The correct, 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." This is a principle of
defensive design, cited here because it is usually given in mutant
forms less descriptive of the challenges of design for {luser}s. For
example, you don't make a two-pin plug symmetrical and then label it
"THIS WAY UP"; if it matters which way it is plugged in, then you
make the design asymmetrical (see also the anecdote under {magic
smoke}).
Edward A. Murphy, Jr. was one of McDonnell-Douglas's test 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 in a replacement set the wrong way around. Murphy
then made the original form of his pronouncement, which the test
subject (Major John Paul Stapp) mis-quoted (apparently in the more
general form "Whatever can go wrong, will go wrong)" 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 "Anything that can go wrong,
will"; this is more correctly referred to as {Finagle's Law}. The
memetic drift apparent in these mutants clearly demonstrates Murphy's
Law acting on itself!
[glossary]
[Reference(s) to this entry by made by: {Finagle's Law}{magic smoke}]