Pi is not the true circle constant

Here is a compelling, interesting, coherent argument for a new circle constant :

http://tauday.com/

>>4
More or less.  I personally have no control over this sort of thing and would see no reason to object to it (hand in hand with having no reason to promote it).

One argument that I was demonstrated early was that pi is the curve distance of a hemisphere with 1 radius and 2 diameter.  To walk around the hemisphere from 0 (start) to 180 (end) degrees, you walk pi units; to walk in a straight line between those same points ("start" to "end") you walk 2 units.  Can this be rephrased without implying a "half-tau?"