Murphy's Law

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	This is the JargonFile (V4.00) entry for Murphy's Law - Next: music, Prev: munge
:Murphys Law: /prov./ The correct, *original* Murphys 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 lusers. For example, you dont 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 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 subjects 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 Murphys 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 correctly referred to as [[Finagles Law]]. The memetic drift apparent in these mutants clearly demonstrates Murphys Law acting on itself!
* (text is auto-included via JargonExtension by mutante using jargon with VERSION 4.0.0, 24 JUL 1996 - JargonFile by Eric S. Raymond is in the public domain)