Math wars: Debate sparks anti-pi day

A controversial debate in the math world has led to celebrations today
by opponents of
the mathematical constant pi.

Tau Day, in honour of the constant some say should
replace pi, is
being celebrated by
those who agree with US mathematicians Bob Palais and Michael Hartl.
The
two argue that
tau, twice as large as pi at approximately 6.28, makes many
calculations easier to
perform.

In The Tau Manifesto, Hartl says that although pi is well-
defined,
it's “a confusing and unnatural choice for the circle constant…Pi is
half of something. It's
the something that is fundamental.”

Whereas pi defines a circle as the ratio between circumference and
diameter, tau defines a
circle in terms of its circumference and radius.

Hartl and Palais note that tau shows up in several major mathematical
equations – an
observation, they say, that isn't simply a coincidence, but rather
justifies adopting a new constant.

Supporters have taken the concept one step further by declaring June
28 Tau Day,
meant to rival the more familiar tradition of Pi Day, held on March 14
each year.

Patrick Speissegger, associate professor at McMaster and Canada
Research Chair in
Model Theory, doesn't buy into the idea.

“It's not a question of right or wrong, but a matter of opinion,” says
Speissegger.
“Philosophically speaking, changing the constant from pi to tau makes
no difference.”

Except perhaps on the issue of practicality.

“It would be more difficult for people who are learning math because
they'd
have to be able to
know and use both constants – pi has been used in mathematical
literature for the past
2,000 years,” he says.

Chris Miller, a professor in the department of mathematics at The Ohio
State University who
was at McMaster on Tau Day, agrees with Speissegger.

“It depends on which you believe is more important: the circumference
of a circle or the
area of a circle,” says Miller. “I don't see how one is more important
than the other, and,
in any case, you'd have to convince me that all the trouble is worth
it.”

Despite differences of opinion, Tau Day is well underway, with some
supporters
suggesting that Pi Day be renamed “Half-Tau Day.”