CBSE Class 8 Science Chapter 11 Keeping Time With The Skies MCQs Set 01

Multiple Choice Questions (MCQs) for Class 8 Science: Chapter 11 Keeping Time With The Skies

Review structured MCQ sets for Class 8 Science Chapter 11 Keeping Time With The Skies. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Practice Chapter 11 Keeping Time With The Skies MCQs for Class 8 Science

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Question: When Meera observed the Moon during the day at the Patang Mahotsav, what surprised her most about what she saw?
A. The Moon appeared as a full circle
B. The Moon was visible even though the Sun was up
C. The Moon was not reflecting sunlight
D. The Moon had changed into a different shape
Show Answer & Explanation

Answer: (B) The Moon was visible even though the Sun was up

Explanation:
Meera was surprised to see the Moon shining during daytime because she had previously thought it only appeared at night. While she knew the Moon's shape changes, seeing it during the day when the Sun was also visible was unexpected for her.

Question: According to the chapter, what is the primary reason the Moon appears to change shape from night to night?
A. Earth's shadow falls on the Moon
B. The Moon is actually changing its physical shape
C. Different portions of the Moon's illuminated side face Earth as it revolves
D. The Moon is moving away from Earth gradually
Show Answer & Explanation

Answer: (C) Different portions of the Moon's illuminated side face Earth as it revolves

Explanation:
The chapter explains that the Moon itself does not change shape—only what we see of it changes. As the Moon revolves around Earth, different amounts of its illuminated half become visible from our perspective, creating the appearance of changing phases.

Question: During Activity 11.1, students recorded that after about 15 days, they could not see the Moon at sunrise or sunset. What does this observation indicate about the Moon's position?
A. The Moon had stopped revolving around Earth
B. The Moon was too close to the Sun in the sky to be visible
C. The Moon had moved behind Earth
D. The Moon's orbit had changed direction
Show Answer & Explanation

Answer: (B) The Moon was too close to the Sun in the sky to be visible

Explanation:
When the bright portion of the Moon has decreased to nearly nothing and the Moon appears very close to the Sun in the sky, it becomes too difficult to spot during sunrise or sunset. At this point, the Moon is in its new Moon phase, positioned between Earth and the Sun.

Question: What is the relationship between the waxing period of the Moon and its position relative to the Sun?
A. The Moon moves farther from the Sun as it waxes
B. The Moon moves closer to the Sun as it waxes
C. The Moon's distance from the Sun remains constant during waxing
D. The waxing period has no connection to the Sun's position
Show Answer & Explanation

Answer: (A) The Moon moves farther from the Sun as it waxes

Explanation:
• During waxing (Shukla Paksha), the illuminated portion visible from Earth increases
• As more of the illuminated side becomes visible, the Moon must be moving away from the Sun's direction
• On the full Moon day, the Moon is farthest from the Sun, appearing opposite to it in the sky
• This movement away is what allows us to see increasing portions of the illuminated hemisphere.

Question: In the ball and stick activity (Activity 11.2), when the ball is held towards the direction of the lamp, what does the observer see?
A. The entire illuminated portion of the ball
B. A crescent-shaped illuminated portion
C. No illuminated portion at all
D. A gibbous-shaped illuminated portion
Show Answer & Explanation

Answer: (C) No illuminated portion at all

Explanation:
When the ball (representing the Moon) is held towards the lamp (representing the Sun), the observer (representing Earth) faces the non-illuminated side of the ball. This position corresponds to the new Moon day, when the illuminated portion cannot be seen from Earth.

Question: What astronomical observation allows people to determine the highest point of the Sun in the sky during the day?
A. Measuring the angle of sunlight
B. Observing the color of the sky
C. Finding when the shadow cast by an object is shortest
D. Watching for changes in wind patterns
Show Answer & Explanation

Answer: (C) Finding when the shadow cast by an object is shortest

Explanation:
The chapter states that the shadow cast by an object is shortest when the Sun reaches its highest position in the sky. This observation became the foundation for measuring the mean solar day, which lasts 24 hours on average.

Question: Why do lunar calendars have a problem staying synchronized with the seasons over multiple years?
A. The Moon's phases are irregular and unpredictable
B. A lunar year of 354 days is shorter than the solar year of approximately 365 days
C. The seasons occur at different times each year
D. The Earth's rotation is slowing down gradually
Show Answer & Explanation

Answer: (B) A lunar year of 354 days is shorter than the solar year of approximately 365 days

Explanation:
Lunar calendars are based on the Moon's phases and consist of 12 lunar months totaling about 354 days. The solar year is approximately 365 days long. This difference of roughly 11 days per year means that lunar months gradually shift relative to the seasons, causing them to become desynchronized over successive years.

Question: What adjustment do solar calendars like the Gregorian calendar make to account for the extra quarter day in Earth's revolution around the Sun?
A. They remove one day every four years
B. They add an extra day every four years if the year is divisible by four
C. They extend the length of each month slightly
D. They skip the month of February every few years
Show Answer & Explanation

Answer: (B) They add an extra day every four years if the year is divisible by four

Explanation:
The Earth takes approximately 365.25 days to complete one orbit around the Sun. The Gregorian calendar adds a leap day (February 29) every four years to account for these extra hours. However, the calendar also includes additional refinements—skipping leap years every 100 years but reinstating them every 400 years—to maintain long-term accuracy.

Question: Which of the following festivals is tied to a lunar phase according to the chapter?
A. Makar Sankranti
B. Vaisakhi
C. Diwali
D. Pongal
Show Answer & Explanation

Answer: (C) Diwali

Explanation:
The chapter explicitly states that Diwali falls on the new Moon of the month of Kartika in luni-solar calendars. Other festivals mentioned as lunar-based include Holi (full Moon of Phalguna) and Buddha Purnima (full Moon of Vaisakha). In contrast, Makar Sankranti, Vaisakhi, and Pongal follow the solar sidereal calendar.

Question: How does the Indian National Calendar differ from the Gregorian calendar in terms of month lengths?
A. All months have 30 days
B. Months have either 30 or 31 days, with the second through sixth months having 31 days
C. Months have either 28 or 29 days
D. Month lengths vary based on the lunar phases
Show Answer & Explanation

Answer: (B) Months have either 30 or 31 days, with the second through sixth months having 31 days

Explanation:
The Indian National Calendar consists of 365 days per year. In a regular year, the second through sixth months have 31 days while the remaining months have 30 days. This differs from the Gregorian calendar, where month lengths are distributed differently and February has only 28 days (or 29 in leap years).

Question: What is the significance of the term "Uttarayan" in the context of ancient Indian sky observations?
A. It marks the arrival of winter
B. It describes the apparent southward movement of the Sun from June to December
C. It describes the apparent northward movement of the Sun from December to June
D. It refers to the lunar month of Kartika
Show Answer & Explanation

Answer: (C) It describes the apparent northward movement of the Sun from December to June

Explanation:
According to the 'Our scientific heritage' section, Uttarayan refers to the apparent northward movement of the Sun from December to June. This occurs because the Sun does not rise exactly in the East throughout the year—in summer it rises northward of East, marking this seasonal shift that ancient observers carefully recorded.

Question: What does the chapter suggest happens to the Moon's position in the sky between consecutive days when observed at the same time (e.g., both at sunrise)?
A. The Moon remains in exactly the same position
B. The Moon appears shifted because it moves ahead in its orbit while Earth rotates
C. The Moon moves backward relative to its previous position
D. The Moon's position depends only on the season
Show Answer & Explanation

Answer: (B) The Moon appears shifted because it moves ahead in its orbit while Earth rotates

Explanation:
• Earth completes one rotation in 24 hours
• During those 24 hours, the Moon also moves along its orbit around Earth
• The Moon advances further in its orbit than Earth's single rotation brings the observer back to the same spot
• Therefore, the Moon takes about 50 minutes longer to return to nearly the same position in the sky
• This causes the apparent shift in the Moon's location from day to day.

Question: According to the chapter, what is the primary purpose of artificial satellites orbiting Earth?
A. To replace the Moon in the night sky
B. To provide communication, navigation, weather monitoring, disaster management, and scientific research support
C. To prevent space junk from reaching Earth
D. To study the phases of the Moon
Show Answer & Explanation

Answer: (B) To provide communication, navigation, weather monitoring, disaster management, and scientific research support

Explanation:
The chapter states that artificial satellites help in many ways including communication, navigation, weather monitoring, disaster management, and scientific research. Examples include ISRO's Cartosat series for mapping, AstroSat for observing stars and celestial objects, and missions like Chandrayaan and Mangalyaan for planetary exploration.

Question: In a luni-solar calendar, what happens approximately every 2 to 3 years to keep the calendar synchronized with seasons?
A. A lunar month is removed from the calendar
B. An extra month called Adhika Maasa (intercalary month) is added
C. The calendar skips ahead by one week
D. The lengths of all months are adjusted
Show Answer & Explanation

Answer: (B) An extra month called Adhika Maasa (intercalary month) is added

Explanation:
Luni-solar calendars combine lunar and solar elements. The 12 lunar months total 354 days, falling short of the solar year by about 11 days. To prevent seasons from drifting relative to calendar months, an intercalary month is inserted every 2 to 3 years, bringing the accumulated difference back in line with the solar year.

Question: What would happen if the Moon were twice as far from Earth as it currently is, while maintaining the same orbital period around Earth?
A. The phases of the Moon would not change
B. The Moon would receive less sunlight and appear dimmer
C. The cycle of lunar phases would take half as long
D. People on different parts of Earth would see different phases on the same day
Show Answer & Explanation

Answer: (B) The Moon would receive less sunlight and appear dimmer

Explanation:
If the Moon were farther away while keeping its orbital period constant, it would still go through the same phases because phases depend on the relative positions of the Sun, Moon, and Earth—not on distance. However, the Moon would appear smaller and dimmer to us because it would receive the same amount of sunlight but be farther away, reducing the light reaching Earth from its reflected surface.

Question: At what altitude above Earth's surface do most artificial satellites orbit, and approximately how long does each complete orbit take?
A. About 400 km altitude, taking roughly 50 minutes per orbit
B. About 800 km altitude, taking roughly 100 minutes per orbit
C. About 1200 km altitude, taking roughly 150 minutes per orbit
D. About 600 km altitude, taking roughly 75 minutes per orbit
Show Answer & Explanation

Answer: (B) About 800 km altitude, taking roughly 100 minutes per orbit

Explanation:
The chapter explicitly states that most artificial satellites orbit about 800 km above Earth's surface and take roughly 100 minutes to complete one orbit.

Question: When the Moon takes approximately 50 minutes longer to return to the same position in the sky on successive days, what is the underlying astronomical cause?
A. The Moon's orbit is gradually expanding over time
B. While Earth rotates once in 24 hours, the Moon moves ahead in its orbit, requiring extra rotation time before the Moon appears in the same spot
C. The Moon's rotation period is longer than its revolution period around Earth
D. The Sun's gravitational pull slows Earth's rotation each day
Show Answer & Explanation

Answer: (B) While Earth rotates once in 24 hours, the Moon moves ahead in its orbit, requiring extra rotation time before the Moon appears in the same spot

Explanation:
• The Moon moves forward in its orbit as Earth completes one 24-hour rotation
• Earth must rotate additional time for the Moon to appear at nearly the same position
• This delay accumulates to about 50 minutes daily as shown in Fig. 11.6.

Question: Which of the following best explains why the entire illuminated portion of the Moon cannot be seen from Earth on certain days during its monthly cycle?
A. The Moon's illuminated half always faces toward the Sun, not always toward Earth
B. Dust and gases in space block our view of certain Moon phases
C. The Moon rotates on its axis faster than it revolves around Earth
D. Earth's atmosphere scatters moonlight during certain phases
Show Answer & Explanation

Answer: (A) The Moon's illuminated half always faces toward the Sun, not always toward Earth

Explanation:
The Moon's shape itself does not change; only what we see changes because the portion of the illuminated side facing Earth varies as the Moon orbits. Sometimes only part of the illuminated half points toward us, resulting in phases like crescents and gibbous shapes.

Question: The Indian National Calendar begins on 22 March, which marks a significant astronomical event. What is that event, and how does it relate to seasonal cycles?
A. The date of the summer solstice when days are longest
B. The day after the spring equinox, aligning the calendar year with the start of seasonal cycles
C. The winter solstice when Earth is closest to the Sun
D. The autumnal equinox marking the transition to harvest season
Show Answer & Explanation

Answer: (B) The day after the spring equinox, aligning the calendar year with the start of seasonal cycles

Explanation:
The Indian National Calendar year starts on 22 March, the day after the spring equinox, ensuring the calendar remains synchronized with the seasonal cycles tied to Earth's revolution around the Sun.

Question: In Activity 11.3, students marked the shortest shadow of a stick throughout the day. Why is the time when the shadow is shortest significant for measuring a solar day?
A. The shortest shadow occurs when Earth is closest to the Sun
B. The shortest shadow indicates when the Sun reaches its highest point in the sky, marking solar noon and allowing measurement of the mean solar day
C. The shortest shadow reveals the magnetic north direction needed for accurate timekeeping
D. The shortest shadow only occurs on certain days of the year when the season changes
Show Answer & Explanation

Answer: (B) The shortest shadow indicates when the Sun reaches its highest point in the sky, marking solar noon and allowing measurement of the mean solar day

Explanation:
The shortest shadow indicates the Sun's highest position in the sky. The time between successive highest positions on consecutive days equals one mean solar day, or approximately 24 hours.

Question: How does the relative positioning of the Sun, Moon, and Earth account for why new Moon days and full Moon days represent opposite points in the lunar cycle?
A. On new Moon day the entire Moon is illuminated; on full Moon day it is completely dark
B. On new Moon day the Moon is between Earth and Sun so only its non-illuminated side faces us; on full Moon day Earth is between the Moon and Sun so we see the entire illuminated side
C. The Moon's rotation slows dramatically on new Moon days, causing it to appear invisible
D. On full Moon day the Moon moves into Earth's shadow, blocking all reflected sunlight
Show Answer & Explanation

Answer: (B) On new Moon day the Moon is between Earth and Sun so only its non-illuminated side faces us; on full Moon day Earth is between the Moon and Sun so we see the entire illuminated side

Explanation:
Geometric position determines visibility. When the Moon lies between Earth and the Sun (new Moon), Earth faces the non-illuminated half. When Earth lies between the Moon and Sun (full Moon), Earth faces the fully illuminated half, making it a visible full circle.

Question: What is the fundamental limitation of purely lunar calendars in agricultural societies, and why does this limitation matter?
A. Lunar calendars do not account for seasonal changes because the lunar year of 354 days is shorter than the solar year of approximately 365 days, causing seasons to drift through different months across successive years
B. Lunar calendars make months too long, adding extra days that confuse planting schedules
C. Lunar calendars ignore the phases of the Moon entirely, making them unreliable
D. Purely lunar calendars require more calculations than solar calendars, making them impractical
Show Answer & Explanation

Answer: (A) Lunar calendars do not account for seasonal changes because the lunar year of 354 days is shorter than the solar year of approximately 365 days, causing seasons to drift through different months across successive years

Explanation:
An 11-day shortfall annually between the lunar year (354 days) and the solar year (365 days) causes the same lunar month to correspond to different seasons from year to year—a critical problem for societies depending on seasonal agriculture.

Question: According to the chapter, which of the following statements correctly describes how luni-solar calendars maintain synchronization with both the Moon's phases and Earth's seasons?
A. They add an extra week every month to align with both cycles
B. Every 2 to 3 years they insert an intercalary month called Adhika Maasa to correct the accumulated difference between lunar and solar years
C. They eliminate lunar months entirely and follow only solar positions
D. They adjust the length of each day to be slightly longer during certain months
Show Answer & Explanation

Answer: (B) Every 2 to 3 years they insert an intercalary month called Adhika Maasa to correct the accumulated difference between lunar and solar years

Explanation:
Luni-solar calendars solve the synchronization problem by inserting an extra month (intercalary or Adhika Maasa) every few years when the accumulated difference approaches a full month, keeping both cycles aligned.

Question: Meghnad Saha, mentioned in the chapter as chairperson of the Calendar Reform Committee, is also famous for developing an important scientific equation. What field of study does this equation relate to?
A. The physics of planetary motion around the Sun
B. Astrophysics, specifically the relationship between stars' temperatures and their properties
C. The mathematical prediction of eclipse dates
D. The calculation of tidal forces exerted by the Moon on Earth's oceans
Show Answer & Explanation

Answer: (B) Astrophysics, specifically the relationship between stars' temperatures and their properties

Explanation:
The chapter identifies Meghnad Saha as a pioneering astrophysicist who developed the famous Saha equation, which relates to the temperatures of stars and their physical properties.

Question: Certain Indian festivals such as Makar Sankranti and Pongal follow a solar sidereal calendar rather than lunar or luni-solar calendars. Over many centuries, what astronomical change would cause the dates of these festivals to shift within the tropical year?
A. The Moon gradually moves away from Earth, altering the lunar cycle length
B. A slow wobble of Earth's axis, similar to a spinning top, causes the sidereal and tropical years to differ gradually, shifting festival dates by one day every 71 years
C. The Sun's distance from Earth increases each century, changing the length of a solar year
D. The tilt of Earth's rotation axis relative to its orbital plane is decreasing
Show Answer & Explanation

Answer: (B) A slow wobble of Earth's axis, similar to a spinning top, causes the sidereal and tropical years to differ gradually, shifting festival dates by one day every 71 years

Explanation:
The chapter explains that a slow wobble of Earth's axis (precession), like that of a wobbling top, causes festivals tied to the sidereal calendar to move ahead relative to the tropical calendar—Makar Sankranti, for instance, shifts by one day every 71 years.

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