Chapter 11 Solutions — Keeping Time with the Skies

Keep the Curiosity Alive

1. 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.
2. 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.
3. 3.
   Name two things that are incorrect in Fig. 11.10. [Fig. 11.10 shows a Moon surrounded by clouds, with stars drawn on the dark face of the Moon.]
4. 4.
   Look at the pictures of the Moon in Fig. 11.11 (panels A, B, C, D, E, F), and answer the following questions.

   • (i) Write the correct panel number corresponding to the phases of the Moon shown in the pictures above. Phase of Moon | Picture label Three days after New Moon | ? Full Moon | ? Three days after Full Moon | ? A week after Full Moon | ? Day of New Moon | ?
   • (ii) List the picture labels of…
5. 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?
6. 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?
7. 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?
8. 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.
9. 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?
10. 10.
    If we stopped having leap years, in approximately how many years would the Indian Independence day happen in winter?
11. 11.
    What is the purpose of launching artificial satellites?
12. 12.
    On which periodic phenomenon are the following measures of time based:

    • (i) day
    • (ii) month
    • (iii) year?