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If you're old enough to read this and understand it then the chances are you've relied on the five second rule at some point in your life.
It's pretty simple: you drop some food on the ground, but if you can pick it up within five seconds then it's probably going to be fine, anything longer and it's probably best just to accept the loss and move on.
The idea goes that five seconds isn't enough time for the bit of food to get swarmed by germs and transform a once tasty morsel into a stomach bug waiting to happen.
Besides the five second rule there are a few other factors which you should think of when picking up your fallen food.
What it's fallen on to is a major one, dropping your dinner onto a nicely polished floor isn't going to guarantee a germ-free meal is salvageable, but it's a damn sight better than deciding whether to sink your teeth into something still covered with dirt from the ground.
Interestingly, the historical basis for the five second rule dates back centuries to the days of Genghis Khan and the Mongol Empire.
According to Paul Dawson and Brian Sheldon, who wrote the book Did You Just Eat That?, when Genghis Khan wasn't busy killing people or having kids he was making up rules for how long food could stay on the ground while still being good to eat.
While he didn't lock the rule into a particular time limit, back in his day if food fell on the floor it stayed there as long as he liked.
When the conqueror who built the world's largest contiguous empire tells you it's fine to pick food up off the floor it's probably best to listen to him.
As for the science behind it, it's true that the longer your food is stuck on the floor the more germs can swarm all over it and render it a danger to eat.
However, sorry to disappoint you all, but science says germs will start getting onto your food the instant it touches the ground, even if it's only there for a split second it can end up getting contaminated.
Scientists putting the five second rule to the test found that the type of food and the type of surface were more important than how long it stayed on the ground, but in general the longer time wasted before picking it up, the less safe it was to eat.
They found that wet foods like fruits are in particular danger of picking up harmful germs as they have an easier time letting diseases latch onto them.
Meanwhile, food which falls on a carpet is less likely to get horribly infested with germs, though it might be a bit fluffy when you pick it up.
I don't know about you but I'm choosing to interpret that as support for the five second rule being a thing, as long as you use some common sense.