Important Questions Class 8 Science Chapter 11: Keeping Time with the Skies

The sky shows repeated patterns that help humans measure days, months and years.
Moon phases, sunrise, seasons and satellites connect astronomy with calendars and timekeeping.

Keeping Time with the Skies explains how people used the Moon, Sun, seasons and sky observations to measure time before modern clocks. Important Questions Class 8 Science Chapter 11 help students practise phases of the Moon, waxing and waning Moon, full Moon, new Moon, moonrise time, lunar calendar, solar calendar, luni-solar calendar, Indian National Calendar, festivals, artificial satellites and space debris. The CBSE 2026 chapter explains these ideas through Moon observation, shadow activity, calendar systems, Indian sky traditions and ISRO satellites.

Key Takeaways

• Moon Phases: The Moon’s visible bright shape changes because we see different parts of its illuminated half.
• Moonrise Time: The Moon rises about 50 minutes later each day.
• Calendar Units: A day comes from Earth’s rotation, a month from Moon phases, and a year from Earth’s revolution.
• Artificial Satellites: Human-made satellites support communication, navigation, weather monitoring and scientific research.

Important Questions Class 8 Science Chapter 11 Structure 2026

Important Questions Class 8 Science Chapter 11 with Answers

Keeping Time with the Skies connects Moon phases, calendars and artificial satellites with astronomy.
Students should connect every answer with repeated sky patterns, Moon position, Earth’s motion or satellite use.
These keeping time with the skies class 8 questions follow the NCERT 2026 chapter flow.

1. What does Important Questions Class 8 Science Chapter 11 mainly teach?

Important Questions Class 8 Science Chapter 11 mainly teach Moon phases, calendars, festivals, artificial satellites and sky-based timekeeping. The chapter shows how repeated astronomical cycles help measure time.

1. Moon Skill: Explain waxing, waning, full Moon and new Moon.
2. Calendar Skill: Link day, month and year with sky cycles.
3. Festival Skill: Explain why festival dates shift.
4. Satellite Skill: Explain uses of artificial satellites.
5. Final Result: Chapter 11 teaches timekeeping through sky observations.

2. What is the name of Class 8 Science Chapter 11?

The name of Class 8 Science Chapter 11 is Keeping Time with the Skies. It explains Moon phases, calendars and artificial satellites.

1. Chapter Number: 11.
2. Chapter Name: Keeping Time with the Skies.
3. Textbook: Curiosity.
4. Final Result: Chapter 11 is about astronomical timekeeping.

3. Why did Meera notice the Moon during daytime?

Meera noticed the Moon during daytime because the Moon can be visible when it is above the horizon during daylight. It does not appear only at night.

1. Place: Ahmedabad during Patang Mahotsav.
2. Observation: Moon was visible during daytime.
3. Reason: Moonrise and moonset times shift daily.
4. Final Result: The Moon can be visible during the day.

Class 8 Science Chapter 11 Important Questions

Class 8 Science Chapter 11 important questions focus on Moon phases and calendar systems.
The chapter corrects the idea that Moon phases happen due to Earth’s shadow.
Students should mention Sun, Moon and Earth positions in phase-based answers.

4. Why does the Moon appear to change shape?

The Moon appears to change shape because we see different parts of its illuminated half. The Moon itself remains spherical.

1. Moon Shape: Spherical.
2. Light Source: Sun.
3. Visible Part: Illuminated part facing Earth.
4. Final Result: Moon phases depend on visible sunlight-reflecting portion.

5. Does the Moon produce its own light?

No, the Moon does not produce its own light. It shines because it reflects sunlight.

1. Source of Light: Sun.
2. Moon Surface: Reflects sunlight.
3. Observation: Bright part is sunlight-lit.
4. Final Result: Moonlight is reflected sunlight.

6. Why is the whole Moon not visible every night?

The whole Moon is not visible every night because the entire illuminated half does not always face Earth. Only the part visible from Earth appears bright.

1. Illuminated Half: Faces the Sun.
2. Earth-facing Side: Changes during revolution.
3. Visible Shape: Depends on Moon’s position.
4. Final Result: Only part of the illuminated Moon may face Earth.

7. Are Moon phases caused by Earth’s shadow?

No, Moon phases are not caused by Earth’s shadow. They are caused by changing relative positions of the Sun, Moon and Earth.

1. Wrong Idea: Earth’s shadow causes phases.
2. Correct Cause: Moon’s revolution around Earth.
3. Earth Shadow: Causes lunar eclipse.
4. Final Result: Moon phases are not lunar eclipses.

8. Why are lunar eclipses rare if full Moon happens every month?

Lunar eclipses are rare because the Moon’s orbit is slightly tilted relative to Earth’s orbit. Earth’s shadow does not fall on the Moon every full Moon.

1. Full Moon: Happens every month.
2. Orbit Tilt: Prevents monthly eclipse.
3. Eclipse Condition: Sun, Earth and Moon must align.
4. Final Result: A full Moon does not always cause a lunar eclipse.

Phases of Moon Class 8 Questions

Phases of moon class 8 questions explain the changing visible shape of the Moon.
The cycle includes full Moon, gibbous, half Moon, crescent and new Moon.
A full cycle from one full Moon to the next takes about a month.

9. What are phases of the Moon?

Phases of the Moon are the changing shapes of the bright portion of the Moon seen from Earth. They repeat in a cycle.

1. Bright Portion: Sunlit part visible from Earth.
2. Cycle: Repeats every month.
3. Examples: Crescent, gibbous and full Moon.
4. Final Result: Moon phases are changing visible bright shapes.

10. What is full Moon day?

Full Moon day is the day when the Moon appears as a full bright circle. It is also called Purnima.

1. Appearance: Full bright circle.
2. Indian Name: Purnima.
3. Position: Moon is nearly opposite the Sun.
4. Final Result: Full Moon day shows the fully illuminated visible disc.

11. What is new Moon day?

New Moon day is the day when the Moon is not visible from Earth. It is also called Amavasya.

1. Appearance: Moon is not visible.
2. Indian Name: Amavasya.
3. Reason: Illuminated part does not face Earth.
4. Final Result: New Moon day shows no visible illuminated portion.

12. What is crescent Moon?

Crescent Moon is the phase where less than half of the illuminated portion is visible. It appears as a thin curved shape.

1. Visible Part: Less than half.
2. Shape: Thin curved bright part.
3. Occurrence: Seen near new Moon days.
4. Final Result: Crescent Moon shows less than half illumination.

13. What is gibbous Moon?

Gibbous Moon is the phase where more than half of the illuminated portion is visible. It occurs between half Moon and full Moon.

1. Visible Part: More than half.
2. Shape: Rounded but not full.
3. Position: Between half and full Moon.
4. Final Result: Gibbous Moon shows more than half illumination.

14. How long does one full cycle of Moon phases take?

One full cycle of Moon phases takes about 29.5 days. It is nearly one month.

1. Cycle: Full Moon to next full Moon.
2. Duration: About 29.5 days.
3. Calendar Use: Basis of lunar month.
4. Final Result: Moon phase cycle lasts nearly a month.

Waxing and Waning Moon Class 8 Questions

Waxing and waning moon class 8 questions explain whether the bright portion increases or decreases.
Waning means the visible bright part decreases.
Waxing means the visible bright part increases.

15. What is the waning period of the Moon?

The waning period is when the bright portion of the Moon decreases from full Moon to new Moon. It lasts about two weeks.

1. Start: Full Moon.
2. End: New Moon.
3. Indian Name: Krishna Paksha.
4. Final Result: Waning Moon decreases in visible brightness.

16. What is the waxing period of the Moon?

The waxing period is when the bright portion of the Moon increases from new Moon to full Moon. It lasts about two weeks.

1. Start: New Moon.
2. End: Full Moon.
3. Indian Name: Shukla Paksha.
4. Final Result: Waxing Moon increases in visible brightness.

17. What is Krishna Paksha?

Krishna Paksha is the waning period of the Moon. The bright portion decreases during this period.

1. Phase Type: Waning.
2. Direction: Full Moon to new Moon.
3. Duration: About two weeks.
4. Final Result: Krishna Paksha means decreasing Moon brightness.

18. What is Shukla Paksha?

Shukla Paksha is the waxing period of the Moon. The bright portion increases during this period.

1. Phase Type: Waxing.
2. Direction: New Moon to full Moon.
3. Duration: About two weeks.
4. Final Result: Shukla Paksha means increasing Moon brightness.

19. When is a waxing Moon easiest to spot?

A waxing Moon is easiest to spot at sunset. It appears in the sky after new Moon as its bright portion grows.

1. Best Time: Sunset.
2. Phase: Waxing.
3. Observation: Moon appears away from Sun gradually.
4. Final Result: Waxing Moon is best observed at sunset.

20. When is a waning Moon easiest to spot?

A waning Moon is easiest to spot at sunrise. It appears closer to the Sun as its bright portion decreases.

1. Best Time: Sunrise.
2. Phase: Waning.
3. Observation: Moon appears nearer to Sun daily.
4. Final Result: Waning Moon is best observed at sunrise.

Full Moon and New Moon Class 8 Questions

Full moon and new moon class 8 questions explain the two most important Moon positions.
Full Moon occurs when the illuminated portion faces Earth fully.
New Moon occurs when the illuminated portion faces away from Earth.

21. Why is the full Moon seen as a complete circle?

The full Moon is seen as a complete circle because the entire illuminated part facing Earth is visible. The Moon is nearly opposite the Sun.

1. Sunlit Half: Faces Earth.
2. Position: Opposite the Sun in the sky.
3. Appearance: Full bright disc.
4. Final Result: Full Moon shows the complete illuminated face.

22. Why is the Moon not visible on new Moon day?

The Moon is not visible on new Moon day because its illuminated half faces away from Earth. The non-illuminated side faces us.

1. Moon Position: Near the Sun in the sky.
2. Earth-facing Side: Dark side.
3. Visible Light: Almost none.
4. Final Result: New Moon shows the non-illuminated side.

23. Where is the Moon compared to the Sun on full Moon day?

On full Moon day, the Moon is nearly opposite the Sun in the sky. When the Sun rises in the east, the Moon is almost setting in the west.

1. Sunrise: Sun in east.
2. Moon Position: Nearly west.
3. Separation: Farthest from Sun in the sky.
4. Final Result: Full Moon appears nearly opposite the Sun.

24. Where is the Moon compared to the Sun on new Moon day?

On new Moon day, the Moon appears closest to the Sun in the sky. Its illuminated side faces away from Earth.

1. Moon Position: Near Sun direction.
2. Visibility: Not visible.
3. Phase: New Moon.
4. Final Result: New Moon appears closest to the Sun.

25. If someone sees the Moon from sunset to sunrise, what phase is it?

The Moon is in the full Moon phase. A full Moon rises near sunset and sets near sunrise.

1. Visible Time: Sunset to sunrise.
2. Position: Opposite Sun.
3. Phase: Full Moon.
4. Final Result: A Moon visible all night is full Moon.

Moonrise Time Class 8 Questions

Moonrise time class 8 questions explain why the Moon does not rise at the same time every day.
The Moon moves ahead in its orbit while Earth rotates once.
So Earth must rotate a little more for the Moon to appear in nearly the same sky position.

26. Why does moonrise time change every day?

Moonrise time changes because the Moon moves ahead in its orbit around Earth each day. Earth must rotate extra time to face it again.

1. Earth Rotation: About 24 hours.
2. Moon Revolution: Continues during that time.
3. Extra Rotation: Needed to see Moon again.
4. Final Result: Moonrise shifts because the Moon keeps orbiting Earth.

27. How much later does the Moon rise each day?

The Moon rises about 50 minutes later each day. This is why its position and rising time shift daily.

1. Daily Shift: About 50 minutes.
2. Cause: Moon’s orbital motion.
3. Observation: Moonrise time changes.
4. Final Result: Moonrise is delayed by about 50 minutes daily.

28. Can the Moon rise in the afternoon?

Yes, the Moon can rise in the afternoon. Around some phases, moonrise may occur between about 2:00 p.m. and 4:00 p.m.

1. Moonrise: Not fixed at night.
2. Possible Time: Afternoon.
3. Visibility: Moon may be seen in daylight.
4. Final Result: The Moon can rise during daytime.

29. Why is the Moon sometimes visible during the day?

The Moon is sometimes visible during the day because it may be above the horizon while sunlight is present. Its reflected sunlight can still reach us.

1. Moon Position: Above horizon.
2. Sunlight: Also present.
3. Visibility: Bright Moon can be seen.
4. Final Result: Daytime Moon visibility depends on Moon position.

30. Does the Moon always rise when the Sun sets?

No, the Moon does not always rise when the Sun sets. That happens approximately around full Moon.

1. Common Belief: Moon rises at sunset.
2. Correct Case: Mostly full Moon.
3. Daily Change: Moonrise shifts by about 50 minutes.
4. Final Result: Moonrise does not always match sunset.

Lunar Calendar Class 8 Questions

Lunar calendar class 8 questions explain calendars based on Moon phases.
A lunar month is about 29.5 days.
A lunar year has 12 lunar months and is about 354 days long.

31. What is a lunar calendar?

A lunar calendar is a calendar based on the Moon’s phase cycle. It uses lunar months of about 29.5 days.

1. Basis: Moon phases.
2. Month Length: About 29.5 days.
3. Year: 12 lunar months.
4. Final Result: Lunar calendars follow the Moon.

32. How long is a lunar year?

A lunar year is about 354 days long. It has 12 lunar months.

1. One Lunar Month: About 29.5 days.
2. Twelve Months: About 354 days.
3. Comparison: Shorter than solar year.
4. Final Result: Lunar year is about 11 days shorter than solar year.

33. Why do seasons not stay in the same lunar months every year?

Seasons do not stay in the same lunar months because the lunar year is about 354 days, while seasons repeat in about 365 days.

1. Lunar Year: 354 days.
2. Solar Year: About 365 days.
3. Difference: Nearly 11 days.
4. Final Result: Lunar months shift against seasons.

34. Why can Eid-ul-Fitr occur in different Gregorian months?

Eid-ul-Fitr can occur in different Gregorian months because it follows a lunar calendar. Pure lunar calendars do not adjust for the solar year.

1. Calendar Basis: Moon phases.
2. Annual Shift: About 11 days earlier.
3. Gregorian Calendar: Solar calendar.
4. Final Result: Lunar festivals shift through Gregorian months.

Solar Calendar Class 8 Questions

Solar calendar class 8 questions explain calendars based on the Sun, Earth’s revolution and seasons.
Solar calendars help keep months aligned with seasons.
The Gregorian calendar is a widely used solar calendar.

35. What is a solar calendar?

A solar calendar is based on the cycle of seasons caused by Earth’s revolution around the Sun. It has about 365 days.

1. Basis: Earth’s revolution.
2. Year Length: About 365 days.
3. Example: Gregorian calendar.
4. Final Result: Solar calendars follow the seasonal year.

36. What is a mean solar day?

A mean solar day is the average time the Sun takes to return to its highest position in the sky. It is 24 hours.

1. Sun Position: Highest point in sky.
2. Average Time: 24 hours.
3. Unit: Day.
4. Final Result: Mean solar day is 24 hours.

37. How can the highest position of the Sun be identified?

The Sun’s highest position can be identified by the shortest shadow of a vertical stick. The shadow is shortest when the Sun is highest.

1. Stick: Fixed vertically.
2. Shadow: Measured during daytime.
3. Shortest Shadow: Sun’s highest position.
4. Final Result: Shortest shadow marks the Sun’s highest position.

38. Why do solar calendars have leap years?

Solar calendars have leap years because Earth takes nearly 365 and a quarter days to complete one revolution. Extra quarters add up to one day in four years.

1. Earth Revolution: About 365¼ days.
2. Extra Time: Quarter day each year.
3. Adjustment: Add one day every four years.
4. Final Result: Leap years keep calendars aligned with seasons.

39. What happens in February during a Gregorian leap year?

February has 29 days during a Gregorian leap year. The extra day helps adjust the calendar.

1. Regular February: 28 days.
2. Leap Year February: 29 days.
3. Purpose: Seasonal alignment.
4. Final Result: Leap year adds one day to February.

Luni Solar Calendar Class 8 Questions

Luni solar calendar class 8 questions explain calendars that use both Moon phases and seasons.
They count months using the Moon and adjust to the solar year.
Many Indian calendars are luni-solar calendars.

40. What is a luni-solar calendar?

A luni-solar calendar uses Moon phases for months and adds adjustments to stay aligned with seasons. It combines lunar and solar features.

1. Month Basis: Moon phases.
2. Year Adjustment: Solar cycle.
3. Indian Use: Common in many regions.
4. Final Result: Luni-solar calendars combine Moon and seasons.

41. Why do luni-solar calendars need an extra month?

Luni-solar calendars need an extra month because 12 lunar months are about 11 days shorter than a solar year. The difference grows over time.

1. Lunar Year: 354 days.
2. Solar Year: About 365 days.
3. Difference: Nearly 11 days each year.
4. Final Result: An extra month corrects the lunar-solar difference.

42. What is Adhika Maasa?

Adhika Maasa is an extra month added in some luni-solar calendars every few years. It keeps lunar months aligned with seasons.

1. Meaning: Intercalary month.
2. Frequency: Every 2–3 years.
3. Purpose: Calendar correction.
4. Final Result: Adhika Maasa synchronises lunar months with seasons.

43. What are Amant and Purnimant calendars?

Amant calendars begin a new month after new Moon, while Purnimant calendars begin after full Moon. Both use lunar phases.

1. Amant: New month after new Moon.
2. Purnimant: New month after full Moon.
3. Use: Found in Indian traditions.
4. Final Result: Amant and Purnimant differ in month start.

Indian National Calendar Class 8 Questions

Indian National Calendar class 8 questions cover India’s official solar calendar.
It is used along with the Gregorian calendar.
It follows the Shaka Era and begins with Chaitra.

44. What is the Indian National Calendar?

The Indian National Calendar is a solar calendar used by the Government of India with the Gregorian calendar. It has 365 days in a regular year.

1. Type: Solar calendar.
2. Era: Shaka Era.
3. Official Use: Government purposes.
4. Final Result: Indian National Calendar is India’s official solar calendar.

45. When does the Indian National Calendar year begin?

The Indian National Calendar year begins on 22 March in a regular year. In a leap year, it begins on 21 March.

1. Regular Year: 22 March.
2. Leap Year: 21 March.
3. First Month: Chaitra.
4. Final Result: The calendar begins with Chaitra.

46. How many days do months have in the Indian National Calendar?

Months in the Indian National Calendar have either 30 or 31 days. In a regular year, second to sixth months have 31 days.

1. Month Lengths: 30 or 31 days.
2. First Month: Chaitra.
3. Leap Adjustment: Extra day added to Chaitra.
4. Final Result: Indian National Calendar months have 30 or 31 days.

47. What was the Calendar Reform Committee?

The Calendar Reform Committee was set up by the Government of India in 1952. It examined calendars and recommended a uniform national calendar.

1. Year Set Up: 1952.
2. Purpose: Calendar reform.
3. Chairperson: Meghnad Saha.
4. Final Result: The committee recommended a unified national calendar.

48. When was the Unified National Calendar adopted?

The Unified National Calendar was adopted from 21 March 1956 CE. This corresponded to 1 Chaitra 1878 Saka.

1. Adoption Date: 21 March 1956 CE.
2. Saka Date: 1 Chaitra 1878 Saka.
3. Use: Along with Gregorian calendar.
4. Final Result: India adopted the national calendar in 1956.

Festivals and Astronomy Class 8 Questions

Festivals and astronomy class 8 questions explain why some festival dates shift.
Many Indian festivals depend on Moon phases, lunar months or solar cycles.
This is why their Gregorian dates may vary.

49. Why do many Indian festivals fall on different Gregorian dates each year?

Many Indian festivals fall on different Gregorian dates because they follow lunar or luni-solar calendars. These calendars do not match the Gregorian solar calendar exactly.

1. Diwali: New Moon of Kartika.
2. Holi: Full Moon of Phalguna.
3. Buddha Purnima: Full Moon of Vaisakha.
4. Final Result: Moon-based festivals shift in Gregorian dates.

50. Which Moon phase is linked with Diwali?

Diwali is linked with the new Moon of the month of Kartika. This is why it occurs on Amavasya.

1. Festival: Diwali.
2. Moon Phase: New Moon.
3. Month: Kartika.
4. Final Result: Diwali falls on Kartika Amavasya.

51. Which Moon phase is linked with Holi?

Holi is linked with the full Moon of the month of Phalguna. It is celebrated on Phalguna Purnima.

1. Festival: Holi.
2. Moon Phase: Full Moon.
3. Month: Phalguna.
4. Final Result: Holi falls on Phalguna Purnima.

52. Why do Makar Sankranti and Pongal occur near the same Gregorian date every year?

Makar Sankranti and Pongal occur near the same Gregorian date because they follow a solar sidereal calendar. Solar-based festivals shift very slowly.

1. Festival Type: Solar.
2. Calendar Link: Sidereal solar year.
3. Date Pattern: Almost same annually.
4. Final Result: Solar festivals stay near fixed Gregorian dates.

53. Why can festival dates differ by a day across Indian regions?

Festival dates can differ by a day because sunrise occurs at different times across India. Lunar phase at sunrise may differ by region.

1. Eastern India: Sunrise earlier.
2. Western India: Sunrise later.
3. Festival Rule: Often depends on lunar phase at sunrise.
4. Final Result: Regional sunrise timing can shift festival dates.

Artificial Satellites Class 8 Questions

Artificial satellites class 8 questions explain human-made objects orbiting Earth.
They appear as moving points of light in the night sky.
Satellites help communication, navigation, weather study and scientific research.

54. What is an artificial satellite?

An artificial satellite is a human-made object launched into space to orbit Earth or another body. It supports many useful activities.

1. Made By: Humans.
2. Motion: Orbits Earth or another body.
3. Example: Cartosat.
4. Final Result: Artificial satellites are man-made orbiting objects.

55. How is the Moon different from artificial satellites?

The Moon is Earth’s natural satellite, while artificial satellites are made and launched by humans. Both orbit Earth.

1. Moon: Natural satellite.
2. Artificial Satellites: Human-made.
3. Common Feature: Orbit Earth.
4. Final Result: Moon is natural, artificial satellites are launched by humans.

56. What are artificial satellites used for?

Artificial satellites are used for communication, navigation, weather monitoring, disaster management and scientific research. They provide information from space.

1. Communication: Signals and broadcasting.
2. Navigation: Location support.
3. Weather: Storm and cloud monitoring.
4. Final Result: Satellites support daily life and science.

57. What is Cartosat used for?

Cartosat satellites capture high-quality images of Earth. These images help improve maps, plan cities and manage disasters.

1. Organisation: ISRO.
2. Use: Earth imaging.
3. Application: Mapping and disaster management.
4. Final Result: Cartosat supports Earth observation.

58. What is AstroSat used for?

AstroSat is used for scientific observations of stars and other celestial objects. It is an Indian space science mission.

1. Mission Type: Space observatory.
2. Observation Target: Stars and celestial objects.
3. Organisation: ISRO.
4. Final Result: AstroSat studies objects in space.

59. What is space debris?

Space debris is non-working satellites, rocket parts and other junk left in space. It can collide with working satellites.

1. Sources: Old satellites and rocket parts.
2. Risk: Collision with active satellites.
3. Problem: Crowds space.
4. Final Result: Space debris is dangerous space junk.

60. Why are artificial satellites seen just after sunset or before sunrise?

Artificial satellites are often seen then because they reflect sunlight while the sky is dark enough. They look like moving points of light.

1. Best Time: Just after sunset or before sunrise.
2. Reason: Satellite reflects sunlight.
3. Appearance: Moving bright point.
4. Final Result: Reflected sunlight makes satellites visible.

NCERT Class 8 Science Chapter 11 Questions

NCERT Class 8 Science Chapter 11 questions test Moon phases, calendars, eclipses, festivals and satellites.
Students should avoid saying that Earth’s shadow causes phases.
These NCERT Class 8 Science Chapter 11 questions follow the 2026 exercise pattern.

61. Is it true that we see only the part of the Moon that reflects sunlight towards us?

Yes, it is true. We see only the illuminated portion of the Moon that reflects sunlight towards Earth.

1. Moon Light: Reflected sunlight.
2. Visible Part: Sunlit part facing Earth.
3. Observation: Shape changes with position.
4. Final Result: We see reflected sunlight from the Moon.

62. Is it true that Earth’s shadow causes Moon phases?

No, it is false. Earth’s shadow causes a lunar eclipse, not regular Moon phases.

1. Moon Phases: Due to Moon’s revolution.
2. Lunar Eclipse: Due to Earth’s shadow.
3. Frequency: Eclipses are rare.
4. Final Result: Earth’s shadow does not cause Moon phases.

63. Is it true that calendars are based on predictable astronomical cycles?

Yes, it is true. Days, months and years are based on repeated motions of Earth, Moon and Sun.

1. Day: Earth’s rotation.
2. Month: Moon phase cycle.
3. Year: Earth’s revolution around Sun.
4. Final Result: Calendars use repeated sky cycles.

64. Is it true that the Moon can only be seen at night?

No, it is false. The Moon can also be seen during the day when it is above the horizon and bright enough.

1. Daytime Moon: Possible.
2. Reason: Moonrise time changes.
3. Observation: It may appear in afternoon or morning.
4. Final Result: The Moon is not limited to night visibility.

65. Does a birthday on full Moon fall on full Moon every year?

No, it does not always fall on full Moon every year in a solar calendar. The Moon phase cycle and Gregorian dates do not match exactly.

1. Full Moon Cycle: About 29.5 days.
2. Gregorian Year: Solar calendar.
3. Mismatch: Moon phase shifts on same date.
4. Final Result: Same calendar date need not have same Moon phase.

66. If Malini saw the Moon overhead at sunset, what phase was it?

Malini saw a half Moon in the waxing phase. A waxing half Moon can appear overhead around sunset.

1. Time: Sunset.
2. Position: Overhead.
3. Phase: Waxing half Moon.
4. Final Result: The Moon was in waxing half phase.

67. Ravi saw a crescent Moon rising in the east when the Sun was setting. Is he correct?

Ravi is likely correct if it was a waxing crescent. A waxing crescent can be seen after sunset in the western sky, but rising in east at sunset is not correct for a crescent.

1. Crescent at Sunset: Usually near western sky.
2. Rising in East: Not suitable for crescent at sunset.
3. Conclusion: Ravi’s full statement is incorrect.
4. Final Result: A crescent Moon does not rise in east at sunset.

68. Kaushalya saw a gibbous Moon during afternoon in the east. Is she correct?

Kaushalya can be correct. A waxing gibbous Moon may rise in the afternoon and be visible in the eastern sky.

1. Phase: Gibbous Moon.
2. Time: Afternoon.
3. Direction: East after moonrise.
4. Final Result: A gibbous Moon can be seen in eastern afternoon sky.

69. Why must at least two of 37 full Moons occur in the same solar calendar month during 3 years?

There are only 36 solar calendar months in 3 years, but 37 full Moons occur. At least one month must contain two full Moons.

1. Total Months: 3 × 12 = 36.
2. Total Full Moons: 37.
3. Logic: More full Moons than months.
4. Final Result: One solar month must contain two full Moons.

70. On which phenomenon is a day based?

A day is based on Earth’s rotation and the Sun’s apparent return to its highest position. A mean solar day is 24 hours.

1. Earth Motion: Rotation.
2. Sun Position: Highest point to next highest point.
3. Duration: 24 hours.
4. Final Result: A day is based on Earth’s rotation.

71. On which phenomenon is a month based?

A month is based on the Moon’s cycle of phases. One cycle takes about 29.5 days.

1. Moon Motion: Revolution around Earth.
2. Visible Pattern: Phases repeat.
3. Duration: About 29.5 days.
4. Final Result: A month is based on Moon phases.

72. On which phenomenon is a year based?

A year is based on Earth’s revolution around the Sun and the cycle of seasons. It takes nearly 365¼ days.

1. Earth Motion: Revolution around Sun.
2. Season Cycle: Repeats annually.
3. Duration: Nearly 365¼ days.
4. Final Result: A year is based on Earth’s revolution.

Class 8 Science Chapter 11 Questions and Answers

Class 8 Science Chapter 11 questions and answers should use astronomy terms accurately.
Students should mention whether a calendar follows the Moon, Sun or both.
These answers support quick revision for school tests.

73. What is the purpose of launching artificial satellites?

The purpose is to support communication, navigation, weather monitoring, disaster management and scientific research. Satellites observe Earth and space from orbit.

1. Earth Use: Mapping and weather monitoring.
2. Daily Use: Communication and navigation.
3. Science Use: Space observations.
4. Final Result: Artificial satellites provide useful information from space.

74. Why are the Sun’s changing sunrise positions useful?

The Sun’s changing sunrise positions show the seasonal cycle. Ancient observers used such patterns to track the year.

1. Summer: Sun rises northward of east.
2. Winter: Sun rises southward of east.
3. Annual Cycle: Repeats every year.
4. Final Result: Sunrise shifts helped build calendars.

75. What are Uttarayan and Dakshinayan?

Uttarayan is the Sun’s apparent northward movement from December to June. Dakshinayan is its apparent southward movement from June to December.

1. Uttarayan: December to June.
2. Dakshinayan: June to December.
3. Cause: Earth’s revolution and tilted axis.
4. Final Result: They describe the Sun’s apparent yearly movement.

76. Who was Meghnad Saha?

Meghnad Saha was an Indian astrophysicist who developed the Saha equation. He also chaired the Calendar Reform Committee.

1. Field: Astrophysics.
2. Contribution: Saha equation.
3. Calendar Role: CRC chairperson.
4. Final Result: Meghnad Saha helped shape India’s calendar reform.

77. Who was Vikram Sarabhai?

Vikram Sarabhai was a researcher in space science and nuclear physics. He is known as the Father of the Indian Space Programme.

1. Field: Space science.
2. Role: Pioneered Indian satellite efforts.
3. Institution: VSSC is named after him.
4. Final Result: Vikram Sarabhai led India’s space programme vision.

78. Why do tides come about 50 minutes later each day?

Tides come about 50 minutes later because tide timing is closely related to the Moon’s position. The Moon also returns to a similar sky position about 50 minutes later daily.

1. Moon Motion: Shifts daily.
2. Moonrise Delay: About 50 minutes.
3. Tide Pattern: Follows similar delay.
4. Final Result: Tide timing is linked with the Moon.

Class 8 Science Chapter List