Solar energy is attracting considerable national attention as a potential new option in the search for energy alternatives for the future. The dream of the use of solar energy is not new. Since solar energy interest has grown and waned in the past one immediately wonders what might be new this time that would lead to success. Do the problems encountered in the past still hold today? If not, what is new that could make solar energy a practical reality? I would like to address this question in some detail under the title of this session: Optical Interfaces; since there obviously is a very important role for optical technology in solar energy, ranging from optical collectors to solid-state physics, but first, some background should be presented.