As the observation interval lengthens—akin to slowing down a camera’s shutter speed—the dances of the molecules overlap and emerge as a blur of frequent changes, masking the intricate ballet of atoms in motion. (Illustration: Yumi Teruya)
The dendrogram of indistinguishability of the Claisen rearrangement of allyl vinyl ether. Each colored step indicates an observation where exact coarse-graining applies. (Illustration: Yutaka Nagahata)