The sun in this frame is a few millilitres of alcohol ink in a Petri dish. No animation, no simulation, just surface tension losing an argument with itself. Alcohol inks are dye or fine pigment carried in isopropanol or ethanol. That carrier has a surface tension near 22 millinewtons per metre. Water sits at roughly 72, more than three times higher. Put one into the other and the interface cannot stay still, because the surrounding high tension liquid drags the low tension patch outward in every direction at once. This is the Marangoni effect, and at macro scale it is violent: spreading fronts cross a dish smaller than a coin in a fraction of a second. What turns a spreading blob into a corona: - Viscous fingering. When a thin, mobile fluid displaces a thicker one, the interface is unstable. Any bulge advances faster than its neighbours and runs away, splitting again and again into the branching filaments that read as sunbeams. - Evaporation. Alcohol leaves first, so the film left b...