Physics learning involves a change in the habitual perception of the everyday world. In order to describe the real world scientifically, an individual must develop perception and cognition capable of reconstructing the world from raw sensory data and incorporating acquired knowledge of the scientific community. The introductory physics student struggles to "see" the invisible filters of conventional physics ideas that most physicists take for granted. This paper draws on several theories of perception and imagery to explore experiences with the invisible world of physics. Discussion includes: generation of images as a route to understanding physics; internal physics imagery and physics thinking; viewing light as a particle or wave; the speed of light; and illustrating the speed of sound and black holes with visual metaphors. Nine figures illustrate various physics concepts. (Contains 11 references.) (AEF)