Water's density peaks at 39.2°F, not at freezing. That single anomaly drives the seasonal mixing that keeps a lake's deep water breathing.

Genetic data from 1.6 million tropical insects and a wasp survey in Costa Rica suggest most of the planet's insect life has never been recorded.

The tree that legend casts as Robin Hood's hideout failed to leaf this spring. The RSPB blames crowds, propping and drought.