A very enjoyable talk, which comes complete with all those great Penrose drawings. The talk is primarily focused on approaches to time asymmetry in quantum gravitational theories. Rather than starting from a theory-up approach, this looks for cracks in standard quantum mechanics and general relativity which could let us understand where time asymmetry could spring from.

If you've read either of his two famous books, you'll know that he looks for clues in the measurement problem. The talk muses about Schrödinger's cat, moves into a very nice description of the Lucien Hardy formulation of the problem, and then goes on to propose a possible experimental arrangement to test what he is talking about (FELIX). I particularly liked his example of what I'll call "Penrose's pendulum", a variation of the cat's situation, which also well highlights the possible connection to gravity and spacetime geometries.

The talk is not very mathematical, but if you're not a student of physics, it may be hard to follow the reasons for what he says. The slides seemed to be shuffled around a bit during the talk, and if you're not on a high-speed line you may want to cache them before starting the talk. (Since you can download the audio file, you may just want to download the whole thing and then play it at your leisure.) Unfortunately, there either was no question and answer session at the end or it wasn't recorded.

Expected background for talk:
Familiarity with the need for quantum gravity helps. A familiarity with non-relativistic quantum mechanics, general relativity and cosmology is needed. (The bulk of the math is surrounding quantum mechanics.)