over time, the turn signals of cars waiting at the same intersection tend to sync up. the biological mechanism for this is not well understood, but some experts believe that cars turning the same direction are exposed to the same pheromones, light sources, stressors, etc., which make synchronization more likely. others say it gives an evolutionary advantage, that cars which blink at the same time may be more likely to complete their turns and thus pass on their genes.
bsky didn't realize this was a joke about menstrual cycles and had a lengthy discussion in my replies about the mechanical reasons turn signals might/might not synchronize at a stoplight. in case anyone was wondering whether that place was truly Twitter 2.0

