NCERT Solutions for Class 8 Science Chapter 11 - Keeping Time with the Skies

Picture yourself waking up to the sun and seeing the time on the clock perfectly, without even checking the clock or even just guessing it out: that is the beauty of Class 8 Science Chapter 11: Keeping Time with the Skies. This chapter discusses the manner in which the movement of celestial bodies such as the Sun, the Moon and the Earth assists man in determining and forecasting time. Students will come to know about the rotation and revolution of the Earth and the phases of the moon, and the effects of these natural cycles on certain phenomena in the world, such as changing seasons and the dates of festivals.

This Story also Contains

1. NCERT Solutions For Class 8 Science Chapter 11 - PDF Download
2. NCERT Solutions for Class 8 Science Chapter 11: Solved Exercise Questions
3. Keeping Time with the Skies Class 8 Science Chapter 11: Topics
4. NCERT Class 8 Science Chapter 11 – Keeping Time with the Skies – Overview
5. Approach to Solve Questions of Class 8 Science Chapter 11 Solutions
6. NCERT Solutions for Class 8 Science: Chapter-wise

The NCERT Solutions to Keeping Time with the Skies includes a step-wise explanation of the important concepts like lunar calendar, solar calendar, and the difference in these methods, as well as the science of keeping time. Conceptualised, designed, and developed by subject experts and as per the current NCERT syllabus, these NCERT solutions for Class 8 Science provide clear diagrams, real-life illustrations, and easy-to-learn language to ensure learning without any hassle. By having these solutions in PDF, students are able to improve on their knowledge, revise and even master the subject in the examination.

NCERT Solutions For Class 8 Science Chapter 11 - PDF Download

The NCERT Solutions of Class 8 Science Chapter 11 are direct and explicit responses to all the text book questions of Keeping Time with the Skies. These solutions to NCERT are designed in PDF format based on the current NCERT syllabus and make concepts such as the rotation and revolution of the Earth, lunar phases and calendars, much easier to learn and master which allows the student to revise in a quick manner and hence score well in the exams..

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NCERT Solutions for Class 8 Science Chapter 11: Solved Exercise Questions

NCERT Solutions for Class 8 Science Chapter 11 - Solved Exercise Questions are step by step explanations to all the end of chapter questions in Keeping Time with the Skies. These answers simplify the study of some of the major principles like motion of celestial bodies, Moon phases and functioning of various calendars by the student. These have been designed by professionals according to the new syllabus and are a very useful means of practice, revision and shaping a firm conceptual framework.

Question 1: State whether the following statements are True or False.

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

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

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

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

Answer:

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

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

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

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

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

Answer: No, Amol’s birthday will not fall on the full moon day every year. This is because the Moon follows a different cycle, which is known as the lunar cycle. And this lunar cycle does not match our calendar months. So, the date of the full moon changes every year.

Question 3: Name two things that are incorrect in the figure given below.

Answer: The two things that are incorrect in the figure are:

• Stars are shown near the moon, which is wrong. Stars are only visible at night.

• The shadow present on the moon is shown in the wrong direction.

Question 4: Look at the pictures of the Moon in the figure given below, and answer the following questions.

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

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

Answer:

(i)

(ii) B is the picture label of the moon phase, which is never seen from the Earth as the moon is not illuminated during that phase.

Question 5: Malini saw the Moon overhead in the sky at sunset.

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

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

Answer:

(i) If Malini saw the moon overhead in the sky at sunset, this means it is the full moon phase.

(ii) At this time, the Moon is in the waxing phase and is about to reach the full Moon. The full Moon is making the transition from waxing to waning.

Question 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?

Answer: Ravi said he saw a crescent moon rising in the east at sunset, but this is not possible because a crescent moon is seen in the early morning or after sunset. On the other hand, Kaushalya said she saw a gibbous moon during the afternoon in the east. This is possible because a waxing gibbous Moon rises in the afternoon and is often visible before sunset.

So, Kaushalya is telling the truth, and Ravi is not.

Question 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?

Answer: Scientific studies show that the moon is getting farther away from the Earth and slower in its revolution. Because of this, each lunar month will become a little longer.

Luni-solar calendars are different kinds of calendars that use the moon’s phases for counting days and months. The 12 lunar months add up to 354 days and thus fall short by around 11 days compared to the solar year. Thus, every 2–3 years, the difference becomes close to a full month. But since the lunar month is getting longer, some of them get adjusted in the year. So, an intercalary month will be needed less often.

Question 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.

Answer: In three years, if we calculate the total months would be 36. But as it is mentioned in the question, the total number of full moons in 3 years is 37, then it means one month will have 2 full moons. This occurs because the number of full moons is more than the number of months.

Question 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?

Answer: If Vaishali saw the moon in the sky from sunset to sunrise, then it is the full moon phase. It is because the full moon rises at sunset, then remains visible all night, and sets as sunrise.

Question 10: If we stopped having leap years, in approximately how many years would the Indian Independence Day happen in winter?

Answer: If we stop having leap years, the calendar will slowly shift. After around 500-600 years, 15th August, which is Independence Day, will fall in winter. This happens because the calendar will not match the real and actual movement of the Earth around the Sun.

Question 11: What is the purpose of launching artificial satellites?

Answer: The main purpose of launching artificial satellites is they help us in many ways, like communication, navigation, weather monitoring, disaster management, and scientific research as well.

Question 12: On which periodic phenomenon are the following measures of time based: (i) day, (ii) month, (iii) year?

Answer:

(i) Day - Based on the rotation of the Earth on its axis

(ii) Month - Based on the revolution of the Moon around the Earth

(iii) Year - Based on the revolution of the Earth around the Sun

Also, check the NCERT Books and the NCERT Syllabus here

• NCERT Books Class 8 Science

• NCERT Syllabus Class 8 Science

• NCERT Books Class 8

• NCERT Syllabus Class 8

Keeping Time with the Skies Class 8 Science Chapter 11: Topics

Keeping Time with the Skies - Class 8 Science Chapter 11 discusses and explains how we use the movements of the celestial bodies in order to close time and keep time. It discusses the principle of rotation and revolution of the Earth, lunar phases, and various calendars, as well as connecting astronomy to our own day-to-day and cultural clocks.

11.1 How does the Moon’s appearance change, and why?

The Moon seems to alter its shape due to the reflection of sunlight on the Moon's surface as it rotates around the Earth. The changes occur periodically and in a predictable cycle.

11.1.1 Phases of the Moon

The phases (New Moon, Crescent, First Quarter and establish, and Full Moon ) come about as a result of the relative movements of the sun, Earth and the Moon. These stages are repeated at a period that is approximately 29.5 days, called the lunar month.

11.1.2 Locating the Moon

The Moon takes different positions in the sky during daytime and night. The observation of its appearance, disappearance, and appearance at various times and at different points in the sky will enable us to understand something of the motion of this double star and its relation to the rotation of the earth.

11.1.3 Making sense of our observations

By observing and keeping a record of daily observations, we can observe the kinds of patterns in the Moon’s journey and appearance. This is why there is a connection between its phases and its location in the sky.

11.2 How Did Calendars Come into Existence?

The calendars were built to observe days, months and years following astronomical phenomena such as the phases of the Moon and, motion of Earth around the Sun.

11.2.1 Lunar calendars

These depend on the cycles of phases of the Moon, and months commonly are either 29 or 30 days.

11.2.2 Solar calendars

Solar calendars measure the Earth’s revolution about the Sun, which gives a year the duration of 365 days. The Gregorian calendar, which is widely used currently, is a solar calendar.

11.2.3 Luni-solar calendars

These are made to merge lunar months and solar years, which change with the leap months to keep in line with seasons. Examples are the Hindu and Chinese calendars.

11.2.4 The Indian National Calendar

Also known as the Saka Calendar, it is a luni-solar calendar in official use in India, along with the Gregorian calendar, synchronizing festivals and agricultural cycles with astronomy.

11.3 Are Festivals Related to Astronomical Phenomena?

There are, indeed, a great number of such festivals connected, either with the lunar phases, or with the relative positions of the sun. As an example, Diwali is frequently celebrated on a new moon day, and Makar Sankranti is a festival to celebrate the sun entering Capricorn.

11.4 Why Do We Launch Artificial Satellites in Space?

Satellites is launched for communication, weather prediction, navigation along with the scientific research. They are also useful in study of celestial bodies and for space exploration and providing us with more accurate information about celestial body and timekeeping.

NCERT Class 8 Science Chapter 11 – Keeping Time with the Skies – Overview

This chapter presents you with an interesting historical trip through the ability of man over the past millennia to measure time, coordinate movements, and mark special occasions. It starts by describing the varying face of the Moon and the way the Moon's phases allowed early humans to count days and months in ancient societies. You will delve into how the various forms of calendars, namely lunar, solar, and luni-solar ones, were created and how the Indian National Calendar was meant to introduce homogeneity in the way time was measured countrywide.

The chapter also emphasises the heavy interconnection between astronomical events and festivals, illustrating how, despite the overall fact that cultural norms tend to be saturated in cosmic events. In the contemporary world, it describes how artificial satellites are used to measure precise time, navigation and communication. The chapter offers a great mix of historical and scientific explanations that bridge the two ends of the sky watching tradition to modern space technology and is, therefore, a vital component of the history as well as our current way of time keeping.

Approach to Solve Questions of Class 8 Science Chapter 11 Solutions

Students can follow the steps given below to answer the questions effectively. Keeping Time with the Skies questions and answers helps students understand a lot about the sun, the moon, and the Earth. These answers allow students to improve their thinking skills and help them relate science to everyday life.

• Students can start by understanding how the sun, the moon, and the Earth help us measure time.

• They can learn about different phases of the Moon and how its form changes regularly. Students can take help from the NCERT Solutions for Class 8 Science Chapter 11 Keeping Time with the Skies.

• Students are advised to prepare flow charts and learn the phases with the diagrams. This makes it easy to remember the phases during exams.

• Learn about different types of calendars, such as solar, lunar, luni-solar, Indian national calendar, etc. They are all included in the Science NCERT Class 8 PDF Solutions.

• Solve and practice different forms of questions from the NCERT Solutions for Class 8 Science to get familiar with the question pattern.

NCERT Solutions For Class 8th: Subject-wise

• NCERT Solutions for Class 8 Maths

NCERT Solutions for Class 8 Science: Chapter-wise

NCERT Solutions for Class 8 Science: Chapter-wise Links provide easy access to well-structured answers for every chapter in the syllabus. These solutions are prepared by subject experts, ensuring clarity, accuracy, and alignment with the latest NCERT guidelines. They help students strengthen concepts, improve problem-solving skills, and prepare effectively for exams.