The five second rule states that when an item of food hits a surface (usually the floor, as a result of being dropped), if it is retrieved within 5 seconds of impact, it is not considered 'dirty', and may still be directly eaten.

The most well known current reference to this rule is embodied in a 30 second Volkswagen Passat television commercial, wherein a new father questions his paternal abilities.

"Suddenly I'm the one saying 'don't touch the cookie on the ground', when I'm really thinking 'five second rule' "

This rule seems to be a rare example of human instinct. It is sometimes referred to as the three second rule, but regardless, it seems to be independently arrived at, in one form or another, by most people.

Of course, the application of this rule varies, depending upon individual preference, the conditions of the food and the surface in a given circumstance, and socio-economic factors.

The five second rule allows you to determine how far away a lightning strike, or pretty much any event that you can both see and hear, is.

Sound travels about one mile every five seconds, so if you see some lightning, and start counting seconds, then hear thunder, you can estimate how many miles away the lightning struck by dividing the number of seconds by five. If you never hear the thunder, the strike was probably too far away to matter anyway.

This can also be used to find out how far away fireworks are when they go off. See the boom, start counting, hear the boom, divide. It's that simple.

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