A 2016 study confirmed what most of us probably already know: the five-second rule is a bunch of baloney. This "rule" is that food dropped on the floor and left there for five seconds or less is "safe" to eat. The theory there is that is takes more than five seconds for the bacteria on the floor to transfer onto the food. Sorry, that's not a thing. While increased time spent on the floor can mean more bacteria on the food, there's no way to avoid bacteria getting on food that's been dropped on the floor.
This study found that at least some bacteria transferred onto food instantaneously when it hits the ground. But the amount of bacteria that gets on the food depends on a few factors, including the nature of the food (Is it wet? Porous and spongy?), and the surface the food lands on. We're not trying to tell you how to live your life, though. Watch the videos below for more science on the five-second rule.