Sara Walker: Physics of Life, Time, Complexity, and Aliens | Lex Fridman Podcast #433

Added: Jun 14, 2024

Defining Life

Walker challenges traditional definitions of life, pointing out the limitations and contradictions in commonly used definitions such as life as a self-reproducing system or life as a self-sustaining chemical system capable of Darwinian evolution. She argues that these definitions fail to encompass the complexity and diversity of life forms, leading to a paradox in the search for alien life. She uses examples like the zombie ant fungus to illustrate the challenges in defining life, highlighting the intricate and interconnected nature of living organisms.

Expansive Definition of Life

Walker proposes a more expansive definition of life as the process of how information structures matter over time and space. She suggests that life is a dynamic and evolving phenomenon that transcends individual organisms, encompassing entire lineages and populations. By shifting the focus from individual entities to the larger causal structure of life on a planetary scale, she aims to capture the essence of life as a continuous and interconnected process.

Time as a Dimension

Walker explores the concept of time as a crucial dimension in understanding the nature of life. She argues that living objects are not only vast in space but also immense in time, with their evolutionary histories spanning billions of years. By visualizing time as a series of causal structures that shape the development of life forms, she suggests that a deeper appreciation of temporal dynamics can provide insights into the complexity and interconnectedness of living systems.

Technosphere

Walker introduces the concept of the technosphere as the global integration of life and technology on Earth. She emphasizes the symbiotic relationship between living organisms and technological advancements, highlighting the interconnectedness of these systems within the larger framework of the planet's evolutionary history. The technosphere represents a significant object in time, reflecting the collective impact of human civilization on the planet's ecological and social dynamics.

Visualizing Abstract Concepts

Walker reflects on the challenges of visualizing abstract concepts and translating complex ideas into words. She acknowledges the limitations of language in capturing the depth and complexity of scientific concepts, highlighting the importance of experimentation with words to convey nuanced meanings. By exploring the intersection of language, perception, and cognition, she seeks to bridge the gap between scientific understanding and human experience.

Origins of Life on Earth

Walker delves into the origins of life on Earth, proposing that the emergence of life is a boundary that the universe can only cross when a structure can reinforce its own existence through self-reproduction and autocatalysis. She explains that the transition to original life occurs when a system can maintain its own existence against randomness and chemical constraints, leading to the emergence of self-reinforcing structures that can persist over time.

The guest discusses the concept of autocatalytic sets, where objects in a system reinforce each other's existence, creating a closed loop that allows the entire structure to persist. She highlights the importance of causal constraints that enable the closure of loops in self-reinforcing structures, leading to the emergence of original life.

Walker uses the example of a self-reproducing malum ring to illustrate the concept of autocatalytic feedback in non-organic systems. She explains how the malum ring serves as a template for smaller structures, leading to a self-reinforcing system that can persist over time. The discovery of the malum ring sheds light on the mechanisms that drive the origin of life and the emergence of self-reinforcing structures in complex systems.

Chirality

Walker delves into the concept of chirality, which refers to the asymmetry between molecules and their mirror images. She explains that chirality breaks symmetry in time, not space, and that it is a fundamental feature of chemistry. She highlights that the transition to life occurs when molecules reach a certain level of complexity, leading to the formation of chiral molecules that can recognize each other and self-reinforce. This transition marks a boundary in chemical space where the universe shifts from a state where few molecules have mirror images to one where almost every structure is chiral.

Walker explains that chirality is a perplexing feature of life chemistry, where amino acids in proteins are left-handed, and bases in RNA and DNA are right-handed. She explores the phenomenon of symmetry breaking in chirality, where a system transitions from having chemistries that are equivalent to one-handedness dominating as the dominant form.

She shares her research on the origin of chirality, highlighting the significance of symmetry breaking in understanding the emergence of handedness in biological molecules. She emphasizes the importance of exploring the origins of chirality as a fundamental aspect of life chemistry and the role it plays in shaping the molecular structures essential for life.

The Great Inventions of Evolution

Walker discusses the ten great inventions of evolution, as outlined by Nick Lane in his book "Life Ascending." These inventions include the origin of life, DNA, photosynthesis, complex cells, sex, movement, sight, consciousness, and death. Walker finds sight particularly fascinating, as it allows organisms to perceive and comprehend the world around them. She also mentions the complexity of embryogenesis, where a single cell develops into a complex organism through a series of recursive steps.

The Assembly Theory and Complexity

Walker introduces the concept of the assembly theory, which quantifies the boundary in the space of all possible objects that could exist. She explains that the assembly index measures the complexity of an object based on the number of recursive steps required to create it. Walker and her team have experimentally validated that for organic chemistry, the assembly index is around 15 steps. Objects beyond this threshold are typically only observed in living organisms, indicating a transition in complexity that is crucial for life to persist and self-reinforce.

The Struggle for Existence

Walker reflects on the struggle for existence, a concept rooted in Darwinian evolution where organisms compete for survival. She highlights the significance of objects that never get a chance to exist, as each new structure generated excludes a vast space of possibilities. She explains that existence excludes many potential objects due to the accident of history and the causal chains that lead to the formation of complex structures. She emphasizes the role of randomness and determinism in shaping the objects that come into existence.

Language and Meaning

Walker explores the role of language in conveying complex ideas and concepts. She discusses how language is a compression mechanism that allows individuals to express their thoughts and convey meaning. She mentions the challenge of using language to describe new or abstract concepts, as existing words may not adequately capture the intended meaning. She highlights the importance of playing with words and language to convey nuanced ideas effectively.

Alien Life and the Expansion of Time

Walker contemplates the possibility of alien civilizations and the uniqueness of Earth's evolutionary process. She questions whether there are other structures in the universe that resemble the complex causal structure of life on Earth. She suggests that the expansion of the universe in time drives the growth of complexity and technology on Earth, leading to a virtualization of the planet. She visualizes Earth as a space packed with time and information, expanding in time while remaining constant in physical size.

Virtualized Reality and Time Crystals

Walker delves into the concept of virtualized reality, drawing parallels between virtual reality simulations and the deep temporal structures that underlie human existence. She discusses the idea of time crystals and how they could potentially isolate civilizations in the universe, leading to a sense of loneliness and separation.

Walker's concept of virtualized reality involves the idea that advanced civilizations may virtualize their reality, embedding themselves in deep temporal structures that separate them from the rest of the universe. She drew inspiration from theoretical physics and psychedelic experiences to explore the notion of civilizations existing as time crystals, isolated and imperceptible to others. This perspective raised questions about the nature of intelligent life and the potential for communication with alien civilizations.

Exploring the Space of Human Aesthetics

The conversation shifts to the exploration of human aesthetics, with Walker highlighting the vast and complex constructible space of human aesthetics. She emphasizes the role of fashion as a dynamic and expressive form of art, reflecting individuality and creativity. She shares her personal experience of using fashion as a means of self-expression and experimentation, viewing it as an intellectual pursuit that bridges different layers of human culture.

Life and Consciousness

Walker delves into the relationship between life and consciousness, questioning which one comes first. She suggests that consciousness is a result of being a temporally extended object, with a deep structure in time that allows for a unique conscious experience. She views consciousness as a manifestation of the vast amount of time rolled up in an individual, leading to a separate thread in time that distinguishes one's conscious experience from others.

Intelligence and Artificial Intelligence

When discussing intelligence and artificial intelligence, Walker draws parallels between the evolution of genomes and the evolution of language. he likens large language models to genetic systems for language, storing the collective intelligence of the human species in a dynamic and evolving manner. She highlights the societal-level impact of these models, which can be seen as crystallizations of human language at specific points in time.

Walker challenges the notion of measuring intelligence in terms of superiority, emphasizing that humans possess a unique capability as universal explainers. She suggests that artificial general intelligence may enhance specific human capabilities rather than represent a significant level shift in intelligence. She cautions against the narrative of a superintelligent machine that could pose a threat to humanity, emphasizing the need for human agency in shaping the co-evolution of humans and technology.

Challenges and Ethical Considerations

Walker acknowledges the rapid advancements in technology, such as deep fakes and weaponized AI, that pose ethical challenges. She stresses the importance of implementing safeguards and legislation to prevent misuse of AI technologies for malicious purposes. She discusses the need for guardrails to ensure responsible development and deployment of AI systems, addressing concerns related to privacy, security, and ethical implications.

The Future of Scientific Understanding

Reflecting on the progress of scientific knowledge, Walker speculates on the extent of human understanding in the grand scheme of the universe. She likens humanity's current position in the quest for knowledge to being in their 20s, with much more to explore and discover. She envisions a future where new questions and mysteries emerge, driving further exploration and expanding the frontiers of scientific understanding.

Free Will and Determinism

The conversation delves into the philosophical debate surrounding free will and determinism. Walker proposes a perspective where free will emerges from the deterministic structure of individuals navigating a random background. She suggests that free will operates over a temporal horizon, allowing for decision-making and steering towards desired outcomes within the constraints of individual history and causal structures.

Mathematics and Reality

Walker challenges traditional views on mathematics, advocating for a perspective where mathematical concepts are intrinsic to the physical world rather than existing in a separate platonic realm. She explores the idea of mathematics as an object of study within physics, emphasizing its role in describing and understanding the underlying structures of reality. She encourages experimental exploration of mathematical concepts to deepen our understanding of the universe.

Transformation through Ideas

Throughout the conversation, Walker expresses her passion for sharing transformative ideas that challenge conventional thinking and inspire new perspectives. She finds joy in witnessing individuals experience moments of realization and growth when confronted with novel concepts that expand their understanding of the world. Her ultimate goal is to contribute to ideas that reshape the way we perceive reality and deepen our comprehension of life, consciousness, and the universe.