This MCQ module is based on: Earth’s Rotation and Day & Night
TOPIC 43 OF 46
Earth’s Rotation and Day & Night
🎓 Class 7
Science
CBSE
Theory
Ch 12 — Earth, Moon and the Sun
⏱ ~14 min
🌐 Language: [gtranslate]
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Myaischool Lt Science Assessment
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[myaischool_lt_science_assessment grade_level="class_7" science_domain="earth_science" difficulty="basic"]
Rashmika Watches a Shadow at Kanyakumari
During the Pongal holidays, Rashmika travelled with her grandparents to Kanyakumari, the southern tip of India where the sea meets the sky. On the first morning she planted a small wooden stick upright in the sand, right beside a coconut palm. At 7 in the morning the shadow of both the stick and the palm stretched westward, long and thin. By noon the shadow had almost vanished under the stick. By 5 in the evening, the shadow was long again, but now it pointed eastward.
"Thatha," she asked her grandfather, "did the Sun actually move from east to west in the sky, or did something else happen?" Her grandfather smiled. "That is a question astronomers struggled with for a thousand years. The truth is beautiful — the Sun stayed almost still. It is we on Earth who kept spinning."
Think first: If you stood on a merry-go-round spinning slowly, the trees around the park would appear to move past you — even though it is you who is moving. Could the Sun's daily journey across the sky be the same kind of illusion?
12.1 Does the Sun Move, or Does Earth Spin?
For most of human history, people assumed the Sun, Moon and stars marched across a still Earth. But careful observations over centuries — including those by Indian astronomer Aryabhata in the 5th century CE — revealed the opposite: the Earth itself is turning. The Sun stays more or less fixed at the centre of our solar system. The apparent journey of the Sun across the sky is caused by Earth's rotation.
Key idea: Earth rotates (spins) about its own axis. One complete rotation takes about 24 hours — this is one day.
Earth's Axis
The axis of rotation is an imaginary line running from the North Pole through the centre of the Earth to the South Pole. Earth spins around this line like a top. Looking down from above the North Pole, the spin is anticlockwise — that is, from West to East. Because Earth turns West → East, the Sun appears to move East → West.
12.2 How Day and Night Form
At any moment, sunlight falls only on half of the Earth — the half facing the Sun. That half experiences day. The other half, turned away, lies in its own shadow — that half experiences night. As Earth keeps spinning, the sunlit half keeps changing, so every place on Earth takes turns in daylight and darkness.
If Earth did not spin, one side would roast in endless daytime while the other side froze in endless night. Our 24-hour rotation keeps temperatures comfortable by giving each region a share of sunlight.
12.3 Why Shadows Shift Through the Day
As Earth rotates, the direction from which sunlight reaches a stick keeps changing. In the morning, the Sun is low in the eastern sky, so shadows stretch long toward the west. By noon, the Sun is nearly overhead (especially in tropical places like Kanyakumari on certain days), so shadows are short. In the evening, the Sun is low in the western sky and shadows stretch long toward the east.
| Time of day | Sun's apparent position | Shadow direction | Shadow length |
|---|---|---|---|
| Early morning | Low in the East | Points West | Long |
| Mid-morning | Rising in East | Points West-North | Medium |
| Noon | Highest overhead | Very short (near base) | Shortest |
| Afternoon | Descending in West | Points East-North | Medium |
| Evening | Low in West | Points East | Long |
Activity 12.1 — Track a Stick's Shadow Across the DayL3 Apply
What you need: a smooth patch of sunlit ground, a straight stick (about 30 cm), chalk or small stones, a watch.
What to do:
- Plant the stick upright in the ground at around 8 AM.
- Mark the tip of its shadow with a stone or chalk line, and note the time.
- Return every hour — at 10 AM, 12 noon, 2 PM, 4 PM — and mark the tip again.
- Measure the length of each shadow and record it.
Predict: At what time will the shadow be shortest? In which direction will the 8 AM and 4 PM shadows point?
The shadow should be shortest close to noon, when the Sun is highest in the sky. The 8 AM shadow points roughly westward (because the Sun is in the east), and the 4 PM shadow points roughly eastward (Sun now in the west). The set of marks traces a graceful curve across the ground — evidence that Earth has been steadily spinning beneath our feet the whole time.
12.4 Does Every Day Last the Same Number of Hours?
A full rotation of Earth takes about 24 hours, so one "day" (sunrise to next sunrise) is 24 hours everywhere. But the daylight portion — the time between sunrise and sunset — varies by season and by location. In Srinagar during December, daylight may last only about 10 hours, while in June it stretches to almost 14 hours. Near the Equator (like Kanyakumari), the daylight time stays close to 12 hours throughout the year. Why this happens will become clear in Part 2, when we study Earth's tilt and revolution.
Remember: Rotation = Earth's daily spin → causes day and night. Revolution = Earth's yearly trip around the Sun → causes seasons (Part 2).
Competency-Based Questions Mixed L2–L4
Scenario: Rashmika's cousin Arjun from Chennai video-calls her at 6 PM Indian time and says, "The Sun has just set here." Rashmika's aunt in London (who is 4.5 hours behind India) says, "It's still mid-afternoon here!"
Q1. Earth completes one rotation on its axis in about:
(b) 24 hours. This gives us one full day-night cycle.
Q2. In which direction does Earth rotate?
(c) West to East. That is why the Sun appears to rise in the east and set in the west.
Q3. Explain in two sentences why it is afternoon in London when the Sun has already set in Chennai.
As Earth spins from west to east, places to the east (like Chennai) face the Sun earlier, and the Sun appears to "leave" them earlier. Places to the west (like London) are still turned toward the Sun, so they are experiencing afternoon at the same instant.
Q4. True or False: If Earth stopped rotating, one side of it would have permanent daylight and the other would have permanent night.
True. Without rotation, the sunlit half would remain forever bright and scorching while the other half stayed dark and frozen.
Q5. Rashmika notices her noon shadow on 21 June is extremely short, but on 21 December the noon shadow is much longer. Suggest one reason for this difference. L4
The Sun is not equally high overhead at noon on every day of the year. Earth's axis is tilted, so on some days (like around June 21 near the Tropic of Cancer) the noon Sun is almost directly overhead, making shadows very short. On other days the Sun is lower in the sky at noon, making shadows longer.
Assertion & Reason L4 Analyse
Choose: (A) Both A and R true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
A: We see the Sun rise in the east and set in the west every day.
R: Earth rotates on its axis from west to east.
(A) — both correct and R explains A. As Earth spins westward-to-eastward, the Sun appears to travel eastward-to-westward across the sky.
A: Shadows are shortest around noon.
R: At noon the Sun is highest in the sky for that location.
(A) — when the Sun is nearly overhead, light falls steeply and a vertical stick casts only a small shadow.
A: Night happens because clouds cover the Sun every evening.
R: Clouds are thicker at night.
(D) — A is false; night happens because Earth rotates and the place turns away from the Sun. R is also false (clouds aren't thicker at night). Clouds have nothing to do with day-night cycles.
Frequently Asked Questions — Earth's Rotation and Day & Night
What does the topic 'Earth's Rotation and Day & Night' cover in Class 7 Science?
The topic 'Earth's Rotation and Day & Night' is part of NCERT Class 7 Science Chapter 12 — Earth, Moon, and the Sun. It covers the key ideas of rotation, axis, day and night, 24 hours, apparent motion, Sun, Earth spin, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Earth's Rotation and Day & Night' important for Class 7 NCERT Science?
'Earth's Rotation and Day & Night' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 12 — Earth, Moon, and the Sun — introduces rotation and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Earth's Rotation and Day & Night?
The key concepts in 'Earth's Rotation and Day & Night' for Class 7 Science are: rotation, axis, day and night, 24 hours, apparent motion, Sun, Earth spin. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 12 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Earth's Rotation and Day & Night taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Earth's Rotation and Day & Night' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 12 — Earth, Moon, and the Sun — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of rotation can Class 7 students observe at home?
Class 7 students can observe rotation at home in many simple ways linked to 'Earth's Rotation and Day & Night'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 12 — Earth, Moon, and the Sun. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Earth's Rotation and Day & Night' connect to other chapters of Class 7 Science?
'Earth's Rotation and Day & Night' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of rotation appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 12 — Earth, Moon, and the Sun — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
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