Murphy's Law

From RationalWiki
Jump to navigation Jump to search
Thinking hardly
or hardly thinking?

Icon philosophy.svg
Major trains of thought
The good, the bad,
and the brain fart
Come to think of it
If you are looking for other laws, see our longer Eponymous laws

Murphy's law states that if something can go wrong, then it will go wrong.

Murphy's law has two corrollaries: First, that if it can go wrong, it will go wrong at the worst possible time. Second, if there is a possibility of several things going wrong, the one that will cause the most damage will be the one to go wrong.

Murphy's law has one exception: Something will never go wrong when you want something to go wrong (though, recursively, this is Murphy's law). (Also known as the Law of Murphological Inapplicability.)


Murphy's law is attributed to a Captain Murphy. Dr. Stapp was an Air Force medical researcher who rode various extremely fast vehicles in order to test how much acceleration the human body can take. In one test, his assistant, Capt. Murphy, had designed a harness to strap in the rider that held 16 sensors to measure the acceleration on different body parts. There were exactly two ways each sensor could be installed. Murphy did each one wrong. When Dr. Stapp staggered off the sled with bloodshot eyes and bleeding sores, all registered zero. A distraught Captain Murphy proclaimed: If there are two or more ways to do something and one of those results in a catastrophe, then someone will do it that way.[1]


  • When you drop toast, it will land butter side down[2] (unless it is strapped butter-side up to the back of a cat, in which case the buttered cat will hover in the air. However, the impact is only negligible, as they can consciously move in midair).
  • When waiting for a bus, every other bus will show and just when you get sick and tired of it all and light a cigarette,[note 1] your bus will arrive. You may instead choose to take a cab/taxi, at which your bus will pass by you minutes after you have entered your cab.
  • Your computer will tend to crash when you have a long, unsaved edit of significant importance. The hard drive in said computer will tend to corrupt during that crash when the autosave of said document is stored locally.
  • When drinking quietly and secretively while your significant other is out with friends, you'll get to the point wherein you only have one beer left but you don't want to open it because you don't want to appear to be drinking when they arrive. After an hour and they haven't arrived, you open it, thinking all is calm, and then they walk in the door and accuse you of being drunk.
  • In the UK, it always rains on bank holidays.[3]
  • A valuable dropped item will always fall into an inaccessible place (a diamond ring down the drain, for example) — or into the garbage disposal while it is running.

Buttered cat theory[edit]

Icon fun.svg For those of you in the mood, RationalWiki has a fun article about Buttered cat theory.

The buttered cat theory is a tongue-in-cheek paradox based on Murphy's Law. It derives from two propositions:

  1. Due to Murphy's Law, a piece of buttered toast will always land on the buttered side.
  2. Cats always land on their feet (this is a common saying grounded in reality).

Due to these factors, the theory postulates that if a cat with a piece of butter-side-up toast strapped to its back is dropped, it will levitate in midair directly above the ground, spinning forever. Of course, this is completely inaccurate and impossible, but it is an amusing idea. The cat will almost certainly land on its feet as usual if this experiment is performed, as cats have an innate reflex that allows them to react quickly and turn upright when falling,[4] and toast lacks the ability to consciously move itself in midair (at least as far as we know). At most, the buttered toast will have a negligible effect on the ability of the cat to land on its feet.

However, if there is a sufficient mass of butter, then it will assumedly overcome the cat's self-righting ability, and the cat will land on its back, splatting butter everywhere. At what mass of butter the cat is unable to overcome will be different for each cat, and therefore there must be a critical cat-to-butter (C:B) ratio, above which the cat wins, and below which the floor gets messy, with the cat waving its paws madly in the air. Very near to this ratio, the cat will likely exhibit more complex behaviour, possibly landing on its side or showing other phenomena. See Professor Stewart's Hoard of Mathematical Treasures for more on the physics of buttered cats.[5]


  1. Only applicable in areas where buses are smoke-free.


  2. Tumbling toast, Murphy's Law and the fundamental constants by R. A. J. Matthews, European Journal of Physics, vol.16, no.4, July 18, 1995, p. 172-6. Matthews won the 19997 Ig Nobel Prize in Physics for his work.[1]
  3. We remember the cold, wet bank holidays and overlook the others.
  4. How does a cat always land on its feet? Huy Nguyen
  5. Hoard of Mathematical Treasures by Ian Stewart (2010) Basic Books. ISBN 0465017754.