Sky Lanterns Buoyancy Simulator (2D)

This 2D simulator models the real physics of a paper sky lantern: a small flame heats the air trapped inside the envelope, lowering its density below that of the surrounding night air and generating a buoyant lift force equal to the density difference times the envelope's volume times gravity. Adjust the flame heat and burn duration to control how hot the internal air gets and for how long, scale the lantern size to see the cube-square advantage larger envelopes enjoy, and dial in wind speed to watch each lantern drift as it climbs. Live readouts track the focus lantern's internal air temperature, instantaneous lift force and altitude as the flame burns down, the air cools, and the lantern eventually loses lift and descends.