If you take a breath now, you will inhale about fifteen atoms of argon that you exhaled in a breath a year ago. Atoms from that earlier breath will have spread out from you, eventually drifting all around the world and back to you. You reconnect with yourself. You also connect with everyone else, and everything else, that exhaled a year ago. So said Harlow Shapley, an astronomer with the soul of a poet who thought deeply about his home planet.