Originally Posted by
Psionik
Spock It was 300k-400k years like Sageous said... I think it was somewhat similar to condition inside stars. Thermonuclear fusion is possible only in core. It generates very hard electromagnetic rays and bunch of different particles like neutrinos, neutrons... But since plasma is so dense the path of photons is very short. It is absorbed, then emitted in many times (photon can penetrate millimetres before it is again absorbed) while energy goes through hundreds of thousands kilometers of ionized matter. It was calculated that it can take many thousands of years till energy is released from Sun.
But neutrinos decoupled from the matter a few seconds after bigbang... If we would be ever capable to observe those relic neutrinos(very low energy neutrinos :( ) we will be able to see Universe at that stage...