Murphy's law





Murphy's law is a popular adage in Western culture, which roughly states
that things will go wrong in a technical system. It is often roughly stated
as "if anything can go wrong, it will", though this is in fact Finagle's law.

The original Murphy's law reads:

     If there are two or more ways to do something, and one of those ways
     can result in a catastrophe, then someone will do it.

It was then a principle of defensive design: anticipating the mistakes the
end-user is likely to make. For example, no competent designer would make a
symmetrical two-pin plug and then label it "THIS WAY UP"; if it matters
which way it is plugged in, the design should be asymmetrical so it can't be
plugged in wrong.

Edward A. Murphy, Jr. was one of the engineers on the rocket-sled
experiments that were done by the U.S. Air Force in 1949 to test human
acceleration tolerances (USAF project MX981). One experiment involved a set
of 16 accelerometers mounted to different parts of the subject's body. There
were two ways each sensor could be glued to its mount, and somebody
methodically installed all 16 the wrong way around. Murphy then made the
original form of his pronouncement, which the test subject (Major John Paul
Stapp) quoted at a news conference a few days later.

Within months "Murphy's law" had spread to various technical cultures
connected to aerospace engineering. Before too many years had gone by,
variants had passed into the popular imagination, changing as they went.
Most of these are variants on "If anything can go wrong, it will"; this is
sometimes referred to as Finagle's law or Sod's law. Another well known
application is to household probability: "The chance of a dropped slice of
bread landing buttered-side down on a new carpet is proportional to the
price of the carpet."

O'Toole's commentary on Murphy's law was : "Murphy was an optimist!"

These mutant versions demonstrate Murphy's law acting on itself - or perhaps
Finagle's law acting on Murphy's law.