Bekungenakubakho nto iphilayo kulo mhlaba ukuba kwakungazange kwenzeke “ngamabona-ndenzile” uthotho lwezinto ezinye zazo ezazingaziwa okanye zingaqondwa kakuhle de kwayinkulungwane yama-20. Nazi ezinye zezo zinto:

• Indawo okuyo umhlaba kumnyele wethu iMilky Way nakummandla wezijikelezi-langa, indlela ohamba kuyo, ukuthambeka kwawo, isantya ojikeleza ngaso nenyanga yawo engaqhelekanga

• Imagnethi yomhlaba kunye nomoya ojikeleze umhlaba (iatmosphere), nto ezo zikhusela umhlaba

• Imijikelo yendalo ehlaziya umhlaba ize icoce umoya esiwuphefumlayo namanzi

Njengokuba uqwalasela ngamnye kule mixholo, zibuze oku: ‘Ngaba izinto ezikulo mhlaba zazivelela ngamabona-ndenzile okanye zadalwa ngumntu okrelekrele?’

Ziziphi izinto ozifakayo xa ubhala iadresi yakho? Kunokufuneka ilizwe, isixeko nesitrato. Ukuzekelisa oku, masithi umnyele wethu iMilky Way “lilizwe” okulo umhlaba, wona ummandla wezijikelezi-langa—ilanga neeplanethi zalo—“sisixeko” somhlaba, ize indlela ohamba kuyo kummandla wezijikelezi-langa ube “sisitrato” sawo. Ngenxa yokuhambela phambili kwenzululwazi yeenkwenkwezi, izazinzulu ziye zafunda okungakumbi ngokubaluleka kwendawo ekhethekileyo omi kuyo umhlaba kwindalo iphela.

Okokuqala, “isixeko” sethu, okanye ummandla wezijikelezi-langa, sikweyona ndawo ifanelekileyo kumnyele iMilky Way—asikho kufuphi kangako kumbindi womnyele singekude nakangako kuwo. Kule ndawo sikuyo esi “sixeko,” nebizwa ngokuba “ngummandla onezinto eziphilayo” zizazinzulu, kukho imichiza eyaneleyo ukuze izinto ziphile. Xa uphumela ngaphandle kwale ndawo, le michiza iyaphela; ukanti ukungena ngaphakathi usondela embindini womnyele kuyingozi kakhulu ngenxa yemitha nezinye izinto eziyingozi. Iphephancwadi iScientific American¹ lithi: “Siphila kweyona ndawo ifanelekileyo.”

“Isitrato” esifanelekileyo: Ayikho indawo efaneleke “njengesitrato” okuso umhlaba, okanye indlela ohamba kuyo kummandla wezijikelezi-langa “osisixeko” sawo. Le ndlela uhamba kuyo umhlaba, ikumgama wezigidi ezili-150 zeekhilomitha ukusuka elangeni, ngaphakathi kummandla onezinto eziphilayo, apho kungekho kubanda nobushushu obugqithiseleyo. Ukongezelela koko, indlela ohamba kuwo iphantse ibe ngqukuva, nto leyo esigcina sikumgama ophantse ulingane ukusuka elangeni unyaka wonke.

Sikwanalo nelanga, elingumthombo wawo onke amandla akulo mhlaba. Lizinzile, likhulu ngokwaneleyo yaye likhupha umlinganiselo ofanelekileyo wamandla alungele umhlaba. Yiloo nto, kusithiwa “yinkwenkwezi ekhethekileyo.”²

 “Ummelwane” ofanelekileyo: Ukuba bekungafuneka ukhethe “ummelwane” womhlaba, akakho obenokuba bhetele kunenyanga. Ingaphezulwana nje kwekota yomhlaba. Ngoko, xa ithelekiswa nezinye iinyanga ezikulo mmandla wezijikelezi-langa sikuwo, le yethu ithande ukuba ngaphezulu kubukhulu obuqhelekileyo beenyanga zezinye iiplanethi. Ngaba oku kwenzeka ngamabona-ndenzile? Kungangenkankulu!

Kaloku yinyanga elawula ukunyuka nokuhla kwamanzi olwandle, nto leyo edlala indima ephambili kwizinto eziphilayo nezisingqongileyo. Ikwayiyo ezinzisa umhlaba ukuze ujikeleze kakuhle. Ngaphandle kwenyanga elungiselelwe wona, umhlaba ubuya kuhexela macala onke, mhlawumbi ude uphethuke! Oko bekuya kubangela isiphithiphithi kwimozulu, kumanzi olwandle nakwezinye izinto.

Indlela efanelekileyo yokuthambeka nokujikeleza komhlaba: Ukuthambeka komhlaba ngeedegree ezimalunga nama-23.4 kuzisa amaxesha onyaka ahlukahlukeneyo, ubushushu obufanelekileyo, nemozulu eyahlukahlukeneyo kwiindawo ngeendawo. Incwadi ethi Rare Earth—Why Complex Life Is Uncommon in the Universe³ ithi: “Indlela othambeke ngayo umhlaba ‘ifaneleke’ kakuhle ukuze izinto ezikuwo ziphile.”

Kwakhona ukujikeleza komhlaba kwenza imini nobusuku zibe nobude “obufanelekileyo.” Ukuba umhlaba ubucotha ukujikeleza, usuku beluya kuba lude lize icala elijonge elangeni litshise ngokugqithiseleyo ngoxa elinye lisiba ngumkhenkce. Kwelinye icala, ukuba ubukhawuleza usuku beluya kuba lufutshane, mhlawumbi lube ziiyure nje ezimbalwa, yaye oko bekuya kuzisa imimoya ebhudla ngamandla nezinye iingxaki.

Zininzi iingozi ezisemajukujukwini, njengemitha yobushushu enokubulala abantu kunye neenkwenkwezi ezitshekayo zinqamleza isibhakabhaka. Sekunjalo, umhlaba ujikeleza phakathi kwazo zonke ezo ngozi ungachaphazeleki. Ngoba? Kaloku umhlaba unezinto eziwukhuselayo—imagnethi enamandla nomoya owenziwe ngokukhethekileyo ukuze ujikeleze umhlaba.

Imagnethi yomhlaba: Embindini womhlaba kukho udaka lwentsimbi olujikelezayo, nto leyo eyenza umhlaba ukhuphe imagnethi enamandla afikelela emajukujukwini. Le magnethi isikhusela kwimitha nolophu oluyingozi olukhutshwa lilanga. Olu lophu luquka umoya osemajukujukwini, onamasuntswana anamandla; amadangatye elanga athi ngomzuzu nje omnye akhuphe amandla alingana naweebhombu zehydrogen ezingaphaya kweebhiliyoni; kunye nezigidi  zeetoni zeentlantsi ezikhutshwa lilanga lizithumela kwalapho emajukujukwini. Ezi zinto zinokukunceda ubone indlela okhuselwa ngayo yimagnethi yomhlaba kwezi ngozi. Amadangatye elanga neentlantsi ezikhutshwa lilanga zitsho ngeengqimba zemibalabala ebonakala esibhakabhakeni xa ukufuphi neencam zomhlaba.

Umoya ojikeleze umhlaba: Lo moya awaneli nje ukusinceda siphefumle, uphinda usikhusele. Inxalenye yokugqibela yalo moya nebizwa ngokuba yistratosphere, ineoksijini ekuthiwa yiozone, ethintela malunga nama-99 ekhulwini emitha eshushu yeultraviolet (UV). Ngoko, iozone ikhusela izinto ezininzi eziphilayo—kuquka abantu, nezinto ezincinane eziphila emanzini esifumana kuzo ioksijini eninzi—kwimitha eyingozi. Ubungakanani beozone abusikelwa mda, buxhomekeka kwiqondo lokutshisa kwemitha yeUV obukhoyo ngelo xesha. Ngoko ke, iozone sisikhuseli esinamandla.

Lo moya uphinda usikhusele kwimfungumfungu yezinto eziwa esibhakabhakeni—izigidi zezinto ezincinane nezinkulu. Inkoliso yezi zinto iyatsha iphelele esibhakabhakeni, thina sibone nje ngenkwenkwezi etshekayo ishiya umsila onyamalala ngokukhawuleza. Kuyo yonke loo nto, ezi zikhuseli zomhlaba ziyayivumela idlule imitha yelanga efunwa zizinto eziphilayo, njengokufudumala nokukhanya. Umoya ojikeleze umhlaba ude uncede usasaze ukufudumala emhlabeni wonke, yaye ebusuku usebenza njengengubo ukuze kuhlale kufudumele.

Umoya ojikeleze umhlaba nemagnethi zizinto eziyilwe ngokumangalisayo yaye kuninzi okusamele kufundwe ngazo. Singatsho okufanayo nangemijikelo eyenzeka kulo mhlaba ukuze ubomi buqhubeke.

Ukuba umoya namanzi acocekileyo ebenokuvalwa esixekweni kuquka inkqubo yogutyulo, bekungayi kuba kudala abantu bahlaselwe zizifo bafe. Kodwa phawula oku: Umhlaba awufani nevenkile ethengisa ukutya, yona ithenga ukutya kwenye indawo kuze kufuneke iye kulahla inkunkuma kwenye. Umoya namanzi acocekileyo esixhomekeke kuwo akaveli ngaphandle komhlaba, yaye nenkunkuma ayithunyelwa ngaphandle kwawo. Yintoni ke enceda umhlaba uhlale ucocekile nokuze siphile kuwo? Yimijikelo yendalo, njengowamanzi, owecarbon, oweoksijini nowenitrogen njengokuba kucaciswa kuze kuboniswe ngendlela elula apha.

Umjikelo wamanzi: Amanzi abaluleke gqitha ebomini. Akukho namnye kuthi onokuphila iintsuku ezininzi ngaphandle kwawo. Umjikelo wamanzi nguwo osasaza amanzi acocekileyo kuwo wonke umhlaba. Oku kwenzeka ngamanqanaba amathathu. (1) Ubushushu bunyusa amanzi abe ngumphunga. (2) Uthi ke lo mphunga wamanzi acociweyo usakuba ngqindilili ube ngamafu. (3) Ayandula ke la mafu abe yimvula, isichotho, iliqhwa okanye ikhephu, ze onke loo manzi abuyele emhlabeni, sele ekulungele ukuphinda abe ngumphunga. Angakanani amanzi acocwa ngulo mjikelo ngonyaka? Kuqikelelwa ukuba maninzi kangangokuba anokuwugubungela wonke umhlaba aze abe ziisentimitha ezingaphezu kwama-80 ukuphakama.⁴

Umjikelo wecarbon neoksijini: Njengokuba usazi, ukuze uphile kufuneka uphefumle, ungenise ioksijini ngoxa ukhupha icarbon dioxide. Ekubeni kukho izigidi zabantu nezilwanyana eziphefumla kwalo moya mnye, kutheni ioksijini ingapheli kuze kusale icarbon dioxide egqithiseleyo? Kungenxa yomjikelo weoksijini. (1) Ngenxa yenkqubo emangalisayo ekuthiwa yiphotosynthesis, izityalo zisezela icarbon dioxide esiyikhuphayo xa siphefumla, zisebenzise yona nokukhanya kwelanga ukuze zivelise iicarbohydrate neoksijini. (2) Xa sisezela ioksijini, sifak’ isandla kulo mjikelo. Yonke le nto, ukuveliswa kwezityalo nokuphefumlwa komoya, yenzeka nje kakuhle kungekho nto ingcoliswayo yaye ithe cwaka.

 Umjikelo wenitrogen: Izinto ezisemhlabeni zixhomekeke ekuvelisweni kweemolekyuli zeorganic njengeprotini. (A) Kufuneka initrogen ukuze kuveliswe ezo molekyuli. Okuvuyisayo kukuba le nitrogen imalunga nama-78 ekhulwini kumoya osemhlabeni. Ukubaneka kuguqula initrogen kuze kwakhe ngayo izinto eziza kusetyenziswa zizityalo. (B) Zandula ke izityalo zisebenzise izinto ezakhiwa yinitrogen ukuvelisa iimolekyuli. Ngoko ke, izilwanyana ezitya ezi zityalo zifumana initrogen. (C) Zithi zakufa izityalo nezilwanyana, izinto ezincinane eziphilayo zahlulahlule ezo zinto bezakhiwe yinitrogen zibe ngamasuntswana. Xa kusenzeka konke oku initrogen ibuyela emhlabeni nasemoyeni.

Nakuba behambele phambili kwezobugcisa, nyaka ngamnye abantu bavelisa iitoni zenkunkuma enobungozi abangaziyo ukuba bayithini. Ukanti, wona umhlaba uyakwazi ukuyicoca ngokugqibeleleyo uphinde uyisebenzise yonke inkunkuma yawo, usebenzisa nje imichiza yendalo.

Ucinga ukuba umhlaba ukwazi njani ukuzihlaziya? UM. A. Corey⁵ umbhali ngezonqulo nenzululwazi uthi: “Ukuba le nkqubo yokuzihlaziya komhlaba yazivelela ngamabona-ndenzile, ibingenakuze isebenze ngokugqibelele ngolu hlobo.” Ngaba uvakalelwa njalo nawe?