Murphy's Law ... Defensive design little light reading

Something to think about for all Business Continuity professionals ...
Murphys Law
Murphy's law (distinct from, and often confused with Finagle's law or Sod's law) is a popular adage in Western culture, which broadly states that things will go wrong in any given situation in which error is possible. "If there's more than one way to do a job, and one of those ways will result in disaster, then somebody will do it that way."
It is most commonly formulated as "Anything that can go wrong will go wrong" and is something we have become all too familiar with in the Business Continuity Field!
Technically speaking, this latter definition is incorrect, given that it refers more accurately to the law of pessimism, Finagle's Law.
In American culture the law was named after Major Edward A. Murphy, Jr., a development engineer working for a brief time on rocket sled experiments done by the United States Air Force in 1949.
The letter of the law
Accounts differ as to the precise origin of Murphy's law and the details about how it was initially formulated. The most definitive account appears in the book "A History of Murphy's Law" by author Nick T. Spark. As Spark relates, from 1947 to 1949, a project known as MX981 took place on Muroc Field (later renamed Edwards Air Force Base) for the purpose of testing the human tolerance for g-forces during rapid deceleration.
The tests used a rocket sled mounted on a railroad track with a series of hydraulic brakes at the end. Initial tests used a humanoid crash test dummy strapped to a seat on the sled, but subsequent tests were performed by John Paul Stapp, at that time a Captain. During the tests, questions were raised about the accuracy of the instrumentation used to measure the g-forces Captain Stapp was experiencing.
Edward Murphy proposed using electronic strain gauges attached to the restraining clamps of Stapp's harness to measure the force exerted on them by his rapid deceleration. Murphy's assistant wired the harness, and a trial was run using a chimpanzee. The sensors provided a zero reading, however; it became apparent that they had been installed incorrectly, with each sensor wired backwards. It was at this point that Murphy made his pronouncement.
In an interview in Spark's book, another engineer named George Nichols claims he witnessed the malfunction. Nichols further states that Murphy, in frustration, blamed the failure on his assistant, saying, "If that guy has any way of making a mistake, he will."
Nichols' account is that "Murphy's law" came about through conversation among the other members of the team; it was condensed to "If it can happen, it will happen," and named for Murphy in mockery of what Nichols perceived as arrogance on Murphy's part. Others, including Edward Murphy's surviving son Robert Murphy, deny Nichols' account, and claim that the phrase did originate with Edward Murphy.
According to Robert Murphy's account, his father's statement was along the lines of "If there's more than one way to do a job, and one of those ways will result in disaster, then somebody will do it that way." In any case, the phrase first received public attention during a press conference in which Stapp was asked how it was that nobody had been severely injured during the rocket sled tests. Stapp replied that it was because they took Murphy's Law under consideration; he then summarized the law and said that in general, it meant that it was important to consider all the possibilities before doing a test.  
A similar sentiment is expressed by "Hawley's Law" that defined: That if any string; rope; thread; cord; line or piece of fabric etc. can get caught in, stuck on or around another object at the most importune and inconvenient time it will!
Murphy's law has taken on many different formulations. In 1952, the proverb was phrased "Anything That Can Possibly Go Wrong, Does" in the epigraph of John Sack's The Butcher: The Ascent of Yerupaja. Possibly the earliest printed use of Murphy's name in connection with the law is in Lloyd Mallan's 1955 book, Men, Rockets and Space Rats: "Colonel Stapp's favorite takeoff on sober scientific laws  - Murphy's Law, Stapp calls it ”'Everything that can possibly go wrong will go wrong'."
The spirit of the law
Regardless of the exact composition and origin of the phrase, its spirit embodies the principle of defensive design - anticipating the mistakes the end-user is likely to make. Murphy's g-force sensors failed because there existed two different ways to connect them; one way would result in correct readings, while the other would result in no readings at all. The end-user, Murphy's assistant, in the historical account, had a choice to make when connecting the wires. When the wrong choice was made, the sensors did not do their job properly. Thus, defensive design is sometimes referred to as "Murphy proofing" a procedure.
In most well-designed technology intended for use by the average consumer, incorrect connections are made difficult. For example, a hard disk used in many personal computers will not easily fit into the drive unless it is oriented correctly. In contrast, the older 5.25-inch floppy disk could be inserted in a variety of orientations that might damage the disk or drive. The newer CD-ROM and DVD technologies permit only one incorrect orientation, the disc may be inserted upside-down.
A defensive designer knows that if it is possible for the disc to be inserted the wrong way, someone will eventually try it. Fatalists observe that even if it theoretically is not possible to perform something incorrectly, someone will eventually manage it or, as Silvermoon's law puts it: Nothing is foolproof to a sufficiently talented fool.
From its initial public announcement, Murphy's law quickly spread to various technical cultures connected to aerospace engineering. Before long, variants had passed into the popular imagination, changing as they went. Generally, the spirit of Murphy's law captures the common tendency to emphasize the negative things that occur in everyday life; in this sense, the law is typically formulated as some variant of "If anything can go wrong, it will," a variant often known as "Finagle's law" or "Sod's law" (chiefly British).
Laws such as Murphy's are a direct expression of such seeming perversities in the order of the universe. Additional mutations of the law and its corollaries have developed, many of them meta-laws in some way, either through some form of self-reference or referral to other laws or analogies. For instance, the buttered-bread analogy could be further extended: "The chance of a dropped slice of bread landing buttered-side down on a new carpet is proportional to the price of the carpet." (If the buttered side falls facing up, then obviously the wrong side is buttered.)
A further example is Murphy's Ultimate Corollary: "If it could have gone wrong earlier and it did not, it ultimately would have been beneficial for it to have." Something to bear in mind when you are knee deep in your next test or exercise!
John Gall's systemantics offers further expansion of Murphy's law. "Laws" can occasionally be found to lead to a paradox, or which have positive outcomes; for example: when a cat is dropped from above a certain height, it will always land on its feet. In almost a canonical example of the hackish love for wordplay and cultural in-jokes, it has been noted that, therefore, if you strap a piece of buttered toast to the back of a cat, butter side up, and drop the cat out a window, it will fall to approximately a foot above the street, and hover there, spinning. Who said Philosophy wasn't funny!
Some state that Murphy's law cannot operate as a subset of something useful; for example: "It will start raining as soon as I start washing my car, except when I wash the car for the purpose of causing rain."
O'Toole's commentary on Murphy's law is: "Murphy was an optimist!".  These mutant versions demonstrate Murphy's law acting on itself, or perhaps Finagle's law acting on Murphy's law.
Murphy's Law is sometimes also presented as a life philosophy. Also embodying defensive design, many simply see it as a way of saying in the approach of anything whatsoever that could have a possible flaw (be it an engineering project, a romantic relationship, an argumentative case, carrying an upright bass down a flight of stairs, or putting on your suit), then it's always within good measure to make the necessary precautions to make sure that those flaws can't happen.
Many others see it as the initial meaning behind what Murphy was saying, a simple philosophy of defensive design that has been highly misinterpreted. However, this is left open to controversy.
  • A slice of buttered bread, when dropped, will always land butter-side down. (This has been proven wrong repeatedly though in various tests, although we are awaiting the results of the Cat test highlighted earlier with some eagerness). We have tried it ourselves, but have repeatedly fallen foul of Hawleys Law (see above).   
  • When you need an item that is in a heap, it will always be the one at the bottom.
  • Buses take ages to arrive, but when they do they always arrive in sets of three (in Britain "you wait ages for a bus, then two come along at once!"). There actually is a logical explanation for this: the first bus is slowed down because of the time needed to let passengers get on and off. The subsequent buses are (often) not able to pass the first bus, so you tend to end up with a full bus followed by a line of empty ones.
  • The day you forget your umbrella, it pours with rain. The rain is worse if you are coming out of the Hair Salon or dressed up for a party.
  • When graphing, the graph paper is always one square too small for the perfect scale.
  • When caught in a traffic jam, the lane that you are in will always be the slowest to move.
  • When you measure twice and cut once either the measurement was wrong, the blade will break or you'll cut at the wrong mark.
  • Nothing is as easy as it looks. Everything takes longer than you think, or twice as long as it should. Except that which appears easy, which takes three times as long.
  • Anything that can go wrong will go wrong, and at the worst possible time.
  • 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.
  • If something simply cannot go wrong, it will anyway.
  • If you perceive that there are four possible ways in which a procedure can go wrong, and circumvent these, then a fifth way, unprepared for, will promptly develop.
  • Left to themselves, things tend to go from bad to worse.
  • Nature always sides with the hidden flaw.
  • Every solution breeds new problems.
  • All small objects of value will disappear when set down.
  • Magellan's Allegory: If you stop and ask someone for directions, and they tell you "You can't miss it", then be assured that you will.
  • If you make it idiot-proof, someone will make a better idiot.
  • When you put your trousers on without looking, they will always be on backwards.
  • A series of events will go wrong in the most negative sequence.
  • Airline Travel Variation: The time you have to catch a flight is inversely proportional to the distance to the gate.
  • 50/50/90: If there is a 50/50 chance to get it right, there is a 90% chance that you will get it wrong.
  • The day you forget to bring your calculator to Math or Science class, there will be a quiz or test that requires one.
  • Transport will always be late, unless you are late yourself, in which case it will be on time.
So there you are you have been warned!