Bare ice underfoot, subzero air above, and a penguin still chooses to stand. The secret is not the black‑and‑white plumage that looks like a tuxedo, but a suite of precise thermal engineering built into the legs and feet.At the core is countercurrent heat exchange, a design biologists know from fish gills and bird wings. Arteries carrying warmer blood from the body run tightly alongside veins retu...More