Imprinting a coherent light pulse on the spins of atoms is standard quantum sorcery. Retrieving the same light pulse from a second, distant set of atoms looks rather like black magic. But it, too, is just quantum mechanics.

As massive ice sheets grew on Antarctica during the first major glaciation of the Cenozoic era, the northern continents cooled and dried. The coincidence in timing implies that the cause was global rather than regional.