Over the past 4 billion years we’ve come through some thrilling, chilling episodes, says Prof. John Baez of the University of California Riverside and the University of Edinburgh. We collided with the planet Theia, there was ‘Snowball Earth’ when most of the oceans froze, and there was the asteroid impact that ended the age of dinosaurs. Some of the past catastrophes are well documented, others only theorised, but life somehow came through them all. Can this, he asks, give us hope in today’s uncertain times?