The rubber band “slide rule” does not slip, but rotates

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Here, we especially appreciate the slide rules. We even have our own collections, some of which are cylindrical and circular. Corn [Mathologer] discusses a recent Reddit post that explains a circular slide rule-like device using a wheel and a stretchy rubber band. While it’s probably difficult to build the actual device using a rubber band, it can do wonders for your understanding of the logarithms that still appear in our lives when, for example, calculating decibels. [Dimitri] simulated the elastic for you in the software.

The idea is that a perfect rubber band has numbers from 0 to 10 evenly marked on it. As you spin a wheel attached to the 10 mark, the rubber band stretches more and more. So the 10 and 9 have relatively little space between them, but the 1 and 2 are much farther apart. The circumference of the wheel is defined so that the 1 exactly covers the 10. This means that each point on the wheel can represent any number that differs only by one decimal point. So you could have 3 means 0.03, 300 or – of course – 3. Of course, you don’t need to build the wheel with a rubber band – you can just mark the wheel like a regular circular slide rule.

If you’ve never really understood why a slide rule works or you don’t know how to make one, you’ll find the explanation in the video very intuitive and illuminating. You should have a rough idea of ​​the order of magnitude of the response you expect, but it’s not that hard with practice.

Of course, if you flatten the circle, you get a normal slide rule. You can see some of my collection – but oddly none of my flyers – in an older post from 2015. If you want to make your own, we suggest you leave the rubber band in the drawer and check [Dylan’s] to work.

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