Out or Not Out

This article is going to be a look at cricket umpiring and trying to apply some human physiology and some simple physics to the decisions that the Test umpires have to make. I shall use a decision from the test where Broad was, now famously, given not out caught behind.

Let’s start with some physiology. What actually happened when the umpire saw the ball strike Broad? How did the umpire see light from Broad and the ball? A bit of physics here but don’t worry I will keep it simple so even if you could not get into University here in Melbourne and had to go to Monash , or somewhere worse, it should make sense. If you went on to further education and did no physics, you should be ashamed of yourself. I forget which great physicist said of education that there is physics, and the rest is stamp collecting.

Light can be understood as consisting of a series of waves emitted from Broad and the ball. These waves are called electromagnetic radiation. The different colours of light are really the same thing except they vary in their size or wave length. The red light from the ball does not have the same wave length as the white light from Broad’s white sleeve. The light from Broad’s gloves and Haddins gloves will not arrive at the umpires eye at the same time but this time difference is not detectable by human beings. This is the crux of the issue that I am about to raise.

The light hits the umpire’s eye and travels through the eye until it hits a series of detectors that respond to the light hitting them by releasing a chemical. Now there are different detectors that work in different ways but for my purpose today I do not want to get bogged down in details. They are not important to my argument. The released chemical oozes about until it hits an electric cable, called a nerve cell and causes a “short” to move along the cell wall or more correctly causes a wave of depolarization to travel. Oops, I promised to keep it simple. These electric signals now travel into the brain. We have now changed light from the outside world into neurological pulses but the transformation has not happened instantaneously.

Now it gets interesting. The brain does an enormous amount of processing of the information that it receives from the eye and I have a very simple experiment for you to do which will illustrate what needs to happen. Get a video recorder; hopefully your phone has one. Stand up and jump up and down a few times. Now pick up the recorder, aim it at something and turn it on, but jump up and down with it in your hands. Now play back what you have recorded. The vision from the h video recorder will be jumping around all over the place but your personal vision does not. Our vision is pretty cool. The brain does some really wonderful processing BUT the brain and the visual system does have some limits that will stop umpires ever being able to give certain cricket decisions.

The crucial point of the Broad decision is a concept of “visual summation” or in simple terms what is the smallest time period, between two events, that can we see two things occurring separately, rather than them blurring together. Think about movie film that consists of still images that flash up on a screen so fast that we see a continuous motion rather than a series of still images. Eighteen frames per second are the slowest they can use or one frame every 0 .05 seconds which gives us a figure we can now apply to the Cook decision. The physiology of our vision is actually a bit more complicated than this but this simplification is a good place to start. Could the umpire realistically have given this decision?

Let’s assume the ball was going at ninety kls per hour and that two player’s gloves were ten centimeters from each other. The ball is travelling at 25 meters per second and will travel the five centimeters in .004 seconds. This is a dozen times quicker than it is possible for our physiology to detect. I hope you also now realize that there are enormous numbers of umpiring decisions that are also impossible for a human umpire to detect the salient information; a bump ball for example. Did he hit it in the air? It occurs so quickly it is not detectable. Having studied physiology at University(not at Monash, La Trobe or somewhere un-mentionable) I have been amused by fellow umpires claiming that they could be sure of certain decisions, when to be sure, means they are not a biological life form.

To go back to the Broad decision, there was no way that the umpire can detect what the ball hit. I have no truck with umpires who say that they can tell by the sound. This is simply conformation bias. The same argument applies to the detecting of sound but don’t bother to do the jumping up and down experiment.

This brings up another important point. The ICC must not rush any decisions on the referral system. The present system has reduced the umpiring errors by two thirds and if the players can get a bit better at deciding what to refer, the system will be even better. Remember at this time the players get about one in five right bur I am sure this will improve as they become used to the system, except for Australia’s Harris who refers everything. When the MCC ran cricket they would use the English county season as an experimental system. They had 16 counties and the two universities so they could introduce a rule and in 4 months have at least 200 first class games played with it. The counties would then be asked to give their opinions on the rule.

A good example was when they decided to use the bowler’s front foot for the no ball law. The original trial made the bowler land his entire foot behind the front line. Since the umpire stands about four yards behind where the foot lands he could not see if the whole foot was behind the line. Everyone realized nearly immediately that you have to devise a Law that uses the bit of the foot that the umpire can see i.e. the heel.

I’ve sort of realized here that today I been talking about mistakes and errors and the whole tone of this article is a bit negative so I will leave with a thought. Nearly all cricket is played without umpires. The players do it themselves. Try playing a game of soccer without neutral umpires. Last about five minutes I reckon. It’s bloody marvelous that cricket is played the way it is.


  1. Speaking as an avid stamp collector I have my doubts about the technical value of DRS. Umpires make mistakes for some of the reasons you describe. DRS makes nearly as many numerically, but different ones because it has different weaknesses.
    Gideon Haigh’s blogsite is down but I am sure I read pretty compelling stats from him that DRS cost $60,000 a day (test?) and only improved the accuracy of umpiring decisions by around 3%. Analysis said umpires unaided got it right 89% and DRS 92%.
    So even on a generous interpretation I wonder how you got a two thirds reduction in umpiring errors from using DRS.
    Use DRS for line calls like run outs and stumpings. Get rid of it for everything else. It just substitutes mechanical failings for human ones.
    Heisenberg’s Uncertainty Principle? Or should I go back to my stamps.
    Thoroughly agree with your final para. Thanks for livening up the debate.

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