For those of you who aren't in Math Club, be informed -- 3/14 marks the unofficial "Pi Day".  That's right, the legendary constant (π=3.14159...) has it's own honorary holiday, though most don't remember to celebrate it -- well other than the math obsessed a certain viral YouTube musician [video].

But on Pi day, some people are trying to introduce a new constant "Tau".  Tau (τ) is often used by engineers to represent the inverse of time, but Michael Hartl [profile], Ph.D thinks of it as something quite different -- two pi.

Dr. Hartl attended a who's who of prestigious universities, studying undergraduate physics at Harvard University, participating in graduate chaos theory studies at the University of Maryland, and finally obtaining his Ph.D at the California Institute of Technology.

But rather than jump back into the world of academia alone, Dr. Hartl split his time with various entrepreneurial ventures.  Today he continues to split his time between his two loves -- education and business.

But perhaps no business venture of the educator has been as outlandish as his treatise The Tau Manifesto.  Inspired by Bob Palais' [profile] essay Pie is wrong! [PDF] Dr. Hartl dreamed up the atypical use of the t-like Roman numeral.

He argues that we should be celebrating 6/28 as Tau Day, and 3/14 as "Half-Tau Day", not "Pi Day".  He writes, "τ is a natural choice of notation because it references the typographical appearance of π, has etymological ties to one "turn", and minimizes conflicts with present usage. Indeed, based on these arguments (put forward by me and by Peter Harremoës), Bob Palais himself has thrown his support behind τ."

As supporting evidence Dr. Hartl points to many formulas, like the Gaussian distribution, Fourier Transform, and, of course, the circumference formula -- all of which contain 2π.  He says that τ is a natural choice because pictographically it looks like a π with a leg missing.

Constants are constants, but given the typical uses of τ, Hartl's wild attack on Pi and boosting of τ a π-like constant may seem bizarre, almost disturbing.  He does raise some valid points.  But is τ the best number?  What about good old "Omicron"?  After all, it's seldom used -- and it's shaped like a circle!  How perfect. [For the record, I, the writer, claim authorship of this humble suggestion.]

But even if we were to embrace τ, or ο perhaps, engineers and mathematicians will likely find π as useful or more so in many cases.  After all, it's a lot easier to write Area_circle= πr² than Area_circle = τr²/2.  And that, one could suppose, is cause enough for some Pi Day celebration even if the beloved constant is developing a bit of a rival of late.