Izinto eziphilayo emhlabeni bezingeke zibe khona ngaphandle “kwezenzakalo ezathuka zenzeka,” ezinye zazo ezazingaziwa noma zingaqondakali ngokuphelele kwaze kwaba sekhulwini lama-20. Lezi zenzakalo zihlanganisa lezi ezilandelayo:

• Indawo umhlaba okuyo emthaleni iMilky Way nasesimisweni sikanozungezilanga, ukujikeleza kwawo, ukutsheka kwawo, ijubane lokujikeleza kwawo nenyanga

• Amandla kazibuthe kanye nomkhathi oyisivikelo esikabili

• Imijikelezo engokwemvelo evuselela futhi ihlanze umoya kanye namanzi

Njengoba ufunda ngasinye salezi zihloko, zibuze: ‘Ingabe izinto ezisemhlabeni zavela ngengozi noma zaklanywa ngenjongo?’

Uma ubhala ikheli lakho, yini oyibhalayo? Ungase ubhale izwe ohlala kulo, idolobha nomgwaqo. Ngomqondo ongokomfanekiso, ake sibize umthala iMilky Way umhlaba okuwo ngokuthi “izwe,” isimiso sikanozungezilanga—ilanga namaplanethi alo—kube “idolobha” bese umzila umhlaba ojikeleza kuwo esimisweni sikanozungezilanga kube “umgwaqo.” Ngenxa yentuthuko kwezokuhlolwa kwezinkanyezi nesayensi yemvelo, ososayensi sebeziqonda kangcono izinzuzo zokuba umhlaba ube sendaweni okuyo.

Okokuqala nje, “idolobha” lethu, noma isimiso sethu sikanozungezilanga, lisendaweni ekahle emthaleni iMilky Way—alikho eduze kakhulu nenkaba yomthala futhi aliqhelile kakhulu. Le ndawo, ososayensi abayibiza ngokuthi “indawo okuhlaleka kuyo,” inesilinganiso esifanele samakhemikhali adingekayo ukuze isekele ukuphila. Emaphethelweni omthala, lawo makhemikhali ayimbijana; ekujuleni komthala, indawo iyingozi kakhulu ngenxa yobuningi bemisebe ebulalayo nezinye izinto. Umagazini i-Scientific American uthi: “Sihlala endaweni enhle kakhulu.”¹

“Umgwaqo” ofanelekayo: Enye indawo “enhle” kakhulu “umgwaqo” womhlaba, noma umzila ozungeza kuwo “edolobheni” lethu lesimiso sikanozungezilanga. Lo mzila oqhele ngamakhilomitha angaba izigidi ezingu-150 elangeni, usendaweni okuhlalekayo kuyo engabandi kakhulu futhi engashisi kakhulu. Ngaphezu kwalokho, umzila womhlaba ucishe ube isiyingi, usigcina siqhele cishe ngebanga elifanayo elangeni unyaka wonke.

Ilanga lona liwumthombo wamandla omangalisayo. Lihlala lishisa, lilingene ngobukhulu futhi likhipha isilinganiso esifanele samandla. Libizwa ngokufanelekile ngokuthi “inkanyezi ekhetheke kakhulu.”²

“Umakhelwane” ofanele: Ukube ubungakhetha “umakhelwane” womhlaba, akekho obengaba ngcono kunenyanga. Ubukhulu bayo bungaphezudlwana kwengxenye  eyodwa kwezine yobukhulu bomhlaba. Ngakho, uma iqhathaniswa nezinye izinyanga ezisesimisweni sethu sikanozungezilanga, inyanga yethu inkulu ngokungavamile uma kubhekwa iplanethi eseduze kwayo. Ingabe lokhu kwenzeka ngengozi? Cha.

Okokuqala, inyanga iyona ngokuyinhloko elawula ukuphakama nokubohla kwamagagasi olwandle, okufeza indima esemqoka ezintweni eziphilayo nendawo yazo. Inyanga yenza nokuba izisekelo zomhlaba zizinze. Ngaphandle kwale nyanga eklanywe ngokukhethekile, iplanethi yethu ibiyophenduphenduka njengethophi eselizokuwa, mhlawumbe ize igingqike! Izinguquko ebeziyoba khona esimweni sezulu, ekuphakameni kwamagagasi nakwezinye izinto beziyobangela inhlekelele.

Ukutsheka nokujikeleza komhlaba okumangalisayo: Ukutsheka komhlaba ngama-degree angaba ngu-23,4 kubangela ukushintsha kwezinkathi zonyaka minyaka yonke, kugcine amazinga okushisa esesilinganisweni futhi kwenze kube nesimo sezulu esishintshashintshayo. Incwadi ethi Rare Earth—Why Complex Life Is Uncommon in the Universe ithi: “Iplanethi yethu ibonakala itsheke ‘ngendlela efanele.’”³

Ukujikeleza komhlaba kwenza imini nobusuku kube kude “ngendlela efanele.” Ukube umhlaba ubujikeleza ngesivinini esiphansi kakhulu, izinsuku beziyoba zinde futhi uhlangothi olubheke elangeni beluyoshisa kakhulu kanti olungalé beluyoba iqhwa. Ngakolunye uhlangothi, ukube umhlaba ubungajikeleza ngesivinini esikhulu kakhulu, izinsuku bezingaba mfushane, mhlawumbe zibe amahora nje ambalwa, futhi lokho bekuyobangela izivunguvungu nezinye izingozi.

Umkhathi uyindawo eyingozi egcwele imisebe ebulalayo nezinguzunga zamatshe atshuzayo. Kodwa kubonakala sengathi iplanethi yethu eluhlaza okwesibhakabhaka ayinankinga yokuhamba kulesi “siminyaminya sezinto ezitshuzayo” emkhathini. Ngani? Ngenxa yokuthi umhlaba unesivikelo esimangalisayo—amandla kazibuthe amakhulu kanye nomkhathi oklanywe ngendlela ekhethekile.

Amandla kazibuthe omhlaba: Inkaba yomhlaba iyibhola lensimbi encibilikile eliphenduphendukayo, elibangela ukuba umhlaba ube namandla amakhulu kazibuthe afinyelela emkhathini. Lesi sivikelo sisivikela emisebeni enamandla evela emkhathini nasemisebeni yelanga ebingasibulala. Le misebe yelanga ihlanganisa ama-solar wind, ayithala elinganqamuki lezinhlayiya ezinamandla; ama-solar flare, akhipha amandla angalingana namabhomu e-hydrogen ayizigidi ngomzuzu; ukuqhuma okusemaphethelweni elanga noma i-corona, okukhiphela emkhathini izigidi zamathani ezinto ezihlukahlukene.  Ungabubona ubufakazi besivikelo osithola emandleni kazibuthe azungeze umhlaba. Ama-solar flare nokuqhuma okusemaphethelweni elanga kubangela imisebe yokukhanya enemibala egqamile ebonakala emkhathini emaphethelweni omhlaba lé enyakatho.

Umkhathi womhlaba: Lesi sembozo samagesi asenzi nje ukuba siqhubeke siphefumula kuphela, kodwa futhi siyisivikelo. Ingxenye yomkhathi engaphandle, okuthiwa i-stratosphere, inohlobo lomoya-mpilo okuthiwa i-ozone, olubamba cishe amaphesenti angu-99 emisebe ye-ultraviolet (UV) evela ngaphandle. Ngakho, ungqimba lwe-ozone luvikela izinhlobo eziningi zezinto eziphilayo—kuhlanganise nabantu nezilwanyana nezitshalo ezincanyana ezisikhiqizela umoya-mpilo—emisebeni eyingozi. Umthamo we-ozone esemkhathini awunasilinganiso. Kunalokho, uyashintshashintsha njengoba amandla emisebe ye-UV anda. Ngakho ungqimba lwe-ozone luyisivikelo esihle kakhulu.

Umkhathi usivikela ekulinyazweni nsuku zonke amatshe avela emkhathini, ashiyanayo ngobukhulu kusukela ezinhlayiyeni ezincane kuya ezinguzungeni ezinkulu. Iningi lala matshe liyasha emkhathini, libe ukukhanya okukhulu okuthiwa izinkanyezi ezitshuzayo. Nokho, izivikelo zomhlaba aziyivimbi imisebe esiyidingayo ukuze siphile, njengokushisa nokukhanya. Umkhathi womhlaba usiza nasekusabalaliseni ukushisa emhlabeni wonke, futhi ebusuku uba njengengubo ebamba ukushisa kungapheli masinyane.

Umkhathi womhlaba kanye namandla kazibuthe ngempela kuyimiklamo emangalisayo engakaqondakali ngokugcwele. Kungashiwo okufanayo nangemijikelezo esekela ukuphila kulo mhlaba.

Uma kungaphela umoya ohlanzekile namanzi edolobheni, kuvaleke namapayipi okukhuculula indle, ngokushesha kungalandela izifo nokufa kwabantu. Kodwa cabanga ngalokhu: Iplanethi yethu ayifani nendawo yokudlela, lapho kufika khona ukudla okusha nezinto ezidingekayo zivela ngaphandle, bese kukhishwa udoti. Umoya ohlanzekile namanzi esiwadingayo akufiki kuvela emkhathini, kanti nokungcola akukhishelwa ngaphandle. Pho umhlaba uhlala kanjani unempilo futhi ukulungele ukuba kuphilwe kuwo? Impendulo iwukuthi: kungenxa yemijikelezo yemvelo, njengomjikelezo wamanzi, wekhabhoni, womoya-mpilo nowe-nitrogen, echazwe lapha futhi yaboniswa ngendlela elula.

Umjikelezo wamanzi: Amanzi ayadingeka ukuze siphile. Akekho kithi ongaphila izinsuku eziningana ngaphandle kwawo. Umjikelezo wamanzi usinika amanzi ahlanzekile emhlabeni. Uhlanganisa izigaba ezintathu. (1) Ukushisa kwelanga kwenza amanzi ahwamukele emkhathini. (2) Lapho lo mhwamuko unqwabelana kwakheka amafu. (3) Amafu wona akhe imvula, isichotho, ungqoqwane noma iqhwa elikhithikayo, elilungele ukuhwamuka futhi, kanjalo liphelelise lo mjikelezo. Angakanani amanzi ahamba kulo mjikelezo unyaka nonyaka? Ngokwesilinganiso, angamboza wonke umhlaba aze aphakame ngamasentimitha angu-80.⁴

Imijikelezo yekhabhoni nomoya-mpilo: Njengoba wazi, ukuze uphile kudingeka uphefumule, uhogele umoya-mpilo, ukhiphe isikhutha (carbon dioxide). Kodwa njengoba kunezigidigidi zabantu nezilwane eziphefumulayo, kungani umkhathi wethu ungaphelelwa umoya-mpilo futhi ugcwale isikhutha? Impendulo itholakala emjikelezweni womoya-mpilo. (1) Ngenqubo emangalisayo okuthiwa i-photosynthesis, izitshalo zimunca isikhutha esisikhiphayo, zisisebenzise kanye namandla avela elangeni ukuze zakhe ukudla okumahhadla (carbohydrates) nomoya-mpilo. (2) Lapho sihogela umoya-mpilo siqedela lo mjikelezo. Lokhu kukhiqizwa kokudla okumahhadla nomoya esiwuhogelayo kwenzeka ngendlela ehlanzekile, ephumelelayo futhi buthule.

 Umjikelezo we-nitrogen: Izinto eziphilayo emhlabeni zithembele nasekwakhekeni kwamangqamuzana emvelo anjengamaprotheni. (A) Ukuze kwakheke lawo mangqamuzana kudingeka i-nitrogen. Ngenhlanhla le-nitrogen yakha amaphesenti angu-78 omoya osizungezile. Umbani uguqula i-nitrogen esemkhathini ibe izakhi ezingase zimuncwe yizitshalo. (B) Izitshalo zona ziguqula lezi zakhi zibe amangqamuzana angokwemvelo. Izilwane ezidla lezo zitshalo zibe sezithola i-nitrogen. (C) Ekugcineni, lapho izitshalo nezilwane zifa, ama-bacterium ahlukanisa izakhi ze-nitrogen. Lezi zakhi ze-nitrogen ezihlukanisiwe zibuyela enhlabathini nasemkhathini, uphele kanjalo umjikelezo.

Nakuba abantu benezinto zobuchwepheshe eziphambili, minyaka yonke babangela inqwaba yemfucumfucu enobuthi engasebenziseki. Kodwa umhlaba unesimiso sokuphinde uyisebenzise yonke imfucumfucu usebenzisa ubunjiniyela bamakhemikhali obuwubunyoninco.

Ucabanga ukuthi isimiso somhlaba sokusebenzisa izinto kabusha saba khona kanjani? Umlobi wezenkolo nesayensi uM. A. Corey uthi: “Ukube isimiso semvelo soMhlaba sasibe khona ngengozi ngempela, besingeke sifinyelele izinga lokuphelela elihle kangaka elibangela ukuvumelana kwemvelo.”⁵ Ingabe uyavumelana nalesi siphetho?