There's this thing called the "5 second rule" that lots of people have believed for ages. It's where when food falls on the ground, you have 5 seconds to pick it up and eat it before loads of bacteria actually get to the food and could make you ill.
But how true is this theory?
Most bacteria move very slowly - about 0.00045 miles per hour - which is 67 times slower than a garden snail, but the moment your food comes in contact with the ground, there will be immediate bacteria transfer between the surface of the ground and the surface of the food you have dropped.
Moist foods do have a 30-second rule, which is where moist food left on the ground for longer than 30 seconds will sop up all kinds of bacteria you wouldn't believe. This includes E-Coli and salmonella. Dry foods falling on dry ground, on the other hand, are far more likely to be safe to eat after just five seconds on the ground.
Watch people's reactions are they're asked to eat cookies that fall on the ground in the name of science!