Drinking Bird — Thermodynamic Heat Engine (Feynman's Favourite Toy)

Dips its beak in water. Forever. Not perpetual motion — a real heat engine running on evaporation.

Richard Feynman considered this one of the most instructive physical demonstrations in existence. It is not a perpetual motion machine. It is a genuine thermodynamic engine, driven by the temperature differential between the wet head (cooled by evaporation) and the warmer body. Evaporation cools the head, lowering the vapour pressure inside, drawing fluid up the neck, shifting the centre of mass, causing the dip. The dip wets the head. The cycle repeats indefinitely as long as there is water and a temperature gradient.

Evaporative cooling, vapour pressure, centre-of-mass mechanics, and the second law — in one glass toy.

Includes: Glass drinking bird · Felt hat · Weighted base · Feynman's analysis card

Ages 8+. Ships within 7–14 business days.