Who says Pi is Wrong?
In the early 21st century, Bob Palais (a mathematician) and Michael Hartl (a physicist) declared that Pi, the traditional circle constant, was wrong.  Their argument is that Pi, defined as the ratio of a circle's circumference to its diameter, is not the most effective or clear way to describe the geometry of a circle.

Palais and Hartl contend that the ratio of a circle's circumference to its radius is a more useful constant.  They chose to name this new constant Tau.  Arithmetically, Tau = 2*Pi.

They argued that Tau produces cleaner mathematical equations throughout physics, mathematics, and statistics and, further, that it makes it easier to teach trigonometry and analytic geometry to new learners.
Instruction: Who says Pi is Wrong?
Context: 
Response: In the early 21st century, Bob Palais (a mathematician) and Michael Hartl (a physicist) declared that Pi, the traditional circle constant, was wrong.  Their argument is that Pi, defined as the ratio of a circle's circumference to its diameter, is not the most effective or clear way to describe the geometry of a circle.

Palais and Hartl contend that the ratio of a circle's circumference to its radius is a more useful constant.  They chose to name this new constant Tau.  Arithmetically, Tau = 2*Pi.

They argued that Tau produces cleaner mathematical equations throughout physics, mathematics, and statistics and, further, that it makes it easier to teach trigonometry and analytic geometry to new learners.