Din, Mahina aur Saal (Aasmaan ki Teen Ghadiyaan)
Ghadi aur calendar se pehle log samay kaise naapte the? Ek lakdi, uski parchhai, Chand aur mausam: yahi thi asli ghadi! ☀️🌙📅
🧭 Is Post Mein
📖 Kahani: Dadi ki “Parchhai Wali Ghadi”
Diwali ki chhuttiyon mein Golu, Priya aur Rohan gaon mein Golu ki Dadi ke paas aaye the. Dopahar ko Rohan ne poochha, “Dadi, khaana kab banega? Mera phone toh discharge ho gaya, time hi nahi pata!”
Dadi muskurayi aur aangan mein gade baans ke khambe ki taraf ishaara kiya. “Jab is khambe ki parchhai sabse chhoti ho jaaye, samjho dopahar ho gayi. Hum bachpan mein isi se time dekhte the.”
Priya ko maza aa gaya. Usne chalk li aur har thodi der mein parchhai ki nok par ek bindu lagaane lagi. Golu bola, “Par Dadi, din 24 ghante ka hi kyun hai? Mahina 30 din ka kyun? Aur saal 365 din ka kisne banaya?”
Dadi ne aasmaan ki taraf dekha, “Kisi ne banaya nahi beta. Sooraj, Chand aur mausam khud bata dete hain. Bas dekhna aana chahiye.”
Teen sawaal: Ek “din” ko theek-theek kaise naapein? Mahina aur saal kahan se aaye? Aur ek seedhi lakdi humein samay ke baare mein kya-kya bata sakti hai? Chaliye, aasmaan ki teen ghadiyaan padhna seekhte hain! ⏳
🎯 Is Post Mein Kya Seekhenge
- Periodic (baar-baar ek niyamit samay par hone wali) ghatnaayein kya hain
- Din: Dharti ke apni dhuri par ghoomne (rotation) se; solar day aur mean solar day (24 ghante)
- Parchhai sabse chhoti kab hoti hai, aur usse din kaise naapte hain (NCERT ki shadow-stick activity)
- Mahina: Chand ke phases ka chakra (~29.5 din)
- Saal: Dharti ka Sooraj ke chaaron taraf ek chakkar (~365¼ din) aur mausam ka chakra
- Bonus: Dharti asal mein 23 ghante 56 minute mein kyun ghoom jaati hai, phir bhi din 24 ghante ka kyun hai
🧱 Basics: Pehle Yeh Aana Chahiye
1. Rotation (ghoornan): kisi cheez ka apni dhuri (axis) par lattoo ki tarah ghoomna. Dharti pashchim se poorab (west → east) ki taraf ghoomti hai. Isliye humein Sooraj poorab mein ugta aur pashchim mein doobta dikhta hai.
2. Revolution (parikrama): kisi doosri cheez ke chaaron taraf chakkar lagana. Chand Dharti ki, aur Dharti Sooraj ki parikrama karti hai.
3. Parchhai (shadow) Sooraj ki ulti taraf banti hai. Sooraj jitna neeche (subah-shaam), parchhai utni lambi. Sooraj jitna upar, parchhai utni chhoti.
4. Pichle posts se: Chand ke phases (Amavasya → Purnima → Amavasya) lagbhag 29.5 din mein ek chakra poora karte hain (Post 1 aur 3).
5. Average (ausat): kuch sankhyaon ka jod ÷ unki ginti. Jaise 24 aur 23.98 ka average = (24 + 23.98) ÷ 2 = 23.99. Activity mein yeh kaam aayega.
💡 Concept: Prakriti ki Teen Ghadiyaan
Step 1: Periodic ghatna kya hai? Jo ghatna ek niyamit (regular) samay ke baad baar-baar hoti hai, use periodic kehte hain. Jaise: roz Sooraj ka ugna, Chand ke phases ka laut-laut kar aana, har saal garmi-barsaat-sardi ka aana. Jo cheez niyam se dohraati hai, wahi samay naapne ki ghadi ban sakti hai!
Step 2: Din kahan se aaya? Dharti apni dhuri par ghoomti hai, isliye Sooraj roz poorab se pashchim ki taraf aasmaan mein chalta dikhta hai. Ek din ka matlab hai: Sooraj ka ek jagah se chal kar wapas usi jagah aana.
Step 3: “Usi jagah” ko kaise pakdein? Sooraj ugne ka samay achha nishaan nahi hai, kyunki woh mausam ke saath roz thoda badalta hai (sardi mein der se, garmi mein jaldi). Isliye scientist ek pakka nishaan lete hain: Sooraj ka aasmaan mein sabse ooncha point, jise local noon (madhyahn) kehte hain. Us samay kisi seedhi khadi lakdi ki parchhai sabse chhoti hoti hai.
Step 4: Solar day. Ek din ki sabse chhoti parchhai se agle din ki sabse chhoti parchhai tak ka samay = ek solar day. Yeh roz bilkul barabar nahi hota (kuch second aage-peeche), isliye iska average liya jaata hai. Is average ko mean solar day kehte hain, aur yeh theek 24 ghante hai. Humari ghadiyaan isi 24 ghante wale din par chalti hain.
Step 5: Mahina kahan se aaya? Chand ke phases lagbhag 29.5 din mein dohraate hain (ek Purnima se agli Purnima). Isi chakra se “mahina” bana. Hindi ka “maas” aur English ka “month”, dono ka rishta Chand (maas/moon) se hai.
Step 6: Saal kahan se aaya? Dharti Sooraj ke chaaron taraf lagbhag 365¼ din mein ek chakkar lagaati hai. Is beech mausam ka ek poora chakra (sardi → garmi → barsaat → sardi) poora hota hai, aur dopahar mein Sooraj ki oonchai bhi ghat-badh kar wapas wahin aa jaati hai. Mausam ke is chakra se solar year (saal) bana.
Step 7: Ek dikkat! Saal = 365¼ din, mahina = 29.5 din. Yeh poore number nahi hain! Calendar mein toh poore din chahiye. Isliye 4 saal mein ek extra din (leap year) jodna padta hai, aur 12 Chand-mahine (354 din) saal se lagbhag 11 din chhote padte hain. Is “jod-tod” ki kahani agle post (Calendar) mein. 😉
Ek line mein: Din = Dharti ka apni dhuri par ghoomna (24 ghante), mahina = Chand ke phases ka chakra (~29.5 din), saal = Dharti ka Sooraj ki parikrama aur mausam ka chakra (~365¼ din).
🖼️ Diagrams: Picture se Samjho
🔐 Deep Concept: 23 Ghante 56 Minute ka Raaz
1. Dharti 1° kitni der mein ghoomti hai? Ek poora chakkar = 360°. Agar yeh 24 ghante mein ho, toh 1 ghante mein 360 ÷ 24 = 15°, yaani 1° ke liye 4 minute.
2. Sidereal day (taaron wala din). Agar hum Sooraj ki jagah kisi door ke taare ko dekhein, toh woh roz lagbhag 23 ghante 56 minute 4 second mein wapas usi jagah aa jaata hai. Yahi Dharti ka “asli” ek chakkar hai.
3. Toh solar day 4 minute lamba kyun? Jab Dharti apni dhuri par ghoom rahi hoti hai, usi beech woh Sooraj ke chaaron taraf bhi aage khisakti hai: roz lagbhag 1° (360° ÷ 365¼ din ≈ 0.99°). Isliye Sooraj ko phir se “sabse upar” laane ke liye Dharti ko lagbhag 1° extra ghoomna padta hai, yaani ~4 minute aur. 23 ghante 56 minute + ~4 minute ≈ 24 ghante.
4. Solar day roz barabar kyun nahi? Dharti ki kaksha (orbit) poori gol nahi, thodi lambi-gol (ellipse) hai, aur uski dhuri tirchhi hai. Isliye saal bhar mein “sabse chhoti parchhai” ka ghadi wala samay dheere-dheere kuch minute aage-peeche khisakta hai (saal mein lagbhag ±15 minute tak). Ek din se agle din ka farq bas kuch second ka hota hai. Isliye hum average lete hain = mean solar day = 24 ghante.
5. Har shehar ka “noon” alag. Poore Bharat ki ghadiyaan ek hi samay (IST) chalaati hain, jo 82.5° poorab (East) longitude ke hisaab se hai. Har 1° longitude = 4 minute ka farq. Isliye (saal ke dinon ka chhota farq chhod kar):
| Shehar (longitude lagbhag) | Hisaab | Sabse chhoti parchhai (lagbhag) |
|---|---|---|
| Kolkata (88.4° E) | (88.4 − 82.5) × 4 ≈ 24 min pehle | ~11:36 |
| Lucknow (81.0° E) | (82.5 − 81.0) × 4 ≈ 6 min baad | ~12:06 |
| Delhi (77.2° E) | (82.5 − 77.2) × 4 ≈ 21 min baad | ~12:21 |
| Ahmedabad (72.6° E) | (82.5 − 72.6) × 4 ≈ 40 min baad | ~12:40 |
Upar ke samay sirf longitude se nikale hain; saal ke alag dinon mein inmein ±15 minute tak ka farq aa sakta hai (point 4). Isliye activity mein apne shehar ka samay khud naapna sabse achha hai!
✏️ Examples: Hisaab Lagao
Hal: 1→2 Nov: 24:00, 2→3 Nov: 24:00, 3→4 Nov: 24:01. Average = (24:00 + 24:00 + 24:01) ÷ 3 ≈ 24 ghante (bas 20 second zyaada).
Minute wali ghadi se naapne mein ±1 minute ki galti normal hai; average lene se galti chhoti ho jaati hai.
Hal: 365.25 × 24 = 8766 ghante.
Hal: 12 × 29.5 = 354 din. 365 − 354 = 11 din kam.
Isi 11 din ke farq ki wajah se calendar banane walon ko jugaad karna pada (agla post).
Hal: 4 saal mein ¼ × 4 = 1 poora din jud jaata hai. Isliye har chauthe saal February mein 29 tareekh (leap year).
Hal: 1° = 4 minute, toh 30° = 30 × 4 = 120 minute = 2 ghante.
Hal: (a) mahina (Chand) + saal dono (b) din (Dharti ka rotation) (c) saal (mausam ka chakra).
⚖️ Difference Table: Din vs Mahina vs Saal
| Baat | Din | Mahina | Saal |
|---|---|---|---|
| Kaaran | Dharti ka apni dhuri par ghoomna (rotation) | Chand ka Dharti ke chaaron taraf ghoomna (phases) | Dharti ka Sooraj ke chaaron taraf ghoomna (revolution) |
| Lambai | 24 ghante (mean solar day) | ~29.5 din | ~365¼ din |
| Kaise pehchaanein | Sabse chhoti parchhai se agli sabse chhoti parchhai tak | Purnima se agli Purnima (ya Amavasya se Amavasya) | Mausam ka ek poora chakra; dopahar mein Sooraj ki oonchai ka ek chakra |
| Roz-marra mein | Ghadi, school-office ka samay | Tithi, Purnima/Amavasya wale tyohaar | Janamdin, kheti ke mausam, saalana exam |
🚫 Misconceptions: Log aisa sochte hain… lekin
✅ Nahi. Dharti apni dhuri par ghoomti hai; Sooraj ka chalna sirf dikhta hai, jaise chalti train se ped peeche bhaagte dikhte hain.
✅ Nahi. Local noon shehar ke longitude aur saal ke din par nirbhar hai. Ahmedabad mein yeh aksar 12:30 ke baad, Kolkata mein 12 se pehle hota hai.
✅ Nahi. Zyaadatar dinon mein dopahar ko bhi thodi parchhai banti hai. Kark rekha (Tropic of Cancer) ke dakshin wali jagahon par saal mein sirf do din (Zero Shadow Day) Sooraj theek sir ke upar aata hai.
✅ Lagbhag 365¼ din. Isi ¼ din ki wajah se leap year chahiye.
✅ Taaron ke hisaab se ~23 ghante 56 minute. 24 ghante Sooraj ke hisaab wala din hai, kyunki Dharti saath-saath Sooraj ke chaaron taraf bhi khisakti hai.
✅ Nahi. Dharti Sooraj ke sabse paas January ki shuruaat mein hoti hai, jab Bharat mein sardi hoti hai! Mausam Dharti ki tirchhi dhuri ki wajah se badalte hain.
🔤 Key Terms (Exam mein English shabd hi likhna)
❓ FAQs
Q1. Din naapne ke liye Sooraj ugne ka samay kyun nahi lete?
Kyunki sunrise ka samay mausam ke saath roz badalta hai (October-November mein roz lagbhag ek minute der se), aur pahaad, ped ya dhundh se ugta Sooraj theek se dikhta bhi nahi. Sabse chhoti parchhai (local noon) ka samay din-ba-din lagbhag same rehta hai, isliye woh behtar nishaan hai.
Q2. 24 ghante kisne tay kiye?
Din ko 24 hisson mein baantne ka tareeka purane zamaane ke logon (jaise Misr/Egypt) se aaya. Bharat mein pehle din ko 60 ghati (ek ghati = 24 minute) mein baanta jaata tha. 60 × 24 minute = 1440 minute = 24 ghante. Baantne ka tareeka insaan ne chuna, par “din” khud prakriti ne diya.
Q3. Calendar mein mahine 28 se 31 din ke kyun, 29.5 ke kyun nahi?
Aaj ka (Gregorian) calendar Sooraj par aadharit hai. Usmein 365 din ko 12 hisson mein baanta gaya hai, isliye mahine 30-31 din ke (February 28/29). Chand wale calendar mein mahine 29 ya 30 din ke hote hain. Agle post mein vistaar se.
Q4. Kya din hamesha se 24 ghante ka tha?
Nahi! Samudra ke jwaar (tides) ki wajah se Dharti ka ghoomna bahut-bahut dheere slow ho raha hai. Karodon saal pehle din kuch ghante chhota tha. Par humari zindagi mein yeh farq naapne layak nahi hai.
Q5. Agar badal ho toh activity ka kya?
Jis din badal ho, us din ko chhod do aur agle saaf din ki reading lo. Phir do saaf dinon ke beech ke dinon ki ginti se hisaab lagao, jaise 3 din ka farq ho toh kul samay ÷ 3.
🧪 Activity: Ek Lakdi se Din Naapo
Is activity mein aap ek seedhi lakdi ki parchhai se pata karoge ki ek din (solar day) kitna lamba hota hai.
Saamaan: lagbhag 1 metre lambi seedhi lakdi (ya scale/dandi), dhoop wali samtal (flat) zameen ka chhota hissa (aangan ya chhat), chalk ya chhote kankad, ghadi ya mobile ka clock, copy-pen, aur ek inch-tape.
| Tareekh | Sabse chhoti parchhai ka samay | Din ki lambai (ghante:minute) |
|---|---|---|
| Din 1 | __ : __ | — |
| Din 2 | __ : __ | __ : __ |
| Din 3 | __ : __ | __ : __ |
Kya dikhega: sabse chhoti parchhai roz lagbhag ek hi samay par banegi (ek-aadh minute aage-peeche). Isliye din ki lambai har baar lagbhag 24:00 aayegi, aur average 24 ghante ke bahut paas hoga.
Nishkarsh: Sooraj ka ek “sabse upar” se agle “sabse upar” tak ka safar lagbhag 24 ghante ka hai. Yahi solar day hai, aur iska average (mean solar day) theek 24 ghante.
Yeh activity NCERT ki Class 8 Science book Curiosity (Chapter 11) par aadharit hai, aur yahan apne shabdon mein samjhayi gayi hai.
🏠 Mini Experiments (Ghar pe)
Ek poora ghoomna = ek din. Torch hili hi nahi, phir bhi bindi ke liye “Sooraj uga aur dooba”!
Raat ko ek chamakta taara chuno jo kisi pakki cheez (padosi ki chhat ka kona, paani ki tanki) ke peeche chhipta ho. Har raat ek hi jagah se khade hokar note karo ki woh kitne baje chhipta hai. 5–7 raat baad dekho: woh roz lagbhag 4 minute pehle chhipega. Yahi sidereal day (23 ghante 56 minute) ka saboot hai! (Chamakta “taara” kabhi-kabhi grah hota hai jo taaron ke beech khisakta hai, isliye do-teen taaron par try karo.)
Mobile ke weather app ya akhbaar se ek hafte tak roz ka sunrise aur sunset ka samay likho. Dekho: November mein sunrise roz thoda der se, sunset thoda jaldi. Phir bhi dono ka beech (local noon) lagbhag same rehta hai! Isiliye din naapne ke liye noon behtar hai, sunrise nahi.
🧠 Think Like a Scientist
Sawaal: Golu kehta hai, “Sabse chhoti parchhai hamesha ek hi samay par banti hogi, saal bhar.” Kya yeh sach hai?
Scientist ka tareeka dekho
1. Observe (dekho): Lagaataar 4–5 din mein sabse chhoti parchhai ka samay lagbhag same aaya.
2. Guess (anumaan): Golu ka anumaan: saal bhar yahi samay rahega.
3. Test (jaanch): Har Ravivaar usi lakdi se 3 mahine tak sabse chhoti parchhai ka samay naapo.
4. Result: Hafte-dar-hafte samay dheere-dheere kuch minute khisakta hai (jaise November se February ke beech kaafi minute aage chala jaata hai), jabki ek din se agle din ka farq bas kuch second ka.
5. Conclusion: Solar day bilkul barabar nahi hai, thoda ghat-ta badhta hai. Isliye scientist iska average (mean solar day = 24 ghante) lete hain. Golu ka anumaan “lagbhag” sahi tha, “bilkul” nahi. Aur yahi science hai: lambe samay tak naapo, tab poori kahani dikhti hai! 🔬
🌍 Real Life Mein Din, Mahina aur Saal
- 🕰️ Jantar Mantar ki dhoop-ghadi: Jaipur ke Jantar Mantar mein “Samrat Yantra” naam ki bahut badi dhoop-ghadi (sundial) hai, jo parchhai se local samay kuch second tak sahi batati hai. Yeh activity wali lakdi ka hi bada roop hai!
- ⏰ IST: Poore desh ki ghadiyaan Indian Standard Time par chalti hain (82.5° E ke hisaab se), taaki train, school, TV sab ek hi samay maanein, chahe har shehar ka local noon alag ho.
- 🌾 Kheti: Kisan kharif (barsaat) aur rabi (sardi) fasalein mausam ke chakra, yaani saal ke hisaab se boate hain.
- ☀️ Zero Shadow Day: Bengaluru, Chennai, Hyderabad jaise shehron mein saal mein do din (April-May aur July-August ke aas-paas) dopahar ko Sooraj theek sir ke upar aata hai aur seedhi cheezon ki parchhai lagbhag gayab ho jaati hai.
- 📱 Mobile ka time: Aapke phone ka samay network aur satellites ki bahut sateek ghadiyon (atomic clocks) se set hota hai, par hum use phir bhi Dharti ke din wale ghante-minute mein hi padhte hain.
🔁 Recap: Poora Post Ek Nazar Mein
- Niyamit samay par dohraane wali ghatnaayein = periodic phenomena; inse samay naapte hain.
- Din: Dharti ka rotation. Sooraj ka sabse ooncha point = local noon = sabse chhoti parchhai.
- Ek local noon se agle tak = solar day; iska average = mean solar day = 24 ghante.
- Mahina: Chand ke phases ka chakra ≈ 29.5 din.
- Saal: Dharti ki Sooraj ke chaaron taraf parikrama, mausam ka chakra ≈ 365¼ din.
- 12 × 29.5 = 354 din: saal se ~11 din kam. ¼ din × 4 = 1 din → leap year.
- Taaron ke hisaab se Dharti ~23 h 56 min mein ghoomti hai; roz ~1° extra (~4 min) ghoomne se solar day 24 h.
- 1° longitude = 4 minute; isliye har shehar ka local noon alag.
✍️ Fill in the Blanks
- Jo ghatna niyamit antaraal par baar-baar hoti hai, use ______ ghatna kehte hain.
- Din aur raat Dharti ke apni dhuri par ______ ki wajah se hote hain.
- Jab Sooraj aasmaan mein sabse upar hota hai, tab seedhi lakdi ki parchhai sabse ______ hoti hai.
- Mean solar day ______ ghante ka hota hai.
- Chand ke phases ka ek chakra lagbhag ______ din ka hota hai.
- Dharti Sooraj ki ek parikrama lagbhag ______ din mein poori karti hai.
Answers
1) periodic · 2) rotation (ghoornan) · 3) chhoti · 4) 24 · 5) 29.5 · 6) 365¼ (365.25)
✅ True / False
- Sunrise ka samay saal bhar roz ek jaisa rehta hai.
- Solar day ka average 24 ghante hai.
- Saal Chand ke phases se tay hota hai.
- Taaron ke hisaab se Dharti ka ek chakkar 24 ghante se thoda kam hai.
- Bharat ke har shehar mein sabse chhoti parchhai ek hi ghadi-samay par banti hai.
- Leap year ki zaroorat isliye padti hai kyunki saal lagbhag 365¼ din ka hai.
Answers (kyun ke saath)
1) False: sunrise mausam ke saath roz badalta hai; isliye din naapne ke liye local noon lete hain.
2) True: isi average ko mean solar day kehte hain.
3) False: saal Dharti ki Sooraj ki parikrama aur mausam ke chakra se tay hota hai; Chand se mahina.
4) True: sidereal day ≈ 23 ghante 56 minute.
5) False: local noon longitude par nirbhar hai; har 1° = 4 minute ka farq.
6) True: ¼ din har saal bachta hai, 4 saal mein 1 din.
🔘 MCQs
Q1. Din-raat kis kaaran hote hain? (a) Sooraj ka Dharti ke chaaron taraf ghoomna (b) Dharti ka apni dhuri par ghoomna (c) Dharti ka Sooraj ke chaaron taraf ghoomna (d) Chand ka Dharti ke chaaron taraf ghoomna
✅ (b): rotation se Dharti ka ek hissa Sooraj ki taraf (din), doosra ulti taraf (raat).
(a) Sooraj Dharti ke chakkar nahi lagata; uska chalna sirf dikhta hai.
(c) isse saal banta hai.
(d) isse mahina (phases) banta hai.
Q2. Ek din naapne ke liye sabse achha nishaan kaunsa hai? (a) Sunrise (b) Sunset (c) Sabse chhoti parchhai (local noon) (d) Pehla taara dikhna
✅ (c): local noon ka samay din-ba-din lagbhag same rehta hai aur saaf naapa ja sakta hai.
(a) aur (b) mausam ke saath roz badalte hain, aur pahaad-dhundh se gadbad hoti hai.
(d) taara dikhna aasmaan ki saafi aur aankh par nirbhar hai.
Q3. Mean solar day kitne ghante ka hai? (a) 23 h 56 min (b) 24 h (c) 24 h 4 min (d) 12 h
✅ (b) 24 h: solar day ka average.
(a) yeh sidereal day (taaron wala) hai.
(c) solar day sidereal day se ~4 min lamba hai, 24 h se nahi.
(d) 12 h sirf lagbhag din ka ujaala ya ghadi ka aadha chakkar hai.
Q4. “Mahina” kis periodic ghatna se bana? (a) Mausam ka chakra (b) Chand ke phases (c) Dharti ka rotation (d) Taaron ka ugna
✅ (b): phases ~29.5 din mein dohraate hain.
(a) mausam se saal bana.
(c) rotation se din.
(d) taaron se sidereal day naapte hain, mahina nahi.
Q5. 12 Chand-mahine (har ek 29.5 din) kitne din ke? (a) 360 (b) 365 (c) 354 (d) 348
✅ (c) 354: 12 × 29.5 = 354.
(a) 30 × 12 maan liya.
(b) yeh solar saal hai.
(d) 29 × 12 maan liya.
Q6. Dharti apni dhuri par 1° ghoomne mein kitna samay leti hai (lagbhag)? (a) 1 minute (b) 4 minute (c) 15 minute (d) 1 ghanta
✅ (b) 4 minute: 24 × 60 = 1440 minute ÷ 360° = 4 minute.
(a) 1 minute mein sirf ¼°.
(c) 15 toh 1 ghante mein ghoomne wali degree hai, minute nahi.
(d) 1 ghante mein 15° ghoomti hai.
Q7. Shadow-stick activity mein lakdi ko seedha (vertical) rakhna kyun zaroori hai? (a) Sundar dikhe (b) Tirchhi lakdi se parchhai ki lambai aur sabse chhoti parchhai ka samay galat aa sakta hai (c) Parchhai rangeen ho (d) Koi zaroorat nahi
✅ (b): tirchhi lakdi se parchhai ki lambai badal jaati hai aur sabse chhoti parchhai galat samay par lag sakti hai.
(a) sundarta ka science se lena-dena nahi.
(c) parchhai ka rang nahi badalta.
(d) galat: seedhapan hi naap ko sahi rakhta hai.
Q8. Saal ke kaaran ke liye sahi jodi: (a) Rotation – 365¼ din (b) Revolution – 365¼ din (c) Revolution – 24 ghante (d) Rotation – 29.5 din
✅ (b): Dharti ki Sooraj ke chaaron taraf parikrama (revolution) ~365¼ din.
(a) rotation se din banta hai, saal nahi.
(c) 24 ghante rotation (din) ka maap hai.
(d) 29.5 din Chand ke phases ka chakra hai, Dharti ke rotation ka nahi.
🔗 Assertion–Reason
Options: (a) A aur R dono sahi, aur R, A ko samjhata hai · (b) A aur R dono sahi, par R, A ko nahi samjhata · (c) A sahi, R galat · (d) A galat, R sahi
1. A: Dopahar ko seedhi lakdi ki parchhai sabse chhoti hoti hai. R: Dopahar ko Sooraj aasmaan mein sabse upar hota hai.
✅ (a): Sooraj jitna upar, parchhai utni chhoti. R seedha A ka kaaran hai.
2. A: Solar day, sidereal day se lagbhag 4 minute lamba hai. R: Dharti apni dhuri par ghoomte hue Sooraj ke chaaron taraf roz lagbhag 1° aage badhti hai.
✅ (a): us 1° ki bharpaai ke liye Dharti ko ~4 minute extra ghoomna padta hai. R, A ko samjhata hai.
3. A: Saal Chand ke phases se tay hota hai. R: Chand ke phases lagbhag 29.5 din mein dohraate hain.
✅ (d): A galat hai, saal mausam aur Dharti ki parikrama se tay hota hai. R sahi hai (yeh mahine ka aadhaar hai).
📝 Very Short Answer (1 mark)
1. Periodic ghatna ka ek udaaharan do.
Roz Sooraj ka ugna (ya Chand ke phases, ya mausam ka chakra).
2. Local noon kise kehte hain?
Jab Sooraj aasmaan mein apne sabse oonche point par ho (parchhai sabse chhoti).
3. Ek lunar month lagbhag kitne din ka hai?
Lagbhag 29.5 din.
4. Sidereal day kitna lamba hai?
Lagbhag 23 ghante 56 minute (4 second).
5. Shadow-stick activity mein kis cheez ka samay note karte hain?
Sabse chhoti parchhai banne ka samay.
📝 Short Answer (2–3 marks)
1. Din naapne ke liye sunrise ki jagah sabse chhoti parchhai kyun behtar hai?
Sunrise ka samay mausam ke saath roz badalta hai, aur pahaad, ped ya dhundh se ugta Sooraj saaf nahi dikhta. Sabse chhoti parchhai (local noon) ka samay din-ba-din lagbhag same rehta hai aur ek lakdi se aasaani se naapa ja sakta hai.
2. Solar day aur mean solar day mein kya antar hai?
Solar day = ek local noon se agle local noon tak ka asli samay; yeh saal bhar mein kuch second ghat-ta badhta hai. Mean solar day = in sabka average = theek 24 ghante; humari ghadiyaan isi par chalti hain.
3. Din, mahina aur saal kin teen periodic ghatnaon se bane?
Din: Dharti ka apni dhuri par ghoomna (24 ghante). Mahina: Chand ke phases ka chakra (~29.5 din). Saal: Dharti ki Sooraj ke chaaron taraf parikrama aur mausam ka chakra (~365¼ din).
4. Ahmedabad mein local noon Kolkata se der se kyun hota hai?
Dharti pashchim se poorab ghoomti hai, isliye Sooraj pehle poorab wale shehron mein sabse upar aata hai. Kolkata (~88° E) Ahmedabad (~73° E) se lagbhag 16° poorab hai; 16 × 4 ≈ 64 minute, yaani Ahmedabad mein local noon lagbhag ek ghanta der se hota hai.
📝 Long Answer (5 marks)
1. Ek seedhi lakdi ki madad se solar day ki lambai kaise naapoge? Saamaan, steps, observation aur nishkarsh likho.
Saamaan: ~1 m seedhi lakdi, dhoop wali samtal zameen, chalk, ghadi, copy-pen.
Steps: (1) lakdi ko bilkul seedha gaado. (2) local noon se ~1 ghanta pehle se har minute parchhai ki nok par bindu lagao aur samay likho, ~1 ghanta baad tak. (3) paaye se sabse paas wala bindu = sabse chhoti parchhai; uska samay note karo. (4) agle kuch din usi jagah yahi dohraao. (5) lagaataar dinon ke samay ka farq + 24 ghante = din ki lambai; average nikaalo.
Observation: sabse chhoti parchhai roz lagbhag ek hi samay par; din ki lambai har baar ~24:00.
Nishkarsh: solar day ≈ 24 ghante; iska average mean solar day = 24 ghante.
Saavdhaani: Sooraj ko seedha mat dekho; lakdi hile nahi.
2. Samjhao ki taaron ke hisaab se Dharti ~23 h 56 min mein ghoomti hai, phir bhi solar day 24 ghante ka kyun hai. Diagram/udaaharan do.
Sidereal day: door ka koi taara roz ~23 h 56 min 4 s mein wapas usi jagah aata hai; yeh Dharti ka asli ek chakkar (360°) hai.
Kaaran: ghoomte-ghoomte Dharti Sooraj ke chaaron taraf bhi aage badhti hai: 360° ÷ 365¼ ≈ 1° roz. Isliye Sooraj ko phir se sabse upar laane ke liye Dharti ko ~361° ghoomna padta hai.
Hisaab: 1° ghoomne mein 4 minute (1440 min ÷ 360°). 23 h 56 min + ~4 min ≈ 24 h.
Udaaharan: gol track par khambe ka chakkar lagate hue, agar dost bhi saath-saath aage chal raha ho toh dost ke saamne dobara aane ke liye thoda extra ghoomna padta hai. (Diagram: Sooraj, Dharti ki do sthiti 1° ke antar par, aur Dharti par ek teer jo pehle din Sooraj ki taraf aur agle din 360° ke baad thoda peeche reh jaata hai.)
📰 Case-Based Question
Priya ne Golu ke gaon mein ek lakdi gaadi aur 4 din sabse chhoti parchhai ka samay naapa: Din 1: 11:58, Din 2: 11:58, Din 3: 11:57, Din 4: 11:57. Din 3 ko thodi der badal bhi aaye the, par sabse chhoti parchhai ke samay dhoop thi. Rohan ne kaha, “Din 2 se Din 3 ka din 23:59 ka tha, matlab din chhota ho gaya!”
Q1. Din 1 se Din 4 tak teeno din ki lambai likho.
24:00, 23:59, 24:00.
Q2. Average din ki lambai kitni aayi?
(24:00 + 23:59 + 24:00) ÷ 3 = 71 ghante 59 minute ÷ 3 ≈ 23 ghante 59 minute 40 second, yaani lagbhag 24 ghante.
Q3. Kya Rohan ka nishkarsh sahi hai? Kyun?
Nahi. Minute wali ghadi aur chalk ke bindu se ±1 minute ki galti normal hai, aur solar day asal mein sirf kuch second hi badalta hai. Ek reading se “din chhota ho gaya” kehna theek nahi; average dekhna chahiye.
Q4. Priya ki readings ko aur sateek kaise banaya ja sakta hai?
Har minute ki jagah har 30 second par bindu lagaana, lambi lakdi (lambi parchhai, chhota farq bhi dikhe) lena, zyaada dinon tak naapna aur average lena, aur lakdi ko plumb line se bilkul seedha rakhna.
🚀 HOTS
1. Agar Dharti apni dhuri par ghoomna band kar de (par Sooraj ki parikrama jaari rakhe), toh ek “din” kitna lamba hoga?
Tab Sooraj aasmaan mein sirf Dharti ki parikrama ki wajah se khisakta dikhega, toh ek “Sooraj ka chakkar” = poora saal. Yaani lagbhag 6 mahine lagaataar din aur 6 mahine raat!
2. Ek bachcha shadow-stick activity mein roz alag jagah lakdi gaadta hai. Uske results par kya asar padega?
Zameen samtal na ho ya lakdi ki oonchai/seedhapan badle toh parchhai ki lambai badlegi, aur galat bindu “sabse chhota” lag sakta hai. Lekin sabse chhoti parchhai ka samay mukhya roop se Sooraj par nirbhar hai, toh agar har din lakdi bilkul seedhi ho aur zameen samtal ho, toh samay lagbhag sahi aayega. Achha tareeka: ek hi jagah, ek hi lakdi.
3. Mangal (Mars) par ek din ~24 h 40 min ka aur saal ~687 Dharti-din ka hai. Mangal par ek “saal” mein Mangal ke kitne din honge (lagbhag)?
687 Dharti-din = 687 × 24 = 16,488 ghante. Mangal ka din = 24 h 40 min ≈ 24.67 ghante. 16,488 ÷ 24.67 ≈ 668 Mangal-din. Matlab har grah ki apni “ghadiyaan” hain!
🏆 Olympiad Corner
1. Ek taara aaj raat 9:00 baje theek sir ke upar hai. 15 din baad woh lagbhag kitne baje sir ke upar hoga? (a) 9:00 (b) 8:00 (c) 10:00 (d) 8:56
✅ (b) 8:00: taara roz ~4 minute pehle aata hai; 15 × 4 = 60 minute pehle.
(a) taare solar din ke hisaab se nahi chalte.
(c) ulti disha: der se nahi, pehle aata hai.
(d) sirf ek din ka farq liya.
2. Dharti ko 75° ghoomne mein kitna samay lagega? (a) 3 h (b) 5 h (c) 7.5 h (d) 18.75 h
✅ (b) 5 h: 1 ghante mein 15°, toh 75 ÷ 15 = 5 ghante.
(a) 15 ki jagah 25° prati ghanta maan liya.
(c) 10° prati ghanta maan liya.
(d) 75 × 0.25 kar diya (4 ka ulta).
3. Do shehar A (78° E) aur B (90° E). B mein local noon 11:40 hai. Usi din A mein lagbhag kab? (a) 10:52 (b) 11:28 (c) 12:28 (d) 12:40
✅ (c) 12:28: A, B se 12° pashchim hai; 12 × 4 = 48 minute der se; 11:40 + 0:48 = 12:28.
(a) 48 minute ghata diya (disha ulti).
(b) sirf 12 minute joda.
(d) 1 ghanta joda.
📚 Aur Padho (External Reference)
- NCERT Class 8 Science Curiosity, Chapter 11 (official PDF)
- DIKSHA: Sarkar ka free learning platform, NCERT ke videos ke liye
💖 CharuMam Motivation
Sooraj kabhi chhutti nahi leta, beta. Har din wahi ek chakkar, wahi niyam, aur isi niyam se poori duniya ka calendar chalta hai. Ek din chhota lagta hai, par 365 din milkar mausam badal dete hain.
Padhai bhi aisi hi hai. Roz bas thoda sa, par roz. Aaj ka ek chhota sa “chakkar” kal ki badi kaamyaabi ka din banega. Apni ghadi khud bano! ☀️📅
— CharuMam
▶️ Is topic ki video dekhein: 29 February Har Saal Kyun Nahi Aati? Leap Year
▶️ Is topic ki video dekhein: IST UTC+5:30 Kyun? 82.5° Ka Hisab
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