“Agora” is a historical epic that depicts the eternal struggle between science and ideology.The central storied figure driving the drama is the celebrated mathematician and astronomer Hypatia ( Rachel Weisz); an isosceles love triangle forms as one of her students (later a high official) and one of her slaves (later a religious extremist) pine for her. “Agora” is a visually imposing, high-minded epic that ambitiously puts one of the pivotal moments in Western history onscreen for the first time. Alejandro Amenabar’s first feature since “The Sea Inside” five years ago foreshadows the transformation of the Roman-dominated ancient world into Christian medieval times . “Agora” has more on its mind than most costume pictures, and most other films, for that matter — mankind’s place in the universe, the human need to understand the cosmos and the debate over the existence of a single deity.