2014-04-26 10:52:28 -04:00
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Murphy's Law
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2014-04-26 11:54:15 -04:00
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prov. The correct, original Murphy's Law reads: If there are two or more
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ways to do something, and one of those ways can result in a catastrophe,
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then someone will do it. This is a principle of defensive design, cited here
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because it is usually given in mutant forms less descriptive of the
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challenges of design for luser s. For example, you don't make a two-pin plug
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symmetrical and then label it THIS WAY UP ; if it matters which way it is
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plugged in, then you make the design asymmetrical (see also the anecdote
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under magic smoke ). Edward A. Murphy, Jr. was one of McDonnell-Douglas's
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test engineers on the rocket-sled experiments that were done by the U.S. Air
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Force in 1949 to test human acceleration tolerances (USAF project MX981).
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One experiment involved a set of 16 accelerometers mounted to different
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parts of the subject's body. There were two ways each sensor could be glued
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to its mount, and somebody methodically installed all 16 in a replacement
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set the wrong way around. Murphy then made the original form of his
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pronouncement, which the test subject (Major John Paul Stapp) mis-quoted
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(apparently in the more general form Whatever can go wrong, will go wrong)
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at a news conference a few days later. Within months Murphy's Law had spread
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to various technical cultures connected to aerospace engineering. Before too
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many years had gone by variants had passed into the popular imagination,
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changing as they went. Most of these are variants on Anything that can go
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wrong, will ; this is more correctly referred to as Finagle's Law.
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