Kuphila emhlabeni bekungeke kube khona kube kute luhlelo loluphelele etintfweni letinyenti, letinye letatingacondzakali kahle kwate kwaba sekhulwini lesi-20 leminyaka. Loluhlelo loluphelele luhlanganisa naku lokulandzelako:

• Indzawo umhlaba lokuyo ku-Milky Way nakumaplanethi netinkhanyeti (solar system), kujikeleta, kutjeka, litubane lekujikeleta kwawo, kanye nenyeti

• Emandla atibutse kanye nemkhatsi losivikelo lesikabili

• Imijikeleto yemvelo levusetela futsi ihlobise umoya kanye nemanti eplanethi

Njengobe ucabangela ngalinye lalamaphuzu, tibute: ‘Tintfo letisemhlabeni tavela ngengoti yini nobe tentiwa ngenjongo?’

Yini loyifakako nawubhala indzawo lohlala kuyo? Usengafaka live, lidolobha kanye nesitaladi. Ngemcondvo longumfanekiso, asesibite i-Milky Way umhlaba lokuyo ngekutsi “live,” emaplanethi netinkhanyeti abe “lidolobha,” bese kutsi indlela umhlaba lojikeleta kuyo (orbit) ibe “sitaladi.” Ngesizatfu sentfutfuko kutekuhlolwa nobe kufundvwa kwetinkhanyeti kanye nesayensi yemvelo, bososayensi sebayicondza kancono indzawo lesiphila kuyo.

Kwekucala nje, “lidolobha” letfu, nobe emaplanethi netinkhanyeti, lisendzaweni lenhle ye-Milky Way—lengekho dvutane nemkhatsi, futsi lengekho khashane nawo. “Lendzawo lokuhlalekako kuyo,” njengobe bososayensi bayibita, icuketse linani lelifanele lemakhemikhali ladzingekako kute isekele kuphila. Ngephandle, lawo makhemikhali awekho; ekhatsi nekhatsi kwe-Milky Way indzawo iyingoti kakhulu ngesizatfu sekutsi minyenti imisebe lebulalako kanye naletinye tintfo. Magazini i-Scientific American utsi: “Sihlala endzaweni lenhle kakhulu.”¹

“Sitaladi” lesihle: Lenye indzawo “lenhle” kakhulu yemhlaba “sitaladi” lokuso, nobe indlela lojikeleta kuyo “edolobheni” letfu lelingemaplanethi netinkhanyeti. Ebangeni lelingaba ngemakhilomitha latigidzi letingu-150 kusuka elangeni, lendlela isekhatsi kwendzawo lokuhlalekako kuyo ngobe ayicandzi futsi ayishisi kakhulu. Ngetulu kwaloko, lendlela yemhlaba cishe isiyingiliti, lokusenta cishe sibe sebangeni lelilinganako kusuka elangeni umnyaka nemnyaka.

Lilanga lona “lingumtfombo wemandla” lomangalisako. Alihambi, likhulu ngendlela lefanele, futsi likhipha emandla lasezingeni lelifanele. Libitwa kufanele ngekutsi “yinkhanyeti lekhetseke kakhulu.”²

“Makhelwane” lomuhle: Kube bewungakhetsa “makhelwane” wemhlaba, kute loncono bewungamkhetsa kwendlula inyeti. Bukhulu bayo bungetudlwana kwekota yebukhulu bemhlaba. Ngako-ke, nayicatsaniswa naletinye tinyeti letikhona kumaplanethi  netinkhanyeti, inyeti yetfu yinkhulu kakhulu nayicatsaniswa neplanethi lehambisana nayo. Kwenteka ngeliphutsa yini loku? Cha akusinjalo.

Kwekucala, inyeti ngiyo leyimbangela lenkhulu yekuphakama kwemagagasi aselwandle, lokuyintfo lebalulekile emvelweni yemhlaba. Inyeti yenta nekutsi ema-eksisi (axis) emhlaba atinte. Ngephandle kwalenyeti leyentiwe ngendlela lekhetsekile, iplanethi yetfu beyitawugucugucuka njengethophi leseyitawukuwa, mhlawumbe ite igicike! Lushintjo esimeni selitulu, ekuphakameni kwemagagasi nakuletinye tintfo belungaba yinhlekelele.

Kutjeka nekujikeleta kwemhlaba lokumangalisako: Kutjeka kwemhlaba ngema-degree langaba ngu-23.4 kubangela kushintja kwetikhatsi temnyaka minyaka yonkhe, kugcina emazinga ekushisa asesilinganisweni futsi kubangela kugucugucuka kwesimo selitulu. Incwadzi letsi Rare Earth​—Why Complex Life Is Uncommon in the Universe itsi: “Ema-eksisi ekutjeka kweplanethi yetfu abonakala ‘afaneleke kahle.’”³

Lokunye “lokuhle kakhulu” budze bemini nebusuku, lokubangelwa kujikeleta kwemhlaba. Kube umhlaba bewujikeleta ngelitubane leliphansi, emalanga abetawuba madze futsi loluhlangotsi lwawo lolubukene nelilanga belutawushisa kakhulu kantsi lolu lolunye lona belutawuba lichwa. Ngakulolunye luhlangotsi, kube umhlaba bewujikeleta ngelitubane lelisetulu, emalanga abetawuba mafishane, mhlawumbe atsatse ema-awa lambadlwana, futsi kujikeleta kwemhlaba ngekushesha bekutawubangela tiphepho kanye naleminye imiphumela leyingoti.

Umkhatsi uyindzawo leyingoti levame kuba nemisebe lebulalako kantsi netinguzanguza tematje nato tiyingoti levamile. Nanobe kunjalo, kubonakala shengatsi iplanethi yetfu leluhlata sasibhakabhaka ihamba “kulesiminyaminya setintfo letintjuza” emkhatsini ngephandle kwenkinga. Kungani? Kungobe umhlaba unesivikelo lesimangalisako​—lokungemandla atibutse kanye nemkhatsi lowentiwe ngendlela lekhetsekile.

Emandla atibutse emhlaba: Indzawo lesemkhatsini wemhlaba iyibhola lejikeletako yensimbi lencibilikile, lebangela kutsi iplanethi yetfu ibe nemandla atibutse lamakhulu laluleka ate afike emkhatsini. Lesivikelo sisivikela emisebeni lenemandla levela emkhatsini kanye nasetingotini letibangelwa lilanga. Letingoti tifaka ekhatsi ema-solar wind, latinhlayiya letinyenti letinemandla, njengema-proton kanye nema-electron; ema-solar flare, lakhipha emandla langalingana nalawo lakhishwa ngemabhomu e-hydrogen latigidzigidzi ngemizuzu lembalwa; kuchuma lokusencenyeni lengephandle yelilanga nobe  i-corona, lekhiphela tigidzigidzi temathani etintfo emkhatsini. Kunetintfo longatibona letisikhumbuto sekuvikelwa lokutfola emandleni atibutse emhlaba. Ema-solar flare kanye nekuchuma lokwenteka encenyeni yelilanga lengephandle nobe i-corona kukhipha imisebe leshisa kakhulu, lebonakala emkhatsini dvutane netincenye temhlaba letisenyakatfo naletiseningizimu (magnetic poles).

Umkhatsi wemhlaba: Lengubo yemagesi ayisigcini nje siphefumula kodvwa iphindze isinikete nalesinye sivikelo. Incenye yawo lengephandle lokutsiwa yi-stratosphere, icuketse luhlobo lwe-oxygen lokutsiwa yi-ozone, lebamba emaphesenti langu-99 emisebe ye-ultraviolet (UV) levela ngephandle. Ngako-ke, ludvwadvwasi lwe-ozone luvikela tinhlobo letinyenti tekuphila​—lokuhlanganisa bantfu kanye ne-plankton lesakhela linyenti le-oxygen lesiyidzingako—​emisebeni leyingoti. Umtsamo we-ozone lesemkhatsini ute linani lelicondzile. Kunaloko lelinani liyashintjashintja, liyakhula njengobe emandla emisebe ye-UV akhula. Ngako-ke, ludvwadvwasi lwe-ozone lusivikelo lesihle nalesiphumelelako.

Umkhatsi wemhlaba uphindze usivikele nasematjeni lavela emkhatsini​—lokutigidzi tetintfo letinebukhulu lobehlukehlukene, kusukela etinhlayiyeni letincane kuya etinguzanguzeni letinkhulu. Lamanyenti alamatje ayasha emkhatsini, abe kukhanya lokukhulu lokutsiwa tinkhanyeti letindizako (meteors). Nobe kunjalo, tivikelo temhlaba atiyivimbi imisebe lebalulekile ekuphileni, njengekushisa nekukhanya lokubonakalako. Umkhatsi wemhlaba usita nasekusabalaliseni kushisa emhlabeni, futsi ebusuku ube njengengubo lebamba kushisa.

Umkhatsi wemhlaba kanye nemandla atibutse kutintfo letentiwe ngendlela lesimangaliso nalengacondzakali kahle. Kungashiwo lokufananako nangemijikeleto lesekela kuphila kuleplanethi.

Nangabe kungaphela umoya lohlobile nemanti edolobheni, kuvaleke nemaphayiphi lahambisa emangcoliso, ngekushesha nje bekuyawulandzela tifo kanye nekufa kwebantfu. Kodvwa caphela: Iplanethi yetfu ayifanani nelikhefi, lapho kufakwa khona kudla naletinye tintfo letinsha letivela ngephandle bese dodi atsatfwa ayolahlwa khashane. Umoya nemanti lahlobile lesiwasebentisako awaveli endzaweni lengephandle kwemkhatsi wemhlaba, nekungcola akulahlwa nobe akuphumeli ngephandle. Kodvwa-ke umhlaba uhlala njani unemphilo futsi ulungele kutsi kuphilwe kuwo? Sizatfu kutsi kunemijikeleto yemvelo, njengemjikeleto wemanti, wekhabhoni, we-oxygen, newe-nitrogen, lechazwe lana futsi lekhonjiswe ngendlela lelula.

Umjikeleto wemanti: Siyawadzinga emanti kute siphile. Kute umuntfu longaphila sikhatsi lesidze ngephandle kwemanti. Umjikeleto wemanti ukhiphela umhlaba emanti lamasha nalahlantekile. Uhlanganisa tigaba letintsatfu. (1) Kushisa lokuvela elangeni kwenta emanti abe ngumswakama. (2) Ngesikhatsi lamanti lahlantekile acala kubutsana, kwakheka emafu. (3) Emafu wona akha imvula, sangcotfo, tinkhungu kanye nelichwa lelikhitsikela emhlabatsini, futsi ngemuva kwaloko kuba ngumswakama, kanjalo kuphelelise lomjikeleto. Angakanani emanti lenta lomjikeleto umnyaka nemnyaka? Nakulinganiswa, kungaba ngemanti lenele kutsi angambonya wonkhe umhlaba, futsi kushona kwawo kungaba ngetulu kwemasentimitha langu-80.⁴

Imijikeleto yekhabhoni kanye ne-oxygen: Njengobe wati, kute uphile kudzingeka uphefumule, udvonse i-oxygen futsi ukhiphe i-carbon dioxide. Kodvwa njengobe kunetigidzigidzi tebantfu netilwane letenta intfo lefananako, kwenteka njani kutsi umkhatsi ungaphelelwa yi-oxygen futsi ugcwale i-carbon dioxide? Imphendvulo itfolakala emjikeletweni we-oxygen. (1) Enchubeni lemangalisako lebitwa ngekutsi yi-photosynthesis, titjalo tidvonsa i-carbon dioxide leyo tsine lesiyikhiphako. Tiyisebentisa kanye nekushisa lokuvela elangeni kute tente kudla kanye ne-oxygen. (2) Nasidvonsa i-oxygen, sisuke siphelelisa lomjikeleto. Konkhe lokwakhiwa kwetitjalo kanye nemoya lesikwati kuwuphefumula kwenteka ngendlela lehlantekile, ngelikhono futsi kwenteka ngephandle kwemsindvo.

 Umjikeleto we-nitrogen: Kuphila emhlabeni kuphindze kwetsembele ekwakhekeni kwemamolekhiyuli emvelo lanjengema-protein. (A) Kute kwakheke emamolekhiyuli lanjalo kudzingeka i-nitrogen. Loluhlobo lwegesi lwakha incenye lecishe ibe ngemaphesenti langu-78 emkhatsi wetfu. Umbani ugucula i-nitrogen ibe tinhlanganisela (compounds) letingamunywa titjalo. (B) Ngemuva kwaloko, titjalo tigucula letinhlanganisela tibe ngemamolekhiyuli emvelo. Kanjalo, tilwane letidla leto titjalo titfola i-nitrogen. (C) Ekugcineni, ngesikhatsi titjalo kanye netilwane tifa, tinhlanganisela te-nitrogen letikuto tehlukaniswa ngemagciwane. Lenchubo yekubola ibuyisela i-nitrogen emhlabatsini nasemkhatsini, kanjalo iphelelise lomjikeleto.

Bantfu, nanobe banebucwephesha lobusembili, babangela incumbi yemfucumfucu lenebutsi nalengasebentiseki umnyaka nemnyaka. Nobe kunjalo, umhlaba uneluhlelo lwekuphindze uyisebentise yonkhe leyo mfucumfucu, ngekusebentisa buciko bebunjiniyela bemakhemikhali.

Ucabanga kutsi loluhlelo lwemhlaba lwekusebentisa tintfo kabusha lwavela njani? M. A. Corey, longumbhali wetenkholo netesayensi utsi: “Kube imvelo yemhlaba yavela ngengoti nje kuphela beyingeke ibe nekuvumelana kwemvelo lokunjalo.”⁵ Uyavumelana yini naloko lakushoko?