Five-second rule
The five-second rule, or sometimes the three-second rule, is a food hygiene urban legend that states a defined time window after which it is not safe to eat food (or sometimes to use cutlery) after it has been dropped on the floor or on the ground and thus exposed to contamination. While the amount of microbes transferred to a dropped food does increase over time, and in some situations floors may be relatively clean of pathogens, the scientific consensus is opposed to such a general applied rule, and the origin of the idea is unclear.