Physics discussion ends in skateboard attack SOUTH SAN FRANCISCO

A homeless man is on trial in San Mateo County on charges that he smacked a fellow transient in the face with a skateboard as the victim was engaged in a conversation about quantum physics, authorities said Wednesday.

Jason Everett Keller, 40, allegedly accosted another homeless man, Stephan Fava, on the 200 block of Grand Avenue in South San Francisco about 1:45 p.m. March 30.

At the time, Fava was chatting with an acquaintance, who is also homeless, about "quantum physics and the splitting of atoms," according to prosecutors.

Keller joined in the conversation and, for reasons unknown, got upset, authorities said. He picked up his skateboard and hit Fava in the face with it, splitting his lip, prosecutors said.

Fava also fell and broke his ankle, although how this happened wasn't known, authorities said.