Professor Neta Bahcall, a pioneering astrophysicist in the field of observational cosmology, and Eugene Higgins, a professor at Princeton University, will present evidence yielded by her research in two Patten lectures -- "The Dark Side of the Universe," Tuesday (Oct. 23), and "Will the Universe Expand Forever?" Thursday (Oct. 25). Both lectures will be held in Ballantine Hall, Room 109, at 7:30 p.m., and are free and open to the public.