# Measurement beats guesswork

By Marcus Wilson 21/01/2011

OK – so this story is a touch light on the physics front, but it does demonstrate the power of actually taking the time to measure something, instead of assuming the obvious.

My wife has kindly agreed to help a friend (who has limited mobility) travel from Cambridge to Hamilton for a medical appointment. This of course means getting the friend into a car, which from all accounts isn’t an easy job.   One naturally assumes that the process will be aided if the car door is big, the seat is wide, and if it isn’t too high or too low off the ground.

We have two cars, both rather long in the tooth now, and both from the same manufacturer. One’s a station wagon, with lots of space and a towbar – it’s certainly useful to have but it does guzzle a lot of fuel, and the other’s smaller, more comfortable, and is pretty economical to run. Unsurprisingly, the station wagon spends most days locked in the garage going no-where while we use the other nearly every day.

Now, it was a no-brain decision that I should take the smaller car to work today leaving my wife the large car in which to take our friend to the hospital.  Though, for some reason, last night I felt compelled actually to measure the door sizes, space in the front seat, height from the ground to the seat, etc, of both cars – just to confirm what was patently obvious.

On measuring, I had a bit of a shock. They are actually the same. I reckon I could take the passenger door off one car and fit it snugly on the other.  Perhaps I shouldn’t have been surprised – two cars of similar ages from the same manufacturer, but I just thought that the larger car had to be the one easier to get in and out of. I’ve even ‘felt’ that there is more space in the front seat of the larger car, but the tape measure tells me otherwise. My intuition has been deluding me.

Unlike your intuition, a tape measure, or other scientific measurement, doesn’t often lie to you. A story to recount to my students next time they can’t be bothered to measure something that’s ‘obvious’ in the lab.