Supernova explosions mark the spectacular deaths of massive stars, and play a pivotal role in astrophysics: they create many of the elements essential for planets and life, they give rise to neutrinos, cosmic rays, and gravitational radiation, and they play an essential part in the evolution of galaxies. Yet these awesome events take a sinister shade when they occur close to home, because an explosion nearby can pose a grave threat to Earthlings. We will show how radioactive atoms produced by supernovae can reveal nearby events in the geologic past, and we will highlight isotopes of interest. In particular, geological evidence for live 60Fe (half-life 2.6 Myr) has recently been confirmed globally in multiple sites of deep-ocean material, in cosmic rays, and on the Moon. We will show how these data demand that a supernova exploded near the Earth about 3 Myr ago, and explain how debris from the explosion was transported to the Earth as “radioactive rain.” New measurements now also reveal a second, earlier supernova, and the find plutonium (244Pu) that offers a unique new probes the production of the heaviest elements in the cosmos (the r-process). Deep-ocean and lunar radioactivities thus represent a new laboratory for supernova astrophysics, and bring implications for geology and astrobiology.