Ralph Lewis Knowles (December 9, 1928 – August 23, 2024) was an American academic who was a professor emeritus of architecture and a leading theorist of solar access design.

[3] In 1962, Knowles applied for a Graham Foundation grant to support his research on natural forces.

The research hypothesis was that “A building made in balanced response to natural forces will exhibit differentiation useful for essential orientation in the urban landscape.” Knowles organized the natural forces laboratory at USC, and collaborated with noted architects and educators, including Pierre Koenig, Emmett Wemple, Konrad Wachsmann, Karen M. Kensek and Douglas E. Noble.

Though officially retired, Knowles continued to participate at USC as a studio advisor and research consultant in the Chase L. Leavitt Graduate Building Science program.

In September 2016, The Graduate School of Design (GSD) at Harvard University conducted a conference titled "heliomorphism" based on the work of Knowles.