Your tasty bagel falls on the floor.  You hate to waste food, and you’d rather not toast a new one.  Can you call "five second rule" and consume it without risk of food-poisoning?   Not according to research from Clemson scientists reported in National Geographic.  Here is the somewhat frightening heart of the story:

According to food-science research at Clemson University, there is no five-second rule. It’s the zero-second rule. Writes Catherine Barker, "salmonella and other bacteria can survive up to four weeks on dry surfaces and transfer to food immediately upon contact."

Other studies had suggested less risk, but with a quote like that, it seems smart to be on the safe side.  Interestingly, your own kitchen (and bathroom of course, but just don’t eat in there) is probably one of the riskiest place to drop food.  

So, hold on tight to your bagel, and think twice before giving it a second chance.