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VAR: an Exercise in Spurious Accuracy

Every few weeks or so, those of us who like to follow the English Premier League are drawn into some new argument about a VAR decision. Was it a penalty? Was it offside? Should the goal have been given?

And those of us whose memories go back more than a few years will know that this is just a modern twist on arguments that have always surrounded football. There have always been dubious calls and fine points of detail over which we can argue. In the past, of course, the consensus was that we should use TV images (or VAR) to right obvious injustices, whereas now there seems to be a growing cohort who think the game is being ruined by the use of such images, and we should go back to how things were done in the past.

Somehow I feel we might be stuck in an endless cycle.

I suppose I should by now have reached a point in life where I let these arguments pass me by, maintaining a lofty detachment from it all. But I haven't quite got there yet, and I suspect I never will. Nor am I sure I want to. Are wisdom and maturity really central to the enjoyment of football? I have, however, generally learned to accept that in any situation where a judgement call must be made, opinions will differ - with or without TV images - and we just have to accept the call that has been made and move on.

But there is one aspect of the use of VAR that I find very irritating - and it links (somewhat tenuously) to LC Physics...

The image above comes from the Man U - Coventry game at the weekend. Coventry (who were very much the outsiders) had fought back from 3-0 down against the (once) mighty Man U team to draw level, and in the dying seconds of extra time seemed to score what was surely destined to be a famous winning goal. But 90 seconds later the goal was disallowed due to offside, based on the image above.

Arguments about this have centred on how trivial the offence was, with the Coventry player's left foot ahead of the Manchester player's by no more than the length of a toe.

But I think that misses the point. We can't ask VAR to change the rules of the game. If a player is offside by even a centimetre then he/she is offside, and surely we should be delighted that such a precise measurement is now possible. But that begs the question: is such precise measurement actually possible?

The offside rule states that the attacking player must not be closer to the goal than the 2nd last defender when the ball is played - and it's the second part of that phrase that seems to be forgotten in these arguments. When controversy arises, we are always shown freeze-frames of the attacking player with lines drawn on the screen to help us compare their position to the defenders. But those images mean nothing if they're not taken when the ball is being played.

So we are being asked to believe that the photo shown is the exact moment the ball leaves the foot of the player to the left. Is that really precise? I certainly can't tell. And if that moment can't be pinpointed with real precision, then the arguments about the position of the attacker's and defender's feet become irrelevant.

The VAR system depends on images that are filmed at 50 frames/second, and I'm told that officials involved are trained to focus on 3 frames in trying to determine the moment the ball is kicked, and then to use the best of those images - just as the ball has left the player's foot.

But a ball travelling at 10 m/s (and they can be going much faster) would travel 20 cm between two of those frames. That's not a small distance. And it means that all that obsessing about the exact position of a players feet on the red and blue lines is more or less meaningless - and that calls made on the basis of a few centimetres are pretty much random.

Or - to tie this back in with physics - it's an exercise in spurious accuracy: a pretense to accuracy that is either meaningless or unattainable. A little like our GPS systems telling us where we are to a millimetre, when in fact it is likely to be inaccurate by a number of metres. Or a thermometer being read to a fraction of a degree, when it is in fact likely to be wrong by a number of degrees.

in Leaving Cert, we tend to simplify this issue with the use of the 2-decimal-places rule of thumb, but Issac Physics has a great exercise to teach students the precise rules regarding significant figures - all designed to avoid spurious accuracy.

Perhaps they should share that exercise with the VAR officials in Stockley Park!

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