Bell Lecture

The physics of life: How much can we calculate?

William Bialek

Princeton University

Theoretical physics is the search for compelling, compact, and unified mathematical descriptions of the world around us. For more than a century, this search has been guided as much by aesthetics as by observation, by the radical hypothesis that the world is a much simpler place than it might have been. Modern biology, in contrast, is a grand celebration of the remarkable complexity and diversity of life on earth. Dramatic improvements in experimental technique have uncovered previously unimagined themes and variations in the mechanisms of life, on every scale from molecules to ecosystems. Given these very different intellectual trajectories, can we envision a theoretical physics of life? Can there be abstract, unifying principles, in the physics tradition, that engage with the complexity and particularity of each biological system? Not so long ago, the answer to these questions - from both the physics and biology communities - was a resounding “no.” Today, things have changed. We have glimpses of success, where abstract physical principles, expressed in precise mathematical form, are shedding new light on diverse biological systems. In this lecture I'll try to convey some of this excitement, drawing on examples that range from the development of a fruit fly embryo to the flocking of birds, and from vision in insects to learning in humans.