Conduction and convection

The tank, the rods and the pins are simulated. The water stays at exactly 80 °C, the room is at 20 °C and the wax melts at 55 °C. Each pin’s release time comes from a simple model of energy flowing along a long rod from its hot end, using real values for copper, aluminium, steel and glass, with no energy lost to the air from the sides of the rod. Real rods lose energy to the air from their sides and real water cools a little, so real pins take longer to drop, and a pin far out on a poor conductor may never drop: on real steel and glass rods in water at 80 °C, the wax 10 cm out may never reach 55 °C. The copper and aluminium pins still drop first, in that order. The glow along each rod shows the model’s temperature; real rods do not glow at these temperatures.

The magnifier’s particles are a model too: real atoms and electrons are far too small to see and move far faster, and the drawing squeezes the 10 cm from the tank to the pin into one view.

The beaker, the burner and the dye are simulated. The dye follows a single smooth loop and spreads out as it goes; real dye wanders and swirls, and the current speeds up as the water near the flame gets hotter. The flame heats the beaker gently and the water never gets near boiling. The loop runs faster than a real one, which takes a minute or two to go round a beaker.

With reduced motion each step happens at once: the rod, the jug and the beakers go straight to their places, each run shows how it ends, the camera cuts to the beaker and the magnifier draws its particles still.