IsiGwinqa

isiGwinqa siyindawo emkhathingeni lapho umNyondo unamandla kangangokuba akunanto engakwazi ukuphunyuka noma ukuphuma kuso, ngisho Izinhlayiyana noma iMiyonzi yeNzubawonga ("electromagnetic radiation") enjengokukhanya uqobo azikwazi ukuphuma esiGwinqeni. Kukhona imbulunga ezungeze isigwinqa. Noma yini engena kuyo soze iphume. Lembulunga iwumngcele ongabalekwa futhi yaziwa ngokuthi umkhawulo wesehlo. Isigwinqa simnyama ngenxa yokuthi sigwinya konke ukukhanya okusondela kuso, futhi asikukhwentuzi sikubuyisele emuva.  
Ngaphansi kobuNguxa boMngako iziGwinqa zinamazinga okushisa futhi zikhafula imiyonzi kaHawking okunzima okuyihlonga ngokuqondile, kodwa lokhu kwenza iziGwinqa zibe zincane.

Izindikimba ezisemkhathini lezo umnyondo wazo unamandla kakhulu ukuba ukukhanya kungaphunyuka zaqala ukunakwa ekhulwini le-18 ngu-John Michell no-Pierre-Simon Laplace. Ngonyaka we-1916, u-Karl Schwarzschild wathola isixazululo sokuqala sanamuhla sesimelana jikelele (general relativity) esasizogagula isiGwinqa. U-David Finkelstein, ngonyaka we-1958, washicilela okokuqala inhlakahlo "yesiGwinqa" njengesifunda somkhathinga okungaphunyuki lutho kuso. Izigwinqa sekuyisikhathi zithathwa njengelukuluku lezibalo; kuze kwaba seminyakeni yowe-1960 ukuthi umsebenzi walowombono uqale uveze ukuthi kwakumane kuyizibikezelo zesimelana jikelele. Ukuvubukulwa kwenkanyezi eyintunge (neutron star) ngu-Jocelyn Bell Burnell ngowe-1967 kwavuselela intakaso ezindikimbeni ezihlangene zokuwohloka komnyondo njengesimo soqobo sasemkhathini. Isigwinqa sokuqala esaziwa ngokuthi Cygnus X-1, sahlonzwa abacwaningi abambalwa ngowe-1971.