Answer**: Rotation is spinning on one’s own axis; revolution is orbiting around another object.
**Explanation**: Earth rotates on its axis and revolves around the Sun.
### Very Difficult (2)
9. **If Earth’s axis were not tilted, what would happen to the seasons?**
**Answer**: There would be no seasons.
**Explanation**: The same amount of sunlight would fall everywhere throughout the year.
10. **Why is a total lunar eclipse visible from a large area while a solar eclipse is not?**
**Answer**: Because Earth’s shadow is larger than the Moon’s shadow.
**Explanation**: The Moon’s shadow covers a small area; Earth’s shadow covers a wider area of the Moon.
---
## Overview
This chapter explores how the Earth's rotation and revolution affect our observations of the Sun, Moon, and stars, and how these celestial movements lead to phenomena such as day and night, seasons, and eclipses. Through hands-on activities, students examine how the Earth's movements give rise to changes in the sky, different seasons, and solar and lunar eclipses.
## Key Topics Covered
### 1. Rotation of the Earth
- The Earth rotates (spins) around an imaginary line called its **axis**.
- This axis passes through the **North Pole** and **South Pole**.
- The rotation is from **West to East** and completes one full turn in **24 hours**.
- The apparent movement of the **Sun rising in the East** and **setting in the West** is due to Earth's rotation.
- Half of the Earth receives sunlight at a time (day), while the other half is in darkness (night).
#### Activities and Observations:
- **Merry-go-round analogy**: Helps understand how the surroundings appear to move due to the observer's own rotation.
- **Globe and Torch Experiment**: Demonstrates how rotation causes day and night and how sunrise occurs in the east first.
- **Observation from the Equator**: Sun appears overhead at noon, then sets in the west—matching our daily experiences.
### 2. Apparent Motion of Celestial Objects
- Stars and the Moon also appear to rise in the East and set in the West.
- **Pole Star (Dhruva Tara)** appears stationary because Earth’s axis points toward it.
- **Big Dipper (Saptarishi)**: Appears to move during the night due to Earth's rotation.
- **Star Trails**: Long exposure photographs show stars moving in circular arcs.
### 3. Revolution of the Earth
- The Earth **revolves around the Sun** in a nearly circular **orbit**.
- One complete revolution takes approximately **365 days and 6 hours**.
- As Earth revolves, the **night sky changes** — different stars and constellations become visible in different months.
### 4. Seasons on Earth
- Earth’s axis is **tilted**, not straight up.
- The tilt and spherical shape of Earth cause **variation in sunlight intensity and duration** in different hemispheres, leading to seasons.
#### Effects of Tilt:
- In **June**, Northern Hemisphere is tilted toward the Sun — results in **summer** with longer days.
- In **December**, the Southern Hemisphere is tilted toward the Sun — results in **summer there** and **winter in the North**.
- **Equinoxes** (21 March & 23 September): Equal day and night.
- **Solstices** (21 June & 22 December): Longest and shortest days.
#### Myths Debunked:
- Seasons are **not** caused by Earth being closer or farther from the Sun.
- Earth is actually **closest to the Sun in January**.
Here is **Part 2** of the markdown summary for the chapter **"Earth, Moon, and the Sun"**, continuing from Part 1.
### 5. Eclipses
#### 5.1 Solar Eclipse
- Occurs when the **Moon comes between the Earth and the Sun**, casting a shadow on Earth.
- Despite being smaller, the Moon can block the Sun due to its proximity, making their **apparent sizes** similar.
- **Total Solar Eclipse**: Entire Sun is blocked; area appears dark during daytime.
- **Partial Solar Eclipse**: Only part of the Sun is covered.
- Safe viewing must be done using protective methods; **never view directly**.
#### 5.2 Lunar Eclipse
- Happens when the **Earth comes between the Sun and the Moon**, casting a shadow on the Moon.
- **Total Lunar Eclipse**: Entire Moon in Earth's shadow; appears dark red.
- **Partial Lunar Eclipse**: Only part of Moon darkened.
- Safe to view with **naked eyes**.
## New Terms and Definitions (in Simple English)
| Term | Definition |
|----------------------|----------------------------------------------------------------------------|
| Rotation | Spinning of an object around an imaginary line (axis) |
| Axis of rotation | Imaginary line through the center of an object that it spins around |
| Revolution | Movement of one object around another |
| Orbit | Path that an object follows while revolving around another object |
| Hemisphere | Half of the Earth (Northern or Southern) |
| Solstice | Day with the longest or shortest daylight |
| Equinox | Day with equal length of day and night |
| Eclipse | Blocking of light from one object by another |
| Solar eclipse | When Moon blocks the Sun’s light from reaching the Earth |
| Lunar eclipse | When Earth blocks sunlight from reaching the Moon |
| Apparent size | How big something looks from where you see it |
| Pole Star | A star that appears fixed in the sky, aligned with Earth’s axis |
| Constellation | Group of stars that form a recognizable pattern |
## Practice Questions
### Easy (3)
1. **What causes day and night on Earth?**
**Answer**: The Earth's rotation causes day and night.
**Explanation**: As the Earth rotates, different parts face the Sun (day) and move away (night).
2. **In which direction does the Sun appear to rise?**
**Answer**: In the East.
**Explanation**: The Earth rotates from West to East, so the Sun appears in the East first.
3. **How long does the Earth take to complete one rotation?**
**Answer**: 24 hours.
**Explanation**: One full spin on its axis takes one day.
### Medium (2)
4. **Why do different constellations appear in the night sky during the year?**
**Answer**: Because the Earth revolves around the Sun.
**Explanation**: Our view of the stars changes as we look in different directions throughout the year.
5. **Why is it summer in India when it is winter in Australia?**
**Answer**: Because of the tilt of the Earth's axis.
**Explanation**: When the Northern Hemisphere is tilted toward the Sun, it’s summer there, and winter in the South.
### Difficult (3)
6. **What is the role of Earth's tilt in causing seasons?**
**Answer**: The tilt causes different hemispheres to receive varying sunlight.
**Explanation**: This variation changes the intensity and duration of sunlight across the year.
7. **Why can the Moon cause a total solar eclipse but not planets like Venus or Mercury?**
**Answer**: Because the Moon appears the same size as the Sun from Earth.
**Explanation**: Though smaller, the Moon is closer, making its apparent size large enough to block the Sun.
8. **What is the difference between rotation and revolution?**
**Answer**: Rotation is spinning on one’s own axis; revolution is orbiting around another object.
**Explanation**: Earth rotates on its axis and revolves around the Sun.
### Very Difficult (2)
9. **If Earth’s axis were not tilted, what would happen to the seasons?**
**Answer**: There would be no seasons.
**Explanation**: The same amount of sunlight would fall everywhere throughout the year.
10. **Why is a total lunar eclipse visible from a large area while a solar eclipse is not?**
**Answer**: Because Earth’s shadow is larger than the Moon’s shadow.
**Explanation**: The Moon’s shadow covers a small area; Earth’s shadow covers a wider area of the Moon.
---
Earth, Moon, and the Sun
Overview
This chapter explores how the Earth's rotation and revolution affect our observations of the Sun, Moon, and stars, and how these celestial movements lead to phenomena such as day and night, seasons, and eclipses. Through hands-on activities, students examine how the Earth's movements give rise to changes in the sky, different seasons, and solar and lunar eclipses.
Key Topics Covered
1. Rotation of the Earth
- The Earth rotates (spins) around an imaginary line called its axis.
- This axis passes through the North Pole and South Pole.
- The rotation is from West to East and completes one full turn in 24 hours.
- The apparent movement of the Sun rising in the East and setting in the West is due to Earth's rotation.
- Half of the Earth receives sunlight at a time (day), while the other half is in darkness (night).
Activities and Observations:
- Merry-go-round analogy: Helps understand how the surroundings appear to move due to the observer's own rotation.
- Globe and Torch Experiment: Demonstrates how rotation causes day and night and how sunrise occurs in the east first.
- Observation from the Equator: Sun appears overhead at noon, then sets in the west—matching our daily experiences.
2. Apparent Motion of Celestial Objects
- Stars and the Moon also appear to rise in the East and set in the West.
- Pole Star (Dhruva Tara) appears stationary because Earth’s axis points toward it.
- Big Dipper (Saptarishi): Appears to move during the night due to Earth's rotation.
- Star Trails: Long exposure photographs show stars moving in circular arcs.
3. Revolution of the Earth
- The Earth revolves around the Sun in a nearly circular orbit.
- One complete revolution takes approximately 365 days and 6 hours.
- As Earth revolves, the night sky changes — different stars and constellations become visible in different months.
4. Seasons on Earth
- Earth’s axis is tilted, not straight up.
- The tilt and spherical shape of Earth cause variation in sunlight intensity and duration in different hemispheres, leading to seasons.
Effects of Tilt:
- In June, Northern Hemisphere is tilted toward the Sun — results in summer with longer days.
- In December, the Southern Hemisphere is tilted toward the Sun — results in summer there and winter in the North.
- Equinoxes (21 March & 23 September): Equal day and night.
- Solstices (21 June & 22 December): Longest and shortest days.
Myths Debunked:
- Seasons are not caused by Earth being closer or farther from the Sun.
- Earth is actually closest to the Sun in January.
Here is Part 2 of the markdown summary for the chapter "Earth, Moon, and the Sun", continuing from Part 1.
5. Eclipses
5.1 Solar Eclipse
- Occurs when the Moon comes between the Earth and the Sun, casting a shadow on Earth.
- Despite being smaller, the Moon can block the Sun due to its proximity, making their apparent sizes similar.
- Total Solar Eclipse: Entire Sun is blocked; area appears dark during daytime.
- Partial Solar Eclipse: Only part of the Sun is covered.
- Safe viewing must be done using protective methods; never view directly.
5.2 Lunar Eclipse
- Happens when the Earth comes between the Sun and the Moon, casting a shadow on the Moon.
- Total Lunar Eclipse: Entire Moon in Earth's shadow; appears dark red.
- Partial Lunar Eclipse: Only part of Moon darkened.
- Safe to view with naked eyes.
New Terms and Definitions (in Simple English)
| Term | Definition |
|---|---|
| Rotation | Spinning of an object around an imaginary line (axis) |
| Axis of rotation | Imaginary line through the center of an object that it spins around |
| Revolution | Movement of one object around another |
| Orbit | Path that an object follows while revolving around another object |
| Hemisphere | Half of the Earth (Northern or Southern) |
| Solstice | Day with the longest or shortest daylight |
| Equinox | Day with equal length of day and night |
| Eclipse | Blocking of light from one object by another |
| Solar eclipse | When Moon blocks the Sun’s light from reaching the Earth |
| Lunar eclipse | When Earth blocks sunlight from reaching the Moon |
| Apparent size | How big something looks from where you see it |
| Pole Star | A star that appears fixed in the sky, aligned with Earth’s axis |
| Constellation | Group of stars that form a recognizable pattern |
Practice Questions
Easy (3)
-
What causes day and night on Earth?
Answer: The Earth's rotation causes day and night.
Explanation: As the Earth rotates, different parts face the Sun (day) and move away (night). -
In which direction does the Sun appear to rise?
Answer: In the East.
Explanation: The Earth rotates from West to East, so the Sun appears in the East first. -
How long does the Earth take to complete one rotation?
Answer: 24 hours.
Explanation: One full spin on its axis takes one day.
Medium (2)
-
Why do different constellations appear in the night sky during the year?
Answer: Because the Earth revolves around the Sun.
Explanation: Our view of the stars changes as we look in different directions throughout the year. -
Why is it summer in India when it is winter in Australia?
Answer: Because of the tilt of the Earth's axis.
Explanation: When the Northern Hemisphere is tilted toward the Sun, it’s summer there, and winter in the South.
Difficult (3)
-
What is the role of Earth's tilt in causing seasons?
Answer: The tilt causes different hemispheres to receive varying sunlight.
Explanation: This variation changes the intensity and duration of sunlight across the year. -
Why can the Moon cause a total solar eclipse but not planets like Venus or Mercury?
Answer: Because the Moon appears the same size as the Sun from Earth.
Explanation: Though smaller, the Moon is closer, making its apparent size large enough to block the Sun. -
What is the difference between rotation and revolution?
Answer: Rotation is spinning on one’s own axis; revolution is orbiting around another object.
Explanation: Earth rotates on its axis and revolves around the Sun.
Very Difficult (2)
-
If Earth’s axis were not tilted, what would happen to the seasons?
Answer: There would be no seasons.
Explanation: The same amount of sunlight would fall everywhere throughout the year. -
Why is a total lunar eclipse visible from a large area while a solar eclipse is not?
Answer: Because Earth’s shadow is larger than the Moon’s shadow.
Explanation: The Moon’s shadow covers a small area; Earth’s shadow covers a wider area of the Moon.