Questions: Keeping time with the skies

Q1. Why does the Moon appear different on different days?

Answer (English): The Moon shines by reflecting sunlight, and half of it is always illuminated by the Sun. While the Moon travels around the Earth, the half turned our way is not always the lit half. We can see only the illuminated part that faces us, so the visible bright region changes from day to day and produces the phases.

Hinglish: Moon suraj ki roshni reflect karta hai, aur uska aadha hissa hamesha Sun se lit hota hai. Moon Earth ke chaaron taraf ghoomta hai, isliye Earth ki taraf wala aadha hissa hamesha lit nahi hota. Hum sirf wahi lit hissa dekh sakte hain jo hamari taraf hota hai, isliye dikhne wala bright portion har din badalta hai aur phases bante hain.

Q2. Distinguish between the waning and waxing periods of the Moon.

Answer (English): The waning period begins after the full Moon, when the lit area shrinks from full to half and then vanishes across about two weeks. The waxing period begins after the new Moon, when the bright part grows from nothing to a half circle and then to a full circle in about two weeks. In India the waning period is called Krishna Paksha and the waxing period Shukla Paksha.

Hinglish: Waning period full Moon ke baad shuru hoti hai, jab bright part do hafton mein full circle se aadha aur phir gayab ho jaata hai. Waxing period new Moon ke baad shuru hoti hai, jab bright part do hafton mein badhkar aadha aur phir poora circle ban jaata hai. India mein waning ko Krishna Paksha aur waxing ko Shukla Paksha kehte hain.

Q3. Why can the Moon be seen during the day, and how does its position change with the phase?

Answer (English): The Moon can be seen during the day when it is above the horizon while the Sun is up, for example in the afternoon or morning sky. Its position depends on the phase. Look for a waxing Moon after sunset and a waning Moon around sunrise. A waxing Moon is closer to the Sun in the sky than at full Moon and can appear in the daytime sky. Moonrise shifts by about 50 minutes daily, so its position at the same clock time keeps changing.

Hinglish: Moon din mein tab dikhta hai jab Sun upar ho aur Moon bhi horizon ke upar ho, jaise dopahar ya subah. Uska position phase par depend karta hai. Waxing Moon sunset par aur waning Moon sunrise par sabse aasani se dikhta hai. Waxing Moon full Moon ke muqable Sun ke paas hota hai, isliye din mein bhi dikh sakta hai. Moon har din kareeb 50 minute late ugta hai, isliye same time par uska position badalta rehta hai.

Q4. How does the ball-and-torch activity explain the phases of the Moon?

Answer (English): The torch represents the Sun, the ball represents the Moon and the head represents the Earth. When the ball is held opposite the torch, its entire lit side faces the observer, just like a full Moon. When the ball is held towards the torch, the dark side faces the observer, like a new Moon. At intermediate positions the boundary between lit and dark parts appears curved, producing the crescent, half and gibbous shapes. The change in the visible lit portion causes the phases.

Hinglish: Activity mein torch Sun, ball Moon aur sir Earth ko dikhata hai. Ball ko torch ke saamne rakho to uski poori lit side dikhti hai, jaise full Moon. Ball ko torch ki taraf rakho to dark side dikhti hai, jaise new Moon. Beech ki positions par lit aur dark hisson ke beech ki line curved dikhti hai, jisse crescent, half aur gibbous shapes bante hain. Visible lit portion badalne se phases bante hain.

Q5. Why are the phases of the Moon not caused by the Earth's shadow?

Answer (English): The phases happen because the Moon revolves around the Earth and we see different portions of its sunlit half. The Earth's shadow on the Moon produces a lunar eclipse instead. A lunar eclipse can happen only on a full Moon day, and a solar eclipse only on a new Moon day. These eclipses do not occur every month because the Moon's orbital plane is tilted a little relative to the plane of Earth's orbit around the Sun.

Hinglish: Phases isliye hote hain kyunki Moon Earth ke chaaron taraf ghoomta hai aur hum uske sunlit half ka alag-alag hissa dekhte hain. Earth ki shadow Moon par lunar eclipse banati hai. Lunar eclipse sirf full Moon day par aur solar eclipse sirf new Moon day par ho sakta hai. Ye eclipses har mahine nahi hote kyunki Moon ki orbit Earth ki Sun ke chaaron taraf wali orbit se thodi tilted hai.

Q6. What periodic phenomenon gives the day, the month and the year?

Answer (English): The day is based on the Earth's rotation on its axis, which makes the Sun appear to move across the sky; the mean solar day is 24 hours. The month is based on the Moon's cycle of phases, which takes about 29.5 days. The year follows Earth's journey around the Sun and its seasonal cycle, lasting about 365 and a quarter days.

Hinglish: Day Earth ke apni axis par rotation par based hai, jisse Sun aasman mein chalta dikhta hai; mean solar day 24 hours ki hoti hai. Month Moon ke phases ke cycle par based hai, jo kareeb 29.5 din leta hai. Year Earth ke Sun ke chaaron taraf revolution aur seasons ke cycle par based hai, jo kareeb 365 aur sava din leta hai.

Q7. Compare lunar, solar and luni-solar calendars.

Answer (English): A lunar calendar counts months by the Moon's phases, so 12 lunar months add up to about 354 days and drift against the seasons. A solar calendar follows the seasons, with months adjusted to total 365 days and leap years correcting the extra quarter day. A luni-solar calendar counts months by the Moon but adds an extra month, Adhika Maasa, every two or three years to stay in step with the seasons.

Hinglish: Lunar calendar mein months Moon ke phases se bante hain, isliye 12 lunar months kareeb 354 din hote hain aur seasons ke against drift karte hain. Solar calendar seasons follow karta hai; months 365 din ke adjusted hote hain aur leap year extra quarter day correct karta hai. Luni-solar calendar mein months Moon se bante hain, par har 2-3 saal mein Adhika Maasa jodta hai taaki seasons ke saath rahe.

Q8. What are the main features of the Indian National Calendar?

Answer (English): The Indian National Calendar is a solar calendar of 365 days that begins on 22 March, the day after the spring equinox. Its months have 30 or 31 days and use names from traditional Indian calendars. In leap years a day is inserted into Chaitra, which moves the new year to 21 March. The Calendar Reform Committee of 1952 recommended it, and it was adopted from 21 March 1956.

Hinglish: Indian National Calendar ek solar calendar hai jo 365 din ka hota hai aur 22 March se shuru hota hai, spring equinox ke agle din. Iske months 30 ya 31 din ke hote hain aur naam traditional Indian calendars se liye gaye hain. Leap year ko Gregorian se match karne ke liye Chaitra mein ek din jodta hai, isliye aise saal mein naya saal 21 March se shuru hota hai. 1952 ki Calendar Reform Committee ne iski sifarish ki thi aur 21 March 1956 se ise apnaya gaya.

Q9. Why do some festivals change dates every year while others stay nearly fixed?

Answer (English): Festivals based on the Moon's phases change dates because the lunar month does not match the Gregorian year. Purely lunar festivals such as Eid-ul-Fitr move earlier by about 11 days each year, while luni-solar festivals shift less than a month because of the extra month added every few years. Solar sidereal festivals such as Makar Sankranti and Pongal follow the Sun and fall on almost the same Gregorian date each year.

Hinglish: Moon ke phases par based festivals ki dates badalti hain kyunki lunar month Gregorian saal se match nahi karta. Purely lunar festivals jaise Eid-ul-Fitr har saal kareeb 11 din pehle ho jaate hain, jabki luni-solar festivals ek mahine se kam shift hote hain kyunki har kuch saal mein extra month jodta hai. Solar sidereal festivals jaise Makar Sankranti aur Pongal Sun ko follow karte hain aur lagbhag same Gregorian date par aate hain.

Q10. What are artificial satellites used for? Name two ISRO missions and one problem caused by satellites.

Answer (English): Artificial satellites are used for weather watching, communication, navigation, disaster response and scientific research. The Cartosat series maps the Earth, and AstroSat studies stars and other celestial objects; Chandrayaan went to the Moon, Mangalyaan to Mars and Aditya L1 studies the Sun. After their useful life, satellites and rocket parts become space debris, which can collide with working satellites.

Hinglish: Artificial satellites communication, navigation, weather monitoring, disaster management aur scientific research ke liye use hote hain. Cartosat Earth ka mapping karta hai aur AstroSat stars aur doosre celestial objects study karta hai; India ne Chandrayaan missions Moon ke liye, Aditya L1 Sun ke liye aur Mangalyaan Mars ke liye bheje. Useful life ke baad satellites aur rocket parts space debris ban jaate hain, jo working satellites se takra sakte hain.

The quick check below has five multiple choice questions on the Moon's phases, calendars and satellites. Each one comes with a short explanation, so take the quiz and see which topics need another read.