special seminar

Speaker: John Hernlund (ELSI)
Title: Memories of a Planet (Q&A Session to be followed)
Date (JST): Wed, Jul 08, 2015, 13:00 - 14:30
Place: Lecture Hall
Abstract: The processes that occur in a planetary system are strongly influenced by memory effects. At the largest scales, plate tectonics may be initiated by generating a sufficient "yield stress" in the stiff cool lithosphere. Once yielding occurs and weak "damage" zones are established, plate tectonics is relatively easy to sustain. A magnetic field sustained by dynamo action in a convecting metallic fluid core must initially overcome a critical threshold of self-induction relative to magnetic diffusion, but once the field is established the field can be sustained at subcritical convective vigor. At a smaller scale, life itself is thought to go through a similar transition, once a self-catalyzing system is established and memory is created by self-replication, then it becomes more robust and can run on smaller free energy gradients. When one begins looking at planetary systems as passing through critical transitions and subsequently sustained by memory effects, there is less difference between life and its planet. This are just some of the reasons that we have come to suspect that life does not exist "on a planet," but rather is an intrinsic geological process that cannot easily be separated from the planetary system. The complexity afforded to life is enabled by the rich landscape offered by carbon-based chemistry. In this talk I will explore some of the more concrete ideas of planetary memory, in addition to some of the more tenuous and new ideas emerging from our exploration of planets and their life as open systems.