My main goal is to understand why the Universe is magnetic. By measuring the polarised radio signals from millions of distant galaxies over the entire sky, I aim to transform our understanding of magnetism in galaxies, clusters and in diffuse intergalactic gas. I also study the ways in which celestial objects change, flicker, flare and explode. I am working to provide a new understanding of the many different populations of transient and variable phenomena, and to develop the novel source-finding and classification algorithms needed to find rare and unusual behaviour in very large data sets. In the next decade, all of this work will culminate in the Square Kilometre Array, a next-generation radio telescope that will answer fundamental questions about the Universe.