Grimes and Mr. Musk made their public debut at the Met Gala in 2018, which had a Catholic theme. "She was wearing a head piece made of Vantablack, the blackest black that anything could be," he recalled to me. "There was only one person who noticed and that was Stephen Colbert. On the back of my tuxedo jacket -- which was sort of like an inverted priest jacket with the jacket being white and the collar being black -- I had in big, black, gothic script, "Novus ordo seclorum." I love how-people-met stories, but this was the wildest one I'd ever heard: Two famous people who thought they were crazy when they were little because there were so many off-the-wall ideas bursting out of their heads somehow found each other.

At a recent conference here of the American Association for Artificial Intelligence, robots competed to rescue dummies in a disaster mock-up, while a robot named George greeted attendees as they arrived. Dozens of teenagers -- a next generation of roboticists -- showed off their robot creations in a contest. Presentations by scientists ran from the esoteric ("Online Semantic Extraction by Backpropagation Neural Network with Various Syntactic Structure Representation" by Heidi Yeung of the City University of Hong Kong) to the practical topic du jour ("Intelligent Technology for Adaptive Aging," by the University of Michigan's Martha Pollack).