From: jimruttshow8596
Assembly Theory, a new framework developed by Sarah Walker and Lee Cronin, offers a novel perspective on complexity, information, and the nature of time. It posits that the complexity of an object can be quantified by the minimum number of steps required to build it from fundamental parts, allowing for the reuse of components during assembly [01:13:00]. This approach directly challenges traditional notions of complexity theory and has profound implications for understanding the origin of life and the search for extraterrestrial intelligence.
Critiquing Traditional Complexity Theory
Lee Cronin and Sarah Walker strongly critique existing complexity theories, arguing that they are fundamentally flawed [02:25:26]. Cronin cites Freeman Dyson, who stated that the entire literature of complexity theory suffers from a deficiency: it is a collection of interesting examples of complex objects and systems but lacks a general understanding of their behavior or a unifying theory [02:49:50]. Cronin asserts that complexity theory was largely “generated by computationalists fascinated with computation and Turing machines” and often serves as an “excuse to not actually do your accounting properly” [02:26:02].
Walker adds that traditional measures from computer science, like Kolmogorov complexity, focus on program size and require searching over all possible machines to find a minimal description, making them uncomputable [01:36:00]. Assembly Theory, in contrast, is concerned with the intrinsic physical properties of an object and the minimal set of causal pathways required to make it, operating under strict constraints imposed by the laws of physics [01:50:52]. A key distinction is that traditional complexity measures cannot distinguish random objects from truly complex ones, whereas Assembly Theory considers random objects very difficult to make and unlikely to be evolved [02:08:00].
Core Concepts of Assembly Theory
Assembly Theory proposes that the “assemblyness” of an object is a measurable physical attribute, not merely a computational abstraction [01:51:00]. Its core tenets include:
- Number of Parts and Copies [01:46:00]: The theory considers how unlikely an object is to form by chance, based on having a large number of parts and being present in a large number of identical copies [01:51:00]. The more identical copies of a complex object (like ten identical iPhone 14s), the more certain it is that it didn’t form by chance [01:36:00].
- Recursive Decomposition and Steps [01:40:00]: The “assembly index” or “steps” of an object is defined as the shortest path to form it by recursively combining its components, allowing for the reuse of components [02:51:00]. The larger the number of steps, the more improbable it is that the object formed by chance in a random environment [02:51:00].
- Measurability [03:00:00]: A crucial aspect of Assembly Theory is that the “steps” or assembly index can be experimentally measured for molecules using techniques like light absorption, magnetic resonance, and mass spectrometry [03:00:00]. This empirical grounding distinguishes it from more abstract complexity measures [03:00:00].
- Memory and Causal Chains [03:22:00]: Every object, by its construction history, “encodes its own memory” [01:52:00]. This means the ability to create complex objects with many steps is prerequisite on the existence of effective memory in the system [03:22:00]. In biological systems, this memory includes DNA, cytoplasm, and cellular metabolism [03:22:00]. This memory is not abstract but “instantiated in physical objects” [04:36:00].
Assembly Theory as a Theory of Time
Sarah Walker argues that Assembly Theory is, in essence, a theory of time [08:19:00]. While traditional physics views time as a fluid the universe moves through or a concept like Einstein’s block universe (where all times exist everywhere at once), Assembly Theory posits time as an intrinsic property of objects [08:19:00].
- Incompatibility with the Block Universe: If Assembly Theory is correct, it fundamentally refutes Einstein’s block universe concept because it implies that some things must happen before others [01:16:00]. The theory suggests that novelty exists and that the universe’s capacity for things to happen is increasing [05:20:00].
- Materiality of Information: For Assembly Theory, information is not an abstract concept but a “temporarily embedded structure” that is a physical feature of the object itself [01:00:00]. The “depth” of an object in time, reflecting its causal history, becomes a physical attribute [01:06:00].
- Fundamental Asymmetry: The theory aligns with the intrinsic asymmetry of the universe (e.g., CP violation in particle physics) [01:17:00], providing a mechanism for why the second law of thermodynamics (increase in disorder) makes sense, as the capacity for more things to happen in the future increases [05:20:00].
Assembly Theory and the Emergence of Life
Assembly Theory provides a framework for understanding the transition from non-life to life, identifying a “sharp phase transition” in the combinatorial space of chemistry [04:22:00].
- The Biotic Threshold: Experiments show a clear boundary around 13 or 14 assembly steps, with objects beyond this threshold (e.g., 15 steps or more) being characteristic of biotic (life-driven) processes [04:22:00]. While life can produce low-assembly objects, high-assembly objects are definitive signatures of living physics [04:22:00]. This threshold arises because the possibility space for objects grows exponentially with each step, requiring selection mechanisms to navigate [04:40:00].
- Prebiotic Selection: A critical implication is that “selection has to predate biology as we know it” [03:52:00]. Assembly Theory suggests a mechanism for how complexity can build through steps, initially randomly, and then through the establishment of memory mechanisms in the universe [03:52:00].
- Life as a Selection Amplifier: Biology acts as a “selection amplifier,” accelerating the production of high-assembly objects [03:52:00]. It’s a “recursive transformation that is continually still happening” [03:52:00].
- Challenges to Autocatalysis: While recognizing the importance of autocatalytic networks for life’s emergence, Walker notes that they are often brittle and require fine-tuned reaction conditions [05:51:00]. Assembly Theory aims to explain features of autocatalysis by embedding them within a broader evolutionary context [05:51:00].
Assembly Theory and Technosignatures/Intelligence
Assembly Theory extends beyond biology to consider techno-signatures and intelligence [04:46:00].
- Life-Technology Phase Transition: Just as there is a sharp transition between non-biotic and biotic chemistry, there may be another phase transition between life and technology/intelligence [04:46:00]. Human technology, through abstraction and redesign, can create molecules with assembly indices (e.g., 50 or more) that biology alone could not [04:46:00].
- Limits to Molecular Information: There is a finite limit to the amount of information that can be stored in a molecule due to error rates (mutations) [05:07:00]. If the mutation rate is too high, it’s impossible to get clean, identical copies of very large, complex molecules [05:07:00].
- The Fermi Paradox and “Perceptual Filter”: Sarah Walker suggests that the Fermi Paradox might be explained by a “great perceptual filter” [01:07:00]. Instead of aliens going extinct, humanity may not have developed the “perceptual apparatus” or physics to recognize alien life or technology [01:07:00]. Just as gravitational waves existed for billions of years before we developed the theory and technology to detect them, alien life might exist in forms we currently cannot perceive or understand [01:09:00]. Understanding the fundamental physics of life on Earth (perhaps by creating alien life in the lab) might provide new “lenses” to detect it elsewhere [01:09:00].
- Remote Sensing for Complexity: The theory proposes looking for complex molecules in exoplanet atmospheres with high assembly numbers (greater than 15) as a technosignature [01:10:00]. The challenge lies in modeling planetary evolution in terms of assembly-theoretic principles and remotely detecting the “memory” or “structure of evolving complexity” on a planet [01:10:00].
- Probability of Life: Assembly Theory aims to make predictions about the likelihood of life emerging in specific chemical environments [01:19:00]. It posits that statements about the probability of life or aliens cannot be made until the physics of the non-life to life transition is fully understood [01:19:00]. The entire causal chain of life on Earth is a unique, interconnected structure, making arguments about the ease of events like multicellularity potentially flawed [01:19:00]. Cronin suggests that selection is a fundamental process in the universe, much like gravity, and that matter drives to complexity, meaning life could be widespread if enough “selection” occurs [01:21:00].
Assembly Theory seeks to provide a unified, physically grounded language to describe both the non-living and living universe, bridging the gap between physics and biology [04:54:00].