The talk was very good, thank you for the link. The Penrose book is also quite good, i especially enjoyed his views on relativity - although the Penrose concept of a "popular level" book is not the normal Greene, Wheeler, Susskind "popular level"
In the Q&A session a question was raised...
I am one of those "amateurs", (not 90, but a young 70). who found Prof. Susskind lectures quite informative. At one point in the lectures (quantum entanglement) there was a survey of both ages and experience. I was about the middle, good math training and experience but little physics, mostly...
An interesting approach http://www.calphysics.org/zpe.html" found on the CalPhysics site suggests that the gravitational effects of the vacuum field have a phase cutoff point. This allows the large, but constant energy field while limiting the gravitational effect (otherwise we would collapse...