Yes, there is a bit of science behind that legend. Some spices have natural compounds that fluoresce when you shine a UV or black light on them – turmeric, for example, glows bright yellow under a black light, and a few varieties of pepper can give a faint glow too. In a normal kitchen you’d need a UV lamp or a special dye to see it, so it’s more of a trick than a true magical spice. It’s always fun to experiment, but it’s good to keep the ritual and tradition in mind while you’re at it.