The joy of analogue

I was half-listening to the BBC radio show The Museum of Curiosity over the weekend when something caught my ear. One of the guests, popular maths writer Alex Bellos, was talking about a mechanical pocket calculator from the 1940s. One of the other guests, Jimmy Carr commented that it went out of fashion when 'everything went digital' (or words to that effect). I was expecting Bellos to jump on him from a great height, but instead he said that, yes, soon after computers took over.

Not only is Jimmy Carr's statement inherently wrong, but the whole discussion is an example of (probably unintentional) historical revisionism, missing out on a fascinating stage in the development of computing technology.

My dad's circular slide rule

Carr's comment was so wrong because a mechanical calculator is digital. We tend to equate digital and electronic - but forget why we do this. It's because (digital) mechanical calculators were mostly ousted in science and engineering by analogue calculators (also mechanical) which in turn were replaced by (digital) electronic calculators. To take the story straight from mechanical to electronic is poor history to say the least.

The analogue revolution that Carr and Bellos ignored is the slide rule, making fast complex calculations easy. We tend to look down on analogue solutions because they are approximate - though they can be made as accurate as you like - but all we're really saying there is that they're natural. Digital may be the reality at the quantum level, but the world we experience (including many aspects of the way our brains work) is analogue.

I used to have a beautiful circular slide rule that was my father's. The advantage of the circular version is that in a compact device, less than 10 centimetres across, you had the equivalent of a straight slide rule much too long to use. And it was lovely to twiddle and do those calculations. I confess I sold it, because I'm not much of a collector, and it is certainly obsolete, but it doesn't stop it being a wonderful device.

I'm all in favour of using humorous programmes to get across science and history - but do make sure you get your facts right, guys.