COSMIC TIME LINE FROM THE DARK AGES After the emission of the cosmicmicrowave background radiation (about 400,000 years after the big bang) the universe grew increasingly cold and dark. But cosmic structure gradually evolved fromthe densky fluctuat ions left over from the big bang 1210 14 BIL UON YEARS I BILUON YEARS 100 MILLION YEARS MILLION YEARS Emission ol cosmic background radiation Dark ages First stars TO THE RENAISSANCE Firstsupemovae and black holes The appearance of the first stars and protogalaxies Protogalaxy (perhaps as early as 100 million years after the big bang set off mergers achain of events that transforme d the universe Modem galaxies