Thermal radiation

The cube, the detector and the water are simulated. The room and the detector are at 20 °C, and the water stays at the temperature it was poured in at while you take the readings. Each reading comes from the temperature of the side and how well its surface emits: matt black paint 0.95, matt white paint 0.90, dull aluminium 0.20 and polished aluminium 0.05 of the most a surface could emit at that temperature, with the detector catching a quarter of what would reach it if the side filled its whole view. Real paints and metals vary, so a real Leslie cube gives different numbers, but the order is the same.

The cans, the lamp and the water are simulated. Each can holds 150 cm³ of water and receives 6.0 watts of the lamp’s radiation; the black paint absorbs 95 % of it and the white paint 25 %. Each can transfers energy away at 0.35 watts for every degree it is above the room. Real cans lose some energy through their lids and bases, so they settle at different temperatures, but the black can always warms faster and settles higher.

The wavy arrows are drawings of radiation you can’t see. The cube itself never glows, and the lamp’s glow shows only that it is on.

With reduced motion each step happens at once: the jugs pour, the cube turns and the lamp moves straight to their places, each reading appears already settled, each run of the lamp shows its whole graph at once and the camera cuts to the cans.