Class 8 Science Chapter 11 Keeping Time with the Skies Solutions | Curiosity NCERT Answers

 

🌟 Class 8 Science – Curiosity Chapter 11

🌙 Keeping Time with the Skies

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🟢 1. State whether the following statements are True or False.

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(i) We can only see that part of the Moon which reflects sunlight towards us.

✅ Answer:

True

🧠 Explanation:

The Moon does not produce its own light. It reflects sunlight. We can only see the part of the Moon that is illuminated by the Sun and facing the Earth.

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(ii) The shadow of Earth blocks sunlight from reaching the Moon causing phases.

❌ Answer:

False

✔️ Correct Statement:

The phases of the Moon are caused by the changing positions of the Moon as it revolves around the Earth.

🧠 Explanation:

Earth’s shadow falling on the Moon causes a lunar eclipse, not the phases of the Moon.

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(iii) Calendars are based on various astronomical cycles which repeat in a predictable manner.

✅ Answer:

True

🧠 Explanation:

Calendars are based on repeating cycles such as:

• Earth’s rotation → Day
• Moon’s revolution → Month
• Earth’s revolution → Year

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(iv) The Moon can only be seen at night.

❌ Answer:

False

✔️ Correct Statement:

The Moon can also be seen during the daytime.

🧠 Explanation:

Its visibility depends on its phase and position relative to the Sun.

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🟢 2. Amol was born on 6th of May on a full Moon day. Does his birthday fall on the full Moon day every year? Explain your answer.

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❌ Answer:

No, it will not fall on a full Moon day every year.

🧠 Explanation:

• The Gregorian calendar is based on Earth’s revolution (365 days).
• The lunar cycle (full Moon to full Moon) is about 29.5 days.

📊 12 lunar months ≈ 354 days

👉 Difference = about 11 days

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📌 Conclusion:

Because of this difference, the date of the full Moon changes every year.

👉 Therefore, Amol’s birthday will not always fall on a full Moon day.

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3. Name two things that are incorrect in Fig. 11.10.

See Answer The two major scientific errors in the drawing are:

1. Stars are shown inside the dark, unlit portion of the Moon. This is impossible because the Moon is a solid, opaque object. We cannot see through it to the stars behind it.

2. The crescent shape of the Moon is created by direct sunlight illuminating one part of it. The drawing incorrectly shows the crescent as a shape that you can see stars through, which misunderstands what the dark part of the Moon actually is – it’s the solid surface of the Moon that is in shadow, not an empty space.

4. Look at the pictures of the Moon in Fig. 11.11, and answer the following questions.

(i) Write the correct panel number corresponding to the phases of the Moon shown in the pictures.

Answer:

(ii) List the picture labels of the phases of the Moon that are never seen from Earth.

See Answer From Earth, we never see (B) new moon phase.

 

🟢 Question 5, 6 and 7 of Class 8 Science Curiosity Chapter 11

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🟢 5. Malini saw the Moon overhead in the sky at sunset.

(i) Draw the phase of the Moon that Malini saw.

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✅ Answer:

👉 Half Moon (First Quarter Phase) 🌗

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(ii) Is the Moon in the waxing or the waning phase?

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✅ Answer:

👉 Waxing Phase ✔️

🧠 Explanation:

• Waxing = illuminated part increasing 📈
• First Quarter Moon appears:
• 🌞 rises around noon
• 🌙 overhead at sunset

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🟢 6. Ravi said, “I saw a crescent Moon, and it was rising in the East, when the Sun was setting.” Kaushalya said, “Once I saw the gibbous Moon during the afternoon in the East.” Who out of the two is telling the truth?

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✅ Answer:

👉 Kaushalya is correct ✔️

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🧠 Explanation:

🌙 Waxing Gibbous Moon:

• Rises in afternoon 🌤️
• Seen in eastern sky ✔️

🌙 Crescent Moon:

• Seen near setting Sun (west side) 🌇
• ❌ Cannot rise in east at sunset

📌 Conclusion:

👉 Ravi is incorrect, Kaushalya is correct ✔️

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🟢 7. Scientific studies show that the Moon is getting farther away from the Earth and slower in its revolution. Will luni-solar calendars need an intercalary month more often or less often?

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✅ Answer:

👉 Less often ✔️

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🧠 Explanation:

📅 Lunar year ≈ 354 days

📅 Solar year ≈ 365 days

👉 Difference ≈ 11 days

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🌙 If Moon slows down:

• Lunar month becomes longer ⏳
• Lunar year becomes longer

👉 Difference reduces

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📌 Conclusion:

👉 Intercalary month (Adhika Maas) needed less frequently ✔️

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🟢 Class 8 Science Curiosity Chapter 11 Question 8 and 9

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🟢 8. A total of 37 full Moons happen during 3 years in a solar calendar. Show that at least two of the 37 full moons must happen during the same month of the solar calendar.

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✅ Answer:

📅 3 years = 36 months

🌙 Full Moons = 37

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🧠 Logic:

👉 36 months → 36 full moons (one per month)

👉 1 full moon extra remains

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📌 Conclusion:

👉 At least one month will have 2 full moons ✔️

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🟢 9. On a particular night, Vaishali saw the Moon in the sky from sunset to sunrise. What phase of the Moon would she have noticed?

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✅ Answer:

👉 Full Moon 🌕

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🧠 Explanation:

🌕 Full Moon:

• Rises at sunset 🌇
• Visible all night 🌙
• Sets at sunrise 🌅

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📌 Conclusion:

👉 Only Full Moon shows this behavior ✔️

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🟢 Class 8 Science Curiosity Chapter 11 Question 10, 11 and 12

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🟢 10. If we stopped having leap years, in approximately how many years would the Indian Independence day happen in winter?

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✅ Answer:

👉 Approximately 500 years ✔️

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🧠 Explanation:

📅 Calendar error = 0.25 days/year

👉 1 month shift (~30 days):

= 30 ÷ 0.25 = 120 years

👉 4 months shift:

= 4 × 120 = 480 ≈ 500 years

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📌 Conclusion:

👉 Independence Day will shift to winter in ~500 years ❄️

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🟢 11. What is the purpose of launching artificial satellites?

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✅ Answer:

🛰️ Uses of Artificial Satellites:

• 📡 Communication (TV, mobile signals)
• 🧭 Navigation (GPS)
• 🌦️ Weather forecasting
• 🚨 Disaster management
• 🔬 Scientific research
• 🗺️ Mapping & planning

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📌 Conclusion:

👉 Satellites make modern life easier & advanced ✔️

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🟢 12. On which periodic phenomenon are the following measures of time based:

(i) day

(ii) month

(iii) year

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✅ Answer:

(i) Day 🌍

👉 Earth’s rotation on its axis

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(ii) Month 🌙

👉 Moon’s revolution around Earth

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(iii) Year ☀️

👉 Earth’s revolution around Sun

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📌 Conclusion:

👉 Time is based on natural astronomical cycles ✔️

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