Yue Wu

Water in a cup cools down in minutes. Gas in a room spreads evenly in seconds. But if you trap atoms in a tube as thin as a laser beam and give them a good kick, they will take several seconds to "cool" toward equilibrium — an eternity by atomic standards.

A microplastic particle drifts on the surface of a warm sea. Within days, invisible hitchhikers, bacteria and single-celled algae, cover it. This living film acts as ballast: the particle becomes heavier and starts to sink. In a new global model, oceanographers have for the first time tracked the fate of such "hitchhiking" plastic across the entire planet.