She arrived like someone from another time, adorned in celestial jewelry, butterfly rings fluttering at her fingers, and an easy, mischievous smile that hinted at mysteries she’d long since made peace with. On April 1st, 2025, at The Interval of the Long Now in San Francisco, a place built for slow thinking and long perspectives, Sara Imari Walker sat across from me and began to unravel the universe.
Sara is one of those rare thinkers who makes the cosmos feel not vast and indifferent, but intimate, alive, even. A physicist by training, she spends her days probing one of the most elusive riddles in science: what exactly is life, and how does it begin? But that’s just the start. Her work reaches far beyond biology or chemistry. Through her development of assembly theory, a framework that attempts to quantify how complex structures come into being, she is carving out nothing less than a new science of emergence.
You get the sense, speaking with her, that the big questions aren’t intimidating to her. They’re magnetic. She describes the universe not as a machine grinding out configurations of matter, but as something more like a poem, or a growing organism. She believes that life is not a cosmic accident but a phenomenon that the universe is, in some sense, biased toward. And while that might sound like philosophy, in Sara’s hands it becomes a set of testable hypotheses, a roadmap for exploring alien biospheres, both real and imagined.
Her background is as eclectic as her intellect. Born with one foot in physics and the other in philosophy, she has made it her mission to collapse the artificial walls between disciplines. She studied theoretical physics in graduate school, but her thinking has always veered into the biological, the informational, the metaphysical. She joined the astrobiology program at Arizona State University, where she now serves as a professor, and she is one of the central figures in NASA’s efforts to define and detect life beyond Earth.
But titles and institutions can only gesture at what makes her work so resonant. Sara is, above all, a synthesizer. She pulls from thermodynamics, evolutionary theory, information science, and even metaphysics to offer a new view of life, not just as a biological category, but as a fundamental feature of reality. Her work has led her to propose that life’s most essential feature is not replication, but memory, systems that retain the past in order to shape the future. It’s a view of the universe that is not frozen and fixed, but open-ended, historical, and creative.
During our session, she picked up a small globe, a prop for the photo, perhaps, but in her hand it became something more: a symbol of the fragility and improbability of everything we know. She looked at it thoughtfully, then glanced back with that same bright smile. “It’s all just matter,” she said, “but not just. It’s matter with history.”
It’s that poetic clarity that defines her. In a field often defined by technical jargon or reductionist thinking, Sara insists on seeing the whole system, and on asking the hardest questions with both rigor and imagination.
The photograph we made together captures something essential about her. Dressed not in the muted tones of the academic, but in bold textures, dark velvet, spiked bracelets, a necklace that looked like a model of spacetime itself, she evokes both the depth of space and the strange beauty of the things that emerge from it. It’s not just an aesthetic choice. It’s a declaration: that science can be sensuous, that big ideas deserve beauty.
Sara Imari Walker is building nothing less than a new cosmology, one in which life is not a footnote to physics, but the main event. She invites us to see ourselves not as anomalies, but as participants in a much larger unfolding. In her universe, we are not isolated observers, but expressions of the same generative force that built stars, molecules, and meaning. And in that universe, there is room for both wonder and understanding.
