Sara Walker is a theoretical physicist and astrobiologist working new theory of physics that might allow us to understand what life is, its general characteristics, its origin on Earth, and how to find alien examples. At Arizona State University she is the deputy director of the Beyond Center for Fundamental Concepts in Science, associate director of the ASU-SFI Center for Biosocial Complex Systems, and associate professor in the School of Earth and Space Exploration and the School of Complex Adaptive Systems. She is also an external faculty member at the Santa Fe Institute.