# Why Murphy was probably right

So, there’s this law by Murphy that most of you must be aware of.

If anything can go wrong, it will.

Now, the origin of Murphy’s law is quite well explained here.

And so goes the original Murphy’s law:

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.

Now the situation that gave rise to this quote is something like this.

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. (Source)

I’d think the odds of failure were quite high. How?

The person in charge of installing the accelerometers can be called Mike. Why? It’s a standard enough name. Now, Mike probably wasn’t a smart enough guy.

1. He did not know which side of the sensor went where and randomly installed all accelerometers, using no common sense, failing to set the right combinations = $0.5 \times (1 - 0.5^{16})$ [FAIL]
2. He did not know which side went where and randomly installed all accelerometers, using no common sense  but luckily fixing the right combinations = $0.5 \times (0.5^{16})$ [SUCCESS]
3. He had the sides interchanged and installed all in the same way. Well, at least he had some common sense to install all in the same way = $0.5 \times 0.5$ [FAIL]
4. Mike was smart. He got the sides right and had the sense to install all in the right way = $0.5 \times 0.5$ [SUCCESS]

Let’s give Mike the benefit of doubt. Maybe he was smart. Let’s assign that a probability of $0.5$. Probability Mike was dumb is $0.5$.

The probability of failure is then approximately $0.75$. If you think of any ideal situation too, the probability of the chain of events leading to a success, when multiplied, is quite low.

Let’s look at it this way. The event: Me getting a sound night’s sleep. Shouldn’t be hard right?

Why it doesn’t work: I have a roommate who keeps talking loudly on the phone till wee hours. Why would I have a roommate? I am a research assistant, we don’t get paid well enough for me to be able to afford a better room. Why am I a research assistant? I want to do a PhD. Why do I want to do a PhD? You get the drift.

Turns out, I was almost destined to have a painful right ear, being subjected to continuous loud mindless rants in the middle of the night. The consequences of a lot of our actions aren’t really predictable until events transpire in due course of time. But when they do happen, it’s not that hard to chart out the trajectory of what might have caused them. And so, if anything wrong can happen, perhaps your brain is able to trace that trajectory in advance to forecast what will go wrong.

Here’s the catch though. When things are expected to go wrong and they don’t, we are so happy with the outcome, we barely recognize it as a failure of the law. So Murphy was a genius, in framing a law whose exceptions would go easily unnoticed. Whoever thought that something so iconic would come out of so much pessimism?

Then again, as Phil Dunphy from Modern Family would say…