Martin Rees isn't just one of the world's most respected cosmologists (and Britain's Astronomer Royal), who's contributed to some of the field's biggest advances over the last four decades. He's also an ecumenical thinker with a broad view of the sciences and their limits, our historical moment and the long-range prospects for earth and its inhabitants. We talked about cosmology past and present, the politics of science in the US and Europe, science vs. religion, climate change and the human (or post-human) future.