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Robert H OlleyRSS Feed of this column.

Until recently, I worked in the Polymer Physics Group of the Physics Department at the University of Reading.

I would describe myself as a Polymer Morphologist. I am not an astronaut,

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Pi Or 2 Pi – That Is The Question

Pi Or 2 Pi – That Is The Question

Jun 28 2008 | comment(s)

In February this year there appeared in Physics World an article entitled Constant Failure by Robert P Crease of Stony Brook University, in which he showed in how many formulae of physics and mathematics 2π turns up, rather than π. This article struck a chord with me, since even after many years I remember the feeling of “cognitive dissonance” when being taught that the formula was 2πR rather than πD.

I felt it a bit much, though, suggesting that Archimedes might have been mistaken in choosing to calculate the ratio of circumference to diameter rather than to radius. In those days, the fundamental dichotomy seems to have been between the geometers who thought of circumference, diameter and their ratio, and the astronomers who used the radius in their calculation of chord tables.

Hipparchus used a radius of 3438 which is the nearest integer to the number of minutes in 1 radian, but Ptolemy preferred 3600 as this is easier to calculate within the sexagesimal system. The work of these astronomers, further developed by Hindu and Arabic mathematicians, gives us our trigonometry of today.