I have a foggy memory of being at a hotel bar after some physics conference reception, and drinking next to Roger Penrose. He let us youngsters explain our research to him, which I think included explaining how pulsar timing can detect gravitational waves. 1/

I feel like he already knew how pulsar timing worked, but it's also possible he didn't. Either way, it was very kind of him to humor us young physicists and let us explain something to him! 2/

It's hard to overstate how much of GR research Penrose has touched. It's not just the formation of singularities, it's also the causal structure of spacetime (including event horizons), the asymptotic structure, spinors in spacetime, and so much more. 3/

One main quality that made Penrose so influential is his ability to make lucid a complicated concept. If you open up some of his books, they're packed full of beautifully illustrated diagrams that make the concepts click (at least for me, I'm a very geometric/visual person) 4/

And of course he's had contributions beyond black hole physics -- like the aperiodic Penrose tilings of the plane -- which are not recognized by this Nobel. He's just been absolutely prolific. 5/

(Let's just ignore Conformal Cyclic Cosmology, Penrose's vast contributions will give him a pass on that one, right?)