Kusho ukuthini unyaka wokukhanya?
Uma kukhulunywa ngezinkanyezi, ibanga lingenye yezinto ezinzima kakhulu ukuzibona ngeso lengqondo. Ngokungafani nokuhamba phakathi kwamadolobha, okungalinganiswa ngamakhilomitha, amabanga phakathi kwezinkanyezi nemithala makhulu kakhulu kangangokuthi amayunithi esivame ukuwasebenzisa eMhlabeni awasebenzi. Ngakho-ke, ososayensi basebenzisa amayunithi akhethekile ebanga ukuchaza izikali ze-cosmic, esinye sazo yi-light-year. Ngakho-ke, iyini i-light-year, kungani isetshenziswa, futhi singayiqonda kanjani? Lesi sihloko sizoxoxa ngalokhu ngokuningiliziwe.
Incazelo yonyaka wokukhanya
Unyaka wokukhanya uyiyunithi yebanga, hhayi isikhathi. Ichazwa njengebanga elihanjwa ukukhanya endaweni engenalutho ngonyaka owodwa. Ukukhanya—okuhamba ngesivinini esikhulu kakhulu—kuwumbusi owusizo wokulinganisa amabanga endaweni yonke.
Abantu abaningi bacabanga ngephutha ukuthi elithi "light-year" libhekisela ebude besikhathi. Lokhu kudideka kuyaqondakala, njengoba igama elithi "unyaka" lifana nekhalenda. Kodwa-ke, kuleli gama, elithi "unyaka" lisetshenziselwa ukukhombisa ubude bohambo lokukhanya, kanti umphumela uba ibanga elihanjiwe phakathi naleso sikhathi.
Isivinini sokukhanya njengesisekelo
Ukuze siqonde unyaka wokukhanya, sidinga ukwazi isivinini sokukhanya. Endaweni engenamuntu, ukukhanya kuhamba cishe:
Amamitha angu-299.792.458 ngomzuzwana
noma cishe amakhilomitha angu-300.000 ngomzuzwana.
Lokhu kusho ukuthi ngomzuzwana owodwa, ukukhanya kungazungeza uMhlaba izikhathi ezingaphezu kweziyisikhombisa (umjikelezo woMhlaba ungamakhilomitha angaba ngu-40.075). Leli jubane lingenye yezinto ezibaluleke kakhulu kwifiziksi yanamuhla, njengoba libeka umkhawulo wejubane lolwazi namandla ngokwemfundiso yokuhlobana.
Ungakanani unyaka wokukhanya?
Ukuze sithole inani lonyaka owodwa wokukhanya, siphindaphinda ijubane lokukhanya ngenani lemizuzwana ngonyaka owodwa.
Unyaka owodwa (cishe) unalokhu:
Izinsuku ezingu-365 × amahora angu-24 × imizuzu engu-60 × imizuzwana engu-60 = imizuzwana engu-31.536.000.
Ngakho ibanga lonyaka wokukhanya cishe liyi:
300.000 km/sekondi × 31.536.000 imizuzwana = 9.460.800.000.000 km.
Ngakho-ke, unyaka owodwa wokukhanya ≈ amakhilomitha ayizigidigidi ezingu-9,46.
Leli nani likhulu kakhulu kangangokuthi kunzima ukuliqonda. Uma uqhathanisa, ibanga elimaphakathi ukusuka eMhlabeni ukuya eLangeni "lingamakhilomitha ayizigidi ezingu-150 kuphela." Lokhu kusho ukuthi unyaka owodwa wokukhanya cishe ulingana nebanga eliphakathi koMhlaba neLanga izikhathi ezingaphezu kuka-63.000.
Kungani usebenzisa iminyaka yokukhanya?
Isizathu esiyinhloko sokusebenzisa iminyaka yokukhanya ukusebenza kahle. Uma amabanga phakathi kwezinto zasemkhathini ebengavezwa ngamakhilomitha, izinombolo beziyoba zinde kakhulu futhi zibe nzima.
Isibonelo, inkanyezi iProxima Centauri (inkanyezi eseduze kakhulu neLanga ngemva kweLanga ngokwalo) iqhele ngebanga eliyiminyaka yokukhanya engu-4,24. Uma ichazwa ngamakhilomitha, lokho kungamakhilomitha ayizigidigidi ezingu-40. Ukufunda nokuqhathanisa amabanga ngamakhilomitha ayizigidigidi akucaci ukuthi akusebenzanga kahle.
Ngeyunithi yonyaka wokukhanya, izazi zezinkanyezi zingenza lokhu kalula:
1. Ukuxhumana ngamabanga aphakathi kwezinkanyezi.
2. Ukuqhathanisa isikali phakathi kwezinto ezisendaweni yonke.
3. Xhuma ibanga nomqondo othakazelisayo: isikhathi sokuhamba esilula.
Iminyaka yokukhanya kanye "nokubona okwedlule"
Kukhona iqiniso elithakazelisayo elivame ukumangaza abantu: uma sibheka izinto zasezulwini ezikude, empeleni sibheka emuva ngesikhathi. Lokhu kungenxa yokuthi ukukhanya kuthatha isikhathi ukufinyelela emehlweni ethu.
Ngokwesibonelo:
– Ilanga liqhele cishe ngemizuzu eyi-8 yokukhanya ukusuka eMhlabeni. Lokhu kusho ukuthi ukukhanya kwelanga esikubonayo manje yilokho ilanga elalibukeka ngakho emizuzwini eyi-8 edlule.
– I-Proxima Centauri iqhele ngeminyaka yokukhanya engu-4,24. Ngakho-ke, sibona inkanyezi njengoba yayinjalo eminyakeni engu-4,24 edlule.
– I-Andromeda Galaxy iqhele ngebanga elingama-light-year ayizigidi ezingu-2,5. Lokhu kusho ukuthi ukukhanya esikutholayo namuhla kwaqala lapho uMhlaba ungenalo impucuko yabantu yesimanje.
Yingakho ama-telescope esebenza “njengemishini yesikhathi” ngandlela thile: lapho into ebonwayo ikude, kulapho ukukhanya sikubona kudala khona.
Ingabe unyaka wokukhanya ufana ne-parsec?
Ngaphandle konyaka wokukhanya, izazi zezinkanyezi zivame ukusebenzisa enye iyunithi ebizwa ngokuthi i-parsec. Zombili ziyiyunithi yebanga, kodwa zithathwe emiqondweni ehlukene.
– Unyaka wokukhanya: ngokusekelwe ebangeni elihanjwa ukukhanya ngonyaka owodwa.
– I-Parsec: isekelwe endleleni yokulinganisa indawo yezinkanyezi kusetshenziswa i-parallax (ukushintsha kwendawo ebonakalayo ngenxa yezinguquko ekhoneni lokubuka kusukela ekuzungelezeni koMhlaba).
Ubudlelwano phakathi kwalaba ababili:
– I-parsec eyi-1 ≈ iminyaka yokukhanya engu-3,26 .
Ama-parsec avame ukusetshenziswa ezincwadini zesayensi ngoba ahambisana namasu okulinganisa izinkanyezi. Kodwa-ke, iminyaka yokukhanya ithandwa kakhulu emphakathini jikelele ngoba izwakala kulula ukuyiqonda.
Isibonelo sebanga kusetshenziswa iminyaka yokukhanya
Ukuze sikubeke lokhu esimweni, nazi ezinye izibonelo zamabanga eminyakeni yokukhanya:
1. Inkanyezi eseduze kakhulu neSistimu Yelanga (i-Proxima Centauri): cishe iqhele ngeminyaka yokukhanya engu-4,24.
2. Isikhungo se-Milky Way Galaxy: cishe iminyaka yokukhanya engu-26.000.
3. Ububanzi be-Milky Way Galaxy: cishe iminyaka yokukhanya eyi-100.000–120.000.
4. I-Andromeda Galaxy: cishe iminyaka yokukhanya eyizigidi ezingu-2,5.
5. Imithala ekude kakhulu ebonwa ngamatheleskopu anamuhla ingaba kude ngezigidigidi zeminyaka yokukhanya.
Ngalesi sibonelo singabona ukuthi iminyaka yokukhanya yenza amabanga omkhathi abe “anengqondo” kakhulu ukukhuluma ngawo.
Ingabe ukukhanya kuhamba ngesivinini esifanayo ngaso sonke isikhathi?
Incazelo yonyaka wokukhanya ibhekisela ekukhanyeni okuhamba endaweni engenalutho. Ezindaweni ezifana namanzi, ingilazi, noma umkhathi, ijubane lokukhanya liyancipha ngenxa yokusebenzisana nezinto. Kodwa-ke, ngamabanga aphakathi kwezinkanyezi—okuyizindawo ezingenalutho kakhulu—ijubane lokukhanya endaweni engenalutho liyindlela engcono kakhulu yokucabanga.
Ngakolunye uhlangothi, ku-cosmology yanamuhla, izenzakalo ezifana nokwanda kwendawo yonke zenza kube nzima ingxoxo yamabanga amakhulu kakhulu. Ezintweni ezikude kakhulu, izazi zezinkanyezi ngezinye izikhathi zisebenzisa imiqondo ehlukile yebanga njenge-"comoving distance" noma "lookback time." Noma kunjalo, unyaka wokukhanya uhlala uwusizo njengesifanekiso esiqondakala kalula.
Isiphetho
Ngakho-ke, unyaka wokukhanya yiyunithi yebanga echaza ukuthi ukukhanya kuhamba ibanga elingakanani ngonyaka endaweni engenamuntu. Inani layo lingaba amakhilomitha ayizigidigidi ezingu-9,46. Le yunithi iwusizo kakhulu ekuchazeni amabanga phakathi kwezinkanyezi naphakathi kwemithala okungaba yinto engenangqondo uma ibhalwe ngamakhilomitha ajwayelekile. Ngaphezu kwalokho, unyaka wokukhanya uphinde uvule ukuqonda okuthakazelisayo kokuthi ukubuka izinto ezikude kusho ukubheka izimo zazo zangaphambilini, ngoba ukukhanya kuthatha isikhathi ukusifinyelela.
Ngokuqonda ukuthi kusho ukuthini unyaka wokukhanya, asigcini nje ngokujwayelana neyunithi entsha yokulinganisa, kodwa futhi siqala ukuqonda ubukhulu bendawo yonke kanye nokungabi nalutho kwethu ngaphakathi kwayo—umbono owenza isayensi yezinkanyezi ikhange kangaka.
