The lessons learned from ephemeral nuclei

Recent experimental analyses of fleeting clusters of protons and neutrons put the very notion of the atomic nucleus in a new light. Atomic nuclei can be divided into those that are stable and those that are not. The latter often are labeled radioactive. But this binary classification fails to capture the range of nuclear lifetimes, from those that last less time than it takes for light to cross atomic dimensions to those that dwarf the age of the universe.