Abstract: One remarkable aspect of exoplanetary science is that it's forcing us to ask fundamental questions about planetary function that we

might not have asked otherwise. I'll discuss one striking example in the puzzle of how planetary spin (or daylength) affects rocky planet

climate states and the potential for life, using state-of-the-art supercomputer climate simulations. This simple problem yields surprising results. I'll

then show how we might turn this on its head to ask the outrageous question of whether life can affect the spin-evolution of a planet through a mechanism first

suggested by Kelvin.