I do a fair amount of rock climbing, which provides an important balance in my life. Climbing helps me to brainstorm about research and to escape from it. I do a variety of bouldering, sport, and trad (and in a past life I was a routesetter at the Stanford Climbing Wall). You can find fairly comprehensive lists of what I've climbed on my Mountain Project, and some highlights here.
For example, here is a series of pictures showing Dan Birman and me as a few pixels, while we were climbing Gift of the Wind Gods.
And here are some more assorted pictures from various climbing trips. Click an image for more info on the climb!
Covid was not good for much, but it did get me to climb more at my local crag (Castle Rock) since all the gyms closed.