Students rely on Class 8 Science Extra Questions and Class 8 Curiosity Chapter 11 Extra Question Answer Keeping Time with the Skies to help self-study at home.
Class 8 Science Chapter 11 Keeping Time with the Skies Extra Questions
Class 8 Science Chapter 11 Extra Questions on Keeping Time with the Skies
Keeping Time with the Skies Class 8 Very Short Question Answer
Question 1.
What is the difference between the waxing and waning phases of the Moon?
Answer:
In the waxing phase, the illuminated portion of the Moon seen from Earth increases daily, beginning after the new Moon.
In the waning phase, the visible portion decreases each night, starting after the full Moon.
Question 2.
How does the Moon’s position affect its visibility in the sky each day?
Answer:
The Moon rises about 50 minutes later each day due to its orbit around Earth. As a result, its position shifts westward daily, affecting when and where we see it in the sky.
Question 3.
What is Adhika Maasa and why is it needed in the Indian calendar system? (Competency Based Que.)
Answer:
Adhika Maasa is an extra month added every 2 – 3 years in the luni-solar calendar.
It helps synchronize the lunar year (~354 days) with the solar year (~365 days) to align festivals with seasons.
Question 4.
Why do lunar festivals not fall on the same Gregorian dates every year?
Answer:
Lunar calendars are based on Moon phases and have shorter years (~354 days).
Hence, festivals like Diwali or Eid shift about 10-11 days earlier each year in the Gregorian (solar) calendar.
Question 5.
What is the significance of a sidereal year in astronomy?
Answer:
A sidereal year is the time taken by Earth to complete one orbit relative to distant stars (~365.26 days). Astronomers use it to precisely track Earth’s position in space, independent of seasons.
Question 6.
Explain why leap years are added in the Gregorian calendar.
Answer:
The Earth takes about 365.25 days to orbit the Sun. To account for the extra 14 day each year, a leap day is added every 4 years to keep the calendar aligned with seasons.
Question 7.
hat are Amant and Purnimant month systems? (Competency Based Que.)
Answer:
In the Amant system, a month starts from new Moon to the next new Moon.
In the Purnimant system, the month goes from Full Moon to Full Moon; both are used in Indian calendars.
Question 8.
Why is the Moon sometimes seen in the daytime?
Answer:
Because the Moon reflects sunlight and rises earlier each day, it can be above the horizon during daylight hours.
This commonly happens during waxing and waning phases when the Sun and Moon are not exactly opposite.
Keeping Time with the Skies Class 8 Short Question Answer
Question 1.
Differentiate between the lunar, solar and luni-solar calendars on the basis of
(i) Basis of measurement
(ii) Year length
(iii) Example
Answer:
| Calender type | Basis of measurment | Year length | Example |
| Lunar calender | Moon’s phases | 354 days | Islamic calender |
| Solar calender | Earth’s orbit around th sun | 365/366 days | Gregorian |
| Luni-solar calender | Lunar month adjusted to solar year | ~365 days | Hindu |
Question 2.
Explain how the phases of the Moon occur. Why do they not result from Earth’s shadow?
Answer:
The Moon has no light of its own, it shines by reflecting sunlight, and exactly half of its surface is always illuminated. As the Moon orbits Earth, the angle between the Sun, Moon, and Earth changes, so we see varying portions of that lit half – this causes the familiar phases. Earth’s shadow only falls on the Moon during a lunar eclipse; it does not play any role in the everyday waxing and waning of the lunar phases.
Question 3.
How does the Moon help in timekeeping? Mention three ways.
Answer:
- The Moon’s phases follow a regular cycle of ~29.5 days, defining a lunar month.
- Festivals and religious rituals in many cultures are based on specific Moon phases.
- Observing moonrise/moonset times helps structure traditional calendars.
Question 4.
What corrections are made in the Gregorian calendar to align it with Earth’s revolution?
Answer:
- One extra day is added every 4 years (leap year = 366 days).
- Leap years are skipped every 100 years (e.g. 1900 was not a leap year).
- Every 400 years, the leap year is added back (e.g., 2000 was a leap year).
Question 5.
What are the major uses of artificial satellites? Mention any three.
Answer:
- Communication : Transmit telephone, television and internet signals.
- Weather Forecasting : Observe cloud patterns, storms, and rainfall.
- Navigation : Provide real-time location via GPS systems.
Question 6.
List three reasons why festivals in India may fall on different dates in different regions.
Answer:
- Sunrise occurs earlier in eastern India and later in western India.
- Different calendar systems (Amant/Purnimant) are followed in different regions.
- Some festivals depend on Moon’s position, which may differ slightly by location.
Question 7.
Explain the difference between Tropical year and Sidereal year. How are they used?
Answer:
- Tropical year is the time between two spring equinoxes (~365.24 days); used in seasonal calendars.
- Sidereal year is the time for Earth to complete one orbit relative to stars (~365.26 days); used by astronomers.
- The sidereal year is ~20 minutes longer due to axial precession.
Question 8.
What is the role of Meghnad Saha in India’s calendar reform and astronomy?
Answer:
Meghnad Saha was a renowned astrophysicist who developed the Saha equation for star analysis. He chaired the Calendar Reform Committee in independent India. His work led to the creation of the Indian National Calendar and the standardization of festival dates.
Keeping Time with the Skies Class 8 Long Question Answer
Question 1.
(i) Explain how the Moon gets its light.
(ii) What causes the phases of the Moon?
(iii) Why is the Moon not visible during new Moon?
(iv) How much time does the Moon take to complete one cycle of phases?
Answer:
(i) The Moon does not produce its own light; it reflects sunlight falling on it.
(ii) As the Moon revolves around the Earth, we see changing portions of its sunlit side.
(iii) On new Moon, the dark side of the Moon faces Earth, making it invisible.
(iv) The Moon takes about 29.5 days to complete one cycle of phases.
Question 2.
(i) What is a lunar calendar and how is it different from a solar calendar?
(ii) Define luni-solar calendar.
(iii) What is Adhika Maasa and why is it added?
(iv) Name any two Indian festivals based on lunar calculations.
Answer:
(i) A lunar calendar is based on Moon’s phases (~354 days/year); a solar calendar is based on Earth’s orbit around the Sun (~365 days/year).
(ii) A luni-solar calendar combines both Moon months and the solar year.
(iii) Adhika Maasa is an extra month added every 2 – 3 years to match the lunar and solar years.
(iv) Diwali, Holi.
Question 3.
(i) What is the Indian National Calendar?
(ii) When does the Indian year begin?
(iii) What are its months based on?
(iv) How is it similar to the Gregorian calendar?
Answer:
(i) It is the official solar calendar of India, developed by the Calendar Reform Committee.
(ii) The year begins on 22 March (or 21 March in leap years).
(iii) The months are based on traditional Indian names (Chaitra, Vaisakha, etc.).
(iv) It has 365 days in a year and adds a leap day every 4 years, like the Gregorian calendar.
Question 4.
Describe the complete cycle of Moon phases and explain why they occur. Also, clarify the common misconception regarding Earth’s shadow.
Answer:
(i) The Moon’s phases are caused by the portion of its sunlit side that is visible from Earth as it revolves around Earth.
(ii) New Moon → Waxing Crescent → First Quarter → Waxing Gibbous → Full Moon → Waning Gibbous → Last Quarter → Waning Crescent → New Moon.
(iii) This complete cycle takes approximately 29.5 days, which defines a lunar month.
(iv) A common misconception is that Earth’s shadow causes these phases, but that is only true during a lunar eclipse.
(v) The Moon reflects sunlight and its visibility depends on its changing position relative to Earth and the Sun.
Keeping Time with the Skies Class 8 Case Based Questions
Question 1.
During the festival of Sharad Purnima, Aanya noticed the Moon was visible for most of the night and appeared perfectly round. Her grandmother told her that this was a Full Moon and such nights are considered very auspicious. Curious, Aanya tracked the Moon for the next 10 days. She noticed that the Moon’s shape started reducing every night and its rising time became later than before. She also read in the Panchang that the the month would end with
Amavasya.
Based on this, answer the following:
(i) What phase of the Moon was visible on Sharad Purnima?
(ii) What is the period called after full Moon and before new Moon?
(iii) Why does the Moon rise later each night?
(iv) What calendar system helps fix the date of Sharad Purnima?
(v) How is Amavasya related to the end of the lunar month?
Answer:
(i) The phase was full Moon (Purnima), where the entire face of the Moon is illuminated and visible from Earth.
(ii) The period after full Moon and before new Moon is called the waning phase or Krishna Paksha.
(iii) The Moon rises about 50 minutes later each day because it moves ahead in its orbit around Earth, so Earth takes more time to rotate and bring the Moon into view.
(iv) Luni-solar calendars, such as the Hindu calendar, are used to fix the date of Sharad Purnima based on Moon phases.
(v) Amavasya, or New Moon, marks the end of the lunar month as the Moon becomes invisible from Earth.
Skill Based Questions
Question 1.
(a) Identify the Moon phase at position B.
(b) If Earth is rotating eastward, from which direction will the Moon rise?
(c) Why do people across the world observe nearly the same phase on the same day? (understanding skill)
Question 2.
Complete the flowchart showing the process of Moon’s phase change from new Moon to full Moon and back to new Moon. (Thinking skill)
Question 3.
Read the following statements carefully. They describe the process of Moon phases. Arrange them in the correct logical order.
(a) The full Moon occurs when the Moon is opposite the Sun.
(b) The new Moon is the beginning of the lunar cycle.
(c) The Moon continues to wane until it becomes a new Moon again.
(d) After the new Moon, the bright part of the Moon starts increasing.
(e) The Moon becomes a full Moon after two weeks. (Understanding skill)
Keeping Time with the Skies Extra Questions for Practice
Very Short Answer Type Questions
Question 9.
Why do solar festivals like Pongal remain on fixed Gregorian dates?
Question 10.
What is Adhika Maasa and why is it important in the Indian calendar?
Question 11.
Why can the Moon sometimes be seen in the daytime?
Short Answer Type Questions
Question 12.
Compare the lunar, solar, and luni-solar calendars with one example of each.
Question 13.
Explain the importance of artificial satellites in daily life.
Question 14.
What is a sidereal year and how is it different from a tropical year?
Long Answer Type Question
Question 1.
Describe the uses and importance of calendars in daily life. Compare the lunar, solar, and lunisolar calendars with examples
Case Based Question
Question 1.
Anirudh was observing the Moon for 10 days. He noticed that the Moon looked like a half-circle on the fifth day and gradually became more visible. His grandfather told him that the Moon would become full soon and then start disappearing again.
(i) What phase was the Moon in on the fifth day?
(ii) What is the name of the phase when the Moon becomes full?
(iii) What is the name of the decreasing phase of the Moon?.