What is the best lava lamp? It seems that no matter how much culture changes, there’s always a demand for the retro, which is why the playful visuals of a lava lamp never seem to go out of style.

When Imre Jánosi’s teenage daughter asked him how her new lava lamp worked, she probably expected a quick explanation. But her innocent question sent Jánosi, a physicist at Loránd Eötvös University in ...