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


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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