Reinventing and Understanding the Circular Slide Rule with a Rubber Band

Here is Fourmilab’s “Slide Rule” page, exploring the genius of and solving real-world problems with this amazing add-a-log computer. You can follow along with this virtual slide rule that runs in your browser. The Cold War even gave us the Strangelove Slide Rule, a circular pocket computer for estimating the effects of nuclear weapon detonations.


Logarithms are an amazing invention. Or discovery. Irrespective of that, what would have to had been true for ancient greeks to invent (or discover) logarithms?

Ancient Babylonians had something like the logarithm in place. Fascinating to learn that in modern times it has been used in digital arithmetic integer multiplication.

The answer is math… now, what was the question?