Neutrinos are elusive particles produced in nuclear reactions, including those inside the sun, in exploding stars, and in radioactive decay. Vast numbers pass through Earth and human bodies every second, usually without leaving a trace. In poetry, a neutrino can embody the unnoticed traveler, the message that crosses every barrier, or the nearly weightless fact of existence. Its scientific strangeness gives language to what is everywhere present yet almost impossible to hold, measure, or answer.

Neutrinos are produced in the Sun, exploding stars, and nuclear reactions. Because they interact so weakly with matter, trillions pass through a human body each second unnoticed.