Physics
Heat Equation
The heat equation describes how temperature spreads out over time. Here it plays out in a room: a radiator warms one corner, a cold window chills another, and heat diffuses between them. Drag inside to add your own heat.
Temp at cursor—
Thermometer—
coldhot
Orange = radiator (hot), blue strip on the right = window (cold), walls sit at room temperature. In Paint heat mode, drag inside to add heat; in Thermometer mode, drag the white ring to probe a point.
What to observe
- Drop the thermometer next to the radiator: its temperature shoots up fast, then levels off as the region around it warms and the gradient driving the flow shrinks.
- Place it midway between radiator and window. It settles at a steady in-between value: heat flows continuously through it from hot to cold (steady state, not "no flow").
- Lower the diffusivity and reset. The same final picture emerges, but the thermometer curve rises far more slowly: diffusivity sets the timescale, not the destination.
Shortcuts: space run/pause · s step · r reset · f fullscreen