The natural direction of heat flows—from hot to cold—can be reversed thanks to quantum effects
In a hot summer Sunday braai or shisa nyama (South African barbecue), if you don't finish your favorite beverage quickly, the ice cubes will melt and the drink will get warm—undoubtedly spoiling your braai/shisa nyama. That's because the natural direction of the heat is always from hot to cold (Fig. 1). The reverse, a drink that grows increasingly colder—which would definitively save your Sunday—looks like science fiction. Indeed, this would be like reversing the arrow of time. Our recent study establishes that things might be very different in the quantum world.