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ASSEMBLY THEORY OF TIME

 

Abstract

 

       TIME IS AN OBJECT:  Not a backdrop, an illusion or an emergent phenomenon, time has a physical size that can be measured in the laboratory.  Time is unidirectional forward.

 

       ASSEMBLY THEORY:  Proposed by Sara Walker of the University of Arizona and Lee Cronin of Glasgow in Scotland.  Darwin’s Natural Selection is at play here and Assembly Theory quantifies selection by making time a property of objects that could have emerged only via evolution.  Life is evident when the space of possibilities is so large that the universe must select only some of that space to exist.  Assembly Theory can function as a universal life-detection system that works by measuring the assembly indexes and copy numbers of molecules in living or nonliving samples.

 

Discussion

 

       Assembly theory explains evolved objects that involve biospheres, molecules and computers.  Such objects exist only along lineages where information has been acquired specific to their discovery.  The nature of these objects are explained by Walker and Cronin as follows:

 

       If the lineages are followed back beyond the origin of life on Earth to the origin of the universe, it would be logical to assume that the memory of the universe was lower in the past, which means that the universe's ability to generate objects of high Assembly is limited by its size in time.  Some objects are too large in time to come into existence in intervals that are smaller than their assembly index.  For complex objects such as computers to exist in our universe, many other objects had to form first, such as stars, heavy elements, life, tools, technology and the abstraction of computing.  All this takes time and is path-dependent due to the casual contingency of each innovation that is made.  The early universe may not have been capable of computation, as we know it, because not enough history had existed.  Time had to pass and be materially formed through the selection of the computer's constituent objects.  This is also true for large language models, new pharmaceutical drugs, the techno sphere or any other complex object.

 

       The consequences of objects having an intrinsic material depth in time are far reaching.  In the block universe, everything is treated as static and existing all at once, which means that objects cannot be ordered by their depth in time, and selection and evolution cannot be used to explain why some objects exist and others do not.  Considering time as a physical dimension of complex matter and setting directionality for time should help solve such questions.  Making time material through assembly theory unifies several philosophical concepts related to life in one measurable framework.  Basic to this theory is the assembly index, which measures the complexity of an object.  It is a quantifiable way of describing the evolutionary concept of selection by showing how many alternatives were excluded to yield a given object.  Each step in the assembly process of an object requires information, memory, to specify what should and should not be added or changed.  A specific sequence of steps is required to construct an object, and each misstep is an error.  If too many errors are made a recognizable object cannot result.  Copying an object requires information about the steps that were previously needed to produce similar objects.

 

       Assembly theory is a casual theory of physics because the underlying structure of an assembly space (the full range of required combinations) orders things in a chain of causation.  Each step relies on a previously selected step, and each object relies on a previously selected object.  If we removed any steps in an assembly pathway, the final object would not be produced.  Phrases that are frequently associated with the physics of life, such as "complexity, "information," "memory", "causation," and "selection," are material because objects themselves encode the rules to help construct other complex objects.  This process could be the case in mutual catalysis where objects reciprocally make each other.  Therefore, in assembly theory, time is essentially the same thing as information, memory, causation and selection.  They are all made physical because we assume they are features of the objects described in the theory, not the laws of how these objects behave.  Assembly theory reintroduces an expanding, moving sense of time to physics by showing how its passing is the stuff that complex objects are made of:  The size of the future increases with complexity.

 

       Time is fundamental and this new conception of time might solve many open problems in fundamental physics.  The first and foremost is the debate between determinism and contingency.  Einstein famously said that God "does not play dice," and many physicists are still forced to conclude that determinism holds, and our future is closed.  But the idea that the initial conditions of the universe, or any process, determine the future has always been a problem.  In assembly theory, the future is determined, but not until it happens.  If what exists now determines the future, and what exists now is larger and richer in information than in the past, then the possible futures also grow larger as objects become more complex.  This is because there is more history existing in the present from which to assemble novel future states.  Treating time as a material property of the objects it creates allows novelty to be generated in the future.

 

       Novelty is critical for our understanding of life as a physical phenomenon.  Our biosphere is an object that is at least 3.5 billion years old by the measure of clock time (Assembly is a different measure of time).  But how did life get started?  What allowed living systems to develop intelligence and consciousness?  Traditional physics suggests that life "emerged."  The concept of emergence captures how new structures seem to appear at higher levels of spatial organization that could not be predicted from lower levels.  Examples include the wetness of water, which is not predicted from individual water molecules, or the way that living cells is made from individual nonliving atoms.  However, the objects traditional physics considers emergent become fundamental in assembly theory.  From this perspective an object's "emergentness" (how far it departs from a physicist's expectations of elementary building blocks) depends on how deep it lies in time.  This idea points toward the origins of life, but we can also travel in the other direction.

 

       If this is the right track, assembly theory suggests time is fundamental.  It suggests change is not measured by clocks but is encoded in chains of events that produce complex molecules with different depths in time.  Assembled from local memory in the vastness of combinatorial space, these objects record the past, act in the present, and determine the future, which means the universe is expanding in time, not space--or maybe space emerges from time, as many current proposals from quantum gravity suggest.  Though the universe may be entirely deterministic, its expansion in time implies that the future cannot be fully predicted, even in principle.  The future of the universe is more open-ended than we could have predicted.

 

       Time may be an ever -moving fabric through which we experience things coming together and apart.  But the fabric does more than move--it expands.  When time is an object, the future is the size of the universe.

 

 

REFERENCES:

 

Doran, D. E., E. Clarke, G. Keenan, E. Carrick, C. Mathis & L. Cronin.  2021.  Exploring the sequence space of unknown oligomers and polymers.  Cell Reports Physical Science 2:  100685.

 

Liu, Y.  C. Mathis, M. D. Bajczyk, S. M. Marshall, L. Wilbraham & I. Cronin.  2021.  Exploring and mapping chemical space with molecular assembly trees.  Science Advances 7: 3abm 2465.

 

Marshall, S. M. et al.  2021.  Identifying molecules as biosignatures with assembly theory and mass spectrometry.  Nature Communications 12:  3033.

 

Marshall, S. M., D. G. Moore, A. R. G. Murray, S. I. Walker & L. Cronin.  2022.  Formalising the pathways to life using assembly spaces.  Entropy 24:  884. 

 

Sharma, A., D. Czegel, M. Lachmann, C. P. Kempes, S. I. Walker & L. Cronin.  2023.  Assembly theory explains and quantifies the emergence of selection and evolution.  Vol 3, arXiv:  2206.  02279.

 

Walker, Sara & Lee Cronin.  2023.  Time is an object.  American Scientist III (5):  302-309.