I ran Terry's camera for the ISEPP presentation again, from high on the speaker's right, dress circle level.
Sir Roger Penrose was our in-front-of-the-camera talent, running two partially overlapping overhead projectors, quickly flipping back and forth from diagram to diagram, building a model of an eternally regenerative Universe, of cosmic constant lambda > 0.
In Penrose's latest proposal, the ultra low entropy constraints of the Big Bang are perhaps associated with zero Weyl Curvature (an hypothesis), Ricci Curvature being the other curvature of interest in this namespace.
But this same zero curvature might obtain when all future singularities (black holes) had rattled away their Hawking radiation, like so many kernels of popcorn, turning their last residual bits of mass into pure light energy.
At this point, with everything photons, all sense of time and space is rendered meaningless, and a kind of recalibration or rescaling might take place, such that our now prefrequency, isotropic, limiting special case might once again show up as a low entropy singularity with zero Weyl curvature -- and another Big Bang gives birth to another gravitational economy, ready to take it from the top.
Downhill = our direction of increasing entropy, per the 2nd Law, although on Planet Earth we're locally permitted an uphill ride on the solar gradient, with "clever plants" impounding high energy photons for the local food chain. We rebroadcast away the energy we didn't use.
Back to zero curvature, there might even be some gravitational rippling connecting one universe to a next. Penrose proposes yet another particle, charged, yet massless, to add some weight to his ideas.
Like any good scientist, Sir Roger builds falsifiable conditions into his pet theories. It's better to bow out with integrity, knowingly wrong, than it is to indefinitely linger as a hungry ghost, with some irrefutably baseless theory (i.e. all tautologies or truisms) -- and no fans.
During Q&A afterward, some of the most earnest questions came from children. He'd held them spellbound for like two hours. The two-overheads approach, with mostly hand-crafted content, is quite simple yet effective in a retro kind of way -- all those little light cones become almost iconic (9 parameters describe their shape, their angles, with only the 10th providing a sense of scale, or frequency).
Our dinner was on the 4th floor of the Performing Arts Center, overlooking a wet Broadway, with lots of flashing, reflecting light for atmosphere (big windows). The salmon with potatoes dish was excellent.
I asked no questions of Sir Roger -- although I did get his autograph in my copy of his latest book, at which time I mentioned I'd be his cameraman for the evening.
I wore my Class of 1980 Princeton reunion shirt -- little Nassau Halls in a pattern. If I'd had a Penrose tiles dress shirt, I could've worn that instead. I enjoy clowning around a little, when afforded an opportunity.