The history of the planet Earth has had periods of being in a distinct state with intervening critical transitions that see it 'flip' between states, for example between a world without atmospheric oxygen to one with a trace of it. These key transitions have been driven by a biological evolutionary innovations which interact with the Earth system. All of these critical transitions feature a number of characteristics that mark them out as distinctive from other Earth system changes, such as that caused by the dinosaur extinction asteroid and other mass extinctions. The fact that all of these characteristics are seen today suggests that we are now on the cusp of another such a key critical transition and that this is part of a process that stretches back billions of years. Additionally, this “co-evolution of life and planet” narrative speaks to the prospect of life elsewhere in the Solar system and even the Galaxy: it informs as to what we might find and where. Earth's Flips of State speaks across disciplines: explaining biological evolution to geologists, geological Earth system evolution to life scientists, and even the relevant biology and geology to astronomers with an interest in exobiology. This book tackles the big questions as to how our species got to this point, the challenges it now faces, and the prospects of life elsewhere.