Good talk given by Roger Penrose at Cambridge on 7 November 2005
topic was "Before the Big Bang"
and he said that only a couple of months earlier if someone had asked him he would have given the conventional answer that the question didn't make sense and there wasn't any "before"
if we can believe that, which could involve some striving for effect, then as recently as September 2005, Penrose would have said nothing before big bang, undefined.
but apparently now he has changed his mind----likes to talk about ideas of what was before the start of our universe expansion.
I heard him give the same talk in 2006, same slides, at MSRI Berkeley in 2006, and he also gave the talk at Perimeter in 2006.
great thing about this talk is his handdrawn pictures. good cartoonist. helps you understand both cosmology and thermodynamics in a more visual intuitive way
incredible what some people can do with just 3 or 4 different colors of felt-tip pen