The universe is out to get us. Or at least it's after our buttered toast. You probably know what I'm talking about. If you're eating toast, and you accidentally bump it to the floor, it seems more likely to land buttered side down. This is one of the most common formulations of Murphy's Law--the tongue-in-cheek axiom that states "If something can go wrong, it probably will."
You might wonder why we're talking about Murphy's Law on A Moment of Science. Surely this so-called "law" is material for comedians, not scientists. If you examine the toast problem rationally, surely you'd expect a fifty-fifty outcome, much like flipping a coin.
Actually, according to physicist Robert Matthews, Murphy is right, at least as far as toast is concerned. In his study "Tumbling Toast, Murphy's Law and the Fundamental Constants," he points out that most buttered toast isn't flipped like a coin--it slides off the breakfast table, initially buttered side up. The toast begins tilting as soon as it goes over the table edge.
On the way to the floor, it rotates--buttered side turning down as the dry side turns up. For an average breakfast table, this rotation is enough to turn your toast exactly half way over before it hits the floor. To turn a full three hundred-sixty degrees--so the toast lands buttered side up--your breakfast table would need to be ten feet high.
You can test this at home, without getting your carpet messy. Place an ordinary paperback book on your table, front cover up, and push it slowly off the side. Chances are, it will land cover down!