Class 8 Science Chapter 11: Keeping Time with the Skies (Hinglish Notes)

Ye chapter kis baare mein hai?

Makar Sankranti par Ahmedabad ke patang utsav mein Meera din mein chaand chamakta dekhti hai, aur wo bhi poora gol nahi. Agar chaand Suraj se roshan ek gola hai, to uska aakaar badalta kyon lagta hai? Chapter ek maheene tak chaand ko dekhkar iska jawaab deta hai, aur phir dikhaata hai ki Suraj aur chaand ke niyamit chakron se humein din, maheena, saal aur hamare calendar kaise mile.

Chaand ki kalaayein

Purnima ke agle din se suryoday par dekhein to chaand ka chamakta hissa lagbhag ek hafte mein aadha reh jaata hai aur agle hafte gaayab ho jaata hai. Ye ghatta chaand ka samay hai, yaani Krishna Paksha. Amavasya ke baad chamakta hissa ek hafte mein aadha aur agle hafte poora, Purnima, ho jaata hai: ye badhta chaand ya Shukla Paksha hai. In badalte aakaaron ko chaand ki kalaayein kehte hain, aur ek chakra lagbhag ek maheene ka hota hai. Padhein: chaand ki kalaayein.

Kalaayein kyon hoti hain

Chaand ki apni roshni nahi hai; wo Suraj ki roshni lautaata hai. Suraj ki or wala aadha hissa hamesha roshan rehta hai aur baaki aadha andhera. Chaand jab Dharti ka chakkar lagaata hai, to hamari or wale aadhe mein roshan hissa kabhi poora, kabhi thoda aur kabhi bilkul nahi hota: Purnima par poora, Amavasya par kuch nahi, crescent mein aadhe se kam aur gibbous mein aadhe se zyada. Lamp ke paas haath bhar door pakdi gend bhi yahi dikhaati hai.

Purnima par chaand Suraj ke saamne ki taraf hota hai; agli subahon mein wo Suraj ke paas dikhta hai, aur Amavasya par sabse paas. Badhta chaand suryaast ke aas-paas aur ghatta chaand suryoday ke aas-paas dekhiye. Dharti ko chaand tak pahunchne ke liye thoda aur ghoomna padta hai, kyonki chaand apni kaksha mein aage badhta rehta hai, isliye chaand roz lagbhag 50 minute der se ugta hai, kabhi dopahar mein bhi, isiliye Meera ko wo din mein dikha.

Kalaayein Dharti ki chhaaya se nahi hoti. Chaand par Dharti ki chhaaya chandra grahan hai, jo sirf Purnima par ho sakta hai, jaise surya grahan sirf Amavasya par. Grahan har maheene nahi hote kyonki chaand ki kaksha thodi jhuki hui hai.

Din, maheena aur saal

Suraj ka roz ugna aur doobna Dharti ke apni dhuri par ghoomne se hai. Suraj ki ek din ki sabse oonchi jagah se agle din ki sabse oonchi jagah tak ka ausat samay 24 ghante hai, yaani mean solar day, jise ek dande ki sabse chhoti parchhaai se naapa ja sakta hai. Chaand ki kalaayein lagbhag 29.5 din mein dohraati hain, jisse maheena milta hai, aur Dharti ke Suraj ka chakkar lagaane se rituein lagbhag 365¼ din mein dohraati hain, jisse saal milta hai.

Calendar

Ek ritu-chakra mein lagbhag 12 chandra maas samaate hain, isliye chandra calendar ka saal 354 din ka hota hai, jo dheere-dheere rituon se khisakta jaata hai. Gregorian jaise saur calendar 365 din ke saath rituon ke saath chalte hain aur har chaar saal mein ek leap day jodte hain, us century saal ko chhodkar jo 400 se na bante. Chandra-saur calendar maheene chaand se ginte hain par har 2 se 3 saal mein ek atirikt maheena, Adhika Maasa, jodte hain. Padhein: calendar kaise bane?.

Bharatiya calendar aur tyohaar

Telescope se bahut pehle Bharat ke dhyaan se dekhne waalon ne paaya ki Suraj garmi mein poorab se thoda uttar mein aur sardi mein thoda dakshin mein ugta hai: uska uttar ki or khiskna Uttarayan aur dakshin ki or khiskna Dakshinayan hai, jiska zikr Taittiriya Samhita mein hai. Indian National Calendar, jiski sifaarish khagol-vaigyanik Meghnad Saha ki adhyakshata wali committee ne ki, 365 din ka saur calendar hai jo 22 March ko shuru hota hai. Diwali, Holi aur Eid chaand ke hisaab se chalte hain aur har saal taareekh badalte hain, jabki Makar Sankranti, Pongal aur Bihu saur calendar se chalte hain.

Kritrim upgrah

Chaand Dharti ka praakritik upgrah hai, par kai kritrim upgrah bhi Dharti ka chakkar lagaate hain, zyaadatar lagbhag 800 km oonchaai par, lagbhag 100 minute mein ek chakkar. Ye sanchaar, raasta dhoondhne, mausam, aapda prabandhan aur research mein madad karte hain. ISRO ne kai upgrah bheje hain, nakshon ke liye Cartosat se lekar taaron ke adhyayan ke liye AstroSat tak. Padhein: kritrim upgrah.

Aage badhne se pehle

Chaand ki kalaayein, rituein aur Suraj ki roz ki chaal prakritik chakra hain jo anumaan lagaane laayak dhang se dohraate hain, aur logon ne inhi par calendar banaaye. Har sawaal ka jawaab Chapter 11 ke NCERT solutions mein hai.