Tau vs Pi: Fixing a 250-year-old Mistake

Rewley House, 1 Wellington Square, Oxford
Saturday, June 1, 2013 - 09:45 to 17:00

Leonhard Euler popularised the symbol pi in the mid-eighteenth century,
establishing ratio of circumference to diameter as the circle constant
of choice. But a circle is defined by centre and radius, so which ratio
is more natural: circumference to diameter or circumference to radius?
This question, pi or tau, is more than notational: it has conceptual,
aesthetic and pedagogic implications. The last ten years has seen
increasing interest in the question of whether it might be both sensible
and possible to depose pi in favour of tau. A 'Tau Manifesto' has been
written, setting a good-humoured but persuasive agenda. But now a 'Pi
Manifesto' has been written too: Euler's followers are not to be
thwarted easily.

We shall look at the history of circle constants from Greek to modern
times; weigh the merits of the Tau and Pi Manifestos; consider the
implications of the former for 'Pi mythology' (the huge body of
Pi-paraphernalia embedded in our culture); and discuss whether it is
actually feasible to bring about such a radical change in notation. This
course will certainly leave you with an informed opinion on a topical
if fringe mathematical issue; you may even find you want to do something
about it!

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