In 1928, Arthur Eddington introduced the world to the arrow of time, the idea that time is unidirectional. Time flies forward, like an arrow, and as a result, we cannot reverse most physical and biological processes. We cannot return to the origins of the universe, age backward, or take the cream out of our morning coffee. The arrow of time is borne of the second law of thermodynamics which tells us that closed systems tend toward increasing entropy. We can’t go backward because, in closed systems, entropy is ever-increasing.
Fast-forward to the present day. In 2017, SFI launched a new, major, funded research program — Aging, Adaptation, and the Arrow of Time — to ask whether a theory of complex time can help us explain aging across physical and biological systems. On May 4-5, 2018, SFI will host its annual Science Board Symposium and will focus on complex time and the direction of this new program.
Complex time is the idea that time moves forward at different scales for different systems. Larger animals tend to live longer than smaller ones, and age in proportion to their body mass. Companies tend to have shorter lifespans than colleges or constitutions. How are we to understand these different lifespans, and their relations to one another, across systems?
Complexity scientists often understand time in terms of information gains and information loss: adaptation is a kind of information gain; decay is a kind of information loss — and entails an increase in entropy. For Caltech physicist Sean Carroll, complex phenomena — the kind of phenomena that interest researchers in the Symposium — lie between low entropy and high entropy states. We might be inclined to think that low entropy gives us complex order. But as Carroll explains, “for complex systems to arise, it's necessary that entropy increases over time.” Understanding the transition from the low entropy beginnings of our universe to the emergence of complex systems lies at the heart of complex time research.
Since complex phenomena manifest themselves in biological, physical, computational, and social systems, the AAA Symposium will bring together researchers from diverse fields. SFI External Professor Doug Erwin, for example, will explore “different timescales in which evolutionary change operates.” Mercedes Pascual, who is co-chair of the Science Board at SFI, hopes that the Symposium “will help us better understand how aging is related to the underlying and evolving structures of complex systems.”
Ultimately, the researchers driving the Symposium are seeking a concept of time that will clarify time’s power across systems. As Pascual remarks, “It is interesting to think that the notion of absolute time or physical time is not that useful in biology. But how to think of time in ways that may be valuable across biological systems is something that I hope this initiative at SFI will help us address.”