COMPLEXITY: Physics of Life

Sara Walker on The Physics of Life and Planet-Scale Intelligence

Episode Notes

What is life, and where does it come from? These are two of the deepest, most vexing, and persistent questions in science, and their enduring mystery and allure is complicated by the fact that scientists approach them from a myriad of different angles, hard to reconcile. Whatever else one might identify as universal features of all living systems, most scholars would agree life is a physical phenomenon unfolding in time. And yet current physics is notorious for its inadequacy with respect to time. Life appears to hinge on information transfer — but, again, what do we mean by “information,” and what it is relationship to energy and matter? If humankind can’t settle fundamental issues with these theoretical investigations, we might be missing other kinds of life (and mind) — not just in outer space, but here on Earth, right beneath our noses. But new models that suggest a vastly wider definition of life offer hope that we might — soon! — not only learn to recognize the biospheres and technospheres of other living worlds, but notice other “aliens” at home, and even find our place amidst a living cosmos.

Welcome to COMPLEXITY, the official podcast of the Santa Fe Institute. I’m your host, Michael Garfield, and every other week we’ll bring you with us for far-ranging conversations with our worldwide network of rigorous researchers developing new frameworks to explain the deepest mysteries of the universe.

This week on the show, we speak with SFI External Professor Sara Walker (Twitter, Google Scholar), Deputy Director of The Beyond Center at ASU, where she acts as Associate Professor in half a dozen different programs. In this conversation, we discuss her pioneering research in the origins of life and the profound and diverse implications of Assembly Theory — a new kind of physics she’s developing with chemist Leroy Cronin and a team of SFI and NASA scholars.  Sara likes to speculate out loud in public conversation, so strap in for an unusually enthusiastic, animated, and free-roaming conversation at the very bleeding edge of science. And be sure to check out our extensive show notes with links to all our references at

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Mentioned Papers:

Intelligence as a planetary scale process
by Adam Frank, David Grinspoon & Sara Walker

The Algorithmic Origins of Life
by Sara Imari Walker & Paul C. W. Davies

Beyond prebiotic chemistry: What dynamic network properties allow the emergence of life?
by Leroy Cronin & Sara Walker

Identifying molecules as biosignatures with assembly theory and mass spectrometry
by Stuart Marshall, Cole Mathis, Emma Carrick, Graham Keenan, Geoffrey Cooper, Heather Graham, Matthew Craven, Piotr Gromski, Douglas Moore, Sara Walker & Leroy Cronin

Assembly Theory Explains and Quantifies the Emergence of Selection and Evolution
by Abhishek Sharma, Dániel Czégel, Michael Lachmann, Christopher Kempes, Sara Walker, Leroy Cronin

Quantum Non-Barking Dogs
by Sara Imari Walker, Paul C. W. Davies, Prasant Samantray, Yakir Aharonov

The Multiple Paths to Multiple Life
by Christopher P. Kempes & David C. Krakauer 

Other Related Videos & Writing:

SFI Seminar - Why Black Holes Eat Information
by Vijay Balasubramanian

Major Transitions in Planetary Evolution
by Hikaru Furukawa and Sara Imari Walker

2022 Community Lecture: “Recognizing The Alien in Us”
by Sara Walker

Sara Walker and Lee Cronin: The Alien Debate
on The Lex Fridman Show

If Cancer Were Easy, Every Cell Would Do It
SFI Press Release on work by Michael Lachmann

The Ministry for The Future
by Kim Stanley Robinson

Re: Wheeler’s delayed choice experiment

On the SFI “Exploring Life’s Origins” Research Project

Complexity Explorer’s Origins of Life Free Open Online Course

Chiara Marletto on Constructor Theory

Simon Saunders, Philosopher of Physics at Oxford

Related SFI Podcast Episodes:

Complexity 2 - The Origins of Life: David Krakauer, Sarah Maurer, and Chris Kempes at InterPlanetary Festival 2019

Complexity 8 - Olivia Judson on Major Energy Transitions in Evolutionary History

Complexity 17 - Chris Kempes on The Physical Constraints on Life & Evolution

Complexity 40 - The Information Theory of Biology & Origins of Life with Sara Imari Walker (Big Biology Podcast Crossover)

Complexity 41 - Natalie Grefenstette on Agnostic Biosignature Detection

Complexity 68 - W. Brian Arthur on Economics in Nouns & Verbs (Part 1)

Complexity 80 - Mingzhen Lu on The Evolution of Root Systems & Biogeochemical Cycling

Alien Crash Site 015 - Cole Mathis

Alien Crash Site 019 - Heather Graham

Alien Crash Site 020 - Chris Kempes

Alien Crash Site 021 - Natalie Grefenstette