Murphy's Law.

Earlier this week I needed to move two boxes from a high shelf . One of them contained a large soft toy dog, the other held 3,427 pieces of playmobile. Guess which one I failed to catch when they slipped from my grasp and headed for the floor. Said floor is covered with wooden laminate. The box without the dog in it, hit the floor with some force  and spread its contents in almost every nook and cranny. This included a sheepskin rug in which the smallest items embedded themselves in an attempt to conceal their whereabouts. The dog stayed snugly in the other box, safely held in my arms.
The mathematical equation for this is:

This is Murphy's law - "Anything that can go wrong, will go wrong." 

Colonel John Paul Stapp who was a doctor for the United States Air Force was the person who first referred to Murphy's law. He had offered to test how much force a person could take in a plane crash so he climbed into a rocket sled and sped down a half mile track at 200 miles an hour, coming to an abrupt stop at the end.  After several months, an engineer called Edward Murphy arrived at the test site with some sensors which could accurately record the G-force when Stapp came to his sudden stop. On the first run, the sensors registered a reading of zero. They could be connected in one of two ways and according to Murphy, the technician had attached them all the wrong way round. Murphy was heard to say, "If there are two ways to do something and one of them will end in disaster, he'll do it that way." Stapp was interviewed after the failed attempt to use the sensors and he attributed the research team's good safety record to their knowledge of Murphy's Law. "Whatever can go wrong, will go wrong." The phrase stuck.

I suppose the Biblical character Job was thinking a similar thing when he said, " Man is born to trouble as surely as the sparks fly upward."