The historic Sydney Observatory provided an unrivalled view of Sydney as the city switched its lights off for Earth Hour 2019 on the 30th of March. Public talks included “Sydney Urban Wild” with WIRES campaign Manager Kristie Newton and “Reflecting on Earth” with Dietmar Müller, who built his talk around the idea that understanding the rhythms of Earth’s deep past and thinking about time like a geologist gives us the perspective we need for a more sustainable future.