I've seen shows on the Science Channel and Discovery Channel that say at the Big Bang there could have been a lot of energy and this later condensed into matter, via [tex]E=mc^2[/tex]. Is this true? If so, exactly how would that work? Would it be by collisions between photons or something.. ? Surely light propagating through space doesn't just spontaeously condense the way radioactive elements can spontaneously transfer part of their mass into energy..