Dear PF Forum, I have read a link about big bang time line. Started from time zero, then Baryogenesis, lepto genesis, planck time then on... http://www.physicsoftheuniverse.com/topics_bigbang_timeline.html I try to make a simple calculation here with Schwarzschild calculator. The mass of the universe is: 1053Kg. Schwarzschild radius: 1.486 x 1026 So at T+20 minutes after big bag, the radius of the universe is: 1.8 x 107Km All these mass is packed at that radius, defintely below Schwarzshild Radius. How can all that mass continued to spread out much less for millions of year. What triggered that expansion? And if I imagine what sphere is 20 minutes light year with that mass compared to Neutron Star. A 2 solar mass neutron star is about 10 km in diameter, this is very roughly. In 20 minutes light speed, the sphere could be packed by... (1.8 x 107/5)3 = 4.66 x 1019 neutron stars. And the number of stars in the universe if a galaxy has roughly 100 billions stars in 100 billions galaxy is 1022. So the sphere is much denser than neutron star?