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Light patterns that show up around the Sun, technically called parhelia, are a natural phenomenon that has fascinated mankind for at least 2300 years, since Aristotle’s time. In cold regions, sunlight interacts with small ice crystals suspended in the atmosphere and, under certain conditions, gives rise to pairs of bright spots (also known as mock suns or sun dogs), a halo (parhelic circle) and straight lines (sun pillars) around the Sun. On even rarer occasions, these formations also occur around the moon. The video produced by Pesquisa FAPESP's team shows how the physicist couple Adriana and Alberto Tufaile, from the Soft Matter Laboratory of the University of São Paulo (USP), has developed an experimental model and provided a new explanation for this phenomenon using water, dish-washing detergent and a laser pointer like those used in seminars.
