I re-discovered my slide rule a while back, the one I used in school maths lessons, way back when. I didn’t know just how utterly classic such things were, even then.
These things mostly worked because of a quirk of mathematics – the logarithm, which means you can add logs, as a linear measure, to multiply. And there’s more. In the photo, I’ve set my slip-stick to do the pi times table – and believe me, it’ll calculate that to about two decimal places (which is OK for a quick estimate) faster than you can punch the same thing into a calculator. All you have to do is slide the centre piece to the right point and look along the ruler. Cool.
Time was when no self-respecting space adventurer set off without one of these. They were a staple in Robert Heinlein’s sci-fi, among others. With them you could not only defeat the squidgy aliens who were trying to make off with all Earth’s water – you could go on to conquer the entire universe.
And, just to nail how fast the world changes, NASA actually did conquer the Moon with slide rules. Apollo-era engineers carried them the same way we carry phones.
My slide rule’s linear, but they were also available as circular calculators – disks – often optimised for other functions such as electrical calculation. My father had one.
I have to admit that I’m using computers to do the maths for a hard sci-fi story I’m writing just now for an upcoming anthology. But still, the slide rule’s there as a standby. And the idea of it – well, I find that pretty inspiring. Do you?
Copyright © Matthew Wright 2015