No, really, pi is wrong: The Tau Manifesto
I am a graduate student, first-year, so I have a lot of problem sets to work on. I've been thinking about tau every so often since the last time this was posted here, and so every time I work a problem, I think to myself: would this be clearer if I used tau? And the answer is usually "no". Sometimes 2 is next to pi because of the natural reason appealed to in the tauifesto, and other times it's there for some other reason, other times it isn't there at all; there's usually a huge constant factor out front anyway, and often a single equation goes across the whole sheet of paper, so even making it one character shorter doesn't accomplish much.<p>Not that I haven't learned notation that <i>really</i> helps. Gaussian units and Einstein notation are a <i>godsend</i>. If you could standardize introductory physics courses using these, I think it could help significantly, especially when people struggle to work out the curl of a cross product or some-such strenuous vector calculation. All hail the Levi-Civita tensor! But we haven't even been able to agree on this.<p>Furthermore, as a test grader of nearly-a-year, the work done by undergraduates is nigh-inscrutable in the maximally acceptable way <i>already</i>, and so the tau "rebellion" promoted here would just make my job harder. It's not too much of an issue: only the technically-inclined, who already do pretty clear work, are likely to use it; still, telling people "just start doing your work like <i>this</i>, let <i>them</i> figure it out!" means that I have to know if that scribble is a tau or a T or what-have-you, two hundred times. Pi is a very recognizable character.<p>Plus, tau is the letter I reach for whenever I need to introduce an adjusted time of some sort, such as proper time; it's also the natural temperature in stat mech (though thermodynamic beta is itself more natural and usually better), it's torque, it's a common time constant, &c. People generally avoid pi as a character which does <i>not</i> represent 3.14159, though it is the prime counting function and an adjusted momentum, in which case it usually has a half-arrow, so you can tell what it's doing. We don't avoid tau at all; it's everywhere.<p>So the tau-switch, as notational improvements go -- and math has had many over the years -- seems like a relatively large-pain, small-gain deal. Many things must change, since pi is all over the place, but few are greatly improved. So I don't see much reason to use tau in my work, or for my students to use it in theirs. If it works for you, though, good!