Readers ask about positronium, wild bees and more

Dance of the doomed particles

Scientists are puzzled by an unexpectedly large gap in the energy levels of an exotic “atom” called positronium, which consists of an electron and a positron, Emily Conover reported in “Positronium result baffles physicists” (SN: 9/12/20, p. 14).

Reader Lee Skinner asked why the electron and its antimatter counterpart, the positron, don’t just annihilate each other when they collide.