Big Bang –creation of universe
•Our cosmic particle horizon = how far can we detect phenomena within age of universe
•Rhoriz = tuniv x c
•Can’t see stars further than 14 Blyrs
•& redshifts decrease photon energy (even harder to detect)
•Horizon increasing
•Planck time tp =( Gh/c5)1/2
= 1.35
x 10-43 secs time, space behave as today
Between Big Bang and Planck time nothing known