A 1900 photograph shows Yerkes Observatory, on Lake Geneva in Wisconsin, in 1900. The observatory was dedicated 125 years ago, in 1897. Yerkes housed the world's largest working refracting telescope (dome at right), which uses lenses to bring starlight into focus. The observatory pioneered the new field of astrophysics, which studies the physical properties of stars and other objects to learn how they work. Yerkes was operated by the University of Chicago until a few years ago, when it was sold to become an education, outreach, and events center. [Wikipedia]