Australia is home to abundant uranium and thorium reserves, the radioactive heavy metals that fuel nuclear reactors, arm militaries, and contribute to the production of radioisotopes for medical and imaging uses. These latter uses offer new insights into the past that were previously impossible to discern. The extraction and uses of Australia’s uranium and thorium reserves have transformed understandings of Australia’s deep human past, but also have immediate and long-term consequences for local communities and landscapes. In this Deep Conversation, we reflect on just how the atom shapes and shares our histories as well as its lasting human and environmental legacies in the twenty-first century. Deep conversations: history, environment, science series is a partnership of the Research Centre for Deep History and Centre for Environmental History. It aims to bring together scholars from diverse disciplines to discuss questions of history, science and the environment, and how they shed light on the global challenges we face today.