Replace Pi with Tau?

I must admit I was unaware of this controversy, but it makes some sense to stop using the constant pi, and to use a new term, tau, instead. Tau is defined as 2 times pi, which would be 6.283.  This is explained in a fun article in a recent Scientific American story:  
Tau relates the properties of a circle to the circle's diameter, whereas pi is related to the radius (r). So the equation 2*pi*r, which gives the circumference of the circle based on a measure of the radius, is replaced with the simpler version, tau*diameter, where the diameter is simply twice the radius. I always wondered, when bored in class, why mathematicians used the radius in calculations instead of the diameter. The article cites some of the history of pi, and why that constant was chosen.

Mathematically, it makes no difference. The argument for changing everything to tau is based on the observation that using the radius always involves a "2" multiplier, which sometimes makes the resulting expression somewhat less obvious. Examples used in this Scientific American article show how the use of pi always adds an additional "2" in an expression, sometimes degrading the apparent simplicity/beauty of fundamental equations in the process.

Interesting topic, especially if you enjoy math.


I disagree with this assertion and wrote quite a lengthy response to it several years ago.  The constant Pi is used in many other applications, and shows up in mathematics in many places....not just in circles.  For example the area under the curve, f(x) = 1/(1+x^2) from - infinity to + infinity is PI.  A simpler example is the area of a circle: PI*r^2.  There are also similar arguments in trigonometry (counter to the ones for Tau) where the introduction of Tau would just introduce a fraction.
So I posit, what's less aesthetically appealing, the whole number "2," or the fraction "1/2."  I'm sure most people would agree that the fraction is more annoying!!
However, it is a moot point, and a great segue into learning about the history of pi.

One last point.....from a historical perspective, PI has a very specific meaning.  It is the ration of the circumference of a circle to its diameter: PI = C/D.  I don't think changing this definition to TAU/2 =C/D is easier or more aesthetic.

So, I'm sticking with tastes better anyway!
Thanks, Michael.  Good points.  Please consider a "letter to the editor" to Scientific American.  Your short summary, along with the earlier reference, would provide a useful correction for those of us who love pi.  While you're at it, could you also put in a good word for Pluto?
Haha, sorry, I'm all for the demotion of Pluto from planet status.  Pluto was lonely as a planet.  But now, he has rejoined his brethren of similar Kuiper Belt objects.  He has returned home to his real family!
Yes, I agree that Pluto made the original list in a fit of excitement, including naming rights and grant possibilities.  So removing it as a planet was correct, although curiously painful.


Robert S.

Dr Bob Loves Science (especially chemistry and physics)

200+ hours
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