"Friedman had suffered health problems over the years. But news of his death stunned friends and colleagues, including UCSD physicist Brian Keating, who recruited him to , and physicist-science fiction author of . The trio made up “The Three Physicists,” an informal group that periodically met to give public talks on science and philosophy. ... With Brin and Keating, he also dove into esoterica, tackling subjects such as the physics of free will."