EntityQ467736· pop 32· linked from 359 articlesFriedmann equationsSign in to saveset of ordinary differential equations governing cosmic expansion in a homogeneous and isotropic universeConnectionsscale factorEntitymass–energy equivalenceEntitybaryonEntityAlexander FriedmannEntityWilkinson Microwave Anisotropy ProbeEntitystress–energy tensorEntityMinkowski diagramEntityAlbert EinsteinPersonIsaac NewtonPersonGalileo GalileiEntitySaint PetersburgCityhydrogenEntityuniverseEntityNicolaus CopernicusEntityBlack holeConceptStephen HawkingPersongravityEntityXi JinpingPersonJohannes KeplerEntityNASAConceptCategoriesGeneral relativity