David Saltzberg, a professor of physics and astronomy at the University of California, Los Angeles, checked scripts and provided dialogue, mathematics equations, and diagrams used as props. According to executive producer/cocreator Bill Prady, "We're working on giving Sheldon an actual problem that he's going to be working on throughout the [first] season so there's actual progress to the boards... We worked hard to get all the science right." Saltzberg, who has a Ph.D. in physics, served as the science consultant for the show for six seasons and attended every taping. He saw early versions of scripts that needed scientific information added to them, and he also pointed out where the writers, despite their knowledge of science, had made a mistake. He was usually not needed during a taping unless a lot of science, and especially the whiteboard, was involved.