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Sara Walker is a theoretical physicist who studies the origins of life and the author of Life as No One Knows It. As AI prompts us to rethink what consciousness, intelligence, and life really mean, Sara’s work offers a provocative framework for understanding these questions. In this conversation, Sara shares how she developed assembly theory—a revolutionary approach suggesting that complex objects like DNA molecules (and even microphones) are evidence of life’s processes.
We explore:
Why Sara believes we need entirely new laws of physics to understand life
How assembly theory quantifies the transition from non-life to life with a measurable threshold
Why complex objects like DNA and microphones are evidence of evolutionary processes
How our perception of objects as “physical” or “abstract” depends on their temporal scale
Why traditional definitions of life fail as scientific frameworks
How assembly theory could revolutionize our search for extraterrestrial life
The surprising connection between urban atmospheres and biosignatures
Why Sara sees fundamental differences between computation and physical construction
How assembly theory views AI systems and large language models
The creative parallels between theoretical physics and conceptual art
Explore the episode
Timestamps
(00:00) Intro
(03:32) Sara’s background and approach to studying the origins of life
(08:21) Sara’s journey to theoretical physics
(11:40) How the “origin of life” field has evolved since she began her research
(17:35) Introduction to assembly theory and its core principles
(23:11) How assembly theory differs from traditional definitions of life
(25:53) The historical parallels between assembly theory and Newtonian physics
(31:45) Life vs. alive
(34:33) How dabbling across disciplines led to Sara’s focus and partnership with Lee Cronin
(40:43) The connection between theoretical physics and art
(42:32) The probabilistic nature of assembly theory’s threshold
(45:05) The time–size continuum
(48:06) New threads that have emerged after Life as No One Knows It
(50:27) Why assembly theory may be our best tool for finding life beyond Earth
(54:04) The second feature of assembly theory: the copy number
(55:39) The challenges of detecting life on exoplanets versus in our solar system
(01:00:50) How recent AI developments have impacted Sara’s thinking about life
(1:05:48) Whether large language models qualify as “life”
(1:13:05) Final meditations
Follow Sara Walker
LinkedIn: https://www.linkedin.com/in/saraimariwalker
Resources and episode mentions
Books
Life as No One Knows It: The Physics of Life's Emergence: https://www.amazon.com/Life-No-One-Knows-Emergence/dp/0593191897
The Beginning of Infinity: Explanations That Transform the World: https://www.amazon.com/Beginning-Infinity-Explanations-Transform-World/dp/0143121359
People
Lee Cronin on X: https://x.com/leecronin
Judea Pearl: https://en.wikipedia.org/wiki/Judea_Pearl
Paul Davies on LinkedIn: https://www.linkedin.com/in/paul-davies-33634114/
Michael Lachmann on X: https://x.com/mikha_ehl
Benjamin Bratton’s website: https://bratton.info/
Other resources
Are We Alone In The Universe? Sara Seager on Exoplanets, Venus, and the Hunt for Alien Life (Astrophysicist and Planetary Scientist at MIT): https://www.generalist.com/p/are-we-alone-in-the-universe-sara-seager
Enceladus: https://en.wikipedia.org/wiki/Enceladus
Definitions of Life by Carl Sagan: http://www.aim.univ-paris7.fr/enseig/exobiologie_PDF/Biblio/Sagan%20Definitions%20of%20life.pdf
Life ≠ alive: https://aeon.co/essays/what-can-schrodingers-cat-say-about-3d-printers-on-mars
Little black dress: https://www.metmuseum.org/art/collection/search/83616
Dragonfly: https://science.nasa.gov/mission/dragonfly/
Universal Turing machine: https://en.wikipedia.org/wiki/Universal_Turing_machine
Von Neumann universal constructor: https://en.wikipedia.org/wiki/Von_Neumann_universal_constructor
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