A black cat ran across the road - to be in trouble. The mirror broke - a big misfortune. Talk over the threshold - quarrel... Who does not know these signs that have come to our age from distant times? The reasons that brought them to life have long been forgotten, and the ridiculous superstition lives on. It lurks somewhere in our memory, next to a huge supply of useful, necessary for life knowledge, and crawls out even against our will.